The Reduction of Carbon Dioxide by Enzymes Adsorbed on Electrodes: from Mechanistic Studies to Bioinspired Catalysts

Lead Research Organisation: University of Cambridge
Department Name: Chemistry

Abstract

Carbon dioxide (CO2) is produced by the combustion of carbon-containing molecules, such as fossil fuels, to power industry, for transportation, and in our homes. Burning fossil fuels is not only causing the level of CO2 in the atmosphere to increase (CO2 is a greenhouse gas and a major contributor to global warming) it is also depleting valuable resources that are required for the manufacture of plastics, chemicals, fertilizers - and countless other requirements of modern society. Unfortunately, CO2 is a very stable and unreactive molecule, and the only large scale process known that can remove CO2 from the atmosphere and use it to regenerate a carbon-containing fuel is biological photosynthesis (growing plants and trees). Therefore, an industrial process that could use the energy from sunlight, or a green-electricity source, to take CO2 out of the atmosphere and turn it into a useful fuel or chemical would revolutionise modern society, by supplying both our energy and material demands. Of course, no such process currently exists. The aim of this proposal is to explore a new approach for the development of such a process. Some bacteria use enzymes called formate dehydrogenases (FDHs) to catalyse the oxidation (= burning) of formate to CO2, and extract energy from this reaction in order to survive. Chemically, formate is one of the simplest hydrocarbons - it is already used as a chemical building block (feedstock) in industry, and formate 'fuel cells' are being developed. Turning a formate dehydrogenases 'in reverse' would turn CO2 into formate, a useful product. In fact, a small number of specialised bacteria use special 'tungsten-containing' FDHs to catalyse this reverse reaction - and live off the tiny amount of energy that they extract. In a pilot study we showed that the tungsten FDH from a bacterium called Syntrophobacter fumaroxidans can act as an extremely efficient electrically-driven catalyst for the reduction of CO2 to formate. In this project we aim to find out 'how the tungsten formate dehydrogenase does it'. We will start by looking for and characterising tungsten FDHs from different organisms, to find those that are the best for our experiments. Then we will apply sophisticated biochemical, electrochemical and physical techniques to aim to find out how they work - and why they work so well. Finally, we will compare our biological catalysts with available synthetic catalysts, aiming to find out how to improve the synthetic catalysts, and to develop 'demonstration devices' that show how efficient CO2 reduction catalysts can be powered by solar radiation and used in fuel cells.

Technical Summary

Carbon dioxide (CO2) is a thermodynamically and kinetically stable molecule. It is easily formed by the oxidation of organic molecules, during combustion or respiration, but difficult to chemically activate or reduce. The production of reduced carbon compounds from CO2 is an attractive proposition, because carbon-neutral energy sources could be used to generate fuel resources and sequester atmospheric CO2. However, available methods for CO2 reduction are slow, energetically wasteful, and produce mixtures of products. In a preliminary study we demonstrated that a tungsten-containing formate dehydrogenase (W-FDH) enzyme can be adsorbed to an electrode surface, to catalyse the efficient electrochemical reduction of CO2 to formate: catalysis is fast, thermodynamically reversible, and specific. Formate is an important feedstock, a stable intermediate in the conversion of CO2 to methanol and methane, and a viable energy source in its own right. This proposal aims to define the mechanism of the electrocatalytic reduction of CO2 to formate by W- FDH enzymes, using an interdisciplinary approach that combines state of the art electrochemical studies with an array of biochemical and mechanistic techniques. We aim also to 'narrow the gap' between the highly active enzymes and the most promising synthetic catalysts: we aim to provide proof-of-principle devices for exploiting the interconversion of CO2 and formate, and to compare the enzymes and synthetic catalysts directly. Therefore, we aim to establish an experimental and theoretical foundation for the development of robust synthetic catalysts for future application in carbon capture, energy storage, and regenerative fuel cell devices.

