Electric double layer on renewable liquid (Cd–Ga) electrode in dimethylformamide solutions

Abstract

The double-layer characteristics on a renewable liquid (Cd–Ga) electrode (0.3 at % Cd) in dimethylformamide (DMF) solutions of various electrolytes are studied by the methods of differential capacitance and open-circuit streaming electrode. The zero-charge potentials unaffected by specific adsorption of ions and the parameters characterizing the (Cd–Ga)–DMF chemisorptive interaction (chemisorption potential drop of solvent and two-dimensional pressure of chemisorbed DMF dipoles) are determined. The results are compared with similar results for the (Cd–Ga)/gamma-butyrolactone (GBL) interface. The energy of (Cd–Ga)–solvent chemisorptive interaction increases with the transition from GBL to DMF due to the increase in the donor number of solvent. The adsorbability of halide ions at the (Cd–Ga)/DMF interface is judged based on the PZC shift in 0.1 М solutions of LiCl, LiBr, and LiI with respect to the PZC in solutions of a surface-inactive electrolyte. On the (Cd–Ga)/DMF interface, the inverted series of surface activity of halide ions is observed. Whereas on Hg and Bi electrodes the surface activity increases in the series Cl^– < Br^– < I^–, on the (Cd–Ga) electrode and also on Ga and (In–Ga) electrodes the activity varies in the inverted sequence I^‒ < Br^– < Cl^–.