SiO_2@TiO_2核壳微球和TiO_2中空微球的制备及其光催化性能

Preparation and Photocatalytic Properties of SiO_2@TiO_2 Core-Shell and TiO_2 Hollow Microspheres

以Stber法制备的单分散SiO_2微球为模板,率先采用静电吸附法和相吸附法相结合技术制备出SiO_2@TiO_2核壳结构微球。深入研究了pH值及煅烧温度对其结构和性能的影响。对SiO_2@TiO_2微球进行去核处理,得到TiO_2中空微球。通过降解常见工业污染物硝基苯来研究两种微球的光催化活性。采用XRD、SEM、TEM、BET、FT-IR对样品进行表征,用紫外-可见分光光度计测量硝基苯溶液降解前后的吸光度。结果表明,相同条件制备的TiO_2中空微球的比表面积比SiO_2@TiO_2微球的显著增大,最大为87m^2/g,导致TiO_2中空微球的光催化活性比SiO_2@TiO_2微球明显提高,对硝基苯的4h降解率可达95.2%。低于600℃处理得到的TiO_2壳层为锐钛矿相,呈孤岛状模式生长。温度升高到700℃时出现金红石相。在pH=9.0、600℃热处理3h条件下制备的SiO_2@TiO_2微球经去核处理所得到的TiO_2中空微球的壳层厚度最大,为25.4nm,且空心球的Ti-O-Si键随之消失。

SiO2 @TiO2 core-shell particles were prepared by using a combination method of electrostatic adsorption and phase adsorption for the first time. The effects of pH value and calcination temperature on the synthesis were discussed. Monodispersed SiO2 microspheres synthesized by using Stober method were used as templates to coat the TiO2 shells. Then, TiO2 hollow microspheres were obtained by removing the SiO2 cores. The photocatalytic activities of the core-shell particles and hollow microspheres were compared by degrading the nitrobenzene, a kind of common industrial pollutant. The samples were characterized by XRD, SEM, TEM, BET and FT-ItL The absorbance of nitrobenzene solution was measured by UV-visible spectrophotometer before and after degradation. Results show that, under the same synthesizing condition, the specific surface area of TiO2 hollow microspheres is much bigger than that of SiO2 @TiO2 microspheres. The maximum specific surface area of the TiO2 hollow microspheres reaches 87 m^2/g, leading to a higher photocatalytic activity than that of the SiO2 @TiO2 mierospheres. The 4 h degradation rate of nitrobenzene is 95.2%. When the annealing temperature was lower than 600 ℃, the anatase phase TiO2 shell grew in island mode. Once the annealing temperature raised to 700 ℃, rutile phase TiO2 appeared. The TiO2 hollow micro- spheres obtained from the SiO2 @TiO2 microspheres prepared with pH= 9.0 and annealing at 600 ℃ for 3 h has the maximum shell thickness, 25.4 nm, and meanwhile, Ti-O-Si bond disappeared.