Preparation, And Visible-photocatalytic Performance Of Nitrogen Doped TiO₂ And TiO₂/SiO₂

With global population growth and economy development, photocatalytic oxidation has attracted wide attention on the environmental protection. Therefore, the development of photocatalyst has become one of the most popular research subjects in the world. A number of researches on visible-light driven catalysts have been made to utilize the solar rays efficiently in photocatalytic reactions. Nonmetallic element nitrogen doping of TiO2 is becoming the focus as it can improve the photocatalytic activity both under ultraviolet radiation and visible light.In this study, nano-sized TiO2 powders were prepared by hydrolysis-deposition method. Nitrogen-doped titania (N-TiO2) were prepared by microwave synthesis and annealing under NH3 flow. The effects of crystal phases of TiO2 on N species types and photocatalytic performances of N-TiO2 were studied. A novel N-doped TiO2 (N1-N2-TiO2) with substitutional and interstitial N impurities simultaneously was successfully synthesized by annealing under NH3 flow-microwave method. The photocatalytic performance of the photocatalyst has been evaluated by photodegradation of methyl orange under UV-vis light and visible light irradiation. we successfully synthesized nitrogen-doped TiO2/SiO2 using SiO2 template sol-gel method. The catalysts were characterized by many methods. The overall conclusions are as follows:(1) Anatase TiO2 and rutile TiO2 are successfully synethesized. Nitrogen-doped titania (N-TiO2) were prepared by microwave synthesis and annealing under NH3 flow. The effects of crystal phases of TiO2 on N species types and photocatalytic performances of N-TiO2 were studied. The results showed that N species types of substitutional and interstitial N-TiO2 were decided by different preparation methods, not changed with crystal phases of TiO2. After nitrogen doped by two kinds methods, photocatalytic activities for TiO2 with anatase or rutile phase were enhanced obviously in visible light, but not improved evidently for N-TiO2 with compound crystal of anatase and rutile.(2) A novel N-doped TiO2 (N1-N2-TiO2) with substitutional and interstitial N impurities simultaneously was successfully synthesized. The catalyst was characterized by X-ray photoelectron spectroscopy (XPS). The result indicated that nitrogen was substituted for the lattice oxygen atoms, and was also interstitially doped into the TiO2 lattice. The optical response of TiO2 was shifted from UV to the visible light region with the introduction of nitrogen. The photocatalytic tests indicated that the N1-N2-TiO2 showed the highest photocatalytic activities in all the N-doped TiO2 under visible light, attributing to the synergetic effects of substitutional and interstitial nitrogen of N-doped TiO2.(3) We successfully synthesized nitrogen-doped TiO2/SiO2 using SiO2 template sol-gel method and then doping N with microwave method. For sol-gel method, the optimal conditions were the calcinations temperature of 800℃and reaction time of 2 h. No rutile phase was found until the calcination temperature to 800℃. Their surface states were clarified by Nls, Ols and Ti2p XPS. The results showed that N species types in N-TiO2 was not changed with SiO2. The N-TiO2/SiO2 exhibited higher photocatalytic activity.