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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 H 2 O 2 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 H 2 O 2 at a production rate of 117 mg H 2 O 2 /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 H 2 O 2. • A sluggish MFC caused voltage reversal with significant anode overpotential. • Replacing Pt-coated cathode with carbon gas diffusion electrode induced cathodic voltage reversal. • Cathodic voltage reversal shifted 0.5 V of anode overpotential to the cathode. • H 2 O 2 was produced in the stacked MFC at cathodic voltage reversal. [ABSTRACT FROM AUTHOR]

Conventionally, both a working and counter electrode are housed in a single cell to form an electrochemical device for quantification of various analytes. For reductive sensing of hydrogen peroxide, however, analyte losses due to oxidation and catalytic decomposition on the counter electrode are significant, rendering such devices unsuitable for continuous monitoring of analyte concentration changes over time. Further, only chemically inert materials such as platinum can be used to construct the counter electrode, where their high cost limits potential applications. To circumvent such issues, an anion-exchange membrane was employed to fabricate a two-chamber device housing each electrode in each individual chamber, to physically prevent the counter electrode from interfering with working electrode analysis. Such a design enables the use of sacrificial anodes as the counter electrodes, thereby significantly expanding the linear range of detection, improving sensitivity, and reducing device cost. [ABSTRACT FROM AUTHOR]