The inherent capacitive behavior of imidazolium-based room-temperature ionic liquids at carbon paste electrode

Abstract

Apparent capacitive characteristics of imidazolium-based room-temperature ionic liquids are justified by means of cyclic voltammetry and impedance techniques using the graphitic carbon paste electrode as a probe in virtue of its low substrate current. The morphological observation shows that the alternate intercalation of the cation and anion of the ionic liquids largely increases the specific surface areas. This outcome is consistent with the electrochemical results. The inherent capacitances are directly related to the special structures of imidazolium-based room-temperature ionic liquids at the interphase region. The formation of bulky ionic pairs owing to intramolecular hydrogen bonding interactions create a third charge layer between the electrode/electrolyte double-layer, which makes the interface rougher and hold more charges. Thus, a hypothesis of "quasi-ternary layers" distribution of charges at the interface is derived, which clarifies the capacitive behavior of the ionic liquids. © 2005 The Electrochemical Society. All rights reserved.