The electrochemical characteristics of polypyrrole doped with either perchlorate or Nation are determined. Polypyrrole doped with Nation ions or perchlorate ions exhibits a specific capacitance of 344 or 355 F g(-1), respectively. Cycle life experiments reveal that the Nafion-doped material retains 98% of the original capacitance after 3000 cycles whereas that doped with perchlorate retains only 70% over this period. Scanning electron microscopy (SEM) before and after long-term cycling, reveals some mechanical degradation. (C) 2008 Published by Elsevier B.V.