High performance flow through microbial fuel cells with anion exchange membrane

Microbial fuel cells (MFCs) can be limited to low power densities due to impacts of localized pH on electrode performance. Acidification of the anodic biofilm limits current generation by bacteria and the increase in cathode pH due to the oxygen reduction reaction reduces the whole cell potential. In this study, an anion exchange membrane (AEM) was used to make a membrane electrode assembly (MEA) in an MFC, with the anode, AEM, and cathode close together to enhance hydroxide ions transport from cathode to anode to minimize pH imbalances and reduce electrode spacing. With a flow-through felt anode the MFC produced 5.7 ± 0.4 W m⁻² (at 29 ± 1 A m⁻², internal resistance of 7.2 ± 0.6 mΩ m², based on cross sectional area), which is one of the highest power densities produced in an MFC using a 50 mM phosphate buffer (PBS). Reducing the flowrate of the anolyte or air past the cathode decreased performance. Increasing the buffer concentration to 100 mM produced a maximum power density of 7.1 ± 0.4 W m⁻², the highest power density ever recorded for an MFC, demonstrating the importance of buffer concentration in maintaining favorable localized pHs.