Synthesis and characterization of visible light responsive N–TiO2 mixed crystal by a modified hydrothermal process

N doped TiO2 with anatase and rutile mixed crystal were prepared by using tetrabutyl titanate as the precursor via a modified hydrothermal process and calcination at 320 °C. The microstructure and morphology of samples were characterized by XRD, UV–vis-DRS, FTIR and XPS. The results showed that N–TiO2 particles were crystallized to anatase and rutile mixed crystal structure; they were presented narrow particle size distribution, and the average particle size was ca. 13.5 nm calculated from XRD results. It was found that the N-doped TiO2 particles showed strong visible-light absorption and high photocatalytic activity for the mineralization of Rhodamine B under irradiation by visible light (400–500 nm). The high visible-light photocatalytic activity of the obtained N-doped TiO2 might result from the synergetic effect of nitrogen doping and the mixed lattice structure of N–TiO2. Possible mechanism of N–TiO2 mixed crystal formed under hydrothermal conditions was discussed.