Investigation Of Modification Of Nano-TiO₂ By Doping And Its Photocatalytic Properties

With the rapid development of industry, energy crisis and environment pollution become more and more serious. So how to save energy, how to control and deal with the enviroment pollution have been the most important thing nowadays. Among all the nano-photocatalytic materials, TiO2 become a most promising photocatalyst for its strong oxidation activity, stability and nontoxic. However, TiO2 has two main disadvantages: Firstly, low quantum yield and low photocatalytic activity. Secondly, large band gap energy (3.2ev) which is only active to ultraviolet light and thus waste energy source. Therefore, how to modify TiO2 in order to increase its photocatalytic activity and extend its range of photo-response spectrum is the key to further utilize in photocatalysis. In this paper, on the foundation of summarizing the development of the modification of nano-scaled TiO2 photocatalyst, the following aspects were mainly studied.1. In order to raise the photocatalytic activity, TiO2 was modified by doping Bi ions and Eu ions using combustion method. Doping mechanism was investigated and photodegradation experiments were made to find the best ion concentration of Bi and Eu. The results showed that ions doping can lead to lattice aberrance, thus reducing the recombination of electrion-cavity pairs and increasing quantum yield photocatalytic activities. The optimum doping concentration was different according to different doping ions. The optimum doping concentration of Bi ions is 3% while the optimum doping concentration of Eu ions is 0.5%. 2. Non-metal doping TiO2 have been studied in order to extend its range of photo-response spectrum and increase its photocatalytic activity. N-doped TiO2 and S-doped TiO2 photocatalysts were prepared using sol-gel method, sovolthermal method, respectively. The crystal structure, morphology, BET and absorbency were characterized by XRD, TEM, IR, BET, UV-vis spectrophotometer. Compared with pure TiO2, the grain size of the doping samples was smaller, the BET was larger. The absorbency increased greatly in the visible region because of the narrower of the band gap and the formation of doping level. The photocatalytic activity of photocatalysts was investigated to be high by degrading methylorange and the samples all have a good photocatalytic properity under visible-light irradiation.3. N-La co-doped TiO2 crystals were synthesized using sol-gel method. The effect of ion doping concentration to photocatalytic activity was investigated. Results show that the highest photodegradation was obtained at the optimum concentration of N5% and La 0.5%. Based on the study of N-La co-doped TiO2 nano-sized photocatalysis, N-La co-doped nano-sized photocatalysis films were synthesized. The effects of co-doping and film layers to lattice deformation and photocatalytic activity were studied. The results showed that La3+-doped samples with bigger ion radius could easily result in lattice deformation, and the replacing of Ti4+ with La3+ could form structure defect which was favour for hydroxylation of the surface grains to obviously heighten the photocatalytic activity of films. The films with four layers possessed the highest photodegradation ratio. The degradation ratio to methylorange and nitrobenze under UV irradiation for 3h was up to 73.98%, 96.29%, respectively. At the same time N doping could narrow the bang gap energy, thus result in the red-shift of absorption edge and increase the photocatalytic activity responding to visible light. The degradation ratios to methylorange and nitrobenze were 56.19% and 87.86% after irradiating under visible-light for 3h. It can be seen that N-La co-doping can not only extend the wavelength to visible light but also maintain good property under UV light, which exhibit new application foreground in the use of solar light.In a word, TiO2 photocatalysts were modified by different ions doping and many significative results were obtained including ion doping concentration, preparation methods, degradation efficiency, photocatalysis mechanics and so on. To a certain extent all the results had some innovation, and at the same time laid the foundation for the further study and practical application on nano-photocatalysts.