Cr single-atom catalysts on electrospun carbon nanofibers with enhanced activity and durability for oxygen reduction in microbial fuel cells

M/N/C-based single-atom catalysts (SACs) attract significant attention for oxygen reduction reactions (ORR), with Fe-Nx SACs demonstrating the highest activity. However, the Fenton reaction between iron-based catalysts and H 2 O 2 causes carbon matrix oxidation and corrosion, leading to stability issues. In this work, ZIF-8 serves as a substrate for anchoring Cr atoms, producing Cr-Nx/C SACs with low Fenton reaction activity through pyrolysis. To enhance Cr-Nx activity and further suppress the Fenton reaction, the carbon matrix is carefully engineered. Electrospinning technology uniformly distributes Cr-Nx/C as a functional structure on carbon nanofibers, resulting in Cr-Nx/C@CNF SACs. During pyrolysis, Zn volatilization from ZIF-8 generates numerous mesoporous structures that precisely connect to the catalytic active sites. The spatial network structure formed by the carbon nanofibers further contributes to the hierarchical porous carbon nanostructure of Cr-Nx/C@CNF SACs. The optimized Cr-Nx/ [email protected] catalyst exhibits excellent ORR activity, with a half-wave potential of 0.739 V vs. RHE. More importantly, the introduction of Cr-Nx and the optimized carbon matrix effectively suppress the Fenton reaction, improving stability. Furthermore, microbial fuel cells (MFCs) using Cr-Nx/ [email protected] as the cathode catalyst achieve a power density of 674.98 mW/m 2 and demonstrate superior durability, outperforming commercial Pt/C catalysts.