An In Situ Raman Spectroscopy Study of the Anodic Oxidation of Copper in Alkaline Media

In situ Raman spectroscopy measurements were made during the anodic oxidation of copper in 1 M and 6 M solutions. The formation of occurs at potentials corresponding to the first anodic voltammetric peak (A1), and a porous layer of composed of fine needle‐like crystals is formed at the second voltammetric peak (A2). The compact underlayer of cuprous oxide is transformed to another species (presumably ) at potentials above 0 mV vs. . At potentials near oxygen evolution, an unidentified trivalent species appears. The reduction of the oxide is shown to be strongly influenced by illumination. Under irradiation, the underlayer is first reduced to at around 0 mV vs. , followed by reduction to copper, and finally reduction to copper metal. Without intense illumination, the p‐type semiconductive properties of the underlying layer make it act as a Schottky barrier, causing the large degree of irreversibility found in this system.