Electrosorption capacitance of nanostructured carbon aerogel obtained by cyclic voltammetry

Cyclic voltammetry experiments at various electrolyte solution concentrations (0.001-0.1 M) and scan rates (I to 5 mV s(-1)) have been performed to study the electrical double layer (edl) formation in nanostructured carbon aerogel. The results show that carbon aerogel is a good edl capacitor and can be further divided into mesoporous and microporous capacitors. According to the experiments, the mesoporous capacitor shows a fast charging/discharging response and is only minimally affected by the electrolyte concentration and scan rate. Therefore, the specific capacitance of the mesoporous capacitor is found to be constant over a wide range of applied electrical potentials. On the other hand, the microporous capacitor shows a slow charging/discharging response and its capacitance strongly depends on the electrolyte concentration and potential. Unlike previous experiments, in which only a flat minimum was observed at the point of zero charge (pzc), in the current study, a deep minimum is observed near the pzc at low electrolyte concentration if a slow scan rate is used. This unique feature is a result of edl overlapping in the micropores and is consistent with the predictions by the Gouy-Chapman model employed in this study. Based on this behavior, a new approach is suggested for pzc measurements of solid porous materials for which a large portion of the surface area is in the micropore region. (C) 2002 Elsevier Science B.V. All rights reserved.