Preparation Of Modified Mesoporous TiO₂/CdS Nanocomposite Photocatalysty And Study On Its Performance

With the decrease of fossil fuels such as coal and oil and the growing environmental pollution, the development of clean and renewable energy with enormous reserve and the energy efficient techniques for environmental contaminants treatment attracted wide attention for recent several decades. Chemical pollution is the main source of the environment pollution especially the nonbiodegradable organic dyes and some toxic macromolecules. Usually we use physical adsorption and chemical oxidation method to treat these pollutants. Titanium dioxide is considered as one of the most effective photocatalyst for environmental contaminants treatment due to its stable chemical properties, strong oxidizing ability, low cost and non-toxic properties. Titanium dioxide can effectively catalyze the degradation of organic pollutants under the UV irradiation, and some of the dye also to be degraded under the condition of visible light. In addition, Titanium dioxide and some other photocatalysts can catalyze the decomposition of water to produce hydrogen fuel, which is believed to be one of the possible ways to solve the energy shortage in the future. But the photocatalytic performance of titanium dioxide is limited by its wider band gap because it can only absorb the UV-light less than five percent in the sunlight. So the modification of titanium dioxide is critical.Based on the analysis of the electronic structure and the photocatalytic mechanism of titanium dioxide, we optimized the synthesis way and prepared the TiO2/CdS nanocomposite photocatalyst. The titanium dioxide photocatalyst was modified by the composition with narrow band gap semiconductor in this work. Mesoporous Titanium dioxide photocatalyst was prepared by sol-gel method and hydrothermal method with isopropyl alcohol as the titanium source. The microstructure of mesoporous titanium dioxide was controlled during the synthsis process. The grain size of CdS nanoparticles was adjusted by the curing temperature. The microstructure and photocatalytic properties of TiO2/CdS photocatalysts obtained by the ion exchange and codeposition method were compared. It was found that the mesoporous TiO2/CdS prepared by our ion exchange method showed much higher photocatalytic activity than that prepared by the codeposition method. The main research content of this essay is as follows:(1) Synthesize mesoporous titanium dioxide with different templates such as P123, F127and CTAB by sol-gel method and hydrothermal method. The microstructure of TiO2/CdS nanocomposite photocatalyst was controlled through the different crystallization temperatures, crystallization time, calcination temperature and the temperature during vulcanizing process by Na2S and thiourean. The microstructure and the light absorption characteristic of the prepared mesoporous TiO2/CdS were studied by XRD, HRTEM, nitrogen isotherm studies, FTIR and UV-vis diffuse reflectance spectra. The results clearly indicated that mesoporous TiO2showed best mesoporous structure at the crystallization temperature of90℃.(2) Control the loading process of CdS nanoparticles by different vulcanization temperature and explore the absorption properties of TiO2/CdS nanocomposite photocatalyst.(3) Synthesize TiO2/CdS nanocomposite photocatalyst by ion exchange method and codeposition method with mesoporous titanium dioxide as support and determine the photocatalytic performance throught photocatalytic degradation of dye and phenol.