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

Abstract

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).