EQCM as a unique tool for determination of ionic fluxes in microporous carbons as a function of surface charge distribution

Abstract

We have recently discovered (M.D. Levi et al. (2009) [5]) that electrochemical quartz crystal microbalance (EQCM) method can be successfully used to provide unique information on the ions adsorption during reversible cycling of porous carbon electrodes. The present paper extends the proposed approach to the analysis of the ions content in the carbon micropores in contact with binary aqueous CsCl solutions of different concentrations, and with a mixed CsCl + HCl solution. Evidence was found that microporous carbons suitable for supercapacitor applications reveal perm-selectivity failure near the pzc in the binary electrolyte solutions due to competing counter- and co-ions fluxes. Oxygen-containing functionalities are responsible for the development of the positive charge on the carbon surface in contact with mixed acidified solution, imparting the carbon electrode the property of an anion-exchanger, readily revealed by EQCM.