The electrodissolution of magnetite: Part I. The electrochemistry of Fe3O4/C discs-potentiodynamic experiments

A simple technique is reported for the preparation of Fe₃O₄ compact electrodes by cold pressing of powdered magnetite admixed with carbon. The electrochemical behaviour of these compacts was shown to be similar with that of polycrystalline magnetite in respect of their potentiodynamic polarisation response. The variation of rest potential with solution composition is complex and indicates that there is oxidation of the surface to Fe₂O₃. Linear potentiodynamic polarisation curves are reported corresponding to unit concentration of ions for the pH range 3–9. The results provide evidence of an electrode process which is an irreversible single electron redox reaction. The current passing through the electrode is generally controlled by a solid-state diffusion process. It is postulated that the diffusing species is the H⁺ ion.