The electrodeposition of metals and alloys from the room-temperature aluminum chloride 1-methyl-3-ethylimidazolium chloride molten salt

The electrochemistry of cobalt, copper, nickel, and zinc was investigated in the room-temperature Lewis acidic aluminum chloride-1-methyl-3-ethylimidazolium chloride molten salt (AlCl;The controlling factors behind the formation of aluminum-transition metal alloys at potentials where aluminum metal is normally thermodynamically unstable were investigated. Because alloy formation was only observed when the work function of the transition metal was significantly greater than that of aluminum, it was concluded that there is a free energy advantage for alloy formation that makes alloy formation thermodynamically favorable at potentials positive of the Al(III)/Al couple. The mutual solubility of the transition metal and aluminum may also play a role in determining which may form alloys at underpotentials.;The fundamental aspects of the electrodeposition of aluminum, cobalt, copper, nickel, and zinc were investigated on both metallic and nonmetallic substrates. The electrodeposition of aluminum, copper, nickel, and zinc on polycrystalline metallic substrates was dominated by underpotential deposition phenomena, and the underpotential shifts were found to correlate linearly with the differences in work functions of the substrate and the electrodeposited metal according to the classical prediction of Kolb and Gerischer.;The electrodeposition of cobalt, nickel and zinc on glassy carbon was found to be an overpotential-driven nucleation process involving island growth according to the Volmer-Weber mechanism. The experimental dimensionless current-time transients that resulted from chronoamperometry experiments suggested a mechanism involving progressive three-dimensional nucleation and hemispherical diffusion-controlled growth of the metal deposits. Analysis of the overpotential dependence of the nucleation rate constant per active site according to the atomistic theory of nucleation suggested that active sites on the glassy carbon substrate probably serve as critical nuclei.