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

Anatase, brookite and rutile type nitrogen-doped titania nanocrystals (TiO2-xNy) which are beige in color were successfully prepared by a 'Homogeneous Precipitation - Solvothermal Process' (HPSP) in TiCl3 - hexamethylenetetramine (C6H12N4) 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 TiO2-xNy 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 degreesC 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-xNy photocatalyst under irradiation of visible-light (lambda > 510 nm) and UV-light (lambda > 290 nm), respectively.