Fabrication Process And Functional Application Of Carbon-based Nanofibers

Carbon nanofibers（CNFs）have high specific surface area,good electrical conductivity,corrosion resistance,and certain chemical activity on the surface.They can be used as conductive materials and coating materials in the field of electrocatalytic hydrogen evolution.Therefore,in this paper,when the humidity is <50%,the voltage is 60.0 kV,the diameter of the liquid supply device is 0.6 mm,and the distance between the liquid supply device and the receiving plate is 25 cm,the electrospinning is performed.Then,the pre-oxidation-stabilization-carbonization stage is performed in a tube furnace.Finally,non-metal and transition metal carbide-CNFs electrocatalytic materials were obtained.The main research contents are as follows:1.g-C₃N₄ nanosheets are used as nitrogen source,PAN is used as carbon source and spinning reagent.A series of g-C₃N₄/CNFs non-metallic carbon nanofibers were synthesized by controlling the carbonization temperature and the material-liquid ratio.Then,its morphology,structure,and electrocatalytic performance were characterized to evaluate the HER performance of the material.It was found that the higher the carbonization temperature,the better HER of the material.When the material-liquid ratio is 0.50%（w/V）g-C₃N₄ the performance of the sample is the best,because it has the highest degree of graphitization and specific surface area,has a pyridine-N,pyrrole-N structure,and the smallest charge transfer resistance It can provide chemically active sites and faster charge transfer rate for HER to improve catalytic hydrogen evolution performance.At a current density of 10 m A/cm²,the overpotentials of 0.50% g-C₃N₄ CNFs in acidic and alkaline electrolytes were 206 mV and 307 mV,and the Taf slope values were 106.2 and 232.6 mV/dec,respectively.Therefore,the Volmer reaction is the speed determining step.And the catalyst has good catalytic stability in acidic and alkaline electrolytes.2.Sodium molybdate is selected as the molybdenum source.Polymers with PAN: Polyvinylpyrrolidone（PVP）= 5: 5 are used as spinning reagent and provide a carbon source.Synthetic carbon nanofibers are coated with molybdenum carbide materials to form smaller molybdenum carbide particles（about 20 nm）.And the carbon material is used to increase the conductivity and corrosion resistance of the material to obtain carbon-based nanofibers with lower overpotential.Based on the conditions of heat treatment temperature and material-liquid ratio,sample has better HER performance when the carbonization temperature is 800 °C and the material-liquid ratio is 4%.The overpotentials in acidic and alkaline electrolytes are respectively 288 mV and 267 mV（current density is 10 m A/cm²）.3.Sodium molybdate,ammonium molybdate and ammonium phosphomolybdate were selected as molybdenum sources,and polymer with PAN: PVP = 5: 5 as spinning reagent and provide carbon source.When ammonium phosphomolybdate is used as the molybdenum source,the N,P co-doped molybdenum carbide/carbon nanofiber（N,P-Mo₂C/CNF₂）sample has the best HER effect.According to the analysis and test results,it can be known that the N and P elements can provide nucleation centers for Mo₂C particles and form finer Mo₂C nanoparticles（about 10 nm）.N and P doping can change the energy density of electrons,which is beneficial to the performance of electrocatalytic hydrogen evolution.In alkaline electrolyte,N,P-Mo₂C/CNF₂ has a low overpotential（107 mV,current density = 10 mA/cm²）,a small Tafel slope,and a high exchange current density,and has good HER activity and stability.