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

Abstract

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-N₄ 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-N₄ sites. Radicals such as ⋅OH and HO₂ ⋅ that form at Fe-N₄ 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 ∼80 % elimination of the radicals generated at the Fe-N₄ 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-NC_Phen from 69 % to 28 % decay.

Keywords: CeO2 nanoparticles; free radicals; fuel cells; oxygen reduction reaction; scavenger.