Crafting controllable Fe-based hierarchically organic-frameworks from bacterial cellulose nanofibers for efficient electrocatalysts in microbial fuel cells

One highly hopeful strategy to supply oxygen reduction reaction (ORR) catalysts for microbial fuel cells (MFCs) is the use of supporting substrates to achieve orderly stacking of metal-organic frameworks (MOFs). In this work, a mixed hierarchically porous carbon nanofiber (Fe-NC@CBC) is proposed by in-situ growth of Fe-based MOFs particles on the surface of bacterial cellulose (BC). Its superior electrocatalytic performance originates from the existence of abundant multi-stage pores in the BC substrate and MOFs after pyrolysis, with a specific surface area up to 636.5 m(2)/g. Apart from this, poison tests confirm that Fe-N-x sites and Fe3C species achieve synergistic catalysis. As such, Fe-NC@CBC exhibits a superior ORR half-wave potential (-0.429 V vs. Hg/HgCl2), which exceeds that of commercial Pt/C. Impressively, the MFC equipped with Fe-NC@CBC catalyst achieves a coulombic efficiency of 23.6%, far exceeding 20 wt% Pt/C (12.6%), showing fascinating potential in pollutants degradation and power recovery. Furthermore, the abundant hydroxyl groups on BC tightly anchor the MOFs to the fibers, thus avoiding agglomeration and migration, and ensuring the continuous and efficient occurrence of ORR in MFCs. This work can provide a new perspective for synthesis of low-cost, eco-friendliness and efficient catalysts suitable for MFCs.