Carbon nanofiber/graphene hybrids anchoring Fe, N, and S heteroatoms simultaneously enhancing extracellular electron transfer and biofilm adhesion in microbial fuel cells

The fairly low power density, mainly resulting from poor electroactive bacterial (EAB) adhesion and the sluggish extracellular electron transfer (EET) at the anode interface, constrains the practical implementation of microbial fuel cells (MFCs). Therefore, the properties of the anode material are considered to be a crucial factor for the long-term operational performance of MFCs. In order to enhance the power production performance of MFCs, an aerogel composed of Fe, N, and S co-doped carbon nanofibers (CNFs) and reduced graphene oxide (rGO) was employed as a high-performance anode material by electrospinning, high-temperature pyrolysis and freeze-drying. The doping of Fe, N and S elements induced the formation of abundant reactive sites on the CNFs, which enhanced the electrochemical performance of the anode and the EET process. The huge electroactive area of the samples facilitated the formation of dense biofilms. Therefore, an MFC with the FeS/Fe3C@NCNFs/rGO-modified anode achieved a maximum power density of 2792.56 mW m-2 and the highest output voltage of 0.658 V, both of which were significantly higher than those of the carbon cloth anode (773.97 mW m-2 and 0.443 V). Considering the great improvement in power production, it has considerable potential as a low-cost but high-performance anode material for MFCs. The aerogel structure composed of FeS/Fe3C@CNFs and rGO has a 3D stereoscopic structure, which can provide sufficient sites for biofilm attachment and nutrient transportation, facilitating the improvement of MFC power density.