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CO electrolysers with 51% energy efficiency towards C2+ using porous separators

Nature Energy volume 10, pages 1197–1204 (2025)Cite this article

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Abstract

Electrochemical CO2 reduction can generate multi-carbon (C2+) products via a CO2-to-CO cascade followed by CO reduction (COR). However, COR energy efficiency remains below 40% due to sluggish ion transport within charge-selective membranes. Here we introduce an uncharged porous separator that enables facile transport of both ion types, reducing ohmic resistance and superconcentrating cations at the catalyst surface—lowering COR voltage by 150 mV at 200 mA cm−2. In previous electrolyser designs, porous separators were limited by cathode-to-anode H2 crossover; the low diffusivity of C2H4 and CO in water allows a separator three times thinner and 1.6 times more porous, markedly reducing overpotential. Operating at elevated temperatures with a nickel–iron-based anode further lowers voltage by 330 mV, leading to a full-cell voltage of 1.95 V at 200 mA cm−2 and an energy efficiency of 51% to C2+ products sustained over 250 h. The system also achieves a CO single-pass conversion of 97% and a C2H4 concentration of 87 wt% in the product gas stream.

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Fig. 1: Performance of the MEA with an AEM.
Fig. 2: Performance of the MEA with a separator.
Fig. 3: Mechanistic understanding of separator performance.
Fig. 4: Optimization of the MEA with a separator.
Fig. 5: Stability and single-pass conversion of the MEA with a separator.

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Data availability

All data supporting the findings of this study are available within the paper and Supplementary Information files. Source data are provided with this paper.

References

  1. O'Brien, C. P. et al. CO2 electrolyzers. Chem. Rev. 124, 3648–3693 (2024).

    Article  Google Scholar 

  2. Chen, Y. et al. Catalyst design for electrochemical CO2 reduction to ethylene. Matter 7, 25–37 (2024).

    Article  Google Scholar 

  3. Shin, H., Hansen, K. U. & Jiao, F. Techno-economic assessment of low-temperature carbon dioxide electrolysis. Nat. Sustain. 4, 911–919 (2021).

    Article  Google Scholar 

  4. Jouny, M., Luc, W. & Jiao, F. General techno-economic analysis of CO2 electrolysis systems. Ind. Eng. Chem. Res. 57, 2165–2177 (2018).

    Article  Google Scholar 

  5. Chen, X. et al. Electrochemical CO2-to-ethylene conversion on polyamine-incorporated Cu electrodes. Nat. Catal. 4, 20–27 (2021).

    Article  Google Scholar 

  6. García de Arquer, F. P. et al. CO2 electrolysis to multicarbon products at activities greater than 1 A cm−2. Science 367, 661–666 (2020).

    Article  Google Scholar 

  7. Zhong, M. et al. Accelerated discovery of CO2 electrocatalysts using active machine learning. Nature 581, 178–183 (2020).

    Article  Google Scholar 

  8. Dinh, C. T. et al. CO2 electroreduction to ethylene via hydroxide-mediated copper catalysis at an abrupt interface. Science 360, 783–787 (2018).

    Article  Google Scholar 

  9. Huang, J. E. et al. CO2 electrolysis to multicarbon products in strong acid. Science 372, 1074–1078 (2021).

    Article  Google Scholar 

  10. Ozden, A. et al. Carbon-efficient carbon dioxide electrolysers. Nat. Sustain. 5, 563–573 (2022).

    Article  Google Scholar 

  11. Fan, M. et al. Cationic-group-functionalized electrocatalysts enable stable acidic CO2 electrolysis. Nat. Catal. 6, 763–772 (2023).

    Article  Google Scholar 

  12. O’Brien, C. P. et al. Single pass CO2 conversion exceeding 85% in the electrosynthesis of multicarbon products via local CO2 regeneration. ACS Energy Lett. 6, 2952–2959 (2021).

    Article  Google Scholar 

  13. Sisler, J. et al. Ethylene electrosynthesis: a comparative techno-economic analysis of alkaline vs membrane electrode assembly vs CO2-CO–C2H4 tandems. ACS Energy Lett. 6, 997–1002 (2021).

    Article  Google Scholar 

  14. Ozden, A. et al. Cascade CO2 electroreduction enables efficient carbonate-free production of ethylene. Joule 5, 706–719 (2021).

    Article  Google Scholar 

  15. Li, J. et al. Hydroxide is not a promoter of C2+ product formation in the electrochemical reduction of CO on copper. Angew. Chem. Int. Ed. 132, 4494–4499 (2020).

