The Local Changes in the Physicochemical Properties during Cu Electrodeposition in an Ionic Liquid Composed of [CuCl₂]^–

The equimolar mixture of CuCl and 1-butyl-1-methylpyrrolidinium chloride (BMPCl) was found to yield an ionic liquid composed predominantly of BMP + and [CuCl 2 ] – . Fine deposits of metallic Cu were obtained by potentiostatic reduction of [CuCl 2 ] – in CuCl-BMPCl (50.0-50.0 mol%). The change in the local physicochemical properties near the electrode during the electrodeposition of Cu was analyzed using electrochemical quartz crystal microbalance. The resonance resistance of a quartz crystal electrode increased with an increase in the local viscosity near the electrode, probably reflecting the change in the composition of the electrolyte.