Synthesis And Photocatalytic Performance Research Of Tin Disulfide-based Heterojunction Materials

Photocatalytic technology,as a multi-disciplinary emerging research field of semiconductor physics,materials science,photoelectrochemistry,catalytic chemistry and environmental science,has shown great application potential in energy conversion and environmental restoration.Metal sulfides,as semiconductor materials with many similarities to metal oxides,have shown catalytic potential in both solar energy conversion and photo-degradation of pollutants due to their suitable light response range.The efficiency of the photocatalytic reaction mainly depends on the separation of electrons and holes,the migration rate of photogenerated carriers to the catalyst surface,and the rate of the catalytic reaction that is captured by the reactive species.However,single semiconductor materials often have problems such as low quantum efficiency,poor selective adsorption performance,and easy photoelectron-hole recombination,which limit the practical application of semiconductor materials in large quantities.In view of the above problems,a new type of heterojunction material is designed and developed in this paper.Starts with improving carrier utilization efficiency and optimizing energy level structure,improving catalytic performance in practical reactions by forming heterojunction catalysts.The content of the thesis will be elaborated from the following two aspects:1.Select a base material with a suitable light response range and a stable structure to generate a controllable component on the base material to form a heterojunction catalyst.Through the dynamic control of the tunable components,a new type of charge transfer path of the system is established,thereby effectively improving the photocatalytic activity and efficiency of the heterojunction catalyst.2.The metal sulfide catalyst is annealed to form an auto-oxidized heterojunction.Through the adjustment of the annealing time,the selective oxidation of the crystal plane is realized.This unique heterojunction structure accelerates the separation of electrons and holes while adjusting the band structure,thereby improving the photocatalytic performance of the sample.The work consists of the following four parts:The paper first briefly introduces the basic principles and development history of photocatalytic technology,and summarized the current common catalyst development strategies.The advantages and common classifications of heterojunction semiconductor catalysts are introduced,and the disulfide-tin compounds selected as base materials in this paper are systematically introduced and analyzed.The work begins with the phase control of heterogeneous catalysts with polymorphic compounds.Pure phase tin disulfide nanosheets were synthesized by hydrothermal method,and a unique polymorphic copper sulfide-tin disulfide（Cu_xS@SnS₂）heterojunction catalytic material was synthesized by further hydrothermal reaction.The formation process of polymorphic copper sulfide was studied using various characterization methods,and a reasonable reaction mechanism was given.At the same time,a series of high-performance Cu_xS@SnS₂photocatalysts were synthesized by dynamically adjusting the proportion of polymorphic copper sulfide compounds（CuS-Cu₂S）by changing the amount of precursor divalent copper ions.The experimental results show that the heterojunction catalyst exhibits excellent photocatalytic activity for the degradation of the pollutant tetracycline hydrochloride（TC）under visible light.The performance is mainly derived from the strong charge brought by the reasonable ratio of two polymorphic copper sulfides Separation and optimization of energy level structure.Secondly,SnS₂@SnO₂heterojunction catalysts and pure phase SnO₂materials were synthesized by annealing under oxygen-depleted conditions.By adjusting the annealing time,it was found for the first time that under certain oxygen atmosphere and annealing time,SnO₂nanoparticles were selectively formed on the side of tin disulfide nanosheet.Studies have shown that such a structure is more conducive to the transfer of electrons,thereby effectively expanding the separation of electrons and holes.At the same time,the energy level structure of the two materials inhibits the recombination of photo-generated carriers.The experimental results show that when the amount of SnO₂formed on the side of SnS₂reaches the optimal value,the separation rate of photogenerated carriers is the largest,and the sample shows the best photocatalytic performance.Finally,all the research results of the thesis are summarized,and the development of semiconductor photocatalytic technology is prospected on this basis.