The Local Changes in the Physicochemical Properties during Electrode Reactions in a Chlorocuprate Ionic Liquid

The physicochemical and electrochemical properties of an ionic liquid consisting of the dichlorocuprate anion, [CuCl 2 ] – , were investigated. The equimolar mixture of CuCl and 1-butyl-1-methylpyrrolidinium chloride (BMPCl) was found to yield an ionic liquid at 298 K composed predominantly of BMP + and [CuCl 2 ] – . Fine deposits of metallic Cu were obtained on a glassy carbon electrode by potentiostatic and galvanostatic reduction of [CuCl 2 ] – in CuCl-BMPCl (50.0–50.0 mol%). The overpotential for Cu nucleation was larger on a glassy carbon electrode than on a Pt electrode. The electrochemical deposition and dissolution of Cu were analyzed using an electrochemical quartz crystal microbalance. The local viscosity and density of the electrolyte near the electrode/electrolyte interface increased during both deposition and dissolution of Cu, probably reflecting the shift in the electrolyte composition to the local basic and acidic conditions, respectively.