Electrochemical Investigation Of Aerobic Biocathodes At Different Poised Potentials: Evidence For Mediated Extracellular Electron Transfer

Microbial Fuel Cells (MFCs) are a promising new technology for the conversion of organic wastes to electrical energy. They work by oxidising organics at the anode using bacteria, and combining this with the Oxygen Reduction Reaction (ORR) at the cathode. Pt and other chemical catalysts have been used at the cathode in MFCs. However, their high cost and issues with long term stability could limit their application in MFCs. To have a more sustainable MFC system, one idea is to use aerobic bacteria to catalyse the ORR at the cathode, which would make the MFC technology cheaper and more robust. Carbon electrodes modified with these bacteria lower the overpotential required for ORR, but little is understood about the organisms that constitute these biofilms and their mechanisms of electron transfer. In the current work, mixed communities of biofilms catalysing the ORR were grown in electrochemical half-cells poised at potentials of +200mV and -100mV vs Ag/AgCl and the electrochemical behaviour of these biofilms was studied using Cyclic Voltammetry (CV). These investigations suggest a shift in the mechanism of Extracellular Electron Transfer (EET) as the potential changes.