Interfacial Layer between a Mercury Electrode and Dilute Aqueous Solutions of Alkali-Metal Chloride at Potentials of the Cathodic Limiting Current Plateau

Abstract

Abstract The electrochemical properties of the interfacial layer between a DME and dilute aqueous solutions of MCl (M: alkali-metal) at the cathodic limiting current plateau were studied by means of impedance measurements at relatively low frequencies (≤250 Hz). From the frequency and potential dependence of the capacitive and the resistive components of the electrode impedance, the following conclusions were obtained concerning the properties of the interfacial layer under the above condition: (i) when the concentration of cations is extremely low in the vicinity of the electrode surface, the impedance behaves as if the conventional double-layer were absent: (ii) the impedance behavior of the present system can be explained by assuming an equivalent circuit which is given by a series combination of the Warburg impedance for the reduction of M+ and the resistance of solution; and (iii) such an interfacial layer is conventionally called “the Nernst double-layer” and its formation is determined by the mass-transport of the reacting species M+.