An Investigation of the Anodic Behavior of Copper and Its Anodically Produced Oxides in Aqueous Solutions of High pH

Abstract

The cyclic voltammetry of copper in base is particularly complex as not only are metal/metal oxide, e.g., , and oxide/oxide, e.g., [and/or ], transitions involved but there are also dissolution processes, and at least one of the oxides, , is poorly conducting, and two of the oxidation products of copper can exist in both anhydrous and hydrated forms. The reduction process in particular is complicated by the fact that with thick films, which tend to be duplex in character, the outer layer of Cu(11) material is frequently unable to react until the inner layer of poorly conducting is reduced. Furthermore, when the outer layer of hydrous Cu(11) oxide reduces the reaction apparently involves a Cu(1) hydrous oxide intermediate or by‐product; this Cu(11) reduction process gives rise to a separate peak, , for the latter being determined by the Cu/Cu(1) hydrous oxide equilibrium, below that for the reaction. The conditions required to produce a thick oxide film on copper in base by the potential cycling technique were investigated. While thick films of the Cu(1) hydrous oxide were not observed, this material, at quite low coverage, is believed to be an important intermediate or mediator in a variety of anodic reactions at copper electrodes in solutions of high pH.