Polyoxometalate electrocatalysts based on earth-abundant metals for efficient water oxidation in acidic media

Abstract

Water splitting is a promising approach to the efficient and cost-effective production of renewable fuels, but water oxidation remains a bottleneck in its technological development because it largely relies on noble-metal catalysts. Although inexpensive transition-metal oxides are competitive water oxidation catalysts in alkaline media, they cannot compete with noble metals in acidic media, in which hydrogen production is easier and faster. Here, we report a water oxidation catalyst based on earth-abundant metals that performs well in acidic conditions. Specifically, we report the enhanced catalytic activity of insoluble salts of polyoxometalates with caesium or barium counter-cations for oxygen evolution. In particular, the barium salt of a cobalt-phosphotungstate polyanion outperforms the state-of-the-art IrO2 catalyst even at pH < 1, with an overpotential of 189 mV at 1 mA cm–2. In addition, we find that a carbon-paste conducting support with a hydrocarbon binder can improve the stability of metal-oxide catalysts in acidic media by providing a hydrophobic environment.

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Figure 1: Electrochemical behaviour of Co-POM/CP electrodes.
Figure 2: Comparative electrochemical behaviour of catalyst/CP electrodes in acidic media, highlighting the superior activity of Co-POM modified electrodes for oxygen evolution.
Figure 3: Stability and benchmarking of catalyst/CP electrodes.

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Acknowledgements

This work was supported by the European Union (project ERC StG, grant CHEMCOMP, no. 279313), the Spanish Ministerio de Economía y Competitividad (MINECO; through projects CTQ2015-71287-R, CTQ2014-52774-P and the Severo Ochoa Excellence Accreditation 2014-2018 SEV-2013-0319), the Generalitat de Catalunya (2014-SGR-797 and 2014SGR-199) and the CERCA Programme/Generalitat de Catalunya. J.M.P. acknowledges the ICREA Foundation for an ICREA Academia award. M.B.A. acknowledges the Generalitat Catalana (AGAUR) for a predoctoral fellowship. The authors also thank Á. Reyes-Carmona for discussions.

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J.R.G.-M. proposed the concept. J.R.G.-M., M.B.-A. and J.S.-L. designed the experiments. M.B.-A. and J.S.-L. performed the experiments. All authors participated in data analysis and co-wrote the manuscript.

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Correspondence to J. R. Galan-Mascaros.

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Blasco-Ahicart, M., Soriano-López, J., Carbó, J. et al. Polyoxometalate electrocatalysts based on earth-abundant metals for efficient water oxidation in acidic media. Nature Chem 10, 24–30 (2018). https://doi.org/10.1038/nchem.2874

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