Of Pb (2 +) (la (3 +), Ag)-tio <sub> 2 </ Sub> Optical Catalytic Materials Wet Chemical Method And Performance Research

In this thesis, semiconductor photocatalysis materials, especially the development and application of nanosize TiO2 are reviewed comprehensively. Nanosize TiO2 had been one of the hotspots in the research field of semiconductor photocatalysis materials because of its excellences such as high photocatalytic activity, long continuance, good thermodynamic stability, cheap price and harmlessness. Photocatalytic principle of Nanosize TiO2 and effect factors of catalytic activity and preparation methods are also reviewed in this thesis. At the same time, problems and methods for resolving them in the research of Nanosize TiO2 are analyzed and discussed.In this research, Nanosize TiO2 were prepared by wet chemistry method. The effects of technical condition, ion doping and noble metal modification on crystal structure of Ti02, crystal size and its distribution, spectrum and photocatalytic activity were studied in order to prepare Nanosize TiO2 of high photocatalytic activity. Effect factors such as temperature in photocatalytic process were also studied.The nanosize TiO2 doped with different concentrations of Pb2+ and La3+ were prepared by Sol-Gel processing. Pb2+ and La3+ doped TiO2 samples were analyzed by XRD and TEM measurement. The photocatalytic activities of the samples were also studied. Results showed that Pb2+ and La3+ replace Ti4+ in TiO2 crystal structure when the concentrations of Pb2+ and La3+ are smaller than 3.0at.% and 3.5at.% respectively. And this replacement would increase the transformation temperature from anatase into rutile and minish crystallite size and increase photocatalytic activity of TiO2. Some factors such as Anatase, expand degree of TiO2 crystal structure, crystal defect and crystal size influenced intensively the photocatalytic activity of TiO2. The optimal doping concentrations of Pb2+ and La3+ are 2.0at.% and 3.0at.% and the optimal heat treatment temperature are 700℃1.5at%) and 600℃. When the doping concentrations of Pb2+ and La3* on TiO2 samples were more than needed, PbO and would be separated out of the samples and the photocatalytic activity of theTiO2 samples would be decreased.Nanosize TiO2 and nanosize Ag-TiO2 were prepared in hydrothermal condition. Nanosize TiO2 samples and nano Ag-TiO2 samples were analyzed by XRD, TEM and DRS. The results showed that the uniform anatase nanosize TiO2 (size<10nm) could be prepared in hydrothermal condition when the system was made up of Ti(OBu)4 and C2H5OH, and the heat treatment temperature ranged form 180℃ to 280℃. Absorption thresholds of DRS are found toward the higher energy region with the decreasing of particle size. But the fluorescence emission peak positions were not blue shifted with the decreasing in particle size of TiO2. The uniform Anatase nanosize Ag-TiO2 (7-20nm) were prepared in hydrothermal condition when the system was made up of Ti(OBu)4, C2H5OH and AgNO3, and the heat treatment temperature ranged form 180℃ to 280℃. Ag+ existed in the form of Ag in nanosize Ag-TiO2. The band gap of TiO2 decreased after Ag doped. When the concentration of Ag was below 2.5wt%, doped Ag could participate in the photocatalysis reaction and help the degradation of the organic materials.In this thesis, the relationship between environment temperature of photocatalysis reaction and photocatalytic activity of nanosize TiO2 and nanosize Ag-TiO2 was studied. Results found that the photocatalytic activity in low environment temperature (8℃) was higher than in high environment temperature(30℃). This phenomenon indicated that the density of surface hydroxyl groups was most important for the photocatalytic activity.