Increase life time and performance of Microbial Fuel Cells by limiting excess oxygen to the cathodes

The cathodes of MFCs are the main bottleneck for practical application; undesired cathode biofilms often cause their breakdown. The goal of this study was to extend cathode life time. Membranes were applied on the air side of the cathodes to limit oxygen penetration and reduce biofilm formation. Two single chamber MFC designs with an electrode spacing of 120 mm (HRT ∼1 week) and 15 mm (HRT 24 h) were investigated in batch operation using a synthetic blackwater at room temperature (23 ±3 °C). At high electrode spacing cathode life time was increased to 217%, with a significantly increase in power densities over time. The Power densities at 15 mm electrode spacing reached 1155 ± 41 mW m−2 with the membrane applied; compared to 460 ± 32 m Wm−2 without membrane. TOC degradation relative to the anode surface at close electrode spacing was near equal at 6.8 ± 2.3 and 7.2 ± 3.0 gm−2 d−1; however, the Coulomb Efficiency with a membrane increased from 28 ± 10% to 54 ± 13%. CV analysis after operation showed considerably higher ORR activity of the cathodes covered by a membrane.