Effect of calcination on the visible light photocatalytic activity of N-doped TiO2 prepared by the sol-gel method.

Abstract

A series of N-doped TiO2 nanoparticle powders have been prepared by the sol-gel method using triethylamine as N precursor. The effect of calcination temperatures on the quality of the as-prepared samples was studied and an annealing treatment was introduced to improve further the quality of the as-prepared sample. The visible light photocatalytic activities of the samples were evaluated by decomposition of methyl orange (MO) in water. The calcination temperature plays a key role in determining the quality of N-doped TiO2 nanoparticle powders. The enhancement of calcination temperatures facilitates the crystallization of N-doped TiO2 powders and the elimination of surface organic residues, but promotes the loss of doping N and the agglomeration of nanoparticles and results in low N doping level and large particle sizes. The N-doped TiO2 sample (NT-300) calcined at 300 degrees C in air for 3 h produced the maximum visible light photocatalytic activity. The annealing treatment of NT-300 at its calcination temperature could improve the crystallinity, remove effectively the surface organic residues, keep nanoparticles in smaller size, and retain the doping N, therefore improving the visible light photocatalytic activity significantly.