Comparative study of Cl-, Br-, and I- ions adsorption from dimethyl formamide at Hg- and Ga-electrodes

The adsorption of Cl-, Br-, and I- ions from their 0.1 M solutions in dimethyl formamide at renewable liquid Hg- and Ga-electrodes was studied under similar experimental conditions by the differential-capacitance and jet-electrode methods. The data obtained points out to a strong effect of the metal nature on adsorption parameters and the halogenide-ion surface activity series. The halogenide-ion surface activity at the Hg-electrode increased in the following sequence: Cl- < Br- < I-; at the Ga-electrode, in the reverse sequence: I- < Br- < Cl-. The results are explained qualitatively in terms of the Andersen-Bockris model. It follows from the obtained data that (1) the free energy of the metal-halogenide-ion interaction increases in the following sequence: I- < Br- < Cl-; (2) the free energy of the Ga-halogenide-ion interaction exceeds that of the Hg(-)halogenide-ion interaction; and (3) the difference of the Cl-, Br-, and I- ions interaction with the metals increased significantly when passing from Hg- to Ga-electrode.