    Article  Google Scholar 

  16. Jouny, M., Luc, W. & Jiao, F. High-rate electroreduction of carbon monoxide to multi-carbon products. Nat. Catal. 1, 745–755 (2018).

    Google Scholar 

  17. Ripatti, D. S., Veltman, T. R. & Kanan, M. W. Carbon monoxide gas diffusion electrolysis that produces concentrated C2 products with high single-pass conversion. Joule 3, 240–256 (2019).

    Article  Google Scholar 

  18. Ozden, A. et al. Energy- and carbon-efficient CO2/CO electrolysis to multicarbon products via asymmetric ion migration–adsorption. Nat. Energy 8, 179–190 (2023).

    Article  Google Scholar 

  19. Wang, X. et al. Efficient electrosynthesis of n-propanol from carbon monoxide using a Ag–Ru–Cu catalyst. Nat. Energy 7, 170–176 (2022).

    Article  Google Scholar 

  20. Wu, H. et al. Selective and energy-efficient electrosynthesis of ethylene from CO2 by tuning the valence of Cu catalysts through aryl diazonium functionalization. Nat. Energy 9, 422–433 (2024).

  21. Salvatore, D. A. et al. Designing anion exchange membranes for CO2 electrolysers. Nat. Energy 6, 339–348 (2021).

    Article  Google Scholar 

  22. Hasa, B. et al. Benchmarking anion-exchange membranes for electrocatalytic carbon monoxide reduction. Chem. Catal. 3, 100450 (2023).

    Google Scholar 

  23. Du, N. et al. Anion-exchange membrane water electrolyzers. Chem. Rev. 122, 11830–11895 (2022).

    Article  Google Scholar 

  24. Henkensmeier, D. et al. Overview: State-of-the-art commercial membranes for anion exchange membrane water electrolysis. J. Electrochem. Energy Convers. Storage 18, 024001 (2021).

    Article  Google Scholar 

  25. Gilliam, R. J., Graydon, J. W., Kirk, D. W. & Thorpe, S. J. A review of specific conductivities of potassium hydroxide solutions for various concentrations and temperatures. Int. J. Hydrog. Energy 32, 359–364 (2007).

    Article  Google Scholar 

  26. Monteiro, M. C. O. et al. Absence of CO2 electroreduction on copper, gold and silver electrodes without metal cations in solution. Nat. Catal. 4, 654–662 (2021).

    Article  Google Scholar 

  27. Zi, X. et al. Breaking K+ concentration limit on Cu nanoneedles for acidic electrocatalytic CO2 reduction to multi-carbon products. Angew. Chem. Int. Ed. 62, e202309351 (2023).

    Article  Google Scholar 

  28. Lee, H. I. et al. The synthesis of a Zirfon-type porous separator with reduced gas crossover for alkaline electrolyzer. Int. J. Energy Res. 44, 1875–1885 (2020).

    Article  Google Scholar 

  29. Ha, T. H., Kim, J., Choi, H. & Oh, J. Selective zero-gap CO2 reduction in acid. ACS Energy Lett. 9, 4835–4842 (2024).

  30. Perazio, A., Schreiber, M. W., Creissen, C. E. & Fontecave, M. Low-voltage acidic CO2 reduction enabled by a diaphragm-based electrolyzer. ChemElectroChem 11, e202400045 (2024).

    Article  Google Scholar 

  31. Xu, Q. et al. Integrated reference electrodes in anion-exchange-membrane electrolyzers: impact of stainless-steel gas-diffusion layers and internal mechanical pressure. ACS Energy Lett. 6, 305–312 (2021).

    Article  Google Scholar 

  32. Hu, C., Zhang, L. & Gong, J. Recent progress made in the mechanism comprehension and design of electrocatalysts for alkaline water splitting. Energy Environ. Sci. 12, 2620–2645 (2019).

    Article  Google Scholar 

  33. Xie, X. et al. Oxygen evolution reaction in alkaline environment: material challenges and solutions. Adv. Funct. Mater. 32, 2110036 (2022).

    Article  Google Scholar 

  34. Wang, N. et al. Boride-derived oxygen-evolution catalysts. Nat. Commun. 12, 6089 (2021).

    Article  Google Scholar 

  35. Varcoe, J. R. & Slade, R. C. T. Prospects for alkaline anion-exchange membranes in low temperature fuel cells. Fuel Cells 5, 187–200 (2005).

    Article  Google Scholar 

  36. Xue, J. et al. High-temperature anion-exchange membrane fuel cells with balanced water management and enhanced stability. Joule 8, 1457–1477 (2024).

