Capacitance Measurements in a Series of Room-Temperature Ionic Liquids at Glassy Carbon and Gold Electrode Interfaces

Abstract

An extensive study has been done for the first time on the structure of the electrical double layer (EDL) at polarized glassy carbon (GC) and gold (Au) electrode interfaces in a series of room-temperature ionic liquids (RTILs) via the measurement of capacitance-potential curves. The parabolic capacitance-potential curves similar to those observed in high-temperature inorganic molten salts were obtained at GC electrode in all of the RTILs studied. Potential of zero charge (PZC) at GC electrode in imidazolium-based RTILs depends significantly on the electrochemical pretreatment of the electrode surface: Electrochemical oxidation pretreatment generates the oxide surface on GC electrode, which results in a favorable adsorption of positively charged imidazolium cations on the electrode surface and in turn shifts the PZC to the positive direction of potential, whereas at the electrochemically reduced GC electrode, on which the adsorption of the imidazolium cations is less favorable, PZC shifts to the negative d...