Synthesis And Photocatalytic Performance Of MoS₂ And Its Composites

In recent years,global energy and environmental issues have become more and more serious.The reason is that the depletion of fossil resources leads to an energy crisis,and the carbon dioxide,nitrogen oxides and sulfur oxygen compounds are generated with a large amount of consumption cause environmental degradation.In order to resolve these problems,we will use hydrogen energy as an alternative energy source and use natural energy to produce hydrogen from water.Among photocatalytic materials,semiconductor materials have been widely used due to their unique characteristics,and they are expected to play an important role in solving the above problems.When the size of the semiconductor is small,such particles are semiconductor clusters,and the photophysical properties of the clusters exhibit a quantum size effect.Due to its quantum size effect,when MoS₂ changes from bulk materials to nanomaterials,indirect bandgap semiconductors change to direct bandgap semiconductors.This paper mainly includes three aspects of research content:（1）In this paper,MoS₂ microspheres were prepared by hydrothermal method.The effects of different reaction conditions on the morphology of the samples were investigated.Under the conditions of reaction temperature 200℃,reaction time 24 h,pH=7 and solvent deionized water,2H-MoS₂ with size of 1μm were prepared.According to the photocatalytic degradation experiment,the degradation rate of Rhodamine B by MoS₂ after 150min irradiation reached 95%;after 180min irradiation,the degradation rate of methylene blue reached 98%.（2）MoS₂/Ti₃C₂ heterostructures with different Ti₃C₂ loadings were prepared by hydrothermal method.In the photocatalytic hydrogen evolution experiment,when the Ti₃C₂ loading is 30%,it has the highest specific surface area and excellent optical properties.The maximum photocatalytic hydrogen release rate of this sample is 6144.7 μmol·g^-1·h^-1,which are 2.3 times higher than that of the pure MoS₂,and has good photocatalytic cycle stability.The high conductivity of the Ti₃C₂ material effectively inhibits the recombination of photogenerated electrons and holes,and improves the photocatalytic activity of the MoS₂/Ti₃C₂ heterostructure.（3）The Au/MoS₂/Ti₃C₂ three-phase composite catalysts with different Au particle loadings were further successfully composited on the MoS₂/Ti₃C₂ heterostructure by the chemical method.Through a series of structural characterizations,it was found that the Au particles were uniformly distributed on the MoS₂/Ti₃C₂ heterostructure,and no agglomeration occurred.When the Au particle loading is 30%,the composite catalyst has the highest specific surface area and excellent optical properties.The photocatalytic hydrogen release rate of the sample is increased to 12000 μmol·g^-1·h^-1.Which are two times higher than those of MoS₂/Ti₃C₂ heterostructure,also have good photocatalytic cycle stability.First,MoS₂ absorbs photons and is excited to generate photogenerated electrons.The photogenerated electrons are transferred to Ti₃C₂ and the hydrogen ions are reduced to hydrogen on its surface.Second,Au particles are excited to generate excited electrons.The excited electrons are directly transferred to the MoS₂ conduction band under the Schottky barrier and electric field,and then H⁺ is reduced to generate hydrogen.