Carbon supported Fe₇₀Co₂₀Ni₁₀ trimetallic catalyst for enhanced cathode performance in Dual-chamber microbial fuel cells for wastewater treatment

Scalable microbial fuel cells (MFCs) for simultaneous wastewater treatment and electricity generation require cost-effective, high-performance cathode catalysts that operate efficiently at neutral pH. Herein, the present study reports a trimetallic Fe₇₀Co₂₀Ni₁₀ alloy nanoparticle catalyst supported on carbon (Fe₇₀Co₂₀Ni₁₀/C) as a highly active and durable oxygen reduction reaction (ORR) electrocatalyst. The catalyst was synthesized via a facile thermal-activation route using sodium borohydride (NaBH4), yielding homogeneous alloy nanoparticles (8–12 nm) with pronounced electron transfer from Fe to Ni, thereby optimizing oxygen adsorption energy and enhancing ORR kinetics. When deployed as a cathode in a dual-chamber MFC at 1.0 mg cm⁻² loading, Fe₇₀Co₂₀Ni₁₀/C delivered a maximum power density of 1532 mW m⁻² and an open-circuit voltage of 0.936 V, and operational stability for over 1100 hours. This configuration also achieved high wastewater treatment efficiency, with 89.7% chemical oxygen demand (COD) removal and 9.7% coulombic efficiency. These findings highlight the superior catalytic and operational performance of Fe₇₀Co₂₀Ni₁₀/C compared with the synthesized mono- and bimetallic Fe, Co, and Ni-based catalysts, suggesting its potential as a cost-effective alternative to precious-metal catalysts for MFC applications for wastewater treatment