Electrodeposition of cobalt and zinc-cobalt alloys from a lewis acidic zinc chloride-1-ethyl-3 methylimidazolium chloride molten salt

The electrodeposition of cobalt and zinc-cobalt alloys on nickel, tungsten, copper, and glassy carbon electrodes was investigated in 40.0-60.0 mole percent (mol%) zinc chloride-1-ethyl-3-methylimidazolium chloride molten salt containing cobalt(II) at 80 degreesC. At potentials positive of 0.15 V (vs. Zn), cobalt deposition on nickel occurs via three-dimensional instantaneous nucleation with diffusion controlled growth of the nuclei. At potentials between 0.1 and 0.0 V, underpotential deposition of zinc on cobalt occurs. At potentials more negative than - 0.1 V, bulk zinc deposition takes place via three-dimensional instantaneous nucleation with mixed diffusion and kinetic controlled growth. The zinc content of the Zn-Co alloys was found to vary nonlinearly with the deposition potential. X-ray diffraction measurements indicate that the Zn-Co deposits with a low zinc content may be amorphous and the crystalline nature of the Zn-Co electrodeposits increases as the zinc content of the deposits increases. Addition of propylene carbonate co-solvent to the melt solution decreases the melting temperature of the solution and enables the electrodeposition to be performed at 40 degreesC. (C) 2001 Elsevier Science Ltd. All rights reserved.