Usefulness of a composite electrode with a carbon surface modified by electrosynthesized polypyrrole for supercapacitor applications

Thin polypyrrole (PPy) films (thickness = 5-10 nm) were electrochemically deposited in situ on a carbon paste (97% of graphite plus 3% of Teflon) by means of cyclic voltammetry (CV), from an acetonitrile solution of pyrrole (0.2 M) and NaClO4 (0.1 M). The obtained PPy/graphite composite electrode was investigated by CV and chronopotentiometry in 0.3 M NaClO4 aqueous electrolytic solution. The capacitance of a composite electrode, calculated by CV, was about 10 F g(-1). The capacitance value of the composite electrode was approximately nine times larger than that of pure graphite. The massic charge and discharge capacity (Q) values, calculated by chronopotentiometry, were considerably higher for the composite electrode-by more than 60 times-than for the pure graphite electrode. Electrochemical impedance spectroscopy (EIS) measurements, performed under stationary conditions, led to an interfacial capacitance value intermediate between that of pure graphite and that of the composite electrode.