Anodic deposition of γ-FeOOH layers on inert metal electrodes

Abstract The anodic oxidation of Fe 2+ ions in neutral and alkaline solutions was studied by using a gold or platinum rotating disk electrode in the region of limiting currents. The reaction occurs with the quantitative deposition on the base metal of a ferric oxyhydroxide (γ-FeOOH). The effects introduced by the different experimental variables on the limiting currents are reported. The kinetic contributions of the mass transport and of the subsequent reaction steps are individually examined. It is proposed that the reaction scheme involves the coupling of two diffusion steps occurring in solution within the Levich layer and across the thickness of the deposited oxide. These two reaction steps are kinetically connected by the ion transport of Fe 2+ ions across the interfacial potential difference; this latter reaction step is considered to introduce the pH dependence of the overall reaction.