Instantaneous Free Radical Scavenging by CeO₂ Nanoparticles Adjacent to the Fe-N₄ Active Sites for Durable Fuel Cells

To achieve the Fe-N-C materials with both high activity and durability in proton exchange membrane fuel cells, the attack of free radicals on Fe-N-4 sites must be overcome. Herein, we report a strategy to effectively eliminate radicals at the source to mitigate the degradation by anchoring CeO2 nanoparticles as radicals scavengers adjacent (Sca(ad-CeO2)) to the Fe-N-4 sites. Radicals such as (OH)-O-center dot and HO2 center dot that form at Fe-N-4 sites can be instantaneously eliminated by adjacent CeO2, which shortens the survival time of radicals and the regional space of their damage. As a result, the CeO2 scavengers in Fe-NC/Sca(ad-CeO2) achieved similar to 80 % elimination of the radicals generated at the Fe-N-4 sites. A fuel cell prepared with the Fe-NC/Sca(ad-CeO2) showed a smaller peak power density decay after 30,000 cycles determined with US DOE PGM-relevant AST, increasing the decay of Fe-NCPhen from 69 % to 28 % decay.