Shift of voltage reversal in stacked microbial fuel cells

Abstract

We proved that sluggish kinetics on the cathode and the imbalance of cathode kinetics cause voltage reversal in a stacked microbial fuel cell (MFC) equipped with a non-Pt cathode. Catholyte aeration to a unit MFC against passive air diffusion to the cathode in the other unit MFC shifted voltage reversal between the two units, due to improved mass transport and O-2 concentration effects in the aerated MFC. The shifted voltage reversal returned to an original status when catholyte aeration was stopped. A Ptcoated cathode increased the rate of oxygen reduction reaction (ORR) by a factor of similar to 20, as compared to the non-Pt cathode. As a result, the anodic reaction rate that became slower than the rate on the Ptcathode limited current density to overpotential in the stacked MFC equipped with the Pt-cathode. This work shows that dominant kinetic bottlenecks, which are the primary cause of voltage reversal, can be shifted between individual MFCs of stacked MFCs or electrodes depending on relative kinetics. (C) 2014 Elsevier B.V. All rights reserved.