The structure of the electrical double layer on a liquid Pb–Ga alloy in aqueous, propylene carbonate, and formamide solutions of electrolytes

Abstract

A new atomically smooth renewable electrode is prepared and studied. The electrode is a liquid Pb–Ga alloy containing 0.06 atoms % of Pb. Its double layer characteristics differ drastically from those of a Ga electrode; they are practically identical to the characteristics of a Pb electrode. Thus, the Pb–Ga electrode actually is a model of the electrochemical properties of liquid Pb electrode. The adsorption of anions on the Pb–Ga electrode increases in the sequence BF 4 −=SO 4 2−<Cl −<Br −<I −. In the absence of metal–solvent chemisorption interaction and at a fixed charge, the ‘metal’ capacitance of the Pb–Ga electrode has an intermediate value between the ‘metal’ capacitances of Ga and Hg electrodes; it practically does not depend on the solvent nature. In relation to water, propylene carbonate and formamide, the Pb–Ga electrode is much less lyophilic than the Ga electrode; its lyophilic nature is practically similar to that of the Hg electrode. For In–Ga, Cd–Ga and Pb–Ga electrodes possessing nearly the same electrochemical work function value, the solvent–chemisorption potential drop is shown to differ significantly; it increases in the sequence Pb–Ga<In–Ga<Cd–Ga, as the distance of the nearest approach of solvent molecules to the ion cores of the metal decreases.