Preparation And Photocatalytic Performance Study Of Composite Nano-Photocatalysts

In recent years, the heterogeneous photocatalysis for the degradation of organic water pollutants using nano-TiO₂ semiconductors has been studied extensively in environmental science. The photocatalytic degradation technique has many advantages, such as carried out under ambient temperature and normal pressure, decomposing organic pollutants completely without second pollution. There are many methods in the preparation of nano-TiO₂ powders at present, but the photocatalytic activity of nano-TiO₂ powders prepared by various methods is much different. It is very important to find out a better method by which the catalysts possess good photocatalytic activity and thermal stability. Except for those advantages, nano-TiO₂ powders have some deficiencies, so it is necessary to modify TiO₂ by the adulteration to improve its photocatalytic activity. In this thesis, the comparative study of the properties of nano-TiO₂ powders prepared by different preparation methods was carried out. We did some experiments about the modifacation of TiO₂ through the SiO₂ adulteration, and the photocatalytic performances of the samples were examined. Some results were obtained as follows:Nano-TiO₂ powders were prepared by chemical precipitation method, sol-gel method and microemulsion method, respectively. The comparative study of the properties was carried out. Different preparation methods led to morphological and structural changes. X-ray diffraction (XRD) and transmission electron microscope (TEM) results showed that the particles synthesized by chemical precipitation method are single crystals of the anatase phase, with uniform and smaller particle size. Photocatalytic performance investigation of the TiO₂ particles in the photodegradation reaction of the methylene blue solution demonstrated that the TiO₂ powders prepared by chemical precipitation method have higher photocatalytic activity than those prepared by the other two methods.The TiO₂-SiO₂ composites were also prepared by chemical precipitation method, sol-gel method and microemulsion method, respectively. The result showed that the SiO₂ adulteration inhibits the accretion of the paticles, makes the crystal phase more stable and the particle size much smaller than the pure TiO₂. Among the samples prepared by the three methods, chemical precipitation method is relatively simple and the adulteration effect of the sample prepared by this method is the best.The TiO₂-SiO₂ composites with different SiO₂ content were synthesized. The result of photocatalytic experiment showed that on the condition of lower adulteration amount of SiO₂ the photocatalytic activity of the TiO₂-SiO₂ composites prepared by both chemicalprecipitation method and sol-gel method is promoted with the increase of SiO2 content.