Frank Abild-Pedersen
Senior Scientist, SLAC National Accelerator Laboratory
Bio
Dr. Abild-Pedersen is the co-director of SUNCAT Center for Interface Science and Catalysis. He is leading a research team that focuses on developing an understanding of the factors determining the catalytic properties at the interface between gas/solvent and solid surfaces and to apply these insights to processes and catalysts of importance for energy transformations and for sustainable chemical production. His research takes advantage of computer facilities at SLAC and Stanford to gain the necessary understanding and to link these simulations to experiments where new catalyst synthesis methods are developed, and the catalyst materials are characterized both in terms of performance (activity, selectivity, durability, etc.) and in terms of geometrical and electronic structure. The underlying philosophy of his research is that by having a fundamental understanding of the way surfaces catalyze a chemical reaction we can make a quantum leap in our ability to make predictions for new catalysts and processes. This requires the development of a theory of heterogeneous catalysis, including electrocatalysis, based on computational and experimental results.
Dr Abild-Pedersen has extensive experience with simulations and modeling of chemical reactions. His work began with the derivation of energy correlations in catalysis that have helped speed up screening for active, selective and stable catalysts for energy conversion as a graduate student working with Professor Jens K. Nørskov at the Technical University of Denmark. He moved to SLAC in 2010 as a staff scientist and helped build up SUNCAT and define research directions in the field of heterogeneous catalysis.
Education & Certifications
-
PhD, Technical University of Denmark, Physics (2005)
Contact
https://orcid.org/0000-0002-1911-074XAll Publications
-
Oxidizing Role of Cu Cocatalysts in Unassisted Photocatalytic CO2Reduction Using p-GaN/Al2O3/Au/Cu Heterostructures.
ACS nano
2024
Abstract
Photocatalytic CO2 reduction to CO under unassisted (unbiased) conditions was recently demonstrated using heterostructure catalysts that combine p-type GaN with plasmonic Au nanoparticles and Cu nanoparticles as cocatalysts (p-GaN/Al2O3/Au/Cu). Here, we investigate the mechanistic role of Cu in p-GaN/Al2O3/Au/Cu under unassisted photocatalytic operating conditions using Cu K-edge X-ray absorption spectroscopy and first-principles calculations. Upon exposure to gas-phase CO2 and H2O vapor reaction conditions, the composition of the Cu nanoparticles is identified as a mixture of CuI and CuII oxide, hydroxide, and carbonate compounds without metallic Cu. These composition changes, indicating oxidative conditions, are rationalized by bulk Pourbaix thermodynamics. Under photocatalytic operating conditions with visible light excitation of the plasmonic Au nanoparticles, further oxidation of CuI to CuII is observed, indicating light-driven hole transfer from Au-to-Cu. This observation is supported by the calculated band alignments of the oxidized Cu compositions with plasmonic Au particles, where light-driven hole transfer from Au-to-Cu is found to be thermodynamically favored. These findings demonstrate that under unassisted (unbiased) gas-phase reaction conditions, Cu is found in carbonate-rich oxidized compositions rather than metallic Cu. These species then act as the active cocatalyst and play an oxidative rather than a reductive role in catalysis when coupled with plasmonic Au particles for light absorption, possibly opening an additional channel for water oxidation in this system.
View details for DOI 10.1021/acsnano.4c02088
View details for PubMedID 39037113
-
Coverage, repulsion, and reactivity of hydrogen on High-Entropy alloys
JOURNAL OF CATALYSIS
2024; 435
View details for DOI 10.1016/j.jcat.2024.115570
View details for Web of Science ID 001247947800001
-
Application of machine learning to discover new intermetallic catalysts for the hydrogen evolution and the oxygen reduction reactions
CATALYSIS SCIENCE & TECHNOLOGY
2024
View details for DOI 10.1039/d4cy00491d
View details for Web of Science ID 001243190900001
-
Prediction of Feasibility of Polaronic OER on the (110) Surface of Rutile TiO2.
Chemphyschem : a European journal of chemical physics and physical chemistry
2024; 25 (11): e202400523
Abstract
The front cover artwork is provided by Dr. Hori Pada Sarker from Dr. Frank Abild-Pedersen's research group at the SLAC National Accelerator Laboratory. The image shows the generation of photoexcited carriers (electrons and holes) and the subsequent formation of hole polaron in rutile TiO2 during oxygen evolution reaction (OER). Read the full text of the Research Article at 10.1002/cphc.202400060.
View details for DOI 10.1002/cphc.202400523
View details for PubMedID 38837603
-
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
-
Prediction of O and OH Adsorption on Transition Metal Oxide Surfaces from Bulk Descriptors
ACS CATALYSIS
2024
View details for DOI 10.1021/acscatal.4c00111
View details for Web of Science ID 001191165700001
-
Revealing Local and Directional Aspects of Catalytic Active Sites by the Nuclear and Surface Electrostatic Potential
JOURNAL OF PHYSICAL CHEMISTRY C
2024; 128 (11): 4544-4558
View details for DOI 10.1021/acs.jpcc.3c08512
View details for Web of Science ID 001183871200001
-
Prediction of Feasibility of Polaronic OER on (110) Surface of Rutile TiO2.
Chemphyschem : a European journal of chemical physics and physical chemistry
2024: e202400060
Abstract
The polaronic effects at the atomic level hold paramount significance for advancing the efficacy of transition metal oxides in applications pertinent to renewable energy. The lattice-distortion mediated localization of photoexcited carriers in the form of polarons plays a pivotal role in the photocatalysis. By employing Hubbard-U corrected and hybrid density functional theory (DFT) methods, we systematically probe the polaronic effects in the catalysis of oxygen evolution reaction (OER) on the (110) surface of rutile TiO2 photocatalyst. Theoretical understanding of polarons within the surface, coupled with simulations of OER at distinct titanium (Ti) and oxygen (O) active sites, reveals diverse polaron formation energies with strong preference for bulk and surface bridge oxygen sites. Moreover, we provide the evidence for the facilitative role of polarons in OER. We find that hole polarons situated at subsurface, equatorial, and bridge site significantly reduce the Ti-active site OER overpotential by ~0.4 eV through the peroxo-oxygen pathway. We also observe that the presence of hole polarons stabilizes the *OH, *O, and *OOH intermediate species. Overall, this study provides a detailed mechanistic insight into polaron-mediated OER, offering a promising avenue for improving the catalytic activity of transition metal oxide-based photocatalysts.
View details for DOI 10.1002/cphc.202400060
View details for PubMedID 38427793
-
A First-Principles Approach to Modeling Surface Site Stabilities on Multimetallic Catalysts
ACS CATALYSIS
2024; 14 (2): 874-885
View details for DOI 10.1021/acscatal.3c04337
View details for Web of Science ID 001146459100001
-
Interpretable design of Ir-free trimetallic electrocatalysts for ammonia oxidation with graph neural networks (vol 14, 792, 2023)
NATURE COMMUNICATIONS
2023; 14 (1): 950
View details for DOI 10.1038/s41467-023-36746-z
View details for Web of Science ID 001164830900027
View details for PubMedID 36805611
View details for PubMedCentralID PMC9941106
-
Classification of Adsorbed Hydrocarbons Based on Bonding Configurations of the Adsorbates and Surface Site Stabilities
ACS CATALYSIS
2023: 13663-13671
View details for DOI 10.1021/acscatal.3c03239
View details for Web of Science ID 001082678300001
-
A Comparative Study of Electrical Double Layer Effects for CO Reduction Reaction Kinetics
JOURNAL OF PHYSICAL CHEMISTRY C
2023
View details for DOI 10.1021/acs.jpcc.3c02953
View details for Web of Science ID 001051341600001
-
Dynamic and reversible transformations of subnanometre-sized palladium on ceria for efficient methane removal
NATURE CATALYSIS
2023
View details for DOI 10.1038/s41929-023-00983-8
View details for Web of Science ID 001033754800001
-
Assessing catalytic rates of bimetallic nanoparticles with active-site specificity: A case study using NO decomposition
CHEM CATALYSIS
2023; 3 (5)
View details for DOI 10.1016/j.checat.2023.100636
View details for Web of Science ID 001001413600001
-
Toward Carbon Monoxide Methanation at Mild Conditions on Dual-Site Catalysts.
Journal of the American Chemical Society
2023
Abstract
The catalytic carbon monoxide (CO) methanation is an ideal model reaction for the fundamental understanding of catalysis on the gas-solid interface and is crucial for various industrial processes. However, the harsh operating conditions make the reaction unsustainable, and the limitations set by the scaling relations between the dissociation energy barrier and dissociative binding energy of CO further increase the difficulty in designing high-performance methanation catalysts operating under milder conditions. Herein, we proposed a theoretical strategy to circumvent the limitations elegantly and achieve both facile CO dissociation and C/O hydrogenation on the catalyst containing a confined dual site. The DFT-based microkinetic modeling (MKM) reveals that the designed Co-Cr2/G dual-site catalyst could provide 4-6 orders of magnitude higher turnover frequency for CH4 production than the cobalt step sites. We believe that the proposed strategy in the current work will provide essential guidance for designing state-of-the-art methanation catalysts under mild conditions.
View details for DOI 10.1021/jacs.3c02180
View details for PubMedID 37017464
-
X-ray free electron laser studies of electron and phonon dynamics of graphene adsorbed on copper
PHYSICAL REVIEW MATERIALS
2023; 7 (2)
View details for DOI 10.1103/PhysRevMaterials.7.024005
View details for Web of Science ID 000943101300002
-
Interpretable design of Ir-free trimetallic electrocatalysts for ammonia oxidation with graph neural networks.
Nature communications
2023; 14 (1): 792
Abstract
The electrochemical ammonia oxidation to dinitrogen as a means for energy and environmental applications is a key technology toward the realization of a sustainable nitrogen cycle. The state-of-the-art metal catalysts including Pt and its bimetallics with Ir show promising activity, albeit suffering from high overpotentials for appreciable current densities and the soaring price of precious metals. Herein, the immense design space of ternary Pt alloy nanostructures is explored by graph neural networks trained on ab initio data for concurrently predicting site reactivity, surface stability, and catalyst synthesizability descriptors. Among a few Ir-free candidates that emerge from the active learning workflow, Pt3Ru-M (M: Fe, Co, or Ni) alloys were successfully synthesized and experimentally verified to be more active toward ammonia oxidation than Pt, Pt3Ir, and Pt3Ru. More importantly, feature attribution analyses using the machine-learned representation of site motifs provide fundamental insights into chemical bonding at metal surfaces and shed light on design strategies for high-performance catalytic systems beyond the d-band center metric of binding sites.
View details for DOI 10.1038/s41467-023-36322-5
View details for PubMedID 36774355
-
Colloidally Engineered Pd and Pt Catalysts Distinguish Surface- and Vapor-Mediated Deactivation Mechanisms
ACS CATALYSIS
2023
View details for DOI 10.1021/acscatal.2c04683
View details for Web of Science ID 000921989700001
-
Atom-Specific Probing of Electron Dynamics in an Atomic Adsorbate by Time-Resolved X-Ray Spectroscopy.
Physical review letters
2022; 129 (27): 276001
Abstract
The electronic excitation occurring on adsorbates at ultrafast timescales from optical lasers that initiate surface chemical reactions is still an open question. Here, we report the ultrafast temporal evolution of x-ray absorption spectroscopy (XAS) and x-ray emission spectroscopy (XES) of a simple well-known adsorbate prototype system, namely carbon (C) atoms adsorbed on a nickel [Ni(100)] surface, following intense laser optical pumping at 400 nm. We observe ultrafast (∼100 fs) changes in both XAS and XES showing clear signatures of the formation of a hot electron-hole pair distribution on the adsorbate. This is followed by slower changes on a few picoseconds timescale, shown to be consistent with thermalization of the complete C/Ni system. Density functional theory spectrum simulations support this interpretation.
