Abstract
The use of acidic electrolytes in CO2 reduction avoids costly carbonate loss. However, the energy efficiency of acid-fed electrolysers has been limited by high hydrogen production and operating potentials. We find that these stem from the lack of alkali cations at the catalyst surface, limiting CO2 and CO adsorption. In acid-fed membrane electrode assembly systems, the incorporation of these cations is challenging as there is no flowing catholyte. Here an interfacial cation matrix (ICM)–catalyst heterojunction is designed that directly attaches to the catalyst layer. The negatively charged nature of the ICM enriches the alkali cation concentration near the cathode surface, trapping generated hydroxide ions. This increases the local electric field and pH, increasing multi-carbon production. Integrating the ICM strategy with a tailored copper–silver catalyst enables selective ethanol production through a proton-spillover mechanism. We report a 45% CO2-to-ethanol Faradaic efficiency at 200 mA cm−2, carbon efficiency of 63%, full-cell ethanol energy efficiency of 15% (3-fold improvement over the best previous acidic CO2 reduction value) and energy cost of 260 GJ per tonne ethanol, the lowest among reported ethanol-producing CO2 electrolysers.
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Acknowledgements
We acknowledge funding for this work from the Government of Canada’s New Frontiers in Research Fund (NFRF), CANSTOREnergy project NFRFT-2022-00197, NRC and the University of Toronto Collaboration Centre Program in Green Energy Materials (CC-GEM, GEM-PRJ-01), Ontario Research Foundation Research Excellence Program and the CIFAR Bio-Inspired Solar Energy programme. D.S. acknowledges the support received from the Canada Research Chairs programme. A.S.Z. thanks NSERC for a Postdoctoral Fellowship. T.A. acknowledges graduate scholarships and fellowships from Hatch, NSERC and the University of Toronto. We also acknowledge Compute Canada for providing computing resources. We appreciate the Ontario Centre for the Characterization of Advanced Materials (OCCAM) at the University of Toronto for conducting microscopy characterizations. We thank M. Chehelamirani for his assistance in preparing the graphical abstract.
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D.S. and E.H.S. supervised the project. A.S.Z. conceived the idea and performed the electrochemical experiments and analyses. A.S.Z. and T.A. co-wrote the manuscript. F.L. performed the DFT calculations. F.L. and T.A. carried out the FEM simulation. R.D. assisted with the DFT calculation and manuscript writing. E.S., F.A., C.P.O., R.K.M. and D.Y. helped with electrochemical experiments. J.K. assisted with TEM imaging. A.O. and Y.Z. assisted with the catalyst preparation. P.P., D.K. and S.P. carried out the XAS measurements. M.Z. assisted with the schematics. L.F. carried out the X-ray diffraction measurement. C.M.G., J.P.E. and A.H.I. assisted with the research advice, discussions and editing. All authors contributed to the manuscript editing.
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Shayesteh Zeraati, A., Li, F., Alkayyali, T. et al. Carbon- and energy-efficient ethanol electrosynthesis via interfacial cation enrichment. Nat. Synth 4, 75–83 (2025). https://doi.org/10.1038/s44160-024-00662-x
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DOI: https://doi.org/10.1038/s44160-024-00662-x
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