Preparation Of The V₂O₅/BiVO₄/TiO₂Nanocomposites And Photocatalytic Degradation Of Gaseous Toluene Under Visible Light Irradiation

Recently, volatile organic pollutants (VOCs) which are extremely hazardous to the environment and human health have attracted wide attention. How to economically and efficiently remove VOCs from ambient environmentcan has become a hot topic. Compared with the traditional treatment techniques, environment-friendly photocatalytic oxidation method is considered to be one of the most promising processing technology. TiO2is the most extensively studied photocatalyst due to its non-toxic, high chemical stability, low price and strong oxidizing ability etc., However, the wide band gap of TiO2(3.2eV for anatase,3.0eV for rutile) causes its inactivity under visible light, which occupies the major part of solar light. Besides, another shortcoming hindering its practical application is its high recombination rate of the photo-induced charges. Therefore, how to use modification methods to increase the hole-electron separation efficiency and extend the absorptive spectral range of TiO2is an important scientific issue. In this paper, we use the method of combining with narrow band gap semiconductors to enhance visible light photocatalytic activity of TiO2. The main investigation was carried out as follows:(1) The TiO2nanobelts and V2O5/BiVO4nanorods were prepared via a facile solvothermal/hydrothermal method, and then a novel composite V2OCVBiVO2/TiO2photocatalyst was successfully synthesized by a simple adhering method. The structural and optical properties of the as prepared samples were comparatively characterized. The characterization results of scanning electron microscopy and high-resolution transmission electron microscopy showed that the formed ternary nanojunctions are comprised of TiO2nanobelts and V2O5/BiVO4nanorods, which are self-assembled by numerous smaller V2O5and BiVO4nanoparticles. By the analyses of UV-vis diffuse reflectance spectroscopy and photoluminescence spectroscopy, it was suggested that the loading of V2O5/BiVO4significantly enhances the visible light absorption of TiO2and promote photoinduced charge separation.(2) We studied the photocatalytic activities of the as-prepared photocatalysts for decomposition of gaseous toluene under visible light irradiation (X>400nm). Compared to pure TiO2nanobelts and V2O5/BiVO4nanorods, the V2O5/BiVO4/TiO2composite exhibited higher photocatalytic activity, which could be attributed to the ternary heterojunction structure of V2O5/BiVO4/TiO2nanocomposite that not only extend the absorptive spectral range of TiO2but also enhanced the photo-generated electron-hole separation. Besides, we used in situ infrared spectra to monitor transient events occurring on the catalyst during the foreign species adsorption and their reactions on the surface, and the result showed that a part of toluene was decomposed into byproducts such as benzoic acid and benzaldehyde etc., and anothor part was completely mineralized to CO2and H2O. Electron spin resonance examination confirmed that the photo-induced active species (·OH and O2·-) were involved in the photocatalytic degradation of toluene.