View details for DOI 10.1103/PhysRevLett.129.276001
View details for PubMedID 36638285
-
Symmetry-resolved CO desorption and oxidation dynamics on O/Ru(0001) probed at the C K-edge by ultrafast x-ray spectroscopy
JOURNAL OF CHEMICAL PHYSICS
2022; 157 (16): 164705
Abstract
We report on carbon monoxide desorption and oxidation induced by 400 nm femtosecond laser excitation on the O/Ru(0001) surface probed by time-resolved x-ray absorption spectroscopy (TR-XAS) at the carbon K-edge. The experiments were performed under constant background pressures of CO (6 × 10-8 Torr) and O2 (3 × 10-8 Torr). Under these conditions, we detect two transient CO species with narrow 2π* peaks, suggesting little 2π* interaction with the surface. Based on polarization measurements, we find that these two species have opposing orientations: (1) CO favoring a more perpendicular orientation and (2) CO favoring a more parallel orientation with respect to the surface. We also directly detect gas-phase CO2 using a mass spectrometer and observe weak signatures of bent adsorbed CO2 at slightly higher x-ray energies than the 2π* region. These results are compared to previously reported TR-XAS results at the O K-edge, where the CO background pressure was three times lower (2 × 10-8 Torr) while maintaining the same O2 pressure. At the lower CO pressure, in the CO 2π* region, we observed adsorbed CO and a distribution of OC-O bond lengths close to the CO oxidation transition state, with little indication of gas-like CO. The shift toward "gas-like" CO species may be explained by the higher CO exposure, which blocks O adsorption, decreasing O coverage and increasing CO coverage. These effects decrease the CO desorption barrier through dipole-dipole interaction while simultaneously increasing the CO oxidation barrier.
View details for DOI 10.1063/5.0114399
View details for Web of Science ID 000876502600007
View details for PubMedID 36319417
-
Electronic structure factors and the importance of adsorbate effects in chemisorption on surface alloys
NPJ COMPUTATIONAL MATERIALS
2022; 8 (1)
View details for DOI 10.1038/s41524-022-00846-z
View details for Web of Science ID 000834816700001
-
Screening binary alloys for electrochemical CO2 reduction towards multi-carbon products
JOURNAL OF MATERIALS CHEMISTRY A
2022
View details for DOI 10.1039/d2ta02749f
View details for Web of Science ID 000827062500001
-
Unraveling Electronic Trends in O* and OH* Surface Adsorption in the MO2 Transition-Metal Oxide Series
JOURNAL OF PHYSICAL CHEMISTRY C
2022; 126 (18): 7903-7909
View details for DOI 10.1021/acs.jpcc.2c02381
View details for Web of Science ID 000800028300011
-
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
-
Catalytic Performance and Near-Surface X-ray Characterization of Titanium Hydride Electrodes for the Electrochemical Nitrate Reduction Reaction.
Journal of the American Chemical Society
2022
Abstract
The electrochemical nitrate reduction reaction (NO3RR) on titanium introduces significant surface reconstruction and forms titanium hydride (TiHx, 0 < x ≤ 2). With ex situ grazing-incidence X-ray diffraction (GIXRD) and X-ray absorption spectroscopy (XAS), we demonstrated near-surface TiH2 enrichment with increasing NO3RR applied potential and duration. This quantitative relationship facilitated electrochemical treatment of Ti to form TiH2/Ti electrodes for use in NO3RR, thereby decoupling hydride formation from NO3RR performance. A wide range of NO3RR activity and selectivity on TiH2/Ti electrodes between -0.4 and -1.0 VRHE was observed and analyzed with density functional theory (DFT) calculations on TiH2(111). This work underscores the importance of relating NO3RR performance with near-surface electrode structure to advance catalyst design and operation.
View details for DOI 10.1021/jacs.2c01274
View details for PubMedID 35315649
-
Trends in oxygenate/hydrocarbon selectivity for electrochemical CO(2) reduction to C2 products.
Nature communications
2022; 13 (1): 1399
Abstract
The electrochemical conversion of carbon di-/monoxide into commodity chemicals paves a way towards a sustainable society but it also presents one of the great challenges in catalysis. Herein, we present the trends in selectivity towards specific dicarbon oxygenate/hydrocarbon products from carbon monoxide reduction on transition metal catalysts, with special focus on copper. We unveil the distinctive role of electrolyte pH in tuning the dicarbon oxygenate/hydrocarbon selectivity. The understanding is based on density functional theory calculated energetics and microkinetic modeling. We identify the critical reaction steps determining selectivity and relate their transition state energies to two simple descriptors, the carbon and hydroxide binding strengths. The atomistic insight gained enables us to rationalize a number of experimental observations and provides avenues towards the design of selective electrocatalysts for liquid fuel production from carbon di-/monoxide.
View details for DOI 10.1038/s41467-022-29140-8
View details for PubMedID 35302055
-
Vernier template synthesis of molecular knots.
Science (New York, N.Y.)
2022; 375 (6584): 1035-1041
Abstract
Molecular knots are often prepared using metal helicates to cross the strands. We found that coordinatively mismatching oligodentate ligands and metal ions provides a more effective way to synthesize larger knots using Vernier templating. Strands composed of different numbers of tridentate 2,6-pyridinedicarboxamide groups fold around nine-coordinate lanthanide (III) ions to generate strand-entangled complexes with the lowest common multiple of coordination sites for the ligand strands and metal ions. Ring-closing olefin metathesis then completes the knots. A 3:2 (ditopic strand:metal) Vernier assembly produces +31#+31 and -31#-31 granny knots. Vernier complexes of 3:4 (tetratopic strand:metal) stoichiometry selectively form a 378-atom-long trefoil-of-trefoils triskelion knot with 12 alternating strand crossings or, by using opposing stereochemistry at the terminus of the strand, an inverted-core triskelion knot with six alternating and six nonalternating strand crossings.
View details for DOI 10.1126/science.abm9247
View details for PubMedID 35239374
-
Microkinetic Modeling of Propene Combustion on a Stepped, Metallic Palladium Surface and the Importance of Oxygen Coverage
ACS CATALYSIS
2022
View details for DOI 10.1021/acscatal.1c03699
View details for Web of Science ID 000746621700001
-
Colloidal Platinum-Copper Nanocrystal Alloy Catalysts Surpass Platinum in Low-Temperature Propene Combustion.
Journal of the American Chemical Society
2022
Abstract
Low-temperature removal of noxious environmental emissions plays a critical role in minimizing the harmful effects of hydrocarbon fuels. Emission-control catalysts typically consist of large quantities of rare, noble metals (e.g., platinum and palladium), which are expensive and environmentally damaging metals to extract. Alloying with cheaper base metals offers the potential to boost catalytic activity while optimizing the use of noble metals. In this work, we show that PtxCu100-x catalysts prepared from colloidal nanocrystals are more active than the corresponding Pt catalysts for complete propene oxidation. By carefully controlling their composition while maintaining nanocrystal size, alloys with dilute Cu concentrations (15-30% atomic fraction) demonstrate promoted activity compared to pure Pt. Complete propene oxidation was observed at temperatures as low as 150 °C in the presence of steam, and five to ten times higher turnover frequencies were found compared to monometallic Pt catalysts. Through DFT studies and structural and catalytic characterization, the remarkable activity of dilute PtxCu100-x alloys was related to the tuning of the electronic structure of Pt to reach optimal binding energies of C* and O* intermediates. This work provides a general approach toward investigation of structure-property relationships of alloyed catalysts with efficient and optimized use of noble metals.
View details for DOI 10.1021/jacs.1c10248
View details for PubMedID 35050603
-
Exploring Trends on Coupling Mechanisms toward C-3 Product Formation in CO(2)R
JOURNAL OF PHYSICAL CHEMISTRY C
2021; 125 (48): 26437-26447
View details for DOI 10.1021/acs.jpcc.1c07553
View details for Web of Science ID 000752819300018
-
Modeling Potential-Dependent Electrochemical Activation Barriers: Revisiting the Alkaline Hydrogen Evolution Reaction.
Journal of the American Chemical Society
2021
Abstract
Accurate theoretical simulation of electrochemical activation barriers is key to understanding electrocatalysis and guides the design of more efficient catalysts. Providing a detailed picture of proton transfer processes encounters several challenges: the constant potential requirement during charge transfer, the different time scales involved in the processes, and the thermal fluctuation of the solvent. Hence, it is prohibitively expensive computationally to apply density functional theory (DFT) calculations in modeling the potential-dependent activation barrier at the electrode-solvent interface, and the results are dubious. To address these challenges, we have developed an analytical approach based on charge conservation and decoupled potential energy surfaces to compute charge transfer barriers. The method makes it possible to simulate an electrochemical process at different potentials and explicitly include thermal fluctuations of the solvent at the electrode-solvent interface. We use the Pt-catalyzed alkaline hydrogen evolution reaction (HER) as our benchmark reaction, and we model the microkinetics of HER with consideration of the spatial fluctuations between the metal surface and the first solvent layer at room temperature. The distribution of water-metal distances has a large effect on the barriers of the charge transfer processes, and an accurate account of the statistical fluctuation in the reaction network leads to a several orders of magnitude increase in HER current as compared to transfer from a static solvent. The trends of the different reaction mechanisms in HER were successfully simulated with our model, and the theoretical I-V curves obtained are in good qualitative agreement with experimental results.
View details for DOI 10.1021/jacs.1c07276
View details for PubMedID 34752077
-
Combining artificial intelligence and physics-based modeling to directly assess atomic site stabilities: from sub-nanometer clusters to extended surfaces.
Physical chemistry chemical physics : PCCP
2021
Abstract
The performance of functional materials is dictated by chemical and structural properties of individual atomic sites. In catalysts, for example, the thermodynamic stability of constituting atomic sites is a key descriptor from which more complex properties, such as molecular adsorption energies and reaction rates, can be derived. In this study, we present a widely applicable machine learning (ML) approach to instantaneously compute the stability of individual atomic sites in structurally and electronically complex nano-materials. Conventionally, we determine such site stabilities using computationally intensive first-principles calculations. With our approach, we predict the stability of atomic sites in sub-nanometer metal clusters of 3-55 atoms with mean absolute errors in the range of 0.11-0.14 eV. To extract physical insights from the ML model, we introduce a genetic algorithm (GA) for feature selection. This algorithm distills the key structural and chemical properties governing the stability of atomic sites in size-selected nanoparticles, allowing for physical interpretability of the models and revealing structure-property relationships. The results of the GA are generally model and materials specific. In the limit of large nanoparticles, the GA identifies features consistent with physics-based models for metal-metal interactions. By combining the ML model with the physics-based model, we predict atomic site stabilities in real time for structures ranging from sub-nanometer metal clusters (3-55 atom) to larger nanoparticles (147 to 309 atoms) to extended surfaces using a physically interpretable framework. Finally, we present a proof of principle showcasing how our approach can determine stable and active nanocatalysts across a generic materials space of structure and composition.
