ZnO-Fe-N/C bimetallic electrocatalysts with antibacterial activity for durable oxygen reduction in microbial fuel cells

Abstract

Improving the oxygen reduction reaction (ORR) at the cathode and mitigating biofouling are key to advancing microbial fuel cell (MFC) performance. This study aims to develop a multifunctional cathode catalyst capable of simultaneously promoting ORR activity and suppressing biofilm formation. A dual-metal ZnO-F-N/C electrocatalyst was synthesized via a controlled pyrolysis strategy, enabling the integration of Fe-N_x active sites with antibacterial ZnO components. The optimized ZnO-Fe-N/C-1 exhibits a high half-wave potential of 0.70 V vs. RHE and sustained activity in neutral electrolyte. When deployed as an air cathode in an MFC, ZnO-Fe-N/C-1 achieves a maximum power density of 643.5 ± 23.0 mW m^-2 (J = 1355.7 ± 24.3 mA m^-2), exceeding those of Fe-N/C and commercial 20 wt% Pt/C benchmarks. During wastewater treatment tests, the MFC demonstrates a chemical oxygen demand (COD) removal efficiency of 94.70 ± 0.86% and a coulombic efficiency of 17.95 ± 0.15%. Furthermore, the intrinsic biofouling-resistant nature of ZnO-F-N/C-1 stabilizes long-term MFC operation. This study demonstrates a sustainable catalyst design that integrates high ORR efficiency with durability and biofilm control, offering a promising route toward robust, high-performance MFC systems.