Enhanced Photocatalytic Activity of Co Surface Doped Nanocrystalline TiO2-SiO2 Composite Films

Abstract

In order to enhance the photocatalytic activity of the TiO2 films, Co surface doped TiO2-SiO2 composite films were synthesized by the improved sol-gel method, in which tetrabutyl titanate (Ti(OC4H9)4) and tetraethyl orthosilicate were chosen as the precursors and cobaltous nitrate hexahydrate (Co(NO3)2·6H2O) was chosen as cobalt source. The field emission scanning electron microscopy and X-ray diffraction results indicated that the films were composed of nanoparticles or aggregates. The photoluminescence results revealed that the recombination rate of the photogenerated electrons and holes was prohibited via SiO2 composite and Co doping in TiO2 film. The Brunauer–Emmett–Teller results showed that the surface area of the modified TiO2 was 301.7 m2 g−1, while that of the pure TiO2 was 68.4 m2 g−1. The photocatalytic activities of the films were evaluated by degradation of an organic dye in aqueous solution. With the SiO2 composite and Co doping, the modified TiO2 films with high photocatalytic activity and clearly responsive to the visible light were obtained. The mechanisms of photoactivity enhancement for composite films have also been discussed.