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Study on Synthesis of Titania Nanofilms Via in Situ Chemical Oxidation and Their Photocatalytic Degradation Performance

Author: WuYaHui
Tutor: CaiWeiMin
School: Harbin Institute of Technology
Course: Environmental Science and Engineering
Keywords: TiO2 thin film and Photocatalytic Degradation In situ chemical oxidation Surface Modification Urea Tungsten -doped
CLC: X70
Type: PhD thesis
Year: 2011
Downloads: 240
Quote: 0
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Abstract


The use of renewable energy, such as solar, water pollution and air pollution has been a rapid development in the past decades, the the photocatalytic technique is the most safe and environmentally friendly way. The photocatalytic purification technology is the core of the photocatalytic materials, the TiO 2 nano-thin film is a low-cost, safe, non-toxic, good stability and easy recovery of photocatalytic materials, environmental pollution control has very broad application prospects. As we all know, the nanofilm morphologies its important impact on a variety of performance and application; prepared with certain morphology of nano TiO 2 film can effectively improve its photocatalytic properties. In this paper, in-situ chemical oxidation on titanium surface in situ generated a different structure and morphology of TiO 2 nano-film and thin film characterization and photocatalytic degradation of performance. Around the above content, mainly in the following aspects: (1) the use of a mixture of sodium hydroxide and hydrogen peroxide oxidation liquid reaction with the metal titanium plate in a 80 ° C water autoclave for 24 hours, and then after pickling and heat treatment, Preparation of a low-dimensional structure of the titanium-based TiO 2 nanowire network-like film. The process of the formation of the network structure of the nanowires: the titanium sheet portion is dissolved in an oxidizing solution to form sodium titanate sol - deposition process gradually grow nanowires titanate sodium salt is formed by dissolving, and then through the pickling heat treatment eventually formed of TiO 2 nanowire network-like structure. Photocatalytic Degradation solution to test the nanowire film photocatalytic performance results show that this TiO 2 nanowire network-like film showed good photocatalytic degradation of performance and good stability childhood phenol degradation rate reached 75.9%. The network-like structure of the film and the anatase crystalline form is the main reason for its good photocatalytic properties. (2) oxidation with hydrogen peroxide solution directly reacted with the titanium plate and titanium base were prepared by further water heat treatment of TiO 2 nano-flower-shaped film. The amorphous TiO 2 nano flower-like structure, the hydrothermal treatment is formed on the titanium substrate in the oxidation reaction process, makes the amorphous of TiO 2 crystallization and the formation of anatase / Rutile mixed crystal phase. The photocatalytic activity of photocatalytic degradation of methyl orange test sample, the results show that compared with the directly calcined samples without hydrothermal reaction, hydrothermal reaction TiO 2 thin film photocatalytic activity by two times. The hydrothermal reaction temperature and time on the film properties, the results show that to raise the temperature of the hydrothermal reaction or extension of the hydrothermal reaction time can improve the degree of crystallinity of the film, thereby improving the photocatalytic efficiency of the film. On this basis, with urea as raw material, by a calcination pyrolysis method for surface modification of TiO 2 nanoflowers film. The study found the the modified film under different calcination temperature, the band gap has reduced to varying degrees. Film for photocatalytic degradation of methyl orange, the results show that both visible light or full spectrum light, modified TiO 2 nanoflowers film photocatalytic degradation properties have been improved . The which the 350 ℃ modified TiO 2 film showed visible activity under visible light 3 hours methyl orange degradation rate reached 72.8%, DRS tests show that the band gap width down to 2.4 eV. XPS analysis of the results showed that the modified TiO 2 film visible photocatalytic activity can be attributed to the pyrolysis of urea in the amine polymer is formed by the film surface sensitization effect. (3) in the hydrogen peroxide solution was added varying amounts of the peroxy tungstic acid sol was added thereto, and then the titanium sheet in situ chemical oxidation reaction to prepare a one-dimensional tungsten doped TiO 2 thin film. The prepared nano TiO 2 film was nanoflowers nano-network or nanopore-like structure. Sol added in an amount different from the tungsten content of the film is different, tungsten element doped into the Ti-OW bond formed TiO 2 lattice. Ti-OW bond is formed through the deposition of the condensation in the reaction system of the peroxotitanic acid and peroxy tungstic acid. DRS test the the doped tungsten film TiO 2 absorption edge redshift, were less than band gap of 3.1 eV. Doped modified film photocatalytic degradation of methyl orange test its photocatalytic performance results show that the doped tungsten film photocatalytic degradation of performance is far superior to the pure TiO 2 films under visible light 3 hours degradation of methyl orange highest rate reached 19.3%, the full spectrum of radiation three hours after, under optimal conditions doped sample degradation rate of methyl orange reached 91.3%, the photocatalytic degradation rate is 4.3 times the undoped sample.

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