Raman spectroelectrochemistry of a carbon supercapacitor

Confocal Raman microspectrometry has been applied to the in situ study of an electrical double-layer capacitor involving activated carbon cloth electrodes and an organic electrolyte. The Raman spectra of the carbon electrodes have been recorded during the charge and discharge. The intensity variations of the G and D bands have been correlated with carbon electronic conductivity changes. At the same time, the salt concentration has been measured in the electrolyte diffusion layer at about 10 mum from the carbon electrodes and significant ionic depletions have been observed during the charges and discharges. The whole results indicate that the two double-layer interfaces do not work in a symmetrical way and a mechanism is proposed to explain the observed effects. (C) 2001 The Electrochemical Society.