Bio-inspired hydrophobicity promotes CO2 reduction on a Cu surface
2019; 18 (11): 1222-+
The aqueous electrocatalytic reduction of CO2 into alcohol and hydrocarbon fuels presents a sustainable route towards energy-rich chemical feedstocks. Cu is the only material able to catalyse the substantial formation of multicarbon products (C2/C3), but competing proton reduction to hydrogen is an ever-present drain on selectivity. Here, a superhydrophobic surface was generated by 1-octadecanethiol treatment of hierarchically structured Cu dendrites, inspired by the structure of gas-trapping cuticles on subaquatic spiders. The hydrophobic electrode attained a 56% Faradaic efficiency for ethylene and 17% for ethanol production at neutral pH, compared to 9% and 4% on a hydrophilic, wettable equivalent. These observations are assigned to trapped gases at the hydrophobic Cu surface, which increase the concentration of CO2 at the electrode-solution interface and consequently increase CO2 reduction selectivity. Hydrophobicity is thus proposed as a governing factor in CO2 reduction selectivity and can help explain trends seen on previously reported electrocatalysts.
View details for DOI 10.1038/s41563-019-0445-x
View details for Web of Science ID 000492685600019
View details for PubMedID 31384032
- Solar-driven reforming of lignocellulose to H-2 with a CdS/CdOx photocatalyst NATURE ENERGY 2017; 2 (4)
Electroreduction of CO2 on Single-Site Copper-Nitrogen-Doped Carbon Material: Selective Formation of Ethanol and Reversible Restructuration of the Metal Sites
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
2019; 58 (42): 15098–103
It is generally believed that CO2 electroreduction to multi-carbon products such as ethanol or ethylene may be catalyzed with significant yield only on metallic copper surfaces, implying large ensembles of copper atoms. Here, we report on an inexpensive Cu-N-C material prepared via a simple pyrolytic route that exclusively feature single copper atoms with a CuN4 coordination environment, atomically dispersed in a nitrogen-doped conductive carbon matrix. This material achieves aqueous CO2 electroreduction to ethanol at a Faradaic yield of 55 % under optimized conditions (electrolyte: 0.1 m CsHCO3 , potential: -1.2 V vs. RHE and gas-phase recycling set up), as well as CO electroreduction to C2 -products (ethanol and ethylene) with a Faradaic yield of 80 %. During electrolysis the isolated sites transiently convert into metallic copper nanoparticles, as shown by operando XAS analysis, which are likely to be the catalytically active species. Remarkably, this process is reversible and the initial material is recovered intact after electrolysis.
View details for DOI 10.1002/anie.201907994
View details for Web of Science ID 000485492500001
View details for PubMedID 31453650
Highlights from Faraday Discussion: Artificial Photosynthesis, Cambridge, UK, March 2019
2019; 55 (58): 8351–58
This Faraday Discussion was held on March 25-27th, 2019 at Murray Edwards College, Cambridge, UK and was attended by 160 delegates from over 20 countries. The attendees represented the cross-disciplinary nature of the field, with biologists, engineers, material scientists, theoreticians and experimental chemists of all experience levels coming together to discuss the state of the art. The meeting captured how rapidly the field of artificial photosynthesis has progressed in a short time and highlighted how far we still have to go. In this conference report, the topics of discussion will be outlined with a brief description of the papers presented and a summary of the conference events.
View details for DOI 10.1039/c9cc90252j
View details for Web of Science ID 000476535400001
View details for PubMedID 31271190
Zn-Cu Alloy Nanofoams as Efficient Catalysts for the Reduction of CO2 to Syngas Mixtures with a Potential-Independent H-2/CO Ratio
2019; 12 (2): 511–17
Alloying strategies are commonly used to design electrocatalysts that take on properties of their constituent elements. Herein, such a strategy is used to develop Zn-Cu alloyed electrodes with unique hierarchical porosity and tunable selectivity for CO2 versus H+ reduction. By varying the Zn/Cu ratio, tailored syngas mixtures are obtained without the production of other gaseous products, which is attributed to preferential CO- and H2 -forming pathways on the alloys. The syngas ratios are also significantly less sensitive to the applied potential in the alloys relative to pure metal equivalents; an essential quality when coupling electrocatalysis with renewable power sources that have fluctuating intensity. As such, industrially relevant syngas ratios are achieved at large currents (-60 mA) for extensive operating times (>9 h), demonstrating the potential of this strategy for fossil-free fuel production.
View details for DOI 10.1002/cssc.201802287
View details for Web of Science ID 000459737500020
View details for PubMedID 30637969
Aerobic Conditions Enhance the Photocatalytic Stability of CdS/CdOx Quantum Dots
CHEMISTRY-A EUROPEAN JOURNAL
2018; 24 (69): 18385–88
Photocatalytic H2 production through water splitting represents an attractive route to generate a renewable fuel. These systems are typically limited to anaerobic conditions due to the inhibiting effects of O2 . Here, we report that sacrificial H2 evolution with CdS quantum dots does not necessarily suffer from O2 inhibition and can even be stabilised under aerobic conditions. The introduction of O2 prevents a key inactivation pathway of CdS (over-accumulation of metallic Cd and particle agglomeration) and thereby affords particles with higher stability. These findings represent a possibility to exploit the O2 reduction reaction to inhibit deactivation, rather than catalysis, offering a strategy to stabilise photocatalysts that suffer from similar degradation reactions.
