| The uncontrolled use of fossil fuels produces a large amount of carbon dioxide(CO2)gas,which causes a serious greenhouse effect and brings a series of harms to global environmental security.The semiconductor photocatalytic reduction of CO2 technology by simulating plant photosynthesis has great significance and broad application prospects in terms of CO2 emission reduction due to the advantages of green pollution-free,sustainable development and simple operation.Photocatalytic reduction of CO2 is essentially an oxidation-reduction reaction involving photogenerated electrons in the catalyst.Therefore,exploring and designing efficient photocatalytic materials is the focus of this technology.Metal sulfide has received extensive attention from many researchers due to its unique crystal form,excellent photoelectric properties and suitable redox ability.However,the single catalyst suffers from the disadvantages of weak light absorption,fast recombination of photogenerated carriers,and slower electron separation,which results in a big gap between the efficiency of light conversion CO2 and practical applications.In this thesis,metal sulfides are modified and modified by means of constructing heterojunctions,supporting carbon materials,introducing precious metals,promoters,etc.,so as to achieve high-efficiency photocatalytic activity.Using zinc nitrate and thiourea as raw materials,ZnS NSs catalyst was prepared by solvotheimal and calcination two-step technology,then ZnS/CdS photocatalyst was prepared by successive ionic layer adsorption and reaction method(SILAR),and finally the two-dimensional multi-interface contacted photocatalyst was prepared by hydrothermal method.Ternary ZnS/CdS/rGO composite photocatalyst.Passed X-ray diffractometer(XRD),X-ray photoelectron spectrometer(XPS),transmission electron microscope(TEM),ultraviolet visible diffuse reflectometer(UV-vis DRS),nitrogen adsorption and desorption instrument(BET),electrochemical test,etc.The prepared photocatalyst was tested for its physical and chemical properties,and its performance was tested by gas chromatography.The results show that the ternary photocatalytic material ZnS/CdS/rGO has strong sunlight absorption capacity and unique multielectron transport channels to increase the mobility of photogenerated carriers,thereby improving the efficiency of photocatalytic reduction of CO2.When the rGO loading is 3%,the ZnS/CdS/rGO composite photocatalyst exhibits the best photocatalytic activity,and the 4h CO yield reaches 38.77 μmol/g under UV-vis light.Using zinc sulfate,indium chloride and thioacetamide as raw materials,ZnIn2S4 microspheres are first prepared by hydrothermal method,then Au nanoparticles are anchored on the surface of the ZnIn2S4 catalyst by light deposition technology,and finally the continuous ion adsorption method(SILAR)is used.Prepare threedimensional ZnIn2S4/Au/CdS composite materials.The photocatalyst was characterized by TEM,UV-vis DRS,HRTEM,SEM,XRD,XPS and other test methods,and the efficiency of the catalyst in the conversion of CO2 under UV-vis light was tested by gas chromatography.The results show that when the Au loading is 1.5wt%,the ternary photocatalyst ZnIn2S4/Au/CdS has the best catalytic activity,and the CO yield is 252.28 μmol/g.This is because ZnIn2S4 and CdS construct a Typ Ⅱ heterostructure and the precious metal Au reduces disordered electron transfer and improves the electron separation rate and light absorption range.In addition,the prepared photocatalyst has good stability.The ZnIn2S4 microspheres prepared by the hydrothermal method were further loaded with NiS promoter by the co-deposition method.Through a series of characterizations,it is found that the promoter NiS reduces the activation energy of CO2 conversion on the semiconductor surface,promotes the separation and migration of photogenerated electron-hole pairs,and increases the active sites,thereby greatly improving the efficiency of photocatalytic reduction of CO2.The CO yield of 4h under UV-vis light was 58.5μmol/g. |
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