View details for DOI 10.1039/d1cp02198b
View details for PubMedID 34570139
-
The Role of Roughening to Enhance Selectivity to C2+ Products during CO2 Electroreduction on Copper
ACS ENERGY LETTERS
2021; 6 (9): 3252-3260
View details for DOI 10.1021/acsenergylett.1c01485
View details for Web of Science ID 000696180500027
-
Insights and comparison of structure-property relationships in propane and propene catalytic combustion on Pd- and Pt-based catalysts
JOURNAL OF CATALYSIS
2021; 401: 89-101
View details for DOI 10.1016/j.jcat.2021.06.018
View details for Web of Science ID 000691545800010
-
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
-
Achieving industrial ammonia synthesis rates at near-ambient conditions through modified scaling relations on a confined dual site.
Proceedings of the National Academy of Sciences of the United States of America
2021; 118 (30)
Abstract
The production of ammonia through the Haber-Bosch process is regarded as one of the most important inventions of the 20th century. Despite significant efforts in optimizing the process, it still consumes 1 to 2% of the worldwide annual energy for the high working temperatures and pressures. The design of a catalyst with a high activity at milder conditions represents another challenge for this reaction. Herein, we combine density functional theory and microkinetic modeling to illustrate a strategy to facilitate low-temperature and -pressure ammonia synthesis through modified energy-scaling relationships using a confined dual site. Our results suggest that an ammonia synthesis rate two to three orders of magnitude higher than the commercial Ru catalyst can be achieved under the same reaction conditions with the introduction of confinement. Such strategies will open pathways for the development of catalysts for the Haber-Bosch process that can operate at milder conditions and present more economically viable alternatives to current industrial solutions.
View details for DOI 10.1073/pnas.2106527118
View details for PubMedID 34282023
-
Identifying factors controlling the selective ethane dehydrogenation on Pt-based catalysts from DFT based micro-kinetic modeling
JOURNAL OF ENERGY CHEMISTRY
2021; 58: 37–40
View details for DOI 10.1016/j.jechem.2020.09.034
View details for Web of Science ID 000640209900005
-
Theory-Aided Discovery of Metallic Catalysts for Selective Propane Dehydrogenation to Propylene
ACS CATALYSIS
2021; 11 (10): 6290-6297
View details for DOI 10.1021/acscatal.0c05711
View details for Web of Science ID 000656056200039
-
Identification of earth-abundant materials for selective dehydrogenation of light alkanes to olefins.
Proceedings of the National Academy of Sciences of the United States of America
2021; 118 (11)
Abstract
Selective ethane dehydrogenation (EDH) is an attractive on-purpose strategy for industrial ethylene production. Design of an effective, stable, and earth-abundant catalyst to replace noble metal Pt is the main obstacle for its large-scale application. Herein, we report an experimentally validated theoretical framework to discover promising catalysts for EDH, which combines descriptor-based microkinetic modeling, high-throughput computations, machine-learning concepts, and experiments. Our approach efficiently evaluates 1,998 bimetallic alloys by using accurately calculated C and CH3 adsorption energies and identifies a small number of new promising noble-metal-free catalysts for selective EDH. A Ni3Mo alloy predicted to be promising is successfully synthesized, and experimentally proven to outperform Pt in selective ethylene production from EDH, representing an important contribution to the improvement of light alkane dehydrogenation to olefins. These results will provide essential additions in the discovery and application of earth-abundant materials in catalysis.
View details for DOI 10.1073/pnas.2024666118
View details for PubMedID 33712546
-
The role of atomic carbon in directing electrochemical CO(2) reduction to multicarbon products
ENERGY & ENVIRONMENTAL SCIENCE
2021; 14 (1): 473–82
View details for DOI 10.1039/d0ee02826f
View details for Web of Science ID 000611850000025
-
Ultrafast Adsorbate Excitation Probed with Subpicosecond-Resolution X-Ray Absorption Spectroscopy.
Physical review letters
2021; 127 (1): 016802
Abstract
We use a pump-probe scheme to measure the time evolution of the C K-edge x-ray absorption spectrum from CO/Ru(0001) after excitation by an ultrashort high-intensity optical laser pulse. Because of the short duration of the x-ray probe pulse and precise control of the pulse delay, the excitation-induced dynamics during the first picosecond after the pump can be resolved with unprecedented time resolution. By comparing with density functional theory spectrum calculations, we find high excitation of the internal stretch and frustrated rotation modes occurring within 200 fs of laser excitation, as well as thermalization of the system in the picosecond regime. The ∼100 fs initial excitation of these CO vibrational modes is not readily rationalized by traditional theories of nonadiabatic coupling of adsorbates to metal surfaces, e.g., electronic frictions based on first order electron-phonon coupling or transient population of adsorbate resonances. We suggest that coupling of the adsorbate to nonthermalized electron-hole pairs is responsible for the ultrafast initial excitation of the modes.
View details for DOI 10.1103/PhysRevLett.127.016802
View details for PubMedID 34270277
-
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
-
From electricity to fuels: Descriptors for C-1 selectivity in electrochemical CO2 reduction
APPLIED CATALYSIS B-ENVIRONMENTAL
2020; 279
View details for DOI 10.1016/j.apcatb.2020.119384
View details for Web of Science ID 000566452900011
-
Enhanced CO tolerance of Pt clusters supported on graphene with lattice vacancies
PHYSICAL REVIEW B
2020; 102 (7)
View details for DOI 10.1103/PhysRevB.102.075408
View details for Web of Science ID 000555319900006
-
Predicting metal-metal interactions. II. Accelerating generalized schemes through physical insights.
The Journal of chemical physics
2020; 152 (9): 094702
Abstract
Operando-computational frameworks that integrate descriptors for catalyst stability within catalyst screening paradigms enable predictions of rates and selectivity on chemically faithful representations of nanoparticles under reaction conditions. These catalyst stability descriptors can be efficiently predicted by density functional theory (DFT)-based models. The alloy stability model, for example, predicts the stability of metal atoms in nanoparticles with site-by-site resolution. Herein, we use physical insights to present accelerated approaches of parameterizing this recently introduced alloy-stability model. These accelerated approaches meld quadratic functions for the energy of metal atoms in terms of the coordination number with linear correlations between model parameters and the cohesive energies of bulk metals. By interpolating across both the coordination number and chemical space, these accelerated approaches shrink the training set size for 12 fcc p- and d-block metals from 204 to as few as 24 DFT calculated total energies without sacrificing the accuracy of our model. We validate the accelerated approaches by predicting adsorption energies of metal atoms on extended surfaces and 147 atom cuboctahedral nanoparticles with mean absolute errors of 0.10 eV and 0.24 eV, respectively. This efficiency boost will enable a rapid and exhaustive exploration of the vast material space of transition metal alloys for catalytic applications.
View details for DOI 10.1063/1.5141378
View details for PubMedID 33480718
-
Predicting metal-metal interactions. I. The influence of strain on nanoparticle and metal adlayer stabilities
JOURNAL OF CHEMICAL PHYSICS
2020; 152 (9)
View details for DOI 10.1063/1.5130566
View details for Web of Science ID 000519108300001
-
Predicting metal-metal interactions. II. Accelerating generalized schemes through physical insights
JOURNAL OF CHEMICAL PHYSICS
2020; 152 (9)
View details for DOI 10.1063/1.5141378
View details for Web of Science ID 000519108300002
-
Predicting metal-metal interactions. I. The influence of strain on nanoparticle and metal adlayer stabilities.
The Journal of chemical physics
2020; 152 (9): 094701
Abstract
Strain-engineering of bimetallic nanomaterials is an important design strategy for developing new catalysts. Herein, we introduce an approach for including strain effects into a recently introduced, density functional theory (DFT)-based alloy stability model. The model predicts adsorption site stabilities in nanoparticles and connects these site stabilities with catalytic reactivity and selectivity. Strain-based dependencies will increase the model's accuracy for nanoparticles affected by finite-size effects. In addition to the stability of small nanoparticles, strain also influences the heat of adsorption of epitaxially grown metal-on-metal adlayers. In this respect, we successfully benchmark the strain-including alloy stability model with previous experimentally determined trends in the heats of adsorption of Au and Cu adlayers on Pt (111). For these systems, our model predicts stronger bimetallic interactions in the first monolayer than monometallic interactions in the second monolayer. We explicitly quantify the interplay between destabilizing strain effects and the energy gained by forming new metal-metal bonds. While tensile strain in the first Cu monolayer significantly destabilizes the adsorption strength, compressive strain in the first Au monolayer has a minimal impact on the heat of adsorption. Hence, this study introduces and, by comparison with previous experiments, validates an efficient DFT-based approach for strain-engineering the stability, and, in turn, the catalytic performance, of active sites in bimetallic alloys with atomic level resolution.
View details for DOI 10.1063/1.5130566
View details for PubMedID 33480713
-
Revealing the structure of a catalytic combustion active-site ensemble combining uniform nanocrystal catalysts and theory insights.
Proceedings of the National Academy of Sciences of the United States of America
2020
Abstract
Supported metal catalysts are extensively used in industrial and environmental applications. To improve their performance, it is crucial to identify the most active sites. This identification is, however, made challenging by the presence of a large number of potential surface structures that complicate such an assignment. Often, the active site is formed by an ensemble of atoms, thus introducing further complications in its identification. Being able to produce uniform structures and identify the ones that are responsible for the catalyst performance is a crucial goal. In this work, we utilize a combination of uniform Pd/Pt nanocrystal catalysts and theory to reveal the catalytic active-site ensemble in highly active propene combustion materials. Using colloidal chemistry to exquisitely control nanoparticle size, we find that intrinsic rates for propene combustion in the presence of water increase monotonically with particle size on Pt-rich catalysts, suggesting that the reaction is structure dependent. We also reveal that water has a near-zero or mildly positive reaction rate order over Pd/Pt catalysts. Theory insights allow us to determine that the interaction of water with extended terraces present in large particles leads to the formation of step sites on metallic surfaces. These specific step-edge sites are responsible for the efficient combustion of propene at low temperature. This work reveals an elusive geometric ensemble, thus clearly identifying the active site in alkene combustion catalysts. These insights demonstrate how the combination of uniform catalysts and theory can provide a much deeper understanding of active-site geometry for many applications.
View details for DOI 10.1073/pnas.2002342117
View details for PubMedID 32554500
-
Catalyst deactivation via decomposition into single atoms and the role of metal loading
NATURE CATALYSIS
2019; 2 (9): 748–55
View details for DOI 10.1038/s41929-019-0328-1
View details for Web of Science ID 000486144700006
-
Single-atom species determine the deactivation of supported catalysts
AMER CHEMICAL SOC. 2019
View details for Web of Science ID 000525055502294
-
Machine Learning for Computational Heterogeneous Catalysis
CHEMCATCHEM
2019; 11 (16): 3579–99
View details for DOI 10.1002/cctc.201900595
View details for Web of Science ID 000498036500004
-
Enhancing Electrocatalytic Water Splitting by Strain Engineering
ADVANCED MATERIALS
2019; 31 (17)
View details for DOI 10.1002/adma.201807001
View details for Web of Science ID 000465600000007
-
Predicting Adsorption Properties of Catalytic Descriptors on Bimetallic Nanoalloys with Site-Specific Precision
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
2019; 10 (8): 1852–59
View details for DOI 10.1021/acs.jpclett.9b00475
View details for Web of Science ID 000465507700030
-
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
-
Density-dependent deactivation mechanism in supported catalysts by high-temperature decomposition of particles into single atoms
AMER CHEMICAL SOC. 2019
View details for Web of Science ID 000478860502379
-
Uncovering the details of methane combustion on palladium catalysts using well-defined nanocrystal precursors
AMER CHEMICAL SOC. 2019
View details for Web of Science ID 000478860502176
-
A coordination-based model for transition metal alloy nanoparticles
NANOSCALE
2019; 11 (10): 4438–52
View details for DOI 10.1039/c9nr00959k
View details for Web of Science ID 000465410200028
-
Enhancing Electrocatalytic Water Splitting by Strain Engineering.
