Microwave Preparation Of Molybdenum Disulfide Composites And Their Photocatalytic Applications

Molybdenum disulfide(MoS₂)is a graphene-like layered semiconductor material.The layers are connected by weak van der Waals forces,and the layers are composed of covalent bonds of S-Mo-S three-atom layer structure.Its crystal structure has three types:1T,2H and 3R,among which 1T and 3R are metastable,and 2H is relatively stable under normal conditions.As a layered transition metal sulfide with multiple crystal structures,MoS₂ has a complex edge structure,high unsaturation and high reactivity.However,the band gap of the bulk MoS₂ is only 1.17 e V,and the band gap structure changes with the number of layers.The conduction band at the K point is an in-plane track,which is not affected by the interlayer coupling.Therefore,the band gap width of a single layer can reach 1.91 e V.Such a band gap width is very suitable for visible light absorption,and these characteristics make MoS₂ has a very broad application prospects in the fields of photoelectric conversion and catalysis.It is widely used as a catalyst for petroleum hydrodesulfurization,a catalyst for degrading pollutants,and hydrogen production by splitting water Catalyst.The active sites for a single-component MoS₂ catalyzed reaction are usually located at its edges,and these active sites are conducive to enhancing the adsorption and catalytic capabilities.Therefore,using a suitable preparation process can obtain MoS₂ and its composite photocatalyst with strong light trapping ability and excellent photocatalytic effect.In recent years,the abuse of antibacterial drugs represented by antibiotics has become a worldwide problem.These untreated medical sewage and its metabolites have caused serious threats to human life and the ecological environment.In order to solve this problem,photocatalysis as an environmentally friendly,non-toxic and harmless treatment technology has great application potential in the degradation of antibiotics.Although there have been a large number of reports about MoS₂ as a photocatalyst for degradation of antibiotics,due to the high degree of photogenerated electron-hole recombination and poor carrier transport ability of Mo S2,its photocatalytic performance is weak.In response to the above problems,this paper has carried out the following work1.The microwave hydrothermal method was used to efficiently prepare molybdenum disulfide nanosheets rich in sulfur defects.Experimental results show that molybdenum disulfide nanosheets rich in sulfur defects(DR-MoS₂)exhibit high adsorption capacity and a rapid adsorption rate for TC removal.Chara cterization and theoretical calculations by TEM,EPR,XPS,etc.show that microwave not only shortens the reaction time but also builds a large number of surface defects.These surface defects can be used as active sites to improve the adsorption capacity of MoS₂.In addition,the promotion of ammonium ion intercalation by microwaves leads to the expansion of the MoS₂ layer spacing,which enables organic molecules to enter the molecular layer,improves the adsorption capacity for organic molecules,and has good stability at the same time.2.Using liquid phase self-assembly strategy to modify ZnO quantum dots(ZnO QDs)on the surface of MoS₂ nanosheets as efficient adsorption and catalysts.Although the single-component MoS₂ has strong adsorption capacity,its photocatalytic ability is very poor.Therefore,we loaded ZnO QDs on the surface of MoS₂ to promote the carrier migration in the photocatalytic process and inhibit the recombination of photogenerated carriers to enhance the photocatalytic activity.P hotocatalysis experiments show that the composite material has excellent photocatalysis performance under ultraviolet light,and the removal rate of TC can reach 80%after 60min of ultraviolet light irradiation.TEM,PL,UV-Vis and other characterizations revealed that ZnO QDs modified on MoS₂ nanosheets have a unique structure,which can expose abundant active edges,improve the charge transport ability,and have good catalytic activity and stability for photocatalytic degradation of antibiotics.3.Depositing palladium particles on the surface of MoS₂ nanosheets to activate MoS₂ as a photocatalyst for high-efficiency degradation of tetracycline.The Schottky junction was constructed by loading palladium particles on MoS₂ by light deposition method.Due to the Schottky junction effect on the Pd/MoS₂ interface,the introduction of Pd not only promotes the interface electron transfer effect of excited catalysts,but also Pd NPs enhances the absorption capacity of visible light.The synergistic effect of the two promotes the photocatalytic degradation of TC..4.Using MoS₂ QDs to modify ZnO nanosheets,an efficient,cheap and stable0D/2D heterojunction photocatalyst was constructed.The introduction of Mo S ₂ QDs not only increased the surface active sites,but also effectively strengthened the charge transport capability and electron-hole pair separation efficiency of the composite material,thus improving the photocatalytic performance of MoS₂/ZnO.The MoS₂/ZnO nanocomposite exhibits excellent photocatalytic degradation of tetracycline and mercury-containing flue gas under ultraviolet light,so it has huge application potential.