Studies On Preparation, Characterization And Performance Of Mesoporous TiO₂ Photocatalytst

Heterogeneous semiconductor photocatalysis is a popular technique that has great potential to solve pollutants and utilize solar energy. Among various oxide semiconductors, TiO₂ has been proved to be the most suitable photocatalyst for widespread environmental applications because of its biological and chemical inertness, strong oxidizing power, nontoxicity and long-term stability against photo and chemical corrosion. However, the fast recombination rate of photogenerated electron/hole pairs in the bulk TiO₂ and the low efficiency of the solar spectrum (about 4% UV light) hider the commercialization of this technology. On the other hand, because of its large band gap, TiO₂ is effective only under ultraviolet irradiation (λ < 387 nm). In recent years, many attempts, such as finding new preparation methods and using modifications, have been made to improve the photocatalytic activity of TiO₂. One of the most efficient methods is doping.In order to resolve the low photocatalytic efficiency of bulk TiO₂ and to explore its application in environment remediation, we used new preparation methods and doped some elements in the samples to enhance its performance. The prepared catalysts were characterized by some advanced technologies and their activities were measured using an online method. The effects of preparation methods and doping elements on the photocatalytic activity was investigated and discussed. In this dissertation, some new and interesting results are as following.1. Highly photocatalytic active mesoporous nanocrystalline TiO₂ powder photocatalyst could be prepared using a sonochemical technique without using any templates or surfactants at low temperature. The sonication promoted the hydrolysis of Ti(OC₄H₉)₄, crystallization of TiO₂ and formation of mesopore. All the samples prepared by ultrasonic method showed better photocatalytic activities than Degussa P25 and the samples prepared by conventional hydrolysis method. This may be ascribed to the facts that the samples prepared by ultrasonic method have high specific surface area, small particle size and bi-phase structures. The formaldehyde is more easily photocatalytic decomposed than acetone due to its less carbon atoms and smaller space hindrance.