Advanced materials (Deerfield Beach, Fla.)
2019: e1807001
Abstract
Electrochemical water splitting driven by sustainable energy such as solar, wind, and tide is attracting ever-increasing attention for sustainable production of clean hydrogen fuel from water. Leveraging these advances requires efficient and earth-abundant electrocatalysts to accelerate the kinetically sluggish hydrogen and oxygen evolution reactions (HER and OER). A large number of advanced water-splitting electrocatalysts have been developed through recent understanding of the electrochemical nature and engineering approaches. Specifically, strain engineering offers a novel route to promote the electrocatalytic HER/OER performances for efficient water splitting. Herein, the recent theoretical and experimental progress on applying strain to enhance heterogeneous electrocatalysts for both HER and OER are reviewed and future opportunities are discussed. A brief introduction of the fundamentals of water-splitting reactions, and the rationalization for utilizing mechanical strain to tune an electrocatalyst is given, followed by a discussion of the recent advances on strain-promoted HER and OER, with special emphasis given to combined theoretical and experimental approaches for determining the optimal straining effect for water electrolysis, along with experimental approaches for creating and characterizing strain in nanocatalysts, particularly emerging 2D nanomaterials. Finally, a vision for a future sustainable hydrogen fuel community based on strain-promoted water electrolysis is proposed.
View details for PubMedID 30773741
-
Understanding Structure-Property Relationships of MoO3-Promoted Rh Catalysts for Syngas Conversion to Alcohols.
Journal of the American Chemical Society
2019
Abstract
Rh-based catalysts have shown promise for the direct conversion of syngas to higher oxygenates. Although improvements in higher oxygenate yield have been achieved by combining Rh with metal oxide promoters, details of the structure of the promoted catalyst and the role of the promoter in enhancing catalytic performance are not well understood. In this work, we show that MoO3-promoted Rh nanoparticles form a novel catalyst structure in which Mo substitutes into the Rh surface, leading to both a 66-fold increase in turnover frequency and an enhancement in oxygenate yield. By applying a combination of atomically controlled synthesis, in situ characterization, and theoretical calculations, we gain an understanding of the promoter-Rh interactions that govern catalytic performance for MoO3-promoted Rh. We use atomic layer deposition to modify Rh nanoparticles with monolayer-precise amounts of MoO3, with a high degree of control over the structure of the catalyst. Through in situ X-ray absorption spectroscopy, we find that the atomic structure of the catalytic surface under reaction conditions consists of Mo-OH species substituted into the surface of the Rh nanoparticles. Using density functional theory calculations, we identify two roles of MoO3: first, the presence of Mo-OH in the catalyst surface enhances CO dissociation and also stabilizes a methanol synthesis pathway not present in the unpromoted catalyst; and second, hydrogen spillover from Mo-OH sites to adsorbed species on the Rh surface enhances hydrogenation rates of reaction intermediates.
View details for DOI 10.1021/jacs.9b07460
View details for PubMedID 31724857
-
Accessing the C-C transition state energy on transition metals.
Physical chemistry chemical physics : PCCP
2019
Abstract
The search for catalysts that can efficiently convert large hydrocarbons has been an active area of research for decades. To gain insight into those reactions, electronic structure calculations are playing an increasing role but the screening efforts are impeded by the complexity of the reaction networks that can contain hundreds of elementary steps, presenting a large number of computationally expensive transition state barrier calculations. A large number of the sub reactions in the network involve C-C bond dissociation, a step that has been identified as rate determining in many studies. The purpose of this article is to present a methodology that allows for accurate and rapid assessment of transition state energies for C-C bond breaking in any hydrocarbon based on a small number of simple calculations. Our model significantly enhances the capability of expanding the search space for new and efficient catalysts.
View details for DOI 10.1039/c9cp04897a
View details for PubMedID 31701972
-
Supported Catalyst Deactivation by Decomposition into Single Atoms Is Suppressed by Increasing Metal Loading.
Nature catalysis
2019; 2
Abstract
In the high-temperature environments needed to perform catalytic processes, supported precious metal catalysts severely lose their activity over time. Even brief exposure to high temperatures can lead to significant losses in activity, which forces manufacturers to use large amounts of noble metals to ensure effective catalyst function for a required lifetime. Generally, loss of catalytic activity is attributed to nanoparticle sintering, or processes by which larger particles grow at the expense of smaller ones. Here, by independently controlling particle size and particle loading using colloidal nanocrystals, we reveal the opposite process as a novel deactivation mechanism: nanoparticles rapidly lose activity by high-temperature nanoparticle decomposition into inactive single atoms. This deactivation route is remarkably fast, leading to severe loss of activity in as little as ten minutes. Importantly, this deactivation pathway is strongly dependent on particle density and concentration of support defect sites. A quantitative statistical model explains how for certain reactions, higher particle densities can lead to more stable catalysts.
View details for DOI 10.1038/s41929-019-0328-1
View details for PubMedID 32118197
View details for PubMedCentralID PMC7047889
-
Theoretical and Experimental Studies of CoGa Catalysts for the Hydrogenation of CO2 to Methanol
CATALYSIS LETTERS
2018; 148 (12): 3583–91
View details for DOI 10.1007/s10562-018-2542-x
View details for Web of Science ID 000449257700001
-
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
-
Strongly Modified Scaling of CO Hydrogenation in Metal Supported TiO Nanostripes
ACS CATALYSIS
2018; 8 (11): 10555–63
View details for DOI 10.1021/acscatal.8b03327
View details for Web of Science ID 000449723900069
-
Mechanistic Insights into the Synthesis of Higher Alcohols from Syngas on CuCo Alloys
ACS CATALYSIS
2018; 8 (11): 10148–55
View details for DOI 10.1021/acscatal.8b01596
View details for Web of Science ID 000449723900026
-
Tuning Methane Activation Chemistry on Alkaline Earth Metal Oxides by Doping
JOURNAL OF PHYSICAL CHEMISTRY C
2018; 122 (39): 22544–48
View details for DOI 10.1021/acs.jpcc.8b06682
View details for Web of Science ID 000446926400035
-
Low-Temperature Methane Partial Oxidation to Syngas with Modular Nanocrystal Catalysts
ACS APPLIED NANO MATERIALS
2018; 1 (9): 5258–67
View details for DOI 10.1021/acsanm.8b01256
View details for Web of Science ID 000461401000092
-
Understanding and tuning catalytic materials using well-defined nanocrystal precursors
AMER CHEMICAL SOC. 2018
View details for Web of Science ID 000447600002371
-
Well-defined nanocrystals catalysts as active phases and premier materials for spectroscopic studies of catalyst restructuring
AMER CHEMICAL SOC. 2018
View details for Web of Science ID 000447600002061
-
Theoretical Investigation of Methane Oxidation on Pd(111) and Other Metallic Surfaces
JOURNAL OF PHYSICAL CHEMISTRY C
2018; 122 (28): 16023–32
View details for DOI 10.1021/acs.jpcc.8b02142
View details for Web of Science ID 000439661000026
-
Nature of Lone-Pair-Surface Bonds and Their Scaling Relations
INORGANIC CHEMISTRY
2018; 57 (12): 7222–38
View details for DOI 10.1021/acs.inorgchem.8b00902
View details for Web of Science ID 000436023800051
-
Structure-Sensitive Scaling Relations: Adsorption Energies from Surface Site Stability
CHEMCATCHEM
2018; 10 (7): 1643–50
View details for DOI 10.1002/cctc.201701841
View details for Web of Science ID 000430102400022
-
Selectivity of Synthesis Gas Conversion to C2+ Oxygenates on fcc(111) Transition-Metal Surfaces
ACS CATALYSIS
2018; 8 (4): 3447–53
View details for DOI 10.1021/acscata1.8b00201
View details for Web of Science ID 000430154100091
-
Understanding and tuning catalytic materials For methane activation using nanocrystal precursors
AMER CHEMICAL SOC. 2018
View details for Web of Science ID 000435537701819
-
Selective catalysts for higher alcohol synthesis: A combined DFT and micro-kinetic modeling study
AMER CHEMICAL SOC. 2018
View details for Web of Science ID 000435537702053
-
Mechanistic insights into the synthesis of higher alcohols from syngas on CuCo-alloys
AMER CHEMICAL SOC. 2018
View details for Web of Science ID 000435539900113
-
Understanding activity loss in precious-metal combustion catalysts using well-defined nanocrystals
AMER CHEMICAL SOC. 2018
View details for Web of Science ID 000435537702405
-
Generic approach to access barriers in dehydrogenation reactions
COMMUNICATIONS CHEMISTRY
2018; 1
View details for DOI 10.1038/s42004-017-0001-z
View details for Web of Science ID 000433892000002
-
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
-
Configurational Energies of Nanoparticles Based on Metal-Metal Coordination
JOURNAL OF PHYSICAL CHEMISTRY C
2017; 121 (41): 23002–10
View details for DOI 10.1021/acs.jpcc.7b08438
View details for Web of Science ID 000413617900043
-
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
-
Rh-MnO Interface Sites Formed by Atomic Layer Deposition Promote Syngas Conversion to Higher Oxygenates
ACS CATALYSIS
2017; 7 (9): 5746–57
View details for DOI 10.1021/acscatal.7b01851
View details for Web of Science ID 000410005700020
-
Theoretical Insights into Methane C-H Bond Activation on Alkaline Metal Oxides
JOURNAL OF PHYSICAL CHEMISTRY C
2017; 121 (30): 16440–46
View details for DOI 10.1021/acs.jpcc.7b05838
View details for Web of Science ID 000407189400038
-
A Theoretical Study of Methanol Oxidation on RuO2(110): Bridging the Pressure Gap
ACS CATALYSIS
2017; 7 (7): 4527–34
View details for DOI 10.1021/acscatal.7b01417
View details for Web of Science ID 000405360800040
-
Electrochemical generation of sulfur vacancies in the basal plane of MoS2 for hydrogen evolution
NATURE COMMUNICATIONS
2017; 8
Abstract
Recently, sulfur (S)-vacancies created on the basal plane of 2H-molybdenum disulfide (MoS2) using argon plasma exposure exhibited higher intrinsic activity for the electrochemical hydrogen evolution reaction than the edge sites and metallic 1T-phase of MoS2 catalysts. However, a more industrially viable alternative to the argon plasma desulfurization process is needed. In this work, we introduce a scalable route towards generating S-vacancies on the MoS2 basal plane using electrochemical desulfurization. Even though sulfur atoms on the basal plane are known to be stable and inert, we find that they can be electrochemically reduced under accessible applied potentials. This can be done on various 2H-MoS2 nanostructures. By changing the applied desulfurization potential, the extent of desulfurization and the resulting activity can be varied. The resulting active sites are stable under extended desulfurization durations and show consistent HER activity.
