Electrochemical transformation of Fe-N-C catalysts into iron oxides in alkaline medium and its impact on the oxygen reduction reaction activity

Precious metal-free Fe-N-C catalysts efficiently electrocatalyze the oxygen reduction reaction both in acid and alkaline electrolyte. Their stability is however limited acidic medium, but generally accepted to be much higher Herein, by combining advanced electron X-ray based techniques, we provide comprehensive evidence of a Fe dissolution/reprecipitation mechanism, which partially transforms single atoms into oxide nanoparticles carbide [email protected] shell nanoparticles, independent on gas atmosphere used during accelerated stress tests. Our work shows that materials zero-valent should designed so all are protected defect-free graphite shell, for improved durability. For atom catalysts, present study raises question possible synergy between minute amount Fe-NxCy single-atom sites, leading apparent durability this catalyst.