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Photocatalytic Properties of Nonmetal Co-doped Nano-TiO2 Films

Author: YinXiaoLi
Tutor: YaoMingMing
School: Jinan University
Course: Physical and chemical
Keywords: TiO2 film Light performance Codoped Surface doping Visible light
CLC: TB383.2
Type: Master's thesis
Year: 2011
Downloads: 109
Quote: 0
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Abstract


Titania to become one of the most green catalyst development prospects because of cheap, non-toxic, high catalytic efficiency, good chemical stability. Titanium dioxide under UV excitation of photogenerated holes and photo-generated electron degradation of organic matter into the air trace CO 2 the H 2 O and other small molecules, thereby eliminating pollution. However, of TiO 2 In practical applications, there are some defects, such as its bandgap wider (Eg = 3.2eV), only in the incident light λ is less than 387.5nm of UV excitation under a valence band electron can transition to conduction band to the formation of photo-generated electrons and holes, so that the decomposition of organic matter, and ultraviolet light in natural light only 3% of 5 % is not high utilization of natural light. In addition, the photo-generated electrons and holes composite probability is very high, and how to reduce the recombination rate of electrons and holes, improve TiO 2 nanoparticles photocatalytic efficiency, improve TiO 2 photocatalyst key catalytic effect. In order to compensate for the TiO 2 above defects, improve its photocatalytic performance and broaden TiO 2 light absorption range, TiO 2 surface modification. Of this thesis is to take non-metallic ion codoped surface doping technical preparation of TiO2 film and its photocatalytic properties. Thesis research work includes the following aspects: (1) TiO 2 thin films and properties of this study using sol-gel technology and roasting process improved preparation of TiO2 films. Selected dyes acid fuchsin degradation of the target, were investigated non-metallic ion F-B 3 and S 2 - doped dye degradation, to seek the best doped Miscellaneous concentration. On this basis, research or FB-doped and FBS three doped on the degradation of the organic dye. The experimental results show that: in the ultraviolet or visible light irradiation, the nonmetal ions codoped photocatalytic activity than any individual ion doping, and three doped effect is more pronounced than the effect Mixed. Kinetic studies showed either non-metallic co-doped or doped TiO 2 , photocatalytic degradation reactions conform the Langmuir-hinshelwood first-order kinetics equation. (2) TiO 2 composite films characterization by X-ray diffraction analyzer (XRD), field emission scanning electron microscope (FE-SEM), fluorescence emission spectrum meter (PL), thermal gravimetric / differential thermal analysis ( DSC / TGA), nitrogen adsorption - desorption instrument (BET) characterization methods to explore the non-metallic codoped TiO , 2 surface structure and optical absorption behavior, the photocatalyst reaction mechanism and Co-doped response mechanisms. The results showed that the titanium dioxide film anatase, but contain small amounts of rutile and brookite phase when doped nonmetal ions codoped nonmetal ions especially after, rutile and brookite type reduced or even completely disappear; pure titanium dioxide thin film surface agglomeration serious alleviate the the ion doped film surface reunion phenomenon, relatively flat topography, relatively uniform particle size distribution, and mesoporous or microporous structure; doped titanium dioxide than pure titanium dioxide compared to the surface area increases, the pore size becomes small. (3) The mechanism of photocatalytic analysis nonmetal doping can significantly improve the photocatalytic activity, co-doped than single doped photocatalytic effect is more pronounced than double doped better co-doped photocatalytic effect of ion-doped system. The possible mechanism is: changing the structure or a defect status of the band gap of the titanium dioxide, doped generate more electrons and holes, and to reduce the recombination probability of the photogenerated electron and hole, and improve the photocatalytic effect. Modified titanium dioxide valence band as determined by the nonmetallic oxa, the conduction band is determined by Ti (3d), but the position of the conduction band is reduced, so that the forbidden band width significantly reduce nonmetallic doped hybrid can level closer to the valence band edge.

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