    Article  Google Scholar 

  37. Vos, R. E. & Koper, M. T. M. The effect of temperature on the cation-promoted electrochemical CO2 reduction on gold. ChemElectroChem 9, e202200239 (2022).

    Article  Google Scholar 

  38. Vos, R. E. et al. How temperature affects the selectivity of the electrochemical CO2 reduction on copper. ACS Catal. 13, 8080–8091 (2023).

    Article  Google Scholar 

  39. Li, J. et al. Constraining CO coverage on copper promotes high-efficiency ethylene electroproduction. Nat. Catal. 2, 1124–1131 (2019).

    Article  Google Scholar 

  40. Tan, Y. C., Lee, K. B., Song, H. & Oh, J. Modulating local CO2 concentration as a general strategy for enhancing C–C coupling in CO2 electroreduction. Joule 4, 1104–1120 (2020).

    Article  Google Scholar 

  41. da Cunha, S. C. & Resasco, J. Maximizing single-pass conversion does not result in practical readiness for CO2 reduction electrolyzers. Nat. Commun. 14, 5513 (2023).

    Article  Google Scholar 

  42. Prajapati, A. et al. CO2-free high-purity ethylene from electroreduction of CO2 with 4% solar-to-ethylene and 10% solar-to-carbon efficiencies. Cell Rep. Phys. Sci. 3, 101053 (2022).

    Article  Google Scholar 

  43. Gabardo, C. M. et al. Continuous carbon dioxide electroreduction to concentrated multi-carbon products using a membrane electrode assembly. Joule 3, 2777–2791 (2019).

  44. Liu, W. et al. Electrochemical CO2 reduction to ethylene by ultrathin CuO nanoplate arrays. Nat. Commun. 13, 1877 (2022).

    Article  Google Scholar 

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Acknowledgements

D.S. acknowledges support from the Canada Research Chairs Program. R.K.M. thanks the Natural Sciences and Engineering Research Council (NSERC), Hatch and the Government of Ontario for their support through graduate scholarships. This work is financially supported by the Natural Sciences and Engineering Research Council of Canada (NSERC) and TOTAL SE.

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Author notes

  1. These authors contributed equally: Rui Kai Miao, Mengyang Fan, Ning Wang.

Authors and Affiliations

  1. Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Ontario, Canada

    Rui Kai Miao, Mengyang Fan, Yong Zhao, Feng Li, Min Liu, Fatemeh Arabyarmohammadi, Puhua Sun, Jinhong Wu, Jiheon Kim, Colin P. O’Brien, Yurou Celine Xiao, Zunmin Guo, Panagiotis Papangelakis, Ali Shayesteh Zeraati, Yi Xu & David Sinton

  2. Department of Electrical and Computer Engineering, University of Toronto, Toronto, Ontario, Canada

    Ning Wang, Yongxiang Liang, Weiyan Ni, Ke Xie, Yuanjun Chen, Jianan Erick Huang, Jiheon Kim & Edward H. Sargent

  3. Department of Chemical Engineering, Smith Engineering, Queen’s University, Kingston, Ontario, Canada

    Cao-Thang Dinh

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Contributions

E.H.S. and D.S. supervised the work. R.K.M. conceived the idea. R.K.M. designed and carried out all the experiments with help from M.F., N.W. and Y.Z. R.K.M. prepared the manuscript. N.W. synthesized the NiFe–B anode material. F.L. performed the one-dimensional simulation. F.A. designed the electrolyser incorporating a reference electrode. C.P.O., P.P. and A.S.Z. prepared the hydrophobic carbon substrate. Y.L., W.N., K.X., Y.C., P.S., J.E.H. and J.W. assisted with experiments. M.L., J.K., Y.C.X., Y.X. and C.-T.D. contributed to data analysis and discussions. All authors discussed the results and approved the final version.

Corresponding authors

Correspondence to Edward H. Sargent or David Sinton.

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Competing interests

There is a US provisional patent application (US 63/656,427) titled “Interposed electrode assembly for electroreduction of carbon oxides to C2+ products”, filed by R.K.M., D.S. and E.H.S. and their institutions. The remaining authors declare no competing interests.

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Nature Energy thanks Joel Ager III, Charles Creissen and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Miao, R.K., Fan, M., Wang, N. et al. CO electrolysers with 51% energy efficiency towards C2+ using porous separators. Nat Energy 10, 1197–1204 (2025). https://doi.org/10.1038/s41560-025-01846-1

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