Thomas Jaramillo
Professor of Chemical Engineering, of Energy Science Engineering, and of Photon Science
Bio
Recent years have seen unprecedented motivation for the emergence of new energy technologies. Global dependence on fossil fuels, however, will persist until alternate technologies can compete economically. We must develop means to produce energy (or energy carriers) from renewable sources and then convert them to work as efficiently and cleanly as possible. Catalysis is energy conversion, and the Jaramillo laboratory focuses on fundamental catalytic processes occurring on solid-state surfaces in both the production and consumption of energy. Chemical-to-electrical and electrical-to-chemical energy conversion are at the core of the research. Nanoparticles, metals, alloys, sulfides, nitrides, carbides, phosphides, oxides, and biomimetic organo-metallic complexes comprise the toolkit of materials that can help change the energy landscape. Tailoring catalyst surfaces to fit the chemistry is our primary challenge.
Academic Appointments
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Professor, Chemical Engineering
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Professor, Energy Science & Engineering
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Professor, Photon Science Directorate
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Affiliate, Precourt Institute for Energy
Administrative Appointments
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Director, SUNCAT Center for Interface Science and Catalysis (2018 - Present)
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Deputy Director, SUNCAT Center for Interface Science and Catalysis (2014 - 2018)
Professional Education
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PhD, University of California, Santa Barbara (2004)
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MS, University of California, Santa Barbara, Chemical Engineering (2000)
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BS, Stanford, Chemical Engineering (1998)
2024-25 Courses
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Independent Studies (4)
- Graduate Research in Chemical Engineering
CHEMENG 600 (Aut, Win, Spr) - Ph.D. Research
MATSCI 300 (Aut, Win, Spr) - Undergraduate Honors Research in Chemical Engineering
CHEMENG 190H (Aut, Win, Spr) - Undergraduate Research in Chemical Engineering
CHEMENG 190 (Aut, Win, Spr)
- Graduate Research in Chemical Engineering
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Prior Year Courses
2023-24 Courses
- Electrochemical Energy Conversion
CHEMENG 432, ENERGY 432 (Aut) - Fundamentals and Applications of Spectroscopy
CHEMENG 345 (Spr)
2022-23 Courses
- Chemical Process Modeling, Dynamics, and Control
CHEMENG 100 (Win) - Fundamentals and Applications of Spectroscopy
CHEMENG 345 (Spr) - Special Topics in Energy and Catalysis
CHEMENG 516 (Aut)
2021-22 Courses
- Chemical Process Modeling, Dynamics, and Control
CHEMENG 100 (Aut) - Special Topics in Energy and Catalysis
CHEMENG 516 (Aut, Win, Spr, Sum)
- Electrochemical Energy Conversion
Stanford Advisees
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Doctoral Dissertation Reader (AC)
Evan Carlson, Timothy Goh, Jinyu Guo, Maggy Harake, Dean Miller -
Postdoctoral Faculty Sponsor
Changzhi Ai, Hussein Osama Mohamed Badr Badr, Filippo Balzaretti, Pooja Basera, Suman Bhasker Ranganath, Neha Bothra, Junjie Chen, Ara Cho, Lakshay Dheer, Ezgi Erdem, Roman Fanta, Anshuman Goswami, Ryan Hannagan, Hyeonjung Jung, Konstantin Lebedev, Sang-Won Lee, Zan Lian, Ruchika Mahajan, Shyama Mandal, Hori Pada Sarker, Johanna Schroeder, Dongjae Shin, Michael Tang, Judith Zander, Zisheng Zhang, Peng Zhu -
Doctoral Dissertation Advisor (AC)
Yamile Cornejo Carrillo, Colin Crago, Tristan Gilbert, Gaurav Kamat, Daniela Marin, Jesse Matthews, Isa Rios Amador, Milenia Rojas Mendoza, Rachel Spurlock, Alfred Vargas, Wrayzene Willoughby, Katherine Yan, Kyra Yap, Sihe Zhang -
Doctoral Dissertation Co-Advisor (AC)
Ashton Aleman -
Postdoctoral Research Mentor
Junjie Chen, Sang-Won Lee, Johanna Schroeder
All Publications
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Author Correction: Alkali cation-induced cathodic corrosion in Cu electrocatalysts.
Nature communications
2024; 15 (1): 6092
View details for DOI 10.1038/s41467-024-50241-z
View details for PubMedID 39030201
View details for PubMedCentralID PMC11259566
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Understanding the Effects of Anode Catalyst Conductivity and Loading on Catalyst Layer Utilization and Performance for Anion Exchange Membrane Water Electrolysis.
ACS catalysis
2024; 14 (14): 10806-10819
Abstract
Anion exchange membrane water electrolysis (AEMWE) is a promising technology to produce hydrogen from low-cost, renewable power sources. Recently, the efficiency and durability of AEMWE have improved significantly due to advances in the anion exchange polymers and catalysts. To achieve performances and lifetimes competitive with proton exchange membrane or liquid alkaline electrolyzers, however, improvements in the integration of materials into the membrane electrode assembly (MEA) are needed. In particular, the integration of the oxygen evolution reaction (OER) catalyst, ionomer, and transport layer in the anode catalyst layer has significant impacts on catalyst utilization and voltage losses due to the transport of gases, hydroxide ions, and electrons within the anode. This study investigates the effects of the properties of the OER catalyst and the catalyst layer morphology on performance. Using cross-sectional electron microscopy and in-plane conductivity measurements for four PGM-free catalysts, we determine the catalyst layer thickness, uniformity, and electronic conductivity and further use a transmission line model to relate these properties to the catalyst layer resistance and utilization. We find that increased loading is beneficial for catalysts with high electronic conductivity and uniform catalyst layers, resulting in up to 55% increase in current density at 2 V due to decreased kinetic and catalyst layer resistance losses, while for catalysts with lower conductivity and/or less uniform catalyst layers, there is minimal impact. This work provides important insights into the role of catalyst layer properties beyond intrinsic catalyst activity in AEMWE performance.
View details for DOI 10.1021/acscatal.4c02932
View details for PubMedID 39050897
View details for PubMedCentralID PMC11264204
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Understanding the Effects of Anode Catalyst Conductivity and Loading on Catalyst Layer Utilization and Performance for Anion Exchange Membrane Water Electrolysis
ACS CATALYSIS
2024
View details for DOI 10.1021/acscatal.4c02932
View details for Web of Science ID 001265524300001
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Alkali cation-induced cathodic corrosion in Cu electrocatalysts.
Nature communications
2024; 15 (1): 5080
Abstract
The reconstruction of Cu catalysts during electrochemical reduction of CO2 is a widely known but poorly understood phenomenon. Herein, we examine the structural evolution of Cu nanocubes under CO2 reduction reaction and its relevant reaction conditions using identical location transmission electron microscopy, cyclic voltammetry, in situ X-ray absorption fine structure spectroscopy and ab initio molecular dynamics simulation. Our results suggest that Cu catalysts reconstruct via a hitherto unexplored yet critical pathway - alkali cation-induced cathodic corrosion, when the electrode potential is more negative than an onset value (e.g., -0.4 VRHE when using 0.1 M KHCO3). Having alkali cations in the electrolyte is critical for such a process. Consequently, Cu catalysts will inevitably undergo surface reconstructions during a typical process of CO2 reduction reaction, resulting in dynamic catalyst morphologies. While having these reconstructions does not necessarily preclude stable electrocatalytic reactions, they will indeed prohibit long-term selectivity and activity enhancement by controlling the morphology of Cu pre-catalysts. Alternatively, by operating Cu catalysts at less negative potentials in the CO electrochemical reduction, we show that Cu nanocubes can provide a much more stable selectivity advantage over spherical Cu nanoparticles.
View details for DOI 10.1038/s41467-024-49492-7
View details for PubMedID 38871724
View details for PubMedCentralID 7810728
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Tuning Two-Dimensional Phthalocyanine Dual Site Metal-Organic Framework Catalysts for the Oxygen Reduction Reaction.
Journal of the American Chemical Society
2024
Abstract
Metal-organic frameworks (MOFs) offer an interesting opportunity for catalysis, particularly for metal-nitrogen-carbon (M-N-C) motifs by providing an organized porous structural pattern and well-defined active sites for the oxygen reduction reaction (ORR), a key need for hydrogen fuel cells and related sustainable energy technologies. In this work, we leverage electrochemical testing with computational models to study the electronic and structural properties in the MOF systems and their relationship to ORR activity and stability based on dual transitional metal centers. The MOFs consist of two M1 metals with amine nodes coordinated to a single M2 metal with a phthalocyanine linker, where M1/M2 = Co, Ni, or Cu. Co-based metal centers, in particular Ni-Co, demonstrate the highest overall activity of all nine tested MOFs. Computationally, we identify the dominance of Co sites, relative higher importance of the M2 site, and the role of layer M1 interactions on the ORR activity. Selectivity measurements indicate that M1 sites of MOFs, particularly Co, exhibit the lowest (<4%), and Ni demonstrates the highest (>46%) two-electron selectivity, in good agreement with computational studies. Direct in situ stability characterization, measuring dissolved metal ions, and calculations, using an alkaline stability metric, confirm that Co is the most stable metal in the MOF, while Cu exhibits notable instability at the M1. Overall, this study reveals how atomistic coupling of electronic and structural properties affects the ORR performance of dual site MOF catalysts and opens new avenues for the tunable design and future development of these systems for practical electrochemical applications.
View details for DOI 10.1021/jacs.4c02229
View details for PubMedID 38709577
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Biogenic Manganese Oxide Synthesized by a Marine Bacterial Multicopper Oxidase MnxG Reveals Oxygen Evolution Activity
ACS CATALYSIS
2024
View details for DOI 10.1021/acscatal.3c06119
View details for Web of Science ID 001242189600001
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<i>Operando</i> investigations of the solid electrolyte interphase in the lithium mediated nitrogen reduction reaction
ENERGY & ENVIRONMENTAL SCIENCE
2024
View details for DOI 10.1039/d3ee04235a
View details for Web of Science ID 001209267000001
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Modeling Planar Electrodes and Zero-Gap Membrane Electrode Assemblies for CO<sub>2</sub> Electrolysis
CHEMELECTROCHEM
2024; 11 (7)
View details for DOI 10.1002/celc.202400226
View details for Web of Science ID 001196770700001
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Bias-free solar NH<sub>3</sub> production by perovskite-based photocathode coupled to valorization of glycerol
NATURE CATALYSIS
2024
View details for DOI 10.1038/s41929-024-01133-4
View details for Web of Science ID 001194940900003
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Interpretable Machine Learning Models for Practical Antimonate Electrocatalyst Performance.
Chemphyschem : a European journal of chemical physics and physical chemistry
2024: e202400010
Abstract
Computationally predicting the performance of catalysts under reaction conditions is a challenging task due to the complexity of catalytic surfaces and their evolution in situ, different reaction paths, and the presence of solid-liquid interfaces in the case of electrochemistry. We demonstrate here how relatively simple machine learning models can be found that enable prediction of experimentally observed onset potentials. Inputs to our model are comprised of data from the oxygen reduction reaction on non-precious transition-metal antimony oxide nanoparticulate catalysts with a combination of experimental conditions and computationally affordable bulk atomic and electronic structural descriptors from density functional theory simulations. From human-interpretable genetic programming models, we identify key experimental descriptors and key supplemental bulk electronic and atomic structural descriptors that govern trends in onset potentials for these oxides and deduce how these descriptors should be tuned to increase onset potentials. We finally validate these machine learning predictions by experimentally confirming that scandium as a dopant in nickel antimony oxide leads to a desired onset potential increase. Macroscopic experimental factors are found to be crucially important descriptors to be considered for models of catalytic performance, highlighting the important role machine learning can play here even in the presence of small datasets.
View details for DOI 10.1002/cphc.202400010
View details for PubMedID 38547332
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Modeling diurnal and annual ethylene generation from solar-driven electrochemical CO<sub>2</sub> reduction devices
ENERGY & ENVIRONMENTAL SCIENCE
2024
View details for DOI 10.1039/d4ee00545g
View details for Web of Science ID 001176280900001
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Modeling Planar Electrodes and Zero-Gap Membrane Electrode Assemblies for CO<sub>2</sub> Electrolysis
CHEMELECTROCHEM
2024
View details for DOI 10.1002/celc.202300566
View details for Web of Science ID 001145445100001
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Controlling Mass Transport in Direct Carbon Dioxide Zero-Gap Electrolyzers via Cell Compression
ACS SUSTAINABLE CHEMISTRY & ENGINEERING
2023; 11 (46): 16661-16668
View details for DOI 10.1021/acssuschemeng.3c05494
View details for Web of Science ID 001108321300001
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High-performance ionomerless cathode anion-exchange membrane fuel cells with ultra-low-loading Ag-Pd alloy electrocatalysts
NATURE ENERGY
2023
View details for DOI 10.1038/s41560-023-01385-7
View details for Web of Science ID 001099214100002
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Protocol for assembling and operating bipolar membrane water electrolyzers.
STAR protocols
2023; 4 (4): 102606
Abstract
Renewable energy-driven bipolar membrane water electrolyzers (BPMWEs) are a promising technology for sustainable production of hydrogen from seawater and other impure water sources. Here, we present a protocol for assembling BPMWEs and operating them in a range of water feedstocks, including ultra-pure deionized water and seawater. We describe steps for membrane electrode assembly preparation, electrolyzer assembly, and electrochemical evaluation. For complete details on the use and execution of this protocol, please refer to Marin et al. (2023).1.
View details for DOI 10.1016/j.xpro.2023.102606
View details for PubMedID 37924520
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Calcium-mediated nitrogen reduction for electrochemical ammonia synthesis.
Nature materials
2023
Abstract
Ammonia (NH3) is a key commodity chemical for the agricultural, textile and pharmaceutical industries, but its production via the Haber-Bosch process is carbon-intensive and centralized. Alternatively, an electrochemical method could enable decentralized, ambient NH3 production that can be paired with renewable energy. The first verified electrochemical method for NH3 synthesis was a process mediated by lithium (Li) in organic electrolytes. So far, however, elements other than Li remain unexplored in this process for potential benefits in efficiency, reaction rates, device design, abundance and stability. In our demonstration of a Li-free system, we found that calcium can mediate the reduction of nitrogen for NH3 synthesis. We verified the calcium-mediated process using a rigorous protocol and achieved an NH3 Faradaic efficiency of 40±2% using calcium tetrakis(hexafluoroisopropyloxy)borate (Ca[B(hfip)4]2) as the electrolyte. Our results offer the possibility of using abundant materials for the electrochemical production of NH3, a critical chemical precursor and promising energy vector.
View details for DOI 10.1038/s41563-023-01702-1
View details for PubMedID 37884670
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Quantifying Influence of the Solid-Electrolyte Interphase in Ammonia Electrosynthesis
ACS ENERGY LETTERS
2023
View details for DOI 10.1021/acsenergylett.3c01534
View details for Web of Science ID 001062617200001
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Development of a versatile electrochemical cell for in situ grazing-incidence X-ray diffraction during non-aqueous electrochemical nitrogen reduction.
Journal of synchrotron radiation
2023
Abstract
In situ techniques are essential to understanding the behavior of electrocatalysts under operating conditions. When employed, in situ synchrotron grazing-incidence X-ray diffraction (GI-XRD) can provide time-resolved structural information of materials formed at the electrode surface. In situ cells, however, often require epoxy resins to secure electrodes, do not enable electrolyte flow, or exhibit limited chemical compatibility, hindering the study of non-aqueous electrochemical systems. Here, a versatile electrochemical cell for air-free in situ synchrotron GI-XRD during non-aqueous Li-mediated electrochemical N2 reduction (Li-N2R) has been designed. This cell not only fulfills the stringent material requirements necessary to study this system but is also readily extendable to other electrochemical systems. Under conditions relevant to non-aqueous Li-N2R, the formation of Li metal, LiOH and Li2O as well as a peak consistent with the alpha-phase of Li3N was observed, thus demonstrating the functionality of this cell toward developing a mechanistic understanding of complicated electrochemical systems.
View details for DOI 10.1107/S1600577523006331
View details for PubMedID 37594864
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Carbon flowers as electrocatalysts for the reduction of oxygen to hydrogen peroxide
NANO RESEARCH
2023
View details for DOI 10.1007/s12274-023-5903-8
View details for Web of Science ID 001030509300001
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Electrochemical Flow Reactor Design Allows Tunable Mass Transport Conditions for Operando Surface Enhanced Infrared Absorption Spectroscopy
CHEMCATCHEM
2023
View details for DOI 10.1002/cctc.202300520
View details for Web of Science ID 001031465700001
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Mechanistic Insights into Aldehyde Production from Electrochemical CO2 Reduction on CuAg Alloy via Operando X-ray Measurements
ACS CATALYSIS
2023: 9379-9391
View details for DOI 10.1021/acscatal.3c01009
View details for Web of Science ID 001020631700001
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Combined, time-resolved, in situ neutron reflectometry and X-ray diffraction analysis of dynamic SEI formation during electrochemical N-2 reduction
ENERGY & ENVIRONMENTAL SCIENCE
2023
View details for DOI 10.1039/d2ee03694k
View details for Web of Science ID 001018487700001
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A framework for understanding efficient diurnal CO2 reduction using Si and GaAs photocathodes
CHEM CATALYSIS
2023; 3 (6)
View details for DOI 10.1016/j.checat.2023.100641
View details for Web of Science ID 001023692400001
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Tracking the Dynamics of a Ag-MnO x Oxygen Reduction Catalyst Using In Situ and Operando X-ray Absorption Near-Edge Spectroscopy
ACS ENERGY LETTERS
2023
View details for DOI 10.1021/acsenergylett.3c00823
View details for Web of Science ID 001015819200001
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Hydrogen production with seawater-resilient bipolar membrane electrolyzers
JOULE
2023; 7 (4): 765-781
View details for DOI 10.1016/j.joule.2023.03.005
View details for Web of Science ID 000988108000001
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Insights into Active Sites and Mechanisms of Benzyl Alcohol Oxidation on Nickel-Iron Oxyhydroxide Electrodes
ACS CATALYSIS
2023: 4272-4282
View details for DOI 10.1021/acscatal.2c05656
View details for Web of Science ID 000953973700001
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Understanding the Stability of Manganese Chromium Antimonate Electrocatalysts through Multimodal In Situ and Operando Measurements.
Journal of the American Chemical Society
2022
Abstract
Improving electrocatalyst stability is critical for the development of electrocatalytic devices. Herein, we utilize an on-line electrochemical flow cell coupled with an inductively coupled plasma-mass spectrometer (ICP-MS) to characterize the impact of composition and reactant gas on the multielement dissolution of Mn(-Cr)-Sb-O electrocatalysts. Compared to Mn2O3 and Cr2O3 oxides, the antimonate framework stabilizes Mn at OER potentials and Cr at both ORR and OER potentials. Furthermore, dissolution of Mn and Cr from Mn(-Cr) -Sb-O is driven by the ORR reaction rate, with minimal dissolution under N2. We observe preferential dissolution of Cr totaling 13% over 10 min at 0.3, 0.6, and 0.9 V vs RHE, with only 1.5% loss of Mn, indicating an enrichment of Mn at the surface of the particles. Despite this asymmetric dissolution, operando X-ray absorption spectroscopy (XAS) showed no measurable changes in the Mn K-edge at comparable potentials. This could suggest that modification to the Mn oxidation state and/or phase in the surface layer is too small or that the layer is too thin to be measured with the bulk XAS measurement. Lastly, on-line ICP-MS was used to assess the effects of applied potential, scan rate, and current on Mn-Cr-Sb-O during cyclic voltammetry and accelerated stress tests. With this deeper understanding of the interplay between oxygen reduction and dissolution, testing procedures were identified to maximize both activity and stability. This work highlights the use of multimodal in situ characterization techniques in tandem to build a more complete model of stability and develop protocols for optimizing catalyst performance.
View details for DOI 10.1021/jacs.2c08600
View details for PubMedID 36453840
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A Versatile Li0.5FePO4 Reference Electrode for Nonaqueous Electrochemical Conversion Technologies
ACS ENERGY LETTERS
2022: 230-235
View details for DOI 10.1021/acsenergylett.2c02190
View details for Web of Science ID 000891330700001
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Investigation of the Structure of Atomically Dispersed NiNx Sites in Ni and N-Doped Carbon Electrocatalysts by 61Ni Mossbauer Spectroscopy and Simulations.
Journal of the American Chemical Society
2022
Abstract
Ni and nitrogen-doped carbons are selective catalysts for CO2 reduction to CO (CO2R), but the hypothesized NiNx active sites are challenging to probe with traditional characterization methods. Here, we synthesize 61Ni-enriched model catalysts, termed 61NiPACN, in order to apply 61Ni Mossbauer spectroscopy using synchrotron radiation (61Ni-SR-MS) to characterize the structure of these atomically dispersed NiNx sites. First, we demonstrate that the CO2R results and standard characterization techniques (SEM, PXRD, XPS, XANES, EXAFS) point to the existence of dispersed Ni active sites. Then, 61Ni-SR-MS reveal significant internal magnetic fields of 5.4 T, which is characteristic of paramagnetic, high-spin Ni2+, in the 61NiPACN samples. Finally, theoretical calculations for a variety of Ni-Nx moieties confirm that high-spin Ni2+ is stable in non-planar, tetrahedrally distorted geometries, which results in calculated isotropic hyperfine coupling that is consistent with 61Ni-SR-MS measurements.
View details for DOI 10.1021/jacs.2c09825
View details for PubMedID 36394993
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Bridging knowledge gaps in liquid- and vapor-fed CO2 electrolysis through active electrode area
CHEM CATALYSIS
2022; 2 (11): 3239-3253
View details for DOI 10.1016/j.checat.2022.09.017
View details for Web of Science ID 000901471000011
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Origins of wear-induced tungsten corrosion defects in semiconductor manufacturing during tungsten chemical mechanical polishing
APPLIED SURFACE SCIENCE
2022; 598
View details for DOI 10.1016/j.apsusc.2022.153767
View details for Web of Science ID 000818529100002
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Strategies for Modulating the Catalytic Activity and Selectivity of Manganese Antimonates for the Oxygen Reduction Reaction
ACS CATALYSIS
2022
View details for DOI 10.1021/acscatal.2c01764
View details for Web of Science ID 000844309700001
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New challenges in oxygen reduction catalysis: a consortium retrospective to inform future research
ENERGY & ENVIRONMENTAL SCIENCE
2022
View details for DOI 10.1039/d2ee01333a
View details for Web of Science ID 000834905400001
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Alloyed Pt-Zn Oxygen Reduction Catalysts for Proton Exchange Membrane Fuel Cells
ACS APPLIED ENERGY MATERIALS
2022
View details for DOI 10.1021/acsaem.2c00816
View details for Web of Science ID 000829265400001
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Lithium-Mediated Electrochemical Nitrogen Reduction: Tracking Electrode-Electrolyte Interfaces via Time-Resolved Neutron Reflectometry
ACS ENERGY LETTERS
2022; 7 (6): 1939-1946
View details for DOI 10.1021/acsenergylett.1c02833
View details for Web of Science ID 000810534300001
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Methods-A Practical Approach to the Reversible Hydrogen Electrode Scale
JOURNAL OF THE ELECTROCHEMICAL SOCIETY
2022; 169 (6)
View details for DOI 10.1149/1945-7111/ac71d1
View details for Web of Science ID 000806520100001
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Vapor-Fed Electrolyzers for Carbon Dioxide Reduction Using Tandem Electrocatalysts: Cuprous Oxide Coupled with Nickel-Coordinated Nitrogen-Doped Carbon
ADVANCED FUNCTIONAL MATERIALS
2022
View details for DOI 10.1002/adfm.202113252
View details for Web of Science ID 000793243300001
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Enhancing the connection between computation and experiments in electrocatalysis
NATURE CATALYSIS
2022; 5 (5): 374-381
View details for DOI 10.1038/s41929-022-00789-0
View details for Web of Science ID 000801852700007
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Using pH Dependence to Understand Mechanisms in Electrochemical CO Reduction br
ACS CATALYSIS
2022; 12 (8): 4344-4357
View details for DOI 10.1021/acscatal.1c05520
View details for Web of Science ID 000791836500011
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First-Row Transition Metal Antimonates for the Oxygen Reduction Reaction.
