Decoupled electrolysis using a silicotungstic acid electron-coupled-proton buffer in a proton exchange membrane cell

Chisholm, G. , Cronin, L. and Symes, M. D. (2020) Decoupled electrolysis using a silicotungstic acid electron-coupled-proton buffer in a proton exchange membrane cell. Electrochimica Acta, 331, 135255. (doi: 10.1016/j.electacta.2019.135255)

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The storage of renewably-generated energy as hydrogen via the electrolysis of water is a fundamental cornerstone of a sustainable hydrogen economy. Conventional electrolysers usually require stable power inputs in order to operate effectively and safely and so may be unsuited to harnessing renewable power, which is often intermittent and diffuse. Electrolysis mediated by Electron-Coupled-Proton Buffers has the potential to overcome some of the challenges surrounding electrolysis using low and/or sporadic power inputs (especially those related to gas crossover) as the use of Electron-Coupled-Proton Buffers allows the oxygen and hydrogen evolution reactions to be completely decoupled from one another. Herein, we show that silicotungstic acid can be used as an Electron-Coupled-Proton Buffer in a proton exchange membrane cell, decoupling the hydrogen and oxygen evolution reactions at steady state current densities as high as 500 mA cm−2. O2 and H2 can be produced continuously by this system by cycling a fixed volume of the Electron-Coupled-Proton Buffer solution. Even at current densities as low as 25 mA cm−2, the level of hydrogen in the oxygen stream is <0.4%, whereas a conventional proton exchange membrane electrolyser operating at this current density produces oxygen containing nearly 2% hydrogen (unacceptable for most applications). Furthermore, using silicotungstic acid as an Electron-Coupled-Proton Buffer also confers greater tolerance to non-deionised water inputs and reduces fluoride release from the perfluorosulfonated membrane (a marker for membrane degradation) relative to a conventional proton exchange membrane electrolyser. Together, these results highlight the promise and potential advantages of Electron-Coupled-Proton Buffers (and silicotungstic acid in particular) for the electrolytic production of hydrogen and oxygen over a wide range of current densities, such as might be produced by renewable power inputs.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Chisholm, Dr Greig and Symes, Professor Mark and Cronin, Professor Lee
Authors: Chisholm, G., Cronin, L., and Symes, M. D.
College/School:College of Science and Engineering > School of Chemistry
Journal Name:Electrochimica Acta
ISSN (Online):1873-3859
Published Online:13 November 2019
Copyright Holders:Copyright © 2019 The Authors
First Published:First published in Electrochimica Acta 331: 135255
Publisher Policy:Reproduced under a Creative Commons License
Data DOI:10.5525/gla.researchdata.905

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
173495Driving energetically uphill processes using metal-ligand coordination complexesMark SymesThe Royal Society (ROYSOC)UF150104Chemistry
167864Energy and the Physical Sciences: Hydrogen Production using a Proton Electron BufferLeroy CroninEngineering and Physical Sciences Research Council (EPSRC)EP/K023004/1Chemistry
301241Ultra-Reduced Polyoxometalates as Electron-Coupled-Proton-Systems for Energy StorageLeroy CroninEngineering and Physical Sciences Research Council (EPSRC)EP/R020914/1Chemistry