Preparation And Electrochemical Performance Of Nitrogen-doped Hierarchical Porous Carbon

The porous carbon material has a large specific surface area,good electrical conductivity,stable chemical properties,so which is widely used in supercapacitor electrode materials.However,the porous carbon material has low electric capacity just through the electric double layer capacitance.Therefore,the current research focus is to increase the specific capacitance of the carbon material.Heteroatomic doping has been distinguished among many methods to improve the performance of carbon materials,in which Nitrogen-doped has attracted the favor of researchers.While reducing the production cost,it is still a very challenging problem to obtain high capacitance,good multiplier performance and stable cycling performance.In this paper,two kinds of low-cost nitrogen-containing substances are used as nitrogen sources,and two kinds of excellent Nitrogen-doped porous carbon are prepared.The morphology of the as-made material was investigated by SEM and TEM.The micro structure and specific surface area of the as-made material were characterized by XRD,Raman spectroscopy,and N2 physical adsorption.The XPS was used to characterize the elemental distribution of as-made material.Finally,the electrochemical properties of the as-made material were tested by cyclic voltammetry,galvanostatic charge-discharge and alternating current impedance.The main results are summarized below:Nitrogen-doped activated carbon was prepared by composite precursor through carbonization and activation,in which ammonium polyphosphate as nitrogen source,phenolic resin as carbon source and polyurethane foam as supporting skeleton.The effect of ammonium polyphosphate consumption on the morphology,pore structure,nitrogen content and electrochemical performance of the as-made material were studied.The carbon material prepared by this method has a three-dimensional network structure,which is beneficial to the rapid transmission of electrons.At the same time,ammonium polyphosphate can effectively carry out nitrogen doping to carbon materials,improve the wettability and electrical conductivity of the material.Moreover,through the two steps of carbonization and activation,the mesoporous and microporous structures of the materials are formed,and the synergetic effect of me soporous-micropore coexist can significantly improve the capacitance of the material.The synergistic effect of meso-micropores can significantly improve the capacitance performance of the material.Electrochemical performance tests of this electrode material show that in a three-electrode system,the specific capacitance of the material can reach 327 F/g at a current density of 0.2 A/g,and after 8000 cycle test,specific capacitance remained 95.5%of the initial specific capacitance.The ANPC-4 was assembled into symmetrical capacitors,at a power density of 125 W/kg,the energy density can reach 5.83 Wh/kg,the capacitance retention rate was 94.5%after 10000 cycles.Finally,the mechanism of charge storage is analyzed by cyclic voltammetry.The above experiments were simplified and improved as follows:A polyurethane foam was used as support skeleton and nitrogen source,a phenolic resin was used as carbon source,KOH was the pore agent,and the nitrogen-doped porous carbon was prepared by facile one-step carbonization.The effect of KOH addition on the surface morphology,pore structure,nitrogen content and electrochemical performance of the material were investigated.This method can not only facilitate the preparation of nitrogen-doped porous carbon,but also has better performance.In a three-electrode system,the specific capacitance can reach as high as 377 F/g at a current density of 0.5 A/g,and the specific capacitance can still be maintained as 96.8%of the initial specific capacitance after 8000 cycles of testing;assembling a symmetrical capacitor with NPC-2,at a power density of 125 W/kg,the energy density can reach 6.05 Wh/kg.the cycle is repeated 10,000 times,the capacitance can be maintained at 96%.