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Abstract
Hydrogen is essential to several key industrial processes and could play a major role as an energy carrier in a future ‘hydrogen economy’. Although the majority of the world's hydrogen supply currently comes from the reformation of fossil fuels, its generation from water using renewables-generated power could provide a hydrogen source without increasing atmospheric CO2 levels. Conventional water electrolysis produces H2 and O2 simultaneously, such that these gases must be generated in separate spaces to prevent their mixing. Herein, using the polyoxometalate H3PMo12O40, we introduce the concept of the electron-coupled-proton buffer (ECPB), whereby O2 and H2 can be produced at separate times during water electrolysis. This could have advantages in preventing gas mixing in the headspaces of high-pressure electrolysis cells, with implications for safety and electrolyser degradation. Furthermore, we demonstrate that temporally separated O2 and H2 production allows greater flexibility regarding the membranes and electrodes that can be used in water-splitting cells. Using a polyoxometalate as an electron-coupled-proton buffer, the decoupling of the water oxidation and proton reduction half reactions of electrolytic water splitting is achieved. This allows O2 and H2 to be produced separately in both time and space. The implications of these findings for electrolyser design and low-cost hydrogen production from water are discussed. Cite this article
Symes, M., Cronin, L. Decoupling hydrogen and oxygen evolution during electrolytic water splitting using an electron-coupled-proton buffer. Nature Chem 5, 403–409 (2013). https://doi.org/10.1038/nchem.1621 