| The major work in this dissertation is focused on the study of the relationships between the structures and the catalytical properties of the catalysts in the heterogeneous catalysis, especially in photocatalysis, which is one of the hot research fields these years. Semiconductor material TiO2 is low-cost, non-toxic, chemically stable, and it can photodegrade the organic pollutants completely. So it has been widely used in photocatalysis. In this dissertation, We have prepared the TiO2 photocatalyst with certain functions by different methods, and it has been utilized in adsorption, acid-catalysis and photocatalysis. We have investigated the adsorption, catalytical properties of these TiO2 photocatalysts, and the relationships between the structures and the properties of these catalysts.1. The preparation of CeO2-TiO2 transition metal composite oxides with different Ce contents via sol-gel-method. We investigated the interfacial/surface structures of the composites, and the adsorption ability toward methyl orange based on the unique structure. Based on the results of XRD, UV-Raman and Visible-Raman, XPS, XAFS, we found that:Ce do not enter the TiO2 lattice, Ce first nucleated at the defects in the bulk of TiO2, as the Ce content increased, it formed the CeO2 fluorite structure. On the interface, Ce-O-Ti bond formed, a few amount of Ce can stabilize the local structure and anatase phase of TiO2. In CeO2-TiO2 composite oxides, TiO2 is rich in surface, and CeO2 is distributed in inner layer. It was concluded not only from these characterization techniques above, but also from the selective chemisorption toward methyl orange by the composite oxides. Based on the distinguished differences of the adsorption ability toward methyl orange between CeO2 and TiO2, we developed a facile method to identify the surface composition of the CeO2-TiO2 composite oxides, and we have broaden the application to other composite oxides, like CeO2-Fe2O3, CeO2-ZrO2 et al. We hope that the surface composition of complex composite oxides can easily identified by this method.2. The preparation of CeO2-TiO2 transition metal composite oxides with different Ce via co-precipitation method. We have investigated the bulk, surface and interface structures of the composite oxides by XRD, XAFS et al. the solid solution could formed, like the Ce/Ti ratio 3:7, Ce0.3Ti0.7O2 is a monoclinic solid solution. As the Ce content increased, because of the formation of the solid solution, the structure evolution of the composite oxides is more complicated. The results of H2-TPR and CO-TPR show that the redox properties of solid solution are different with other composite oxides based on the unique structure. The oxygen storage ability of composite oxides and solid solution is better than CeO2. We found water-gas reaction in CO-TPR, it is related to the concentration of the hydroxyl groups on the surface of the composite oxides. The adsorption ability toward methyl orange by the composite oxides become stronger as the increasing of the Ce content. CeO2 is the main component that adsorbed methyl orange, thus the evolution of the surface components is the main point that effect the adsorption properties of the composite oxides.The photocatalytic activity of the CeO2-TiO2 composite oxides for the photodegradation of methyl orange is low. It could be the preparation method, the type of the photocatalytic reaction, or the efficiency of the experiment's equipment that needed the further study.3. The N-doped TiO2 photocatalysts have been prepared by clacination of the precusors at different temperature, which was synthesized via the precipitation of [TiO(C2O4)2]2-by ammonium hydroxide at low temperature. The results shows that all the photocatalysts are anatase phase, N is doped at the interstitial sites in TiO2 lattice, and because of this N doping, the light response of these photocatalysts is moved into the visible light region. Based on the TPRS results, we found that the photocatalyst calcined at 400℃is covalently bonded with oxalate groups on the surface to form Bronsted acid sites. All photocatalysts are performed well in the photocatalytic reaction for the degradation of methyl orange. The photocatalyst calcined at 400℃could adsorb methyl orange effectively because of the acidity, and it is an acid-catalysis and photocatalysis bi-funcitional catalyst.4. We developed an one-step method to prepare N,S co-doped TiO2 photocatalyst via the controlled thermal decomposition of ammonium titanyl sulfate. the photocatalyst calcined at 800 C is still anatase, shows the phase stabilization ability. The results of XPS show that the photocatalysts are all S(IV) cation doping, the photocatalyst calcined at 600℃is co-doped with N,S and N is at the interstitial sites in TiO2 lattices. The band gap of TiO2 is not narrowed down by these doping. Based on the results of NH3-TPD and 1H soild-state MAS NMR, the photocatalyst calcined at 600 C is covalently bonded with the sulfate acid groups on the surface to form Bronsted acid sites. The evaluation of the photocatalytic activity is conducted by the photodegradation of methyl orange and photolysis of water for H2 production. Under all-wavelength light illumination, the photocatalytic activity of the photodegradation of methyl orange is well for all the photocatalysts, the photocatalyst calcined at 600℃is most active, better than the commercial P25. All the photocatalysts could degrade methyl orange under visible light illumination because of the N, S doping. After Pt loading, the H2 production under all-wavelength light illumination by the photocatalysts increased dramatically compared with the bare TiO2. Because of the synergy effect of Pt loading and the N, S co-doping, the 0.1Pt/TiO2 shows an improved photocatalytic activity for H2 production. the photocatalyst calcined at 600℃is both very active in the esterification for the ethyl acetate production and the photocatalytic reactions. So it is a acid-catalysis and photocatalysis bi-functional catalyst.
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