| HC(hydrocarbon) is one of the main components of the motor vehicle exhaust emissions. Photocatalytic technology brings a new way to organic pollutants treatment, related research has shown that nearly all the environmental organic pollutant can be degraded in some extent. As a photocatalyst, TiO2 was widely used to degrade a variety of organic pollutant. However, pure TiO2 itself usually cannot meet practical needs for its low utilization of sunlight and high recombination rate of photogenerated carriers. In this work, we successfully improved the photocatalytic activity of TiO2 through forming heterojunction with loading narrow band gap semiconductor onto the surface of TiO2 particles. It consists of material selection, preparation, characterization and theoretical analysis of the result in the experiments.. The main contents are summarized as follows:In chapter one, first we introduced the present situation of automobile exhaust pollution, the application and the mechanism of semiconductor photocatalysis. Then we summarized the main issues in study of photocatalytic materials and the progress of highly active photocatalysts including some path for improving the efficiency of photocatalysts by means of SPR enhancement of metallic nanoparticles, construction of internal electrical field, and transfer of carriers between different coordination polyhedrons, and modulation of band structures by quantum sized effect.In chapter two, a detailed introduction of catalyst characterization was carried out.In chapter three, Cu2O/TiO2 heterostructures with different Cu2 O concentrations were prepared by a chemical precipitation method, take the Cu(CH3COO)2·H2O and TiO2(P25) as the precursor. The ratio of Cu2O/TiO2 in the nanocomposites can be tuned by controlling the concentration of Cu(CH3COO)2·H2O. It is revealed that the optical response and photocatalytic performance of the Cu2O/TiO2 nanocomposites can be tuned by adjusting the molar ratio of Cu2O/TiO2. The samples were investigated by XRD, HRTEM, UV-vis diffuse reflection absorption spectra. Through loading of Cu2 O, heterostructures are formed between Cu2 O and TiO2, which favors the efficient separation of charge carrier. We focus our studies on photo-catalytic activities of ethylene and propane photodecompositions. Compared with the pure p25, the 0.1wt% Cu2O/TiO2 heterostructure shows remarkable improved photocatalytic activity in degrading ethylene and propane.In chapter four, WO3/TiO2 nanocomposites were prepared by a modified impregnation method using ammonium tungstate and Dugussa P25 as the precursor. The as-obtained tungsten oxide is homogeneous distributed on the surface of TiO2 and thus a sufficient interfacial contact is achieved for these two components. Using photocatalytic degradation of hydrocarbons(C2H6, C3H8, C2H4) as model reactions, it is demonstrated that the WO3 decoration can obviously improve the performance of the TiO2(P25) under simulated solar light irradiaton. Among the WO3/TiO2 nanocomposites, the 10wt%WO3/TiO2 shows the best photoactivities, which can effectively remove the C2H6, C3H8, C2H4 within 15 minutes, 9 minutes and 8 minutes, respectively. In addition, the photocatalytic activities of the samples are also investigated under UV light irradiation and visible light irradiation. The results also show a strong benefical effect of WO3 decoration for the photocatalytic activities of TiO2 both in UV and visible region. The enhancement of the photocatalytic performance is ascribed to the effective charge separation due to WO3/TiO2 coupling. The photocatalytic mechanism is also investigated by in-situ FTIR analysis.In chapter five, we summarized the research work and discussed the problems of this work. Finally, we proposed the research plans in the future work. |
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