Electrochemical deposition of zinc from zinc oxide in 2:1 urea/choline chloride ionic liquid

To overcome the major difficulties involved in the electrodeposition of zinc (Zn) from traditional aqueous solvents, it is important to discover novel electrolytes that are eco-friendly and highly efficient. Zinc oxide (ZnO) was dissolved in eutectic mixture of urea/choline chloride (2:1 molar ratio) at different temperatures (343-373K). Electrochemical measurements confirmed that the onset reduction potential for Zn2+ to Zn occur at ∼-1.05V using cyclic voltammetry. A linear relationship was obtained between cathodic peak current and square root of scan rate, thus indicating the reaction was governed by diffusion-controlled mechanism. Electrodeposition of Zn followed three dimensional (3D) instantaneous nucleation and growth mechanism for various reduction potentials. Scanning electron microscopy (SEM) images showed the formation of hexagonal-shaped Zn particles at lower applied potentials, while plate-like structures of Zn metal were deposited at higher applied potentials. The X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) analysis confirmed the presence of high-pure Zn metal electrodeposits on Cu cathode.