N-doped Activated Carbon-Supported Cu-Fe-Zn-Ni-Co High-Entropy Alloy Electrocatalyst: Improved ORR in Microbial Fuel Cells

Abstract Microbial fuel cells (MFCs) enable simultaneous wastewater treatment and energy recovery; however, their performance is primarily limited by sluggish oxygen reduction reaction (ORR) kinetics at the cathode. In this work, a non-precious metal-based electrocatalyst i.e., Cu-Fe-Zn-Ni-Co (CFZNC) high-entropy alloy (HEA) supported on nitrogen (N)-doped activated carbon powder (ACP) was synthesized and evaluated for ORR activity. CFZNC-HEA/N-ACP exhibited excellent ORR performance with E onset and E 1/2 of 1.12 V and 0.82 V vs RHE, respectively, and high selectivity towards a four-electron ORR pathway, indicating direct reduction of O 2 to H 2 O. It delivered the highest open-circuit potential (0.85 V), outperforming CFZNC (0.62 V) and N-ACP (0.21 V) alone as an MFC cathode. The superior performance is attributed to synergistic multi-metal active sites in HEA nanoparticles and N-doped porous carbon support, which enhance ORR kinetics and reduce cathodic overpotential. These results highlight the potential of nobel metals-free cost-effective HEA-based cathodes for advancing MFC electrocatalysis.