Incorporation of CeF₃ on single-atom dispersed Fe/N/C with oxophilic interface as highly durable electrocatalyst for proton exchange membrane fuel cell

Herein, we demonstrate a bottom-up synthetic method resulting in a nanocomposite which consist of cerium fluoride (CeF₃) embedded in iron-nitrogen-doped porous carbon (Fe/N/C) utilizing fluorination and ammonia annealing. High-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) combined with X-ray absorption spectroscopy (XAS) verifies that the Fe species are present as Fe-N₄ coordination at an atomic level in the CeF₃-Fe/N/C catalyst. A high-spin Fe³⁺-N₄ configuration in the nitrogen-doped carbon revealed by ⁵⁷Fe Mössbauer spectrum and X-ray absorption spectroscopy for Fe L-edge, which will contribute to the oxygen reduction reaction (ORR) activity in acid electrolyte. CeF₃ embedded into the structure of Fe/N/C not only form the oxophilic interface, but also regulate the surface chemical state of Fe and Ce species as well as boosting ORR in acidic solution. The presence of Ce³⁺ sites at the CeF₃-Fe/N/C hybrid catalyst could enhance the O₂ adsorption capability and promote H₂O₂ reducing to water efficiently, thus greatly improve of the electrochemical performance and durability of Fe/N/C catalyst is demonstrated in proton exchange membrane fuel cell (PEMFC).