Highly conductive skeleton Graphitic-C3N4 assisted Fe-based metal-organic frameworks derived porous bimetallic carbon nanofiber for enhanced oxygen-reduction performance in microbial fuel cells

Abstract

Rational design and assembly of metal-organic frameworks (MOFs) is an effective strategy to develop high-performance electrocatalysts for oxygen reduction reaction in the microbial fuel cells (MFCs). In this work, a novel strategy to fabricate hierarchically porous bimetallic-carbon nanofibers (Mn–Fe@g-C3N4) via pyrolyzing Mn-doped g-C3N4 assisted Fe-based MOFs (MIL-101) is proposed. The Mn–Fe@g-C3N4 exhibits superior oxygen reduction reaction (ORR) onset potential (0.393 V vs. Ag/AgCl) and half-wave potential (−0.042 V vs. Ag/AgCl) under neutral condition, exceeding the state-of-the-art Pt/C catalyst. Mn–Fe@g-C3N4 displays a direct four-electron-transfer pathway, excellent stability and methanol tolerance in alkaline media. Mn–Fe@g-C3N4 cathode exhibits the ohmic resistance (8.07 Ω) and charge transfer resistance (5.44 Ω), which is slightly lower than Pt/C catalyst. Mn–Fe@g-C3N4 catalyst is an outstanding air-cathode in MFC with a power density of 413 ± 7 mW m−2, outperforms the MFC with 20 wt% Pt/C catalyst (333 ± 9 mW m−2). The outstanding catalytic activity for Mn–Fe@g-C3N4 is mainly due to 3D interconnected porous architectures, highly conductive framework and the synergistic effects between nitrogen and metal ion center. The present work not only provides an efficient conductive-skeleton-assisted synthetic strategy to construct high-performance electrocatalyst, but also improves the electrochemical performance of MOF-derived materials for practical MFCs application.