Single-atom Fe-decorated N-doped porous carbon from waste biomass as a high-performance air-cathode for wastewater treatment in microbial fuel cells

Microbial fuel cells (MFCs) offer great potential for simultaneous wastewater treatment and energy generation, yet the development of cost-effective and efficient carbon-based cathode alternatives to Pt/C for oxygen reduction reactions remains challenging. This study presents a novel single-atom Fe-decorated N-doped porous carbon (Fe-SA/NBC) synthesized from biogas residue for wastewater treatment. The Fe-SA/NBC demonstrated superior catalytic performance, achieving a kinetic current density of 18.89 mA·cm - ² compared to 10.38 mA·cm - ² for Pt/C, and an enhanced electrochemical surface area with a C dl of 1.81 mF·cm - ² versus 1.76 mF·cm - ² for Pt/C. When integrated into an MFC air-cathode under actual sewage, Fe-SA/NBC outperformed Pt/C, achieving a 22.6 % higher power density (882.92 mW·m - ² vs. 719.81 mW·m - ²), a higher output voltage (0.53 V vs. 0.47 V), and a longer operational duration (3.6 days vs. 3.2 days). Additionally, Fe-SA/NBC exhibited superior removal efficiencies for chemical oxygen demand and ammonia nitrogen during sewage treatment. In practical applications, MFCs equipped with Fe-SA/NBC successfully powered diodes and timers in series-connected configurations. This study introduces an innovative method for producing cost-effective and efficient cathode catalysts from waste biomass, offering significant potential for wastewater treatment and power generation systems.