Synthesis and Characterization of Visible-Light Active Nitrogen-Doped TiO2 Photocatalyst

Abstract

Nitrogen-doped titania (N-doped TiO₂) has been synthesized through the hydrolysis of Nsubstituted titanium isopropoxide precursors followed by annealing treatment in air at desired temperatures. The resulting N-doped TiO₂ were characterized using TGA, XRD, BET, XPS, TEM and UV-VIS spectrophotometer. The XRD result showed that the structure of N-doped TiO₂ was anatase. The crystallite size of N-doped TiO₂ increased with the increase of N/Ti proportion. The pore properties were investigated from nitrogen gas sorption analyzer, showing a mesoporous structure of its N-doped TiO₂ with a high specific surface area and a sharp pore radius distribution. The substitution of oxygen sites with nitrogen atoms in the TiO₂ structure was confirmed by X-ray photoemission spectroscopy (XPS). The doping of nitrogen could extend the absorption edge into the visible-light region leaded to a clear decrease in the band gap on N-doped TiO₂ (compared to pure titania and Degussa P25). The adsorption capacity and adsorption equilibrium constant were also improved by the doping of nitrogen. Catalytic application on methylene blue photodegradation under visible-light irradiation indicated that N-doped TiO2 provide better activity comparing to the pure ones.