Preparation And Photocatalytic Performance Of WO₃/tiO₂ Hollow Microspheres

Semiconductor photocatalyst has become a hot topic of environmental pollution control because of its depth of reaction at room temperature and can be directly drived by solar light. Among various semiconductor photocatalyst materials, TiO₂ was considered as one of best catalyst duo to its strong oxidizing power, stable chemical properties, nontoxicity and low cost. Despite its great potential, the low photocatalytic efficiency of TiO₂ limits application because of absorption ultraviolet light only?5% energy of the solar light? and the high recombination ratio of photon-generated carriers. In this paper, based on carbon spheres templates, TiO₂ hollow microspheres were prepared by template method and solvothermal method. In order to improve the photocatalytic activity of TiO₂ hollow microspheres, WO₃/TiO₂ hollow microspheres were prepare by using ammonium tungstate as tungsten source. The results showed that visible absorption ability and photocatalytic activity of WO₃/TiO₂ composite structure had significantly enhanced. The main content is listed as follows:?1? The carbon spheres template was synthesized from glucose by hydrothermal method. The influences of precursor solution concentration and hydrothermal time on carbon spheres morphology were studied. By comparing the FESEM images and particle size distributions of different carbon spheres, the optimal conditions for these samples was obtained using 0.5 mol/L glucose solution as precursor at 180?for 8 h. In this condition,the prepared carbon spheres with 330 nm average particle size have more smooth surface, better spherical structure, relatively concentrated particle size distribution and more appropriate production. It's suitable to choose the condition as follow-up experiments template preparation condition.?2? Using the carbon spheres as the template, tetrabutyl orthotitanate?TBOT? as Ti source, TiO₂ hollow microspheres with 330 nm average particle size were prepared by combining template synthesis and solvothermal synthesis. The UV-vis diffuse reflectance spectra illustrated the band gap of 3.0 eV. The photocatalytic activity of TiO₂ hollow microspheres was investigated by degradation methylene blue?MB? under simulated solar irradiation. The results demonstrated that after 120 min irradiation, the degradation rate of MB was 31.1% and the apparent rate constant of TiO₂ hollow microspheres was 0.31×10-2 min-1.?3? WO₃/TiO₂ hollow microspheres were successfully prepared by using carbon spheres as the template, tetrabutyl orthotitanate?TBOT? as Ti source and ammonium tungstate as tungsten source. The FESEM image and particle size distribution showed average particle size of the composite hollow microspheres was 310 nm. The UV-vis diffuse reflectance spectra illustrated the main absorption of the WO₃/TiO₂ hollow microspheres were red-shifted about 31 nm compare with TiO₂ hollow microspheres, indicating that composite structure had stronger light absorption ability and absorption range had expanded to the visible light region. Different WO₃ amount of the WO₃/TiO₂ hollow microspheres resulted in different degradation rate of MB solution. With the increase of the amount of ammonium tungstate, dye adsorption of complex system was also gradually improved. When the amount of ammonium tungstate was 0.12 g, the MB adsorption rate of complex system reached 73.9%. When the amount of ammonium tungstate was 0.06 g, the photodegradation efficiency of the complex system reached the maximum value. After 120 min simulated solar light irradiation, the photodegradation rate of the WO₃/TiO₂ hollow microspheres system reached 78.6%, the apparent rate constant was 1.25×10-2 min-1, which was about 4 times as that of TiO₂ hollow microspheres.