Specific adsorption of bromide and iodide ions on liquid Ga electrode from 0.1m M LiBr+0.1(1-m) M LiClO4 and 0.1m M LiI+0.1(1-m) M LiClO4 mixed solutions in dimethyl formamide

摘要

The differential capacitance curves were measured with an ac bridge in the Ga/[DMF + 0.1m M LiBr + 0.1(1 - m) M LiClO4] and Ga/[DMF + 0.1m M LiI + 0.1(1 - m) M LiClO4] systems at the following fractions m of surface-active anion: 0, 0.01, 0.02, 0.05, 0.1, 0.2, 0.5, and 1. Dimethyl formamide (DMF), as well as N-methyl formamide (N-MF), enables one to realize considerable positive charges of Ga electrode, at which it remains ideally polarizable (up to 11 mu C/cm(2)). The data on the specific adsorption of Br- and I- anions in these systems can be quantitatively described by the Frumkin's isotherm. The free energy of Br- and I- adsorption Delta G (ads) is a quadratic function of electrode charge. It is found that, at the Ga/DMF interface, Delta G (ads) varies in the series I- < Br- < Cl-. It is shown that the series of surface activity of halide ions is reversed when we pass from Hg/DMF and Bi/DMF interfaces to Ga/DMF interface. In contrast to the Ga/N-MF interface, where the values of Delta G (ads) for Br- and I- were almost equal and an increase in Delta G (ads) for Cl- was rather small, at the Ga/DMF interface, Delta G (ads) increases significantly in the series I- < Br- < Cl-.