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

Abstract

The electric double layer (EDL) is one of the key concepts in electrochemistry, and understanding its charging kinetics is of key importance. Significant progress has been made via theoretical methods; however, it is challenging to study the ion dynamics experimentally in porous carbon electrodes under realistic conditions because of fast charge relaxation. In this work, the charging kinetics of porous carbon electrodes with different pore sizes in an aqueous electrolyte was experimentally investigated in electrolytes with various concentrations by using a cavity microelectrode. We were able to observe electrolyte depletion, and we systematically studied the key parameters that will affect the electrolyte depletion, resulting in major changes in the charging kinetics. Results showed that low concentration, high overpotential, and small carbon pore size triggered the electrolyte depletion, decreasing the charging kinetics. These findings further push our understanding of the ion dynamics of the EDL at the charged porous carbon/electrolyte interface.