Abstract
Seawater electrolysis powered by renewable electricity provides an attractive strategy for producing green hydrogen1,2,3,4,5. However, direct seawater electrolysis faces many challenges, primarily arising from corrosion and competing reactions at the anode caused by the abundance of halide ions (Cl−, Br−) in seawater6. Previous studies3,6,7,8,9,10,11,12,13,14 on seawater electrolysis have mainly focused on the anode development, because the cathode operates at reducing potentials, which is not subject to electrode dissolution or chloride corrosion reactions during seawater electrolysis11,15. However, renewable energy sources are intermittent, variable and random, which cause frequent start–shutdown operations if renewable electricity is used to drive seawater electrolysis. Here we first unveil dynamic evolution and degradation of seawater splitting cathode in intermittent electrolysis and, accordingly, propose construction of a catalyst’s passivation layer to maintain the hydrogen evolution performance during operation. An in situ-formed phosphate passivation layer on the surface of NiCoP–Cr2O3 cathode can effectively protect metal active sites against oxidation during frequent discharge processes and repel halide ion adsorption on the cathode during shutdown conditions. We demonstrate that electrodes optimized using this design strategy can withstand fluctuating operation at 0.5 A cm−2 for 10,000 h in alkaline seawater, with a voltage increase rate of only 0.5% khr−1. The newly discovered challenge and our proposed strategy herein offer new insights to facilitate the development of practical seawater splitting technologies powered by renewable electricity.
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Change history
13 March 2025
In the PDF version of this article initially published, images in panels in Fig. 2d, e, h were incomplete and are now updated in the online PDF.
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Acknowledgements
We acknowledge H. Dai and Y. Kuang for the helpful guidance, L. Gu, T. Zhang and Y. Lu for the help on HAADF-STEM characterization and D. Lu for the help on TOF-SIMS characterization. X.S. and D.Z. acknowledge financial support from the National Key Research and Development Project (2022YFA1504000), the National Natural Science Foundation of China (21935001), Beijing Natural Science Foundation (Z210016), a long-term subsidy from China’s Ministry of Finance and the Ministry of Education. D.Z. acknowledges financial support from the Young Elite Scientists Sponsorship Program by CAST (2022QNRC001). B.L. acknowledges financial support from the City University of Hong Kong startup fund (9020003), ITF-RTH-Global STEM Professorship (9446006) and JC STEM lab of Advanced CO2 Upcycling (9228005).
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X.S., B.L. and D.Z. supervised the project. Q.S. and S.W. conceived the idea and carried out the experiments and also conducted materials synthesis and electrochemical measurements. Q.S. wrote the paper. X.G., T.L. and Z. Zhuang helped with the anion exchange membrane test. L.Y., S.L. and X.G. helped with the stability test. H.L., Y.F. and Z. Zhang performed the density functional theory calculations.
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Sha, Q., Wang, S., Yan, L. et al. 10,000-h-stable intermittent alkaline seawater electrolysis. Nature 639, 360–367 (2025). https://doi.org/10.1038/s41586-025-08610-1
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DOI: https://doi.org/10.1038/s41586-025-08610-1
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