Ultrathin Metal Sulfides:Controllable Fabrication In High-pressure Solvothermal System And Properties

With the rapid development of graphene,the ultra-thin structure metal sulfides have been extensively studied for their unique physical and chemical properties.For example,this ultra-high surface state can significantly enhance the occurrence of surface electrochemical reactions,which expected to be an ideal class ofelectrochemical energy storage materials for these ultra-thin metal sulfides.Therefore,various methods of preparing ultrathin metal sulfides have also been reported in an endless stream.Among these methods,the hydrothermal/solvent thermal method has become a very important preparation method because of its simple operation,easy availability of raw materials,various morphological regulation and low cost.The factors that affect the hydrothermal/solvent thermal process include reaction time,reaction temperature,reaction pressure,additives such as surfactants,pH of the reaction system,and concentrated reaction precursors of the reaction materials.Most of the parameters have been studied in detail.However,the pressure,an important thermodynamic parameter affecting hydrothermal/solvent thermal reaction,is often neglected,whcih leads to related research is rarely reported.It is well known that applying a certain pressure can change the activation energy and reaction barrier of the entire reaction system,change the adsorption state of the surface adsorbent on a specific surface,effectively change the thickness of the ion diffusion layer,and form the crystal nucleus and crystal growth of the material.The process has a certain impact.In the preparation of ultra-thin metal sulfides,dimensionally controlled growth can be expected by pressure-regulating the adsorption state of molecules on specific crystal faces.Based on the above theory,on the basis of the high-pressure solvothermal reaction which was developed by our laboratory,we choose the preparation of ultra-thin metal sulfides as the main research object.The influence of pressure on the formation process of atomic layer structure is discussed plenty.The energy storage characteristics were also studied.The main contents of this article are as follows:1.High-pressure solvothermal synthesis of ultra-long atomic layer ?-In2S3 nanobelts and the study of lithium electric energy storage properties.The ultra-long(>50 um)P-InS3 nanobelts with atomic layer(~1 nm)structure were successfully prepared by high-pressure solvothermal method.The orientation-attached growth mechanism under pressure indicates the ultra-long nanobelts,process of growth.Moreover,we have extended this method to other reaction systems for preparing ?-In2S3 nanobelts,indicating that the high pressure method has certain universality.When it is combined with rGO,the combination ofthese two atomic levels can not only increase the active sites,but also enhance the surface oxidation-reduction reaction,and shorten the ion transport path and increase the charge transfer rate.The negative electrode material of the lithium ion battery prepared based on this exhibits good discharge specific capacity,cycle stability,and high rate characteristics.For example,the discharge capacity of 801 mA hg-1 can be maintained after 60 cycles at the current density of 100 mAg-1,and the reversible capacity remains at 587 mA h g-1 after 150 cycles at the current density of 500 mA g-1.2.High-pressure solvothermal method synthesis the 1T-MoS2 nanosheet.In this solvothermal system,the growth of the[002]crystal orientation of MoS2 nanosheets was successfully inhibited with the introduction of high pressure.We prepared the IT-MoS2 nanosheets and IT-MoS2/rGO composites.Among the composites,the single layer of IT-MoS2 accounts for more than 60%of the entire sample.Afte combing with graphene,the IT-MoS2 can not only effectively inhibit agglomeration,but also significantly improve the conductivity of the sample.What is more importantly,the single-layer structure can fully expose the electrochemical reactive sites of MoS2,which improve the diffusion ability of ions in the electrode and shorten the diffusion path.The combination of the metallic MoS2 and graphene canfurther improve the charge transport efficiency of the electrode material.When used as a negative electrode material for a lithium ion battery,the composite electrode exhibits good reversible discharge specific capacity,cycle stability,and high rate characteristics.For example,the reversible discharge specific capacity of 100 cycles can still maintain about 1000 mAh g-1 at the current density of 1000mA g-1.In addition,the composite electrode also has good hydrogen evolution properties,including low overpotential,low Tafel slope,and good cycle stability for electrocatalytic hydrogen evolution.3 High-pressure solvothermal method synthesis the large size and high crystallinity SnS2 nanosheetsWith the help of high-pressure solventthermal experimental apparatus,we successfully synthesized the large size and high crystallinity SnS2 nanosheets whose the length of 10-20um.The high-pressure improved the attachment growth which decide the synthesis of large size and high crystallinity SnS2 nanosheets.The high-quality thin-layer single crystal has laid a solid foundation for the further development of high-performance photodetector parts.