Photoelectrochemical study of sputtered nitrogen-doped titanium dioxide thin films in aqueous electrolyte

This paper describes the photoelectrochemical response in aqueous electrolyte for nitrogen-doped titanium dioxide, TiO2−xNx. The electrodes were prepared by reactive DC magnetron sputtering in an environment of argon, oxygen and nitrogen. The crystal structure of the photoelectrochemically active films was mainly of rutile character and scanning and transmission electron microscopy revealed a highly porous parallel penniform microstructure. The nitrogen-doped TiO2 generated a monochromatic incident photon-to-current efficiency response in good agreement with the optical spectrum. The onset wavelength for photoresponse was located around 550 nm. The visible light response for TiO2−xNx compared to TiO2 prepared without nitrogen was considerably improved at moderate bias. However, severe recombinations were observed in the nitrogen-doped material indicating that the doping sites could serve as recombination centres.