Water oxidation is a key reaction for the conversion of solar energy into chemical fuels, but effective water-oxidation catalysts are often based on rare and costly precious metals such as Pt, Ir or Ru. Developing strategies based on earth-abundant metals is important to explore critical aspects of this reaction, and to see whether different and more efficient applications are possible for energy systems. Herein, we present an approach to tuning a redox-active electrocatalyst based on the doping of molybdenum into the tungsten framework of [Co4(H2O)2(PW9O34)2]10–, known as the Weakley sandwich. The Mo-doped framework was confirmed by X-ray crystallography, electrospray ionization mass spectrometry and inductively coupled plasma optical emission spectrometry studies. The doping of molybdenum into the robust Weakley sandwich framework leads to the oxidation of water at a low onset potential, and with no catalyst degradation, whereby the overpotential of the oxygen evolution reaction is lowered by 188 mV compared with the pure tungsten framework.

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We acknowledge J. Mathieson and D. Castro-Spencer for their kind help and support in acquiring the ESI-IM-MS data. We thank L. MacDonald for offering supportive discussion on the electrochemistry. We also thank J. M. Poblet and J. Carbò for helpful discussion on the POM design, characterization and electrocatalysis. We gratefully acknowledge financial support from the Engineering and Physical Sciences Research Council (grant nos EP/H024107/1, EP/J015156/1, EP/K021966/1, EP/L015668/1, EP/L023652/1), the European Research Council (project 670467 SMART-POM) and the University of Glasgow. This work was partially funded by the Spanish Ministerio de Economia y Competitividad (MINECO) through projects CTQ2015-71287-R and the Severo Ochoa Excellence Accreditation 2014-2018 SEV-2013-0319; the Generalitat de Catalunya (2014-SGR-797) and the Centres de Recera de Catalunya Programme/Generalitat de Catalunya. We also thank Chemistry and Molecular Sciences and Technologies European Cooperation in Science & Technology Action CM1203.

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Author notes

  1. These authors contributed equally to this work: Mercè Martin-Sabi and Joaquín Soriano-López.


  1. WestCHEM, School of Chemistry, University of Glasgow, Glasgow, UK

    • Mercè Martin-Sabi
    • , Ross S. Winter
    • , Jia-Jia Chen
    • , Laia Vilà-Nadal
    • , De-Liang Long
    •  & Leroy Cronin
  2. Institut Català d’Investigació Química (ICIQ), Tarragona, Spain

    • Joaquín Soriano-López
    •  & José Ramón Galán-Mascarós
  3. ICREA, Barcelona, Spain

    • José Ramón Galán-Mascarós


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L.C. conceived the original concept and both L.C. and J.R.G.-M. designed the project and together with L.V.-N. coordinated the efforts of the research team. M.M.-S. and J.S.-L. contributed equally. M.M.-S. and J.S.-L. synthesized the compounds, M.M.-S. characterized the compounds electrochemically, analysed the ESI-IM-MS and determined the formula for each compound. J.S.-L. measured the oxygen evolution. R.S.W. and J.-J.C. supervised directly the electrochemistry and the synthetic work and characterization analysis. D.-L.L. finalized the X-ray structures. M.M.-S., L.V.-N. and L.C. co-wrote the paper with input from all the authors.

Competing interests

The authors declare no competing interests.

Corresponding authors

Correspondence to José Ramón Galán-Mascarós or Leroy Cronin.

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    Supplementary Methods, Supplementary Figures 1–10, Supplementary Tables 1–19, Supplementary References

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