A Comparative Study of the Electrochemical Characteristics of [Emim⁺][BF₄⁻] and [Bmim⁺][BF₄⁻] Ionic Liquids at the Surfaces of Carbon Nanotube and Glassy Carbon Electrodes

Abstract

The electrochemical interfaces of a glassy carbon (GC) electrode and a carbon nanotube (CNT) paper electrode have been studied in 1-ethyl-3-methylimidazolium tetrafluoroborate (EmimBF 4 ) and 1-butyl-3-methylimidazolium tetrafluoroborate (BmimBF 4 ) ionic liquids (ILs) using direct current (DC) cyclic voltammetry (CV) and alternating current (AC) electrochemical impedance spectroscopy (EIS). These four electrode/electrolyte combinations serve as representative models of the relatively unconventional, spatially inhomogeneous IL−carbon interfaces that are potentially useful for electrochemical energy-storage/conversion devices. The present work explores in detail the double-layer capacitances as well as other essential electrochemical features of these interfaces. The voltage-dependent double-layer capacitances, and the interfacial charge transfer resistances have been determined within the nonfaradaic windows of these systems, independently, by using CV and EIS. The results of the DC and AC measurements have been compared to demonstrate how the material properties of such complex systems can affect their characterization procedures if they are simply treated as classical ideally polarized interfaces.