Effect of Copper Ion and Water on Anodic Dissolution of Metallic Copper in a Deep Eutectic Solvent (DES)

This report presents influence of water and copper salt on the anodic dissolution of metallic copper in a eutectic solvent of choline chloride and ethylene glycol (DES) in a 1 : 2 molar ratio. The mechanism of copper dissolution anodically was investigated using anodic linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS). Atomic force microscope (AFM) was used to examine the morphology and topography of the surface after electrochemical dissolution course. The addition of 1, 4, 8, 16 and 20 vol% of water cause pitting and has no significant impact on the electrochemical behavior, in particular the shape of anodic linear sweep voltammetry remains unchanged. The more profound effect was seen from the microscopic analysis. The addition of 0.1 and 0.81 M CuCl2 into this eutectic solvent resulted in relatively high resistance at the interfacial region where charge transfer occurs during anodic dissolution of metallic copper using impedance responses. The results confirmed that water will not affect anodic dissolution behavior and the chemistry of dissolution in the deep eutectic solvent.