Using Metal Oxides for the Photo-Electrochemical Oxygen Evolution Reaction

It is highly desirable that solar energy be efficiently and inexpensively directly converted to dispatchable fuels such as H₂. Photoelectrochemical water splitting represents a clean, energy conversion technology, which still has many fundamental barriers that must be addressed before it can be reduced to widespread practice. Whilst much research effort has been applied to these systems and conversion efficiencies greater than the 10% desired by the US DOE have been achieved, these high efficiency systems remain too unstable to achieve 10 years of operation and the stable systems remain at non-viable efficiencies. New electrodes or electrode combinations, developed by a close coupling between theory and experiment, are needed to enable a robust, efficient system for direct solar-induced water splitting.In this paper we will summarize all the approaches we have taken to date to create efficent photo-active electrodes for the photo-electrocatalystic evolution of oxygen from water.  Our first attempts were with heteropoly acid (HPA)modified titanium surfaces.  DFT calculations indcated that lacunary HPA could shift the absorption of titania in to the visible.  We then shifted our attention to sysytems usuing bismuth vanadate with the CoPI catalyst.  We successfully showed that molybdenum doped bismuth vanadate was an extremely active oxygen evolution catalyst but to improve its utility we added siica to make the elecrode transparent.  Laterly we have been investigating heterojuncyions with either tungsten oxide or copper tunngstate with bismuth vanadate.