Anomalous Capacitance Maximum of the Glassy Carbon-Ionic Liquid Interface through Dilution with Organic Solvents

Citation:

Bozym, D. J. ; Uralcan, B. ; Limmer, D. T. ; Pope, M. A. ; Szamreta, N. J. ; Debenedetti, P. G. ; Aksay, I. A. Anomalous Capacitance Maximum of the Glassy Carbon-Ionic Liquid Interface through Dilution with Organic Solvents. J. Phys. Chem. Lett. 2015, 6 2644-2648.

Abstract:

We use electrochemical impedance spectroscopy to measure the effect of diluting a hydrophobic room temperature ionic liquid with miscible organic solvents on the differential capacitance of the glassy carbon − electrolyte interface. We show that the minimum differential capacitance increases with dilution and reaches a maximum value at ionic liquid contents near 5 − 10 mol% (i.e., ∼ 1 M). We provide evidence that mixtures with 1,2-dichloroethane, a low- dielectric constant solvent, yield the largest gains in capacitance near the open circuit potential when compared against two traditional solvents, acetonitrile and propylene carbonate. To provide a fundamental basis for these observations, we use a coarse-grained model to relate structural variations at the double layer to the occurrence of the maximum. Our results reveal the potential for the enhancement of double-layer capacitance through dilution.