Evaluation of Cu-Doped FeO Nanoparticles Synthesized via Green Method as High-Performance Cathode Catalysts for PEM Fuel Cells

This study reports the green synthesis of FeO and 5 wt.% Cu-doped FeO nanoparticles using fig leaf extract and their application as cathode catalysts in proton exchange membrane fuel cells (PEMFCs). Structural analyses indicated the formation of crystalline FeO nanoparticles with an average size of approximately 4 nm, while Pt–FeO/C and Pt–CuFeO/C catalysts exhibited smaller particle sizes of 2 nm. BET analysis revealed a significant increase in surface area from 54.4 m²g⁻¹ (Pt–FeO/C) to 185.1 m²g⁻¹ (Pt–CuFeO/C), accompanied by an increase in electrochemically active surface area (ECSA) from 97 to 213 m²g⁻¹_Pt upon Cu incorporation. Durability tests over 250 CV cycles showed that Pt–CuFeO/C retained 73% of its ECSA, compared to 29% for Pt–FeO/C, suggesting improved structural stability. Single-cell PEMFC evaluations demonstrated that catalyst performance was temperature-dependent. The Pt–CuFeO/C catalyst achieved a current density of approximately 250 mAcm⁻² at 70°C under PEMFC operating conditions, whereas Pt–FeO/C reached 212 mAcm⁻² at 60°C but showed decreased performance at higher temperatures.