Electrical double layer and adsorption of iodide ions at the Bi|gamma-butyrolactone interface

• The interface Bi|γ-butyrolactone was studied by impedance measurement method.
• Adsorption of I− anions was studied at the Bi(1 1 1)|γ-butyrolactone interface.
• The mixed electrolyte method was used for the study of the adsorption of I− anions.
• The adsorption parameters of I− anions have been calculated.
• The adsorption of I− ions is stronger from γ-butyrolactone than for other solvents.

The adsorption of I− anions on the Bi(1 1 1) single crystal plane from solutions in gamma-butyrolactone has been investigated by impedance measurement method. The ionic charge due to the specific adsorption has been obtained using the mixed-electrolyte method applied for both electrode charge and electrode potential as the independent electrical variables. The Gibbs energy of I− anions adsorption has been calculated using the virial adsorption isotherm. It was found that under comparable conditions, the results obtained at constant electrode potential and at constant electrode charge, are coincident and the Gibbs energy of I− anion adsorption increases in the sequence of solvents: methanol < ethanol < propylene carbonate < gamma-butyrolactone < acetonitrile. The electrosorption valency value has been calculated and it was found that this parameter increases in the sequence: propylene carbonate < ethanol < gamma-butyrolactone < methanol < acetonitrile.