Effect of metal nature on energy of specific adsorption of chloride ions from dimethyl formamide solutions

Resumo

The specific adsorption of chloride ions on the renewable liquid (Cd–Ga) electrode from mixed [0.1_m М LiCl + 0.1(1–_m) М LiBF₄] solutions in dimethyl formamide (DMF) is studied with an ac bridge at the following fractions of surface-active anion m: 0, 0.01, 0.02, 0.05, 0.1, 0.2, 0.5 and 1. It is found that the data on the specific adsorption of Cl^– anion in the system can be quantitatively described by Frumkin’s isotherm. The free adsorption energy of Cl^– (ΔG_ads) is a quadratic function of electrode charge. The results are compared with the corresponding data for the Ga/DMF and (In–Ga)/DMF interfaces. It is shown that the adsorption energy of Cl–anions at the metal/DMF interface depends on the metal nature and increases in the series (In–Ga) ≈ (Cd–Ga) < Ga. The energy of metal–DMF chemisorption interaction, which hampers ion adsorption, increases in the same series. The analysis of the data uniquely indicates that the free energy of metal–Cl^– interaction (ΔG_M-CL-) increases in the series (In–Ga) ≈ (Cd–Ga) < Ga. Thus, in the series of electrodes studied, the variations in the energies of metal–Cl^– and metal–DMF specific interaction are correlated: the higher the energy of metal–DMF chemisorption interaction, the higher the energy of metal interaction with Cl^–.