The Study On Preparation And Performance Of Fluorine Intercalation N,F Co-doped Carbon Materials In A Space-Confined System

In recent years,in the fields of electrocatalytic hydrogen evolution reaction?HER?and lithium ion batteries,N-doped carbon materials have been widely concerned by researchers due to their excellent electrochemical stability and safety.However,the nitrogen-doped carbon materials prepared under the traditional open system still face many problems,including low reversible capacity of lithium batteries and poor electrochemical activity.For many years,researchers have usually optimized and modified precious metals by loading them with nitrogen-doped carbon materials.However,this type of method is not only costly but has little effect.Therefore,the modification of N-doped carbon materials with appropriate preparation methods has important practical significance for the development and application of HER and lithium batteries.In this paper,using natural vermiculite as the template and urea as the intercalating agent,the fluorine intercalated nitrogen-fluorine co-doped carbon material was obtained with the aid of a limited space synthesis system.At the same time,through the HER and lithium battery charge and discharge performance test to examine its electrochemical performance.The details are as follows:The urea hot-intercalated vermiculite composite material is used as a precursor,and annealed at a high temperature of 550 ? in an air atmosphere,so that the urea molecule undergoes thermal polycondensation in the two-dimensional limited space unique to vermiculite,which is created by the vermiculite laminate structure.The confined space reaction environment has changed the polymerization reaction process of urea molecules in the conventional open system and achieved the purpose of controlling the product morphology and size and phase composition.Through the hydrofluoric acid etching process,the fluorine intercalated carbon nitride nanocomposites were obtained.The characterization results show that the introduction of the confined space synthesis system not only modified the morphology and structure of the material,but also changed the internal bonding method and structure.Spatial arrangement enhances electrical conductivity.HER test results show that the material has a hydrogen evolution overpotential of 200 mV at a current density of 10 mA/cm²,and its activity is superior to other carbon nitride materials.?2?Using 750 ? thermally expanded vermiculite as the intercalation body and urea as the intercalation agent,the urea intercalation vermiculite precursor material was carbonized at a high temperature of 750 ? under an inert atmosphere.After the template etching process,fluorine intercalated nitrogen and fluorine were obtained.Doped with carbon material,the resulting material was activated at high temperature with KOH as an activator,and a porous N,F co-doped carbon-based material was successfully prepared.Characterization by means of N₂ adsorption and desorption curves,the results show that: fluorine is successfully embedded between graphitized carbon structure layers,and a higher intercalation content is obtained,and the effective introduction of nitrogen and fluorine makes more crystals in the material Defect sites.These defect sites can increase the number of reactive sites during the electrochemical reaction,improve the network structure,and increase the efficiency of electron transfer.In addition,the amorphous carbon layer structure of the material makes it have a higher electrochemical stability during the charging and discharging of lithium batteries and promotes the material's reversible capacity to continue to climb.It shows that the reversible capacity can reach 2102 mAh·g^-1after 400 cycles of 0.1 A/g current density charge and discharge.In addition,the overpotential of the material at 10 mA/cm² is 147 mV,and the initial potential is 81 mV.The HER performance is significantly better than traditional nitrogen-doped carbon materials.