Understanding the Deactivation of Fe Single-Atom on Nitrogen-Doped Carbon Catalysts in Oxygen Reduction Reaction

Single-atom catalysts (SACs) have gained attention as potential replacements for the Platinum-Group Metals (PGMs) in the oxygen reduction reaction (ORR), a fundamental reaction in renewable energy technologies. Among SACs, the Fe single-atom nitrogen-doped carbon catalysts (Fe-NxCy) are prominent due to their remarkable activity; however, their long-term stability under operando conditions remains a critical challenge. Here, we show that a carbon atom coordinated to the Fe center can activate and interact with reactive oxygen species, leading to demetallization, through the electronic and structural evolution of the catalyst. In addition, the spin polarization of Fe affects the electron distribution on the intra-orbitals that enhance stability, while axial-orbitals counteract the ligand field effects. These findings provide mechanistic insights into the deactivation of Fe-NxCy moieties and guide the design of robust and sustainable catalysts for energy applications.