| Titanium dioxide (TiO2), a semiconductor material with excellent performance as a photocatahyst is widely used in solving environmental pollution and energy shortages. Due to its good photocatalytic activity, high chemical and thermal stability, environment friendly property and excellent degradation and adsorption capacity of organic dyes, TiO2has been received largely attention and lots of research on it. However, the traditional TiO2materials have a high recombination rate of photo-generated electron-hole pairs, resulting in low quantum efficiency, thereby reducing the photocatalytic activity. And because of it widely band gap, TiO2can only use the ultraviolet rays, which greatly limits the actual TiO2utilization. In recent years, realization of anionic nonmetal doping and high energy crystal facets exposure in TiO2photocatalysts has been proven to be effective approaches for significantly improving their photocatalytic performance.Based on the above research background, the main purpose of this thesis is to synthesize and study the photocatalytic activity of a series of TiO2nanoscaled catalysts for degradation of organic dyes, and we successfully improved the catalyst activity by optimizing the synthesis conditions.In the first chapter, the previous research of crystal structure, photocatalytic mechanism and its application of TiO2catalysis were introduced. In addition, modification methods and exposed{001} surface research status of TiO2photocatalysts were reviewed.In the second chapter, we introduced SiO2spheres as hard template, a series of SiO2@TiO2structures and hollow spherical nano-TiO2catalysts were prepared in the solvent system of ethanol and acetonitrile by adding with tetrabutyl titanate. Hollow spherical anatase TiO2catalyst with evenly shell structure, mechanical stability and well crystallization was obtained. The catalytic performance of@antase TiO2catalyst for degradation of methylene blue(MB), methyl orange(MO) and rhodamine B(RhB) were systematically investigated and better than commercial P25.In the third chapter, cubic TiO2exposed with high-energy{001} facet structure was synthesized under hydrothermal conditions by using hollow spherical amorphous TiO2powder as the precursor and NH4F as the capping and morphology control agents. SEM and TEM displayed that TiO2cubes with regularly morphology, well monodispersity and uniform size about30-50nm were prepared. Because of{001} facet was exposed, which is not only beneficial for the conduction of electrons, but also reduces the TiO2band gap width, thus cubic TiO2showed excellent photocatalytic properties. By adjusting the ratio of the concentration of reactants, reaction time, temperature and hydrothermal conditions, we also optimized the process for preparing the catalysts, and obtained TiO2spheres composed of ultrafine nanoparticles, flaky spheres and nanospindles structure of TiO2.In the fourth chapter, ionic liquid1-butyl-3-methylimidazolium tetrafluoroborate([Bmim][BF4]) was used as the F source, a facile strategy of ionic liquid assisted etching chemistry by simply hydrothermally etching hollow TiO2spheres composed of TiO2nanoparticles is developed to create highly active anatase TiO2nanocube assembles with{001} facets exposed under hydrothermal conditions. The morphology of such catalyst is not only novel, but also in the visible-light condition exhibits excellent photocatalytic activity. With this one-pot ionic liquid assisted etching process, the surface-fluorination and nitridation and high energy {001} crystal facets exposure can be readily realized simultaneously. The ionic liquid assisted etching chemistry is facile and robust and may be a general green strategy for synthesizing other metal oxides with high energy crystal facets and surface doping for improving photocatalytic activity. We also prepared the antase TiO2nanocubes with regularly morphology by adjusting the synthetic methods and solvents. |
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