Synthesis And Photocatalytic Properties Of Metal Ion Doped Mesoporous TiO₂ Materials

TiO2, as an N-type semiconductor, has a wide application prospect in the fields of photocatalyst, photo-induced/electrochromic, sensors, solar cells and self-cleaning glass because of its unique electronic and optical properties. In the realm of photocatalysis, titanium dioxide is widely used to degrade the various pollutants and purify the environment for its biochemical inert, non-toxic, chemical stability and other characteristics. Mesoporous TiO2, which has high surface area and abundant pores, is more suitable for catalysis. However, the photocatalytic properties of pure TiO2 is not sufficient to the industrial application, so many researchers carried out the study to modify TiO2 for improving its photocatalytic activity. In this paper, we used two different preparation and metal doping methods to modify the mesoporous TiO2, the microstructures and photocatalytic activity of the samples were examined by some advanced technologies. The mechanism of the photocatalysis decomposing polluents was studied, which provide a theoretical basis for the practical application. The main contents are summarized as follows:1. Mesoporous TiO2 and W-TiO2 particles were prepared by the soft template method, using P123 as the template, tetrabutyl titanate and tungsten phosphoric as the precursors. The sample calcined at 550℃has good anatase and worm-hole structure, higher temperature would cause rutile phase and collapse of the pores. The morphology structure and photocatalytic properties of the materials were tested by XRD, SEM, TEM, XPS and UV-vis. The experimental results showed that W dopant introduced a new impurity energy level, and reduce the electron-hole recombination rate. The W-doped mesoprous TiO2 have better photocatalytic reactivity, the optimum content is 5%, which would degrade about 80% of the methylene blue within 70 min.2. Mesoporous TiO2 and W-doped TiO2 particles were synthesized by hard template method using SBA-15 as the template. The influence of different acids (HCl, HNO3) were tested, the results showed that TiO2 (HCl) is anatase and TiO2 (HNO3) is rutile. Thus the mesoporous TiO2 based photocatalysts were synthesized by hydrochloric acid. The materials were analyzed by XRD, SEM, TEM, BET, XPS, UV-vis, the result showed that the mesoporous TiO2 synthesized by hard template method has more orderly pore structure, compared with that obtained by the soft template method. The 5% W-doped TiO2 (hard template method) could degrade about 95% of methylene blue in 70 mins, which is more efficient than that synthesized by soft template. It indicated that the more ordered the mesoporous structure, the better photocatalytic activity.3. Mesoporous Mn-doped TiO2 samples with different Mn doping contents were synthesized by using SBA-15 and manganese acetate. The samples were analyzed by various characterization and photodegradation techniques. It is indicated that Mn-doped TiO2 particles have ordered mesoporous structure, Mn ions entered into TiO2 lattice and replaced the Ti ions. The incoporaton of Mn dopants reduced the photoelectron-hole recombination rate and expanded the light response to the visible light range. The Mn dopant significantly improved the photocatalytic activity of TiO2 under the visible light irradiation.