Design,preparation And Photocatalytic Performance Of Indium-based Sulfide Composite Catalysts

In-based sulfides(ZnIn₂S₄,MnIn₂S₄,and In₂S₃,etc.)benefit from their excellent chemical stability,adjustable optical properties,suitable band gap,and unique photoelectric properties.Similarly,its high activity in heavy metal ion photoreduction,organic photosynthesis,photodegradation of organic pollutants,and photocatalytic hydrogen evolution has received widespread attention in the field of photocatalysis.This thesis focuses on the soft chemical methods to prepared indium-based sulfide composites photocatalysts and study the photocatalytic performance.Moreover,aim at the energy band of indium-based sulfide,designing a band structure with a Z-scheme electron transport mechanism,and then on this basis construct a composite catalyst with high visible light activity and photostability.In this work,a variety of characterization methods are used to systematically study the crystal phase structure,microscopic morphology,chemical composition,photoresponse,photocatalytic performance,and possible mechanism of the synthesized photocatalyst.The research contents are as follows:1.Solvothermal-assisted synthesis of WO₃/In₂S₃ Z-scheme heterojunction catalysts for photocatalytic reduction of Cr(VI)The two-step hydrothermal/solvothermal method was used to prepared composite photocatalysts with 0D WO₃ nanoparticles coupled with 3D In₂S₃ microspheres.Observed and analyzed the microscopic morphology,phase structure,optical properties,surface chemical composition,band gap structure,and carrier separation characteristics of materials through a series of characterization.The results of catalytic reduction of Cr(VI)under visible light showed that the photocatalytic activity of the composite system is higher than that of a single component.The rate constant of Cr(VI)reduction at the optimal compound ratio achieved 0.0812 min^-1,which is 67.7 and 3.6 times higher than the rate constants of WO₃(0.0012 min^-1)and In₂S₃(0.0225 min^-1),respectively.XPS and XRD proved that the catalytic system has good photostability.Combining the ESR test in the photocatalytic process,the photocatalytic mechanism of the composite system with the Z-scheme carrier migration in the photocatalytic process was explored.2.In-situ synthesis of Z-scheme?-MnO₂@MnIn₂S₄ nano-heterojunction catalysts for photocatalytic reductionThe MnCO₃ nanocubes as templates,MnIn₂S₄ nanosheets were in-situ grown on the surface of?-MnO₂ nanocubes through ion etching and solvothermal methods,and a series of?-MnO₂@MnIn₂S₄ composite photocatalytic systems were successfully prepared.Combining XRD,SEM,TEM,XPS,and other methods,the morphology,phase and surface elemental composition of the prepared materials were characterized,and the concept of nano-define junction was put forward through further HRTEM.The photocatalytic reduction of Cr(VI)and 4-nitroaniline experiments proved that the composite materials showed improved photocatalytic activity,and the optimal ratio of the composite system reduced 99.6%of 4-nitroaniline and 94%Cr(VI)in 90 min and 60 min,respectively.Through active species capture experiment and ESR,the possible Z-scheme photocatalytic electron transfer mechanism was explored.Cycling experiments also verified the excellent stability of the composite photocatalytic system under the Z-mechanism.3.Construction of 0D/2D CeO₂/ZnIn₂S₄ Z-scheme heterojunction photocatalysts for photocatalytic hydrogen evolution researchA series of 0D/2D CeO₂/ZnIn₂S₄ composite photocatalysts with different composition ratios were prepared by the hydrothermal and hydrolysis co-precipitation method.The morphology of the sample was observed by electron microscope(SEM and TEM),and its special 0D loaded 2D"chess-chessboard"structure was confirmed.Ultraviolet-visible diffuse reflectance spectroscopy(UV-vis DRS)and electrochemical tests are used to determine the energy band structure of the materials.The photocatalytic activity of the catalyst was evaluated by photocatalytic water splitting to hydrogen evolution.The results show that the composite catalytic system(CZIS-10)has the highest hydrogen evolution efficiency(847.42?mol g^-1 h^-1)when loaded with 10wt%CeO₂ nanoparticles,which is 6.7and 2.4 times that of a single CeO₂ and ZnIn₂S₄.The cycle experiment and the phase and morphology tests after the experiment proved the photostability of the composite photocatalyst.Combining the morphology,energy band structure,and photocatalytic performance of the material,a photocatalytic mechanism with a Z-scheme electron transport mechanism is proposed to improved photocatalytic performance.4.Oxygen vacancy-mediated Z-scheme TiO_2-x@ZnIn₂S₄ heterojunction catalysts for photocatalytic degradation of antibioticsA Z-scheme TiO_2-x@ZnIn₂S₄ heterojunction was prepared by the hydrothermal method.The morphological structure and optical properties of the prepared catalysts were extensively characterized.Experimental results show that the TiO₂-x with rich surface oxygen vacancies benefits the formation of local defect energy levels between the conduction band and the valence band,which can be advantageous to expand the light absorption range.The absorption band edge of TiO_2-x@ZnIn₂S₄was extended from 421 nm to 503 nm compared to pristine TiO_2-x and the interfacial charge transfer was highly accelerated to enhance the photo-reactivity of TiO_2-x@ZnIn₂S₄.Likewise,the TiO_2-x@ZnIn₂S₄ showed 12.4-fold and7.70-fold higher photocatalytic performance compared to pristine TiO_2-x and ZnIn₂S₄towards the degradation of tetracycline hydrochloride(TCH)and nitrofurantoin(NFT)in real water matrix and solution water.Furthermore,the photo-decomposition pathway of NFT was proposed by HPLC-MS,and the Z-scheme electron transfer mechanism in TiO_2-x@ZnIn₂S₄ heterojunction was proposed and discussed in detail.