View details for DOI 10.1038/ncomms15113
View details for Web of Science ID 000399985300001
-
Theoretical study on oxidative coupling of methane using MgO
AMER CHEMICAL SOC. 2017
View details for Web of Science ID 000430569100049
-
Scaling Relations for Adsorption Energies on Doped Molybdenum Phosphide Surfaces
ACS CATALYSIS
2017; 7 (4): 2528-2534
View details for DOI 10.1021/acscatal.6b03403
View details for Web of Science ID 000398986700035
-
Modeling the Migration of Platinum Nanoparticles on Surfaces Using a Kinetic Monte Carlo Approach
JOURNAL OF PHYSICAL CHEMISTRY C
2017; 121 (8): 4261–69
View details for DOI 10.1021/acs.jpcc.6b11549
View details for Web of Science ID 000395616200018
-
Understanding trends in C-H bond activation in heterogeneous catalysis
NATURE MATERIALS
2017; 16 (2): 225-229
Abstract
While the search for catalysts capable of directly converting methane to higher value commodity chemicals and liquid fuels has been active for over a century, a viable industrial process for selective methane activation has yet to be developed. Electronic structure calculations are playing an increasingly relevant role in this search, but large-scale materials screening efforts are hindered by computationally expensive transition state barrier calculations. The purpose of the present letter is twofold. First, we show that, for the wide range of catalysts that proceed via a radical intermediate, a unifying framework for predicting C-H activation barriers using a single universal descriptor can be established. Second, we combine this scaling approach with a thermodynamic analysis of active site formation to provide a map of methane activation rates. Our model successfully rationalizes the available empirical data and lays the foundation for future catalyst design strategies that transcend different catalyst classes.
View details for DOI 10.1038/NMAT4760
View details for Web of Science ID 000393349800016
-
Mechanistic insights into heterogeneous methane activation.
Physical chemistry chemical physics
2017; 19 (5): 3575-3581
Abstract
While natural gas is an abundant chemical fuel, its low volumetric energy density has prompted a search for catalysts able to transform methane into more useful chemicals. This search has often been aided through the use of transition state (TS) scaling relationships, which estimate methane activation TS energies as a linear function of a more easily calculated descriptor, such as final state energy, thus avoiding tedious TS energy calculations. It has been shown that methane can be activated via a radical or surface-stabilized pathway, both of which possess a unique TS scaling relationship. Herein, we present a simple model to aid in the prediction of methane activation barriers on heterogeneous catalysts. Analogous to the universal radical TS scaling relationship introduced in a previous publication, we show that a universal TS scaling relationship that transcends catalysts classes also seems to exist for surface-stabilized methane activation if the relevant final state energy is used. We demonstrate that this scaling relationship holds for several reducible and irreducible oxides, promoted metals, and sulfides. By combining the universal scaling relationships for both radical and surface-stabilized methane activation pathways, we show that catalyst reactivity must be considered in addition to catalyst geometry to obtain an accurate estimation for the TS energy. This model can yield fast and accurate predictions of methane activation barriers on a wide range of catalysts, thus accelerating the discovery of more active catalysts for methane conversion.
View details for DOI 10.1039/c6cp08003k
View details for PubMedID 28094377
-
Bond Order Conservation Strategies in Catalysis Applied to the NH3 Decomposition Reaction
ACS CATALYSIS
2017; 7 (1): 864-871
View details for DOI 10.1021/acscatal.6b03129
View details for Web of Science ID 000391783200092
-
Methanol Partial Oxidation on Ag(111) from First Principles
CHEMCATCHEM
2016; 8 (23): 3621-3625
View details for DOI 10.1002/cctc.201601053
View details for Web of Science ID 000397014800010
-
Direct and continuous strain control of catalysts with tunable battery electrode materials
SCIENCE
2016; 354 (6315): 1031-1036
Abstract
We report a method for using battery electrode materials to directly and continuously control the lattice strain of platinum (Pt) catalyst and thus tune its catalytic activity for the oxygen reduction reaction (ORR). Whereas the common approach of using metal overlayers introduces ligand effects in addition to strain, by electrochemically switching between the charging and discharging status of battery electrodes the change in volume can be precisely controlled to induce either compressive or tensile strain on supported catalysts. Lattice compression and tension induced by the lithium cobalt oxide substrate of ~5% were directly observed in individual Pt nanoparticles with aberration-corrected transmission electron microscopy. We observed 90% enhancement or 40% suppression in Pt ORR activity under compression or tension, respectively, which is consistent with theoretical predictions.
View details for DOI 10.1126/science.aaf7680
View details for PubMedID 27885028
-
Understanding trends in C-H bond activation in heterogeneous catalysis.
Nature materials
2016
Abstract
While the search for catalysts capable of directly converting methane to higher value commodity chemicals and liquid fuels has been active for over a century, a viable industrial process for selective methane activation has yet to be developed. Electronic structure calculations are playing an increasingly relevant role in this search, but large-scale materials screening efforts are hindered by computationally expensive transition state barrier calculations. The purpose of the present letter is twofold. First, we show that, for the wide range of catalysts that proceed via a radical intermediate, a unifying framework for predicting C-H activation barriers using a single universal descriptor can be established. Second, we combine this scaling approach with a thermodynamic analysis of active site formation to provide a map of methane activation rates. Our model successfully rationalizes the available empirical data and lays the foundation for future catalyst design strategies that transcend different catalyst classes.
View details for DOI 10.1038/nmat4760
View details for PubMedID 27723737
-
Two-Dimensional Materials as Catalysts for Energy Conversion
CATALYSIS LETTERS
2016; 146 (10): 1917-1921
View details for DOI 10.1007/s10562-016-1837-z
View details for Web of Science ID 000385196700011
-
Sintering of Pt Nanoparticles via Volatile PtO2: Simulation and Comparison with Experiments
ACS CATALYSIS
2016; 6 (10): 7098–7108
View details for DOI 10.1021/acscatal.6b01646
View details for Web of Science ID 000385057900091
-
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
-
Dynamical Observation and Detailed Description of Catalysts under Strong Metal-Support Interaction
NANO LETTERS
2016; 16 (7): 4528-4534
Abstract
Understanding the structures of catalysts under realistic conditions with atomic precision is crucial to design better materials for challenging transformations. Under reducing conditions, certain reducible supports migrate onto supported metallic particles and create strong metal-support states that drastically change the reactivity of the systems. The details of this process are still unclear and preclude its thorough exploitation. Here, we report an atomic description of a palladium/titania (Pd/TiO2) system by combining state-of-the-art in situ transmission electron microscopy and density functional theory (DFT) calculations with structurally defined materials, in which we visualize the formation of the overlayers at the atomic scale under atmospheric pressure and high temperature. We show that an amorphous reduced titania layer is formed at low temperatures, and that crystallization of the layer into either mono- or bilayer structures is dictated by the reaction environment and predicted by theory. Furthermore, it occurs in combination with a dramatic reshaping of the metallic surface facets.
View details for DOI 10.1021/acs.nanolett.6b01769
View details for Web of Science ID 000379794200081
View details for PubMedID 27280326
-
Modeling the Interface of Platinum and alpha-Quartz(001): Implications for Sintering
JOURNAL OF PHYSICAL CHEMISTRY C
2016; 120 (19): 10340-10350
View details for DOI 10.1021/acs.jpcc.6b01403
View details for Web of Science ID 000376417500026
-
Trends in the Thermodynamic Stability of Ultrathin Supported Oxide Films
JOURNAL OF PHYSICAL CHEMISTRY C
2016; 120 (19): 10351–60
View details for DOI 10.1021/acs.jpcc.6b01404
View details for Web of Science ID 000376417500027
-
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
-
Activating and optimizing MoS2 basal planes for hydrogen evolution through the formation of strained sulphur vacancies
NATURE MATERIALS
2016; 15 (1): 48-?
Abstract
As a promising non-precious catalyst for the hydrogen evolution reaction (HER; refs ,,,,), molybdenum disulphide (MoS2) is known to contain active edge sites and an inert basal plane. Activating the MoS2 basal plane could further enhance its HER activity but is not often a strategy for doing so. Herein, we report the first activation and optimization of the basal plane of monolayer 2H-MoS2 for HER by introducing sulphur (S) vacancies and strain. Our theoretical and experimental results show that the S-vacancies are new catalytic sites in the basal plane, where gap states around the Fermi level allow hydrogen to bind directly to exposed Mo atoms. The hydrogen adsorption free energy (ΔGH) can be further manipulated by straining the surface with S-vacancies, which fine-tunes the catalytic activity. Proper combinations of S-vacancy and strain yield the optimal ΔGH = 0 eV, which allows us to achieve the highest intrinsic HER activity among molybdenum-sulphide-based catalysts.
View details for DOI 10.1038/NMAT4465
View details for Web of Science ID 000366690600019
View details for PubMedID 26552057
-
Theoretical insights into the hydrogen evolution activity of layered transition metal dichalcogenides
SURFACE SCIENCE
2015; 640: 133-140
View details for DOI 10.1016/j.susc.2015.01.019
View details for Web of Science ID 000359167800019
-
Surface Tension Effects on the Reactivity of Metal Nanoparticles
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
2015; 6 (19): 3797-3801
Abstract
We present calculated adsorption energies of oxygen on gold and platinum clusters with up to 923 atoms (3 nm diameter) using density functional theory. We find that surface tension of the clusters induces a compression, which weakens the bonding of adsorbates compared with the bonding on extended surfaces. The effect is largest for close-packed surfaces and almost nonexistent on the more reactive steps and edges. The effect is largest at low coverage and decreases, even changing sign, at higher coverages where the strain changes from compressive to tensile. Quantum size effects also influence adsorption energies but only below a critical size of 1.5 nm for platinum and 2.5 nm for gold. We develop a model to describe the strain-induced size effects on adsorption energies, which is able to describe the influence of surface structure, adsorbate, metal, and coverage.
View details for DOI 10.1021/acs.jpclett.5b01746
View details for Web of Science ID 000362391000004
-
Predicting Promoter-Induced Bond Activation on Solid Catalysts Using Elementary Bond Orders
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
2015; 6 (18): 3670-3674
Abstract
In this Letter, we examine bond activation induced by nonmetal surface promoters in the context of dehydrogenation reactions. We use C-H bond activation in methane dehydrogenation on transition metals as an example to understand the origin of the promoting or poisoning effect of nonmetals. The electronic structure of the surface and the bond order of the promoter are found to establish all trends in bond activation. On the basis of these results, we develop a predictive model that successfully describes the energetics of C-H, O-H, and N-H bond activation across a range of reactions. For a given reaction step, a single data point determines whether a nonmetal will promote bond activation or poison the surface and by how much. We show how our model leads to general insights that can be directly used to predict bond activation energetics on transition metal sulfides and oxides, which can be perceived as promoted surfaces. These results can then be directly used in studies on full catalytic pathways.
View details for DOI 10.1021/acs.jpclett.5b01792
View details for Web of Science ID 000361858800025
-
From the Sabatier principle to a predictive theory of transition-metal heterogeneous catalysis
JOURNAL OF CATALYSIS
2015; 328: 36-42
View details for DOI 10.1016/j.jcat.2014.12.033
View details for Web of Science ID 000356748300007
-
Hydrogenation of CO2 to methanol and CO on Cu/ZnO/Al2O3: Is there a common intermediate or not?
