Ordered mesoporous carbon with atomically dispersed Fe-Nx as oxygen reduction reaction electrocatalyst in air-cathode microbial fuel cells

Abstract As a renewable energy source, microbial fuel cell (MFC) exhibits a great potential in solution of energy crisis and environmental pollution. The cathode catalyst for oxygen reduction reaction (ORR) is one of the most important factors that can affect the performance of fuel cell. Herein, MOF-derived ordered mesoporous carbon (Fe–N/C) with atomically dispersed Fe-Nx active sites was successfully prepared. It can significantly improve the ORR activity in alkaline, acidic or neutral electrolyte, inspiring us to establish a MFC using it as cathode catalyst. The Fe–N/C-MFC performs great maximum power density (1232.9 mW m−2), high Open Circuit Voltage (0.644 V) and large constant output voltage (0.46 V) which are all superior to that of 20% Pt–C. The ohmic resistance (Rohm) and charge transfer resistance (Rct) of Fe–N/C decrease by 36.2% and 88.7% from 25.4 Ω to 110.6 Ω (N/C) to 16.2 Ω and 12.5 Ω (Fe–N/C), respectively. Note that the Fe–N/C holds an ordered mesoporous structure with the characteristic of Fe-Nx active sites doping, and content of pyridine-like N and graphite-like N are both significantly increased compared with N/C sample. These results make the atomically dispersed Fe-Nx ordered mesoporous Fe–N/C promising for commercial application of MFC.