Controlled Structure And Photocatalytic Properties Of Oxide Semiconductor

Today,social and economic developments are very rapid,but at the same time the economic development has brought a heavy burden on the environment.People now are using many technical means to control pollution.In 1972,TiO2 was found be an efficient semiconductor electrode that can decompose water.After then,photocatalytic technology has become a major part of scientific research.Photocatalytic technology is a kind of technology that makes use of sunlight to decompose organic matter into nontoxic and harmless carbon dioxide and water.The catalyst which are the most commonly usedare TiO2,ZnO,metal titanate and so on.However,the band gap of oxide semiconductor is generally more than 3 eV.Thus,they are nearly inactive under visible light irradiation so that sustainable solar energy can't be used adequately.Many efforts have been devoted to overcome the shortcomings and enhance the photocatalytic activities of these pholocatalysts,especially in the visible light range.It is a very effective way to control the;semiconductor band and extend the range of light response by adjusting the electronic structure of semiconductor material,such as ion doping,solid solution,etc..In addition,there are other methods such as semiconductor composite,noble metal deposition and surface photosensitization to broaden the range of the optical response.In this thesis,TiO2 and FeTiO3 were used as the research subject,and the structure of TiO2 and FeTiO3 were modified by element doping and solid solution formation,respectively.The main contents are summarized as following:Firstly,a series of Se-doped TiO2 nanoparticles of anatase structure with various Se concentrations up to 17.1 at.%have been prepared using sol-gel method.The synthesized samples were characterized by XRD,XPS,UV-DRS and so on.XRD patterns showed the Se atoms enter the TiO2 crystal structure.XPS results reveal that the doped Se ions have been confirmed to be mainly in the valence state of +4.UV-DRS results indicate the Se-TiO2 catalysts have enhanced absorption in the visible light region.The photocatalytic activities were evaluated by photocatalytic decolorization of RhB under visible light irradiation.Se-TiO2 photocatalysts exhibit better photocatalytic activity than that of un-doped TiO2.We prepared Se-TiO2 with various Se doping concentration to further study the optimum value of Se doping concentration.The band gap has been effectively narrowed down to 2.17 eV.The experimental results show that when the actual doping concentration of Se is 13.63 at.%,the sample exhibits the best photocatalytic efficiency,which is due to the narrowed band gap of 2.58 eV in the visible range and the optimum defect density to efficiently suppress the recombination of electron-hole pairs.Secondly,the preparation technology of pure phase FeTiO3 was explored,and pure phase FeTiO3 has been prepared by hydrothermal method,and the FeTiO3-Fe2O3 solid solutions with varous compositons were prepared by the same method.The photocatalytic activities and ferromagnetism were evaluated.0.6 FeTiO3-0.4 Fe2O3 has the best photocatalytic activity,while the composite of 0.9 FeTiO3 has the strongest ferromagnetism.However,ferromagnetism can also be observed in 0.6 FeTiO3-0.4 Fe2O3,which may facilitate its recovery.