ACS nano
2022
Abstract
The development of inexpensive and abundant catalysts with high activity, selectivity, and stability for the oxygen reduction reaction (ORR) is imperative for the widespread implementation of fuel cell devices. Herein, we present a combined theoretical-experimental approach to discover and design first-row transition metal antimonates as excellent electrocatalytic materials for the ORR. Theoretically, we identify first-row transition metal antimonates─MSb2O6, where M = Mn, Fe, Co, and Ni─as nonprecious metal catalysts with good oxygen binding energetics, conductivity, thermodynamic phase stability, and aqueous stability. Among the considered antimonates, MnSb2O6 shows the highest theoretical ORR activity based on the 4e- ORR kinetic volcano. Experimentally, nanoparticulate transition metal antimonate catalysts are found to have a minimum of a 2.5-fold enhancement in intrinsic mass activity (on transition metal mass basis) relative to the corresponding transition metal oxide at 0.7 V vs RHE in 0.1 M KOH. MnSb2O6 is the most active catalyst under these conditions, with a 3.5-fold enhancement on a per Mn mass activity basis and 25-fold enhancement on a surface area basis over its antimony-free counterpart. Electrocatalytic and material stability are demonstrated over a 5 h chronopotentiometry experiment in the stability window identified by theoretical Pourbaix analysis. This study further highlights the stable and electrically conductive antimonate structure as a framework to tune the activity and selectivity of nonprecious metal oxide active sites for ORR catalysis.
View details for DOI 10.1021/acsnano.2c00420
View details for PubMedID 35377139
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Engineering metal-metal oxide surfaces for high-performance oxygen reduction on Ag-Mn electrocatalysts
ENERGY & ENVIRONMENTAL SCIENCE
2022
View details for DOI 10.1039/d2ee00047d
View details for Web of Science ID 000766715400001
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Acid anion electrolyte effects on platinum for oxygen and hydrogen electrocatalysis
COMMUNICATIONS CHEMISTRY
2022; 5 (1)
View details for DOI 10.1038/s42004-022-00635-1
View details for Web of Science ID 000757832500001
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Acid anion electrolyte effects on platinum for oxygen and hydrogen electrocatalysis.
Communications chemistry
2022; 5 (1): 20
Abstract
Platinum is an important material with applications in oxygen and hydrogen electrocatalysis. To better understand how its activity can be modulated through electrolyte effects in the double layer microenvironment, herein we investigate the effects of different acid anions on platinum for the oxygen reduction/evolution reaction (ORR/OER) and hydrogen evolution/oxidation reaction (HER/HOR) in pH 1 electrolytes. Experimentally, we see the ORR activity trend of HClO4 > HNO3 > H2SO4, and the OER activity trend of HClO4 [Formula: see text] HNO3 ∼ H2SO4. HER/HOR performance is similar across all three electrolytes. Notably, we demonstrate that ORR performance can be improved 4-fold in nitric acid compared to in sulfuric acid. Assessing the potential-dependent role of relative anion competitive adsorption with density functional theory, we calculate unfavorable adsorption on Pt(111) for all the anions at HER/HOR conditions while under ORR/OER conditions [Formula: see text] binds the weakest followed by [Formula: see text] and [Formula: see text]. Our combined experimental-theoretical work highlights the importance of understanding the role of anions across a large potential range and reveals nitrate-like electrolyte microenvironments as interesting possible sulfonate alternatives to mitigate the catalyst poisoning effects of polymer membranes/ionomers in electrochemical systems. These findings help inform rational design approaches to further enhance catalyst activity via microenvironment engineering.
View details for DOI 10.1038/s42004-022-00635-1
View details for PubMedID 36697647
View details for PubMedCentralID PMC9814610
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Gas diffusion electrodes, reactor designs and key metrics of low-temperature CO2 electrolysers
NATURE ENERGY
2022
View details for DOI 10.1038/s41560-021-00973-9
View details for Web of Science ID 000757201800001
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Characterization of a Dynamic Y2Ir2O7 Catalyst during the Oxygen Evolution Reaction in Acid
JOURNAL OF PHYSICAL CHEMISTRY C
2022
View details for DOI 10.1021/acs.jpcc.1c07760
View details for Web of Science ID 000746684300001
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Demonstration of photoreactor platform for on-sun unassisted photoelectrochemical hydrogen generation with tandem III-V photoelectrodes
CHEM CATALYSIS
2022; 2 (1): 195-209
View details for DOI 10.1016/j.checat.2021.12.013
View details for Web of Science ID 000901338900018
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Evaluating the Case for Reduced Precious Metal Catalysts in Proton Exchange Membrane Electrolyzers
ACS ENERGY LETTERS
2022; 7 (1): 17-23
View details for DOI 10.1021/acsenergylett.1c01869
View details for Web of Science ID 000769973900003
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Engineering Surface Architectures for Improved Durability in III-V Photocathodes.
ACS applied materials & interfaces
1800
Abstract
GaInP2 has shown promise as the wide bandgap top junction in tandem absorber photoelectrochemical (PEC) water splitting devices. Among previously reported dual-junction PEC devices with a GaInP2 top cell, those with the highest performance incorporate an AlInP2 window layer (WL) to reduce surface recombination and a thin GaInP2 capping layer (CL) to protect the WL from corrosion in electrolytes. However, the stability of these III-V systems is limited, and durability continues to be a major challenge broadly in the field of PEC water splitting. This work provides a systematic investigation into the durability of GaInP2 systems, examining the impacts of the window layer and capping layer among single junction pn-GaInP2 photocathodes coated with an MoS2 catalytic and protective layer. The photocathode with both a CL and WL demonstrates the highest PEC performance and longest lifetime, producing a significant current for >125 h. In situ optical imaging and post-test characterization illustrate the progression of macroscopic degradation and chemical state. The surface architecture combining an MoS2 catalyst, CL, and WL can be translated to dual-junction PEC devices with GaInP2 or other III-V top junctions to enable more efficient and stable PEC systems.
View details for DOI 10.1021/acsami.1c18938
View details for PubMedID 35005903
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Improving intrinsic oxygen reduction activity and stability: Atomic layer deposition preparation of platinum-titanium alloy catalysts
APPLIED CATALYSIS B-ENVIRONMENTAL
2022; 300
View details for DOI 10.1016/j.apcatb.2021.120741
View details for Web of Science ID 000707873700001
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Designing a Zn-Ag Catalyst Matrix and Electrolyzer System for CO2 Conversion to CO and Beyond.
Advanced materials (Deerfield Beach, Fla.)
2021: e2103963
Abstract
CO2 emissions can be transformed into high-added-value commodities through CO2 electrocatalysis; however, efficient low-cost electrocatalysts are needed for global scale-up. Inspired by other emerging technologies, the authors report the development of a gas diffusion electrode containing highly dispersed Ag sites in a low-cost Zn matrix. This catalyst shows unprecedented Ag mass activity for CO production: -614mAcm-2 at 0.17mgof Ag. Subsequent electrolyte engineering demonstrates that halide anions can further improve stability and activity of the Zn-Ag catalyst, outperforming pure Ag and Au. Membrane electrode assemblies are constructed and coupled to a microbial process that converts the CO to acetate and ethanol. Combined, these concepts present pathways to design catalysts and systems for CO2 conversion toward sought-after products.
View details for DOI 10.1002/adma.202103963
View details for PubMedID 34672402
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Chemical Modifications of Ag Catalyst Surfaces with Imidazolium Ionomers Modulate H2 Evolution Rates during Electrochemical CO2 Reduction.
Journal of the American Chemical Society
2021
Abstract
Bridging polymer design with catalyst surface science is a promising direction for tuning and optimizing electrochemical reactors that could impact long-term goals in energy and sustainability. Particularly, the interaction between inorganic catalyst surfaces and organic-based ionomers provides an avenue to both steer reaction selectivity and promote activity. Here, we studied the role of imidazolium-based ionomers for electrocatalytic CO2 reduction to CO (CO2R) on Ag surfaces and found that they produce no effect on CO2R activity yet strongly promote the competing hydrogen evolution reaction (HER). By examining the dependence of HER and CO2R rates on concentrations of CO2 and HCO3-, we developed a kinetic model that attributes HER promotion to intrinsic promotion of HCO3- reduction by imidazolium ionomers. We also show that varying the ionomer structure by changing substituents on the imidazolium ring modulates the HER promotion. This ionomer-structure dependence was analyzed via Taft steric parameters and density functional theory calculations, which suggest that steric bulk from functionalities on the imidazolium ring reduces access of the ionomer to both HCO3- and the Ag surface, thus limiting the promotional effect. Our results help develop design rules for ionomer-catalyst interactions in CO2R and motivate further work into precisely uncovering the interplay between primary and secondary coordination in determining electrocatalytic behavior.
View details for DOI 10.1021/jacs.1c06212
View details for PubMedID 34472346
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Electrolyte-Guided Design of Electroreductive CO Coupling on Copper Surfaces
ACS APPLIED ENERGY MATERIALS
2021; 4 (8): 8201-8210
View details for DOI 10.1021/acsaem.1c01427
View details for Web of Science ID 000688250200081
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Dynamics and Hysteresis of Hydrogen Intercalation and Deintercalation in Palladium Electrodes: A Multimodal In Situ X-ray Diffraction, Coulometry, and Computational Study
CHEMISTRY OF MATERIALS
2021; 33 (15): 5872-5884
View details for DOI 10.1021/acs.chemmater.1c00291
View details for Web of Science ID 000685206200005
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Probing the Effects of Acid Electrolyte Anions on Electrocatalyst Activity and Selectivity for the Oxygen Reduction Reaction
CHEMELECTROCHEM
2021; 8 (13): 2467-2478
View details for DOI 10.1002/celc.202100500
View details for Web of Science ID 000674273100011
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Phosphate-passivated mordenite for tandem-catalytic conversion of syngas to ethanol or acetic acid
JOURNAL OF CATALYSIS
2021; 399: 132-141
View details for DOI 10.1016/j.jcat.2021.04.029
View details for Web of Science ID 000659913700013
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Understanding Degradation Mechanisms in SrIrO3 Oxygen Evolution Electrocatalysts: Chemical and Structural Microscopy at the Nanoscale
ADVANCED FUNCTIONAL MATERIALS
2021
View details for DOI 10.1002/adfm.202101542
View details for Web of Science ID 000662722100001
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Direct Integration of Strained-Pt Catalysts into Proton-Exchange-Membrane Fuel Cells with Atomic Layer Deposition.
Advanced materials (Deerfield Beach, Fla.)
2021: e2007885
Abstract
The design and fabrication of lattice-strained platinum catalysts achieved by removing a soluble core from a platinum shell synthesized via atomic layer deposition, is reported. The remarkable catalytic performance for the oxygen reduction reaction (ORR), measured in both half-cell and full-cell configurations, is attributed to the observed lattice strain. By further optimizing the nanoparticle geometry and ionomer/carbon interactions, mass activity close to 0.8AmgPt -1 @0.9V iR-free is achievable in the membrane electrode assembly. Nevertheless, active catalysts with high ORR activity do not necessarily lead to high performance in the high-current-density (HCD) region. More attention shall be directed toward HCD performance for enabling high-power-density hydrogen fuel cells.
View details for DOI 10.1002/adma.202007885
View details for PubMedID 34110653
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A refraction correction for buried interfaces applied to in situ grazing-incidence X-ray diffraction studies on Pd electrodes.
Journal of synchrotron radiation
2021; 28 (Pt 3): 919–23
Abstract
In situ characterization of electrochemical systems can provide deep insights into the structure of electrodes under applied potential. Grazing-incidence X-ray diffraction (GIXRD) is a particularly valuable tool owing to its ability to characterize the near-surface structure of electrodes through a layer of electrolyte, which is of paramount importance in surface-mediated processes such as catalysis and adsorption. Corrections for the refraction that occurs as an X-ray passes through an interface have been derived for a vacuum-material interface. In this work, a more general form of the refraction correction was developed which can be applied to buried interfaces, including liquid-solid interfaces. The correction is largest at incidence angles near the critical angle for the interface and decreases at angles larger and smaller than the critical angle. Effective optical constants are also introduced which can be used to calculate the critical angle for total external reflection at the interface. This correction is applied to GIXRD measurements of an aqueous electrolyte-Pd interface, demonstrating that the correction allows for the comparison of GIXRD measurements at multiple incidence angles. This work improves quantitative analysis of d-spacing values from GIXRD measurements of liquid-solid systems, facilitating the connection between electrochemical behavior and structure under in situ conditions.
View details for DOI 10.1107/S1600577521001557
View details for PubMedID 33949999
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Advanced manufacturing for electrosynthesis of fuels and chemicals from CO2
ENERGY & ENVIRONMENTAL SCIENCE
2021; 14 (5): 3064-3074
View details for DOI 10.1039/d0ee03679j
View details for Web of Science ID 000652354100036
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Isolating the Electrocatalytic Activity of a Confined NiFe Motif within Zirconium Phosphate
ADVANCED ENERGY MATERIALS
2021
View details for DOI 10.1002/aenm.202003545
View details for Web of Science ID 000639983100001
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Bridging thermal catalysis and electrocatalysis: Catalyzing CO2 conversion with carbon-based materials.
Angewandte Chemie (International ed. in English)
2021
Abstract
Understanding the differences between reactions driven by elevated temperature or electric potential remains challenging, largely due to materials incompatibilities between thermal catalytic and electrocatalytic environments. We show that Ni, N-doped carbon (NiPACN), an electrocatalyst for the reduction of CO2 to CO (CO2R), can also selectively catalyze thermal CO2 to CO via the reverse water gas shift (RWGS) representing a direct analogy between catalytic phenomena across the two reaction environments. Advanced characterization techniques reveal that NiPACN likely facilitates RWGS on dispersed Ni sites in agreement with CO2R active site studies. Finally, we construct a generalized reaction driving-force that includes temperature and potential and suggest that NiPACN could facilitate faster kinetics in CO2R relative to RWGS due to lower intrinsic barriers. This report motivates further studies that quantitatively link catalytic phenomena across disparate reaction environments.
View details for DOI 10.1002/anie.202101326
View details for PubMedID 33823079
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Cobalt porphyrin intercalation into zirconium phosphate layers for electrochemical water oxidation
SUSTAINABLE ENERGY & FUELS
2021; 5 (2): 430–37
View details for DOI 10.1039/d0se01134g
View details for Web of Science ID 000611818900011
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Tungsten oxide-coated copper gallium selenide sustains long-term solar hydrogen evolution
SUSTAINABLE ENERGY & FUELS
2021; 5 (2): 384–90
View details for DOI 10.1039/d0se00487a
View details for Web of Science ID 000611818900005
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Bottom-Up Fabrication of Oxygen Reduction Electrodes with Atomic Layer Deposition for High-Power-Density PEMFCs
CELL REPORTS PHYSICAL SCIENCE
2021; 2 (1)
View details for DOI 10.1016/j.xcrp.2020.100297
View details for Web of Science ID 000658759800014
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CO as a Probe Molecule to Study Surface Adsorbates during Electrochemical Oxidation of Propene
CHEMELECTROCHEM
2021; 8 (1): 250–56
View details for DOI 10.1002/celc.202001162
View details for Web of Science ID 000607645400031
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Understanding Selectivity in CO2 Hydrogenation to Methanol for MoP Nanoparticle Catalysts Using In Situ Techniques
CATALYSTS
2021; 11 (1)
View details for DOI 10.3390/catal11010143
View details for Web of Science ID 000610007900001
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Guiding the Catalytic Properties of Copper for Electrochemical CO2 Reduction by Metal Atom Decoration.
ACS applied materials & interfaces
2021
Abstract
Tuning bimetallic effects is a promising strategy to guide catalytic properties. However, the nature of these effects can be difficult to assess and compare due to the convolution with other factors such as the catalyst surface structure and morphology and differences in testing environments. Here, we investigate the impact of atomic-scale bimetallic effects on the electrochemical CO2 reduction performance of Cu-based catalysts by leveraging a systematic approach that unifies protocols for materials synthesis and testing and enables accurate comparisons of intrinsic catalytic activity and selectivity. We used the same physical vapor deposition method to epitaxially grow Cu(100) films decorated with a small amount of noble or base metal atoms and a combination of experimental characterization and first-principles calculations to evaluate their physicochemical and catalytic properties. The results indicate that the metal atoms segregate to under-coordinated Cu sites during physical vapor deposition, suppressing CO reduction to oxygenates and hydrocarbons and promoting competing pathways to CO, formate, and hydrogen. Leveraging these insights, we rationalize bimetallic design principles to improve catalytic selectivity for CO2 reduction to CO, formate, oxygenates, or hydrocarbons. Our study provides one of the most extensive studies on Cu bimetallics for CO2 reduction, establishing a systematic approach that is broadly applicable to research in catalyst discovery.
View details for DOI 10.1021/acsami.1c09128
View details for PubMedID 34415714
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Tuning the electronic structure of Ag-Pd alloys to enhance performance for alkaline oxygen reduction.
Nature communications
2021; 12 (1): 620
Abstract
Alloying is a powerful tool that can improve the electrocatalytic performance and viability of diverse electrochemical renewable energy technologies. Herein, we enhance the activity of Pd-based electrocatalysts via Ag-Pd alloying while simultaneously lowering precious metal content in a broad-range compositional study focusing on highly comparable Ag-Pd thin films synthesized systematically via electron-beam physical vapor co-deposition. Cyclic voltammetry in 0.1 M KOH shows enhancements across a wide range of alloys; even slight alloying with Ag (e.g. Ag0.1Pd0.9) leads to intrinsic activity enhancements up to 5-fold at 0.9 V vs. RHE compared to pure Pd. Based on density functional theory and x-ray absorption, we hypothesize that these enhancements arise mainly from ligand effects that optimize adsorbate-metal binding energies with enhanced Ag-Pd hybridization. This work shows the versatility of coupled experimental-theoretical methods in designing materials with specific and tunable properties and aids the development of highly active electrocatalysts with decreased precious-metal content.
View details for DOI 10.1038/s41467-021-20923-z
View details for PubMedID 33504815
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Identifying and Tuning the In Situ Oxygen-Rich Surface of Molybdenum Nitride Electrocatalysts for Oxygen Reduction
ACS APPLIED ENERGY MATERIALS
2020; 3 (12): 12433–46
View details for DOI 10.1021/acsaem.0c02423
View details for Web of Science ID 000618839200099
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Acidic Oxygen Evolution Reaction Activity-Stability Relationships in Ru-Based Pyrochlores
ACS CATALYSIS
2020; 10 (20): 12182–96
View details for DOI 10.1021/acscatal.0c02252
View details for Web of Science ID 000614389200044
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Direct Characterization of Atomically Dispersed Catalysts: Nitrogen-Coordinated Ni Sites in Carbon-Based Materials for CO(2)Electroreduction
ADVANCED ENERGY MATERIALS
2020
View details for DOI 10.1002/aenm.202001836
View details for Web of Science ID 000565386000001
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Addressing the Stability Gap in Photoelectrochemistry: Molybdenum Disulfide Protective Catalysts for Tandem III-V Unassisted Solar Water Splitting
ACS ENERGY LETTERS
2020; 5 (8): 2631–40
View details for DOI 10.1021/acsenergylett.0c01132
View details for Web of Science ID 000562954100024
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Nanosized Zirconium Porphyrinic Metal-Organic Frameworks that Catalyze the Oxygen Reduction Reaction in Acid
SMALL METHODS
2020
View details for DOI 10.1002/smtd.202000085
View details for Web of Science ID 000557369400001
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Low-pressure methanol synthesis from CO2 over metal-promoted Ni-Ga intermetallic catalysts
JOURNAL OF CO2 UTILIZATION
2020; 39
View details for DOI 10.1016/j.jcou.2020.03.001
View details for Web of Science ID 000546648400007
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Ni5Ga3 catalysts for CO2 reduction to methanol: Exploring the role of Ga surface oxidation/reduction on catalytic activity
APPLIED CATALYSIS B-ENVIRONMENTAL
2020; 267
View details for DOI 10.1016/j.apcatb.2019.118369
View details for Web of Science ID 000518865300047
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A cyclic electrochemical strategy to produce acetylene from CO2, CH4, or alternative carbon sources
SUSTAINABLE ENERGY & FUELS
2020; 4 (6): 2752–59
View details for DOI 10.1039/c9se00799g
View details for Web of Science ID 000539290400013
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Nitride or Oxynitride? Elucidating the Composition-Activity Relationships in Molybdenum Nitride Electrocatalysts for the Oxygen Reduction Reaction
CHEMISTRY OF MATERIALS
2020; 32 (7): 2946–60
View details for DOI 10.1021/acs.chemmater.9b05212
View details for Web of Science ID 000526394000025
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In Situ X-Ray Absorption Spectroscopy Disentangles the Roles of Copper and Silver in a Bimetallic Catalyst for the Oxygen Reduction Reaction
CHEMISTRY OF MATERIALS
2020; 32 (5): 1819–27
View details for DOI 10.1021/acs.chemmater.9b03963
View details for Web of Science ID 000519337600008
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Electrolyte Engineering for Efficient Electrochemical Nitrate Reduction to Ammonia on a Titanium Electrode
ACS SUSTAINABLE CHEMISTRY & ENGINEERING
2020; 8 (7): 2672–81
View details for DOI 10.1021/acssuschemeng.9b05983
View details for Web of Science ID 000516665500010
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Using Microenvironments to Control Reactivity in CO2 Electrocatalysis
JOULE
2020; 4 (2): 292–94
View details for DOI 10.1016/j.joule.2020.01.017
View details for Web of Science ID 000515121700005
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A Combined Theory-Experiment Analysis of the Surface Species in Lithium-Mediated NH3 Electrosynthesis
CHEMELECTROCHEM
2020
View details for DOI 10.1002/celc.201902124
View details for Web of Science ID 000510258500001
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Selective reduction of CO to acetaldehyde with CuAg electrocatalysts.
Proceedings of the National Academy of Sciences of the United States of America
2020
Abstract
Electrochemical CO reduction can serve as a sequential step in the transformation of CO2 into multicarbon fuels and chemicals. In this study, we provide insights on how to steer selectivity for CO reduction almost exclusively toward a single multicarbon oxygenate by carefully controlling the catalyst composition and its surrounding reaction conditions. Under alkaline reaction conditions, we demonstrate that planar CuAg electrodes can reduce CO to acetaldehyde with over 50% Faradaic efficiency and over 90% selectivity on a carbon basis at a modest electrode potential of -0.536 V vs. the reversible hydrogen electrode. The Faradaic efficiency to acetaldehyde was further enhanced to 70% by increasing the roughness factor of the CuAg electrode. Density functional theory calculations indicate that Ag ad-atoms on Cu weaken the binding energy of the reduced acetaldehyde intermediate and inhibit its further reduction to ethanol, demonstrating that the improved selectivity to acetaldehyde is due to the electronic effect from Ag incorporation. These findings will aid in the design of catalysts that are able to guide complex reaction networks and achieve high selectivity for the desired product.
View details for DOI 10.1073/pnas.1821683117
View details for PubMedID 31980521
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Morphology control of metal-modified zirconium phosphate support structures for the oxygen evolution reaction.
Dalton transactions (Cambridge, England : 2003)
2020
Abstract
The electrochemical oxygen evolution reaction (OER) is the half-cell reaction for many clean-energy production technologies, including water electrolyzers and metal-air batteries. However, its sluggish kinetics hinders the performance of those technologies, impeding them from broader implementation. Recently, we reported the use of zirconium phosphate (ZrP) as a support for transition metal catalysts for the oxygen evolution reaction (OER). These catalysts achieve promising overpotentials with high mass activities. Herein, we synthesize ZrP structures with controlled morphology: hexagonal platelets, rods, cubes, and spheres, and subsequently modify them with Co(ii) and Ni(ii) cations to assess their electrochemcial OER behavior. Through inductively coupled plasma mass-spectrometry measurements, the maximum ion exchange capacity is found to vary based on the morphology of the ZrP structure and cation selection. Trends in geometric current density and mass activity as a function of cation selection are discussed. We find that the loading and coverage of cobalt and nickel species on the ZrP supports are key factors that control OER performance.
