Preparation Of Nitrogen Doped TiO₂ And Photoactivity Under Visible Light Irradiation

Titanium dioxide, a photocatalyst, has received a great deal of attention owing to its advantage such as long term stability, non-toxicity and low cost. In order to improve photoactivity for further application, investigations about how to extend its light absorbance into visible light region have become a focus. Of all the means to achieve this purpose, negative ion-doped TiO₂ has been proved to be the best route. And nitrogen doped TiO₂ is considered to be the most efficient way.In this paper, N-doped TiO₂ powders were obtained in an economic and easily performed way by using tetrabutyl titanate and urea. The prepared powders were characterized by XRD, UV-Vis, FTIR, N₂ adsorption, Fluorescence spectroscopy, etc. N-doped TiO₂ evidently shows its absorbance shoulder shift into visible light region. Moreover, N-doping retards the transition of TiO₂ from anatase to rutile type as well as restrains the growth of the crystal size which leads to less decrease of surface area. These characteristics are considered to benefit the photoactivity of TiO₂; When all the samples were applied to the photodecomposition of Methylene Blue under visible light(λ＞400 nm), the N-doped TiO₂ show an obvious superiority when compared to the undoped TiO₂, the active hydroxyl groups are found to play a important role in this high photoactivity; When the same experiment was performed under UV light, all the samples show the consistent sequence of photoactivity as in the visible light.In order to decrease the recombination of the photoexited holes and photoexited electrons in the Nitrogen doping sites, Fe(NO₃)₃,KClO₃,KBrO₃ and KIO₃ were chosen as electron acceptors. The levels of improvement to the N-doped TiO₂ vary from different electron acceptors as well as different concentrations of the same electron acceptor. KBrO₃ shows the best improvement of all. Under the same condition, compared to the undoped TiO₂, N-doped TiO₂ powders are more sensitive to KBrO₃ and show a greater improvement in degrading Methylene Blue.