Specific adsorption of bromide and iodide ions on the (Cd–Ca)/dimethylformamide interface

The specific adsorption of bromide and iodide ions from mixed solutions [0.1 m M LiBr + 0.1 (1 – m ) M LiBF 4 ] and [0.1 m M LiI + 0.1 (1 – m )M LiBF 4 ] in dimetylformamide (DMF) with the following fractures m of surface-active anion: 0, 0.01, 0.02, 0.05, 0.1, 0.2, 0.5, and 1 is studied on a renewable liquid (Cd–Ga) electrode by means of an ac bridge. The data on the specific adsorption of Br – and I – anions can be quantitatively described by the Frumkin isotherm, the same as the data on Cl – . It is found that in contrast to Hg/DMF and Bi/DMF interfaces for which the adsorption energy of halide (Hal – ) anions (Δ G ads ) increases with the transition from Cl – to Br – and further to I – , on the (Cd–Ga)/DMF interface, the Δ G ads values increase in the inverted sequence I – < Br – < Cl – . It is found that the energy of (Cd–Ga) interaction with Hal – anions ( Δ G ( Cd-Ga ) − H a l − ) also increases in the sequence I – < Br – < Cl – . The comparative analysis of the results on the Hal – adsorption on the (Сd–Gа)/DMF and (In–Gа)/DNF interfaces shows that the interaction energies metal–DMF and metal–Hal – correlate with one another. For (Cd–Ga) and (In–Ga) electrodes which have virtually the same energy of metal–DMF interaction, the corresponding values of Δ G ( Cd-Ga ) − H a l − and Δ G ( In-Ga ) − H a l − turn out to be close not only for Cl – but also for Br – and I – .