Adsorption of iodide ions at the Bi(1 1 1) | propylene carbonate + dimethyl carbonate interface

• The interface Bi | PC + DMC was studied by impedance measurements. • Adsorption of I - anions was studied at the Bi(1 1 1)| PC + DMC interface. • The adsorption parameters of I - anions have been calculated. • Adsorption of anions is stronger from pure carbonates than from solvent mixtures. The adsorption of I - anions on the Bi(1 1 1) single crystal plane from mixed solutions of propylene carbonate and dimethyl carbonate (1:1) has been investigated with impedance measurements. Both electrode charge and electrode potential were applied as the independent electrical variables in the calculations of the ionic charge due to the specific adsorption following the mixed-electrolyte method. The Gibbs energy of I - anions adsorption has been calculated using the virial adsorption isotherm. It was found that under comparable conditions, the standard Gibbs energy values obtained at constant electrode potential and at constant electrode charge, are coincident and the Gibbs energy of I - anion adsorption in the mixture is only slightly lower than in the pure propylene carbonate or ethylene carbonate solutions. However, at higher concentrations of iodide ions, the specific adsorption charge values in the mixture are remarkably lower than in pure propylene carbonate caused by different lateral repulsion values of iodide ions on the electrode surface in different systems. The electrosorption valency values have been calculated and it was found that this parameter is higher in the mixture than in pure propylene carbonate or in other organic carbonate solvents.