Optical Visualization of Fluid Flow during Electrodeposition of Zn Deposits at the Interface between Two Immiscible Liquids

Fluid flow around an n-butyl acetate / aqueous ZnSO4 interface was visualized using Schlieren method and Mach-Zehnder interferometry during Zn electrodeposition. Results showed that fluid flows were introduced into both the organic liquid and the electrolyte solution after applying potential. The fluid flow observed in the organic liquid was considered to be attributable to the temperature increase by Joule heating at the growth front during Zn electrodeposition. However, the fluid flow observed in the electrolyte solution was considered to be attributable to electro-osmotic flow and Marangoni convection. We speculated that the vigorous fluid flow attributable to electro-osmotic flow and Marangoni convection in the electrolyte solution can enhance Zn2+ transportation to the growth front of Zn deposits, producing rapid and preferential growth along the liquid-liquid interface.