Hierarchical N/Se dual-doped porous carbon drives four-electron oxygen reduction for superior efficiency and durability of microbial fuel cells

Microbial fuel cells (MFCs) are eco-friendly energy conversion systems that simultaneously degrade organic matter and convert its chemical energy into electricity. However, a formidable challenge in MFC development is designing efficient and stable catalysts to enhance cathodic oxygen reduction reaction (ORR). Herein, we propose a hierarchical nitrogen and selenium dual-doped porous carbon (NSeC-800) for MFC applications. The NSeC-800 exhibits superior ORR activity and durability, with initial potential of 0.99 V, limiting current density of 6.25 mA cm −2 and 90.1 % retention in neutral electrolyte, surpassing commercial Pt/C (0.95 V, 5.69 mA cm −2 and 70.8 %). The high performance is attributed to the synergism of N/Se doping, creating abundant active sites such as combined pyridinic N and C-Se (p-N/C-Se) within a hierarchical porous structure (1571.3 m 2 g −1 ). Density functional theory calculations reveal the strong adsorption energies of O 2 and ∗OOH (−2.34 and −3.62 eV) on p-N/C-Se sites, facilitating O-O bond cleavage and boosting the four-electron oxygen reduction. In MFCs, NSeC-800 outperforms commercial Pt/C, demonstrating 2.6 times higher maximum power density (1018.7 ± 4.3 mW m −2 ) and 4.5 times longer running time (450 h/period). This work provides a dual-heteroatom doping strategy to construct an efficient and stable electrocatalyst with dominated 4e − pathway for high-performance MFCs. • Hierarchical N/Se dual-doped porous carbon shows high performance and stability. • The synergistic N and Se doping on UiO-66 creates highly active substances. • The enhanced O 2 /∗OOH adsorption on p-N/C-Se sites drives four-electron ORR. • MFC-NSeC delivers a superior power density of 1018.7 ± 4.3 mW m −2 . • MFC-NSeC achieves a COD removal rate of 91.2 % with efficient electron transfer.