Ionic Liquid Structure Dependent Electrical Double Layer at the Mercury Interface

Abstract

Structures of the electrical double layer at Hg|room-temperature ionic liquid (RTIL) interfaces were studied by measuring the differential capacitance and electrocapillary curves as a function of potential. Maxima of the electrocapillary curves measured at the Hg|1-hexyl-3-methylimidazolium tetrafluoroborate (HMIBF4) and 1-octyl-3-methylimidazolium tetrafluoroborate (OMIBF4) interfaces demonstrate an unusual broadness on the anodic side of the potential of zero charge (PZC), which is significantly different from those obtained at Hg in RTILs containing shorter alkyl chains or in conventional molecular solvents containing electrolytes. This broadness of the electrocapillary curve was found to depend on the crystal structure and spatial heterogeneity of the RTILs containing larger alkyl groups, which impede the charged moieties from being in contact with the electrode surface within a certain potential range. Cleaving of the liquid crystal structure by the dilution of OMIBF4 with dimethyl sulfoxide, which is reflected on the electrocapillary and surface charge density versus potential curves, supports the above reasoning. This is the first report on the dependence of the interfacial structure at the Hg electrode on the structure of the RTIL itself. A schematic model of the structure of the electrical double layer is also given.

Experimental, quantum chemical and Monte Carlo simulation studies on the corrosion inhibition of some alkyl imidazolium ionic liquids containing tetrafluoroborate anion on mild steel in acidic medium

“…It is well known that long alkyl chain length results in higher inhibition efficiency for a set of ILs with the same anion head groups [42,43]. Hence, the higher % IE of [C 10 [42][43][44][45]. The %IE obtained from both polarization and impedance measurements are comparable to a fair degree, and this is depicted in Fig.…”

“…Inhibition activities of ILs are usually associated with the interactions of the hydrophobic tails and/or the electrostatic interaction of the head groups with the charged metal surface [40]. It is well known that long alkyl chain length results in higher inhibition efficiency for a set of ILs with the same anion head groups [42,43]. Hence, the higher % IE of [C 10 [42][43][44][45].…”

Mean-Field Theory of Electrical Double Layer In Ionic Liquids with Account of Short-Range Correlations

“…Plots generated using estimates from Ref. 40 show curves that resemble those obtained for ionic liquids at metallic electrodes [37][38][39]80].…”

The Electrode/Ionic Liquid Interface: Electric Double Layer and Metal Electrodeposition

“…Up to now, differential capacitance curves have been measured on different electrodes including liquid metal Hg, [56,95,96] solid metals Au [29,97,98] and Pt, [83,84,[97][98][99] glassy carbon (GC), [48,97,98,100] and HOPG. [98,100] The ionic liquids involved are mainly with alkylimidazolium-based cations.…”

“…[98,100] The ionic liquids involved are mainly with alkylimidazolium-based cations. Bell-shaped, [29,97] camel-shaped, [48] and even parabolic [56,83,84,[95][96][97][98]100] capacitance curves have been obtained depending on the electrodes and ionic liquids employed, which exclude the possibility to determine the PZCs from differential capacitance curves in ionic liquids by a universal rule.…”