Understanding Ion Charging Dynamics in Nanoporous Carbons for Electrochemical Double Layer Capacitor Applications

Theelectric double layer (EDL) is one of the key concepts in electrochemistry,and understanding its charging kinetics is of key importance. Significantprogress has been made via theoretical methods; however, it is challengingto study the ion dynamics experimentally in porous carbon electrodesunder realistic conditions because of fast charge relaxation. In thiswork, the charging kinetics of porous carbon electrodes with differentpore sizes in an aqueous electrolyte was experimentally investigatedin electrolytes with various concentrations by using a cavity microelectrode.We were able to observe electrolyte depletion, and we systematicallystudied the key parameters that will affect the electrolyte depletion,resulting in major changes in the charging kinetics. Results showedthat low concentration, high overpotential, and small carbon poresize triggered the electrolyte depletion, decreasing the chargingkinetics. These findings further push our understanding of the iondynamics of the EDL at the charged porous carbon/electrolyte interface.