Synthesis And Electrochemical Performance Of Transition Metal Dichalcogenides And Heterostructures

In recent years,the two-dimensional?2D?transition metal dichalcogenides?MX₂?and heterostructures have received extensive attention due to the adjustable energy band structure,novel physical and chemical properties,and broad application prospects in the fields of electronic and optoelectronic devices and energy.The targeted fabrication of high-quality,thin-layer 2D MX₂ and heterostructures with a specific sequence is an important prerequisite for the exploration of the basic physical and chemical properties and application.The chemical vapor deposition?CVD?method is considered to be the preparation method that is most likely to achieve this goal while taking into account both growth efficiency and growth cost.At present,this method has been widely used in the controllable growth of MX₂ and heterostructures,which have comparable crystal quality to the samples obtained by mechanical exfoliation.According to previous reports,metallic VS₂ with good conductivity,large interlayer spacing,and high theoretical specific capacity,has been widely used in energy storage fields such as lithium ion batteries?LIBs?and sodium ion batteries,but there is still a lack of intuitive observation of VS₂'s dynamic energy storage mechanism.Now,most of the VS₂ nanosheets?NS?are synthesized by hydrothermal methods,which have the disadvantages of poor crystal quality,easy stacking,and poor cycle rate performance of the formed electrode,which hinder the improvement of electrochemical performance and the intuitive exploration of internally dynamic energy storage mechanism.In addition,Pt Se₂-based heterostructures?e.g.,Pt Se₂/Mo Se₂,Pt Se₂/Si nanowires,and Pt Se₂/Ga As?exhibit strong interfacial coupling effect and ultrafast carrier transfer,and show good application prospects in the fields of electronic and optoelectronic devices.However,at present,the basic physical and electronic/photoelectric properties of heterostructures composed of graphene?Gr?and Pt Se₂ are only studied via theoretical calculations,and the controllable synthesis of the Gr/Pt Se₂ heterostructure is the prerequisite for relevant experimental exploration.The above problems provide the basis for the research of this paper.The specific contents of this paper are as follows:?1?Electrochemical Performance and Mechanism of VS₂@CNT as Anode Materials for High-Performance Lithium-Ion BatteriesWe have synthesized highly crystalline,thin-layer VS₂ NS on a carbon nanotube film?CNT?substrate by using a APCVD method;the excellent electrochemical performance of VS₂ NS@CNT composite material was explored as a anode electrode for LIBs?it delivers a high reversible capacity of?850 m A/h g at a current density of0.2 A/g,Even at a high current density of 10 A/g,its specific capacity retains at 697m Ah/g?;The microstructural changes and internal energy storage mechanism of VS₂NS@CNT composite material during charge and discharge process are intuitively revealed via the in situ SEM/TEM characterization;This work provides an important reference for the design of high-performance anode materials and the study of energy storage mechanism.?2?Intercalation-Mediated Synthesis and Interfacial Coupling Effect Exploration of Unconventional Gr/Pt Se₂ Vertical HeterostructuresWe have synthesized Gr/Pt Se₂ vertical heterostructure on Au foils through a two-step APCVD route;We utilized the 2D confined space between the Gr film grown in the first step and the Au foil substrate to control the layer thickness of Pt Se₂ in the second growth step,and further explored the effect of growth temperature and growth time on the layer thickness and coverage of Pt Se₂;The stacking sequence and interfacial coupling effect of Gr/Pt Se₂ heterostructures are revealed by using high-resolution scanning tunneling microscopy/spectroscopy?STM/STS?characterization;Our work should hereby enable significant advances in the synthesis of 2D-based vertical heterostructures and in the exploration of their intrinsic interface properties.