Anomalous Capacitance Maximum of the Glassy Carbon-Ionic Liquid Interface through Dilution with Organic Solvents.
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.
†Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, United States.
David J
DJ
Bozym
†Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, United States.
Betül
B
Uralcan
‡Princeton Center for Theoretical Science, Princeton University, Princeton, New Jersey 08540, United States.
David T
DT
Limmer
†Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, United States.
Michael A
MA
Pope
†Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, United States.
Nicholas J
NJ
Szamreta
†Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, United States.
Pablo G
PG
Debenedetti
†Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, United States.
Ilhan A
IA
Aksay
Ising model; acetonitrile; capacitance; electrochemical impedance spectroscopy; glassy carbon; room temperature ionic liquid