Preparation And Photocatalytic Application Of Titanium Dioxide Nanomaterials

Semiconductor photocatalytic oxidation technology has been established to be one of the most promising methods for environment remediation. Among various semiconductors, TiO2 has been considered as an excellent photocatalyst for degradation of pollutants compounds in air and water for its nontoxicity, cheapness, and chemical stability. However, the relative large band gap of TiO2 (3.2 eV for the anatase phase and 3.0 eV for the rutile phase) requires ultraviolet (UV) light for electron-hole separation which is only 5% of the natural solar light. It is of great significance to develop photocatalysts that can be used in both UV irradiation (290-400 nm) and visible light (400-700nm) to enhance the photocatalysis efficiency. One approach is to dope various coumpounds into TiO2 at the Ti sites. In this paper, we investigated fabrication of doped TiO2 and evaluated their potential photocatalytic applications. We investigated the synthesi of two metals transition doping on titanium dioxide:(ⅰ) CuF2 doped TiO2 nanosheets and (ⅱ) Mn doped nanoparticles. In both cases our main focus has been optimizing material synthesis for improving potential applications based on photodegradation of organic dyes.CuF2 doped TiO2 nanosheets and Mn doped TiO2 nanoparticles were prepared by different methods and characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction infrared spectroscopy(XRD). The Photocatalytic activity of the synthesized products was studied. The synthesized products have not been studied previously, so it is significant to study their physical and chemical properties detailedly. The main contents and results of this thesis are shown as follows: 1. CuF2 doped TiO2 anatase nanosheets were synthesized by a simple hydrothermal method of a mixed solution containing tetrabutyl titanate, cupric nitrate, poly (vinylpyrrolidone) and hydrofluoric acid. The SEM results indicated that the synthesized product consisted of sheet-shaped structures with the side length of about 60 nm. These products were applied to the photodegradation of methyl orange. It was found that the photocatalytic activity of the product was greatly enhanced after CuF2 doping. Moreover, our synthesized product exhibited the highest photocatalytic activity under visible light irradiation compared to TiO2 (Degussa, P25). The best result was obtained when the product was synthesized at 160℃for 36h. The remarkable efficient visible light photocatalytic activity is largely attributed to the unique morphology of the products and the CuF2 doping. These new photocatalysts present a promising way to improve the photocatalytic activity of TiO2 for water treatment and other applications.2. Mn doped TiO2 nanoparticles were successfully synthesized by a simple solvothermal method using tetrabutyl titanate and manganese sulfate as the precursors. The products were characterized by X-ray diffraction, scanning electron microscopy equipped with energy dispersive X-ray micro-analysis (SEM-EDS). The results showed that Mn doped TiO2 nanoparticles were in good crystalline in anatase phase for unannealing products and in anatase mixed rutile phases for the calcined products at 600℃. The synthesized products were applied to photocatalytic decomposition of calconcarboxylic acid. It was found that the photocatalytic activity of unannealing TiO2 doped with 0.011M MnSO4. is higher than pure TiO2 and the calcined products. The effects of Mn, ammonia content and the calcination temperatures on the products were investigated in this study.