Adsorption of bromide and iodide anions on a renewable liquid (Cd–Ga) electrode from acetonitrile solutions. Effect of (Cd–Ga)–solvent chemisorption interaction on the anion adsorption energyстатья
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Дата последнего поиска статьи во внешних источниках: 12 января 2022 г.
Аннотация:The specific adsorption of bromide and iodide anions was studied at the (Cd-Ga)/acetonitrile (AN) interface from mixed solutions of [0.1m M LiBr + 0.1 (1-m) M LiBF4] and [0.1m M LiI + 0.1 (1-m) M LiBF4] at the following values of molar fraction m of the surface–active anion: 0, 0.01, 0.02, 0.05, 0.1, 0.2, 0.5, and 1. The main experimental method was measurement of differential capacitance on a renewable liquid (Cd–Ga) electrode. The obtained experimental results can be described quantitatively by the Frumkin isotherm in a wide range of charge densities (σ). The adsorption parameters of halide anions (Hal–) were determined using a regression analysis of two-dimensional pressure isotherms. It is shown that the adsorption energy (ΔGads) of Br– and I– at the (Cd–Ga)/AN interface practically coincides. It follows that the difference in the interaction energies of Br– and I– with (Cd–Ga) is equal to the difference of the solvation energies of these anions: ( ) ≈ ( ) and therefore ΔG(Cd-Ga)-I– < ΔG(Cd-Ga)-Br–. The adsorption parameters of Hal– obtained on (Cd–Ga)/AN interface were compared with similar data for (Cd–Ga)/DMF interface. The adsorption energy of Br- and I- on the (Cd-Ga) electrode increases significantly when passing from DMF to AN. This result can be unambiguously explained by a significant decrease in the energy of chemisorptions interaction of (Cd-Ga) electrode with solvent molecules in the Helmholtz layer during the transition from DMF to AN. The ΔGads,σ dependence obtained at the (Cd–Ga)/AN interface in the first approximation characterizes the change of the free energy of (Cd–Ga)–Hal– interaction with σ. It is shown that the slope of the ΔGads, σ- dependence decreases upon transition from the (Cd–Ga)/AN interface to the (Cd–Ga)/DMF interface due to a significant increase in the energy of the chemisorption interaction of (Cd–Ga) with DMF molecules in the Helmholtz layer during the transition from negative to positive values of charge density.