View details for DOI 10.1039/c9dt04135d
View details for PubMedID 31894216
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A Spin Coating Method To Deposit Iridium-Based Catalysts onto Silicon for Water Oxidation Photoanodes.
ACS applied materials & interfaces
2020
Abstract
Silicon has shown promise for use as a small band gap (1.1 eV) absorber material in photoelectrochemical (PEC) water splitting. However, the limited stability of silicon in acidic electrolyte requires the use of protection strategies coupled with catalysts. Herein, spin coating is used as a versatile method to directly coat silicon photoanodes with an IrO x oxygen evolution reaction (OER) catalyst, reducing the processing complexity compared to conventional fabrication schemes. Biphasic strontium chloride/iridium oxide (SrCl2:IrO x ) catalysts are also developed, and both catalysts form photoactive junctions with silicon and demonstrate high photoanode activity. The iridium oxide photoanode displays a photocurrent onset at 1.06 V vs reversible hydrogen electrode (RHE), while the SrCl2:IrO x photoanode onsets earlier at 0.96 V vs RHE. The differing potentials are consistent with the observed photovoltages of 0.43 and 0.53 V for the IrO x and SrCl2:IrO x , respectively. By measuring the oxidation of a reversible redox couple, Fe(CN)63-/4-, we compare the charge carrier extraction of the devices and show that the addition of SrCl2 to the IrO x catalyst improves the silicon-electrolyte interface compared to pure IrO x . However, the durability of the strontium-containing photoanode remains a challenge, with its photocurrent density decreasing by 90% over 4 h. The IrO x photoanode, on the other hand, maintained a stable photocurrent density over this timescale. Characterization of the as-prepared and post-tested material structure via Auger electron spectroscopy identifies catalyst film cracking and delamination as the primary failure modes. We propose that improvements to catalyst adhesion should further the viability of spin coating as a technique for photoanode preparation.
View details for DOI 10.1021/acsami.9b20099
View details for PubMedID 31971770
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Readily Constructed Glass Piston Pump for Gas Recirculation.
ACS omega
2020; 5 (27): 16455–59
Abstract
The recirculation of gases in a sealed reactor system is a broadly useful method in catalytic and electrocatalytic studies. It is especially relevant when a reactant gas reacts slowly with respect to residence time in a catalytic reaction zone and when mass transport control through the reaction zone is necessary. This need is well illustrated in the field of electrocatalytic N2 reduction, where the need for recirculation of 15N2 has recently become more apparent. Herein, we describe the design, fabrication, use, and specifications of a lubricant-free, readily constructed recirculating pump fabricated entirely from glass and inert polymer (poly(ether ether ketone) (PEEK), poly(tetrafluoroethylene) (PTFE)) components. Using these glass and polymer components ensures chemical compatibility between the piston pump and a wide range of chemical environments, including strongly acidic and organic electrolytes often employed in studies of electrocatalytic N2 reduction. The lubricant-free nature of the pump and the presence of components made exclusively of glass and PEEK/PTFE mitigate contamination concerns associated with recirculating gases saturated with corrosive or reactive vapors for extended periods. The gas recirculating glass pump achieved a flow rate of >500 mL min-1 N2 against atmospheric pressure at 15 W peak power input and >100 mL min-1 N2 against a differential pressure of +6 in. H2O (∼15 mbar) at 10 W peak power input.
View details for DOI 10.1021/acsomega.0c00742
View details for PubMedID 32685809
View details for PubMedCentralID PMC7364576
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Double layer charging driven carbon dioxide adsorption limits the rate of electrochemical carbon dioxide reduction on Gold.
Nature communications
2020; 11 (1): 33
Abstract
Electrochemical CO[Formula: see text] reduction is a potential route to the sustainable production of valuable fuels and chemicals. Here, we perform CO[Formula: see text] reduction experiments on Gold at neutral to acidic pH values to elucidate the long-standing controversy surrounding the rate-limiting step. We find the CO production rate to be invariant with pH on a Standard Hydrogen Electrode scale and conclude that it is limited by the CO[Formula: see text] adsorption step. We present a new multi-scale modeling scheme that integrates ab initio reaction kinetics with mass transport simulations, explicitly considering the charged electric double layer. The model reproduces the experimental CO polarization curve and reveals the rate-limiting step to be *COOH to *CO at low overpotentials, CO[Formula: see text] adsorption at intermediate ones, and CO[Formula: see text] mass transport at high overpotentials. Finally, we show the Tafel slope to arise from the electrostatic interaction between the dipole of *CO[Formula: see text] and the interfacial field. This work highlights the importance of surface charging for electrochemical kinetics and mass transport.
View details for DOI 10.1038/s41467-019-13777-z
View details for PubMedID 31911585
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Oxidation State and Surface Reconstruction of Cu under CO2 Reduction Conditions from In Situ X-ray Characterization.
Journal of the American Chemical Society
2020
Abstract
The electrochemical CO2 reduction reaction (CO2RR) using Cu-based catalysts holds great potential for producing valuable multi-carbon products from renewable energy. However, the chemical and structural state of Cu catalyst surfaces during the CO2RR remains a matter of debate. Here, we show the structural evolution of the near-surface region of polycrystalline Cu electrodes under in situ conditions through a combination of grazing incidence X-ray absorption spectroscopy (GIXAS) and X-ray diffraction (GIXRD). The in situ GIXAS reveals that the surface oxide layer is fully reduced to metallic Cu before the onset potential for CO2RR, and the catalyst maintains the metallic state across the potentials relevant to the CO2RR. We also find a preferential surface reconstruction of the polycrystalline Cu surface toward (100) facets in the presence of CO2. Quantitative analysis of the reconstruction profiles reveals that the degree of reconstruction increases with increasingly negative applied potentials, and it persists when the applied potential returns to more positive values. These findings show that the surface of Cu electrocatalysts is dynamic during the CO2RR, and emphasize the importance of in situ characterization to understand the surface structure and its role in electrocatalysis.
View details for DOI 10.1021/jacs.0c10017
View details for PubMedID 33382947
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Modified atomic layer deposition of MoS2 thin films
Modified atomic layer deposition of MoS2 thin films
2020; 38: 060403
View details for DOI 10.1116/6.0000641
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Two-Dimensional Conductive Ni-HAB as a Catalyst for the Electrochemical Oxygen Reduction Reaction.
ACS applied materials & interfaces
2020
Abstract
Catalytic systems whose properties can be systematically tuned via changes in synthesis conditions are highly desirable for the next-generation catalyst design and optimization. Herein, we present a two-dimensional (2D) conductive metal-organic framework consisting of M-N4 units (M = Ni, Cu) and a hexaaminobenzene (HAB) linker as a catalyst for the oxygen reduction reaction. By varying synthetic conditions, we prepared two Ni-HAB catalysts with different crystallinities, resulting in catalytic systems with different electric conductivities, electrochemical activity, and stability. We show that crystallinity has a positive impact on conductivity and demonstrate that this improved crystallinity/conductivity improves the catalytic performance of our model system. Additionally, density functional theory simulations were performed to probe the origin of M-HAB's catalytic activity, and they suggest that M-HAB's organic linker acts as the active site with the role of the metal being to modulate the linker sites' binding strength.
View details for DOI 10.1021/acsami.0c09323
View details for PubMedID 32805928
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Understanding the Origin of Highly Selective CO2 Electroreduction to CO on Ni, N-doped Carbon Catalysts.
Angewandte Chemie (International ed. in English)
2020
Abstract
Ni,N-doped carbon catalysts have shown promising catalytic performance for CO 2 electroreduction (CO 2 R) to CO; this activity has been attributed to the presence of nitrogen-coordinated, single metal atom active sites. However, experimentally confirming Ni-N bonding and correlating CO 2 reduction (CO 2 R) activity to these species has remained a fundamental challenge. We synthesized polyacrylonitrile-derived Ni, N-doped carbon electrocatalysts (Ni-PACN) with a range of pyrolysis temperatures and Ni loadings and correlated their electrochemical activity with extensive physiochemical characterization to rigorously address the origin of activity in these materials. We found that the CO- 2 R to CO partial current density increased with increased Ni content before plateauing at 2 wt% which suggests a dispersed Ni active site. These dispersed active sites were investigated by hard and soft x-ray spectroscopy, which revealed that pyrrolic nitrogen ligands selectively bind Ni atoms in a distorted square-planar geometry that strongly resembles the active sites of molecular metal-porphyrin catalysts.
View details for DOI 10.1002/anie.201912857
View details for PubMedID 31919948
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The Materials Research Platform: Defining the Requirements from User Stories
MATTER
2019; 1 (6): 1433–38
View details for DOI 10.1016/j.matt.2019.10.024
View details for Web of Science ID 000519845900003
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A non-precious metal hydrogen catalyst in a commercial polymer electrolyte membrane electrolyser.
Nature nanotechnology
2019
Abstract
We demonstrate the translation of a low-cost, non-precious metal cobalt phosphide (CoP) catalyst from 1cm2 lab-scale experiments to a commercial-scale 86cm2 polymer electrolyte membrane (PEM) electrolyser. A two-step bulk synthesis was adopted to produce CoP on a high-surface-area carbon support that was readily integrated into an industrial PEM electrolyser fabrication process. The performance of the CoP was compared head to head with a platinum-based PEM under the same operating conditions (400psi, 50°C). CoP was found to be active and stable, operating at 1.86Acm-2 for>1,700h of continuous hydrogen production while providing substantial material cost savings relative to platinum. This work illustrates a potential pathway for non-precious hydrogen evolution catalysts developed in past decades to translate to commercial applications.
View details for DOI 10.1038/s41565-019-0550-7
View details for PubMedID 31611657
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Transition Metal Arsenide Catalysts for the Hydrogen Evolution Reaction
JOURNAL OF PHYSICAL CHEMISTRY C
2019; 123 (39): 24007–12
View details for DOI 10.1021/acs.jpcc.9b05738
View details for Web of Science ID 000489086300028
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Surface Engineering of 3D Gas Diffusion Electrodes for High-Performance H-2 Production with Nonprecious Metal Catalysts
ADVANCED ENERGY MATERIALS
2019
View details for DOI 10.1002/aenm.201901824
View details for Web of Science ID 000486842200001
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Aqueous Electrochemical Reduction of Carbon Dioxide and Carbon Monoxide into Methanol with Cobalt Phthalocyanine.
Angewandte Chemie (International ed. in English)
2019
Abstract
CO2 conversion into valuable molecules has emerged as a field of intensive investigation, with the aim of ultimately developing scalable technologies for making fuels using renewable sources of energy. Electrochemically reduction into CO and formate getting closer from industrial maturity, the challenge is now to obtain more reduced products like methanol, an already commercialized fuel. At the contrary, literature is really scarce on the matter, and even more when using molecular catalyst. Here, we demonstrate that cobalt phthalocyanine, a long known catalyst for the CO2 to CO electrochemical step, can also catalyse the reaction from CO2 or CO until methanol in aqueous electrolyte, at ambient temperature and atmospheric pressure. Detailed studies identified formaldehyde as key intermediate and unexpected pH effect on selectivity. This paves the way for establishing a sequential process where CO2 is first converted to CO and is subsequently used as reactant to produce methanol. In optimal conditions, CO2 could be catalyzed to CH3OH with a 19.5% global Faradaic efficiency and 7.5% chemical selectivity.
View details for DOI 10.1002/anie.201909257
View details for PubMedID 31496012
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Understanding vapor-fed carbon dioxide reduction at the gas diffusion electrode and electrolyte interface Using flow-electrolyte systems
AMER CHEMICAL SOC. 2019
View details for Web of Science ID 000525055505347
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Promoting reliable electrocatalytic N2 reduction
AMER CHEMICAL SOC. 2019
View details for Web of Science ID 000525055502400
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Crystalline Strontium Iridate Particle Catalysts for Enhanced Oxygen Evolution in Acid
ACS APPLIED ENERGY MATERIALS
2019; 2 (8): 5490–98
View details for DOI 10.1021/acsaem.9b00658
View details for Web of Science ID 000483434700019
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Electro-Oxidation of Methane on Platinum under Ambient Conditions
ACS CATALYSIS
2019; 9 (8): 7578–87
View details for DOI 10.1021/acscatal.9b01207
View details for Web of Science ID 000480503700098
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Electrochemically converting carbon monoxide to liquid fuels by directing selectivity with electrode surface area
NATURE CATALYSIS
2019; 2 (8): 702–8
View details for DOI 10.1038/s41929-019-0301-z
View details for Web of Science ID 000481511400011
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Interfacial engineering of gallium indium phosphide photoelectrodes for hydrogen evolution with precious metal and non-precious metal based catalysts
JOURNAL OF MATERIALS CHEMISTRY A
2019; 7 (28): 16821–32
View details for DOI 10.1039/c9ta05247j
View details for Web of Science ID 000476599900020
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Precious Metal-Free Nickel Nitride Catalyst for the Oxygen Reduction Reaction.
ACS applied materials & interfaces
2019
Abstract
With promising activity and stability for the oxygen reduction reaction (ORR), transition metal nitrides are an interesting class of non-platinum group catalysts for polymer electrolyte membrane fuel cells. Here, we report an active thin-film nickel nitride catalyst synthesized through a reactive sputtering method. In rotating disk electrode testing in a 0.1 M HClO4 electrolyte, the crystalline nickel nitride film achieved high activity and selectivity to four-electron ORR. It also exhibited good stability during 10 and 40 h chronoamperometry measurements in acid and alkaline electrolyte, respectively. A combined experiment-theory approach, with detailed ex situ materials characterization and density functional theory calculations, provides insight into the structure of the catalyst and its surface during catalysis. Design strategies for activity and stability improvement through alloying and nanostructuring are discussed.
View details for DOI 10.1021/acsami.9b07116
View details for PubMedID 31310093
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A Versatile Method for Ammonia Detection in a Range of Relevant Electrolytes via Direct Nuclear Magnetic Resonance Techniques
ACS CATALYSIS
2019; 9 (7): 5797–5802
View details for DOI 10.1021/acscatal.9b00358
View details for Web of Science ID 000474812400001
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A rigorous electrochemical ammonia synthesis protocol with quantitative isotope measurements.
Nature
2019
Abstract
The electrochemical synthesis of ammonia from nitrogen under mild conditions and using renewable electricity is in principle an attractive alternative1-4 to the demanding, energy-intense Haber-Bosch process, which dominates industrial ammonia production. However, the electrochemical alternative faces considerable scientific and technical challenges5,6 and most experimental studies reported thus far achieve only low selectivities and conversions. In fact, the amount of ammonia produced is usually so small that it is difficult to firmly attribute it to electrochemical nitrogen fixation7-9 and exclude contamination due to ammonia that is either present in air, human breath or ion-conducting membranes9, or generated from labile nitrogen-containing compounds (for example, nitrates, amines, nitrites and nitrogen oxides) that are typically present in the nitrogen gas stream10, in the atmosphere or even the catalyst itself. Although these many and varied sources of potential experimental artefacts are beginning to be recognized and dealt with11,12, concerted efforts to develop effective electrochemical nitrogen reduction processes would benefit from benchmarking protocols for the reaction and from a standardized set of control experiments to identify and then eliminate or quantify contamination sources. Here we put forward such a rigorous procedure that, by making essential use of 15N2, allows us to reliably detect and quantify the electroreduction of N2 to NH3. We demonstrate experimentally the significance of various sources of contamination and show how to remove labile nitrogen-containing compounds present in the N2 gas and how to perform quantitative isotope measurements with cycling of 15N2 gas to reduce both contamination and the cost of isotope measurements. Following this protocol, we obtain negative results when using the most promising pure metal catalysts in aqueous media, and successfully confirm and quantify ammonia synthesis using lithium electrodeposition in tetrahydrofuran13.
View details for DOI 10.1038/s41586-019-1260-x
View details for PubMedID 31117118
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Progress and Perspectives of Electrochemical CO2 Reduction on Copper in Aqueous Electrolyte.
Chemical reviews
2019
Abstract
To date, copper is the only heterogeneous catalyst that has shown a propensity to produce valuable hydrocarbons and alcohols, such as ethylene and ethanol, from electrochemical CO2 reduction (CO2R). There are variety of factors that impact CO2R activity and selectivity, including the catalyst surface structure, morphology, composition, the choice of electrolyte ions and pH, and the electrochemical cell design. Many of these factors are often intertwined, which can complicate catalyst discovery and design efforts. Here we take a broad and historical view of these different aspects and their complex interplay in CO2R catalysis on Cu, with the purpose of providing new insights, critical evaluations, and guidance to the field with regard to research directions and best practices. First, we describe the various experimental probes and complementary theoretical methods that have been used to discern the mechanisms by which products are formed, and next we present our current understanding of the complex reaction networks for CO2R on Cu. We then analyze two key methods that have been used in attempts to alter the activity and selectivity of Cu: nanostructuring and the formation of bimetallic electrodes. Finally, we offer some perspectives on the future outlook for electrochemical CO2R.
View details for DOI 10.1021/acs.chemrev.8b00705
View details for PubMedID 31117420
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Transition Metal-Modified Exfoliated Zirconium Phosphate as an Electrocatalyst for the Oxygen Evolution Reaction
ACS APPLIED ENERGY MATERIALS
2019; 2 (5): 3561–67
View details for DOI 10.1021/acsaem.9b00299
View details for Web of Science ID 000469885300064
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Influence of Atomic Surface Structure on the Activity of Ag for the Electrochemical Reduction of CO2 to CO
ACS CATALYSIS
2019; 9 (5): 4006–14
View details for DOI 10.1021/acscatal.9b00260
View details for Web of Science ID 000467335600027
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What would it take for renewably powered electrosynthesis to displace petrochemical processes?
SCIENCE
2019; 364 (6438): 350-+
View details for DOI 10.1126/science.aav3506
View details for Web of Science ID 000465643400035
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Robust and biocompatible catalysts for efficient hydrogen-driven microbial electrosynthesis
COMMUNICATIONS CHEMISTRY
2019; 2
View details for DOI 10.1038/s42004-019-0145-0
View details for Web of Science ID 000465438600001
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Development of Molybdenum Phosphide Catalysts for Higher Alcohol Synthesis from Syngas by Exploiting Support and Promoter Effects
ENERGY TECHNOLOGY
2019; 7 (5)
View details for DOI 10.1002/ente.201801102
View details for Web of Science ID 000471344300038
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Revealing the Synergy between Oxide and Alloy Phases on the Performance of Bimetallic In-Pd Catalysts for CO2 Hydrogenation to Methanol
ACS CATALYSIS
2019; 9 (4): 3399–3412
View details for DOI 10.1021/acscatal.8b04848
View details for Web of Science ID 000464075700069
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Quantitative protocol for the electroreduction of N2 to NH3 under ambient conditions
AMER CHEMICAL SOC. 2019
View details for Web of Science ID 000478860505876
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Observing hydrogen intercalation into palladium thin films using in situ grazing incidence x-ray diffraction and x-ray reflectivity
AMER CHEMICAL SOC. 2019
View details for Web of Science ID 000478860506048
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Proton control in electrochemical ammonia synthesis
AMER CHEMICAL SOC. 2019
View details for Web of Science ID 000478860505877
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Absence of Oxidized Phases in Cu under CO Reduction Conditions
ACS ENERGY LETTERS
2019; 4 (3): 803–4
View details for DOI 10.1021/acsenergylett.9b00172
View details for Web of Science ID 000461271600027
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Electrochemical flow cell enabling operando probing of electrocatalyst surfaces by X-ray spectroscopy and diffraction.
Physical chemistry chemical physics : PCCP
2019
Abstract
The rational improvement of current and developing electrochemical technologies requires atomistic understanding of electrode-electrolyte interfaces. However, examining these interfaces under operando conditions, where performance is typically evaluated and benchmarked, remains challenging, as it necessitates incorporating an operando probe during full electrochemical operation. In this study, we describe a custom electrochemical flow cell that enables near-surface-sensitive operando investigation of planar thin-film catalysts at significant hydrogen evolution reaction (HER) rates (in excess of -100 mA cm-2) using grazing incidence X-ray methods. Grazing-incidence X-ray spectroscopy and diffraction were implemented on the same sample under identical HER conditions, demonstrating how the combined measurements track changing redox chemistry and structure of Cu thin-film catalyst surfaces as a function of electrochemical conditions. The coupling of these methods with improved mass transport and hydrodynamic control establishes a new paradigm for operando measurement design, enabling unique insights into the key fundamental processes occurring at the catalyst-electrolyte interface.
View details for DOI 10.1039/c8cp07423b
View details for PubMedID 30785434
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Molybdenum Disulfide Catalytic Coatings via Atomic Layer Deposition for Solar Hydrogen Production from Copper Gallium Diselenide Photocathodes
ACS APPLIED ENERGY MATERIALS
2019; 2 (2): 1060–66
View details for DOI 10.1021/acsaem.8b01562
View details for Web of Science ID 000459948900017
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pH effects on the electrochemical reduction of CO(2) towards C2 products on stepped copper.
Nature communications
2019; 10 (1): 32
Abstract
We present a microkinetic model for CO(2) reduction (CO(2)R) on Cu(211) towards C2 products, based on energetics estimated from an explicit solvent model. We show that the differences in both Tafel slopes and pH dependence for C1 vs C2 activity arise from differences in their multi-step mechanisms. We find the depletion in C2 products observed at high overpotential and high pH to arise from the 2nd order dependence of C-C coupling on CO coverage, which decreases due to competition from the C1 pathway. We further demonstrate that CO(2) reduction at a fixed pH yield similar activities, due to the facile kinetics for CO2 reduction to CO on Cu, which suggests C2 products to be favored for CO2R under alkaline conditions. The mechanistic insights of this work elucidate how reaction conditions can lead to significant enhancements in selectivity and activity towards higher value C2 products.
View details for PubMedID 30604776
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pH effects on the electrochemical reduction of CO(2) towards C-2 products on stepped copper
NATURE COMMUNICATIONS
2019; 10
View details for DOI 10.1038/s41467-018-07970-9
View details for Web of Science ID 000454756900009
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Systematic Investigation of Iridium-Based Bimetallic Thin Film Catalysts for the Oxygen Evolution Reaction in Acidic Media.
ACS applied materials & interfaces
2019
Abstract
Multimetallic Ir-based systems offer significant opportunities for enhanced oxygen evolution electrocatalysis by modifying the electronic and geometric properties of the active catalyst. Herein, a systematic investigation of bimetallic Ir-based thin films was performed to identify activity and stability trends across material systems for the oxygen evolution reaction (OER) in acidic media. Electron beam evaporation was used to co-deposit metallic films of Ir, IrSn2, IrCr, IrTi, and IrNi. The electrocatalytic activity of the electrochemically oxidized alloys was found to increase in the following order: IrTi < IrSn2 < Ir ∼ IrNi < IrCr. The IrCr system demonstrates two times the catalytic activity of Ir at 1.65 V versus RHE. Density functional theory calculations suggest that this enhancement is due to Cr active sites that have improved oxygen binding energetics compared to those of pure Ir oxide. This work identifies IrCr as a promising new catalyst system that facilitates reduced precious metal loadings for acid-based OER catalysis.
View details for DOI 10.1021/acsami.9b13697
View details for PubMedID 31442022
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What would it take for renewably powered electrosynthesis to displace petrochemical processes?
Science (New York, N.Y.)
2019; 364 (6438)
Abstract
Electrocatalytic transformation of carbon dioxide (CO2) and water into chemical feedstocks offers the potential to reduce carbon emissions by shifting the chemical industry away from fossil fuel dependence. We provide a technoeconomic and carbon emission analysis of possible products, offering targets that would need to be met for economically compelling industrial implementation to be achieved. We also provide a comparison of the projected costs and CO2 emissions across electrocatalytic, biocatalytic, and fossil fuel-derived production of chemical feedstocks. We find that for electrosynthesis to become competitive with fossil fuel-derived feedstocks, electrical-to-chemical conversion efficiencies need to reach at least 60%, and renewable electricity prices need to fall below 4 cents per kilowatt-hour. We discuss the possibility of combining electro- and biocatalytic processes, using sequential upgrading of CO2 as a representative case. We describe the technical challenges and economic barriers to marketable electrosynthesized chemicals.
View details for PubMedID 31023896
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Author Correction: A rigorous electrochemical ammonia synthesis protocol with quantitative isotope measurements.