JOURNAL OF CATALYSIS
2015; 328: 43–48
View details for DOI 10.1016/j.jcat.2014.12.016
View details for Web of Science ID 000356748300008
-
Toward Controlled Growth of Helicity-Specific Carbon Nanotubes
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
2015; 6 (12): 2232-2237
Abstract
The underlying mechanisms for the nucleation of carbon nanotubes as well as their helicity, remain elusive. Here, using van der Waals dispersion force calculations implemented within density functional theory, we study the cap formation, believed to be responsible for the chirality of surface-catalyzed carbon nanotubes. We find the energetics associated with growth along different facets to be independent of the surface orientation and that the growth across an edge along the axis of the metal particle leads to a perfect honeycomb lattice in a curved geometry. The formation of defects in the graphene matrix, which bend the carbon plane, requires that two or more graphene embryos with significantly different growth axis merge. Such scenario is only possible at the front- or back-end of the metal particle where growth symmetry is broken. The graphene embryos reconstruct their hexagonal structure into pentagons, heptagons, and octagons counterpart to accommodate the tube curvature.
View details for DOI 10.1021/acs.jpclett.5b00880
View details for Web of Science ID 000356758100013
-
Examining the Linearity of Transition State Scaling Relations
JOURNAL OF PHYSICAL CHEMISTRY C
2015; 119 (19): 10448-10453
View details for DOI 10.1021/acs.jpcc.5b02055
View details for Web of Science ID 000354912200033
-
The Mechanism of CO and CO2 Hydrogenation to Methanol over Cu-Based Catalysts
CHEMCATCHEM
2015; 7 (7): 1105-1111
View details for DOI 10.1002/cctc.201500123
View details for Web of Science ID 000352488300010
-
Catalyst design principles: An application to the steam reforming of methane
AMER CHEMICAL SOC. 2015
View details for Web of Science ID 000411183301511
-
Transition-metal doped edge sites in vertically aligned MoS2 catalysts for enhanced hydrogen evolution
NANO RESEARCH
2015; 8 (2): 566-575
View details for DOI 10.1007/s12274-014-0677-7
View details for Web of Science ID 000349956600018
-
On the role of the surface oxygen species during A-H (A = C, N, O) bond activation: a density functional theory study.
Chemical communications
2015; 51 (13): 2621-2624
Abstract
During A-H (A = C, N, O) bond cleavage on O* or OH* pre-covered (111) surfaces, the oxygen species play the role of modifying the reaction energy by changing the species involved in the initial and final states of the reaction.
View details for DOI 10.1039/c4cc08658a
View details for PubMedID 25571859
-
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
-
Rational design of MoS2 catalysts: tuning the structure and activity via transition metal doping
CATALYSIS SCIENCE & TECHNOLOGY
2015; 5 (1): 246-253
View details for DOI 10.1039/c4cy01162g
View details for Web of Science ID 000348358200027
-
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
-
Understanding the Reactivity of Layered Transition-Metal Sulfides: A Single Electronic Descriptor for Structure and Adsorption
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
2014; 5 (21): 3884-3889
Abstract
Density functional theory is used to investigate the adsorption and structural properties of layered transition-metal sulfide (TMS) catalysts. We considered both the (101̅0) M-edge and (1̅010) S-edge terminations for a wide range of pure and doped TMSs, determined their sulfur coverage under realistic operating conditions (i.e, steady-state structures), and calculated an extensive set of chemisorption energies for several important reactions. On the basis of these results, we show that the d-band center, εd, of the edge-most metal site at 0 ML sulfur coverage is a general electronic descriptor for both structure and adsorption energies, which are known to describe catalytic activity. A negative linear correlation between adsorbate-S binding and S-metal binding allows εd to describe the adsorption of species on both metal and sulfur sites. Our results provide a significant simplification in the understanding of structure-activity relationships in TMSs and provides guidelines for the rational design and large-scale screening of these catalysts for various processes.
View details for DOI 10.1021/jz5020532
View details for Web of Science ID 000344579500041
-
Energetics of the Water-Gas-Shift Reaction on the Active Sites of the Industrially Used Cu/ZnO/Al2O3 Catalyst
CATALYSIS LETTERS
2014; 144 (11): 1973–77
View details for DOI 10.1007/s10562-014-1363-9
View details for Web of Science ID 000343136100024
-
Insights into carbon nanotube nucleation: Cap formation governed by catalyst interfacial step flow
SCIENTIFIC REPORTS
2014; 4
Abstract
In order to accommodate an increasing demand for carbon nanotubes (CNTs) with desirable characteristics one has to understand the origin of helicity of their structures. Here, through in situ microscopy we demonstrate that the nucleation of a carbon nanotube is initiated by the formation of the carbon cap. Nucleation begins with the formation of a graphene embryo that is bound between opposite step-edges on the nickel catalyst surface. The embryo grows larger as the step-edges migrate along the surface, leading to the formation of a curved carbon cap when the steps flow across the edges of adjacent facets. Further motion of the steps away from the catalyst tip with attached rims of the carbon cap generates the wall of the nanotube. Density Functional Theory calculations bring further insight into the process, showing that step flow occurs by surface self diffusion of the nickel atoms via a step-edge attachment-detachment mechanism. Since the cap forms first in the sequence of stages involved in growth, we suggest that it originates the helicity of the nanotube. Therefore, the angular distribution of catalyst facets could be exploited as a new parameter for controlling the curvature of the cap and, presumably, the helicity of the nanotube.
View details for DOI 10.1038/srep06510
View details for Web of Science ID 000343083200001
View details for PubMedID 25308821
View details for PubMedCentralID PMC4194440
-
Implications of uncertainty on computationally predicted rates and trends in catalytic ammonia synthesis
AMER CHEMICAL SOC. 2014
View details for Web of Science ID 000349165103848
-
Inherent Enhancement of Electronic Emission from Hexaboride Heterostructure
PHYSICAL REVIEW APPLIED
2014; 2 (2)
View details for DOI 10.1103/PhysRevApplied.2.024004
View details for Web of Science ID 000344331500001
-
Catalysis. Assessing the reliability of calculated catalytic ammonia synthesis rates.
Science
2014; 345 (6193): 197-200
Abstract
We introduce a general method for estimating the uncertainty in calculated materials properties based on density functional theory calculations. We illustrate the approach for a calculation of the catalytic rate of ammonia synthesis over a range of transition-metal catalysts. The correlation between errors in density functional theory calculations is shown to play an important role in reducing the predicted error on calculated rates. Uncertainties depend strongly on reaction conditions and catalyst material, and the relative rates between different catalysts are considerably better described than the absolute rates. We introduce an approach for incorporating uncertainty when searching for improved catalysts by evaluating the probability that a given catalyst is better than a known standard.
View details for DOI 10.1126/science.1253486
View details for PubMedID 25013071
-
Active edge sites in MoSe2 and WSe2 catalysts for the hydrogen evolution reaction: a density functional study.
Physical chemistry chemical physics
2014; 16 (26): 13156-13164
Abstract
MoSe2 and WSe2 nanofilms and nanosheets have recently been shown to be active for electrochemical H2 evolution (HER). In this work, we used periodic density functional theory to investigate the origin of the catalytic activity on these materials. We determined the relevant structures of the Mo/W-edges and the Se-edges under HER conditions and their differential hydrogen adsorption free energies. The Mo-edge on MoSe2 and the Se-edge on both MoSe2 and WSe2 are found to be the predominantly active facets for these catalysts, with activity predicted to be comparable to or better than MoS2. On the other hand, the (0001) basal planes are found to be inert. We further explain the enhanced activity at the edges in terms of localized edge states, which provide insight into the trends in HER activity seen between the two catalysts. Our results thus suggest that an optimal catalyst design should maximize the exposure of edge sites. Comparisons are also made between the transition metal selenide catalysts and their sulfide counterparts in order to understand the consequences of having either Mo/W or Se/S atoms. It is found that linear scaling relations describe the S/Se binding onto the edge and the H binding onto the S/Se.
View details for DOI 10.1039/c4cp01237b
View details for PubMedID 24866567
-
DFT Study of Atomically-Modified Alkali-Earth Metal Oxide Films on Tungsten
JOURNAL OF PHYSICAL CHEMISTRY C
2014; 118 (21): 11303-11309
View details for DOI 10.1021/jp4120578
View details for Web of Science ID 000336771700017
-
Exploring the limits: A low-pressure, low-temperature Haber-Bosch process
CHEMICAL PHYSICS LETTERS
2014; 598: 108-112
View details for DOI 10.1016/j.cplett.2014.03.003
View details for Web of Science ID 000334294900021
-
Theoretical Analysis of Transition-Metal Catalysts for Formic Acid Decomposition
ACS CATALYSIS
2014; 4 (4): 1226-1233
View details for DOI 10.1021/cs400664z
View details for Web of Science ID 000338807100024
-
Discovery of a Ni-Ga catalyst for carbon dioxide reduction to methanol
NATURE CHEMISTRY
2014; 6 (4): 320-324
Abstract
The use of methanol as a fuel and chemical feedstock could become very important in the development of a more sustainable society if methanol could be efficiently obtained from the direct reduction of CO2 using solar-generated hydrogen. If hydrogen production is to be decentralized, small-scale CO2 reduction devices are required that operate at low pressures. Here, we report the discovery of a Ni-Ga catalyst that reduces CO2 to methanol at ambient pressure. The catalyst was identified through a descriptor-based analysis of the process and the use of computational methods to identify Ni-Ga intermetallic compounds as stable candidates with good activity. We synthesized and tested a series of catalysts and found that Ni5Ga3 is particularly active and selective. Comparison with conventional Cu/ZnO/Al2O3 catalysts revealed the same or better methanol synthesis activity, as well as considerably lower production of CO. We suggest that this is a first step towards the development of small-scale low-pressure devices for CO2 reduction to methanol.
View details for DOI 10.1038/NCHEM.1873
View details for Web of Science ID 000333396200022
View details for PubMedID 24651199
-
Finite-size effects on gold and platinum clusters
AMER CHEMICAL SOC. 2014
View details for Web of Science ID 000348455204569
-
Effects of d-band shape on the surface reactivity of transition-metal alloys
PHYSICAL REVIEW B
2014; 89 (11)
View details for DOI 10.1103/PhysRevB.89.115114
View details for Web of Science ID 000332705300001
-
Tuning the MoS2 Edge-Site Activity for Hydrogen Evolution via Support Interactions.
Nano letters
2014; 14 (3): 1381-1387
Abstract
The hydrogen evolution reaction (HER) on supported MoS2 catalysts is investigated using periodic density functional theory, employing the new BEEF-vdW functional that explicitly takes long-range van der Waals (vdW) forces into account. We find that the support interactions involving vdW forces leads to significant changes in the hydrogen binding energy, resulting in several orders of magnitude difference in HER activity. It is generally seen for the Mo-edge that strong adhesion of the catalyst onto the support leads to weakening in the hydrogen binding. This presents a way to optimally tune the hydrogen binding on MoS2 and explains the lower than expected exchange current densities of supported MoS2 in electrochemical H2 evolution studies.
View details for DOI 10.1021/nl404444k
View details for PubMedID 24499163
-
Activity and Selectivity Trends in Synthesis Gas Conversion to Higher Alcohols
TOPICS IN CATALYSIS
2014; 57 (1-4): 135-142
View details for DOI 10.1007/s11244-013-0169-0
View details for Web of Science ID 000330829600014
-
In silico search for novel methane steam reforming catalysts
NEW JOURNAL OF PHYSICS
2013; 15
View details for DOI 10.1088/1367-2630/15/12/125021
View details for Web of Science ID 000329439500001
-
On the effect of coverage-dependent adsorbate-adsorbate interactions for CO methanation on transition metal surfaces
JOURNAL OF CATALYSIS
2013; 307: 275-282
View details for DOI 10.1016/j.jcat.2013.08.002
View details for Web of Science ID 000327903900030
-
Density functional theory studies of transition metal nanoparticles in catalysis
AMER CHEMICAL SOC. 2013
View details for Web of Science ID 000329618403017
-
Interlayer Carbon Bond Formation Induced by Hydrogen Adsorption in Few-Layer Supported Graphene
PHYSICAL REVIEW LETTERS
2013; 111 (8)
Abstract
We report on the hydrogen adsorption induced phase transition of a few layer graphene (1 to 4 layers) to a diamondlike structure on Pt(111) based on core level x-ray spectroscopy, temperature programed desorption, infrared spectroscopy, and density functional theory total energy calculations. The surface adsorption of hydrogen induces a hybridization change of carbon from the sp^{2} to the sp^{3} bond symmetry, which propagates through the graphene layers, resulting in interlayer carbon bond formation. The structure is stabilized through the termination of interfacial sp^{3} carbon atoms by the substrate. The structural transformation occurs as a consequence of high adsorption energy.
