The Studies On Preparation And Photocatalytic Properties Of Cadmium Sulfide Based Semiconductor Composites

As a cheap and feasible technology,solar powered semiconductor photocatalysis has a great prospect in solving environmental and energy problems.Because of the narrow band gap of single photocatalytic semiconductor material,solar energy can not be used efficiently.The rapid recombination of electron hole pairs in a single semiconductor material reduces the catalytic performance of the photocatalyst.In this paper,a series of Cd S based composites were prepared by combining semiconductors to form heterojunction and changing the band gap,morphology and crystal shape of the photocatalyst.The problems of narrow absorption edge and rapid recombination of electron hole pairs of a single semiconductor material were overcome,and the performance of the photocatalyst was greatly improved.The photoelectric and photocatalytic properties of Cd S matrix composites were analyzed by various characterization methods.The main research content and innovation results of this paper are as follows:（1）Solvothermal synthesis of Cd S/Mo S₂ composites with spherical and flake loads.The composites were characterized by XRD,SEM,UV-vis DRS and photoelectrochemistry.It was found by UV-vis that the higher the molar ratio of Cd S,the stronger the light absorption performance.The composite has higher photocurrent density,lower resistance value and better photocatalytic performance of H₂O₂ production than single semiconductor under the irradiation of sunlight simulation.The optimum photocatalytic H₂O₂ production efficiency of 1.5CM composite is 12.48 m M.g^-1.h^-1.Cyclic experiments show that the material has good stability.（2）Cd S/r GO composite photocatalysts were synthesized using benzyl alcohol as solvent and water as solvent,respectively.CG@C ternary photocatalyst was prepared by adding glucose to synthesize CG with benzyl alcohol as solvent.The experimental results show that the photocatalytic properties and photocatalytic activities of CG composites synthesized with benzyl alcohol as solvent are better than those of WCG synthesized with water as solvent.The photocatalytic properties and photocatalytic activities of CG composites synthesized by thermal synthesis of CG@C samples after the addition of glucose are further improved than those of CG photocatalysts without carbon composite.The photocatalytic experiment results showed that CG@C can produce H₂O₂ under visible light at a rate of 23.70 m M.g^-1.h^-1,and can rapidly degrade tetracycline and Rhodamine B,with degradation rates of 60.26%and 45.93%within10 min.Cyclic experiments show that the material has good stability.（3）Graphene was often employed as electron mediator between semiconductors in the heterogeneous materials to improve electron transfer and therefore enhance photocatalytic performance.Little reported synthesis method can guarantee the deposition of two different semiconductors directly on graphene.In this work,an emulsion-solvothermal method employing graphene oxide（GO）as surfactant was proposed to prepare Cd S/reduced graphene oxide（r GO）/Zn S composites for accomplishing the direct contact of Cd S and Zn S with r GO.The optimal composite CG0.5Z prepared via.emulsion-solvothermal method can produce H₂O₂with the remarkable efficiency of 24.93 m M.g^-1.h^-1 under visible light,and rapidly decompose tetracycline and Rh B with the removal rate of 80.3%and 87.4%,respectively,after only 10 min irradiation,exhibiting superior photocatalytic activity to the material prepared via.conventional method.CG0.5Z also exhibited out-standing photocatalytic ability under real sunlight irradiation.The recycling experiments proved the excellent stability of the obtained ternary composite.The photoluminescence measurements,the time-resolved photoluminescence decay curves and Mott-Schottky plots further confirmed the more efficient electron-hole spatial separation and transfer in composite prepared through emulsion-solvothermal route,proving the emulsion-solvothermal synthesis is a better way to construct the r GO bridge between semiconductors.The possible degradation reaction pathways were also deduced based on the detected intermediate products.