Planned Impact

The inexpensive capture and conversion of carbon dioxide into a valuable and sustainable energy carrier such as formic acid is of major and immediate economic interest. The UK White Paper on Energy 2007 underlined the fact that energy is essential for our lives and our economy. The reduction of carbon dioxide emissions, and ensuring a secure supply of clean and affordable energy were identified as major objectives. Thus, it is imperative that we react fast to develop renewable energy technologies. The target of this proposal is to lay a foundation for a new direction of industrially relevant research in the renewable production of carbon-based fuels. In this project we aim to understand how to activate and reduce CO2, by studying enzymes as model systems for the development of synthetic catalysts. At this stage, these are basic research aims, with academic beneficiaries, and commercialisation of a product is not an aim of the current proposal (as enzymes are very precious materials and not cost-competitive with current energy generation). But, after successful completion of this project, we will seek a close industrial partnership to develop a catalyst and devices, to apply the principles learnt from this BBSRC-funded project and to replace our enzymes with small molecule equivalents. Our ultimate aim is the production of a low-cost product capable of reducing carbon dioxide, ideally using sunlight. Our proposed research project combines a high degree of novelty and impact, with a high probability of achieving our stated goals, with immediate impact on UK academic science, and longer-term impact on UK industry. This project will establish a new academic partnership between Judy Hirst, Medical Research Council, and Erwin Reisner, University of Cambridge, forming a nucleus around which future networks and collaborations will be built. Within this project we will provide top-quality cross-disciplinary training for two BBSRC PDRAs (plus at least four University of Cambridge undergraduate students, who will undertake projects related to this proposal), to provide expertise in the development of alternative energy technologies, an area of critical scientific, technological and economic importance for the future.

Publications

10 25 50
 
Description Catalytic conversion of the greenhouse gas CO2 to fuels forms a new line of research in my group and this work is supported by this grant. We have recently reported on the reversible electrochemistry of a Mo-containing formate dehydrogenase, which provides a formidable entry point to this field.

We have shown that the electroactive enzyme formate dehydrogenase H from E. coli (EcFDH-H) is a highly active and efficient electrocatalyst capable of interconverting formate and CO2 when immobilised on an electrode. Voltammetry data revealed single points of zero net current which denote the CO2 reduction potential, which varies according to the Nernst equation. Quantification of formate production from CO2 reduction showed that catalysis is specific. This work established EcFDH-H as an attractive model system for the study of efficient electrocatalytic CO2 reduction.

Publications on this grant:
"Reversible interconversion of CO2 and formate by a molybdenum-containing formate dehydrogenase." Bassegoda, A.; Madden, C.; Wakerley, D. W.; Reisner, E.; Hirst, J. J. Am. Chem. Soc., 2014, 136, 15473-15476.

Sokol K, Mersch D, Hartmann V, Zhang J, Nowaczyk M, Rögner M..Reisner E. (2016). Rational wiring of photosystem II to hierarchical indium tin oxide electrodes using redox polymers. Energy Environ. Sci, 9 (12), pp. 3698-3709

The results of this award have contributed to the prepartation of an ERC grant
Exploitation Route We are still at an early stage of the project.
Sectors Energy,Environment

URL http://www-reisner.ch.cam.ac.uk/
 
Description First publication on this grant: "Reversible interconversion of CO2 and formate by a molybdenum-containing formate dehydrogenase." Bassegoda, A.; Madden, C.; Wakerley, D. W.; Reisner, E.; Hirst, J. J. Am. Chem. Soc., 2014, 136, 15473-15476. Sokol K, Mersch D, Hartmann V, Zhang J, Nowaczyk M, Rögner M..Reisner E. (2016). Rational wiring of photosystem II to hierarchical indium tin oxide electrodes using redox polymers. Energy Environ. Sci, 9 (12), pp. 3698-3709
 
