Solvothermal-induced phase transition and visible photocatalytic activity of nitrogen-doped titania

Nitrogen-doped titania nanoparticles consisting of pure anatase, pure rutile and bicrystallites (anatase + rutile and anatase + brookite) have been prepared in TiCl3-HMT (hexamethylene tetramine)-alcohol solution under solvothermal process. The effect of the solvent type and amount of HMT as pH adjuster on the phase composition of titania and its visible photocatalytic activity for degradation to MO (methyl orange) was investigated. It is found that anatase gradually transferred to rutile with increase of carbon chain using methanol, ethanol, 1-propanol and 1-butanol as solvent. The pure anatase formed at the pH value of 1-2, while bicrystalline titania (anatase + rutile and anatase + brookite) at that of 7-10 in the presence of methanol. The bicrystalline (anatase + brookite) titania have the best visible photocatalytic activity among all the samples. The -(NO) and -(NH) dopants with an N (1s) binding energy of 400 eV may have positive effects on the visible light photocatalytic activity.