The degradation of cathodic Fe/N/C catalyst in PEMFCs: The evolution of remanent active sites after demetallation

The state-of-the-art Fe/N/C catalyst has presented comparable initial cathode performance to the bench-mark Pt/C catalyst in proton exchange membrane fuel cells (PEMFCs). However, the major bottleneck is its significant activity decay in real-world PEMFC cells. The superposed fast decay and slow decay have been well documented to describe the degradation process of Fe/N/C catalysts during PEMFC operation. The fast decay has been well understood in close relation to the demetallation at the initial 15-h stability test. Nevertheless, it is still unclear how the remanent active sites evolve after demetallation. To this end, the catalyst performance and evolution of a typical Fe/N/C active site were herein investigated through postmortem characterizations of the membrane electrode assemblies (MEAs) after different operations. It is presented that 1 bar pressure and 80 & DEG;C temperature are the optimized conditions for Fe/N/C MEA. Particularly, the fast decay in the initial 15 h is immune to the various operating parameters, while the slow decay highly depends on the applied temperature and pressure. According to the X-ray absorption spectra (XAS) analysis and stability test of MEA, the gradual evolution of Fe-N coordination to Fe-O is found correlated with the slow decay and accounts for the catalyst decay after the demetallation process.& COPY; 2023 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

Automated summary

The state-of-the-art Fe/N/C catalyst shows comparable initial performance to Pt/C catalysts in PEMFCs, but experiences significant activity decay. The fast decay is related to demetallation, while the slow decay is influenced by temperature and pressure. XAS analysis reveals the evolution of Fe-N coordination to Fe-O, which explains the catalyst decay after demetallation.