| Volatile organic compounds (VOCs) are attracting wide attention because of their photochemical smog and greenhouse effect, and moreover benzene series of VOCs would bring carcinogenicity, mutagenicity and teratogenicity to human health. Thus, the development of effective controllable methods is urgently required. Among all of the methods, photocatalysis is considered to be one of the most effective ways in the process. However, the degradation rates for VOCs are still in a low level as the utilization rate of visible light is limited in the solar spectrum. To address the problem, the visible-light responsive and high-efficiency photocatalysts have been fabricated by some different methods in the thesis. Meanwhile, toluene and orthzo-Dichlorobenzene (o-DCB), as the two most typical VOCs, were chosen as research objects, and then the mechanisms of catalytic reaction had been investigated by in situ FTIR and Density Functional Theory (DFT), which could be beneficial to design more effective catalysts. The research results are as follows:(1) Based on modulation of the electronic structure, the Ti1-xZrxO2 composites were fabricated by a facile and co-participation method and the average particle size dispersed without aggregation was about 300 nm. The materials incorporated Zr element showed decreasing crystallinity with increasing Zr contents. The adsorption edge of the Ti0.3Zr0.7O2 extended to the visible region and the band-gap energy was around 2.92 eV. Furthermore, the weak fluorescence signals indicated that the recombination of photo-generated carriers was inhibited greatly, which would be beneficial for enhancing the photocatalytic efficiency. Hence, the removal efficiency of the Ti0.3Zr0.7O2 particles could reach 81.8% after 6 h. In addition, the intermediates (benzaldehyde) and final product (CO2) were also identified through degradation process of gaseous toluene.(2) Based on modulation of the crystal structure, a series of AgInS2/TiO2 composites was fabricated by a one-pot hydrothermal method, and the particles were composed of multi-phase heterostructures of AgInS2 and TiO2. The optical properties showed that the synthesized nanoparticles exhibited strong absorption intensity in the region of visible light and the catalyst (1:5) possessed the most effective separation of photo-generated charges. So the degradation ratio of gaseous o-DCB could reach 48.9% after 7 h. Moreover, the mechanism of enhanced photocatalytic activity was proposed in terms of the quantum calculation and proper band alignment of AgInS2/TiO2 composites.(3) Based on modulation of the microscopic structure, the urchin-type V2O5 hollow microspheres with an average particle size of about 700 nm were fabricated by the solvothermal method, and then a probable formation mechanism of hollow structure was illustrated based on the carbonaceous templates. Moreover, the specific surface area of hollow V2O5 was found to be 65.5 m2/g. The photocatalyst was an indirect band-gap semiconductor and showed much significance to the visible-light response. So the degradation ratio could reach about 45.7% after 7 h of reaction time, which was 11.4% and 28.1% as high as that over V2O5 solid spheres and commercial V2O5, respectively. Finally, a possible degradation mechanism could be proposed by in situ FTIR:-OH radical species attacked the ortho-position of the aromatic ring of o-DCB, and then Cl atoms were substituted for the nucleophilic effect, leading to the generation of the o-benzoquinone-type species and breakdown of the rings. As the reaction progressed, these intermediates would produce some inorganic acids and inorganic molecular compounds, such as CO2, H2O, and HCl.(4) Based on modulation of the microscopic structure, the double-shelled ZnFe2O4 hollow microspheres with an average particle size of about 600 nm were fabricated by a simple solvothermal method and then a probable formation mechanism was illustrated based on different calcination ramp. When the rate was 20 ?/min and the final annealing temperature was 350 ?, the double-shelled ZnFe2O4 hollow microspheres were formed by two opposite forces of contraction from oxidative decomposition of the organic species and adhesion from the dense shell. The materials obtained could be indexed to the spinel. At last, the degradation ratio of gaseous o-DCB was about 73.9% after 7 h, ascribed to high surface area (126.7 m2/g) and effective light absorption (multiple scattering for double-shelled architectures). |
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