Preparation Of Heteroatom-doped Carbon Materials And Their Electrochemical Performance For Supercapacitors Electrode Materials

Due to their relatively abundant raw materials,economic feasibility,adjustable surface chemistry,easy processing,large specific surface area,high chemical stability,fast transfer kinetics and wide operating tempera-ture range,carbon materials have been studied extensively.Although most carbon materials have a high specific surface area,their electrical conduc-tivity generally decreases with increasing porosity and specific surface area,which greatly limits the specific capacity.How to design reasonable pore structure and surface doping modification of carbon materials is the key problem of the research.This thesis mainly focuses on the purpose of im-proving the electrochemical performance of carbon materials,selecting or-ganic ligands as carbon sources,through the coordination with low boiling point zinc salt and alkali activation method to drill holes and etching,het-eroatom（B,P,N）doping/co-doping to modify the surface,which are in order to obtain carbon materials with excellent electrochemical perfor-mance.The application of various carbon materials in the electrochemical properties of supercapacitors was mainly studied,and the physical proper-ties of carbon materials,such as structure,morphology and component el-ements,were studied by means of SEM,TEM,XRD,Raman,XPS and BET.The results are as follows:（1）2-（4-hydroxybenzene）imidazo[4,5-f]-[1,10]phenanthroline（named CO）was selected as carbon source to investigate the effects of car-bonization temperature,doping of P or B atoms in different proportions,pore-forming of zinc salts and activation of KOH on the electrochemical properties of carbon materials.The optimal carbonization temperature was700℃,and the molar ratio of potassium dihydrogen phosphate to ligand CO was 1:1.The best electrochemical performance of porous carbon ma-terial P₁-COPCN-700 was determined.Based on the symmetrical superca-pacitor of P₁-COPCN-700,at a current density of 0.5 A/g,the specific ca-pacitance of a single electrode and the specific capacitance of the entire device are 280.5 F/g and 70.1 F/g,respectively.And it exhibits a high ma-terial level energy density of 14.0 Wh/Kg at 300.0 W/Kg.（2）Using 4’-（4-phosphonylphenyl）-3,2’:6’,3”-terpyridine（named CP）as carbon source,the effects of carbonization temperature,different pro-portion of B,P or N atom doping,zinc salt pore-forming and KOH activa-tion on the electrochemical properties of carbon materials were investi-gated.It was determined that the optimal carbonization temperature was700℃,and the molar ratio of boric acid to ligand CP was 5:1.The porous carbon material B₅-CPPCN-700 had the best electrochemical performance.For the three-electrode system,when the current density is 0.5 A/g,the specific capacitance of B₅-CPPCN-700 reaches 503.3 F/g.Based on the B₅-CPPCN-700 symmetrical supercapacitor,at a current density of 0.5 A/g,the specific capacitance of a single electrode and the entire device are 299.7F/g and 74.9 F/g,respectively.And it exhibits a high material level energy density of 15.0 Wh/Kg at 300.0 W/Kg.（3）Using 2,6-bis（2-pyrazinyl）-4-（4-cyanophenyl）pyridine（named CN）as carbon source,the effects of different proportion of B,P or N atom doping,zinc salt pore-forming and KOH activation on the electrochemical properties of carbon materials were investigated.Compared with boric acid,potassium dihydrogen phosphate and nicotinic acid,the doping of B atom can improve the electrochemical performance of ligand CN to a greater extent.Among them,the molar ratio of boric acid to the ligand CN of B_0.5-CNPCN-700 has the largest specific capacitance.In the three-electrode system,when the current density is 0.5 A/g,the specific capac-itance of B_0.5-CNPCN-700,CNPCN-700 and CN-700 are 421.7 F/g,307.5 F/g and 210.2 F/g,respectively.