Anodic Oxidation of Copper in Alkaline Solutions: I . Nucleation and Growth of Cupric Hydroxide Films

The anodic oxidation of copper in LiOH solution has been investigated by galvanostatic, potentiostatic, and voltammetric sweep techniques. The structure and composition of the films were determined by x-ray and electron diffrac-tion, and by scanning electron microscopy. Cu(OH)2 forms in two layers: a base layer grown by a solid-state mechanism and an upper layer of individual crystals nucleated and grown from solution. The size and number of upper layer crystals are dependent on electrode potential. More anodic potentials produce a large number of randomly deposited crystals, whereas less anodic potentials result in fewer, more highly developed crystals. Increased stirring results in a greater loss of material into solution, and in the extreme, nu-cleation and growth are completely prevented. For sufficiently low crystalliza-tion rates, produced galvanostatically, the thermodynamical ly stable phase, CuO, is formed. At higher rates the formation of Cu(OH)2 dominates. A nu-cleation and growth mechanism is given and discussed with reference to other