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    Improved preparation method of catalyst and development of nano-scale TiO2 material

    • Last Update: 2021-06-19
    • Source: Internet
    • Author: User
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    At present, improving the photocatalytic activity of semiconductors, especially improving their use of solar energy, is a worldwide issue
    .


    In order to solve this problem, researchers have started research from the following three aspects


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    1 Improved catalyst preparation method

    Studies have shown that the catalytic activity of TiO 2 is related to the particle size and crystal structure of the catalyst.
    When it has a mixed crystal structure and a small particle size, the catalytic effect is better.
    The preparation method has a greater influence on the crystal structure and particle size of TiO 2 and affects the catalyst.
    Follow-up processing
    .


    By changing the operating conditions of the preparation method, a catalyst with better performance can be obtained


    For example, the gas phase method is to oxidize TiCl 4 at a high temperature to prepare TiO 2.
    Studies have shown that in a high temperature tubular aerosol reactor, TiCl 4 gas phase oxidation is used to prepare nano TiO 2.
    It is found that the particle size of TiO 2 increases with the extension of the residence time The reaction temperature increases, and the content of rutile TiO 2 increases with the extension of the residence time and the increase of the reaction temperature.
    When the reaction temperature reaches 1300°C, the content of rutile TiO 2 appears to the maximum
    .


    Thus at 1300 ℃, vapor phase method having a rapid formation of anatase, rutile crystalline form mixed Ti02 2 Nanocrystalline TiO2 advantages, prepared therefrom having higher activity


    For the liquid phase method to prepare TiO 2 , whether it is a hydrolysis method using TiCl 4 as a raw material, a hydrolysis method using a titanium alkoxide as a raw material, or a sol-gel method (Sol-gel), the wet sol is generally obtained ( Or gel), and then dried and calcined to obtain a sample
    .


    The main disadvantage of the traditional drying method is that due to the formation of the gas-liquid interface in the gel pores, the surface tension causes the gel to shrink significantly during the drying process, destroys the spatial network structure of the gel, and finally causes the gel skeleton to collapse and the particle size grows.


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    2.
    5.
    3 Development of nano-scale TiO 2 materials

    The quantum efficiency of ordinary powder semiconductor photocatalysts is not high, but the research on nanomaterials that has emerged since the 1990s has shown that nanomaterials have changed in terms of optical properties and catalytic properties
    .


    The time for photogenerated electrons and holes to diffuse from the phase body to the surface of the catalyst to undergo oxidation-reduction reaction is related to the particle size.


    From the perspective of energy band theory, the energy level of the semiconductor valence band represents the limit of the oxidation potential of the semiconductor hole.
    Any substance with an oxidation potential above the semiconductor valence band position can in principle be oxidized by the photo-generated holes; similarly, any reduction Substances with a potential below the conduction band of the semiconductor can in principle be reduced by photogenerated electrons
    .


    TiO 2 is an n-type semiconductor material.


    The newly developed nanotube TiO 2 material is an important inorganic functional material.
    Compared with other forms of TiO 2 , it has a larger specific surface area, especially in the tube can be further loaded with smaller inorganic, organic, and metal Or the self-assembly of magnetic nano-ions into composite nano-materials will greatly improve the photoelectric, opto-magnetic and photocatalytic properties of TiO 2
    .


    Many researchers have devoted themselves to the basic aspects of the preparation and application of TiO 2 nanotubes


    Porous materials can be divided into 3 categories according to their pore diameter:

    ①Materials with a pore diameter less than 2nm are microporous materials, mainly including wollastonite, activated carbon, zeolites, zeolite molecular sieves, etc.
    ;

    ②Materials with a pore diameter greater than 50nm are macroporous materials, including porous glass, porous ceramics, aerogel, cement, etc.
    ;

    ③Materials with a pore diameter of 2-50nm are mesoporous materials, mainly including aerosols, layered clays, silicon-based and non-silicon-based mesoporous materials
    .

    Mesoporous materials belong to the category of nanomaterials
    .


    Compared with common nano-TiO 2 materials, mesoporous TiO 2 materials not only have larger pore size, specific surface area and pore volume, but also have regular pore channels and adjustable pore size, and their macroscopic morphology can be adjusted as required, such as membranes and fibers.


     

     

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