Preparation Of N-doped Nano-TiO₂ And Its Porous Film And Study Its Photocatalytic Performance

TiO2 has been widely used for environmental treatment, purification purposes, and many other applications due to its outstanding stability, non-toxicity and high efficiency. In order to elevate the absorption capacity of TiO2 to visible light and relieve the application problem of TiO2 that a second pollution would be generated after degradation of pollutant with TiO2 powders, N-doped TiO2 photocatalysts and porous TiO2 films were prepared in this paper to modify TiO2, the concrete works are as follows:N-TiO2 photocatalysts were prepared by the modified sol-gel method, using tetrabutyl titanate as the precursor and hexamethylenetetramine, urea and ammonia as the nitrogen sources. The properties of samples were characterized and the influencing factors of the photocatalytic activity of the photocatalysts were also studied. Using MB as the target pollutant, the photocatalytic activity of various catalysts under three lights have been investigated. Results show that the crystalline sizes of all prepared samples are around 20nm and they are all anatase phases. N exists in the TiO2 lattice in the form of O-Ti-N and Ti-O-N and doping with N element is contribute to reduce the band gap energy of TiO2. The three kinds of N-TiO2 samples all show satisfactory photocatalytic activity under three light sources and among them, N-TiO2 doped with hexamethylenetetramine exhibits a better property and when the molar ratio of N and Ti is 0.20, the photocatalytic activity of the N-TiO2 reaches the best, which maybe owe to the fact that the complicated organic N molecule is more easily to be immobilized in the TiO2 lattice, therefore, to reduce the band gap energy of TiO2 and restrain the recombination of photogenerated electrons and hole, improve the absorption capacity of TiO2 to visible light. In this experiment condition, the photocatalytic activity of prepared catalysts will be better when the calcination temperature is higher, which due to the reason that calcination with high temperature is more advantage to generate a more ordered crystal form of TiO2, but as for the influence of calcination time, the change is slightly.N-TiO2 photocatalyst was prepared by the slow hydrolysis method, using tetrabutyl titanate as the precursor and triethylamine as the nitrogen source. P25 and the prepared N-TiO2 were then modified with kh550 in this study. Using P25, N-TiO2, modified P25 and modified N-TiO2 as the raw materials to prepare pastes and porous films. The synthesized powders and films were characterized by various techniques. Using MO as the target pollutant, the photocatalytic activity of the porous films was investigated. Results show that the preparation method of the pastes and films is simple and easy to execute and it’s suitable for the preparation of various TiO2 pastes and films. The crystalline sizes of all prepared samples are between 17nm-21nm and they are all pure anatase phases. N exists in the TiO2 lattice in the form of O-Ti-N and Ti-O-N. Doping with N element and modification with kh550 are all contribute to reduce the band gap energy of TiO2.The roasted films show obviously porous structure and good adhesiveness to the substrate. Using the four kinds of TiO2 films as the catalysts, the degradation rates of MO solution are 70%-90% under UV light and visible light and the average degradation rate of twelve time degradations of MO solution is 70%-82%, which shows that all the TiO2 films have a good photocatalytic activity and a strong durability.Surfactant-free emulsion polymerization was used to synthesize PS spheres, then using the prepared PS spheres as the template and N-doped, Fe-doped and N, Fe-codoped TiO2 sol as the filling liquid, assembled them on a glass substrate by vertical deposition method. After calcination, the N-doped, Fe-doped and N, Fe-codoped TiO2 nano-hollow composites were obtained. Adopted various test technologies to characterize their properties. Results show that the nano-hollow composite is pure anatase phase, N exists in the TiO2 lattice in the form of O-Ti-N and Ti-O-N. After calcination, the composite presents a hollow structure.