Zinc Electrodeposition from a Deep Eutectic System Containing Choline Chloride and Ethylene Glycol

Deep eutectic electrolytes have recently been considered as alternatives to classical room-temperature ionic liquids. This work is an initial study of the zinc deposition process from a basic choline chloride/ethylene glycol deep eutectic solvent containing ZnCl2 at 30 degrees C. The system was examined by cyclic voltammetry at static and rotating glassy carbon disk electrodes and by potential step techniques. There was little deposition initially on sweeping or stepping the potential to -0.5 to -0.8 V vs Zn/Zn(II), but more rapid deposition was observed when the potential was subsequently raised to -0.4 to -0.2 V. The role of choline chloride was also studied by comparing with a choline-free electrolyte, which exhibited a more conventional voltammetric response. The formation of a dissolved, intermediate species Z on the cathodic sweep was proposed to account for the observed deposition behavior in the deep eutectic. Furthermore, an observation of the electrodeposition behavior with the addition of sodium ethoxide supports the suggestion that Z is a complex of Zn2+ and deprotonated components of the solvent. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3364930] All rights reserved.