Mixture of 1-ethyl-3-methylimidazolium tetrafluoroborate and 1-ethyl-3-methylimidazolium iodide: A new potential high capacitance electrolyte for EDLCs

Abstract

The electrochemical characteristics of the interface between Bi(111) and the mixture of 1-ethyl-3-methylimidazolium tetrafluoroborate and 1-ethyl-3-methylimidazolium iodide were electrochemically characterized by using cyclic voltammetry and electrochemical impedance spectroscopy. The region of ideal polarizability, the formation/rearrangement kinetics of the electrical double layer, the values of series and parallel capacitance and the adsorption kinetics of ions depend on the addition of EMImI in the mixture. Based on the experimental data, it was found that the region of ideal polarizability of Bi(111) single crystal electrode in the mixture under study is comparable to the values measured in “pure” ionic liquids. Capacitance depends strongly on AC frequency and electrode potential, increasing considerably at E>−0.7V vs. Ag|AgCl, where the specific adsorption of iodide ions with partial charge transfer from ions to electrode surface and vice versa occurs.