Estimation of the specific adsorption of I⁻, Br⁻, and Cl⁻ ions in systems (Tl-Ga)/[N-methylformamide + 0.1m M KA + 0.1(1 − m) M KClO₄] (KA is KCl, KBr, and KI) based on the analysis of two-dimensional pressure curves obtained by integration of differential capacitance

Abstract

By means of an ac bridge, the differential capacitance vs. potential curves are measured in systems (Tl-Ga)/[N-MF + 0.1m M KI + 0.1(1 − m) M KClO₄], (Tl-Ga)/[N-MF + 0.1m M KBr + 0.1(1 − m) M KClO₄], and (Tl-Ga)/[N-MF + 0.1m M KCl + 0.1(1 − m) M KClO₄] for the following fractions m of the surfaceactive anion: 0, 0.02, 0.05, 0.1, 0.2, 0.5, and 1. Based on the analysis of curves of two-dimensional pressure found by integrating the differential capacitance, it is shown that the data on the specific adsorption of anions I⁻, Br⁻, and Cl⁻ in the mentioned systems can be quantitatively described by the Frumkin isotherm. The main adsorption parameters of I⁻, Br⁻, and Cl⁻ anions at the (Tl-Ga)/N-MF interface are determined. It is found that on the (Tl-Ga)/N-MF interface, the same as on the (In-Ga)/N-MF interface, the adsorption energy of ions increases in the sequence Cl⁻ < Br⁻ < I⁻, in contrast to the Ga/N-MF interface, where the energy increases in the reverse sequence: I⁻ ≈ Br⁻ < I⁻. For all halide ions (Hal⁻), the adsorption energy and the energy of metal-Halinteraction increase in the sequence (Tl-Ga) < (In-Ga) < Ga.