Nature
2019
Abstract
An Amendment to this paper has been published and can be accessed via a link at the top of the paper.
View details for DOI 10.1038/s41586-019-1625-1
View details for PubMedID 31554972
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Nanostructuring Strategies To Increase the Photoelectrochemical Water Splitting Activity of Silicon Photocathodes
ACS APPLIED NANO MATERIALS
2019; 2 (1): 6–11
View details for DOI 10.1021/acsanm.8b01966
View details for Web of Science ID 000464491500002
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Gas-Diffusion Electrodes for Carbon Dioxide Reduction: A New Paradigm
ACS ENERGY LETTERS
2019; 4 (1): 317–24
View details for DOI 10.1021/acsenergylett.8b02035
View details for Web of Science ID 000456493100044
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Guiding Electrochemical Carbon Dioxide Reduction toward Carbonyls Using Copper Silver Thin Films with Interphase Miscibility
ACS ENERGY LETTERS
2018; 3 (12): 2947–55
View details for DOI 10.1021/acsenergylett.8b01736
View details for Web of Science ID 000453805100013
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A Highly Active Molybdenum Phosphide Catalyst for Methanol Synthesis from CO and CO2
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
2018; 57 (46): 15045–50
Abstract
Methanol is a major fuel and chemical feedstock currently produced from syngas, a CO/CO2 /H2 mixture. Herein we identify formate binding strength as a key parameter limiting the activity and stability of known catalysts for methanol synthesis in the presence of CO2 . We present a molybdenum phosphide catalyst for CO and CO2 reduction to methanol, which through a weaker interaction with formate, can improve the activity and stability of methanol synthesis catalysts in a wide range of CO/CO2 /H2 feeds.
View details for PubMedID 30134041
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Improved CO2 reduction activity towards C2+ alcohols on a tandem gold on copper electrocatalyst
NATURE CATALYSIS
2018; 1 (10): 764–71
View details for DOI 10.1038/s41929-018-0139-9
View details for Web of Science ID 000447080500011
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Quasi-2D Pd/Pt nanoclams for CO2 reduction in tandem with microbial communities
AMER CHEMICAL SOC. 2018
View details for Web of Science ID 000447600002036
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Water splitting electrocatalysis within zirconium phosphate layered inorganic nanomaterials
AMER CHEMICAL SOC. 2018
View details for Web of Science ID 000447609101149
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Metal-modified zirconium phosphate monolayers for the oxygen evolution reaction
AMER CHEMICAL SOC. 2018
View details for Web of Science ID 000447609101575
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Intercalation of rhenium bipyridine complexes with zirconium phosphate nanoparticles for energy-related reactions
AMER CHEMICAL SOC. 2018
View details for Web of Science ID 000447609101272
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Rapid flame doping of Co to WS2 for efficient hydrogen evolution
ENERGY & ENVIRONMENTAL SCIENCE
2018; 11 (8): 2270–77
View details for DOI 10.1039/c8ee01111g
View details for Web of Science ID 000442262900035
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Extending the limits of Pt/C catalysts with passivation-gas-incorporated atomic layer deposition
NATURE CATALYSIS
2018; 1 (8): 624–30
View details for DOI 10.1038/s41929-018-0118-1
View details for Web of Science ID 000446621900013
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Electrochemical Carbon Monoxide Reduction on Polycrystalline Copper: Effects of Potential, Pressure, and pH on Selectivity toward Multicarbon and Oxygenated Products
ACS CATALYSIS
2018; 8 (8): 7445–54
View details for DOI 10.1021/acscatal.8b01200
View details for Web of Science ID 000441112400064
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A Universal Platform for Fabricating Organic Electrochemical Devices
ADVANCED ELECTRONIC MATERIALS
2018; 4 (7)
View details for DOI 10.1002/aelm.201800090
View details for Web of Science ID 000437828700011
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Standards and Protocols for Data Acquisition and Reporting for Studies of the Electrochemical Reduction of Carbon Dioxide
ACS CATALYSIS
2018; 8 (7): 6560–70
View details for DOI 10.1021/acscatal.8b01340
View details for Web of Science ID 000438475100092
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Designing Boron Nitride Islands in Carbon Materials for Efficient Electrochemical Synthesis of Hydrogen Peroxide.
Journal of the American Chemical Society
2018; 140 (25): 7851–59
Abstract
Heteroatom-doped carbons have drawn increasing research interest as catalysts for various electrochemical reactions due to their unique electronic and surface structures. In particular, co-doping of carbon with boron and nitrogen has been shown to provide significant catalytic activity for oxygen reduction reaction (ORR). However, limited experimental work has been done to systematically study these materials, and much remains to be understood about the nature of the active site(s), particularly with regards to the factors underlying the activity enhancements of these boron-carbon-nitrogen (BCN) materials. Herein, we prepare several BCN materials experimentally with a facile and controlled synthesis method, and systematically study their electrochemical performance. We demonstrate the existence of h-BN domains embedded in the graphitic structures of these materials using X-ray spectroscopy. These synthesized structures yield higher activity and selectivity toward the 2e- ORR to H2O2 than structures with individual B or N doping. We further employ density functional theory calculations to understand the role of a variety of h-BN domains within the carbon lattice for the ORR and find that the interface between h-BN domains and graphene exhibits unique catalytic behavior that can preferentially drive the production of H2O2. To the best of our knowledge, this is the first example of h-BN domains in carbon identified as a novel system for the electrochemical production of H2O2.
View details for PubMedID 29874062
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The Predominance of Hydrogen Evolution on Transition Metal Sulfides and Phosphides under CO2 Reduction Conditions: An Experimental and Theoretical Study
ACS ENERGY LETTERS
2018; 3 (6): 1450–57
View details for DOI 10.1021/acsenergylett.8b00237
View details for Web of Science ID 000435159000032
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Cyclic-Voltammetry-Based Solid-State Gas Sensor for Methane and Other VOC Detection
ANALYTICAL CHEMISTRY
2018; 90 (10): 6102–8
Abstract
We present the fabrication, characterization, and testing of an electrochemical volatile organic compound (VOC) sensor operating in gaseous conditions at room temperature. It is designed to be microfabricated and to prove the sensing principle based on cyclic voltammetry (CV). It is composed of a working electrode (WE), a counter electrode (CE), a reference electrode (RE), and a Nafion solid-state electrolyte. Nafion is a polymer that conducts protons (H+) generated from redox reactions from the WE to the CE. The sensor needs to be activated prior to exposure to gases, which consists of hydrating the Nafion layer to enable its ion conduction properties. During testing, we have shown that our sensor is not only capable of detecting methane, but it can also quantify its concentration in the gas flow as well as differentiate its signal from carbon monoxide (CO). These results have been confirmed by exposing the sensor to two different concentrations of methane (50% and 10% of methane diluted in N2), as well as pure CO. Although the signal is positioned in the Hads region of Pt, because of thermodynamic reasons it cannot be directly attributed to methane oxidation into CO2. However, its consistency suggests the presence of a methane-related oxidation process that can be used for detection, identification, and quantification purposes.
View details for DOI 10.1021/acs.analchem.8b00184
View details for Web of Science ID 000432478600020
View details for PubMedID 29644861
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Copper Silver Thin Films with Metastable Miscibility for Oxygen Reduction Electrocatalysis in Alkaline Electrolytes
ACS APPLIED ENERGY MATERIALS
2018; 1 (5): 1990–99
View details for DOI 10.1021/acsaem.8b00090
View details for Web of Science ID 000458705500027
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Trends in the Catalytic Activity of Hydrogen Evolution during CO2 Electroreduction on Transition Metals
ACS CATALYSIS
2018; 8 (4): 3035–40
View details for DOI 10.1021/acscatal.7b03807
View details for Web of Science ID 000430154100048
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Nanoparticles via vapor phase condensation for energy applications
AMER CHEMICAL SOC. 2018
View details for Web of Science ID 000435537706021
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Uniform Pt/Pd bimetallic nanocrystals demonstrate platinum effect on palladium methane combustion activity and stability
AMER CHEMICAL SOC. 2018
View details for Web of Science ID 000435537702178
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Electrochemical reduction of carbon dioxide over bimetallic metal-on-copper electrocatalysts
AMER CHEMICAL SOC. 2018
View details for Web of Science ID 000435537702290
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Electrochemical cycling strategy for selective and sustainable C2H2 production from CO2 or CH4 at atmospheric pressure using H2O
AMER CHEMICAL SOC. 2018
View details for Web of Science ID 000435539900178
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alpha-Zirconium phosphate frameworks as supports for active oxygen evolution reaction electrocatalysts
AMER CHEMICAL SOC. 2018
View details for Web of Science ID 000435539903338
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High-efficiency oxygen reduction to hydrogen peroxide catalysed by oxidized carbon materials
NATURE CATALYSIS
2018; 1 (2): 156–62
View details for DOI 10.1038/s41929-017-0017-x
View details for Web of Science ID 000428621500015
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Engineering Ru@Pt Core-Shell Catalysts for Enhanced Electrochemical Oxygen Reduction Mass Activity and Stability.
Nanomaterials (Basel, Switzerland)
2018; 8 (1)
Abstract
Improving the performance of oxygen reduction reaction (ORR) electrocatalysts is essential for the commercial efficacy of many renewable energy technologies, including low temperature polymer electrolyte fuel cells (PEFCs). Herein, we report highly active and stable carbon-supported Ru@Pt core-shell nanoparticles (Ru@Pt/C) prepared by a wet chemical synthesis technique. Through rotating disc electrode testing, the Ru@Pt/C achieves an ORR Pt mass-based activity of 0.50 A mgPt-1 at 0.9 V versus the reversible hydrogen electrode (RHE), which exceeds the activity of the state-of-the-art commercial Pt/C catalyst as well as the Department of Energy 2020 PEFC electrocatalyst activity targets for transportation applications. The impact of various synthetic parameters, including Pt to Ru ratios and catalyst pretreatments (i.e., annealing) are thoroughly explored. Pt-based mass activity of all prepared Ru@Pt/C catalysts was found to exceed 0.4 mgPt-1 across the range of compositions investigated, with the maximum activity catalyst having a Ru:Pt ratio of 1:1. This optimized composition of Ru@Pt/C catalyst demonstrated remarkable stability after 30,000 accelerated durability cycles (0.6 to 1.0 V vs. RHE at 125 mV s-1), maintaining 85% of its initial mass activity. Scanning transmission electron microscopy energy dispersive spectroscopy (STEM-EDS) analysis at various stages of electrochemical testing demonstrated that the Pt shell can provide sufficient protection against the dissolution of the otherwise unstable Ru core.
View details for PubMedID 29329264
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Defective Carbon-Based Materials for the Electrochemical Synthesis of Hydrogen Peroxide
ACS SUSTAINABLE CHEMISTRY & ENGINEERING
2018; 6 (1): 311–17
View details for DOI 10.1021/acssuschemeng.7b02517
View details for Web of Science ID 000419536800034
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Impact of Nanostructuring on the Photoelectrochemical Performance of Si/Ta3N5 Nanowire Photoanodes
JOURNAL OF PHYSICAL CHEMISTRY C
2017; 121 (49): 27295–302
View details for DOI 10.1021/acs.jpcc.7b08690
View details for Web of Science ID 000418393900007
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Design and Fabrication of a Precious Metal-Free Tandem Core-Shell p(+)n Si/W-Doped BiVO4 Photoanode for Unassisted Water Splitting
ADVANCED ENERGY MATERIALS
2017; 7 (22)
View details for DOI 10.1002/aenm.201701515
View details for Web of Science ID 000417350000021
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Electrochemical CO2 Reduction over Compressively Strained CuAg Surface Alloys with Enhanced Multi-Carbon Oxygenate Selectivity
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2017; 139 (44): 15848–57
Abstract
The electrochemical reduction of carbon dioxide using renewably generated electricity offers a potential means for producing fuels and chemicals in a sustainable manner. To date, copper has been found to be the most effective catalyst for electrochemically reducing carbon dioxide to products such as methane, ethene, and ethanol. Unfortunately, the current efficiency of the process is limited by competition with the relatively facile hydrogen evolution reaction. Since multi-carbon products are more valuable precursors to chemicals and fuels than methane, there is considerable interest in modifying copper to enhance the multi-carbon product selectivity. Here, we report our investigations of electrochemical carbon dioxide reduction over CuAg bimetallic electrodes and surface alloys, which we find to be more selective for the formation of multi-carbon products than pure copper. This selectivity enhancement is a result of the selective suppression of hydrogen evolution, which occurs due to compressive strain induced by the formation of a CuAg surface alloy. Furthermore, we report that these bimetallic electrocatalysts exhibit an unusually high selectivity for the formation of multi-carbon carbonyl-containing products, which we hypothesize to be the consequence of a reduced coverage of adsorbed hydrogen and the reduced oxophilicity of the compressively strained copper. Thus, we show that promoting copper surface with small amounts of Ag is a promising means for improving the multi-carbon oxygenated product selectivity of copper during electrochemical CO2 reduction.
View details for PubMedID 28988474
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Effects of Ta3N5 Morphology and Composition on the Performance of Si-Ta3N5 Photoanodes
SOLAR RRL
2017; 1 (11)
View details for DOI 10.1002/solr.201700121
View details for Web of Science ID 000415056300002
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Systematic Structure Property Relationship Studies in Palladium Catalyzed Methane Complete Combustion
ACS CATALYSIS
2017; 7 (11): 7810–21
View details for DOI 10.1021/acscatal.7b02414
View details for Web of Science ID 000414724700052
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Highly Stable Molybdenum Disulfide Protected Silicon Photocathodes for Photoelectrochemical Water Splitting
ACS APPLIED MATERIALS & INTERFACES
2017; 9 (42): 36792–98
Abstract
Developing materials, interfaces, and devices with improved stability remains one of the key challenges in the field of photoelectrochemical water splitting. As a barrier to corrosion, molybdenum disulfide is a particularly attractive protection layer for photocathodes due to its inherent stability in acid, the low permeability of its basal planes, and the excellent hydrogen evolution reaction (HER) activity the MoS2 edge. Here, we demonstrate a stable silicon photocathode containing a protecting layer consisting of molybdenum disulfide, molybdenum silicide, and silicon oxide which operates continuously for two months. We make comparisons between this system and another molybdenum sulfide-silicon photocathode embodiment, taking both systems to catastrophic failure during photoelectrochemical stability measurements and exploring mechanisms of degradation. X-ray photoelectron spectroscopy and transmission electron microscopy provide key insights into the origins of stability.
View details for PubMedID 29035498
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Mesoporous Ruthenium/Ruthenium Oxide Thin Films: Active Electrocatalysts for the Oxygen Evolution Reaction
CHEMELECTROCHEM
2017; 4 (10): 2480–85
View details for DOI 10.1002/celc.201700334
View details for Web of Science ID 000412892600009
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Core-Shell Au@Metal-Oxide Nanoparticle Electrocatalysts for Enhanced Oxygen Evolution
NANO LETTERS
2017; 17 (10): 6040–46
Abstract
Enhanced catalysis for electrochemical oxygen evolution is essential for the efficacy of many renewable energy technologies, including water electrolyzers and metal-air batteries. Recently, Au supports have been shown to enhance the activity of many 3d transition metal-oxide thin films for the oxygen evolution reaction (OER) in alkaline media. Herein, we translate the beneficial impact of Au supports to high surface area, device-ready core-shell nanoparticles consisting of a Au-core and a metal-oxide shell (Au@MxOy where M = Ni, Co, Fe, and CoFe). Through a systematic evaluation, we establish trends in performance and illustrate the universal activity enhancement when employing the Au-core in the 3d transition metal-oxide nanoparticles. The highest activity particles, Au@CoFeOx, demonstrate an overpotential of 328 ± 3 mV over a 2 h stability test at 10 mA cm-2, illustrating that strategically coupling Au support and mixed metal-oxide effects in a core-shell nanoparticle morphology is a promising avenue to achieve device-ready, high-performance OER catalysts.
View details for PubMedID 28945433
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Machine-Learning Methods Enable Exhaustive Searches for Active Bimetallic Facets and Reveal Active Site Motifs for CO2 Reduction
ACS CATALYSIS
2017; 7 (10): 6600–6608
View details for DOI 10.1021/acscatal.7b01648
View details for Web of Science ID 000412795700022
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Investigating Catalyst-Support Interactions To Improve the Hydrogen Evolution Reaction Activity of Thiomolybdate [Mo3S13](2-) Nanoclusters
ACS CATALYSIS
2017; 7 (10): 7126–30
View details for DOI 10.1021/acscatal.7b02133
View details for Web of Science ID 000412795700082
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Understanding activity trends in electrochemical water oxidation to form hydrogen peroxide
NATURE COMMUNICATIONS
2017; 8: 701
Abstract
Electrochemical production of hydrogen peroxide (H2O2) from water oxidation could provide a very attractive route to locally produce a chemically valuable product from an abundant resource. Herein using density functional theory calculations, we predict trends in activity for water oxidation towards H2O2 evolution on four different metal oxides, i.e., WO3, SnO2, TiO2 and BiVO4. The density functional theory predicted trend for H2O2 evolution is further confirmed by our experimental measurements. Moreover, we identify that BiVO4 has the best H2O2 generation amount of those oxides and can achieve a Faraday efficiency of about 98% for H2O2 production.Producing hydrogen peroxide via electrochemical oxidation of water is an attractive route to this valuable product. Here the authors theoretically and experimentally investigate hydrogen peroxide production activity trends for a range of metal oxides and identify the optimal bias ranges for high Faraday efficiencies.
View details for PubMedID 28951571
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Understanding the Influence of [EMIM]CI on the Suppression of the Hydrogen Evolution Reaction on Transition Metal Electrodes
LANGMUIR
2017; 33 (37): 9464–71
Abstract
We have studied the influence of low concentrations (0.1 M) of the ionic liquid 1-ethyl-3-methylimidazolium chloride ([EMIM]Cl) on suppressing the hydrogen evolution reaction (HER) using polycrystalline Ag, Cu, and Fe electrodes in aqueous acidic and basic media. HER suppression is generally desired when aiming to catalyze other reactions of interests, e.g., CO2 electro-reduction. Cyclic voltammetry and chronoamperometry measurements were performed at potentials between -0.2 and -0.8 V versus the reversible hydrogen electrode (RHE) to investigate HER activity in a simulated CO2 electrolysis environment without the CO2. In an acidic electrolyte, a decrease in HER activity was observed for all three electrodes with the largest effect being that of Fe, where the HER activity was suppressed by 75% at -0.5 V versus RHE. In contrast to the effect of [EMIM]Cl in an acidic electrolyte, no HER suppression was observed in basic media. Using 1H nuclear magnetic resonance spectroscopy on the electrolyte before and after electrolysis, it was determined that [EMIM]Cl breaks down at both the working and counter electrodes under reaction conditions under both acidic and basic conditions. These results underscore the challenges in employing ionic liquids for electrochemical reactions such as CO2 reduction.
View details for PubMedID 28691827
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Polyol Synthesis of Cobalt-Copper Alloy Catalysts for Higher Alcohol Synthesis from Syngas
CATALYSIS LETTERS
2017; 147 (9): 2352–59
View details for DOI 10.1007/s10562-017-2130-5
View details for Web of Science ID 000407719300012
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High-yield ammonia synthesis via an electrochemical cycling process using N2 and H2O at atmospheric pressure
AMER CHEMICAL SOC. 2017
View details for Web of Science ID 000429556700172
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Multimodal x-ray characterization of solar fuels catalysts under operation
AMER CHEMICAL SOC. 2017
View details for Web of Science ID 000429525602065
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Water oxidation electrocatalysis by transition metals supported onto zirconium phosphate nanoparticles
AMER CHEMICAL SOC. 2017
View details for Web of Science ID 000429556700276
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Promoter Effects of Alkali Metal Cations on the Electrochemical Reduction of Carbon Dioxide
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2017; 139 (32): 11277–87
Abstract
The electrochemical reduction of CO2 is known to be influenced by the identity of the alkali metal cation in the electrolyte; however, a satisfactory explanation for this phenomenon has not been developed. Here we present the results of experimental and theoretical studies aimed at elucidating the effects of electrolyte cation size on the intrinsic activity and selectivity of metal catalysts for the reduction of CO2. Experiments were conducted under conditions where the influence of electrolyte polarization is minimal in order to show that cation size affects the intrinsic rates of formation of certain reaction products, most notably for HCOO-, C2H4, and C2H5OH over Cu(100)- and Cu(111)-oriented thin films, and for CO and HCOO- over polycrystalline Ag and Sn. Interpretation of the findings for CO2 reduction was informed by studies of the reduction of glyoxal and CO, key intermediates along the reaction pathway to final products. Density functional theory calculations show that the alkali metal cations influence the distribution of products formed as a consequence of electrostatic interactions between solvated cations present at the outer Helmholtz plane and adsorbed species having large dipole moments. The observed trends in activity with cation size are attributed to an increase in the concentration of cations at the outer Helmholtz plane with increasing cation size.
View details for PubMedID 28738673
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Effects of Gold Substrates on the Intrinsic and Extrinsic Activity of High-Loading Nickel-Based Oxyhydroxide Oxygen Evolution Catalysts
ACS CATALYSIS
2017; 7 (8): 5399–5409
View details for DOI 10.1021/acscatal.7b01070
View details for Web of Science ID 000407309100055
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Ammonia synthesis from N-2 and H2O using a lithium cycling electrification strategy at atmospheric pressure
ENERGY & ENVIRONMENTAL SCIENCE
2017; 10 (7): 1621–30
View details for DOI 10.1039/c7ee01126a
View details for Web of Science ID 000405279900010
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Uniform Pt/Pd Bimetallic Nanocrystals Demonstrate Platinum Effect on Palladium Methane Combustion Activity and Stability
ACS CATALYSIS
2017; 7 (7): 4372–80
View details for DOI 10.1021/acscatal.7b00393
View details for Web of Science ID 000405360800018
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Understanding Selectivity for the Electrochemical Reduction of Carbon Dioxide to Formic Acid and Carbon Monoxide on Metal Electrodes
ACS CATALYSIS
2017; 7 (7): 4822–27
View details for DOI 10.1021/acscatal.7b00687
View details for Web of Science ID 000405360800075
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reduction on Au surfaces: mechanistic aspects regarding the formation of major and minor products.
Physical chemistry chemical physics : PCCP
2017
Abstract
In the future, industrial CO2 electroreduction using renewable energy sources could be a sustainable means to convert CO2 and water into commodity chemicals at room temperature and atmospheric pressure. This study focuses on the electrocatalytic reduction of CO2 on polycrystalline Au surfaces, which have high activity and selectivity for CO evolution. We explore the catalytic behavior of polycrystalline Au surfaces by coupling potentiostatic CO2 electrolysis experiments in an aqueous bicarbonate solution with high sensitivity product detection methods. We observed the production of methanol, in addition to detecting the known products of CO2 electroreduction on Au: CO, H2 and formate. We suggest a mechanism that explains Au's evolution of methanol. Specifically, the Au surface does not favor C-O scission, and thus is more selective towards methanol than methane. These insights could aid in the design of electrocatalysts that are selective for CO2 electroreduction to oxygenates over hydrocarbons.
View details for DOI 10.1039/c7cp02855e
View details for PubMedID 28585950
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: Controlling selectivity toward oxygenates and hydrocarbons.
Proceedings of the National Academy of Sciences of the United States of America
2017; 114 (23): 5918-5923
Abstract
In this study we control the surface structure of Cu thin-film catalysts to probe the relationship between active sites and catalytic activity for the electroreduction of CO2 to fuels and chemicals. Here, we report physical vapor deposition of Cu thin films on large-format (∼6 cm(2)) single-crystal substrates, and confirm epitaxial growth in the <100>, <111>, and <751> orientations using X-ray pole figures. To understand the relationship between the bulk and surface structures, in situ electrochemical scanning tunneling microscopy was conducted on Cu(100), (111), and (751) thin films. The studies revealed that Cu(100) and (111) have surface adlattices that are identical to the bulk structure, and that Cu(751) has a heterogeneous kinked surface with (110) terraces that is closely related to the bulk structure. Electrochemical CO2 reduction testing showed that whereas both Cu(100) and (751) thin films are more active and selective for C-C coupling than Cu(111), Cu(751) is the most selective for >2e(-) oxygenate formation at low overpotentials. Our results demonstrate that epitaxy can be used to grow single-crystal analogous materials as large-format electrodes that provide insights on controlling electrocatalytic activity and selectivity for this reaction.
