| With the development of industrialization, exhaustion of fossil fuel and all kinds of pollution have emerged. Air and water pollution have begun to affect our lives seriously. Since 1972, Fujishima and Honda first discovered TiO2 electrode may decompose water under UV irradiation; photocatalytic semiconductor technology has aroused extensive attention since it is rational utilization of renewable energy. Titania nanomaterials, because of its stability, security, non-toxic and high photocatalytic properties, were widely recognized as the best photocatalytic material. However, the band gap of titanium dioxide confines its use of solar energy. Only ultraviolet light can be absorbed which is less than 5% of solar energy. The photocatalytic quantum efficiency of TiO2 is poor, which restrict the development of TiO2.In this paper, the photoresponse range and photogenerated charge separation of TiO2 were developed by means of microstructure modulation (including hierarchical structure and crystal facet regulation), surface loading and modification. Surrounding the direction, our mainly works are listed below:(1) We use tetrabutyl titanate and titanium dioxide particles as titanium source, synthesize titanium dioxide nanoparticles, nanosheets and nanotubes through the sol-gel method and hydrothermal method, respectively. TNTs exhibited best photocatalytic performance. Titania nanotubes entangled and formed many pore structures. Titania nanotubes got a much higher specific surface area than other TiO2, were able to enhance the adsorption of dye-molecules. Compared with titania nanotube, titania nanosheets shows better hydrophilic, easy to form a stable colloid in aqueous solution.(2) Graphene oxide was prepared by using Hummers method from graphite powders. G-TiO2 composites and G-TNTs composites with different weight addition ratios of graphene were preparded by sol-gel process and hydrothermal treatment respectively. Graphene oxide contains a mass of functional groups on its surface. These functional groups contributed to the nucleation of TiO2 and promoted TiO2 attaching to the graphene skeleton. We observed that TiO2 materials were resoundingly stuck to the abaxial and adaxial surface and the edges of grapheme sheets, homogeneously. Photocatalytic experiments showed that the addtion of graphene material could significantly improve the catalytic efficiency of titanium dioxide. The composites combined with 3wt.% graphene exhibited the best photocatalytic performance. Catalytic efficiency of G-TiO2 is 4.5 times that of pure TiO2 nanoparticles. Catalytic efficiency of G-TNTs is 2.5 times higher that of pure TNTs. It was found that the graphene could inhibit agglomeration of titanium dioxide material, increasing the specific surface area of material and improving the carrier mobility of the material. It is a very effective approach to increasing titanium dioxide nano material catalytic efficiency.(3) We use APTMS as a silane coupling agent to modify the surface of titanium dioxide material, APTMS/(TNS-Au) and APTMS/(TNTs-Au) with visible response were successful synthesized by the strong electrostatic adsorption properties between Au nanoparticles and-NH hydrogen on APTMS surface. Different from depositing Au particles by photochemical reduction, more Au nanoparticles could homogeneously deposite on the surface of titanium dioxide modified by APTMS.The composites showed high catalytic efficiency and stability in the irradiation of visible light. FDTD simulation showed the surface electric field distribution under irradiation of visible light, which confirmed that gold particles are the centre of surface plasmon resonance.Under the irradiation of visible light, Au NPs absorb resonant photons and produce hot electrons via SPR excitation. The hot electrons are quickly injected into the conduction band (CB) of TNTs through the interaction between Au NPs and TNTs which induce photocatalysis activity. Titanium dioxide composite with Au nanoparticles can expand the spectral response from ultraviolet to visible range, enabling the efficient use of solar energy.(4) G/(TNTs-Au) composites were successfully prepared using a one-pot method. The addition of graphene can reduce the radiative electron-hole recombination. It found that the original structure of TNTs-Au composite and the quantity of gold nanoparticles were not changed after the addtion of graphene. The visible light catalytic efficiency of G (TNTs/Au) is 1.5 times than that of TNTs-Au. Graphene, titanium dioxide and gold particles these three materials cooperate to improve the efficiency of the catalytic composite under the irradiation of visible light. It provides some new directions to further expanding the material response in visible light, incerased the efficiency of the catalytic material. |
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