Electrocapillarity at the nonpolarized interface between the aqueous solution and the room-temperature molten salt composed of 1-octyl-3-methylimidazolium bis(pentafluoroethylsulfonyl)imide

Abstract

The interfacial tension between the room-temperature molten salt (RTMS, also called ionic liquid) composed of 1-octyl-3-methylimidazolium bis(perfluoroethylsulfonyl)imide (C₈mimC₂C₂N) and the aqueous solution containing 1-octyl-3-methylimidazolium chloride or lithium bis(perfluoroethylsulfonyl)imide has been measured as a function of the composition of the aqueous phase. The phase–boundary potential calculated for this non-polarized interface from the solution composition enables us to construct the corresponding electrocapillary curve, which shows a parabolic shape with respect to the variation of the phase–boundary potential over 300 mV. C₈mim⁺ ions specifically adsorb at the interface. Switching of the potential-determining ion from C₈mim⁺ to C₂C₂N⁻ causes a jump of more than 160 mV in the potential at the outer Helmholtz plane on the aqueous side of the interface.