Effect of nitrogen doping on anatase–rutile phase transformation of TiO2

N–TiO2 nanoparticles were prepared by hydrolysis of TiCl4 and characterized by means of XPS, SEM, XRD, TG-DSC and UV–vis DRS. The nitrogen was doped into TiO2 lattice successfully, and the temperature of anatase phase transforming to rutile phase was found to be increased by N-doping. By comparison of the crystal structure of titanium nitride, anatase and rutile, the mechanism for the transformation temperature increase was summarized as the effects of the similar structure of titanium nitride and anatase, the crystal aberration and the retained crystal growth induced by N-doping. The visible light photocatalytic activity of N-doped TiO2 was much higher in comparison with that of P25. The higher photocatalytic efficiency could be attributed to the synergetic effect of N-doping and appropriate crystallinity of anatase phase TiO2.