Morphology. Preparation Of Alcohol Heat Controllability Of Tio <sub> 2 </ Sub> Catalyst And Its Photocatalytic Properties

Semiconductor photocatalysis is a comprehensive discipline which combines optics, electrochemistry, material science, surface chemistry and catalysis chemistry. The semiconductor materials can absorb the optical energy and produce the photo-induced holes and electrons which have strong oxidizability and reducing power as well, thus the direct and indirect oxidation and reducing reaction can be occurred at the surface of the catalyst. What causes the great interest of the semiconductor photocatalysis in the scientific research area is the potential value to the problem of the energy utility and environmental purification. The semiconductor photocatalysis research has been developed for 30 years and a lot of achievements have been made but there remain many key problems waited to be solved. Efficient semiconductor photocatalyst need to be improved on the basis of fundamental research. The TiO₂, an n-type oxide semiconductor, has been proven to be the most suitable for widespread environmental applications among various photocatalysts, owing to its cheapness, nontoxicity, and structural stability. However, the broad band gap and low quantum efficiency confine the development of TiO₂ photocatalysts. Recently, it has been shown that TiO₂ architecture and morphology plays a key role in determining catalytic efficiency owing to the remarkable influence on the diffusion and adsorption of reactant molecules as well as the absorbance for lights. Our group have engaged in the photocatalyst research areas for many times and thus got much experience in the research of the interaction of the photocatalyst's structure and their activities. Our works focus on the synthesis of photocatalysts with various morphologies and structures through optimizing the preparation methods and conditions. The effect of crystal phase, texture and surface property to activity was explored in detail. Thus it could provide a lot of experience to further develop practical applications of photocatalysis technique. The detailed works are as follows:1. Fabrication and photocatalytic activity of TiO₂ particles with tailored structuresThe nano-structured TiO₂ materials with various morphologies containing sheets, core-shell structured spheres, solid spheres and semi-hollow structured spheres, have been obtained by a facile solvothermal approach based on the adjustment of solvents. The results demonstrate that the properties of solvents play a key role in determining the final structure. The relationship between morphology and photocatalytic activity has been demonstrated, which shows that semi-hollow structured TiO₂ is superior to other TiO₂ samples owing to the high special surface areas and its chamber structure.2. Synthesis of flower-like TiO₂ and its modification by Bi₂O₃ nanoparticles used in visible light photocatalysisThe hierarchical flower-like TiO₂ (FLT) has been achieved by using a simple solvothermal process without any surfactants or colloidal crystals as a template. It is shown that the petals interconnect each other and self-organize into quasi-spherical assemblies, or a flower-like morphology, with a puffy appearance. Such hierarchical flower-like structure significantly enhances the photocatalytic activity, because that its open structure with numerous of interconnected petals and exposed edges might be benefit for the light absorption just like solar panel to enhance the utilization efficiency of UV light, and thus significantly improve the photocatalytic activity.Meanwhile, the Bi₂O₃ modified titania (Bi-FLT) is prepared to improve the photocatalytic activity under visible light irradiation. During the photodegradation of 4-chlorophenol (4-CP) under visible light irradiation, the Bi-FLT sample exhibits higher activity than either the pure TiO₂ sample or commercial P25, owing to the modification of highly dispersed Bi₂O₃ on the surface of TiO₂. The highest photocatalytic activity of 75 % is obtained when the Bi/Ti molar ratio is 3.3 %. And the correlation of the photocatalytic performance to the structural characteristics is also discussed based on detailed characterizations. Meanwhile, such unique hierarchical flower-like structure may allow multi-reflections of light among the interconnected petals to and thus greatly enhance photocatalytic activity.3. Solvothermal synthesis and photocatalytic activity of anatase TiO₂ single-crystal nanosheets with exposed (001) high-energy facetsAnatase TiO₂ single-crystal nanosheets with exposed (001) high-energy facets have been successfully prepared via solvothermal route. The products are characterized in detail by field emission scanning electronic microscope (FESEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The results show that compared to the general TiO₂ crystals with micrometre size, the anatase TiO₂ single-crystal nanosheets exhibit higher SBET and exposed (001) high-energy facets. And the sample shows good activity during the photocatalytic degradation of methyl orange compared to commercial P25.