Characterization of metal (Ba, Al, Si, V, and W)-incorporated and toluene photodecomposition in the presence of H_2O

摘要

This study focused on toluene photodecomposition in the presence of H_2O over metal (Ba, Al, Si, V, and W)-incorporated TiO_2. The nanometer-sized, metal-TiO_2 photocatalyst samples, including Ba~(2+), A1~(3+), Si~(4+), V~(5+), and W~(6+) ions, were prepared by using the solvothermal method. The X-ray photoelectron spectroscopy (XPS) results showed that the Ti-OH peak, which indicates hydrophilicity, increased with increasing Al and Si ion components but decreased with increasing Ba, V, and W ion components. The contact angles were distributed over the range of 0-10° on almost all films (200-nm thick) after irradiation for 2 h, and in particular approached 0° on the Al-TiO_2 and Si-TiO_2 nanometer-sized films after just 30 min. The toluene (100 ppm) photodecomposition in the continuous system increased in the order of Al-TiO_2 > Si-TiO_2 > pure TiO_2 > W-TiO_2 > Ba-TiO_2 > V-TiO_2, and the maximum toluene conversion rate achieved was 45% over Al-TiO_2 film after 120 min. The toluene conversion remarkably increased; however, over all photocatalysts, with H_2O addition during the toluene photo-decomposed reaction, and in particular, the conversion reached up to 90% after 120 min over Al-TiO_2 and Si-TiO_2 with increased hydrophilicity. After photoreaction for 24 h, minimal carbon was deposited on the photocatalyst under both reaction conditions, with and without H_2O addition, although the deposited carbon amounts were smaller for the former. These results confirmed that the hydrophilicity of the photocatalyst had a greater effect on toluene decomposition, while the photocatalytic deactivation could be retarded by H_2O supplementation during toluene decomposition.