Unusual anodic peak on negative potential scan for copper in alkaline media①
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Abstract: The unusual anodic peak emerging on negative potential scan for copper in concentrated NaOH media was investigated by X-ray diffraction, X-ray photoelectron spectroscopy techniques, potentiodynamic scan, galvanostatic reduction and fast triangular voltage methods. The results show that CuO is formed on the electrode at potentials above this unusual peak A2,3, but also produced at peak A2,3when copper has been beforehand anodized at high potentials. Longer pre-oxidation time and higher pre-oxidation potential are advantageous to the formation of CuO at peak A2,3. It is presented that the pent-up growth of oxide layer in the high potential region occurs at the interface between metal and oxide by the field-assisted migration of O2-ions to electrode, and when potential negatively shifts to the range of peak A2,3, the O2-(or cation vacancies) accumulated in the film could move towards the solution and combine with Cu2+ions at the interface between oxide and solution.
Key words: copper electrode; anodic film; ion transfer; capacitance