Effect of WO3 additive on the mesostructure and optical properties of mesoporous TiO2

• Main Authors: Hao Yu Cheng, 鄭浩余
• Other Authors: Lay Gaik Teoh
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/74958210467344568560

碩士 === 國立屏東科技大學 === 機械工程系所 === 97 === Due to their large surface area, tunable pore size and suitable morphology in comparison with powder materials, mesostructured materials of transition metal oxides, especially of TiO2, are promising candidates for many applications. In this study, the mesoporous TiO2 has been prepared by using sol-gel process with TiCl4 as the inorganic precursor and block copolymer as the structure-directing agent. We adjusted the additive of WO3 to investigate its effect on structure and the properties of mesoporous TiO2.Various techniques were used for characterization of the samples, including TGA, XRD, TEM, N2 adsorption-desorption isotherms and UV-vis spectroscopy. Mesoporous TiO2 obtained are characterized with anatase structure after calcined at 250~400°C. For the sample using 1.5 g block copolymer as the structure-directing agent, the high specific surface area is 288.20 m2/g and the relatively narrow pore size distribution centered at 6.7 nm after it is calcined at 300 °C. The results show that the mesostructure of TiO2 can be controlled by the block copolymer. When the additive of WO3 increased from 0 to 3 mol %, the specific surface areas decreased from 288.20 to 201.86 m2/g, but the average pore sizes increased from 6.7 to 8.6 nm after being calcined at 300°C. However, the surface area of TiO2 substantially increase to 252.85 m2/g, and the pore size is drastically decrease to 6.7 nm as the WO3 content is increased to 5 mol %. Optical absorption in the UV region enhanced gradually with the increase of WO3 content, and (αhυ)1/2 varied linearly with hυ. The optical bandgap decreased in the region from 3.64 eV for pure TiO2 to 3.14 eV with 5 mol % WO3 and the relationship between optical bandgap and WO3 content (x) fitted to the equation: Eg(x) = Eg(0) + [Eg(1) - Eg(0) - b]x + bx2.