Specific adsorption of chloride ions from 0.1m M LiCl + 0.1(1 − m) M LiClO4 mixed solutions in dimethyl formamide on liquid Ga electrode

Abstract

The differential capacitance curves were measured with an ac bridge in the Ga/[DMF + 0.1m M LiCl + 0.1(1 − m) M LiClO4] system 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 large positive charges of Ga electrode, at which it remains ideally polarizable (up to 12 μC/cm2). It is found that the data on the specific adsorption of Cl− anion in the system can be quantitatively described by the Frumkin’s isotherm. The free energy of Cl− ion adsorption ΔGads is a quadratic function of electrode charge. It is shown that, on the Ga electrode, the transition from N-methyl formamide to dimethyl formamide is accompanied by a significant increase in the free adsorption energy ΔGads. In view of a stronger Ga-DMF interaction as compared with Ga-(N-MF), this result can be explained only by the corresponding decrease of salvation energy of chloride ion.