Preparation of homogeneous nitrogen-doped mesoporous TiO2 spheres with enhanced visible-light photocatalysis.

A series of mesoporous TiO 2 spheres of nanosized crystals with high monodispersity and dimensional homogeneity are synthesized by a simple reflux method. In order to improve the visible light response and to further narrow the band bap of TiO 2 sphere, nitrogen is used as the dopant in a hydrothermal method. Different from the traditional nitrogen doping in TiO 2 solid sphere, the nitrogen is uniformly distributed from bulk to the surface of mesoporous TiO 2 sphere, which is beneficial to the generation of the successive energy bands inside the TiO 2 band gap. Interestingly, the XPS results indicate that the nitrogen doping concentration could reach 1.31% (only 0.17% for nitrogen doped solid TiO 2 sphere), owing to the homogeneous doping in the mesoporous TiO 2 spheres. The nitrogen doped TiO 2 spheres exhibit such excellent characteristics as high specific area, relatively small particle size, pure anatase phase and excellent UV–vis absorption capacity in the range of 400–800 nm, which are all beneficial to the photo-degradation of Rhodamine B under the visible light irradiation. The high photocatalytic activity could be ascribed to the homogeneous nitrogen doping on the deep adjustment of energy band of TiO 2 sphere from the bulk to the surface. [ABSTRACT FROM AUTHOR]