Voltammetric behaviour of nickel in base with particular reference to thick oxide growth

The formation of anodic oxide films on nickel surfaces in base was investigated using cyclic voltammetry. The formation and reduction of a Ni(II) species was observed at low potentials, about 0–0.3 V (RHE). Potential/pH studies indicated that the initial oxypecies formed in this region were anionic. The reduction of such a layer was shown to occur in a significantly different manner, evidently a postelectrochemical restructuring of the initially deposited species occurred via a field-assisted, place-exchange type reaction. Conversion of terminal O− to bridging (Ni−O−Ni) oxygen species at the surface evidently resulted in a changeover from an anionic to a neutral layer. The results are discussed by analogy with recent data for gold and platinum. A much thicker hydrous film was produced by repetitive potential cycling. The influence of sweep-rate, sweep-limits, solution temperature, and base concentration on the growth and charge storage behaviour of this type of layer was invegtigated.