The Fabrication And Application Of Composites Based On MoS₂ And MoSe₂

After the discovering of two dimensional graphene,transition metal dichalcogenides（TMD）have attracted growing interest and been intensively investigated in recent years because of their unique physical and mechanical properties.Inspired by the great achievement on the preparation and application of graphene-basaed composites,TMD has been also considered as potential building component for the fabrication of complex composites for achieving enhanced and even novel performance for a wide range of applications.Therefore,we systematically studied the preparation,application and theoretical analysis of a series of TMD composites in this academic dissertation.We successfully fabricated a fantastic photocatalyst via two-step hydro（solvo）-thermal method by compositing MoSe₂ on TiO₂.We introduced density functional theory to describe the synergistic effect between MoSe₂ and TiO₂,and its impact on the performance of photocatalysis.The electronic structure,band engineering,and charge re-distribution in this MoSe₂/TiO₂ heterostructure were calculated and analysed.We found the behavior of photogenerate electron-hole pairs in this structure could be optimized,corresponding photoluminescence characterization verified this conclusion.We employed the heterogeneous photocatalyst for the photodegration of organic dye and obtained excellent measured performance.We presented the experimental synthesis and theoretical investigation of MoS₂@SnO₂ heterostructure.Based on the MoS₂@SnO₂ heterostructure via hydrothermal method,we fabricated high-performance humidity sensor device.The first-principles calculations results revealed the water molecule adsorption mechanism between H₂O and sensing material.In the testing process,the measured response time and recovery time of MoS₂@SnO₂ heterostructure were 53 s and 21 s when switching humidity environment.The humidity sensing mechanisms were interpreted by characterization and calculation.We found he high specific surface and the low adsorption energy were the key factor.We fabricated a novel MoSe₂@MoS₂ heterostructure by compositing MoSe₂ on MoS₂ via two-step hydrothermal method.This composite can be used as catalyst for HER process during water splitting powered by electricity.We employed first-principle investigation to analyses the charge transfer and conductivity change.We found the optimized Gibbs free energy changed and the band structure of the composite structure contracted,and they were good to HER performance.According to HER measurements,we found the MoSe₂@MoS₂ heterostructure had enhanced output current density small Tafel slope,and long-term stability.We fabricate MoS₂-Co₃S₄ hybrid with hollow nanostructure via solvothermal synthesis as excellent electrode materials for application in the field of energy convert and store.As catalyst for electrochemical HER process,MoS₂-Co₃S₄ hybrid can split water into H₂ in a wide pH range with high activity and stability.As a lithium-ion battery anode,it is proven to achieve high reversible capacity(880 mA h g_-1 at 0.1 A g^-1 after 200 cycles)with excellent cycle performance.It exhibits a superior specific capacitance(1369 F g^-1 at 1 A g^-1)of and 83%capacity retention after 10,000 cycles when evaluated as an electrode for supercapacitors.Corresponding theoretical analysis indicated that MoS₂-Co₃S₄ hybrid had improved conductivity,increased active sites and optimized electrical structure.In this dissertation,we presented the fabrication and investigation of a series of TMD-based composites.We employed SEM,TEM,XRD,XPS techniques for structural and morphology characterization of prepared TMD-based composites.Combining performance characterization and theoretical elucidation,our work not only provides many promising candidates for typical application,but also provided fundamental understandings for the mechanism analysis in TMD based composites.