Mechanism study of Cu-Zn alloys electrodeposition in deep eutectic solvents

Copper and copper-zinc alloys were electrochemical prepared from Cu2O-ZnO mixed oxides in urea and 1-butyl-3-methylimidazolium chloride deep eutectic solvent at 383 K. The electrochemical reduction and nucleation mechanism of copper and copper-zinc alloys were investigated by cyclic voltammetry and chronoamperometry. Cyclic voltammetry showed that copper species [Cu2ClO center dot urea](-) was reduced to copper at - 0.68 V (vs. Ag), while zinc species [ZnClO center dot urea](-) was reduced to zinc and formed copper-zinc alloy at - 1.8 V (vs. Ag). Chronoamperometry indicated that copper particles were electrodeposited by progressive nucleation with diffusion-controlled growth process in urea-BMIC-Cu2O solutions, and the average diffusion coefficient of copper complex ions was determined to be 2.79 x 10(-8) cm(2) s(-1). On contrast, the electrodeposition of copper-zinc alloy proceeded via combination of 3D instantaneous and progressive nucleation. On the other hand, copper and copper-zinc alloys were electroplated on to a stainless steel substrate and characterized by X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy.