Ion transfer kinetics at the interface between two immiscible electrolyte solutions supported on a thick-wall micro-capillary. A mini review

Abstract

Absence of an agreement on the values of the experimental rate constant of the ion transfer across the interface between two immiscible electrolyte solutions (ITIES) has stimulated the development of a more reliable methodology of kinetic measurements. This communication provides a brief review of our recent kinetic studies of the model tetraethylammonium (TEA+) ion transfer across the water/1,2-dichloroethane interface supported on a thick-wall micro-capillary by electrochemical impedance spectroscopy, noise analysis and steady-state voltammetry, all which give comparable values of the apparent standard rate constant k0 ≈ 0.3–0.7 cm s−1. Similar values of the apparent activation energies, which were evaluated from the temperature dependence of k0 and the diffusion coefficient of TEA+ (∼13 kJ mol−1), point to the absence of an additional energy barrier for the ion to overcome in the interfacial region. Role of the coupling of the ion motion and thermal corrugations of the interface (solvent protrusions) in the ion transfer kinetics is highlighted. Stochastic effects in the ion transfer kinetics at the nanoscopic ITIES are worth considering.