Separator electrode assembly (SEA) with 3-dimensional bioanode and removable air-cathode boosts microbial fuel cell performance

Separator electrode assemblies (SEAs) were designed by associating a microbial anode with an air-cathode on each side of three different kinds of separator: plastic grid, J-cloth and baking paper. The SEA was designed to allow the air-cathode be removed and replaced without disturbing the bioanode. Power densities up to 6.4 W m−2 were produced by the Grid-SEAs (on average 5.9 ± 0.5 W m−2) while JCloth-SEAs and Paper-SEAs produced 4.8 ± 0.3 and 1.8 ± 0.1 W m−2, respectively. Power densities decreased with time mainly because of fast deterioration of the cathode kinetics. They always increased again when the air-cathodes were replaced by new ones; the Grid-SEAs were thus boosted above 4 W m−2 after 7 weeks of operation. The theoretical analysis of SEA functioning suggested that the high performance of the Grid-SEAs was due to the combination of several virtuous phenomena: the efficient pH balance thanks to free diffusion through the large-mesh grid, the likely mitigation of oxygen crossover thanks to the 3-dimensional structure of the bioanode and the possibility of overcoming cathode fouling by replacing it during MFC operation. Finally, the microbial community of all bioanodes showed stringent selection of Proteiniphilum acetatigenes in proportion with the performance. •The separator membrane assembly with a grid as the separator performed the best.•Efficient pH balance by diffusion of the buffering species is essential.•Oxygen crossover was mitigated by the biofilm on the cathode and the 3D bioanode.•Biofouling did not impact the resistance; fouling deteriorated the cathode kinetics.•All bioanodes showed stringent selection of Proteiniphilum acetatigenes.