Photoelectrolysis at the oxide-electrolyte interface as interpreted through the ‘transition’ layer model

• Published in: Surface science 1980-01, Vol.101 (1), p.214-223
• Main Authors: Kalia, R.K., Weber, Michael F., Schumacher, L., Dignam, M.J.
• Format: Article
• Language: English
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/0039-6028(80)90614-7

A transition layer model of the oxide-electrolyte interface, proposed earlier by one of us, is outlined and then examined in the light of experimental data relating primarily to photoelectrolysis of water at semiconducting oxide electrodes. The model provides useful insight into the behaviour of the system and allows a calculation of thc minimum bias potential needed for photoelectrolysis, thus illuminating the origin of the requirement for such an external bias. In order to electrolyse water without a bias, the model requires an n-type oxide to be sufficiently reduced so that it is thermodynamically capable of chemically reducing water to produce hydrogen at 1 atm pressure. Similarly, for bias-free operation, a p-type metal oxide must be thermodynamically unstable with respect to the release of oxygen at 1 atm pressure. In the face of these requirements it is apparent that oxide stability is bound to be in general a serious problem for nonstoichiometric single metal oxides.