Abstract
The electrochemical reduction of carbon dioxide (CO2) can produce value-added chemicals and fuels with reduced greenhouse gas emissions by leveraging renewable electricity. However, the economic viability of this technology is limited by high full-cell voltages due to the combination of various materials and processes between the anode and the cathode. Here we analyse voltage distributions within systems that are candidates for achieving energy-efficient CO2 electroreduction: CO2 reduction (CO2R) in acidic media, cascade CO2R-CO electroreduction and CO2 reactive capture. By measuring and resolving the individual contributions to the overall cell voltage, we show that the cascade approach is, at present, the most energy-efficient candidate for achieving economic and scalable CO2R. The membrane and cathode overpotentials dominate in direct CO2R approaches (acidic CO2R and CO2R with forward-biased bipolar membranes). By contrast, the reactive capture approach benefits from a low membrane overpotential (<0.2 V) as a result of the high proton conductivity of the cation exchange membrane, with remaining overpotentials at the cathode, anode and intrinsic Nernstian pH gradient. Applying these insights, we optimize the CO electroreduction system to reach a full-cell voltage of 1.95 V at 200 mA cm−2. Our findings offer a framework for steering the advance of more energy-efficient and scalable CO2R electrolysers.
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All data supporting the findings of this study are available within the paper and Supplementary Information. Source data are provided with this paper.
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Acknowledgements
We gratefully acknowledge funding from the Government of Canada’s New Frontiers in Research Fund (CANSTOREnergy Project NFRFT-2022-00197), the Natural Sciences and Engineering Research Council of Canada and the Canada Research Chairs Program. We also received support from Suncor Canada. F.A. thanks Hatch, CGEN and the University of Toronto for their support through graduate scholarships.
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D.S., E.H.S. and R.K.M. supervised the project. F.A. designed the research. F.A., R.K.M. and A.S.Z. carried out all the experiments. F.A. and R.K.M. analysed the data and wrote the paper. M.Z. performed the COMSOL model simulation. R.K.M. and C.P.O’B. gave guidance on scenario selection and analyses. T.A., J.A. and G.L. assisted with the experiments. T.A. and F.L. assisted with the COMSOL simulation. R.D. and M.F. assisted with the experimental design. All authors contributed to the discussions and assisted during the preparation of the paper.
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Nature Sustainability thanks Feng Jiao, Hunter Simonson and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.
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Arabyarmohammadi, F., Miao, R.K., Zeraati, A.S. et al. Voltage distribution within carbon dioxide reduction electrolysers. Nat Sustain (2025). https://doi.org/10.1038/s41893-025-01643-4
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DOI: https://doi.org/10.1038/s41893-025-01643-4
