Electrocatalytic reduction of dioxygen on the surface of glassy carbon electrodes modified with dicobalt diporphyrin complexes

The electrocatalytic reduction of dioxygen has been studied by cyclic voltammetry at glassy carbon electrodes (GCEs) modified with four different dicobalt diporphyrin complexes in dioxygen-saturated aqueous solutions. The electroreduction of O2 on modified GCEs is irreversible and diffusion-controlled. Under the catalysis of these metallodiporphyrins, dioxygen reduces to hydrogen peroxide via a two-electron process. The results reveal that the geometric conformation of diporphyrins determines whether dioxygen is reduced by a four-electron process to water or via a two-electron change to hydrogen peroxide.