Photoelectrochemical Oxidation of Formate Ions on Nickel−Titanium Dioxide Nanocomposite Electrodes: Unusually High “Current Doubling” Yields and Manifestation of a Site Proximity Effect

This paper concerns the photoelectrochemical oxidation of formate and acetate ions on nanocrystalline composite (nanocomposite) films comprising of TiO 2 and nickel. The photocurrents arising from the oxidation of these organic compounds were compared with those measured in the base electrolyte (0.1 M NaNO 3 ), and a photocurrent enhancement factor, F, was thus determined. Values of F as high as ca. 5.5 were obtained for formate under certain conditions. The influence of film deposition time and TiO 2 dose on F is described. The variation of F with these film preparation variables and the unusually high values of F for these nanocomposite films are rationalized on the basis of a site proximity effect that arises from the synergistic presence of both nickel as a substrate adsorption site and adjoining TiO 2 serving as the photocatalyst.