Studies On Preparation And Electrochemical Properties Of Chitin-based Nitrogen Doped Porous Carbon

Biomass has the advantages of wide source and renewable.It can be used as carbon materials in supercapacitors,batteries and catalysts.Chitin is the only abundant nitrogen-containing compound in nature.The nitrogen doped heterocarbon materials prepared by chitin have broad prospects in the application of supercapacitors.Direct carbonization of chitin can lead to the problems of limited specific surface area,single pore structure and low nitrogen content of carbon materials.In order to change the morphology of the precursor of carbon electrode,nitrogen doped porous carbon nanomaterials were prepared based on former formed chitin nanogels.Furthermore,the supercapacitors with excellent performance were prepared by introducing nitrogen source and activator,and their electrochemical properties were studied.This paper provides a new idea and method for the preparation of nitrogen-doped porous carbon materials by using chitin.The main contents are as follows:1)Chitin nanogels was constructed from bottom to top by stirring the chitin solution dissolved in NaOH/urea system at high speed.After freezing and drying,chitin nano aerogels were obtained.Nitrogen-doped microporous carbon nanoparticles were synthesized by direct carbonization in argon atmosphere at 800-900?.SEM,TEM,BET,XRD and XPS were used to characterize the morphology,porosity,crystal structure and element composition of the nanoparticles.The electrochemical properties of nitrogen-doped microporous carbon nanoparticles prepared at different temperatures were studied.The results show that the carbon materials(CNC-800)burned at 800?have excellent electrochemical properties.Under the current density of 0.5 A/g,the specific capacitance of the two-electrode in aqueous phase(1 M H₂SO₄)is 185F/g and that of the organic system(1 M TEABF4-AN)is 108 F/g.The assembled capacitors have high energy density(23.4 Wh/kg)and good cycle stability(95%capacitance retention after 10000 charge-discharge cycles).2)With the urea as the nitrogen source and sodium hydroxide as the activator,the higher specific surface area and nitrogen doped microporous/mesoporous activated carbon were prepared by one step carbonization and activation method.The related characterization and electrochemical tests were carried out.The positive effects of activation and additional nitrogen doping on the capacitance properties of the materials were discussed.The results show that NaOH activation and N doping from urea effectively increase the specific surface area(2631m²/g),porosity and nitrogen content(7.1%)of the carbon material(ACNC-800),resulting in high electrochemical performance.Under the current density of 0.5 A/g,the specific capacitance of the two-electrode in aqueous phase(1 M H2SO4)is 227 F/g and that of the organic system(1 M TEABF4-AN)is 136 F/g.The assembled capacitors have high energy density(29.4 Wh/kg)and good cycle stability(98%capacitance retention after 10000 charge-discharge cycles).