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Highly quaternized polystyrene ionomers for high performance anion exchange membrane water electrolysers

Abstract

Alkaline anion exchange membrane (AEM) electrolysers to produce hydrogen from water are still at an early stage of development, and their performance is far lower than that of systems based on proton exchange membranes. Here, we report an ammonium-enriched anion exchange ionomer that improves the performance of an AEM electrolyser to levels approaching that of state-of-the-art proton exchange membrane electrolysers. Using rotating-disk electrode experiments, we show that a high pH (>13) in the electrode binder is the critical factor for improving the activity of the hydrogen- and oxygen-evolution reactions in AEM electrolysers. Based on this observation, we prepared and tested several quaternized polystyrene electrode binders in an AEM electrolyser. Using the binder with the highest ionic concentration and a NiFe oxygen evolution catalyst, we demonstrated performance of 2.7 A cm−2 at 1.8 V without a corrosive circulating alkaline solution. The limited durability of the AEM electrolyser remains a challenge to be addressed in the future.

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Fig. 1: Schematic of low-temperature water electrolysis cells.
Fig. 2: Impact of NaOH concentration on activities of electrocatalysts.
Fig. 3: The chemical structure of the polymeric materials used for the study.
Fig. 4: Impact of ionomer on AEM performance.
Fig. 5: AEM electrolyser performance catalysed by a PGM-free anode.
Fig. 6: Durability of AEM electrolysers catalysed by NiFe anodes.

Data availability

The authors declare that the data supporting the findings of this study are available within the paper, Supplementary Information and Source Data files. Further data beyond the immediate results presented here are available from the corresponding authors upon reasonable request.

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Acknowledgements

We gratefully acknowledge research support from the HydroGEN Advanced Water Splitting Materials Consortium, established as part of the Energy Materials Network under the US Department of Energy, Office of Energy Efficiency and Renewable Energy, Fuel Cell Technologies Office (program manager: D. Peterson). Los Alamos National Laboratory is operated by Triad National Security under the US Department of Energy, under contract no. 89233218CNA000001. Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, a wholly owned subsidiary of Honeywell International, for the US Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. Y.L. acknowledges research support from the JCDREAM. We thank A. Dattelbaum for constructive criticism of the manuscript.

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Contributions

Y.S.K. designed the experiments. D.L. carried out the electrochemical analysis and electrolyser test. E.J.P., E.D.B and C.F. synthesized the polymeric materials. W.Z., Q.S., Y.Z., H.T. and Y.L. synthesized and characterized the NiFe catalysts. A.S. and B.Z. synthesized and characterized the NiMo/C catalysts. D.L., E.J.P., W.Z., Y.L., A.S. and Y.S.K. contributed to writing the article. Y.S.K. initiated the collaborative project. Y.L., B.Z. and Y.S.K. supervised and guided the work.

Corresponding authors

Correspondence to Yuehe Lin or Yu Seung Kim.

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Supplementary Information

Supplementary Figs. 1–12, Tables 1–2 and refs. 1–2.

Source data

Source Data Fig. 2

Electrochemical data for plotting.

Source Data Fig. 4

Electrochemical data for plotting.

Source Data Fig. 5

Electrochemical data for plotting.

Source Data Fig. 6

Electrochemical data for plotting.

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Li, D., Park, E.J., Zhu, W. et al. Highly quaternized polystyrene ionomers for high performance anion exchange membrane water electrolysers. Nat Energy 5, 378–385 (2020). https://doi.org/10.1038/s41560-020-0577-x

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