View details for DOI 10.1073/pnas.1618935114
View details for PubMedID 28533377
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Carbon Dioxide Electroreduction using a Silver-Zinc Alloy
ENERGY TECHNOLOGY
2017; 5 (6): 955–61
View details for DOI 10.1002/ente.201700087
View details for Web of Science ID 000403458600020
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Transition Metal-Modified Zirconium Phosphate Electrocatalysts for the Oxygen Evolution Reaction
CATALYSTS
2017; 7 (5)
View details for DOI 10.3390/catal7050132
View details for Web of Science ID 000404099100007
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Enhanced electrocatalysis for polymer electrolyte membrane fuel cells and electrolyzers
AMER CHEMICAL SOC. 2017
View details for Web of Science ID 000430568502160
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Fundamental understanding of defective carbon-based materials for electrochemical synthesis of hydrogen peroxide
AMER CHEMICAL SOC. 2017
View details for Web of Science ID 000430568502299
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Phase segregated copper silver thin films as model catalysts for electrochemical oxygen reduction in alkaline electrolytes
AMER CHEMICAL SOC. 2017
View details for Web of Science ID 000430568502161
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Vapor phase deposition of silver-copper nanoparticles for the oxygen reduction reaction
AMER CHEMICAL SOC. 2017
View details for Web of Science ID 000430568502463
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Surface structure engineering of Cu thin films for electrochemical CO2 reduction
AMER CHEMICAL SOC. 2017
View details for Web of Science ID 000430568502203
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Screening of binary alloy thin films for electrochemical CO2/CO reduction
AMER CHEMICAL SOC. 2017
View details for Web of Science ID 000430568502460
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Electrochemical generation of H2O2: Development of a reactor with carbon catalysts for portable low-cost water purification
AMER CHEMICAL SOC. 2017
View details for Web of Science ID 000430569100599
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Operando electrochemical grazing incidence x-ray absorption and diffraction for the CO2 reduction reaction
AMER CHEMICAL SOC. 2017
View details for Web of Science ID 000430568502328
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Molybdenum disulfide as a protection layer and catalyst for gallium indium phosphide solar water splitting photocathodes
AMER CHEMICAL SOC. 2017
View details for Web of Science ID 000430568502396
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Cobalt-copper nanoparticle catalysts for higher alcohols synthesis prepared by water-in-oil microemulsion
AMER CHEMICAL SOC. 2017
View details for Web of Science ID 000430568502171
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Exploring electrocatalytic N2 activation under mild synthetic conditions
AMER CHEMICAL SOC. 2017
View details for Web of Science ID 000430569103422
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Developing catalysts and methods for low temperature electrochemical oxidation of methane
AMER CHEMICAL SOC. 2017
View details for Web of Science ID 000430569100192
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Au@MxOy core-shell nanoparticles as catalysts for the oxygen evolution reaction
AMER CHEMICAL SOC. 2017
View details for Web of Science ID 000430568502259
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Higher alcohol synthesis via Fischer-Tropsch metal surface modification of MoP catalyst
AMER CHEMICAL SOC. 2017
View details for Web of Science ID 000430568502423
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Electrocatalyst design and development for the Oxygen Evolution Reaction (OER) and the electroreduction of CO2
AMER CHEMICAL SOC. 2017
View details for Web of Science ID 000430568500582
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Transition metal phosphide catalysts for methanol synthesis from CO and CO2
AMER CHEMICAL SOC. 2017
View details for Web of Science ID 000430568502376
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Effects of alkylamine electrolyte additives on activity and selectivity in electrochemical carbon dioxide reduction
AMER CHEMICAL SOC. 2017
View details for Web of Science ID 000430569100181
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Ionic compounds for electrochemical reduction of carbon dioxide
AMER CHEMICAL SOC. 2017
View details for Web of Science ID 000430568502505
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Metal modified zirconium hydrogen phosphate for the oxygen evolution reaction
AMER CHEMICAL SOC. 2017
View details for Web of Science ID 000430568502450
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Exceptionally stable molybdenum disulfide protection schemes for silicon photocathodes
AMER CHEMICAL SOC. 2017
View details for Web of Science ID 000430568502317
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Activation and stabilization of copper chalcopyrite light absorbers for photoelectrochemical hydrogen production
AMER CHEMICAL SOC. 2017
View details for Web of Science ID 000430569100202
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Nanostructured non-precious metal silicon photocathodes for solar water splitting
AMER CHEMICAL SOC. 2017
View details for Web of Science ID 000430568502401
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Electro-thermochemical cycling process for high-yield ammonia synthesis from N2 and H2O at atmospheric pressure
AMER CHEMICAL SOC. 2017
View details for Web of Science ID 000430569104027
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Nanostructured tandem Si-Ta3N5 photoanodes for solar water splitting
AMER CHEMICAL SOC. 2017
View details for Web of Science ID 000430568502678
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Integrated electrochemical-biological systems for the production of fuels and chemicals from CO2
AMER CHEMICAL SOC. 2017
View details for Web of Science ID 000430569100172
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High-performance oxygen reduction and evolution carbon catalysis: From mechanistic studies to device integration
NANO RESEARCH
2017; 10 (4): 1163-1177
View details for DOI 10.1007/s12274-016-1347-8
View details for Web of Science ID 000398382300005
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Development of a reactor with carbon catalysts for modular-scale, low-cost electrochemical generation of H2O2
REACTION CHEMISTRY & ENGINEERING
2017; 2 (2): 239–45
View details for DOI 10.1039/c6re00195e
View details for Web of Science ID 000403324600016
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Operando investigation of Au-MnOx thin films with improved activity for the oxygen evolution reaction
ELECTROCHIMICA ACTA
2017; 230: 22-28
View details for DOI 10.1016/j.electacta.2017.01.085
View details for Web of Science ID 000395599900003
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Combining theory and experiment in electrocatalysis: Insights into materials design
SCIENCE
2017; 355 (6321): 146-?
Abstract
Electrocatalysis plays a central role in clean energy conversion, enabling a number of sustainable processes for future technologies. This review discusses design strategies for state-of-the-art heterogeneous electrocatalysts and associated materials for several different electrochemical transformations involving water, hydrogen, and oxygen, using theory as a means to rationalize catalyst performance. By examining the common principles that govern catalysis for different electrochemical reactions, we describe a systematic framework that clarifies trends in catalyzing these reactions, serving as a guide to new catalyst development while highlighting key gaps that need to be addressed. We conclude by extending this framework to emerging clean energy reactions such as hydrogen peroxide production, carbon dioxide reduction, and nitrogen reduction, where the development of improved catalysts could allow for the sustainable production of a broad range of fuels and chemicals.
View details for DOI 10.1126/science.aad4998
View details for Web of Science ID 000391743700032
View details for PubMedID 28082532
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Materials for solar fuels and chemicals
NATURE MATERIALS
2017; 16 (1): 70-81
Abstract
The conversion of sunlight into fuels and chemicals is an attractive prospect for the storage of renewable energy, and photoelectrocatalytic technologies represent a pathway by which solar fuels might be realized. However, there are numerous scientific challenges in developing these technologies. These include finding suitable materials for the absorption of incident photons, developing more efficient catalysts for both water splitting and the production of fuels, and understanding how interfaces between catalysts, photoabsorbers and electrolytes can be designed to minimize losses and resist degradation. In this Review, we highlight recent milestones in these areas and some key scientific challenges remaining between the current state of the art and a technology that can effectively convert sunlight into fuels and chemicals.
View details for DOI 10.1038/NMAT4778
View details for Web of Science ID 000391343300015
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Electrochemical Ammonia Synthesis-The Selectivity Challenge
ACS CATALYSIS
2017; 7 (1): 706-709
View details for DOI 10.1021/acscatal.6b03035
View details for Web of Science ID 000391783200078
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Top-down fabrication of fluorine-doped tin oxide nanopillar substrates for solar water splitting
RSC ADVANCES
2017; 7 (45): 28350–57
View details for DOI 10.1039/c7ra02937c
View details for Web of Science ID 000402999300047
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Active and Stable Ir@Pt Core-Shell Catalysts for Electrochemical Oxygen Reduction
ACS ENERGY LETTERS
2017; 2 (1): 244-249
View details for DOI 10.1021/acsenergylett.6b00585
View details for Web of Science ID 000392260400034
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Materials for solar fuels and chemicals.
Nature materials
2016; 16 (1): 70-81
Abstract
The conversion of sunlight into fuels and chemicals is an attractive prospect for the storage of renewable energy, and photoelectrocatalytic technologies represent a pathway by which solar fuels might be realized. However, there are numerous scientific challenges in developing these technologies. These include finding suitable materials for the absorption of incident photons, developing more efficient catalysts for both water splitting and the production of fuels, and understanding how interfaces between catalysts, photoabsorbers and electrolytes can be designed to minimize losses and resist degradation. In this Review, we highlight recent milestones in these areas and some key scientific challenges remaining between the current state of the art and a technology that can effectively convert sunlight into fuels and chemicals.
View details for DOI 10.1038/nmat4778
View details for PubMedID 27994241
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Tandem Core-Shell Si-Ta3N5 Photoanodes for Photoelectrochemical Water Splitting
NANO LETTERS
2016; 16 (12): 7565-7572
Abstract
Nanostructured core-shell Si-Ta3N5 photoanodes were designed and synthesized to overcome charge transport limitations of Ta3N5 for photoelectrochemical water splitting. The core-shell devices were fabricated by atomic layer deposition of amorphous Ta2O5 onto nanostructured Si and subsequent nitridation to crystalline Ta3N5. Nanostructuring with a thin shell of Ta3N5 results in a 10-fold improvement in photocurrent compared to a planar device of the same thickness. In examining thickness dependence of the Ta3N5 shell from 10 to 70 nm, superior photocurrent and absorbed-photon-to-current efficiencies are obtained from the thinner Ta3N5 shells, indicating minority carrier diffusion lengths on the order of tens of nanometers. The fabrication of a heterostructure based on a semiconducting, n-type Si core produced a tandem photoanode with a photocurrent onset shifted to lower potentials by 200 mV. CoTiOx and NiOx water oxidation cocatalysts were deposited onto the Si-Ta3N5 to yield active photoanodes that with NiOx retained 50-60% of their maximum photocurrent after 24 h chronoamperometry experiments and are thus among the most stable Ta3N5 photoanodes reported to date.
View details for DOI 10.1021/acs.nanolett.6b03408
View details for Web of Science ID 000389963200037
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Microfabricated electrochemical gas sensor
MICRO & NANO LETTERS
2016; 11 (12): 798-802
View details for DOI 10.1049/mnl.2016.0364
View details for Web of Science ID 000389323100003
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Mesoporous platinum nickel thin films with double gyroid morphology for the oxygen reduction reaction
NANO ENERGY
2016; 29: 243-248
View details for DOI 10.1016/j.nanoen.2016.05.005
View details for Web of Science ID 000389624100017
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Solar water splitting by photovoltaic-electrolysis with a solar-to-hydrogen efficiency over 30.
Nature communications
2016; 7: 13237-?
Abstract
Hydrogen production via electrochemical water splitting is a promising approach for storing solar energy. For this technology to be economically competitive, it is critical to develop water splitting systems with high solar-to-hydrogen (STH) efficiencies. Here we report a photovoltaic-electrolysis system with the highest STH efficiency for any water splitting technology to date, to the best of our knowledge. Our system consists of two polymer electrolyte membrane electrolysers in series with one InGaP/GaAs/GaInNAsSb triple-junction solar cell, which produces a large-enough voltage to drive both electrolysers with no additional energy input. The solar concentration is adjusted such that the maximum power point of the photovoltaic is well matched to the operating capacity of the electrolysers to optimize the system efficiency. The system achieves a 48-h average STH efficiency of 30%. These results demonstrate the potential of photovoltaic-electrolysis systems for cost-effective solar energy storage.
View details for DOI 10.1038/ncomms13237
View details for PubMedID 27796309
View details for PubMedCentralID PMC5095559
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A highly active and stable IrOx/SrIrO3 catalyst for the oxygen evolution reaction
SCIENCE
2016; 353 (6303): 1011-1014
Abstract
Oxygen electrochemistry plays a key role in renewable energy technologies such as fuel cells and electrolyzers, but the slow kinetics of the oxygen evolution reaction (OER) limit the performance and commercialization of such devices. Here we report an iridium oxide/strontium iridium oxide (IrOx/SrIrO3) catalyst formed during electrochemical testing by strontium leaching from surface layers of thin films of SrIrO3 This catalyst has demonstrated specific activity at 10 milliamps per square centimeter of oxide catalyst (OER current normalized to catalyst surface area), with only 270 to 290 millivolts of overpotential for 30 hours of continuous testing in acidic electrolyte. Density functional theory calculations suggest the formation of highly active surface layers during strontium leaching with IrO3 or anatase IrO2 motifs. The IrOx/SrIrO3 catalyst outperforms known IrOx and ruthenium oxide (RuOx) systems, the only other OER catalysts that have reasonable activity in acidic electrolyte.
View details for DOI 10.1126/science.aaf5050
View details for Web of Science ID 000382558900034
View details for PubMedID 27701108
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Two-Dimensional Molybdenum Carbide (MXene) as an Efficient Electrocatalyst for Hydrogen Evolution
ACS ENERGY LETTERS
2016; 1 (3): 589-594
View details for DOI 10.1021/acsenergylett.6b00247
View details for Web of Science ID 000389617900017
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Elucidating the electronic structure of supported gold nanoparticles and its relevance to catalysis by means of hard X-ray photoelectron spectroscopy
SURFACE SCIENCE
2016; 650: 24-33
View details for DOI 10.1016/j.susc.2015.12.025
View details for Web of Science ID 000377837800006
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Molybdenum Disulfide as a Protection Layer and Catalyst for Gallium Indium Phosphide Solar Water Splitting Photocathodes
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
2016; 7 (11): 2044-2049
Abstract
Gallium indium phosphide (GaInP2) is a semiconductor with promising optical and electronic properties for solar water splitting, but its surface stability is problematic as it undergoes significant chemical and electrochemical corrosion in aqueous electrolytes. Molybdenum disulfide (MoS2) nanomaterials are promising to both protect GaInP2 and to improve catalysis because MoS2 is resistant to corrosion and also possesses high activity for the hydrogen evolution reaction (HER). In this work, we demonstrate that GaInP2 photocathodes coated with thin MoS2 surface protecting layers exhibit excellent activity and stability for solar hydrogen production, with no loss in performance (photocurrent onset potential, fill factor, and light-limited current density) after 60 h of operation. This represents a 500-fold increase in stability compared to bare p-GaInP2 samples tested in identical conditions.
View details for DOI 10.1021/acs.jpclett.6b00563
View details for Web of Science ID 000377239200018
View details for PubMedID 27196435
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Gold-supported cerium-doped NiOx catalysts for water oxidation
NATURE ENERGY
2016; 1
View details for DOI 10.1038/NENERGY.2016.53
View details for Web of Science ID 000394119200002
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Improving the Photoelectrochemical Performance of Hematite by Employing a High Surface Area Scaffold and Engineering Solid-Solid Interfaces
ADVANCED MATERIALS INTERFACES
2016; 3 (7)
View details for DOI 10.1002/admi.201500626
View details for Web of Science ID 000374153000005
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Band Edge Engineering of Oxide Photoanodes for Photoelectrochemical Water Splitting: Integration of Subsurface Dipoles with Atomic-Scale Control
ADVANCED ENERGY MATERIALS
2016; 6 (7)
View details for DOI 10.1002/aenm.201502154
View details for Web of Science ID 000374704200003
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Design and synthesis of nitrogen-doped hierarchical carbon for selective carbon capture and electrocatalysis
AMER CHEMICAL SOC. 2016
View details for Web of Science ID 000431905706765
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Hydrogen generation and fuel cells: Current status, research challenges, and future prospects
AMER CHEMICAL SOC. 2016
View details for Web of Science ID 000431905700062
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Tuning Composition and Activity of Cobalt Titanium Oxide Catalysts for the Oxygen Evolution Reaction
ELECTROCHIMICA ACTA
2016; 193: 240-245
View details for DOI 10.1016/j.electacta.2016.01.200
View details for Web of Science ID 000371471900030
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Engineering Cobalt Phosphide (CoP) Thin Film Catalysts for Enhanced Hydrogen Evolution Activity on Silicon Photocathodes
ADVANCED ENERGY MATERIALS
2016; 6 (4)
View details for DOI 10.1002/aenm.201501758
View details for Web of Science ID 000371147000009
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Chemical and Phase Evolution of Amorphous Molybdenum Sulfide Catalysts for Electrochemical Hydrogen Production.
ACS nano
2016; 10 (1): 624-632
Abstract
Amorphous MoSx is a highly active, earth-abundant catalyst for the electrochemical hydrogen evolution reaction. Previous studies have revealed that this material initially has a composition of MoS3, but after electrochemical activation, the surface is reduced to form an active phase resembling MoS2 in composition and chemical state. However, structural changes in the MoSx catalyst and the mechanism of the activation process remain poorly understood. In this study, we employ transmission electron microscopy (TEM) to image amorphous MoSx catalysts activated under two hydrogen-rich conditions: ex situ in an electrochemical cell and in situ in an environmental TEM. For the first time, we directly observe the formation of crystalline domains in the MoSx catalyst after both activation procedures as well as spatially localized changes in the chemical state detected via electron energy loss spectroscopy. Using density functional theory calculations, we investigate the mechanisms for this phase transformation and find that the presence of hydrogen is critical for enabling the restructuring process. Our results suggest that the surface of the amorphous MoSx catalyst is dynamic: while the initial catalyst activation forms the primary active surface of amorphous MoS2, continued transformation to the crystalline phase during electrochemical operation could contribute to catalyst deactivation. These results have important implications for the application of this highly active electrocatalyst for sustainable H2 generation.
View details for DOI 10.1021/acsnano.5b05652
View details for PubMedID 26624225
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Benchmarking nanoparticulate metal oxide electrocatalysts for the alkaline water oxidation reaction
JOURNAL OF MATERIALS CHEMISTRY A
2016; 4 (8): 3068-3076
View details for DOI 10.1039/c5ta07586f
View details for Web of Science ID 000371077300034
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Electrooxidation of Alcohols with Electrode-Supported Transfer Hydrogenation Catalysts
ACS CATALYSIS
2015; 5 (12): 7343-7349
View details for DOI 10.1021/acscatal.5b01830
View details for Web of Science ID 000366153300034
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Enhancement Effect of Noble Metals on Manganese Oxide for the Oxygen Evolution Reaction
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
2015; 6 (20): 4178-4183
Abstract
Developing improved catalysts for the oxygen evolution reaction (OER) is key to the advancement of a number of renewable energy technologies, including solar fuels production and metal air batteries. In this study, we employ electrochemical methods and synchrotron techniques to systematically investigate interactions between metal oxides and noble metals that lead to enhanced OER catalysis for water oxidation. In particular, we synthesize porous MnOx films together with nanoparticles of Au, Pd, Pt, or Ag and observe significant improvement in activity for the combined catalysts. Soft X-ray absorption spectroscopy (XAS) shows that increased activity correlates with increased Mn oxidation states to 4+ under OER conditions compared to bare MnOx, which exhibits minimal OER current and remains in a 3+ oxidation state. Thickness studies of bare MnOx films and of MnOx films deposited on Au nanoparticles reveal trends suggesting that the enhancement in activity arises from interfacial sites between Au and MnOx.
View details for DOI 10.1021/acs.jpclett.5b01928
View details for Web of Science ID 000363083900031
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Enhancement Effect of Noble Metals on Manganese Oxide for the Oxygen Evolution Reaction.
The journal of physical chemistry letters
2015; 6 (20): 4178-83
Abstract
Developing improved catalysts for the oxygen evolution reaction (OER) is key to the advancement of a number of renewable energy technologies, including solar fuels production and metal air batteries. In this study, we employ electrochemical methods and synchrotron techniques to systematically investigate interactions between metal oxides and noble metals that lead to enhanced OER catalysis for water oxidation. In particular, we synthesize porous MnOx films together with nanoparticles of Au, Pd, Pt, or Ag and observe significant improvement in activity for the combined catalysts. Soft X-ray absorption spectroscopy (XAS) shows that increased activity correlates with increased Mn oxidation states to 4+ under OER conditions compared to bare MnOx, which exhibits minimal OER current and remains in a 3+ oxidation state. Thickness studies of bare MnOx films and of MnOx films deposited on Au nanoparticles reveal trends suggesting that the enhancement in activity arises from interfacial sites between Au and MnOx.
View details for DOI 10.1021/acs.jpclett.5b01928
View details for PubMedID 26722794
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Polymer Electrolyte Membrane Electrolyzers Utilizing Non-precious Mo-based Hydrogen Evolution Catalysts.
ChemSusChem
2015; 8 (20): 3512-3519
Abstract
The development of low-cost hydrogen evolution reaction (HER) catalysts that can be readily integrated into electrolyzers is critical if H2 from renewable electricity-powered electrolysis is to compete cost effectively with steam reforming. Herein, we report three distinct earth-abundant Mo-based catalysts, namely those based on MoSx , [Mo3 S13 ](2-) nanoclusters, and sulfur-doped Mo phosphide (MoP|S), loaded onto carbon supports. The catalysts were synthesized through facile impregnation-sulfidization routes specifically designed for catalyst-device compatibility. Fundamental electrochemical studies demonstrate the excellent HER activity and stability of the Mo-sulfide based catalysts in an acidic environment, and the resulting polymer electrolyte membrane (PEM) electrolyzers that integrate these catalysts exhibit high efficiency and durability. This work is an important step towards the goal of replacing Pt with earth-abundant catalysts for the HER in commercial PEM electrolyzers.
View details for DOI 10.1002/cssc.201500334
View details for PubMedID 26377877
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Mapping Photoelectrochemical Current Distribution at Nanoscale Dimensions on Morphologically Controlled BiVO4
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
2015; 6 (18): 3702-3707
Abstract
We develop a method that can be used to qualitatively map photocurrent on photoelectrode surfaces, and show its utility for morphologically controlled W-doped BiVO4. The method is based on the deliberate photoinduced sintering of Au NPs, a photon-driven process that indicates oxidation with nanoscale-resolution. This strategy allows us to identify the active regions on W-doped BiVO4 photoelectrodes, and we observe a strong dependence of photoactivity on the electrode morphology, controlled by varying the relative humidity during the sol-gel fabrication process. We find that photoelectrode morphologies that exhibit the most evenly distributed Au sintering are those that yield the highest photoelectrochemical (PEC) activity. Understanding the correlation between electrode morphology and PEC activity is essential for designing structured semiconductors for PEC water splitting.
View details for DOI 10.1021/acs.jpclett.5b01587
View details for Web of Science ID 000361858800030
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Mapping Photoelectrochemical Current Distribution at Nanoscale Dimensions on Morphologically Controlled BiVO4.
The journal of physical chemistry letters
2015; 6 (18): 3702-7
Abstract
We develop a method that can be used to qualitatively map photocurrent on photoelectrode surfaces, and show its utility for morphologically controlled W-doped BiVO4. The method is based on the deliberate photoinduced sintering of Au NPs, a photon-driven process that indicates oxidation with nanoscale-resolution. This strategy allows us to identify the active regions on W-doped BiVO4 photoelectrodes, and we observe a strong dependence of photoactivity on the electrode morphology, controlled by varying the relative humidity during the sol-gel fabrication process. We find that photoelectrode morphologies that exhibit the most evenly distributed Au sintering are those that yield the highest photoelectrochemical (PEC) activity. Understanding the correlation between electrode morphology and PEC activity is essential for designing structured semiconductors for PEC water splitting.
