Significant Role of Ultramicropores on Capacitive Properties of Polypyrrole-Based Carbons.

N-doped carbon was synthesized by carbonization of polypyrrole at 700 °C and further reduced by hydrogen under the same temperature. Pore-structure and surface elemental analyses show that both carbons have a low apparent specific surface area (by nitrogen sorption analysis) and there is a decrease of nitrogen content when the original carbon was reduced by hydrogen. However, electrochemical measurements such as cyclic voltammetry and galvanostatic chargedischarge indicate that there is no correlation between nitrogen content and specific capacitance. Further detailed porestructure characterization was performed by carbon dioxide physisorption analysis, which reveals that there are many ultramicropores in both carbons. Those ultramicropores are not available to nitrogen molecule but carbon dioxide and electrolyte ions, thus playing a dominant role on the energy storage process. [ABSTRACT FROM AUTHOR]