Abstract: Highly crystalline nitrogen doped mesoporous TiO₂ photocatalysts were fabricated by the sol-gel method using tetrabutyl titanate as the Ti source, urea as the N source, and polyacrylamide (PAM) and polyethylene glycol (PEG) as the templates, and then by calcining in nitrogen and air. The photocatalysts were characterized by X-ray diffraction, transmission electron microscopy, N₂ adsorption, X-ray photoelectron spectroscopy, and UV-Vis spectroscopy. When the mass ratio of PAM and PEG was 1:4, the sample prepared by calcining at 600 °C in nitrogen and 500 °C in air had the anatase phase and a mesoporous structure and high crystallinity. The average pore size, crystallite size, and specific surface area were 5.11 nm, 12.5 nm, and 110.8 m²/g, respectively. Nitrogen atoms were incorporated into the TiO₂ lattice mainly as substitutional N and molecularly chemisorbed γ-N₂, and a small amount of interstitial N. Nitrogen doping narrowed the band gap and allowed light absorption in the visible light region. Compared with undoped mesoporous TiO₂, the absorption band edge of nitrogen doped samples exhibited a red shift and the light absorption intensity was increased. Photocatalytic degradation of methyl orange showed that the nitrogen doped mesoporous TiO₂ had a higher photocatalytic activity than undoped mesoporous TiO₂ under visible light.

Key words: mesoporous titanium dioxide, nitrogen doped, high crystallinity, photocatalytic activity, methyl orange