View details for DOI 10.1021/acs.jpclett.5b01587
View details for PubMedID 26713778
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Platinum and hybrid polyaniline-platinum surfaces for the electrocatalytic reduction of CO2
MRS COMMUNICATIONS
2015; 5 (2): 319-325
View details for DOI 10.1557/mrc.2015.30
View details for Web of Science ID 000358147300024
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Benchmarking Hydrogen Evolving Reaction and Oxygen Evolving Reaction Electrocatalysts for Solar Water Splitting Devices
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2015; 137 (13): 4347-4357
Abstract
Objective comparisons of electrocatalyst activity and stability using standard methods under identical conditions are necessary to evaluate the viability of existing electrocatalysts for integration into solar-fuel devices as well as to help inform the development of new catalytic systems. Herein, we use a standard protocol as a primary screen for evaluating the activity, short-term (2 h) stability, and electrochemically active surface area (ECSA) of 18 electrocatalysts for the hydrogen evolution reaction (HER) and 26 electrocatalysts for the oxygen evolution reaction (OER) under conditions relevant to an integrated solar water-splitting device in aqueous acidic or alkaline solution. Our primary figure of merit is the overpotential necessary to achieve a magnitude current density of 10 mA cm(-2) per geometric area, the approximate current density expected for a 10% efficient solar-to-fuels conversion device under 1 sun illumination. The specific activity per ECSA of each material is also reported. Among HER catalysts, several could operate at 10 mA cm(-2) with overpotentials <0.1 V in acidic and/or alkaline solutions. Among OER catalysts in acidic solution, no non-noble metal based materials showed promising activity and stability, whereas in alkaline solution many OER catalysts performed with similar activity achieving 10 mA cm(-2) current densities at overpotentials of ~0.33-0.5 V. Most OER catalysts showed comparable or better specific activity per ECSA when compared to Ir and Ru catalysts in alkaline solutions, while most HER catalysts showed much lower specific activity than Pt in both acidic and alkaline solutions. For select catalysts, additional secondary screening measurements were conducted including Faradaic efficiency and extended stability measurements.
View details for DOI 10.1021/ja510442p
View details for Web of Science ID 000352752000019
View details for PubMedID 25668483
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Semiconductor materials for efficient photoelectrochemical water splitting: The PEC working group
AMER CHEMICAL SOC. 2015
View details for Web of Science ID 000411183304449
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Applications of ALD MnO to electrochemical water splitting
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
2015; 17 (21): 14003-14011
Abstract
Atomic layer deposition (ALD) is an attractive method to deposit uniform catalytic films onto high surface area electrodes. One interesting material for ALD synthesis is MnOx, a promising earth-abundant catalyst for the oxygen evolution reaction (OER). It has previously been shown that catalysts beginning as MnO synthesized using ALD on smooth glassy carbon (s-GC) electrodes and Mn2O3 obtained upon annealing MnO on s-GC are active OER catalysts. Here, we use ALD to deposit MnO on high surface area GC (HSA-GC) substrates, forming an active catalyst on a geometric surface area basis. We then characterize three types of catalysts, HSA-GC MnO, s-GC MnO, and annealed MnO (Mn2O3), using cyclic voltammetry (CV), scanning electron microscopy (SEM), and ex situ X-ray absorption spectroscopy (XAS). We show that under OER conditions, all three catalysts oxidize to similar surface states with a mixture of Mn(3+)/Mn(4+) and that MnOx surface area effects can account for the observed differences in the catalytic activity. We also demonstrate the need for a high surface area support for high OER activity on a geometric basis.
View details for DOI 10.1039/c5cp00843c
View details for Web of Science ID 000354946200025
View details for PubMedID 25946998
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Designing an improved transition metal phosphide catalyst for hydrogen evolution using experimental and theoretical trends
ENERGY & ENVIRONMENTAL SCIENCE
2015; 8 (10): 3022-3029
View details for DOI 10.1039/c5ee02179k
View details for Web of Science ID 000362351700024
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CoTiOx Catalysts for the Oxygen Evolution Reaction
JOURNAL OF THE ELECTROCHEMICAL SOCIETY
2015; 162 (12): H841-H846
View details for DOI 10.1149/2.0931510jes
View details for Web of Science ID 000363600300070
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Simultaneous detection of electronic structure changes from two elements of a bifunctional catalyst using wavelength-dispersive X-ray emission spectroscopy and in situ electrochemistry
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
2015; 17 (14): 8901-8912
Abstract
Multielectron catalytic reactions, such as water oxidation, nitrogen reduction, or hydrogen production in enzymes and inorganic catalysts often involve multimetallic clusters. In these systems, the reaction takes place between metals or metals and ligands to facilitate charge transfer, bond formation/breaking, substrate binding, and release of products. In this study, we present a method to detect X-ray emission signals from multiple elements simultaneously, which allows for the study of charge transfer and the sequential chemistry occurring between elements. Kβ X-ray emission spectroscopy (XES) probes charge and spin states of metals as well as their ligand environment. A wavelength-dispersive spectrometer based on the von Hamos geometry was used to disperse Kβ signals of multiple elements onto a position detector, enabling an XES spectrum to be measured in a single-shot mode. This overcomes the scanning needs of the scanning spectrometers, providing data free from temporal and normalization errors and therefore ideal to follow sequential chemistry at multiple sites. We have applied this method to study MnOx-based bifunctional electrocatalysts for the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR). In particular, we investigated the effects of adding a secondary element, Ni, to form MnNiOx and its impact on the chemical states and catalytic activity, by tracking the redox characteristics of each element upon sweeping the electrode potential. The detection scheme we describe here is general and can be applied to time-resolved studies of materials consisting of multiple elements, to follow the dynamics of catalytic and electron transfer reactions.
View details for DOI 10.1039/c5cp01023c
View details for Web of Science ID 000351933600043
View details for PubMedID 25747045
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Synthesis of thin film AuPd alloys and their investigation for electrocatalytic CO2 reduction
JOURNAL OF MATERIALS CHEMISTRY A
2015; 3 (40): 20185-20194
View details for DOI 10.1039/c5ta04863j
View details for Web of Science ID 000363151000021
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Designing Active and Stable Silicon Photocathodes for Solar Hydrogen Production Using Molybdenum Sulfide Nanomaterials
ADVANCED ENERGY MATERIALS
2014; 4 (18)
View details for DOI 10.1002/aenm.201400739
View details for Web of Science ID 000346983100007
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Molybdenum Phosphosulfide: An Active, Acid-Stable, Earth-Abundant Catalyst for the Hydrogen Evolution Reaction
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
2014; 53 (52): 14433-14437
Abstract
Introducing sulfur into the surface of molybdenum phosphide (MoP) produces a molybdenum phosphosulfide (MoP|S) catalyst with superb activity and stability for the hydrogen evolution reaction (HER) in acidic environments. The MoP|S catalyst reported herein exhibits one of the highest HER activities of any non-noble-metal electrocatalyst investigated in strong acid, while remaining perfectly stable in accelerated durability testing. Whereas mixed-metal alloy catalysts are well-known, MoP|S represents a more uncommon mixed-anion catalyst where synergistic effects between sulfur and phosphorus produce a high-surface-area electrode that is more active than those based on either the pure sulfide or the pure phosphide. The extraordinarily high activity and stability of this catalyst open up avenues to replace platinum in technologies relevant to renewable energies, such as proton exchange membrane (PEM) electrolyzers and solar photoelectrochemical (PEC) water-splitting cells.
View details for DOI 10.1002/anie.201408222
View details for Web of Science ID 000346485800022
View details for PubMedID 25359678
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Operando Characterization of an Amorphous Molybdenum Sulfide Nanoparticle Catalyst during the Hydrogen Evolution Reaction
JOURNAL OF PHYSICAL CHEMISTRY C
2014; 118 (50): 29252-29259
View details for DOI 10.1021/jp505394e
View details for Web of Science ID 000346759300037
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Catalyzing the Hydrogen Evolution Reaction (HER) with Molybdenum Sulfide Nanonnaterials
ACS CATALYSIS
2014; 4 (11): 3957-3971
View details for DOI 10.1021/cs500923c
View details for Web of Science ID 000344639300019
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Substrate Selection for Fundamental Studies of Electrocatalysts and Photoelectrodes: Inert Potential Windows in Acidic, Neutral, and Basic Electrolyte
PLOS ONE
2014; 9 (10)
Abstract
The selection of an appropriate substrate is an important initial step for many studies of electrochemically active materials. In order to help researchers with the substrate selection process, we employ a consistent experimental methodology to evaluate the electrochemical reactivity and stability of seven potential substrate materials for electrocatalyst and photoelectrode evaluation. Using cyclic voltammetry with a progressively increased scan range, we characterize three transparent conducting oxides (indium tin oxide, fluorine-doped tin oxide, and aluminum-doped zinc oxide) and four opaque conductors (gold, stainless steel 304, glassy carbon, and highly oriented pyrolytic graphite) in three different electrolytes (sulfuric acid, sodium acetate, and sodium hydroxide). We determine the inert potential window for each substrate/electrolyte combination and make recommendations about which materials may be most suitable for application under different experimental conditions. Furthermore, the testing methodology provides a framework for other researchers to evaluate and report the baseline activity of other substrates of interest to the broader community.
View details for DOI 10.1371/journal.pone.0107942
View details for Web of Science ID 000346765000003
View details for PubMedID 25357131
View details for PubMedCentralID PMC4214636
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Optoelectronic properties of Ta3N5: A joint theoretical and experimental study
PHYSICAL REVIEW B
2014; 90 (15)
View details for DOI 10.1103/PhysRevB.90.155204
View details for Web of Science ID 000345630800003
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Electrocatalytic Conversion of Carbon Dioxide to Methane and Methanol on Transition Metal Surfaces
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2014; 136 (40): 14107-14113
Abstract
Fuels and industrial chemicals that are conventionally derived from fossil resources could potentially be produced in a renewable, sustainable manner by an electrochemical process that operates at room temperature and atmospheric pressure, using only water, CO2, and electricity as inputs. To enable this technology, improved catalysts must be developed. Herein, we report trends in the electrocatalytic conversion of CO2 on a broad group of seven transition metal surfaces: Au, Ag, Zn, Cu, Ni, Pt, and Fe. Contrary to conventional knowledge in the field, all metals studied are capable of producing methane or methanol. We quantify reaction rates for these two products and describe catalyst activity and selectivity in the framework of CO binding energies for the different metals. While selectivity toward methane or methanol is low for most of these metals, the fact that they are all capable of producing these products, even at a low rate, is important new knowledge. This study reveals a richer surface chemistry for transition metals than previously known and provides new insights to guide the development of improved CO2 conversion catalysts.
View details for DOI 10.1021/ja505791r
View details for Web of Science ID 000343026700028
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Electrocatalytic conversion of carbon dioxide to methane and methanol on transition metal surfaces.
Journal of the American Chemical Society
2014; 136 (40): 14107-14113
Abstract
Fuels and industrial chemicals that are conventionally derived from fossil resources could potentially be produced in a renewable, sustainable manner by an electrochemical process that operates at room temperature and atmospheric pressure, using only water, CO2, and electricity as inputs. To enable this technology, improved catalysts must be developed. Herein, we report trends in the electrocatalytic conversion of CO2 on a broad group of seven transition metal surfaces: Au, Ag, Zn, Cu, Ni, Pt, and Fe. Contrary to conventional knowledge in the field, all metals studied are capable of producing methane or methanol. We quantify reaction rates for these two products and describe catalyst activity and selectivity in the framework of CO binding energies for the different metals. While selectivity toward methane or methanol is low for most of these metals, the fact that they are all capable of producing these products, even at a low rate, is important new knowledge. This study reveals a richer surface chemistry for transition metals than previously known and provides new insights to guide the development of improved CO2 conversion catalysts.
View details for DOI 10.1021/ja505791r
View details for PubMedID 25259478
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Nickel-silver alloy electrocatalysts for hydrogen evolution and oxidation in an alkaline electrolyte.
Physical chemistry chemical physics
2014; 16 (36): 19250-19257
Abstract
The development of improved catalysts for the hydrogen evolution reaction (HER) and hydrogen oxidation reaction (HOR) in basic electrolytes remains a major technical obstacle to improved fuel cells, water electrolyzers, and other devices for electrochemical energy storage and conversion. Based on the free energy of adsorbed hydrogen intermediates, theory predicts that alloys of nickel and silver are active for these reactions. In this work, we synthesize binary nickel-silver bulk alloys across a range of compositions and show that nickel-silver alloys are indeed more active than pure nickel for hydrogen evolution and, possibly, hydrogen oxidation. To overcome the mutual insolubility of silver and nickel, we employ electron-beam physical vapor codeposition, a low-temperature synthetic route to metastable alloys. This method also produces flat and uniform films that facilitate the measurement of intrinsic catalytic activity with minimal variations in the surface area, ohmic contact, and pore transport. Rotating-disk-electrode measurements demonstrate that the hydrogen evolution activity per geometric area of the most active catalyst in this study, Ni0.75Ag0.25, is approximately twice that of pure nickel and has comparable stability and hydrogen oxidation activity. Our experimental results are supported by density functional theory calculations, which show that bulk alloying of Ni and Ag creates a variety of adsorption sites, some of which have near-optimal hydrogen binding energy.
View details for DOI 10.1039/c4cp01385a
View details for PubMedID 25098811
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Engineering tantalum nitride photoanodes for improved activity and stability in photoelectrochemical (PEC) water splitting
AMER CHEMICAL SOC. 2014
View details for Web of Science ID 000349165102466
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Insights into the electrocatalytic reduction of CO2 on metallic silver surfaces.
Physical chemistry chemical physics
2014; 16 (27): 13814-13819
Abstract
The electrochemical reduction of CO2 could allow for a sustainable process by which renewable energy from wind and solar are used directly in the production of fuels and chemicals. In this work we investigated the potential dependent activity and selectivity of the electrochemical reduction of CO2 on metallic silver surfaces under ambient conditions. Our results deepen our understanding of the surface chemistry and provide insight into the factors important to designing better catalysts for the reaction. The high sensitivity of our experimental methods for identifying and quantifying products of reaction allowed for the observation of six reduction products including CO and hydrogen as major products and formate, methane, methanol, and ethanol as minor products. By quantifying the potential-dependent behavior of all products, we provide insights into kinetics and mechanisms at play, in particular involving the production of hydrocarbons and alcohols on catalysts with weak CO binding energy as well as the formation of a C-C bond required to produce ethanol.
View details for DOI 10.1039/c4cp00692e
View details for PubMedID 24915537
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A carbon-free, precious-metal-free, high-performance O-2 electrode for regenerative fuel cells and metal-air batteries
ENERGY & ENVIRONMENTAL SCIENCE
2014; 7 (6): 2017-2024
View details for DOI 10.1039/c3ee44059a
View details for Web of Science ID 000336831700025
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Modeling practical performance limits of photoelectrochemical water splitting based on the current state of materials research.
ChemSusChem
2014; 7 (5): 1372-1385
Abstract
Photoelectrochemical (PEC) water splitting is a means to store solar energy in the form of hydrogen. Knowledge of practical limits for this process can help researchers assess their technology and guide future directions. We develop a model to quantify loss mechanisms in PEC water splitting based on the current state of materials research and calculate maximum solar-to-hydrogen (STH) conversion efficiencies along with associated optimal absorber band gaps. Various absorber configurations are modeled considering the major loss mechanisms in PEC devices. Quantitative sensitivity analyses for each loss mechanism and each absorber configuration show a profound impact of both on the resulting STH efficiencies, which can reach upwards of 25 % for the highest performance materials in a dual stacked configuration. Higher efficiencies could be reached as improved materials are developed. The results of the modeling also identify and quantify approaches that can improve system performance when working with imperfect materials.
View details for DOI 10.1002/cssc.201301030
View details for PubMedID 24692256
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Understanding Interactions between Manganese Oxide and Gold That Lead to Enhanced Activity for Electrocatalytic Water Oxidation.
Journal of the American Chemical Society
2014; 136 (13): 4920-4926
Abstract
To develop active nonprecious metal-based electrocatalysts for the oxygen evolution reaction (OER), a limiting reaction in several emerging renewable energy technologies, a deeper understanding of the activity of the first row transition metal oxides is needed. Previous studies of these catalysts have reported conflicting results on the influence of noble metal supports on the OER activity of the transition metal oxides. Our study aims to clarify the interactions between a transition metal oxide catalyst and its metal support in turning over this reaction. To achieve this goal, we examine a catalytic system comprising nanoparticulate Au, a common electrocatalytic support, and nanoparticulate MnOx, a promising OER catalyst. We conclusively demonstrate that adding Au to MnOx significantly enhances OER activity relative to MnOx in the absence of Au, producing an order of magnitude higher turnover frequency (TOF) than the TOF of the best pure MnOx catalysts reported to date. We also provide evidence that it is a local rather than bulk interaction between Au and MnOx that leads to the observed enhancement in the OER activity. Engineering improvements in nonprecious metal-based catalysts by the addition of Au or other noble metals could still represent a scalable catalyst as even trace amounts of Au are shown to lead a significant enhancement in the OER activity of MnOx.
View details for DOI 10.1021/ja407581w
View details for PubMedID 24661269
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Insights into the electrochemical conversion of CO2 to hydrocarbons and alcohols on transition metals surfaces
AMER CHEMICAL SOC. 2014
View details for Web of Science ID 000348455205072
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Nearly Total Solar Absorption in Ultrathin Nanostructured Iron Oxide for Efficient Photoelectrochemical Water Splitting
ACS PHOTONICS
2014; 1 (3): 235-240
View details for DOI 10.1021/ph4001026
View details for Web of Science ID 000335802900013
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Building an appropriate active-site motif into a hydrogen-evolution catalyst with thiomolybdate [Mo3S13](2-) clusters.
Nature chemistry
2014; 6 (3): 248-253
Abstract
Identifying and understanding the active sites responsible for reaction turnover is critical to developing improved catalysts. For the hydrogen-evolution reaction (HER), MoS2 has been identified as an active non-noble-metal-based catalyst. However, only edge sites turnover the reaction because the basal planes are catalytically inert. In an effort to develop a scalable HER catalyst with an increased number of active sites, herein we report a Mo-S catalyst (supported thiomolybdate [Mo3S13](2-) nanoclusters) in which most sulfur atoms in the structure exhibit a structural motif similar to that observed at MoS2 edges. Supported sub-monolayers of [Mo3S13](2-) nanoclusters exhibited excellent HER activity and stability in acid. Imaging at the atomic scale with scanning tunnelling microscopy allowed for direct characterization of these supported catalysts. The [Mo3S13](2-) nanoclusters reported herein demonstrated excellent turnover frequencies, higher than those observed for other non-precious metal catalysts synthesized by a scalable route.
View details for DOI 10.1038/nchem.1853
View details for PubMedID 24557141
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Controlling the Structural and Optical Properties of Ta3N5 Films through Nitridation Temperature and the Nature of the Ta Metal
CHEMISTRY OF MATERIALS
2014; 26 (4): 1576-1582
View details for DOI 10.1021/cm403482s
View details for Web of Science ID 000332059400012
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High Surface Area Transparent Conducting Oxide Electrodes with a Customizable Device Architecture
CHEMISTRY OF MATERIALS
2014; 26 (2): 958-964
View details for DOI 10.1021/cm402551m
View details for Web of Science ID 000330543600012
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Climbing the Activity Volcano: Core-Shell Ru@Pt Electrocatalysts for Oxygen Reduction
CHEMELECTROCHEM
2014; 1 (1): 67-71
View details for DOI 10.1002/celc.201300117
View details for Web of Science ID 000338287600009
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Insights into the electrocatalytic reduction of CO2 on metallic silver surfaces
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
2014; 16 (27): 13814-13819
Abstract
The electrochemical reduction of CO2 could allow for a sustainable process by which renewable energy from wind and solar are used directly in the production of fuels and chemicals. In this work we investigated the potential dependent activity and selectivity of the electrochemical reduction of CO2 on metallic silver surfaces under ambient conditions. Our results deepen our understanding of the surface chemistry and provide insight into the factors important to designing better catalysts for the reaction. The high sensitivity of our experimental methods for identifying and quantifying products of reaction allowed for the observation of six reduction products including CO and hydrogen as major products and formate, methane, methanol, and ethanol as minor products. By quantifying the potential-dependent behavior of all products, we provide insights into kinetics and mechanisms at play, in particular involving the production of hydrocarbons and alcohols on catalysts with weak CO binding energy as well as the formation of a C-C bond required to produce ethanol.
View details for DOI 10.1039/c4cp00692e
View details for Web of Science ID 000338116700031
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Perfect Sunlight Absorption in Iron Oxide Photoanode
IEEE. 2014
View details for Web of Science ID 000369908602485
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Nanostructured Manganese Oxide Supported onto Particulate Glassy Carbon as an Active and Stable Oxygen Reduction Catalyst in Alkaline-Based Fuel Cells
JOURNAL OF THE ELECTROCHEMICAL SOCIETY
2014; 161 (7): D3105-D3112
View details for DOI 10.1149/2.014407jes
View details for Web of Science ID 000339034800016
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An X-ray Photoelectron Spectroscopy Study of Surface Changes on Brominated and Sulfur-Treated Activated Carbon Sorbents during Mercury Capture: Performance of Pellet versus Fiber Sorbents
ENVIRONMENTAL SCIENCE & TECHNOLOGY
2013; 47 (23): 13695-13701
Abstract
This work explores surface changes and the Hg capture performance of brominated activated carbon (AC) pellets, sulfur-treated AC pellets, and sulfur-treated AC fibers upon exposure to simulated Powder River Basin-fired flue gas. Hg breakthrough curves yielded specific Hg capture amounts by means of the breakthrough shapes and times for the three samples. The brominated AC pellets showed a sharp breakthrough after 170-180 h and a capacity of 585 μg of Hg/g, the sulfur-treated AC pellets exhibited a gradual breakthrough after 80-90 h and a capacity of 661 μg of Hg/g, and the sulfur-treated AC fibers showed no breakthrough even after 1400 h, exhibiting a capacity of >9700 μg of Hg/g. X-ray photoelectron spectroscopy was used to analyze sorbent surfaces before and after testing to show important changes in quantification and oxidation states of surface Br, N, and S after exposure to the simulated flue gas. For the brominated and sulfur-treated AC pellet samples, the amount of surface-bound Br and reduced sulfur groups decreased upon Hg capture testing, while the level of weaker Hg-binding surface S(VI) and N species (perhaps as NH4(+)) increased significantly. A high initial concentration of strong Hg-binding reduced sulfur groups on the surface of the sulfur-treated AC fiber is likely responsible for this sorbent's minimal accumulation of S(VI) species during exposure to the simulated flue gas and is linked to its superior Hg capture performance compared to that of the brominated and sulfur-treated AC pellet samples.
View details for DOI 10.1021/es403280z
View details for PubMedID 24256554
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A Precious-Metal-Free Regenerative Fuel Cell for Storing Renewable Electricity
ADVANCED ENERGY MATERIALS
2013; 3 (12): 1545-1550
View details for DOI 10.1002/aenm.201300492
View details for Web of Science ID 000328337500003
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Benchmarking Heterogeneous Electrocatalysts for the Oxygen Evolution Reaction
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2013; 135 (45): 16977-16987
Abstract
Objective evaluation of the activity of electrocatalysts for water oxidation is of fundamental importance for the development of promising energy conversion technologies including integrated solar water-splitting devices, water electrolyzers, and Li-air batteries. However, current methods employed to evaluate oxygen-evolving catalysts are not standardized, making it difficult to compare the activity and stability of these materials. We report a protocol for evaluating the activity, stability, and Faradaic efficiency of electrodeposited oxygen-evolving electrocatalysts. In particular, we focus on methods for determining electrochemically active surface area and measuring electrocatalytic activity and stability under conditions relevant to an integrated solar water-splitting device. Our primary figure of merit is the overpotential required to achieve a current density of 10 mA cm(-2) per geometric area, approximately the current density expected for a 10% efficient solar-to-fuels conversion device. Utilizing the aforementioned surface area measurements, one can determine electrocatalyst turnover frequencies. The reported protocol was used to examine the oxygen-evolution activity of the following systems in acidic and alkaline solutions: CoO(x), CoPi, CoFeO(x), NiO(x), NiCeO(x), NiCoO(x), NiCuO(x), NiFeO(x), and NiLaO(x). The oxygen-evolving activity of an electrodeposited IrO(x) catalyst was also investigated for comparison. Two general observations are made from comparing the catalytic performance of the OER catalysts investigated: (1) in alkaline solution, every non-noble metal system achieved 10 mA cm(-2) current densities at similar operating overpotentials between 0.35 and 0.43 V, and (2) every system but IrO(x) was unstable under oxidative conditions in acidic solutions.
