Rotating Ring‐Disk Electrode and Spectroelectrochemical Studies on the Oxidation of Iron in Alkaline Solutions

The investigation of the anodic oxidation of iron in alkaline solutions is important because it is used as a cathodic reaction in Fe/Ni and Fe/air batteries, and it is also related to the corrosion of iron. 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(2) at the least positive anodic CV peak, Fe[sub 3]O[sub 4] at the second peak, [delta]-FeOOH and Fe[sub 2]O[sub 3] at the third peak, and Fe[sub 3]O[sub 4] 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.