Electrodeposition of Zinc from the Lewis Acidic Aluminum Chloride‐1‐Methyl‐3‐ethylimidazolium Chloride Room Temperature Molten Salt

Abstract

The electrodeposition of zinc on polycrystalline gold, platinum, and tungsten and on glassy carbon was investigated in the 60.0–40.0 mole percent aluminum chloride‐1‐methyl‐3‐ethylimidazolium chloride molten salt containing electrogenerated zinc (II). The electrodeposition of zinc on all of the polycrystalline metal electrodes was preceded by underpotential deposition processes similar to those reported previously during studies carried out in aqueous solutions. The underpotential shift was found to vary linearly with the difference in the work functions of zinc and the metallic substrate. In contrast, the electrodeposition of zinc on glassy carbon required a substantial nucleation overpotential. Dimensionless chronoamperometric current‐time transients for the electrodeposition of zinc on this substrate were in good accord with the theoretical transients for the limiting case of progressive three‐dimensional nucleation with hemispherical diffusion‐controlled growth of the nuclei. Analysis of the nucleation kinetics by using the atomistic theory of nucleation suggested that active sites on the glassy carbon surface played the role of critical nuclei during the initial stages of the deposition process. The formal potential of the Zn(II)/Zn couple at 40°C was found to be vs. the Al(III)/Al couple in pure melt, and the diffusion coefficient of zinc(II) was determined to be .