Design And Preparation Of Metal Oxide-based Composite Catalysts And Study On Their Photocatalytic Performance

In order to solve the aquatic ecological environment crisis and meet the demand for clean energy,the purification of water environmental pollutants and the development of renewable fuels are a major challenge facing mankind.Photocatalysis using inexhaustible sunlight and semiconductor has proven to be a sustainable way for effectively degrading pollutants and hydrogen energy supply.The generation,dissociation and separation of carriers is an important element that affects the efficiency of photocatalysis.Among the many control methods,combining multiple semiconductors is the most important control method to increase the density of carriers and active molecules on the catalyst surface.Therefore,this project aims to construct a series of semiconductor composite photocatalyts.Through the“solvothermal method”,“in-situ growth method”and“solid phase synthesis method”and other methods to combine metal oxides and band matching semiconductors to prepare efficient and stable composite catalyst.Finally use them to treat water antibiotics,phenolic pollutants and photolysis of water to produce hydrogen,alleviating ecological and energy crises.At the same time,the adsorption and photocatalytic processes of various monomers and composite photocatalysts for pollutants were studied,and the internal relationship between the structural characteristics of the prepared photocatalysts and their adsorption performance,catalytic performance and stability was explored.In order to provide theoretical support for the preparation of high-performance composite photocatalyst,the path and mechanism of catalytic process were clarified.The specific contents and innovations of this project are as follows:（1）Ti₃₂-oxo-cluster,Cd S nanoparticles and Cd S/Ti₃₂-oxo-cluster composite photocatalysts were prepared by in-situ precipitation and ultrasonic method to degrade tetracycline hydrochloride.The experimental results show that all series of Cd S/Ti₃₂-oxo-cluster composite materials show significantly enhanced photocatalytic performance and photostability,and the degradation rate of 96.3%can be achieved in 60 minutes with the optimal composite.The enhanced photocatalytic activity due to the extended response to the visible region,the increased reaction sites and the effective separation of photogenerated carrier pairs.At the same time,Ti³⁺,·O₂^-and h⁺have been proved to play an important role in photocatalytic degradation.In addition,the intermediates in the degradation process of Cd S/Ti₃₂-oxo-cluster system were identified,and the corresponding photocatalytic degradation pathway and mechanism were discussed.（2）Zn In₂S₄ nanosheets were uniformly compounded on the six sides of In₂O₃ by low-temperature hydrothermal method and efficient 3D/2D In₂O₃/Zn In₂S₄ catalyst was synthesized.The optimized 3D/2D Zn In₂S₄/In₂O₃ photocatalyst showed wonderful degradation efficiency for 2,4-dichlorophenol,which was1.85,2.60,3.02 and 3.54 times higher than 3D/0D In₂O₃/Zn In₂S₄,monomer Zn In₂S₄ nanosheets,Zn In₂S₄nanoparticles and In₂O₃,respectively.The improvement of performance was mainly due to the establishment of type II heterojunction.In addition,it is confirmed that·O₂^-and h⁺are the main active substances,and the degradation mechanism of 2,4-DCP was discussed in detail.（3）In₂O₃ hollow cube/g-C₃N₄ nanosheets heterojunction photocatalyst was synthesized by bubble template method and hydrothermal method,which was used for photocatalytic H₂ production.The excellent compact binary heterostructure can increase the contact area between the components,improve the photoinduced electrons and holes concentration,and help delay the recombination of carriers.The results show that the In₂O₃/g-C₃N₄ heterojunction has remarkable photocatalytic performance,that is,the hydrogen production rate reaches 3.342μmolg^-1h^-1,which is 41 and 82 times higher than that of the monomer In₂O₃ and g-C₃N₄,respectively.At the same time,the relationship between the photocatalytic activity and the structure of In₂O₃/g-C₃N₄ composite was discussed by a series of characterization techniques,and the catalytic mechanism was clarified.