Anatase TiO2 films with 2.2 eV band gap prepared by micro-arc oxidation

Anatase TiO2 films were prepared by micro-arc oxidation of TiN films in a Na3PO4 electrolytic solution, while TiN films were obtained by ion beam assisted deposition on Ti substrates. The crystal structure, surface morphology and optical property of the films were investigated by X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), scanning electron microscopy (SEM) and UV–vis spectroscopy, respectively. The photocatalytic activity of the films was evaluated by the decomposition of methylene blue. Mechanisms for micro-arc oxidation and band gap narrowing of N-doped TiO2 were discussed.