Excellent electrochemical performance of homogeneous polypyrrole/graphene composites as electrode material for supercapacitors

Polypyrrole (PPy) was synthesized on graphene (GN) sheets which was reduced from graphene oxide by microwave irradiation in N-methyl-2-pyrrolidinone (NMP) and dispersed very well in beta-naphthalene sulfonic acid solution. Homogeneous polypyrrole/graphene (PGN) composites had been successfully prepared via an in situ emulsion polymerization method and showed better electrochemical performance including high specific capacitance, rate characteristic and cycling stability compared with polypyrrole/graphene oxide (PGO) composites. The NMP molecules entered into GN which was helpful for PPy deposition on the GN sheets evenly. The supercapacitive behaviors of the corresponding electrodes were estimated with cyclic voltammetry and galvanostatic charge/discharge measurements in 1 M KCl electrolyte and the results showed that the specific capacitance of PGN composites was up to 906 F g(-1) at the current density of 0.2 A g(-1), much higher than that of the PGO (704 F g(-1)) and PPy (430 F g(-1)). Its specific capacitance retains more than 91 % of its initial capacitance after 1,000 cycles at a high current density of 5 A g(-1). The good electrochemical performance of PGN composites is mainly attributed to its uniform structure, the N doping, and the synergistic effects between the two components.