Metal corroles as electrocatalysts for oxygen reduction

The rotating ring disk electrode method has been used to study O-2 electroreduction with metal corroles. Catalysis begins at potentials that are 0.5-0.7 V more positive than the expected potential of the M-III/II couple based on studies in non-aqueous solutions. The path of O-2 reduction depends on the nature of the metal ion. Cobalt corroles promote O-2 reduction to H2O2. Iron corroles catalyse O-2 reduction via parallel two- and four-electron pathways, with a predominate four-electron reaction. The rate constants for the individual O-2 reduction paths are given at pH 7. Mechanisms are proposed on the basis of pH dependence, inhibition studies, and Tafel slopes. An imidazole-tailed iron corrole catalyses H2O2 disproportionation analogous to catalase.