Mitigating Fe–N–C Catalyst Degradation Using Organic Radical Scavengers

Atomically dispersed iron–nitrogen–carbon (Fe–N–C) catalysts are promising catalyst candidates for the cathodic oxygen reduction reaction in hydrogen fuel cells, owing to their high activity and cost-effectiveness. However, their practical application is hindered by rapid degradation. Here, we demonstrate that introducing organic molecules with suitable physicochemical properties into acidic electrolytes can act as reactive oxygen species (ROS) scavengers, thereby mitigating the degradation of Fe–N–C catalysts. We systematically investigate five organic molecules─methanol, ethanol, isopropanol, tert -butanol, and dimethyl sulfoxide (DMSO)─which vary in molecular size, viscosity, and radical scavenging kinetics, using three types of Fe–N–C catalysts with distinct porous architectures. High-viscosity scavengers (e.g., isopropanol and tert -butanol) impair the catalytic activity of Fe–N–C catalysts. More importantly, the compatibility between the molecular size of the scavenger and the pore structure of Fe–N–C catalysts proves to be a dominant factor over the scavenging effect. Specifically, DMSO, due to its larger molecular size, adversely affects the Fe–N–C catalyst rich in micropores (Fe–N–C–microP), but effectively protects the mesoporous variant (Fe–N–C–mesoP) and the catalyst with active sites on carbon black particle surface (Fe–N–C–CB). These findings offer valuable guidelines for the rational selection of organic ROS scavengers to enhance the durability and long-term performance of Fe–N–C catalysts in fuel cell applications.