View details for DOI 10.1103/PhysRevLett.111.085503
View details for Web of Science ID 000323388200016
View details for PubMedID 24010453
-
Stability of Pt-Modified Cu(111) in the Presence of Oxygen and Its Implication on the Overall Electronic Structure
JOURNAL OF PHYSICAL CHEMISTRY C
2013; 117 (32): 16371-16380
View details for DOI 10.1021/jp400486r
View details for Web of Science ID 000323301100012
-
Analysis of sulfur-induced selectivity changes for anhydrous methanol dehydrogenation on Ni(100) surfaces
SURFACE SCIENCE
2013; 613: 58-62
View details for DOI 10.1016/j.suse.2013.03.004
View details for Web of Science ID 000319180600010
-
Thermionic current densities from first principles.
journal of chemical physics
2013; 138 (20): 204701-?
Abstract
We present a density functional theory-based method for calculating thermionic emission currents from a cathode into vacuum using a non-equilibrium Green's function approach. It does not require semi-classical approximations or crude simplifications of the electronic structure used in previous methods and thus provides quantitative predictions of thermionic emission for adsorbate-coated surfaces. The obtained results match well with experimental measurements of temperature-dependent current densities. Our approach can thus enable computational design of composite electrode materials.
View details for DOI 10.1063/1.4805002
View details for PubMedID 23742494
-
Comment on "Using Photoelectron Spectroscopy and Quantum Mechanics to Determine d-Band Energies of Metals for Catalytic Applications"
JOURNAL OF PHYSICAL CHEMISTRY C
2013; 117 (13): 6914-6915
View details for DOI 10.1021/jp312595p
View details for Web of Science ID 000317317600050
-
Bronsted-Evans-Polanyi Relationship for Transition Metal Carbide and Transition Metal Oxide Surfaces
JOURNAL OF PHYSICAL CHEMISTRY C
2013; 117 (8): 4168–71
View details for DOI 10.1021/jp312671z
View details for Web of Science ID 000318211800055
-
Electronic Origin of the Surface Reactivity of Transition-Metal-Doped TiO2(110)
JOURNAL OF PHYSICAL CHEMISTRY C
2013; 117 (1): 460-465
View details for DOI 10.1021/jp310667r
View details for Web of Science ID 000313220700059
-
Investigation of Catalytic Finite-Size-Effects of Platinum Metal Clusters
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
2013; 4 (1): 222-226
Abstract
In this paper, we use density functional theory (DFT) calculations on highly parallel computing resources to study size-dependent changes in the chemical and electronic properties of platinum (Pt) for a number of fixed freestanding clusters ranging from 13 to 1415 atoms, or 0.7-3.5 nm in diameter. We find that the surface catalytic properties of the clusters converge to the single crystal limit for clusters with as few as 147 atoms (1.6 nm). Recently published results for gold (Au) clusters showed analogous convergence with size. However, this convergence happened at larger sizes, because the Au d-states do not contribute to the density of states around the Fermi-level, and the observed level fluctuations were not significantly damped until the cluster reached ca. 560 atoms (2.7 nm) in size.
View details for DOI 10.1021/jz3018286
View details for Web of Science ID 000313142000032
-
CO and CO2 Hydrogenation to Methanol Calculated Using the BEEF-vdW Functional
CATALYSIS LETTERS
2013; 143 (1): 71-73
View details for DOI 10.1007/s10562-012-0947-5
View details for Web of Science ID 000313653600009
-
Energetics of Oxygen Adatoms, Hydroxyl Species and Water Dissociation on Pt(111)
JOURNAL OF PHYSICAL CHEMISTRY C
2012; 116 (49): 25772-25776
View details for DOI 10.1021/jp3066794
View details for Web of Science ID 000312176100015
-
Elementary steps of syngas reactions on Mo2C(0 0 1): Adsorption thermochemistry and bond dissociation (vol 290, pg 108, 2012)
JOURNAL OF CATALYSIS
2012; 296: 175-175
View details for DOI 10.1016/j.jcat.2012.09.009
View details for Web of Science ID 000312427100017
-
An orbital-overlap model for minimal work functions of cesiated metal surfaces
JOURNAL OF PHYSICS-CONDENSED MATTER
2012; 24 (44)
Abstract
We introduce a model for the effect of cesium adsorbates on the work function of transition metal surfaces. The model builds on the classical point-dipole equation by adding exponential terms that characterize the degree of orbital overlap between the 6s states of neighboring cesium adsorbates and its effect on the strength and orientation of electric dipoles along the adsorbate-substrate interface. The new model improves upon earlier models in terms of agreement with the work function-coverage curves obtained via first-principles calculations based on density functional theory. All the cesiated metal surfaces have optimal coverages between 0.6 and 0.8 monolayers, in accordance with experimental data. Of all the cesiated metal surfaces that we have considered, tungsten has the lowest minimum work function, also in accordance with experiments.
View details for DOI 10.1088/0953-8984/24/44/445007
View details for Web of Science ID 000310571100009
View details for PubMedID 23018485
-
Volcano Relations for Oxidation of Hydrogen Halides over Rutile Oxide Surfaces
CHEMCATCHEM
2012; 4 (11): 1856–61
View details for DOI 10.1002/cctc.201200140
View details for Web of Science ID 000310470200027
-
CO hydrogenation to methanol on Cu-Ni catalysts: Theory and experiment
JOURNAL OF CATALYSIS
2012; 293: 51-60
View details for DOI 10.1016/j.jcat.2012.06.004
View details for Web of Science ID 000308836800005
-
Reversible graphene-metal contact through hydrogenation
PHYSICAL REVIEW B
2012; 86 (7)
View details for DOI 10.1103/PhysRevB.86.075417
View details for Web of Science ID 000307272700004
-
Application of a new informatics tool in heterogeneous catalysis: Analysis of methanol dehydrogenation on transition metal catalysts for the production of anhydrous formaldehyde
JOURNAL OF CATALYSIS
2012; 291: 133-137
View details for DOI 10.1016/j.jcat.2012.04.017
View details for Web of Science ID 000306779600017
-
Elementary steps of syngas reactions on Mo2C(001): Adsorption thermochemistry and bond dissociation
JOURNAL OF CATALYSIS
2012; 290: 108-117
View details for DOI 10.1016/j.jcat.2012.03.007
View details for Web of Science ID 000305098400011
-
The Active Site of Methanol Synthesis over Cu/ZnO/Al2O3 Industrial Catalysts
SCIENCE
2012; 336 (6083): 893-897
Abstract
One of the main stumbling blocks in developing rational design strategies for heterogeneous catalysis is that the complexity of the catalysts impairs efforts to characterize their active sites. We show how to identify the crucial atomic structure motif for the industrial Cu/ZnO/Al(2)O(3) methanol synthesis catalyst by using a combination of experimental evidence from bulk, surface-sensitive, and imaging methods collected on real high-performance catalytic systems in combination with density functional theory calculations. The active site consists of Cu steps decorated with Zn atoms, all stabilized by a series of well-defined bulk defects and surface species that need to be present jointly for the system to work.
View details for DOI 10.1126/science.1219831
View details for Web of Science ID 000304145600059
View details for PubMedID 22517324
-
CatApp: A web application for surface chemistry and heterogeneous catalysis
11th International Biorelated Polymer Symposium / 243rd National Spring Meeting of the American-Chemical-Society (ACS)
AMER CHEMICAL SOC. 2012
View details for Web of Science ID 000324475101205
-
Scaling relations applied to synthetic fuel production
AMER CHEMICAL SOC. 2012
View details for Web of Science ID 000324475105899
-
Catalyst design on the computer
AMER CHEMICAL SOC. 2012
View details for Web of Science ID 000324503203276
-
CatApp: A Web Application for Surface Chemistry and Heterogeneous Catalysis
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
2012; 51 (1): 272-274
View details for DOI 10.1002/anie.201107947
View details for Web of Science ID 000298598500049
View details for PubMedID 22162297
-
A theoretical evaluation of possible transition metal electro-catalysts for N-2 reduction
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
2012; 14 (3): 1235-1245
Abstract
Theoretical studies of the possibility of forming ammonia electrochemically at ambient temperature and pressure are presented. Density functional theory calculations were used in combination with the computational standard hydrogen electrode to calculate the free energy profile for the reduction of N(2) admolecules and N adatoms on several close-packed and stepped transition metal surfaces in contact with an acidic electrolyte. Trends in the catalytic activity were calculated for a range of transition metal surfaces and applied potentials under the assumption that the activation energy barrier scales with the free energy difference in each elementary step. The most active surfaces, on top of the volcano diagrams, are Mo, Fe, Rh, and Ru, but hydrogen gas formation will be a competing reaction reducing the faradaic efficiency for ammonia production. Since the early transition metal surfaces such as Sc, Y, Ti, and Zr bind N-adatoms more strongly than H-adatoms, a significant production of ammonia compared with hydrogen gas can be expected on those metal electrodes when a bias of -1 V to -1.5 V vs. SHE is applied. Defect-free surfaces of the early transition metals are catalytically more active than their stepped counterparts.
View details for DOI 10.1039/c1cp22271f
View details for Web of Science ID 000299271800015
-
Scaling relationships for adsorption energies of C-2 hydrocarbons on transition metal surfaces
CHEMICAL ENGINEERING SCIENCE
2011; 66 (24): 6318-6323
View details for DOI 10.1016/j.ces.2011.02.050
View details for Web of Science ID 000296568500003
-
Scaling relations applied to synthetic fuel production
242nd National Meeting of the American-Chemical-Society (ACS)
AMER CHEMICAL SOC. 2011
View details for Web of Science ID 000299378303423
-
On the activity and selectivity of syngas conversion processes
242nd National Meeting of the American-Chemical-Society (ACS)
AMER CHEMICAL SOC. 2011
View details for Web of Science ID 000299378303131
-
Structure effects on the energetics of the electrochemical reduction of CO2 by copper surfaces
SURFACE SCIENCE
2011; 605 (15-16): 1354-1359
View details for DOI 10.1016/j.susc.2011.04.028
View details for Web of Science ID 000293671000006
-
Understanding selectivity in syngas reactions
241st National Meeting and Exposition of the American-Chemical-Society (ACS)
AMER CHEMICAL SOC. 2011
View details for Web of Science ID 000291982806703
-
Br(A)over-tilde,nsted-Evans-Polanyi relations for transition-metal oxides from density functional theory
241st National Meeting and Exposition of the American-Chemical-Society (ACS)
AMER CHEMICAL SOC. 2011
View details for Web of Science ID 000291982803874
-
Universal Bronsted-Evans-Polanyi Relations for C-C, C-O, C-N, N-O, N-N, and O-O Dissociation Reactions
CATALYSIS LETTERS
2011; 141 (3): 370-373
View details for DOI 10.1007/s10562-010-0477-y
View details for Web of Science ID 000287506800002
-
First-principles investigations of Ni3Al(111) and NiAl(110) surfaces at metal dusting conditions
SURFACE SCIENCE
2011; 605 (5-6): 582-592
View details for DOI 10.1016/j.susc.2010.12.023
View details for Web of Science ID 000287833500019
-
Density functional theory in surface chemistry and catalysis
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2011; 108 (3): 937-943
Abstract
Recent advances in the understanding of reactivity trends for chemistry at transition-metal surfaces have enabled in silico design of heterogeneous catalysts in a few cases. The current status of the field is discussed with an emphasis on the role of coupling theory and experiment and future challenges.
