Preparation Of Graphene/polypyrrole Composites And Their Applications In Supercapacitor Electrode Materials

Graphene,as the newest form of carbon materials has been applied to supercapacitor,electrochemical catalysis and other fields,owing to its excellent electrical and mechanical properties.But the specific capacitance of graphene as electrode material is still low.It is not benefit from the subsequent application because of poor dispersion.What's more,the toxic chemicals will be needed during the preparation process.Therefore,a "green" method for preparing a graphene film has been used in this paper.Although graphene has unique physical and chemical properties,such as high surface area,excellent conductance is much lower than the theoretical value.It has been shown that graphene can be incorporated with conducting polymers to improve the electrochemical properties of composite.The composite not only has high specific capacitance but also good cycle stability.Polypyrrole has the maximum theoretical specific capacitance and good environment stability.It should be noticed that methods of synthesizing graphene/polypyrrole composite in reported literatures were complicated and the capacitance of such materials are not high.Therefore,it is still a challenge to achieve a novel and simple method to synthesis graphene/polypyrrole composite and meanwhile obtaining high specific capacitance as well as good cycle stability.The contents of the paper are given as follow:(1)The graphene oxide was reduced to obtain graphene film by cyclic voltammetry in tow-electrode system.The morphology,structure,the degree of reduction,electrical conductivity are characterized by SEM,TEM,Raman,AFM,XPS and four terminal instrument.Meanwhile,the electrochemical properties are characterized by cyclic voltammetry curves and constant current charge-discharge curves.A maximum capacitance value of 120 F/g has been obtained for this composite at current density of 0.1 A/g.The composite achieved high electrical conductivity of 64.6 S/cm.The damping of the specific capacitance is loss 39%after 1500 charge/discharge processes at 20 mV/s scan rate.(2)The graphene/polypyrrole composite were prepared by potentiostatic deposition.The morphology,structure and thermal stability are researched by TEM,SEM,Raman and TGA.It has been shown that the addition of graphene has a significant impact on the morphology,structure and thermal stability of the material.(3)We successfully synthesize graphene/polypyrrole composite at varying concentration of SDBS,Synthetic time and the content of graphene in order to gain excellent electrochemical performance.A maximum capacitance value of 310 F/g has been obtained for this composite at a current density of 0.3 A/g;the specific capacitance is 307 F/g at 10 mV/s scan rate,and remains 255 F/g at 300 mV/s scan rate.The specific capacitance still remains 71%after 1500 cycles at 50 mV/s scan rate.The electrochemical properties of supercapacitor assembled by composite were tested.The result show that the specific capacitance can still reach 253 F/g at a current density of 0.3 A/g.