Visible light response of nitrogen and sulfur co-doped TiO2 photocatalysts fabricated by anodic oxidation

N,S-codoped TiO2 photocatalysts were successfully immobilized on the surface of plasma-nitrided pure Ti substrate by anodic oxidation in a sulfuric acid electrolyte and their photocatalytic activities were evaluated. The anodic TiO2 photocatalysts effectively bleached methylene blue (MB) aqueous solution under visible light illumination. X-ray photoelectron spectroscopy (XPS) analysis clarified the presence of nitrogen and sulfur, and auger electron spectroscopy (AES) analysis revealed that sulfur was distributed over the anodic oxide. It is estimated that N,S-codoping in the anodic TiO2 narrows the band gap of pristine TiO2 and improves the photocatalytic activity under visible light illumination.