Photoelectrochemical Study of Nitrogen-Doped Titanium Dioxide for Water Oxidation

This paper describes the photoelectrochemical response in aqueous electrolyte of nitrogen-doped titanium dioxide, TiO2-xNx. Thin film electrodes were prepared by reactive DC magnetron sputtering in an environment of Ar, O2, and N2. A typical film thickness was 0.85 μm. The crystal structure of the photoelectrochemically active films was mainly of rutile character, and scanning and transmission electron microscopy showed a highly porous parallel penniform nanostructure. It was conclusively shown that dioxygen could be generated from water by illumination of the TiO2-xNx electrodes at moderate anodic potentials. The current density under 1000 W m-2 visible light from a sulfur lamp was 0.2 mA cm-2 at 0.55 V vs Ag/AgCl. Current−voltage characteristics under illumination were strongly dependent on the scan direction. Scanning the electrode from cathodic toward anodic potentials gave an onset potential similar to that of normal rutile TiO2, whereas a reversed scan gave an onset of photocurrent (depending on the...