N-doped SiO2/TiO2 mesoporous nanoparticles with enhanced photocatalytic activity under visible-light irradiation.

Mesoporous nanocrystalline N-doped SiO2/TiO2 visible-light photocatalysts were prepared by treating SiO2/TiO2 xerogels in a flow of nitrogen gas bubbled through concentrated ammonia solution. Structural characterization and performance analysis results revealed that the addition of SiO2 remarkably altered the phase composition, specific surface area, microstructure, as well as the photocatalytic activity of N-doped TiO2. The presence of SiO2 in N-doped TiO2 particles suppressed the formation of rutile phase and the crystal growth of N-doped TiO2 particles during thermal calcinations. When weight ratio of SiO2/TiO2 was in 0.05-0.20, the N-doped SiO2/TiO2 exhibited higher photocatalytic activity than the N-doped TiO2, and optimum ratio was found to be 0.05. The enhanced photocatalytic activity could be attributed to the higher specific area, larger pore volume, and more surface hydroxyl groups in the catalyst.