Study On The Preparation And Catalytic Performance Of TiO₂ And Its Composites With Different Morphologies

The problem of energy shortage and environmental pollution that affect the sustainable development of human society has become more and more serious,so it is the only way to achieve sustainable development to deal with the problem of energy and environment.Photocatalysis technology can be combined with solar energy to achieve energy conversion,converting solar energy into usable chemical energy,such as photolysis of water to produce hydrogen,CO₂ reduction,N₂ conversion,and degradation of organic pollutants,especially in the treatment of organic pollutants,photocatalysis has an absolute advantage compared with other methods such as physical adsorption,chemical sedimentation,and biological bacteriophage.Because it can almost completely convert organic pollutants into water and carbon dioxide without causing secondary pollution,it has become a hot spot in current research.In this paper,we start with the preparation,morphology control and composite of materials:first,TiO₂ precursor sol containing Ti³⁺was prepared by oxidation of TiH₂with hydrogen peroxide,and then Ti³⁺self doped TiO₂ with different morphology was prepared by solvent heat treatment in organic solvents with different polarity.Second,using the reducibility of glucose and sodium selenite as selenium source,the composite products of Se and Ti³⁺self doped TiO₂ were prepared,and their photocatalytic properties were studied.Third,Ti³⁺doped TiO₂ was prepared by using TiCl₃ as titanium source,and then compounded with g-C₃N₄ to prepare TiO₂/g-C₃N₄ composite materials,and the photocatalytic degradation of wastewater from different chemical plants was studied.The main research contents of the paper are as follows:Preparation and catalytic performance of Ti³⁺self doped TiO₂ with different morphology:Ti³⁺precursor was obtained by oxidation of TiH₂ with green environmental protection H₂O₂.Different organic solvents were selected as reaction medium for solvothermal reaction.The different polarity of solvents made the crystal surface of anatase TiO₂ grow in different directions,and Ti³⁺self doped TiO₂ with different morphology was prepared.The products were characterized by X-ray diffraction?XRD?,transmission electron microscopy?TEM?,high resolution transmission electron microscopy?HRTEM?,X-ray photoelectron spectroscopy?XPS?,UV-Vis diffuse reflectance spectroscopy?UV-Vis DRS?.The results show that due to the different polarity of the solvent,the crystal surface of TiO₂ grows in different directions,and Ti³⁺self doped TiO₂ with different morphology is prepared.When triethanolamine is used as solvent,the sample has a large specific surface area,which makes the material have the best photocatalytic performance.The band gap width is an important factor to determine the efficiency of light absorption,and the particle size and morphology are important factors to affect the adsorption and photocatalytic degradation of pollutant molecules on the surface.Preparation and catalytic performance of Se/Ti³⁺doped TiO₂ composite:first,TiH₂ from low valent Ti source was partially oxidized to obtain Ti³⁺containing precursor,then Na₂SeO₃ as selenium source and glucose as reductant were mixed with sol for hydrothermal treatment.Selenium and Ti³⁺self doping Se@TiO₂ composite material was prepared.The samples were characterized by XRD,TEM,HRTEM,XPS,UV-Vis DRS,TPC and EIS.The results show that the hydrothermal method can effectively avoid the sublimation of selenium and improve the compound content of selenium in the compound.By controlling the amount of Na₂SeO₃,not only the proportion of selenium in the complex can be controlled,but also the morphology of the product can be greatly affected.The content and morphology of Se particles are closely related to the catalytic properties of the materials.According to Z-type electron and hole separation mechanism,the photocatalytic degradation of RHB was carried out by Ti³⁺self doped TiO₂ composite with se,which greatly improved the efficiency of carrier separation,so the composite had good visible photocatalytic performance.Preparation and catalytic performance of Ti³⁺self-doped TiO₂ and g-C₃N₄composite materials:two-step high-temperature calcination combined with acid treatment was used to obtain graphene-like g-C₃N₄ nanosheet structures with high yield.The Ti³⁺self-doped TiO₂/g-C₃N₄ heterostructure was prepared by thermal stirring reflux-hydrothermal crystallization method,using low-cost TiCl₃ as Ti source and nitrogen as protective gas.The samples were characterized by XRD,TEM,HRTEM,XPS,UV-Vis DRS,BET and so on.The results show that the formation of TiO₂/g-C₃N₄ heterojunction can rapidly separate the photogenerated electrons and holes at the interface of the heterojunction and transfer them to the surface of the catalyst,thus enhancing the stability and photocatalytic performance of the material.When the mass ratio of TiO₂ to g-C₃N₄ is 1:2,the sample has the best photocatalytic performance,which is due to the formation of good heterojunction interface structure.The results of practical wastewater treatment show that the wastewater containing single phenol is easy to be degraded by photocatalysis,while the wastewater with complex components and high salt content is difficult to be degraded by photocatalysis,which provides certain evidence for the application of photocatalysis in environmental treatment.