Synthesis of excellent visible-light responsive TiO₂ - _XN_y photocatalyst by a homogeneous precipitation- solvothermal process

Anatase, brookite and rutile type nitrogen-doped titania nanocrystals (TiO₂ - _xN_y) which are beige in color were successfully prepared by a 'Homogeneous Precipitation-Solvothermal Process' (HPSP) in TiCl₃-hexamethylenetetramine (C₆H ₁₂N₄) aqueous and alcohol solutions. The phase composition, crystallinity, microstructure, specific surface area, nitrogen doping amount and photocatalytic activity of titania powders greatly changed depending on pH, temperature and the type of treatment alcohols. The TiO ₂ - _xN_y powders showed excellent visible-light absorption and photocatalytic activity for nitrogen monoxide destruction under irradiation by both visible-light and UV-light. The beige titania powders prepared in TiCl₃-hexamethylenetetramine alcohol solutions at 190 °C for 2 h possessed higher specific surface areas than those in aqueous solution. About 39 and 83% nitrogen monoxide could be continuously removed by the anatase TiO₂ - _xN_y photocatalyst under irradiation of visible-light (λ > 510 nm) and UV-light (λ > 290 nm), respectively.