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 TiO2 and nickel. The photocurrents arising from the oxidation of these organic compounds were compared with those measured in the base electrolyte (0.1 M NaNO3), 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 TiO2 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 TiO2 serving as the photocatalyst.