Electrocatalytic reduction of dioxygen by cobaltporphyrin in aqueous solutions

The electrocatalytic reduction of dioxygen by Co(TTFP)(Y)(2) {Y=H2O or HO-} is investigated by cyclic voltammetry, spectroelectrochemistry, hydrodynamic voltammetry at a glassy carbon electrode in dioxygen-saturated aqueous solutions. Electrocatalytic reduction of dioxygen by Co-II(TTFP)(Y)(2) establishes a pathway of 2e(-) reduction to form hydrogen peroxide, and then the generated hydrogen peroxide is reduced to water by Co-I(TTFP)(Y)(2) at more negative potential. Co-II(TTFP)(Y)(2) may bind dioxygen to produce the adduct complex [Co-II-O-2 or Co-III-O-2(-.)] which exhibits a Soret band at 411 nm and Q band at 531 nm.