Study On Preparation And Photocatalytic Performance Of TiO₂ Nanosheets And Its Composite Materials

Due to its controllable electronic structure,high chemical stability,non-toxicity and low cost,titanium dioxide nanomaterials are considered to be a photocatalyst for solar-fuel conversion.However,the shortcomings of TiO₂ photocatalysts,such as the high recombination rate of photogenerated electron-hole pairs and the narrow response range to sunlight,limit its application in photolysis of water to produce hydrogen.Regarding the above problems,this thesis starts from adjusting the surface and interface structure of TiO₂ catalyst,energy band structure,and constructing the heterostructure between semiconductor and TiO₂,using hydrothermal method,solvothermal method,solid phase sintering,deposition-precipitation and other methods.The TiO₂photocatalyst was modified to obtain anatase-type TiO₂ nanosheet material with a high exposure ratio(001)crystal face,TiO₂/MoS₂ layered heterojunction composite material,and TiO₂/g-C₃N₄ nano-block composite material.The morphology and structure of the prepared materials were characterized by XRD,SEM,and TEM,and the optical and photocatalytic performance data of the samples were obtained by using photoelectric response,TR-PL,UV-vis,photoluminescence,Mott Schottky and hydrogen production tests.1.Using solvothermal method to prepare(001)surface TiO₂ nanosheet structure with exposure ratio up to 98.5%,it performs well in UV-visible light degradation of rhodamine B.After 2.5 hours of radiation,nearly 99%of Rh B is degraded,which is better than commercial P25 More effective.And this large surface structure provides a guarantee for the subsequent loading of Pt nanoparticles with good dispersibility.We also explored the effect of Pt loading on the photocatalytic properties.The hydrogen production photocatalytic rate of Pt/TiO₂ catalyst gradually increases with the increase of Pt content.The highest hydrogen production rate of TiO₂ nanosheets can reach2.234mmol h^-1g^-1.2.The TiO₂/MoS₂ layered composite heterojunction structure material prepared by hydrothermal method,under visible light irradiation,the photocatalytic hydrogen production rate of TiO₂/MoS₂ nanolayer is 1858?mol h^-1g^-1,which is lighter than pure TiO₂ nanosheets.The catalytic hydrogen production rate of 45?mol h^-1g^-1 is nearly 41times higher.At the same time,the preparation of TiO₂/MoS₂ composite material with heterojunction also showed high stability.Under the reaction conditions of 4 cycles for10 hours,the photocatalytic hydrogen production rate remained basically stable.The heterojunction formed by the recombination of this large-area surface and interface increases the electron-hole separation rate and further improves the photocatalytic activity.3.The hydrothermal method and solid phase sintering method are used to prepare TiO₂/g-C₃N₄ nano-blocks with uniform size and a heterojunction structure formed by large-scale surface and interface.The TiO₂/g-C₃N₄ composite obtained by optimizing the loading of g-C₃N₄ in the catalyst has a high photocatalytic hydrogen generation rate.The pure TiO₂ nanosheets show a hydrogen generation rate of 0.045 mmol g^-1h^-1.After directional compounding with g-C₃N₄,when the weight percentage of g-C₃N₄ is 20%,TiO₂/g-C₃N₄ nano-block composite the photocatalytic hydrogen generation rate of high-performance hydrogen is 1.854 mmolg^-1h^-1,which is significantly better than pure TiO₂.It can maintain a relatively stable photocatalytic activity after 10 hours of cyclic reaction,and the hydrogen production rate of the TiO₂/g-C₃N₄-2 composite is basically unchanged.The core-shell layered structure,the appropriate loading of g-C₃N₄ and the synergistic effect of surface and interface heterojunction show the high photocatalytic activity of TiO₂/g-C₃N₄ nanomaterials.This article has 48 figures,5 tables,and 190 references.