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Bifunctional ionomers for efficient co-electrolysis of CO2 and pure water towards ethylene production at industrial-scale current densities

Abstract

Many CO2 electrolysers under development use liquid electrolytes (KOH solutions, for example), yet using solid-state polymer electrolytes can in principle improve efficiency and realize co-electrolysis of CO2 and pure water, avoiding corrosion and electrolyte consumption issues. However, a key challenge in these systems is how to favour production of multicarbon molecules, such as ethylene, which typically necessitates a strong alkaline environment. Here we use bifunctional ionomers as polymer electrolytes that are not only ionically conductive but can also activate CO2 at the catalyst–electrolyte interface and favour ethylene synthesis, while running on pure water. Specifically, we use quaternary ammonia poly(ether ether ketone) (QAPEEK), which contains carbonyl groups in the polymer chain, as the bifunctional electrolyte. An electrolyser running on CO2 and pure water exhibits a total current density of 1,000 mA cm2 at cell voltages as low as 3.73 V. At 3.54 V, ethylene is produced with the industrial-scale partial current density of 420 mA cm2 without any electrolyte consumption.

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Fig. 1: MEA electrolyser with 0.1 M KHCO3 anolyte.
Fig. 2: MEA electrolyser operated with pure water.
Fig. 3: Effects of ionomer coating on Cu surface towards the CO2RR.
Fig. 4: Synergetic catalytic mechanism of QAPEEK.
Fig. 5: MEA electrolysers with Cu-ionomer GDEs.
Fig. 6: MEA electrolyser using porous Cu–QAPEEK GDE.

Data availability

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

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Acknowledgements

All authors acknowledge funding from the National Natural Science Foundation of China (grant nos. 92045302, 21991150 and 21991154).

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Contributions

L.Z. and G.W. conceived and supervised the whole project. W.L., Z.Y. and G.W. made verification of the ideas and carried out the electrochemical experiments. Z.G. and X.W. carried out in situ ATR–SEIRAS measurements. F.W. carried out density functional theory calculations. H.P. and X.H. provided and characterized the materials. Z.L. assisted in data analysis. L.X. and J.L. provided valuable suggestions and assisted in the manuscript writing. L.Z., G.W., Z.Y. and W.L. wrote the paper.

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Correspondence to Gongwei Wang or Lin Zhuang.

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Nature Energy thanks Thomas Burdyny, Sichao Ma and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Extended data supporting the current study, including Supplementary Methods, Notes 1–5, Figs. 1–48 and Tables 1–11, are all provided in the Supplementary Information.

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Li, W., Yin, Z., Gao, Z. et al. Bifunctional ionomers for efficient co-electrolysis of CO2 and pure water towards ethylene production at industrial-scale current densities. Nat Energy 7, 835–843 (2022). https://doi.org/10.1038/s41560-022-01092-9

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