Study On The Controllable Preparation And The Photocatalytic Properties Of Nano-TiO₂

Nano-TiO₂ particle has drawn more and more people's attention owing to the smaller particle size, the larger surface area, good dispersion and no pollution properties. Preparation and development of nano-TiO₂ has become a central issue of the material science and nanotechnology both here and abroad. This paper was studied the low-temperature hydrothermal (solvent-thermal ) under the micro-structure of nano-TiO₂, as well as its application in light irradiation degradation of organic pollutants, and analyzed the spectral properties of TiO₂ and photocatalytic mechanism.1 Nano-TiO₂ was prepared in the different solvents of H2O, NaOH, CH3CH2OH, OP emulsifier and diethanolamine. The effects of solvent and temperature on the microstructure of TiO₂ were investigated. Morevover, the degradation of organic dyes under ultraviolet light by nano-TiO₂ and the spectroscopy properties of nano-TiO₂ with various structures were analysed.2 TiO₂ particles were prepared under low temperature by solvothermal method. XRD, BET surface area and pore size analyzer and TEM were carried out to characterise TiO₂. The results showed that the cannular frame of TiO₂ was mainly anatase phase with the existence of brookite phase (121) and specific surface area was 106.2m2/g. The photocatalytic degradation of organic dye rhodamine B (RhB) and colorless small molecule 2,4-DCP under UV (λ≤387nm) were used as probe reactions to evaluate the photocatalytic activity of TiO₂. It was indicated that TiO₂ prepared under low temperature (50℃) showed good photocatalytic activity in the degradation of RhB and 2,4-DCP in view of the analysis of UV-visible spectroscopy, infrared spectroscopy (FTIR) and total organic carbon. In the TiO₂/UV system, the mineralized rates of RhB and 2,4-DCP were 81.2% (5h later) and 86.8% (7h later), respectively. The concentration of H2O₂ was determined using horseradish peroxidase (POD) and N, N-diethyl-p-phenylenediamine (DPD) spectrophotometry. The content of·OH was detected by fluorescence spectrophotometry of benzoic acid. The experiment indicated that photocatalytic degradation of TiO₂ mainly involved·OH mechanism.3 Brookite titania particles were prepared from a precursor of TiO₂ by hydrothermal method. The effects of the reaction temperature and the reaction time on the photocatalytic activity of the brookite titania were studied. The TiO₂ samples were characterized by XRD and TEM. Photocatalytic degradation of organic dye under UV light (λ≤387 nm) was used as the probe reaction to evaluate the properties of the optimum TiO₂. It was indicated that TiO₂ prepared under 150℃for 24h with the existence of brookite phase had a high photocatalytic activity. The discoloration and degradation of sulforhodamin B (SRB) were tracked, and the produced intermediate H2O₂ and·OH were determined during the photocatalytic experiments. It was indicated that photocatalytic degradation of brookite TiO₂ mainly involved the·OH mechanism. Brookite TiO₂ also exhibited the potential of application in photocatalysis.4 TiO₂@SiO₂ nanosphere powders were prepared using n-octylamine as a template by the sol-precipitation method. The effects of reaction acidity and calcination temperature on morphology, crystal and photoelectric properties of TiO₂@SiO₂ nanosphere powders were researched through XRD, TEM, electrochemical properties and photocatalytic degradation which used organic dyes as probe reaction. It was indicated that TiO₂@SiO₂ nanosphere powders prepared at the condition of reaction temperature 50℃, medium 1mol/L of HCl and calcination temperature 550℃were mostly anatase nanospheres with the highest dispersity and specific capacitance. The photocatalytic degradation properties of organic dyes and small molecules, the effect of mineralization and the mechanism of degradation were studied by Electron Spin Resonance (ESR), Spectrophotometry, IR and TOC. It was indicated that the photocatalytic effect of TiO₂@SiO₂ nanosphere powders were similar to that of business P25 and the photocatalytic process mainly involved·OH mechanism.5 Titania of different doping amounts was prepared by sol-gel method, which used tetrabutyl titanate, cerium nitrate and iodine as materials and were calcined at 450℃. XPS, XRD, TEM and thermal gravimetric analysis (TG) were carried out to characterise the optical properties of the catalysts. It was indicated that the band gap of doped-TiO₂ decreased from 3.03eV to 2.51eV and the size of it was 13nm. The doped-TiO₂ which was mainly anatase with iodine and Ce doped in the crystal lattice of TiO₂ had good thermal stability and TG was less than 2%. Nano-TiO₂ doped with iodine and cerium had been optimized in the degradation of RhB and the oxidizing species in photocatalytic reaction system was measured. It was found that the degradation rate of doped TiO₂ raised to six times under visible light, and photocatalytic mechanism referred to the hole oxidation.