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Direct seawater electrolysis by adjusting the local reaction environment of a catalyst

Abstract

The use of vast amounts of high-purity water for hydrogen production may aggravate the shortage of freshwater resources. Seawater is abundant but must be desalinated before use in typical proton exchange membrane (PEM) electrolysers. Here we report direct electrolysis of real seawater that has not been alkalised nor acidified, achieving long-term stability exceeding 100 h at 500 mA cm−2 and similar performance to a typical PEM electrolyser operating in high-purity water. This is achieved by introducing a Lewis acid layer (for example, Cr2O3) on transition metal oxide catalysts to dynamically split water molecules and capture hydroxyl anions. Such in situ generated local alkalinity facilitates the kinetics of both electrode reactions and avoids chloride attack and precipitate formation on the electrodes. A flow-type natural seawater electrolyser with Lewis acid-modified electrodes (Cr2O3–CoOx) exhibits the industrially required current density of 1.0 A cm−2 at 1.87 V and 60 °C.

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Fig. 1: Evaluation of Cr2O3–CoOx in direct seawater electrolysis based on two-electrode configuration.
Fig. 2: Anodic activity and chlorine chemistry of Cr2O3–CoOx in natural seawater based on a three-electrode configuration.
Fig. 3: Investigation on the origin of locally generated OH in natural seawater.
Fig. 4: Cathodic activity and avoiding precipitate formation on Cr2O3–CoOx in natural seawater.
Fig. 5: Performance of flow-type natural seawater electrolyser.

Data availability

The datasets analysed and generated during the current study are included in the paper and Supplementary Information. Source data are provided with this paper.

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Acknowledgements

This work was supported by the Natural Science Foundation of China (52071231 and 51722103) and the Natural Science Foundation of Tianjin city (19JCJQJC61900). Y.Z. acknowledges funding from the Australian Research Council (DP190103472 and FT200100062). S.-Z.Q. acknowledges funding from the Australian Research Council (FL170100154 and DP220102596). Calculations were performed on TianHe-1A at the National Supercomputer Center, Tianjin. We thank Weihua Wang from Nankai University for constructive suggestions.

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Contributions

T.L., Y.Z. and S.-Z.Q. conceived the project and designed the experiments. J.G. and K.D. performed the experiments. Z.H., C.Z. and T.L. carried out the DFT calculations. J.M. carried out the TEM and HAADF-STEM characterizations. T.L., Y.Z. and J.G. wrote the manuscript. S.-Z.Q., T.L. and M.J. reviewed and corrected the manuscript. All authors discussed the results and commented on the manuscript.

Corresponding authors

Correspondence to Shi-Zhang Qiao or Tao Ling.

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Nature Energy thanks Wen-Feng Lin and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Guo, J., Zheng, Y., Hu, Z. et al. Direct seawater electrolysis by adjusting the local reaction environment of a catalyst. Nat Energy 8, 264–272 (2023). https://doi.org/10.1038/s41560-023-01195-x

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