Preparation Of Functionalized Graphene And Investigation Of Its Electrochemical Performance

Graphene has attracted more and more attention in the field of materials because of its unique two-dimensional structure,excellent physical and chemical properties.It is considered to be an excellent electrode material for supercapacitor.However,the specific capacitance of pure reduced graphene is far lower than the theoretical value.Therefore,it has become one of the hot topics to obtain the modified graphene to meet the demand of the modern supercapacitor electrode materials.In this paper,diaminopyridine was used as precursor to prepare modified graphene under different experimental conditions.Diaminopyridine also can be polymerized to prepare graphene/poly diaminopyridine composite.The application of modified graphene prepared under different conditions in supercapacitor was investigated.The results are as follow:In the solution,DAP molecules were covalently functionalized onto graphene sheets through the nucleophilic S_N2 displacement reaction between the amine groups of DAP and the epoxy groups on the basal plane of GO in alkaline condition,thus the surface modified functionalized graphene was obtained.The feed ratios of reactants will affect the structure and electrochemical properties of the nitrogen functionalized graphene.The different microstructures and electrochemical performance of functionalized graphene were caused by different positions of-NH₂ groups on the pyridine rings of diaminopyridine isomers due to the steric effect.Among them,the functionalized graphene P-NFG modified with 2,3-diaminopyridine showed the highest specific capacitance.The nitrogen-doped graphene can be obtained by the reaction of nitrogen-containing precursor and graphene oxide suspension under hydrothermal condition.The electrochemical properties of nitrogen-doped graphene materials obtained under 165^oC exhibited the best electrochemical properties.The two adjacent amino groups on the 2,3-diaminopyridine can react with the dihydroxyl group on the edge of graphene oxide layer to form a double-N doped pyrazine structure.In the hydrothermal process,quaternary-nitrogen will be formed due to nitrogen atoms will doped into the carbon framework,which can improve the conductivity of the electrode materials.In the three electrode system,the specific capacitance of nitrogen-doped graphene modified with 2,3-diaminopyridine?O-DAP-NG?at the current density of 0.1 A/g is 421 F/g.The O-DAP-NG electrode delivered the maximum specific capacitance of 274 F/g at the current density of 0.5 A/g,and it also displays excellent electrochemical stability of 91.5%after 5000 charge-discharge cycles.Poly?diaminopyridine??PDAP?was in situ grafted to graphene oxide in solution to obtain the poly?diaminopyridine?/graphene composite.The composite material of poly diaminopyridine/graphene can be obtained by optimizing the feeding ratio and heat reduction temperature.The specific capacitance of the best composite material after low temperature thermal treatment is 264 F/g at the current density of 0.1 A/g.The application of poly diaminopyridine in supercapacitors has certain prospects and needs to be further explored.