KINETICS OF THE ELECTROREDUCTION OF ANODICALLY FORMED CADMIUM-OXIDE LAYERS IN ALKALINE-SOLUTIONS

The kinetics of the potentiostatic electroreduction of cadmium oxide l ayers on polycrystalline cadmium electrodes have been investigated in 0.01 - 1.0 M NaOH solutions. The study was undertaken to determine the influence of passive film formation conditions on the electroreductio n process of the anodically produced hydrous cadmium hydroxide-oxide l ayers. By properly adjusting the electroreduction conditions the catho dic potentiostatic current transients can be satisfactorily described by a nucleation and growth mechanism involving the participation of so luble Cd(II) and passivating anodic species. Experimental data were an alysed by the application of non linear least squares fit routines. Fr om the parametric identification procedure coherent potential dependen cies of the corresponding fitting parameters as well as reasonable val ues of the physicochemical constants included in the reaction model, h ave been obtained. In this way it is possible to correlate kinetic dat a of the electroreduction process of the anodic oxide layers to make a discrimination between the different mechanistic contributions to thi s complex reaction involving several steps.