High performance reduction of H₂O₂ with an electron transport decaheme cytochrome on a porous ITO electrode

A decaheme cytochrome MtrC from Shewanella oneidensis MR-1 immobilized on an ITO electrode displays unprecedented H2O2 reduction activity. Although MtrC showed lower peroxidase activity in solution compared to horseradish peroxidase, the ten heme cofactors enable excellent electronic communication and a superior activity on the electrode surface. A hierarchical ITO electrode enabled optimal immobilization of MtrC and a high current density of 1 mA cm⁻² at 0.4 V vs SHE could be obtained at pH 6.5 (E_onset = 0.72 V). UV−visible and Resonance Raman spectroelectrochemical studies suggest the formation of a high valent iron-oxo species as the catalytic intermediate. Our findings demonstrate the potential of heme-proteins to catalyze technologically relevant reactions and establish MtrC as a new benchmark in biotechnological H₂O₂ reduction with scope for applications in fuel cells and biosensors.