The influence of slow Cu(OH) 2 phase formation on the electrochemical behaviour of copper in alkaline solutions

Abstract

Evidences of a slow Cu(OH) 2 phase formation with data resulting from potentiodynamic potentiostatic and rotating-ring-disc techniques were obtained during the anodization of copper in 0.1 M NaOH. According to the potential and time windows employed in the different runs, electrochemical results can be explained by admitting two limiting complex structures of the anodic layers namely Cu/Cu 2O (porous inner layer)/CuO (outer layer) and Cu/Cu 2O (porous inner layer)/CuO/Cu(OH) 2 (outer layer). The formation of the Cu(OH) 2 layer fits a progressive nucleation and 2-D growth under charge transfer control in the −0.175 ⩽ E ⩽ −0.10 V range and an instantaneous nucleation and 2-D growth mechanism under charge transfer control in the −0.20 ⩽ E ⩽ −0.18 V. A well-defined voltammetric peak multiplicity can be distinguished for the electrochemical of each complex anodic layer. These results furnish a reasonable explanation to discrepancies observed in the literature for the electroformation and electroreduction of anodic layers formed on copper in alkaline solutions.