Abstract
Cyclic voltammetry experiments at various electrolyte solution concentrations (0.001-0.1 M) and scan rates (1 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.
Original language | English |
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Pages (from-to) | 159-167 |
Number of pages | 9 |
Journal | Journal of Electroanalytical Chemistry |
Volume | 540 |
DOIs | |
State | Published - Jan 2 2003 |
Funding
Support for this research was provided by the National Science Foundation through a Career Award (BES-9702356 to S.Y.). Support to C.T. was provided by the Office of Basic Sciences, Division of Chemical Sciences, U.S. Department of Energy, under contract DE-AC05-00OR22725 with UT-Battelle, LLC. We also gratefully acknowledge partial support of this project by the Georgia Institute of Technology Molecular Design Institute, under prime contract N00014-95-1-1116 from the Office of Naval Research. The authors are also grateful to Dr E. Steven Vittoratos for conducting specific surface area and pore size distribution measurements of the carbon aerogel material and to Dr Marsha Savage for editing the manuscript. Computations were supported by the Center for Computational Molecular Science and Technology at the Georgia Institute of Technology (GT) and partially funded through a Shared University Research (SUR) grant from IBM and GT. Computations were also supported by the GT High Performance Computing (HPC) Center.
Keywords
- Carbon aerogel
- Cyclic voltammetry
- Electrical double layer
- Electrosorption
- Point of zero charge