Low temperature hydrothermal synthesis of N-doped TiO₂ photocatalyst with high visible-light activity

A visible-light-active TiO₂ photocatalyst was prepared through nitrogen doping, employing triethylamine as nitrogen source, by a low temperature hydrothermal method without further calcinations. The prepared samples were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, diffuse reflectance spectra. A shift of the absorption edge to a lower energy and a stronger absorption in the visible-light region were observed in the N-TiO₂ samples. Comparing to P25 and undoped TiO₂, greatly improved photocatalytic activity, decomposing methyl orange dye solutions under visible-light irradiation, was obtained as a result of the doping of nitrogen into the titania system, that was evidenced by the formation of O-Ti-N bonds. In addition, the photocatalytic activity of N-TiO₂ was strongly affected by the hydrothermal temperature and pH value in the process of preparing the samples.