Low pH electrolytic water splitting using earth abundant metastable catalysts that self-assemble in situ

Bloor, L.G., Molina-Sanchez, P.I., Symes, M. and Cronin, L. (2014) Low pH electrolytic water splitting using earth abundant metastable catalysts that self-assemble in situ. Journal of the American Chemical Society, 136(8), pp. 3304-3311. (doi:10.1021/ja5003197)

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Abstract

Typical catalysts for the electrolysis of water at low pH are based on precious metals (Pt for the cathode and IrO2 or RuO2 for the anode). However, these metals are rare and expensive, and hence lower cost and more abundant catalysts are needed if electrolytically produced hydrogen is to become more widely available. Herein, we show that electrode-film formation from aqueous solutions of first row transition metal ions at pH 1.6 can be induced under the action of an appropriate cell bias and that in the case of cobalt voltages across the cell in excess of 2 V lead to the formation of a pair of catalysts that show functional stability for oxygen evolution and proton reduction for over 24 h. We show that these films are metastable and that if the circuit is opened, they redissolve into the electrolyte bath with concomitant O2 and H2 evolution, such that the overall Faradaic efficiency for charge into the system versus amounts of gases obtained approaches unity for both O2 and H2. This work highlights the ability of first row transition metals to mediate heterogeneous electrolytic water splitting in acidic media by exploiting, rather than trying to avoid, the natural propensity of the catalysts to dissolve at the low pHs used. This in turn we hope will encourage others to examine the promise of metastable electrocatalysts based on abundant elements for a range of reactions for which they have traditionally been overlooked on account of their perceived instability under the prevailing conditions.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Molina-Sanchez, Mr Pedro and Symes, Dr Mark and Bloor, Dr Leanne and Cronin, Professor Lee
Authors: Bloor, L.G., Molina-Sanchez, P.I., Symes, M., and Cronin, L.
College/School:College of Science and Engineering > School of Chemistry
Journal Name:Journal of the American Chemical Society
Publisher:American Chemical Society
ISSN:0002-7863
ISSN (Online):1520-5126

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