View details for DOI 10.1002/chem.201802353
View details for Web of Science ID 000452614800017
View details for PubMedID 29750379
View details for PubMedCentralID PMC6348374
- Plastic waste as a feedstock for solar-driven H-2 generation ENERGY & ENVIRONMENTAL SCIENCE 2018; 11 (10): 2853–57
A Poly(cobaloxime)/Carbon Nanotube Electrode: Freestanding Buckypaper with Polymer-Enhanced H-2-Evolution Performance
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
2016; 55 (12): 3952–57
A freestanding H2-evolution electrode consisting of a copolymer-embedded cobaloxime integrated into a multiwall carbon nanotube matrix by π-π interactions is reported. This electrode is straightforward to assemble and displays high activity towards hydrogen evolution in near-neutral pH solution under inert and aerobic conditions, with a cobalt-based turnover number (TON(Co)) of up to 420. An analogous electrode with a monomeric cobaloxime showed less activity with a TON(Co) of only 80. These results suggest that, in addition to the high surface area of the porous network of the buckypaper, the polymeric scaffold provides a stabilizing environment to the catalyst, leading to further enhancement in catalytic performance. We have therefore established that the use of a multifunctional copolymeric architecture is a viable strategy to enhance the performance of molecular electrocatalysts.
View details for DOI 10.1002/anie.201511378
View details for Web of Science ID 000372660400014
View details for PubMedID 26890469
View details for PubMedCentralID PMC4794774
DuBois Photocatalysis: Visible light driven H2 generation with a phosphonated Ni bis(diphosphine) catalyst in water
AMER CHEMICAL SOC. 2015
View details for Web of Science ID 000432475501661
Photocatalytic Formic Acid Conversion on CdS Nanocrystals with Controllable Selectivity for H-2 or CO
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
2015; 54 (33): 9627–31
Formic acid is considered a promising energy carrier and hydrogen storage material for a carbon-neutral economy. We present an inexpensive system for the selective room-temperature photocatalytic conversion of formic acid into either hydrogen or carbon monoxide. Under visible-light irradiation (λ>420 nm, 1 sun), suspensions of ligand-capped cadmium sulfide nanocrystals in formic acid/sodium formate release up to 116±14 mmol H2 g(cat)(-1) h(-1) with >99% selectivity when combined with a cobalt co-catalyst; the quantum yield at λ=460 nm was 21.2±2.7%. In the absence of capping ligands, suspensions of the same photocatalyst in aqueous sodium formate generate up to 102±13 mmol CO g(cat)(-1) h(-1) with >95% selectivity and 19.7±2.7% quantum yield. H2 and CO production was sustained for more than one week with turnover numbers greater than 6×10(5) and 3×10(6), respectively.
View details for DOI 10.1002/anie.201502773
View details for Web of Science ID 000358987300033
View details for PubMedID 26201752
View details for PubMedCentralID PMC4552973
- Oxygen-tolerant proton reduction catalysis: much O-2 about nothing? ENERGY & ENVIRONMENTAL SCIENCE 2015; 8 (8): 2283–95
Reversible lnterconversion of CO2 and Formate by a Molybdenum-Containing Formate Dehydrogenase
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2014; 136 (44): 15473–76
CO2 and formate are rapidly, selectively, and efficiently interconverted by tungsten-containing formate dehydrogenases that surpass current synthetic catalysts. However, their mechanism of catalysis is unknown, and no tractable system is available for study. Here, we describe the catalytic properties of the molybdenum-containing formate dehydrogenase H from the model organism Escherichia coli (EcFDH-H). We use protein film voltammetry to demonstrate that EcFDH-H is a highly active, reversible electrocatalyst. In each voltammogram a single point of zero net current denotes the CO2 reduction potential that varies with pH according to the Nernst equation. By quantifying formate production we show that electrocatalytic CO2 reduction is specific. Our results reveal the capabilities of a Mo-containing catalyst for reversible CO2 reduction and establish EcFDH-H as an attractive model system for mechanistic investigations and a template for the development of synthetic catalysts.
View details for DOI 10.1021/ja508647u
View details for Web of Science ID 000344516600006
View details for PubMedID 25325406
Development and understanding of cobaloxime activity through electrochemical molecular catalyst screening
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
2014; 16 (12): 5739–46
Electrochemical molecular catalyst screening (EMoCS) has been developed. This technique allows fast analysis and identification of homogeneous catalytic species through tandem catalyst assembly and electrochemistry. EMoCS has been used to study molecular proton reduction catalysts made from earth abundant materials to improve their viability for water splitting systems. The efficacy of EMoCS is proven through investigation of cobaloxime proton reduction activity with respect to the axial ligand in aqueous solution. Over 20 axial ligands were analysed, allowing rapid identification of the most active catalysts. Structure-activity relationships showed that more electron donating pyridine ligands result in enhanced catalytic currents due to the formation of a more basic Co-H species. The EMoCS results were validated by isolating and assaying the most electroactive cobaloximes identified during screening. The most active catalyst, [Co(III)Cl(dimethyl glyoximato)2(4-methoxypyridine)], showed high electro- and photoactivity in both anaerobic and aerobic conditions in pH neutral aqueous solution.
View details for DOI 10.1039/c4cp00453a
View details for Web of Science ID 000332396500034
View details for PubMedID 24525821
Proton reduction by molecular catalysts in water under demanding atmospheres
2014; 50 (100): 15995–98
The electrocatalytic proton reduction activity of a Ni bis(diphosphine) (NiP) and a cobaloxime (CoP) catalyst has been studied in water in the presence of the gaseous inhibitors O2 and CO. CoP shows an appreciable tolerance towards O2, but its activity suffers severely in the presence of CO. In contrast, NiP is strongly inhibited by O2, but produces H2 under high CO concentrations.
View details for DOI 10.1039/c4cc06159d
View details for Web of Science ID 000345452400040
View details for PubMedID 25407336