Research Of Defect Controlling About N-x Two Elements Doped TiO₂

The preparation method and crystal defects can influence the crystal structure, which determine the properties of crystal.It has no break through that the traditional solid state and liquid state were the main methods which were used to synthesize TiO2; In applied field, nano TiO2can be only activated under UV light irradiation of wavelength less than387nm (about8%of Solar Energy) because of its wide band gap (Eg=3.2eV), so the light utilization efficiency to solar irradiation is very low. At the same time, the recombination of the photogenerated electrons and holes occur quickly, resulting in low light quantum efficiency.According to the above problems, this paper constructed Gas-Liquid (L-g) interface, which not only has advantages of gas phase scattered, but also has the advantage of simple post-processing. Hydrolysis occurs between water molecules dispersed at a gaseous state and liquid Tetra-n-butyl Titanate at gas-liquid interface. Different elements doping and morphology TiO2were synthesized by the vapor transport method of water molecules, and all Factors contribution in preparing process and forming mechanism were discussed.The multiplex defect was characterized by XPS, XRD, ESR and PL. Based on these characterization, we investigated the thermal catalytic and the photo catalytic properties of the doped TiO2nanocomposites, realized the assessment of the effect of the multiplex defect to the crystal material properties.The followings are the main research work and results:(1) Orthogonal experiment was designed to discuss the effects of various factors such as Flowing rate, Deionized Water Temperature and Stirring rate. The optimum technical situations:Flowing rate was200L/h, Stirring rate350r·min-1and Deionized Water Temperature was25℃were obtained. Mechanism of agglomeration controlling and how to prevent nanoparticles agglomeration was discussed in this paper.(2) C-N co-doped TiO2nanorods were synthesized by the vapor transport method, with rotating and ball milling. The samples were characterized by X-Ray Diffraction and X-ray photoelectron spectroscopy analysis. The scanning electron microscope images showed that as-prepared TiO2powders were nanorods, formed by the stacking of nanoparticles with a uniform size of about50nm. The degradation of methylene blue demonstrated that doping C and N could increase the photocatalytic activity of TiO2under visible light.(3) C-N co-doped TiO2nanoparticles were synthesized by the vapor transport method, using urea as the carbon and nitrogen sources. The entire preparation doesn’t need any acid or alkali to control the pH value of the system. The samples were characterized by X-Ray Diffraction, Transmission electron microscope and X-ray photoelectron spectroscopy. Results showed that as-prepared samples were well dispersed pure TiO2and C-N co-doped TiO2nanoparticles with an approximate diameter of10-30nm. Degradation rate of methyl blue proved double elements doping could efficiently improve the photocatalytic activity of TiO2. The reason was studied by photoluminescence spectra and ultraviolet-visible spectroscopy, which suggested that C, N co-doping could narrow the band gap of TiO2and increase the visible-light absorption. In addition, C, N co-doping could create more oxygen vacancies, which could inhibit the recombination of electrons and holes and improve the photocatalytic activity of C-N co-doped TiO2. Among all of the samples, C-N co-doped TiO2calcined at400℃presented the highest catalytic efficiency.(4) N-Sn co-doped TiO2nanoparticles were synthesized by the vapor transport methods. The samples were characterized by X-Ray Diffraction, Transmission electron microscope and X-ray photoelectron spectroscopy. Results showed that nanoparticles were dispersive and homogeneous. Sample whose doping amount is1%calcined at400℃about2h had the best photocatalytic activity, and this was consistent with thermocatalysis results. Photocatalytic and thermocatalysis have the consistency with each other mainly because of crystal composition and defects caused by doping.The paper completed the preparation of the TiO2nanocomposites, discussed the nanorod molding mechanism, elements doping, defects forming and photocatalysis and thermocatalysis. The work provides a reference to the research of properties and defects in functional nanomaterials.