| TiO2 semiconductor oxide is one of the most promising photocatalytic materials owing to its superior properties, such as cheap, non-toxicity, easy acceptance, chemical stability and photo-stability, and strong oxidizing power. However, two main limitations are encountered when using this material:its efficiency is limited by charges recombination after excitation and its absorption is mainly located in the UV range which represents only 3%-5% of solar spectrum. Many efforts have been attempted to enhance the photocatalytic efficiency of TiO2, such as morphology controlling, metal or nonmetal elements doping, noble metal loading, coupling with narrow band gap semiconductors, and so on.Innumerable researches have proved that anatase TiO2 single crystals with a large percentage of (001) facets own an enhanced photocatalytic property, but the efficiency still cannot meet the requirements of practical application. In this thesis, we attempt to enhance the photocatalytic efficiency of anatase TiO2 single crystals with a large percentage high energy facets through morphology controlling, noble metal Ag loading, coupling with narrow band gap semiconductors Ag2O. Related research results are as follows:(1) Using Ti powder as titanium source, through a simple hydrothermal synthesis method prepared nanosheet-assembled anatase TiO2 microspheres. The physical and chemical properties of nanosheet-assembled anatase TiO2 microspheres were well characterized by XRD, SEM, XPS, BET and other analysis methods. The photocatalytic reduction and oxidation activities of the as-prepared sample were evaluated by removing heavy metal Cr (VI) and degradation organic dyes (Methyl orange (MO); Rhodamine B (Rh B)), respectively. The experimental results showed that compared with P25 and commercial pure anatase TiO2, nanosheet-assembled anatase TiO2 microspheres exhibited very excellent photocatalytic.(2) TiO2 single crystal with high energy facet was successfully synthesized through a simple sinter method by use HF acid as facet-controlling agent. Noble metal Ag was selectively loaded on high energy facet of TiO2 single crystal through sonochemical deposition. After silver nanoparticles deposited, light absorption property of the sample in visible light region was strongly enhanced and the photocatalytic efficiency for Rh B degradation was improved clearly.(3) TiO2 single crystal nanosheet with a large percentage of high energy (001) facets was prepared through solvent-thermal method by use butyl titanate as titanium source, HF acid as morphology control agent, thiourea as surface active agent. The influence of the amount of titanium source and surface active agent to the morphology of TiO2 single crystal nanosheet was discussed. Noble metal Ag was selectively loaded on (101) facets of TiO2 single crystal through sonochemical deposition, and the influence of sonochemical time to the samples was studied. Experiments results showed that 10mL butyl titanate,0.10g thiourea and 50min sonochemical are the optimization parameters for the samples. Due to its special structure, Ag selectively modified TiO2 single crystal nanosheet exhibited excellent photocatalytic performance for the degradation of Rh B.(4) The Ti3+self doped TiO2 nanocrystals have been firstly prepared through a simple solvent-thermal method by sodium borohydride as reductant, subsequently the as-prepared product was modified with narrow band gap semiconductor Ag2O nanocrystals through a sonochemical depositing process. TEM analysis said that (001) and (101) facets individual exposed in as-prepared Ti3+self doped TiO2 nanocrystals. Ag2O and the two different TiO2 single crystal nanosheet formed a typical double Z-scheme, which showed an excellent photocatalytic oxidation degradation performance for Rh B under simulated sunlight. |
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