Interfacial reactivity and oscillating behavior of chalcopyrite cathodes during H2O2 reduction. II. Characterization of electrode corrosion

The electrochemical behavior of CuFeS2 in alkaline medium has been investigated with cyclic voltammetry and XPS techniques. The oxidation processes preceding the dissolution peak are surface transformations leading presumably to CuS, Fe(OH)3, and S, which may be reduced back to chalcopyrite at moderate negative potentials. Similar investigations performed on CuFeS2 cathodes after H2O2 reduction in alkaline medium show the occurrence, in the latter polarization experiments, of oxidative corrosion processes of a chemical nature. The corrosion products remaining on the surface consist mainly of CuO and Fe2O3 · xH2O; sulfur is converted into soluble oxidized species, as shown by residual traces of SO3 = and SO4 =. It is shown that the current wave observed in the voltammograms of H2O2 reduction, and the related oscillating phenomena, are associated with the release of Cu(II) following the corrosion processes. The amount of corrosion during H2O2 reduction has been evaluated by examining the electrode surface with voltammetry and EDX microanalysis. Corrosion varies with the potential at which a given cathodic charge is passed and is maximum at potentials in the region of the current wave. It increases substantially when the current flows under oscillating conditions.