Preparation And Electrical Properties Of PVP/MF-based Nitrogen-containing Carbon Nanofiber Electrode Materials

In this paper,nitrogen-enriched carbon(NC)was obtained by carbonization of polyvinylpyrrolidone(PVP)containing nitrogen-and oxygen atoms and melamine formaldedyde resin(MF)with the high concentration of nitrogen.NC-U and NC-K were prepared by adding urea and KOH activation method,respectively.The preparation of electrodes and assembly of supercapacitors were finished through the coating process.Meanwhile nitrogen-enriched carbon fiber(NCF)with self-supporting structure was prepared by the electrospinning of PVP/MF mixing aqueous solution and carbonization,and it was assembled into supercapacitor by clamping piece method directly.All samples were characterized by SEM,Raman,TGA,XPS and nitrogen adsorption/desorption.The electrochemical behaviors of samples and supercapacitor electrodes was studied by CV,EIS,galvanostatic charge/discharge test.The influence of microstructure,nitrogen contents and types,specific surface area,pore structure and the conductivity on the electrochemical performances was studied.The results show NC-U and NC-K prepared with the methods of mixing urea and KOH activation presents honeycomb porous structure with higher porosity compared to NC.Although NC-K has the high specific surface area(1086.29m2/g),its specific capacitance is very low because of its lower nitrogen concentration(4.85 at.%).Theurea treatment not only introduces the reactive nitrogen atoms into NC-U but also improves its specific area and conductivity,which is beneficial to electrochemical performances.NC-U50 has the highest Cpe of 148.5 F/g at scanning rate of lmV/s due to the highest nitrogen concentration of 13.15 at.%and SBETof 244.67m2/g-1 and the high concentration of N-6 and N-5.NC-U50 and its supercapacitor show excellent comprehensive performances.Nitrogen-riched carbon nanofiber films present 3D flexible self-supporting structure with 100 to 300nm fibers overlapping each other.The structure,composition and electrochemical properties of NCF was greatly impacted by the ratio of PVP solution and MF solution and carbonization temperature.NCF-650 prepared by the PVP/MF solution ratio of 1:2,carbonization temperature of 650? has the highest Cpe of 202.5F/g at scanning rate of ImV/s.Compared to AC with high specific surface area,NCF-650 has higher Cpe due to the active nitrogen atoms of 6.13 at.%,compared to NC-650,NCF-650 has higher specific surface area of 173.9 m2/g than NC-650 which is beneficial to the energy storage.And NCF-650 with 3D fiber film structure has lower impedance.There is only 8.2%decay in specific capacitance of the supercapacitor with NCF-650 ad the negative eletrode over 1000 cycles,indicating the excellent electrochemical performances.Nitrogen-enriched carbon nanofiber film is the ideal electrode materials for supercapacitor.