A Ring-Disk Electrode Study of the Electrochemical Reduction of Copper(II) in 0.2M Sulfuric Acid on Platinum

Current-potential curves of Cu(ll) in 0.2M H₂SO₄ at a platinum disk electrode show three reduction processes during the cathodic potential scan and three oxidation processes during the anodic potential scan. Two of the reduction (and oxidation) processes are associated with the formation (and removal) of a monolayer of zero-valent copper in contact with the platinum surface. At potentials more negative than 0 V, Cu(ll) is reduced to a bulk copper metal deposit with the concurrent production of some Cu(l). Oxidation of the bulk copper deposit produces primarily Cu(ll) and some Cu(l). Bulk copper cannot be deposited until the platinum surface is covered with zero-valent copper.