A study of the initial stages in oxidation of copper in alkaline solutions

Abstract

The split ring-disc electrode technique has been used to investigate the formation of Cu 2O upon copper metal in 1 M sodium hydroxide solution at 30°C. Particular attention has been paid to the initial stages of film formation prior to the formation of bulk Cu 2O. The results indicate that the initial step in the oxidation of copper in alkaline solutions is simultaneous formation of discrete nuclei of Cu(I) surface species on the electrode and a soluble Cu(I) species which is generated directly from the copper metal. This is followed by the growth and coalescence of the Cu(I) surface nuclei and formation of the initial monolayers, which progressively block off the dissolution sites on the electrode surface. The flux of the soluble Cu(I) species to the half rings therefore never reaches the theoretical value predicted for a free dissolution process.