Initial stages of electrocrystallization of nickel, iron and nickel-iron alloy on a glassy carbon electrode in an electrolyte based on a eutectic mixture of choline chloride and ethylene glycol

Abstract

The kinetics and mechanism of the initial stages of electrocrystallization of nickel, iron and nickel-iron alloy were characterized for the process of electrolytic deposition from a solution based on deep eutectic solvent ethaline (liquid mixture containing choline chloride and ethylene glycol at a molar ratio of 1:2, respectively). The theoretical model developed by Scharifker and Hills was used to interpret the obtained experimental data. It was shown that the electrodeposition of nickel and iron obeys the patterns of three-dimensional instantaneous and progressive nucleation, respectively. It was concluded that the formation of iron nuclei occurs at a significantly lower rate than in the case of nickel. The kinetics of the initial stages of Ni–Fe alloy deposition obeys the mechanism of instantaneous nucleation. Thus, in the case of electrolytic deposition from ethaline-based solutions on a glassy carbon electrode, nickel imposes on iron not only its own region of electrode potentials where alloy deposition occurs, but also the type of mechanism of nucleation in the course of codeposition.