Electric Double Layer on a Renewable Liquid (Cd–Ga) Electrode in Acetonitrile Solutions

Abstract

Parameters that characterize the electric double layer structure on a renewable liquid (Cd–Ga) (0.3 at % Cd) electrode in solutions of surface-inactive electrolytes in a solvent with the low donor number, namely, acetonitrile (AN), are obtained. For the (Cd–Ga) electrode in AN, the following parameters: the potential of zero charge (PZC) unaffected by specific adsorption of ions, the value of “corrected electrochemical work function,” and the potential drop due to chemisorption of solvent, are obtained and compared with analogous results at Hg/AN, Ga/AN, (Cd–Ga)/gamma-butyrolactone (GBL), and (Cd–Ga)/dimethylformamide (DMF) interfaces. The AN chemisorption shifts the potential in the negative direction, which suggests that chemisorbed AN dipoles are oriented with their negative (nitrogen) ends to the metal surface. It is demonstrated that the solvent chemisorption potential drop on the (Cd–Ga) electrode increases in the series AN < GBL < DMF, i.e., with the increase in solvent’s donor number. The energy of chemisorption interaction metal–AN increases when going from (Cd–Ga) to Ga, i.e., with the increase in the work function. Based on the PZC shifts observed in 0.1 М LiBr and LiI solutions with respect to the PZC in solution of a surfaceinactive electrolyte, the adsorbability of halide ions on the (Cd–Ga)/AN interface is studied. The close values of the adsorption potential shift are obtained for Br^– and I^– ions, which suggests the stronger (Cd–Ga)–Br^– interaction as compared with (Cd–Ga)–I^–.