View details for DOI 10.1021/ja407115p
View details for Web of Science ID 000327103600040
View details for PubMedID 24171402
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Impedance-based study of capacitive porous carbon electrodes with hierarchical and bimodal porosity
JOURNAL OF POWER SOURCES
2013; 241: 266-273
View details for DOI 10.1016/j.jpowsour.2013.03.178
View details for Web of Science ID 000323093700034
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Technical and economic feasibility of centralized facilities for solar hydrogen production via photocatalysis and photoelectrochemistry
ENERGY & ENVIRONMENTAL SCIENCE
2013; 6 (7): 1983-2002
View details for DOI 10.1039/c3ee40831k
View details for Web of Science ID 000320779700001
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In Situ X-ray Absorption Spectroscopy Investigation of a Bifunctional Manganese Oxide Catalyst with High Activity for Electrochemical Water Oxidation and Oxygen Reduction.
Journal of the American Chemical Society
2013; 135 (23): 8525-8534
Abstract
In situ X-ray absorption spectroscopy (XAS) is a powerful technique that can be applied to electrochemical systems, with the ability to elucidate the chemical nature of electrocatalysts under reaction conditions. In this study, we perform in situ XAS measurements on a bifunctional manganese oxide (MnOx) catalyst with high electrochemical activity for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). Using X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS), we find that exposure to an ORR-relevant potential of 0.7 V vs RHE produces a disordered Mn3(II,III,III)O4 phase with negligible contributions from other phases. After the potential is increased to a highly anodic value of 1.8 V vs RHE, relevant to the OER, we observe an oxidation of approximately 80% of the catalytic thin film to form a mixed Mn(III,IV) oxide, while the remaining 20% of the film consists of a less oxidized phase, likely corresponding to unchanged Mn3(II,III,III)O4. XAS and electrochemical characterization of two thin film catalysts with different MnOx thicknesses reveals no significant influence of thickness on the measured oxidation states, at either ORR or OER potentials, but demonstrates that the OER activity scales with film thickness. This result suggests that the films have porous structure, which does not restrict electrocatalysis to the top geometric layer of the film. As the portion of the catalyst film that is most likely to be oxidized at the high potentials necessary for the OER is that which is closest to the electrolyte interface, we hypothesize that the Mn(III,IV) oxide, rather than Mn3(II,III,III)O4, is the phase pertinent to the observed OER activity.
View details for DOI 10.1021/ja3104632
View details for PubMedID 23758050
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Bridging the Gap Between Bulk and Nanostructured Photoelectrodes: The Impact of Surface States on the Electrocatalytic and Photoelectrochemical Properties of MoS2
JOURNAL OF PHYSICAL CHEMISTRY C
2013; 117 (19): 9713-9722
View details for DOI 10.1021/jp311375k
View details for Web of Science ID 000319649100020
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Benchmarking electrocatalysts for hydrogen evolution and oxygen evolution
AMER CHEMICAL SOC. 2013
View details for Web of Science ID 000324303600952
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Growth of Pt Nanowires by Atomic Layer Deposition on Highly Ordered Pyrolytic Graphite
NANO LETTERS
2013; 13 (2): 457-463
Abstract
The formation of Pt nanowires (NWs) by atomic layer deposition on highly ordered pyrolytic graphite (HOPG) is investigated. Pt is deposited only at the step edges of HOPG and not on the basal planes, leading to the formation of laterally aligned Pt NWs. A growth model involving a morphological transition from 0-D to 1-D structures via coalescence is presented. The width of the NWs grows at a rate greater than twice the vertical growth rate. This asymmetry is ascribed to the wetting properties of Pt on HOPG as influenced by the formation of graphene oxide. A difference in Pt growth kinetics based on crystallographic orientation may also contribute.
View details for DOI 10.1021/nl303803p
View details for Web of Science ID 000315079500021
View details for PubMedID 23317031
- Catalyzing chemical transformations in renewable energy: Tailoring Electrocatalyst Materials for Activity, Selectivity, and Stability 2013
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Effect of Temperature Treatment on CoTiOx Catalyst for the Oxygen Evolution Reaction
2nd International Symposium on Electrochemical Synthesis of Fuels (ESF)
ELECTROCHEMICAL SOC INC. 2013: 285–91
View details for DOI 10.1149/05802.0285ecst
View details for Web of Science ID 000328212000030
- Solar hydrogen production by photoelectrochemical (PEC) water-splitting: Advancing technology through the synergistic activities of the PEC working group (PEC WG) 2013
- Exploring Nano-architectures of MoS2: How Surface Structure and Electronic Structure Impact H2 Production by Electrocatalysis and Solar Photoelectrochemistry 2013
- Catalyzing Electrochemical Transformations in Renewable Energy 2013
- The Impact of Surface Structure on the Electrocatalytic and Photoelectrochemical (PEC) Properties of MoS2 2013
- Electrocatalytic Conversion of Carbon Dioxide to Fuels and Chemicals on Transition Metal Electrodes 2013
- Catalyzing key chemical transformations for renewable, sustainable energy 2013
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Mn3O4 Supported on Glassy Carbon: An Active Non-Precious Metal Catalyst for the Oxygen Reduction Reaction
ACS CATALYSIS
2012; 2 (12): 2687-2694
View details for DOI 10.1021/cs3004352
View details for Web of Science ID 000312170100030
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Engineering the surface structure of MoS2 to preferentially expose active edge sites for electrocatalysis
NATURE MATERIALS
2012; 11 (11): 963-969
Abstract
Controlling surface structure at the atomic scale is paramount to developing effective catalysts. For example, the edge sites of MoS(2) are highly catalytically active and are thus preferred at the catalyst surface over MoS(2) basal planes, which are inert. However, thermodynamics favours the presence of the basal plane, limiting the number of active sites at the surface. Herein, we engineer the surface structure of MoS(2) to preferentially expose edge sites to effect improved catalysis by successfully synthesizing contiguous large-area thin films of a highly ordered double-gyroid MoS(2) bicontinuous network with nanoscaled pores. The high surface curvature of this catalyst mesostructure exposes a large fraction of edge sites, which, along with its high surface area, leads to excellent activity for electrocatalytic hydrogen evolution. This work elucidates how morphological control of materials at the nanoscale can significantly impact the surface structure at the atomic scale, enabling new opportunities for enhancing surface properties for catalysis and other important technological applications.
View details for DOI 10.1038/NMAT3439
View details for Web of Science ID 000310434600021
View details for PubMedID 23042413
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Active MnOx Electrocatalysts Prepared by Atomic Layer Deposition for Oxygen Evolution and Oxygen Reduction Reactions
ADVANCED ENERGY MATERIALS
2012; 2 (10): 1269-1277
View details for DOI 10.1002/aenm.201200230
View details for Web of Science ID 000309595900016
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New cubic perovskites for one- and two-photon water splitting using the computational materials repository
ENERGY & ENVIRONMENTAL SCIENCE
2012; 5 (10): 9034-9043
View details for DOI 10.1039/c2ee22341d
View details for Web of Science ID 000308891200029
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Mercury chemistry on brominated activated carbon
FUEL
2012; 99: 188-196
View details for DOI 10.1016/j.fuel.2012.04.036
View details for Web of Science ID 000305150900020
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Amorphous Molybdenum Sulfide Catalysts for Electrochemical Hydrogen Production: Insights into the Origin of their Catalytic Activity
ACS CATALYSIS
2012; 2 (9): 1916-1923
View details for DOI 10.1021/cs300451q
View details for Web of Science ID 000308577300011
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Effect of Film Morphology and Thickness on Charge Transport in Ta3N5/Ta Photoanodes for Solar Water Splitting
JOURNAL OF PHYSICAL CHEMISTRY C
2012; 116 (30): 15918-15924
View details for DOI 10.1021/jp3041742
View details for Web of Science ID 000306989500007
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Meso-Structured Platinum Thin Films: Active and Stable Electrocatalysts for the Oxygen Reduction Reaction
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2012; 134 (18): 7758-7765
Abstract
Improving both the activity and the stability of the cathode catalyst in platinum-based polymer electrolyte fuel cells is a key technical challenge. Here, we synthesize a high surface area meso-structured Pt thin film that exhibits higher specific activity for the oxygen reduction reaction (ORR) than commercial carbon-supported Pt nanoparticles (Pt/C). An accelerated stability test demonstrates that the meso-structured Pt thin film also displays significantly enhanced stability as compared to the commercial Pt/C catalyst. Our study reveals the origin of the high turnover frequency (TOF), and excellent durability is attributed to the meso-structure, which yields a morphology with fewer undercoordinated Pt sites than Pt/C nanoparticles, a key difference with substantial impact to the surface chemistry. The improved catalyst activity and stability could enable the development of a high-performance gas diffusion electrode that is resistant to corrosion even under the harsh conditions of start-up, shut-down, and/or hydrogen starvation.
View details for DOI 10.1021/ja2120162
View details for Web of Science ID 000303696200035
View details for PubMedID 22500676
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New insights into the electrochemical reduction of carbon dioxide on metallic copper surfaces
ENERGY & ENVIRONMENTAL SCIENCE
2012; 5 (5): 7050-7059
View details for DOI 10.1039/c2ee21234j
View details for Web of Science ID 000303251500047
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Simulating Linear Sweep Voltammetry from First-Principles: Application to Electrochemical Oxidation of Water on Pt(111) and Pt3Ni(111)
JOURNAL OF PHYSICAL CHEMISTRY C
2012; 116 (7): 4698-4704
View details for DOI 10.1021/jp210802q
View details for Web of Science ID 000301156500043
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Investigation of Surface Oxidation Processes on Manganese Oxide Electrocatalysts Using Electrochemical Methods and Ex Situ X-ray Photoelectron Spectroscopy
JOURNAL OF THE ELECTROCHEMICAL SOCIETY
2012; 159 (10): H782-H786
View details for DOI 10.1149/2.017210jes
View details for Web of Science ID 000309105500057
- Tailoring electrocatalyst materials to enhance activity, stability, and selectivity for key energy conversion reactions 2012
- Electrocatalysis 101 2012
- Developing Electrocatalysts for the Synthesis of Renewable Fuels 2012
- Catalyzing chemical transformations in renewable energy: Tailoring electrocatalyst materials for activity, selectivity, and stability 2012
- The electrocatalytic conversion of CO2 to fuels and chemicals 2012
- Tailoring electrocatalyst materials to enhance activity, stability, and selectivity for key energy conversion reactions 2012
- Tailoring electrocatalyst materials to enhance activity, stability, and selectivity for key energy conversion reactions 2012
- Engineering the Surface Structure of MoS2 Through Morphological Control At the Nano-Scale for Enhanced Electrocatalytic Hydrogen Production 2012
- Bridging the gap between optical absorption and charge transport in metal oxide materials for the synthesis of solar fuels 2012
- Tailoring Electrocatalyst Materials at the Nano-Scale: Controlling Activity, Selectivity, and Stability for Energy Conversion Reactions 2012
- Tailoring Electrocatalyst Materials at the Nano-Scale: Controlling Activity, Selectivity, and Stability for Energy Conversion Reactions 2012
- Solar Fuels by Photocatalysis and Photoelectrochemistry 2012
- Insights into the electrochemical conversion of CO2 to fuels and chemicals on transition metal surfaces 2012
- Directed Nano-scale and Macro-scale Architectures for Semiconductor Absorbers and Transparent Conducting Substrates for Photoelectrochemical Water Splitting 2012
- Addressing charge transport limitations in thin film Ta3N5 & TaON photoanodes for solar fuel synthesis 2012
- Energy Storage by Means of Renewable Fuels 2012
- Electrocatalyst development for renewable energy: Engineering surface structure at the atomic-scale by controlling morphology at the nano-scale 2012
- Tailoring Electrocatalyst Materials at the Nano-Scale: Controlling Activity, Selectivity, and Stability for Energy Conversion Reactions 2012
- Electrocatalyst development for the synthesis of renewable fuels from water and CO2 2012
- A tutorial on electrocatalysis: Concepts, fundamentals, methods, and applications 2012
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Identifying active surface phases for metal oxide electrocatalysts: a study of manganese oxide bi-functional catalysts for oxygen reduction and water oxidation catalysis
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
2012; 14 (40): 14010-14022
Abstract
Progress in the field of electrocatalysis is often hampered by the difficulty in identifying the active site on an electrode surface. Herein we combine theoretical analysis and electrochemical methods to identify the active surfaces in a manganese oxide bi-functional catalyst for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). First, we electrochemically characterize the nanostructured α-Mn(2)O(3) and find that it undergoes oxidation in two potential regions: initially, between 0.5 V and 0.8 V, a potential region relevant to the ORR and, subsequently, between 0.8 V and 1.0 V, a potential region between the ORR and the OER relevant conditions. Next, we perform density function theory (DFT) calculations to understand the changes in the MnO(x) surface as a function of potential and to elucidate reaction mechanisms that lead to high activities observed in the experiments. Using DFT, we construct surface Pourbaix and free energy diagrams of three different MnO(x) surfaces and identify 1/2 ML HO* covered Mn(2)O(3) and O* covered MnO(2), as the active surfaces for the ORR and the OER, respectively. Additionally, we find that the ORR occurs through an associative mechanism and that its overpotential is highly dependent on the stabilization of intermediates through hydrogen bonds with water molecules. We also determine that OER occurs through direct recombination mechanism and that its major source of overpotential is the scaling relationship between HOO* and HO* surface intermediates. Using a previously developed Sabatier model we show that the theoretical predictions of catalytic activities match the experimentally determined onset potentials for the ORR and the OER, both qualitatively and quantitatively. Consequently, the combination of first-principles theoretical analysis and experimental methods offers an understanding of manganese oxide oxygen electrocatalysis at the atomic level, achieving fundamental insight that can potentially be used to design and develop improved electrocatalysts for the ORR and the OER and other important reactions of technological interest.
View details for DOI 10.1039/c2cp40841d
View details for Web of Science ID 000309140400036
View details for PubMedID 22990481
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Addressing the terawatt challenge: scalability in the supply of chemical elements for renewable energy
RSC ADVANCES
2012; 2 (21): 7933-7947
View details for DOI 10.1039/c2ra20839c
View details for Web of Science ID 000307792200001
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Branched TiO2 Nanorods for Photoelectrochemical Hydrogen Production
NANO LETTERS
2011; 11 (11): 4978-4984
Abstract
We report a hierarchically branched TiO(2) nanorod structure that serves as a model architecture for efficient photoelectrochemical devices as it simultaneously offers a large contact area with the electrolyte, excellent light-trapping characteristics, and a highly conductive pathway for charge carrier collection. Under Xenon lamp illumination (UV spectrum matched to AM 1.5G, 88 mW/cm(2) total power density), the branched TiO(2) nanorod array produces a photocurrent density of 0.83 mA/cm(2) at 0.8 V versus reversible hydrogen electrode (RHE). The incident photon-to-current conversion efficiency reaches 67% at 380 nm with an applied bias of 0.6 V versus RHE, nearly two times higher than the bare nanorods without branches. The branches improve efficiency by means of (i) improved charge separation and transport within the branches due to their small diameters, and (ii) a 4-fold increase in surface area which facilitates the hole transfer at the TiO(2)/electrolyte interface.
View details for DOI 10.1021/nl2029392
View details for Web of Science ID 000296674700082
View details for PubMedID 21999403
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Core-shell MoO3-MoS2 Nanowires for Hydrogen Evolution: A Functional Design for Electrocatalytic Materials
NANO LETTERS
2011; 11 (10): 4168-4175
Abstract
We synthesize vertically oriented core-shell nanowires with substoichiometric MoO(3) cores of ∼20-50 nm and conformal MoS(2) shells of ∼2-5 nm. The core-shell architecture, produced by low-temperature sulfidization, is designed to utilize the best properties of each component material while mitigating their deficiencies. The substoichiometric MoO(3) core provides a high aspect ratio foundation and enables facile charge transport, while the conformal MoS(2) shell provides excellent catalytic activity and protection against corrosion in strong acids.
View details for DOI 10.1021/nl2020476
View details for Web of Science ID 000295667000024
View details for PubMedID 21894935
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Plasmon Enhanced Solar-to-Fuel Energy Conversion
NANO LETTERS
2011; 11 (8): 3440-3446
Abstract
Future generations of photoelectrodes for solar fuel generation must employ inexpensive, earth-abundant absorber materials in order to provide a large-scale source of clean energy. These materials tend to have poor electrical transport properties and exhibit carrier diffusion lengths which are significantly shorter than the absorption depth of light. As a result, many photoexcited carriers are generated too far from a reactive surface and recombine instead of participating in solar-to-fuel conversion. We demonstrate that plasmonic resonances in metallic nanostructures and multilayer interference effects can be engineered to strongly concentrate sunlight close to the electrode/liquid interface, precisely where the relevant reactions take place. On comparison of spectral features in the enhanced photocurrent spectra to full-field electromagnetic simulations, the contribution of surface plasmon excitations is verified. These results open the door to the optimization of a wide variety of photochemical processes by leveraging the rapid advances in the field of plasmonics.
View details for DOI 10.1021/nl201908s
View details for Web of Science ID 000293665600066
View details for PubMedID 21749077
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Universality in Oxygen Evolution Electrocatalysis on Oxide Surfaces
CHEMCATCHEM
2011; 3 (7): 1159-1165
View details for DOI 10.1002/cctc.201000397
View details for Web of Science ID 000293384000012
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Thin Films of Sodium Birnessite-Type MnO2: Optical Properties, Electronic Band Structure, and Solar Photoelectrochemistry
JOURNAL OF PHYSICAL CHEMISTRY C
2011; 115 (23): 11830-11838
View details for DOI 10.1021/jp200015p
View details for Web of Science ID 000291339000063
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Electrocatalysis on manganese oxide surfaces: Oxygen reduction and water oxidation
241st National Meeting and Exposition of the American-Chemical-Society (ACS)
AMER CHEMICAL SOC. 2011
View details for Web of Science ID 000291982803880
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Ex-situ Spectroscopy Study of Manganese Oxide Catalytic Surfaces under Reaction Conditions Relevant to Oxygen Reduction and Oxygen Evolution
11th Polymer Electrolyte Fuel Cell Symposium (PEFC) Under the Auspices of the 220th Meeting of the ECS
ELECTROCHEMICAL SOC INC. 2011: 1701–7
View details for DOI 10.1149/1.3635701
View details for Web of Science ID 000309598800163
- Tailoring Electrocatalyst Materials at the Nano-Scale: Controlling Activity, Selectivity, and Stability for Energy Conversion Reactions 2011
- Nanostructured electrocatalysts for energy conversion reactions 2011
- Nanomaterials for efficient chemical transformations in energy conversion reactions 2011
- Catalyzing the production of clean fuels from renewable energy resources 2011
- Tailoring electrocatalyst materials at the nano-scale: Controlling activity, selectivity, and stability for energy conversion reactions 2011
- Tailoring Electrocatalyst Materials at the Nano-Scale: Controlling Activity, Selectivity, and Stability for Energy Conversion Reactions 2011
- Nano-architectures for 3rd generation PEC devices: A study of MoS2, fundamental investigations and applied research 2011
- Engineering catalysts at the nano-scale for energy conversion reactions 2011
- Tailoring electrocatalyst materials at the nano-scale: Controlling activity and selectivity for energy conversion reactions 2011
- Tailoring electrocatalyst materials at the nano-scale: Controlling activity and selectivity for energy conversion reactions 2011
- Semiconductors and catalysts for the production of solar fuels 2011
- Non-precious metal catalysts for electrochemical transformations between H2, O2, and H2O 2011
- Electrocatalytic conversion of CO2 to fuels on metal surfaces 2011
- Electrocatalytic Conversion of CO2 to Fuels on Metal Surfaces 2011
- Tailoring Electrocatalyst Materials at the Nano-Scale: Controlling Activity, Selectivity, and Stability for Energy Conversion Reactions 2011
- Tailoring electrocatalyst materials at the nano-scale: Controlling activity and selectivity for energy conversion reactions 2011
- Tailoring electrocatalyst materials at the nano-scale: Controlling activity and selectivity for energy conversion reactions 2011
- Nanostructured Catalysts for Chemical Transformations in Energy 2011
- Advanced electrode and photo-electrode structures for the synthesis of fuels from sunlight 2011
- Double Gyroid Nanostructured Platinum As Highly Durable Oxygen Reduction Reaction Electrocatalyst 2011
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A Bifunctional Nonprecious Metal Catalyst for Oxygen Reduction and Water Oxidation
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2010; 132 (39): 13612-13614
Abstract
There is a growing interest in oxygen electrochemistry as conversions between O(2) and H(2)O play an important role in a variety of renewable energy technologies. The goal of this work is to develop active bifunctional catalyst materials for water oxidation and oxygen reduction. Drawing inspiration from a cubane-like CaMn(4)O(x), the biological catalyst found in the oxygen evolving center (OEC) in photosystem II, nanostructured manganese oxide surfaces were investigated for these reactions. Thin films of nanostructured manganese oxide were found to be active for both oxygen reduction and water oxidation, with similar overall oxygen electrode activity to the best known precious metal nanoparticle catalysts: platinum, ruthenium, and iridium. Physical and chemical characterization of the nanostructured Mn oxide bifunctional catalyst reveals an oxidation state of Mn(III), akin to one of the most commonly observed Mn oxidation states found in the OEC.
View details for DOI 10.1021/ja104587v
View details for Web of Science ID 000282864100017
View details for PubMedID 20839797
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Nanostructured MoS2 for solar hydrogen production
AMER CHEMICAL SOC. 2010
View details for Web of Science ID 000208189302571
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Accelerating materials development for photoelectrochemical hydrogen production: Standards for methods, definitions, and reporting protocols
JOURNAL OF MATERIALS RESEARCH
2010; 25 (1): 3-16
View details for DOI 10.1557/JMR.2010.0020
View details for Web of Science ID 000273858900002
- Developing solid-state electrocatalysts based on design principles from nature: The oxidation of water and the reduction of CO2 to fuels 2010
- Nanostructured MoS2 and WS2 for the solar production of hydrogen 2010
- Nano-structured materials for the synthesis of fuels from sunlight 2010
- Surface electrocatalysis for fuel synthesis: Inspiration from nature 2010
- Nano-scaled materials for the synthesis of fuels from sunlight 2010
- Nano-scaled materials for the synthesis of fuels from sunlight 2010
- Nano-scaled materials for the synthesis of fuels from sunlight 2010
- Nano-scaled materials for the synthesis of fuels from sunlight 2010
- In pursuit of a reversible oxygen electrode: Water oxidation and oxygen reduction on electro-catalytic oxide surfaces 2010
- Bi-functional electrocatalysis on manganese oxide surfaces: oxygen reduction and water oxidation 2010
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Nanostructuring MoS2 for Photoelectrochemical Water Splitting
Conference on Solar Hydrogen and Nanotechnology V
SPIE-INT SOC OPTICAL ENGINEERING. 2010
View details for DOI 10.1117/12.860659
View details for Web of Science ID 000286094200009
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Monolithic III-V Nanowire PV for Photoelectrochemical Hydrogen Generation
35th IEEE Photovoltaic Specialists Conference
IEEE. 2010: 1793–1796
View details for Web of Science ID 000287579502007
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Alloys of platinum and early transition metals as oxygen reduction electrocatalysts
NATURE CHEMISTRY
2009; 1 (7): 552-556
Abstract
The widespread use of low-temperature polymer electrolyte membrane fuel cells for mobile applications will require significant reductions in the amount of expensive Pt contained within their cathodes, which drive the oxygen reduction reaction (ORR). Although progress has been made in this respect, further reductions through the development of more active and stable electrocatalysts are still necessary. Here we describe a new set of ORR electrocatalysts consisting of Pd or Pt alloyed with early transition metals such as Sc or Y. They were identified using density functional theory calculations as being the most stable Pt- and Pd-based binary alloys with ORR activity likely to be better than Pt. Electrochemical measurements show that the activity of polycrystalline Pt(3)Sc and Pt(3)Y electrodes is enhanced relative to pure Pt by a factor of 1.5-1.8 and 6-10, respectively, in the range 0.9-0.87 V.
