Synthesis And Photocatalytic Properties Of New Titanium Dioxide Photocatalytic Materials

TiO₂semiconductor has been proven to be the most suitable for photocatalytictreatment of organic pollutants in widespread environmental applications amongvarious photocatalysts, owing to its high photocatalytic performance, chemicalstability, non-toxic, and low price. TiO₂-based heterogeneous photocatalysis hasmany advantages compared with the traditional pollution treatment technology, suchas: the use of solar energy, degradation of organic matter without selective, simpleand easy to operation, and no secondary pollution. However, there are still a lot ofproblems in TiO₂-based photocatalysis such as low quantum efficiency and littleutilization of solar energy and so on. As a result, it is the main direction of scientificdevelopment to photocatalysis that how to solve these problems and make thephotocatalytic technique be widely used in practice.The synthesis of new TiO₂materials is an effective way to improve theperformance of the TiO₂photocatalyst, and the synthesis of Mesocrystal TiO₂material and non-metallic ion modified TiO₂photocatalytic materials is the hot spotin such field. Our research work focuses on TiO₂photocatalysts and begins from thesynthesis method. We will study the controlled synthesis of mesocrystal TiO₂material and develop efficient nitrogen-doped TiO₂material.The detailed works are as follows:1. Solvothermal alcoholysis synthesis of spherical mesocrystal TiO₂and itsphotocatalytic propertiesThe mesocrystal TiO₂is synthesized by solvothermal alcoholysis with TiOSO₄inethanol and benzyl alcohol as a mixed solvent under low temperature. The sphericalmesocrystal TiO₂has the porous structure and high surface are （SBET=188m2?g-1）.The results show that the porous structure is formed by the accumulation of TiO₂nanocrystals, while these TiO₂nanocrystals orientation to maintain the same latticeand the SO42-adsorbed on the high energy surface of TiO₂can stabilize the （001）facets by lowering the surface energy, leading to the oriented crystal growth. Thedetailed morphologies and structures of mesocrystal TiO₂are analyzed and characterized using FESEM, TEM and XRD characterizations and the formationmechanism is proposed. Spherical mesocrystal TiO₂is applied to phenol degradationexperiments which show the higher photocatalytic activity and applied to thephotocatalytic degradation of methyl orange which showed the35%higher thancommercial TiO₂（P-25）.2. Solvothermal alcoholysis synthesis of size controlled spherical mesocrystalTiO₂and its photocatalytic propertiesSize controlled spherical mesocrystal TiO₂is synthesized by solvothermalalcoholysis with TiOSO₄in ethanol and benzyl alcohol as a mixed solvent under lowtemperature by adjusting the volume ratio of alcohols. The results showed that thesize of spherical mesocrystal TiO₂is controlled from80to about2000nm. Usingdifferent alcohol solvents, such as isopropanol or n-butanol substituted benzylalcohol can also be obtained similar results.3. Preparation and photocatalytol activity N-doped TiO₂visible lightphotocatalyst from two N-sourcesA highly active N-doped TiO₂visible light photocatalyst was prepared by animproved precipitation method. Ammonium oxalate and ammonium hydroxide wereused as the nitrogen resources and worked as in-situ release and pre-addition of theN elements to modified TiO₂, respectively. The prepared photocatalysts werecharacterized by the BET, XRD, UV-Vis, XPS and IR spectrum. The model reaction ofdegradation methylene blue was used to test the photocatalytic activity ofphotocatalyst under visible light. The results showed that the TiO₂photocatalystmodified by the two N sources displayed higher photocatalytic activity than thesingle N source or post-modifying TiO₂photocatalysts, due to that the two N sourceswere beneficial to make N atoms into the TiO₂lattice.