Oxidative energy storage ability of a TiO2-Ni(OH)2 bilayer photocatalyst.

A TiO2-coated indium tin oxide electrode was further coated with Ni(OH)2 by electrodeposition to obtain a TiO2-Ni(OH)2 bilayer film. Upon irradiation of the bilayer film with UV light in a pH 10 buffer, the Ni(OH)2 layer was oxidized, and it turned from colorless to brown; oxidative energy was stored in the layer. The potential of the oxidative energy thus stored was about +0.7 V versus Ag|AgCl. The stored energy could be reversibly taken out of the film by chemical and electrochemical means. The photooxidized Ni(OH)2 was rereduced by alcohols, aldehydes, phenol, I-, H2O2, formate, and acetone.