Iron azaphthalocyanine electrocatalysts for enhancing oxygen reduction reactions under neutral conditions and power density in microbial fuel cells

Highly catalytic cathodes for oxygen reduction reactions under neutral conditions allow major improvement in the power output of microbial fuel cells (MFCs). This work reports iron azaphthalocyanine impregnated into oxidized multi-walled carbon nanotubes to form a molecularly synthesized non-precious metal electrocatalyst. The synthesized catalyst was characterized using a rotating ring and disk electrode in a neutral medium (pH = 7.4) and exhibited a four-electron transfer pathway. When incorporated as a cathode in a two-chamber MFC assembly, the electrocatalyst achieved a power density of 1.54 W/m2 and a current density of 10.7 A/m2, which was 27 % higher than a commercial platinum‑carbon catalyst. In addition, the MFC loading of the molecular catalysts reached over 80 % COD removal efficiency. This work demonstrates that the use of an electrocatalyst based on the FeN4 structure and efficient electron-withdrawing nitrogen improves the application of MFCs in low-cost wastewater treatment and the generation of electricity from wastewater.