| In the 21st century, environmental and energy issues arc the greatest challenges for human.Semiconductor photocatalytic technology provides an effective way of controlling environmental pollution and efficient use of solar energy. In 1972. Japanese scientists, Fujishima and Honda, found TiO2 electrode as a single crystal could decompose H2O into H2 and O2 in the light conditions. TiO2, as a represented metal oxide semiconductor, was received widespread attention. TiO2 not only owning anti-corrosion ability, efficient, non-toxic, inexpensive, stable photochemical properties and many other advantages, but also owning environmentally friendly and biological function. Photocatalyst is now being widely used. However, TiO2 photocatalytic materials exist in the practical application have some problems as following:low quantum efficiency, narrow light response range, only absorbing the sun’s ultraviolet light, difficult to recycle, etc, binding the development and commercialization of its practical application. The dissertation revolved around titania-based photocatalysis material composition, structure and properties of the system to carry out in-depth research work on microstructure control in the high activity of titanium dioxide, doped with non-metallic, semiconductor compound and other aspects of photocatalytic enhancement achieved. Some researches results can be summarized as the following four areas:(1) A two-step hydrothermal method prepared a novel layered Ag@TiO2 core-shell nano-structured titanium dioxide. The diameter of Ag core is around 200 nm. but it seems not very uniform in size, the layered structure of the nano-chip portfolio. As the shell tightly wrapped Ag nanoparticles. it protects the Ag nanoparticles from corrosion and dissolution, and increases the contact area between the Ag and TiO:. Metallic silver, as the photo-generated electrons temporary, gathered place with a timely transfer of electronic functions. This enables efficient separation of photogenerated electron-hole pairs, slow electron-hole pair recombination. improved carrier utilization and increase Ag@h-TiO2 photocatalytic catalytic activity TiO2 hierarchical structure, specific surface area compared large, could absorbed more dye and enhanced the absorption of light scattering to improve the chances of light. Thereby, they enhancing the catalytic properties of the catalyst under visible light through eight cycles tested degradation of methyl orange and methylene blue. The results showed that it had good photocatalytic degradation.(2) One-step solvothermal synthesis of F-B co-doped TiO2 nanosheets. Fluorine boric acid as fluoride, boron source, titanium trichloride as titanium source, by adjusting the ratio, reaction temperature and time successfully prepared containing oxygen vacancies and exposed (001) plane of TiO2 nanoparticles. When HBF4 and TiCl3 volume ratio of 0.5:1, the reaction temperature and time were 200℃ and 12 h, the morphology of sample preparation for Nano-sheet and the diameter is not uniform, but uniform in thickness, about 70nm. The exposed (001) crystal face is not very smooth intact, but there are many recesses and pore structure. Compared to pure TiO2, due to the fluorine and boron synergy to improve the visible light photocatalytic activity of TiO2 photocatalyst, the UV-visible spectral range photocatalytic degradation of methyl orange showed better photocatalytic activity.(3) We have designed and fabricated rutile/anatase type Nano TiO2 heterojunction flower by-step solvothermal, cetyl trimethyl ammonium bromide (CTAB) as a template, titanium tetrachloride and urea as reactants. The XRD, SEM, TEM and BET were characterized. TiO2 heterojunction nano-flowers with rutile TiO2 for the skeleton, anatase nanocrystalline TiO2 as a catalyst loading on the surface, due to the energy between the rutile TiO2 anatase TiO2 with the differences, and its skeleton can become carriers of light transport natural channel, due to the rutile/anatase. The anatase phase heterojunction conduction band edge can be higher than the rutile phase, the photo-generated electrons are transferred from anatase to rutile phase,and holes from rutile to anatase phase shift, resulting in an effective electronic holes separation, improving photocatalytic activity. Study on the catalytic effect of methylene blue in simulated sunlight radiation.(4) We introducing isopropyl titanate fat as a source of titanium, cerium nitrate hexahydrate as cerium source. The products have a visible light absorption of narrow bandgap semiconductor composite material. CeO2 to the surface of TiO2 nanoparticle heterostructures. The prepared CeO2/TiO2 nano-junction spend UV composites from the UV-visible absorption edge of the area to broaden the visible region, thereby improving the light response range. XRD, SEM, TEM, UV-vis and other methods of sample preparation morphology and structure were characterized. The methyl orange as target pollutants investigated the photocatalytic properties of the sample. The conduction band bottom potential of CeO2 is higher than that of TiO2 CeO2 conduction band electrons, the potential of the conduction band, can be excited easily transferred from the contact surface of both the conduction band of TiO2 and TiO2 holes. The valence band can be injected into the valence band generated by the contact surfaces of both the CeO2. This makes the photo-generated electron-hole pairs separated quickly and help improved the photocatalytic activity. In addition, CeO2 excitation of electron-hole pair photogenerated electrons from the conduction band spread CeO3 to TiO2 conduction band under visible light. The photogenerated TiO1 can be transferred from the holes valence band to the valence band of CeO2. Thus, these contribute to the electron-hole pair separation and help to improve the photocatalytic activity. |
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