Tracking ionic fluxes in porous carbon electrodes from aqueous electrolyte mixture at various pH

Abstract

Electrochemical quartz crystal microbalance (EQCM) and cyclic voltammetry (CV) techniques were used to study ion dynamics in porous carbide-derived carbon (CDC) electrodes in various aqueous electrolytes. Although the cyclic voltammetries look similar, EQCM revealed different ion transfer depending on the electrolyte during both positive and negative polarization. During polarization in neutral K2SO4 electrolyte, partial desolvation of cation and anion were observed in carbon micropores. In EMI+-HSO4− electrolyte, the main charge carrier during cation adsorption was not found to be bulkier EMI+, but smaller and highly mobile H+. Furthermore, ionic fluxes during charging/discharging were monitored and identified in multi-ions aqueous system, which was ambiguous according to the CV plots. EQCM shows its powerful ability to serve as an accurate gravimetry probe to study the electrolyte concentration and compositional changes in porous materials.