Description Contribution to the "Solar Fuels Vision Statement"
Geographic Reach National 
Policy Influence Type Membership of a guideline committee
 
Description The reduction of carbon dioxide by enzymes: from biological studies to the development of bio-inspired synthetic catalysts 
Organisation Medical Research Council (MRC)
Department MRC Mitochondrial Biology Unit
Country United Kingdom of Great Britain & Northern Ireland (UK) 
Sector Public 
PI Contribution Electrochemical study of formate dehydrogense and demonstration of the reversibility of a molybdenum containing formate dehydrogenase from E. coli. We are also investigating biotechnological devices for the reduction of CO2 to formate using sunlight. The technological side of the project is performed in our lab in the Department of Chemistry.
Collaborator Contribution MRC constructed a strain of E. coli to purify a molybdenum containing formate dehydrogenase. All of the biological side of the project such as enzyme purification and DNA work is performed in her lab at the Mitochondrial Biology Unit
Impact "Reversible Interconversion of CO2 and Formate by a Molybdenum-Containing Formate Dehydrogenase" - article published in the Journal of the American Chemical Society DOI: 10.1021/ja508647u
Start Year 2012
 
Description 1st International Symposium on Energy Chemistry and Materials, Shanghai, China 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Plenary talk at the "1st International Symposium on Energy Chemistry and Materials"
To bring together an outstanding and diverse group of scientists at the forefront of research on the topics of solar energy conversion, chemical energy storage and conversion, optimal utilization of carbon resources and energy chemistry and materials.
Year(s) Of Engagement Activity 2015
 
Description 4th International Symposium on Solar Fuels and Solar Cells, Dalian China 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Invited Lecture in the Next-Generation Materials for Energy Chemistry: Faraday Discussion 176 (FD176). The Conference was organized by the Royal Society of Chemistry (RSC) and the Collaborative Innovation Center of Chemistry for Energy Materials (iChEM).

The following subjects have been covered:
• System integration from atomic, molecular, nano to meso scale towards optimized design of energy materials
• Design of material systems to optimize the energy enrichment of renewable sources for photochemical, thermal-to-electric conversion, and mechanical-to-electric conversion systems
• How interfacial chemistry takes place in the energy-related processes, focussing on design principles of efficient (electro) catalysts, in-situ characterization methods and theories in energy conversion and storage
• New materials and innovations for energy applications, including new light harvesting materials/semiconductors, plasmonics-enhanced energy conversion, new catalysts for biomass conversion, and energy-related bioinspiration/biomimetic systems
Year(s) Of Engagement Activity 2014
 
Description Facebook account with information about the group 
Form Of Engagement Activity Engagement focused website, blog or social media channel
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other audiences
Results and Impact Facebook account with information about the group to make the wider public aware of research work done by the Reisner Group
Year(s) Of Engagement Activity 2013,2014,2015,2016
URL https://www.facebook.com/ReisnerLab
 
Description ISACS17-Challenges in Chemical Renewable Energy, Rio de Janeiro, Brazil 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Plenary lecture at the 17th International Conference on Advancing the Chemical Sciences (ISACS 17). The theme of this conference is "Challenges in Chemical Renewable Energy".
Year(s) Of Engagement Activity 2015
URL http://www.rsc.org/isacs
 
Description Twitter account for the Reisner Group 
Form Of Engagement Activity Engagement focused website, blog or social media channel
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other audiences
Results and Impact Twitter account to spread the news about the Reisner Group's work
Year(s) Of Engagement Activity 2014,2015,2016
URL https://twitter.com/reisnerlab
 
Description Youtube Channel with Movies from the Reisner Group 
Form Of Engagement Activity Engagement focused website, blog or social media channel
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other audiences
Results and Impact Presenting short video's about the Reisner Group's Research work on youtube to make the wider public aware of the work and research of the group
Year(s) Of Engagement Activity 2013,2014,2015,2016
URL https://www.youtube.com/user/reisnerlab