ROTATING-RING-DISK ELECTRODE AND SPECTROELECTROCHEMICAL STUDIES ON THE OXIDATION OF IRON IN ALKALINE-SOLUTIONS

The electrochemical oxidation of iron has been studied in concentrated alkaline solutions employing rotating ring-disk electrode voltammetric and in situ spectroelectrochemical techniques. While four anodic and cathodic cyclic voltammetric (CV) peaks may be observed at times, three cathodic CV peaks and four anodic peaks are observed under the usual experimental conditions. Results obtained from these studies are consistent with the conclusion that iron is oxidized to Fe(II) at the least positive anodic CV peak, Fe3O4 at the second peak, delta-FeOOH and Fe2O3 at the third peak, and Fe3O4 below the delta-FeOOH layer at the most positive anodic peak. Corresponding cathodic CV peaks were identified for all these anodic processes, except for the most positive one. Evidence supporting the conclusion and detailed mechanisms for the iron oxidation is presented.