Indium doped TiO2 nanotubes were fabricated by a two-step pre-doping method. It was found that the TiO2 nanotubes with indium doped content at 3% exhibited the best photocatalytic activity being over twice as much as that of pure TiO2 nanotubes on the photocatalytic degradation of 4-chlorophenol under visible light. Based on XRD, XPS and SPS, it can be inferred that when the doped content is low, the indium ion substitutes Ti into the TiO2 lattice forming the InxTi1－xO2 structure and the In doped energy-band narrows the band gap by mixing with Ti 3d states. With increasing the doped content, In2O3 comes up on the surface of InxTi1－xO2 nanotubes to form the InxTi1－xO2/In2O3 composite structure. This composite structure efficiently enhances the visible light response, promotes photogenerated carriers separation and increases the utilization of photogenerated carriers in photocatalytic reactions at the solid/liquid interface, resulting in the higher photocatalytic activity under visible light.

Key words: In doping, TiO2 nanotube, photocatalytic activity under visible light