Unveiling the ionic exchange mechanisms in vertically-oriented graphene nanosheet supercapacitor electrodes with electrochemical quartz crystal microbalance and ac-electrogravimetry

Abstract

This work presents the first electrochemical quartz crystal microbalance (EQCM) results for vertically-oriented graphene nanosheets (VOGNs) as supercapacitor electrodes. Conventional EQCM technique delivered primary insights on the ionic exchange mechanisms between VOGNs and organic electrolytes, showing a major contribution of anions. A more advanced electrogravimetric methodology, ac-electrogravimetry, was then used to access specific dynamic attributes for each species exchanged at the VOGN electrode surface. Accordingly, under the conditions of this study, anions were confirmed to be the major energy storage vector with high kinetic values and low transfer resistance while cations and free solvent molecules are given non-negligible supporting roles.