硫酸銅溶液中でのCu₂O相の陰極還元機構

銅陽極不働態化の研究 (第1報)

抄録

A simple electrochemical method has been established to detect a Cu₂O phase present or newly formed on the surface of a copper anode.Utilizing this technique, a study has been extended to investigate conditions which allow this oxide phase to form during anodization.
A well-defined peak corresponding to the reduction of a Cu₂O phase appears on the cathodic voltammetric curve provided a sufficiently fast potential-sweep rate is employed (i.e., <0.6 V/min). This reduction reaction proceeds through the following three sequential steps;{Cu₂O+2e-→2Cu°+O^2- (electron transfer)
Cu²+O^2-→CuO (rate-determining)
CuO+H₂SO₄→CuSO₄+H₂O (following reaction)
The overall cathodic reacton is expressed by,
Cu₂O+Cu²⁺+2^e-→2Cu°+CuO
and its equilibrium potential as calculated from the Nernst's equation based on the present experimental conditions is-0.42V vs. Hg/Hg₂ SO₄, which coincides very well with the experimental value.
Various anodizing conditions were given to a pure Cu anode, and analysis of the results indicates that a Cu₂0 phase only forms when the copper anode is passive.