Induction of cathodic voltage reversal and hydrogen peroxide synthesis in a serially stacked microbial fuel cell

We developed an innovative strategy to address the inhibition of anode-respiring bacteria due to voltage reversal in serially stacked microbial fuel cells by inducing cathodic voltage reversal and H₂O₂ production. When platinum-coated carbon (Pt/C) cathodes were employed (stacked MFC_Pt/C) and the MFC was operated with acetate medium, the last unit (MFC 4) caused a voltage reversal of -0.8 V with a substantial anode overpotential of 1.22 V. After replacing the Pt/C cathode with a Pt-free carbon gas diffusion electrode in MFC 4, an electrode overpotential, approximately 0.5 V, was shifted from the anode to the cathode, inducing cathodic voltage reversal. Under cathodic voltage reversal, MFC 4 generated H₂O₂ at a production rate of 117 mg H₂O₂/m²-h. Hence, under cathodic voltage reversal induced by Pt-free cathodes, due to less anode polarization, the anode-respiring activity can largely be sustained in a stacked MFC that treats organic wastewater consistently and the quality of treated wastewater may be improved with energy-efficient and on-site generated H₂O₂.