View details for DOI 10.1073/pnas.1006652108
View details for Web of Science ID 000286310300013
View details for PubMedID 21220337
View details for PubMedCentralID PMC3024687
-
Descriptor-Based Analysis Applied to HCN Synthesis from NH3 and CH4
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
2011; 50 (20): 4601-4605
View details for DOI 10.1002/anie.201100353
View details for Web of Science ID 000290663600007
View details for PubMedID 21500324
-
How copper catalyzes the electroreduction of carbon dioxide into hydrocarbon fuels
ENERGY & ENVIRONMENTAL SCIENCE
2010; 3 (9): 1311-1315
View details for DOI 10.1039/c0ee00071j
View details for Web of Science ID 000282334000016
-
On the Role of Metal Step-Edges in Graphene Growth
JOURNAL OF PHYSICAL CHEMISTRY C
2010; 114 (25): 11221-11227
View details for DOI 10.1021/jp1033596
View details for Web of Science ID 000278982300031
-
Self Blocking of CO Dissociation on a Stepped Ruthenium Surface
TOPICS IN CATALYSIS
2010; 53 (5-6): 357-364
View details for DOI 10.1007/s11244-010-9445-4
View details for Web of Science ID 000276979100007
-
Electrochemical chlorine evolution at rutile oxide (110) surfaces
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
2010; 12 (1): 283–90
Abstract
Based on density functional theory (DFT) calculations we study the electrochemical chlorine evolution reaction on rutile (110) oxide surfaces. First we construct the Pourbaix surface diagram for IrO(2) and RuO(2), and from this we find the chlorine evolution reaction intermediates and identify the lowest overpotential at which all elementary reaction steps in the chlorine evolution reaction are downhill in free energy. This condition is then used as a measure for catalytic activity. Linear scaling relations between the binding energies of the intermediates and the oxygen binding energies at cus-sites are established for MO(2) (M being Ir, Ru, Pt, Ti). The linear relations form the basis for constructing a generalized surface phase diagram where two parameters, the potential and the binding energy of oxygen, are needed to determine the surface composition. We calculate the catalytic activity as function of the oxygen binding energy, giving rise to a Sabatier volcano. By combining the surface phase diagram and the volcano describing the catalytic activity, we find that the reaction mechanism differs depending on catalyst material. The flexibility in reaction path means that the chlorine evolution activity is high for a wide range of oxygen binding energies. We find that the required overpotential for chlorine evolution is lower than the overpotential necessary for oxygen evolution.
View details for DOI 10.1039/b917459a
View details for Web of Science ID 000272589000032
View details for PubMedID 20024470
-
Volcano Relation for the Deacon Process over Transition-Metal Oxides
CHEMCATCHEM
2010; 2 (1): 98–102
View details for DOI 10.1002/cctc.200900194
View details for Web of Science ID 000274283600013
-
CATALYSIS Bond control in surface reactions
NATURE
2009; 461 (7268): 1223–25
View details for DOI 10.1038/4611223a
View details for Web of Science ID 000271190800035
View details for PubMedID 19865160
-
First-principles investigations of the Ni3Sn alloy at steam reforming conditions
SURFACE SCIENCE
2009; 603 (5): 762-770
View details for DOI 10.1016/j.susc.2009.01.018
View details for Web of Science ID 000264507600005
-
Trends for Methane Oxidation at Solid Oxide Fuel Cell Conditions
JOURNAL OF THE ELECTROCHEMICAL SOCIETY
2009; 156 (12): B1447–B1456
View details for DOI 10.1149/1.3230622
View details for Web of Science ID 000271218900024
- Virtual materials design using databases of calculated materials properties. Computational Science and Discovery 2009; 2: 27
-
The nature of the active site in heterogeneous metal catalysis
CHEMICAL SOCIETY REVIEWS
2008; 37 (10): 2163-2171
Abstract
This tutorial review, of relevance for the surface science and heterogeneous catalysis communities, provides a molecular-level discussion of the nature of the active sites in metal catalysis. Fundamental concepts such as "Brønsted-Evans-Polanyi relations" and "volcano curves" are introduced, and are used to establish a strict partitioning between the so-called "electronic" and "geometrical" effects. This partitioning is subsequently employed as the basis for defining the concept "degree of structure sensitivity" which can be used when analyzing the structure sensitivity of catalytic reactions.
View details for DOI 10.1039/b800260f
View details for Web of Science ID 000259505600003
View details for PubMedID 18818819
-
First principles calculations and experimental insight into methane steam reforming over transition metal catalysts
JOURNAL OF CATALYSIS
2008; 259 (1): 147-160
View details for DOI 10.1016/j.jcat.2008.08.003
View details for Web of Science ID 000260267900017
-
Identification of non-precious metal alloy catalysts for selective hydrogenation of acetylene
SCIENCE
2008; 320 (5881): 1320-1322
Abstract
The removal of trace acetylene from ethylene is performed industrially by palladium hydrogenation catalysts (often modified with silver) that avoid the hydrogenation of ethylene to ethane. In an effort to identify catalysts based on less expensive and more available metals, density functional calculations were performed that identified relations in heats of adsorption of hydrocarbon molecules and fragments on metal surfaces. This analysis not only verified the facility of known catalysts but identified nickel-zinc alloys as alternatives. Experimental studies demonstrated that these alloys dispersed on an oxide support were selective for acetylene hydrogenation at low pressures.
View details for DOI 10.1126/science.1156660
View details for Web of Science ID 000256441100039
View details for PubMedID 18535238
-
Structure sensitivity of the methanation reaction: H-2-induced CO dissociation on nickel surfaces
JOURNAL OF CATALYSIS
2008; 255 (1): 6-19
View details for DOI 10.1016/j.jcat.2007.12.016
View details for Web of Science ID 000254966500002
-
Using scaling relations to understand trends in the catalytic activity of transition metals
2nd Workshop on Theory Meets Industry
IOP PUBLISHING LTD. 2008
Abstract
A method is developed to estimate the potential energy diagram for a full catalytic reaction for a range of late transition metals on the basis of a calculation (or an experimental determination) for a single metal. The method, which employs scaling relations between adsorption energies, is illustrated by calculating the potential energy diagram for the methanation reaction and ammonia synthesis for 11 different metals on the basis of results calculated for Ru. It is also shown that considering the free energy diagram for the reactions, under typical industrial conditions, provides additional insight into reactivity trends.
View details for DOI 10.1088/0953-8984/20/6/064239
View details for Web of Science ID 000252927300040
View details for PubMedID 21693900
-
On the Role of Surface Modifications of Palladium Catalysts in the Selective Hydrogenation of Acetylene
International Symposium on Creation and Control of Advanced Selective Catalysis
WILEY-V C H VERLAG GMBH. 2008: 9299–9302
View details for DOI 10.1002/anie.200802844
View details for Web of Science ID 000261445900023
View details for PubMedID 18833559
-
Scaling relationships for adsorption energies on transition metal oxide, sulfide, and nitride surfaces
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
2008; 47 (25): 4683-4686
View details for DOI 10.1002/anie.200705739
View details for Web of Science ID 000256894600012
View details for PubMedID 18484577
-
Scaling properties of adsorption energies for hydrogen-containing molecules on transition-metal surfaces
PHYSICAL REVIEW LETTERS
2007; 99 (1)
Abstract
Density functional theory calculations are presented for CHx, x=0,1,2,3, NHx, x=0,1,2, OHx, x=0,1, and SHx, x=0,1 adsorption on a range of close-packed and stepped transition-metal surfaces. We find that the adsorption energy of any of the molecules considered scales approximately with the adsorption energy of the central, C, N, O, or S atom, the scaling constant depending only on x. A model is proposed to understand this behavior. The scaling model is developed into a general framework for estimating the reaction energies for hydrogenation and dehydrogenation reactions.
View details for DOI 10.1103/PhysRevLett.99.016105
View details for Web of Science ID 000247819900029
View details for PubMedID 17678168
-
CO adsorption energies on metals with correction for high coordination adsorption sites - A density functional study
SURFACE SCIENCE
2007; 601 (7): 1747–53
View details for DOI 10.1016/j.susc.2007.01.052
View details for Web of Science ID 000245870500014
-
Carbide induced reconstruction of monatomic steps on Ni(111) - A density functional study
SURFACE SCIENCE
2007; 601 (3): 649–55
View details for DOI 10.1016/j.susc.2006.10.036
View details for Web of Science ID 000244372900009
-
Mechanisms for catalytic carbon nanofiber growth studied by ab initio density functional theory calculations
PHYSICAL REVIEW B
2006; 73 (11)
View details for DOI 10.1103/PhysRevB.73.115419
View details for Web of Science ID 000236467300139
-
Understanding the effect of steps, strain, poisons, and alloying: Methane activation on Ni surfaces
CATALYSIS LETTERS
2005; 105 (1-2): 9-13
View details for DOI 10.1007/s10562-005-7998-9
View details for Web of Science ID 000232697100002
-
Methane activation on Ni(111): Effects of poisons and step defects
SURFACE SCIENCE
2005; 590 (2-3): 127-137
View details for DOI 10.1016/j.susc.2005.05.057
View details for Web of Science ID 000231657300004
-
DFT study of formaldehyde and methanol synthesis from CO and H-2 on Ni(111)
JOURNAL OF PHYSICAL CHEMISTRY B
2004; 108 (38): 14535-14540
View details for DOI 10.1021/jp0493374
View details for Web of Science ID 000223922500044
-
Atomic-scale imaging of carbon nanofibre growth
NATURE
2004; 427 (6973): 426-429
Abstract
The synthesis of carbon nanotubes with predefined structure and functionality plays a central role in the field of nanotechnology, whereas the inhibition of carbon growth is needed to prevent a breakdown of industrial catalysts for hydrogen and synthesis gas production. The growth of carbon nanotubes and nanofibres has therefore been widely studied. Recent advances in in situ techniques now open up the possibility of studying gas-solid interactions at the atomic level. Here we present time-resolved, high-resolution in situ transmission electron microscope observations of the formation of carbon nanofibres from methane decomposition over supported nickel nanocrystals. Carbon nanofibres are observed to develop through a reaction-induced reshaping of the nickel nanocrystals. Specifically, the nucleation and growth of graphene layers are found to be assisted by a dynamic formation and restructuring of mono-atomic step edges at the nickel surface. Density-functional theory calculations indicate that the observations are consistent with a growth mechanism involving surface diffusion of carbon and nickel atoms. The finding that metallic step edges act as spatiotemporal dynamic growth sites may be important for understanding other types of catalytic reactions and nanomaterial syntheses.
View details for DOI 10.1038/nature02278
View details for Web of Science ID 000188470500038
View details for PubMedID 14749826