Preparation Of Nitrogen-doped Porous Carbon Materials And Properties Of Supercapacitors

Electrode material is a key factor affecting the performance of supercapacitors.Nitrogen doping in porous carbon structure can improve the wettability,change the electronic structure and provide additional charge storage capacity.In this paper,three nitrogen-doped porous carbon materials are prepared and their performance as electrode materials is investigated,aiming to find a simple and green method to prepare carbon materials with suitable morphological structures and use them in the research and development of supercapacitors.The main research contents include the following three aspects:1)Nitrogen-doped ordered mesoporous carbon spheres were prepared using phenol-formaldehyde resin spheres as the core and melamine as the nitrogen source.Using a one-step aqueous solution method,melamine-formaldehyde was formed into melamine-formaldehyde resin（MF）coating by polycondensation reaction.Nitrogen-doped ordered mesoporous carbon spheres（NMCS）were obtained after pyrolysis at 800℃in N₂atmosphere.In order to obtain carbon spheres with controllable structure and excellent electrochemical performance,the effects of polymerization temperature on the structure,morphology and electrochemical properties of the carbon materials were investigated.The results show that when the polymerization temperature is 60℃,the synthesized nitrogen-doped ordered mesoporous carbon spheres have the largest specific surface area(578 m²·g^-1)and excellent electrochemical performance.The specific capacitance(1 A·g^-1 current density in 6 M KOH,the specific capacitance of NMCS-1 is 240 F·g^-1)and the cycle stability（82.9%of the original specific capacitance after 10000 cycles）prove that the material can be applied to the electrode material of supercapacitors.2)Based on the work 1,nitrogen-doped hollow mesoporous carbon nanospheres（NHCS）were prepared using a self-template sacrificial strategy with melamine-formaldehyde resin spheres as the core and 2,6-diaminopyridine（DAP）as the nitrogen source.By a facile and rapid method,ammonium persulfate（APS）catalyzed the rapid polymerization of DAP on the surface of MF spheres into colloidal nanospheres under the protection of polymeric surfactant（PVP）.The poly-DAP（PDAP）shell was encapsulated on the surface of MF spheres and the MF spheres decomposed and the PDAP shell form carbon to form NHCS after pyrolysis at 800℃in N₂.To achieve the optimal electrochemical properties of NHCS,the effects of the amount of DAP on the structure and electrochemical properties of NHCS were investigated.It was observed by scanning electron microscopy and transmission electron microscopy that the NHCS obtained with different DAP additions had different dispersions,but all had large cavity structures.The specific capacitance(270 F·g^-1 at 1 A·g^-1)and cycling stability（92.3%of the original specific capacitance after performing 10000 cycles）in 6 M KOH demonstrate that NHCS-2 can be used as a supercapacitor electrode material.3)Based on the work 2,we changed to use dopamine（DA）as the carbon and nitrogen sources and added tetraethyl orthosilicate（TEOS）to form a silicon dioxide（Si O₂）coating,which was etched with hydrofluoric acid to obtain nitrogen-doped mesoporous bowl carbon（NPCB）.The effects of factors such as the amount of dopamine and Si O₂ coating on the morphology,structure and electrochemical properties of the carbon materials were systematically investigated.The results show that the excess of dopamine leads to self-polymerization in the reaction process,while the Si O₂ coating can improve the dispersion of NPCB.The specific capacitance(240 F·g^-1 at 1 A·g^-1)and cycling stability（small decay of specific capacitance at 10000 cycles,which is 91.2%of the original specific capacitance）in 6 M KOH demonstrate that NPCB-2 can be used as supercapacitor electrode material.