Preparation Of Mesoporous TiO₂ Composite Photocatalysts And Their Visible Light Induced Photocatalytic Activities

In recent years, a large amount of wastewater was produced with the development of agriculture and industry. The wastewater was discharged into river and became a potential threat to the survival and development for human beings. In 1972, TiO₂ electrode was first used to produce H2, since then, semiconductor photocatalytic technology has gradually developed and was applied in wastewater treatment. TiO₂ was one of the most common semiconductor photocatalyst, however, the large bandgap and high electron-hole recombination rate limited the photocatalytic activity of TiO₂. In this paper, the synergistic effect of large surface area of mesoporous carbon and noble metal depositing or metal cation doping was used to obtain mesoporous TiO₂ composite photocatalysts, which can effectively improve the visible light photocatalytic performance of TiO₂. The research work of this paper mainly contains the following aspects:1. RF@TiO₂ composite core-shell spheres（RF is getting from the polymerization reaction of resol and Pluronic F127） were prepared by changing the amount of tetrabutyl titanate（TBOT） with a mixed solvent method, and then calcined at 600℃ in nitrogen atmosphere to obtain mesoporous C@TiO₂（meso-C@TiO₂）. Finally, noble metal Ag was deposited on the surface of meso-C@TiO₂ to obtain meso-C@TiO₂@Ag. The composition, phase, morphology and structure of meso-C@TiO₂ and meso-C@TiO₂@Ag were investigated. The results showed that the meso-C@TiO₂@Ag composite photocatalyst was successfully synthesized and the BET surface area was up to 173.9 m2/g. Methylene blue as a degradation model was used to evaluate the photocatalytic activity of the obtained samples under visible light, and the effects of the amount of TBOT and Ag on photocatalytic activity of meso-C@TiO₂@Ag were discussed. The best amount of TBOT was 0.3 mL, and the degradation rate of methylene blue was 90% in 40 min. The best amount of Ag was 10 wt%, and the methylene blue can be degraded nearly 100% in 40 min, which was much better than the commercial P25.2. Mesoporous C/TiO₂ precursor was prepared by changing the amount of resol and titanium source by evaporation-induced self assembly（EISA） method, and then the precursor was calcined at different temperatures in nitrogen atmosphere to obtain mesoporous C/TiO₂ composite. Finally, noble metal Ag was deposited on mesoporous C/TiO₂ to obtain mesoporous C/TiO₂/Ag composite photocatalyst. The phase, composition, morphology and structure of mesoporous C/TiO₂/Ag were investigated. The results showed that the meso-C/TiO₂/Ag composite photocatalyst was successfully synthesized and the BET surface area was up to 149.1 m2/g. Methylene blue as a degradation model was used to evaluate the photocatalytic activity of the obtained samples under visible light, and the effects of the mass ratio of C/TiO₂, the calcination temperature and the amount of Ag on photocatalytic activity of mesoporous C/TiO₂/Ag composite photocatalyst were discussed. The best amount of resol was 4 g, titanium source was 3.2 g, the best calcination temperature was 650℃, the amount of AgNO3 added was 10 wt%, and the methylene blue can be 100% degraded within 20 min.3. Mesoporous C/TiO₂/Cu precursor was prepared by changing the mass ratio of titanium source and CuCl2 by EISA method, and then the precursor was calcined at different temperatures in nitrogen atmosphere to obtain mesoporous C/TiO₂/Cu. The phase, composition, morphology and structure of mesoporous C/TiO₂/Cu were investigated. The results showed that the mesoporous C/TiO₂/Cu composite photocatalyst was successfully synthesized and the BET surface area was up to 156.1 m2/g. Methylene blue as a degradation model was used to evaluate the photocatalytic activity of the obtained samples under visible light, and the effects of the Cu/Ti mass ratio, the calcination temperature on photocatalytic activity of mesoporous C/TiO₂/Cu photocatalyst were discussed. The best mass ratio of titanium source to CuCl2 was 5:5, the best calcination temperature was 550℃, and methylene blue was degraded within 20 min.