Electrochemical Characteristics of Ionic Liquid at Metal Surface

Ionic liquids (ILs) are electrically conductive molten salts at room temperature with extremely low vapor pressure (“green chemicals”). ILs also have excellent thermal stability and wide temperature ranges for the liquid phase. Due to their unique physical and chemical properties, IL electrolytes, particularly in combination with carbon nanotube (CNT) electrodes, represent an important class of experimental systems for energy storage. We report electrochemical characterization experiments for such a system involving a paper-electrode of multiwall CNT and an IL electrolyte of 1-Hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([Hmim][Tf2N]). Electrochemical characterization of ionic liquid at different metal electrodes such as, glassy carbon, platinum, gold and tantalum are also presented. A novel three-electrode cell (containing only 400 µL of electrolyte) is designed for these experiments, and the measurements include cyclic voltammetry (determination of electrochemical window and differential capacitance), as well as D.C. voltage dependent electrochemical impedance spectroscopy (EIS). The results demonstrate how the electrochemistry of the CNT-IL interface deviates from that of nonporous electrodes in traditional dilute solutions