View details for DOI 10.1038/NCHEM.367
View details for Web of Science ID 000270077200014
View details for PubMedID 21378936
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Combined spectroscopy and microscopy of supported MoS2 nanoparticles
SURFACE SCIENCE
2009; 603 (9): 1182-1189
View details for DOI 10.1016/j.susc.2009.02.039
View details for Web of Science ID 000266610700007
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Electrocatalytic Activity of Gold-Platinum Clusters for Low Temperature Fuel Cell Applications
JOURNAL OF PHYSICAL CHEMISTRY C
2009; 113 (12): 5014-5024
View details for DOI 10.1021/jp8089209
View details for Web of Science ID 000264349100044
- Electrocatalytic activity of gold-platinum clusters for low temperature fuel cell applications Journal of Physical Chemistry C 2009; 113 (12): 5014-5024
- Photon absorbers and energy conversion catalysts: New approaches to solar fuels 2009
- Nanostructured MoS2 for the Photoelectrochemical Production of Hydrogen 2009
- Nanostructured MoS2 and WS2 for the solar production of hydrogen 2009
- Nanostructured MoS2 and WS2 for the solar production of hydrogen 2009
- Nanostructured MoS2 and WS2 for the solar production of hydrogen 2009
- Nano-scaled semiconductors and novel catalysts for the synthesis of fuels from sunlight 2009
- Designing new electrocatalysts: A case study of the hydrogen evolution reaction (HER) 2009
- Combined spectroscopy and microscopy of supported MoS2 nanoparticles Surface Science 2009; 603 (9): 1182-1189
- Alloys of platinum and early transition metals as oxygen reduction electrocatalysts Nature Chemistry 2009; 1 (7): 552-556
- Designing new electrocatalysts for the hydrogen evolution reaction (HER): combining theory and experiment 2009
- Solar Fuels by Photoelectrochemistry (PEC) 2009
- Nano-structured MoS2 and WS2 for the Solar Production of Hydrogen 2009
- Nano-scaled materials for the synthesis of fuels from sunlight 2009
- Designing nano-scaled, non-precious metal catalysts for hydrogen evolution 2009
- Nano-scaled materials for the synthesis of fuels from sunlight 2009
- The Dynamics of Surface Exchange Reactions Between Au and Pt for the Hydrogen Evolution Reaction (HER) and the Hydrogen Oxidation Reaction (HOR) Journal of the Electrochemical Society 2009; 156 (2): B273-B282
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Dynamics of Surface Exchange Reactions Between Au and Pt for HER and HOR
JOURNAL OF THE ELECTROCHEMICAL SOCIETY
2009; 156 (2): B273-B282
View details for DOI 10.1149/1.3040509
View details for Web of Science ID 000261973600018
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Hydrogen Evolution on Supported Incomplete Cubane-type [Mo3S4](4+) Electrocatalysts
JOURNAL OF PHYSICAL CHEMISTRY C
2008; 112 (45): 17492-17498
View details for DOI 10.1021/jp802695e
View details for Web of Science ID 000260675900002
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Hydrogen evolution on nano-particulate transition metal sulfides
Conference on Electrocatalysis Theory and Experiment at the Interface
ROYAL SOC CHEMISTRY. 2008: 219–231
Abstract
The hydrogen evolution reaction (HER) on carbon supported MoS2 nanoparticles is investigated and compared to findings with previously published work on Au(111) supported MoS2. An investigation into MoS2 oxidation is presented and used to quantify the surface concentration of MoS2. Other metal sulfides with morphologies similar to MoS2 such as WS2, cobalt-promoted WS2, and cobalt-promoted MoS2 were also investigated in the search for improved HER activity. Experimental findings are compared to density functional theory (DFT) calculated values for the hydrogen binding energies (deltaGH) on each system.
View details for DOI 10.1039/b803857k
View details for Web of Science ID 000260437800016
View details for PubMedID 19213319
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Steady state oxygen reduction and cyclic voltammetry
Conference on Electrocatalysis Theory and Experiment at the Interface
ROYAL SOC CHEMISTRY. 2008: 337–346
Abstract
The catalytic activity of Pt and Pt3Ni for the oxygen reduction reaction is investigated by applying a Sabatier model based on density functional calculations. We investigate the role of adsorbed OH on the activity, by comparing cyclic voltammetry obtained from theory with previously published experimental results with and without molecular oxygen present. We find that the simple Sabatier model predicts both the potential dependence of the OH coverage and the measured current densities seen in experiments, and that it offers an understanding of the oxygen reduction reaction (ORR) at the atomic level. To investigate kinetic effects we develop a simple kinetic model for ORR. Whereas kinetic corrections only matter close to the volcano top, an interesting outcome of the kinetic model is a first order dependence on the oxygen pressure. Importantly, the conclusion obtained from the simple Sabatier model still persists: an intermediate binding of OH corresponds to the highest catalytic activity, i.e. Pt is limited by a too strong OH binding and Pt3Ni is limited by a too weak OH binding.
View details for DOI 10.1039/b802129e
View details for Web of Science ID 000260437800023
View details for PubMedID 19213325
- Designing novel electrocatalytic materials: a case study of the hydrogen evolution reaction (HER). 2008
- Designing electrocatalysts for the hydrogen evolution reaction. 2008
- Steady state oxygen reduction reaction and cyclic voltammetry 2008
- Precious-metal and non-precious metal based nano-scale electrocatalysts for electrocatalytic hydrogen evolution. 2008
- New materials for electrocatalytic hydrogen production: from alloys to nanoparticles 2008
- Solar fuels by photoelectrochemistry: Prospects and challenges. 2008
- Developing new hydrogen evolution electrocatalysts: metal surface alloys and nano-scale molybdenum sulfides. 2008
- Designing new electrocatalytic materials for the hydrogen evolution reaction (HER). 2008
- Electrocatalytic materials for the hydrogen evolution reaction. 2008
- Designing non-noble metal electrocatalysts: An investigation of the hydrogen evolution reaction. 2008
- Non-precious metal electrocatalysts for the hydrogen evolution reaction (HER): Inspiration for designing new PEC materials 2008
- In the pursuit of active, non-precious metal electrocatalysts: A study of the hydrogen evolution reaction (HER). 2008
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Cyclic voltammograms for H on Pt(111) and Pt(100) from first principles
PHYSICAL REVIEW LETTERS
2007; 99 (12)
Abstract
Cyclic voltammetry is a fundamental experimental method for characterizing electrochemical surfaces. Despite its wide use, a way to quantitatively and directly relate cyclic voltammetry to ab initio calculations has been lacking. We derive the cyclic voltammogram for H on Pt(111) and Pt(100), based solely on density functional theory calculations and standard molecular tables. By relating the gas phase adsorption energy to the electrochemical electrode potential, we provide a direct link between surface science and electrochemistry.
View details for DOI 10.1103/PhysRevLett.99.126101
View details for Web of Science ID 000249668000046
View details for PubMedID 17930522
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Identification of active edge sites for electrochemical H-2 evolution from MoS2 nanocatalysts
SCIENCE
2007; 317 (5834): 100-102
Abstract
The identification of the active sites in heterogeneous catalysis requires a combination of surface sensitive methods and reactivity studies. We determined the active site for hydrogen evolution, a reaction catalyzed by precious metals, on nanoparticulate molybdenum disulfide (MoS2) by atomically resolving the surface of this catalyst before measuring electrochemical activity in solution. By preparing MoS2 nanoparticles of different sizes, we systematically varied the distribution of surface sites on MoS2 nanoparticles on Au(111), which we quantified with scanning tunneling microscopy. Electrocatalytic activity measurements for hydrogen evolution correlate linearly with the number of edge sites on the MoS2 catalyst.
View details for DOI 10.1126/science.1141483
View details for Web of Science ID 000247776700058
View details for PubMedID 17615351
- From theory to experiment: New electrocatalysts for the hydrogen evolution reaction 2007
- Nano-scale molybdenum sulfides for electrocatalytic hydrogen evolution 2007
- From alloys to bio-mimetic materials: searching for new hydrogen evolution electrocatalysts 2007
- Identification of Active Edge Sites for Electrochemical H2 Evolution from MoS2 Nanocatalysts Science 2007; 317 (5834): 100-102
- Cyclic voltammograms for H on Pt(111) and Pt(100) from first principles Physical Review Letters 2007; 99 (126101)
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Computational high-throughput screening of electrocatalytic materials for hydrogen evolution
NATURE MATERIALS
2006; 5 (11): 909-913
Abstract
The pace of materials discovery for heterogeneous catalysts and electrocatalysts could, in principle, be accelerated by the development of efficient computational screening methods. This would require an integrated approach, where the catalytic activity and stability of new materials are evaluated and where predictions are benchmarked by careful synthesis and experimental tests. In this contribution, we present a density functional theory-based, high-throughput screening scheme that successfully uses these strategies to identify a new electrocatalyst for the hydrogen evolution reaction (HER). The activity of over 700 binary surface alloys is evaluated theoretically; the stability of each alloy in electrochemical environments is also estimated. BiPt is found to have a predicted activity comparable to, or even better than, pure Pt, the archetypical HER catalyst. This alloy is synthesized and tested experimentally and shows improved HER performance compared with pure Pt, in agreement with the computational screening results.
View details for DOI 10.1038/nmat1752
View details for Web of Science ID 000241732000026
View details for PubMedID 17041585
- New electrode materials for hydrogen production: A focus on nanoparticulate molybdenum sulfides 2006
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Low-voltage electrodeposition of fullerol thin films from aqueous solutions
JOURNAL OF THE ELECTROCHEMICAL SOCIETY
2006; 153 (7): C483-C487
View details for DOI 10.1149/1.2196671
View details for Web of Science ID 000237945300037
- New materials for hydrogen production: Nanoparticulate molybdenum sulfides 2006
- Electrocatalysis at nanometer and sub-nanometer scales: Hydrogen evolution on supported MoS2 and Mo3S4 clusters 2006
- Low-voltage electrodeposition of fullerol thin films from aqueous solutions Journal of the Electrochemical Society 2006; 153 (7): C483-C487
- New materials for hydrogen evolution: From alloys to nanoparticles 2006
- Nanoparticulate MoS2 electrocatalysts for hydrogen evolution 2006
- Biocatalysis and biomimetics for electrochemical hydrogen conversion. Electrocatalysis at the sub-nanometer scale: structure and function of supported Mo3S4 clusters 2006
- Computational high-throughput screening of electrocatalytic materials for hydrogen evolution Nature Materials 2006; 5 (11): 909-913
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Synthesis and characterization of Pt-WO3 as methanol oxidation catalysts for fuel cells
JOURNAL OF PHYSICAL CHEMISTRY B
2005; 109 (48): 22958-22966
Abstract
Several compositions of Pt-WO3 catalysts were synthesized and characterized for the electro-oxidation of methanol and CO. The surface morphologies of the catalysts were found to be dependent on the composition. X-ray energy dispersive spectroscopy and X-ray photoelectron spectroscopy results suggest a surface enrichment of WO3 in the codeposited Pt-WO3 catalysts. Cyclic voltammetry and chronoamperometry in methanol show an improvement in catalytic activity for the Pt-WO3 catalysts. A significant improvement in the poison tolerance toward CO and other organic intermediates was observed in the mixed metal-metal oxide catalyst. The catalytic performance of the different compositions was directly compared by normalization of the current to active sites. CO-stripping voltammetry suggests the involvement of WO3 in the catalytic process as opposed to a mere physical effect as suggested by previous work. A possible mechanism for this improvement is proposed based on the electrochemical data.
View details for DOI 10.1021/jp053053h
View details for Web of Science ID 000233761300035
View details for PubMedID 16853991
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Combinatorial electrochemical synthesis and screening of Pt-WO3 catalysts for electro-oxidation of methanol
REVIEW OF SCIENTIFIC INSTRUMENTS
2005; 76 (6)
View details for DOI 10.1063/1.1927007
View details for Web of Science ID 000229962000029
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Synthesis of Au nanoclusters supported upon a TiO2 nanotube array
JOURNAL OF MATERIALS RESEARCH
2005; 20 (5): 1093-1096
View details for DOI 10.1557/JMR.2005.0170
View details for Web of Science ID 000229293700003
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Automated electrochemical synthesis and photoelectrochemical characterization of Zn1-xCoxO thin films for solar hydrogen production
JOURNAL OF COMBINATORIAL CHEMISTRY
2005; 7 (2): 264-271
Abstract
High-throughput electrochemical methods have been developed for the investigation of Zn1-xCo(x)O films for photoelectrochemical hydrogen production from water. A library of 120 samples containing 27 different compositions (0
View details for DOI 10.1021/cc049864x
View details for Web of Science ID 000227708100015
View details for PubMedID 15762755
- Combinatorial electrochemical synthesis and screening of Pt-WO3 catalysts for electro-oxidation of methanol Review of Scientific Instruments 2005; 76 (6)
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Automated electrochemical synthesis and characterization of TiO2 supported Au nanoparticle electrocatalysts
MEASUREMENT SCIENCE & TECHNOLOGY
2005; 16 (1): 54-59
View details for DOI 10.1088/0957-0233/16/1/008
View details for Web of Science ID 000226655800009
- High-throughput methods for the investigation of photoelectrochemical hydrogen production from Zn1-xCoxO thin films 2005
- Mixed-metal nanoparticles for fuel cell catalysis 2005
- Combinatorial Discovery: New Materials for Photoelectrochemical Hydrogen Production 2005
- Synthesis and characterization of Pt-WO3 films as methanol oxidation catalysts for low-temperature polymer electrolyte membrane fuel cells Journal of Physical Chemistry B 2005; 109 (48): 22958-22966
- Optimized Materials for Photoelectrochemical Hydrogen Production 2005
- New materials for energy conversion reactions: photoelectrochemical hydrogen production and electrocatalytic methanol oxidation 2005
- Automated electrochemical synthesis and photoelectrochemical characterization of Zn1-xCoxO thin films for solar hydrogen production Journal of Combinatorial Chemistry 2005; 7 (2): 264-271
- Automated electrochemical synthesis and characterization of TiO2 supported Au nanoparticle electrocatalysts Measurement Science & Technology 2005; 16 (1): 54-59
- Photoelectrochemical hydrogen production: a combinatorial investigation of ZnO-based materials 2005
- New materials for photoelectrochemical hydrogen production: A high-throughput investigation 2005
- High throughput investigation of new materials for the photoelectrochemical production of hydrogen 2005
- Doped semiconductors and mixed-metal nanoparticles: New materials for energy conversion reactions 2005
- Synthesis of titania nanotubes with supported Au nanoclusters Journal of Materials Research 2005; 20 (5): 1093-1096
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Gas-phase catalysis by micelle derived Au nanoparticles on oxide supports
CATALYSIS LETTERS
2004; 95 (3-4): 107-111
View details for Web of Science ID 000221338900002
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Parallel synthesis and characterization of photoelectrochemically and electrochromically active tungsten-molybdenum oxides
CHEMICAL COMMUNICATIONS
2004: 390-391
Abstract
Single phase tungsten-molybdenum mixed oxide films (W(1-x)Mo(x)O(3)) were successfully synthesized by automated parallel electrodeposition, and distinct structural changes were observed as a function of composition. A monoclinic structure (beta-phase) was observed in mixed oxides with less than 90% Mo, and above 90% Mo, orthorhombic structure (alpha-phase) was identified.
View details for DOI 10.1039/b313924g
View details for Web of Science ID 000220108100017
View details for PubMedID 14765223
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Combinatorial electrochemical synthesis and screening of mesoporous ZnO for photocatalysis
Workshop on Combinatorial and High-Throughput Approaches in Polymer and Materials Science
WILEY-V C H VERLAG GMBH. 2004: 297–301
View details for DOI 10.1002/marc.200300187
View details for Web of Science ID 000188385300033
- Combinatorial electrochemical synthesis and screening of mesoporous ZnO for photocatalysis Macromolecular Rapid Communications 2004; 25 (1): 297-301
- Structure, composition, and morphology of photoelectrochemically active TiO2-xNx thin films deposited by reactive DC magnetron sputtering Journal of Physical Chemistry B 2004; 108 (52): 20193-20198
- Parallel synthesis and characterization of photoelectrochemically and electrochromically active tungsten molybdenum oxides Chemical Communications 2004; 4: 390-391
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Size- and support-dependent electronic and catalytic properties of Au-0/Au3+ nanoparticles synthesized from block copolymer micelles
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2003; 125 (42): 12928-12934
Abstract
Supported Au nanoclusters synthesized from diblock copolymer micelles can be reliably prepared with well-controlled sizes and dispersions. For particles with diameters between approximately 1 and 6 nm, the particle size and the support were found to strongly influence the oxygen reactivity, the formation and stabilization of a metal-oxide, and the catalytic activity for electrooxidation of carbon monoxide. The smallest particles studied (1.5 nm) were the most active for electrooxidation of CO and had the largest fraction of oxygen associated with gold at the surface as measured by the Au(3+)/Au(0) X-ray photoemission intensities. Conducting and semiconducting substrates, ITO-coated glass and TiO(2), respectively, were associated with greater stabilization of Au(3+) oxide as compared to insulating, SiO(2), substrates.
View details for DOI 10.1021/ja036468u
View details for Web of Science ID 000185990300053
View details for PubMedID 14558841
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Synthesis of tungsten oxide on copper surfaces by electroless deposition
CHEMISTRY OF MATERIALS
2003; 15 (18): 3411-3413
View details for DOI 10.1021/cm0341641
View details for Web of Science ID 000185221500003
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Enhancement of photocatalytic and electrochromic properties of electrochemically fabricated mesoporous WO3 thin films
ADVANCED MATERIALS
2003; 15 (15): 1269-?
View details for DOI 10.1002/adma.200304669
View details for Web of Science ID 000184798700008
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Catalytic activity of supported au nanoparticles deposited from block copolymer micelles
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2003; 125 (24): 7148-7149
Abstract
Quasi-ordered, highly dispersed, gold nanoclusters of tightly controlled particle size were synthesized by dip-coating substrates with gold precursors encapsulated by block-copolymer micelles. By this method, gold particles (4.8 +/- 1.3 nm) were deposited on ITO-coated glass and shown to be catalytically active for electro-oxidation of carbon monoxide. XPS confirmed the catalytically active particles were predominantly Au0; however, a large fraction existed as Au3+. Whereas bulk gold is inert, these results demonstrate that catalytically active Au nanoparticles can be derived from micelle encapsulation.
View details for Web of Science ID 000183503500002
View details for PubMedID 12797767
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A CU2O/TiO2 heterojunction thin film cathode for photoelectrocatalysis
SOLAR ENERGY MATERIALS AND SOLAR CELLS
2003; 77 (3): 229-237
View details for Web of Science ID 000182193700001
- Enhancement of photocatalytic and electrochromic properties of electrochemically fabricated mesoporous WO3 thin films Advanced Materials 2003; 15 (15): 1269-1273
- Photoelectrochemical Hydrogen Production Using New Combinatorial Chemistry Derived Materials 2003
- Combinatorial Investigation of New Materials for Photoelectrochemical Hydrogen Production 2003
- Catalytic activity of supported Au nanoparticles deposited from block copolymer micelles Journal of the American Chemical Society 2003; 125 (24): 7148-7149
- A Cu2O/TiO2 heterojunction thin film cathode for photoelectrocatalysis Solar Energy Materials and Solar Cells 2003; 77 (3): 229-237
- Size and support dependent electronic and catalytic properties of Au0/Au3+ nanoparticles synthesized from block co-polymer micelles Journal of the American Chemical Society 2003; 125 (42): 12928-12934
- Combinatorial Electrochemical Synthesis and Screening of Transition-Metal Doped Zinc Oxides as Water-Splitting Photocatalysts for H2 Production 2003
- Synthesis of tungsten oxide on copper surfaces by electroless deposition Chemistry of Materials 2003; 15 (18): 3411-3413
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Combinatorial electrochemical synthesis and characterization of tungsten-based mixed-metal oxides
JOURNAL OF COMBINATORIAL CHEMISTRY
2002; 4 (6): 563-568
Abstract
Automated systems for electrochemical synthesis and high-throughput screening of photoelectrochemical materials were developed and used to prepare tungsten-based mixed-metal oxides, W(n)O(m)M(x) [M = Ni, Co, Cu, Zn, Pt, Ru, Rh, Pd, and Ag], specifically for hydrogen production by photoelectrolysis of water. Two-dimensional arrays (libraries) of diverse metal oxides were synthesized by automated cathodic electrodeposition of the oxides on Ti foil substrates. Electrolytes for the mixed oxides were prepared from various metal salts added to a solution containing tungsten stabilized as a peroxo complex. Electrodeposition of the peroxo-stabilized cations gave rise to three distinguishable oxide groups: (1) mixed-metal oxides [Ni], (2) metal-doped tungsten oxides [Pt, Ru, Rh, Pd, Ag], and (3) metal-metal oxide composites [Co, Cu, Zn]. The oxides typically showed n-type semiconducting behavior. Automated measurement of photocurrent using a scanning photoelectrochemical cell showed the W-Ni mixed oxide had the largest relative zero bias photocurrent, particularly at a low Ni concentration (5-10 atomic percent Ni). Pt and Ru were also found to increase the photoactivity of bulk tungsten oxide at relatively low concentrations; however, at concentrations above 5 atomic percent, crystallization of WO(3) was inhibited and photoactivity was diminished. Addition of Co, Cu, and Zn to WO(3) was not found to improve the photoelectrochemical activity.
View details for DOI 10.1021/cc020014w
View details for Web of Science ID 000179254700006
View details for PubMedID 12425600
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Controlled electrodeposition of nanoparticulate tungsten oxide
NANO LETTERS
2002; 2 (8): 831-834
View details for DOI 10.1021/nl025587p
View details for Web of Science ID 000177485500008
- Influence of composition and morphology on photo and electrocatalytic activity of electrodeposited Pt/WO3 2002
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High-throughput screening system for catalytic hydrogen-producing materials
JOURNAL OF COMBINATORIAL CHEMISTRY
2002; 4 (1): 17-22
Abstract
A high-throughput screening system and methodology were developed for libraries of hydrogen (H(2)) producing catalytic materials. The system is based on the chemo-optical properties of WO(3), which give rise to reflectance changes in the presence of H(2). Pd-coated WO(3) sensors were synthesized and examined for their hydrogen sensitivity, wavelength-dependent reflectance, and performance in the presence of water vapor. For high-throughput screening, a polypropylene reactor block was designed and constructed to house 8 x 12 catalyst libraries deposited as thin films. When the library and reactor block are assembled together, 96 independent microreactor units are formed. A large-area Pd/WO(3) sensor film covers and seals all microreactors, forming a 96-element 2-D H(2) sensor array. As H(2) is produced differentially across the library, the reflectance changes of the Pd/WO(3) film are monitored by reflectivity sensors that scan the surface every 30 s. The time-dependent changes in reflectance indicate relative rates of H(2) production. A library of cathode electrocatalysts was synthesized from Ti, Pt, Ni, Au, Pd, Al, Ag, Ge, and mixtures thereof to demonstrate the H(2) high-throughput screening system. The results of the electrolytic screening are in agreement with expected literature trends: mixtures of Ni and samples containing Pt and Pd generated H(2) at the greatest rates, while Ge- and Ti-based materials were the least effective electrocatalysts. A mixture of 80% Al and 20% Pt was found to have the highest rate of H(2) production. This high-throughput screening system is applicable in a variety of catalytic screening applications where hydrogen is the desired product.
View details for DOI 10.1021/cc010054k
View details for Web of Science ID 000174085200002
View details for PubMedID 11831878
- Controlled electrodeposition of nanoparticulate tungsten oxide Nano Letters 2002; 2 (8): 831-834
- Combinatorial electrochemical synthesis and characterization of tungsten-based mixed metal oxides Journal of Combinatorial Chemistry 2002; 4 (6): 563-568
- High-throughput screening system for catalytic hydrogen-producing materials Journal of Combinatorial Chemistry 2002; 4 (1): 17-22
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Automated synthesis and characterization of diverse libraries of macroporous alumina
ELECTROCHIMICA ACTA
2001; 47 (4): 553-557
View details for Web of Science ID 000172385400003
- Automated synthesis and characterization of diverse libraries of macroporous alumina Electrochimica Acta 2001; 47 (4): 553-557
- The Investigation of Photoelectrochemical Hydrogen Production Using Combinatorial Chemistry 2000