Abstract:The electrochemical deposition of zinc/gold dendrite-free alloys was achieved from deep eutectic solvents based on a mixture of choline chloride and ethylene glycol, without using any additives. Potentiostatic electrodeposition was carried out at relatively low Zn electrodeposition overpotential at different Zn(II) concentrations. Insight into the electrochemical mechanism of the Zn electrodeposition was revealed by cyclic voltammetry (CV) and chrono- amperometry (CA). The morphology and structure of the obtained electrodeposits were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD), while the elemental analysis was determined by energy dispersive spectroscopy (EDS) technique. The CV results showed that Zn electrodeposition commences with zinc underpotential deposition (UPD) and proceeds through the zinc overpotential deposition (OPD) region. The deposition potential of the Zn/Zn(II) couple shifts towards more positive value with increased Zn(II) concentration. CA analysis demonstrated that in the zinc OPD region, 3D progressive nucleation starts, followed by 3D growth of depositing zinc. Morphological analysis revealed that electrodeposition commences with the formation of compact Zn islands and proceeds through dendrite-free zinc/gold alloys formed. A formation of several intermetallics, namely cubic AuZn₃ and AuZn along with metallic zinc were identified by XRD analysis.

Key words: zinc electrodeposition; deep eutectic solvent; zinc/gold alloys; morphology; structure