Study of the aging process of nanostructured porous carbon-based electrodes in electrochemical capacitors filled with aqueous or organic electrolytes

Abstract We report in this work the surface chemistry and the electrochemical studies on electrodes composed of randomly oriented multi-walled carbon nanotubes supported on stainless-steel (AISI:ROMWCNTs) confined in symmetric coin cells, before and after the electrode aging process accomplished in aqueous and organic electrolytes. We contrasted features from the as-grown and aged electrodes obtained during the different electrochemical experiments using cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy techniques. Also, several studies involving the Raman, Fourier transform infrared, and X-ray photoelectron spectroscopy, and the scanning electron microscopy techniques were carried out. Our experimental findings indicated that the electrode material shows fair good stability during the charge-discharge processes carried out using the different electrolytes. The aging process observed for each electrolyte revealed the formation of reaction by-products during the long-term charge-storage endurance tests. We additionally performed the in situ (operando) Raman characterization study of the electrodes under dynamic polarization conditions. In this sense, we verified the reversible Raman shifts (e.g., G & D bands) accounting for the dynamic nature of the charge accumulation-depletion processes occurring inside the electrical double-layer structure.