Dynamic hydrogen buffer integrated with single Pt sites for enhanced durability of high-temperature proton exchange...

The performance degradation caused by current reversal during start-up/shut-down (SU/SD) in proton exchange membrane fuel cells (PEMFCs), particularly severe in high-temperature PEMFCs (HT-PEMFCs), is conventionally mitigated by strategies that significantly increase system complexity and cost. In this work, the Co nanoparticles encapsulated by graphene layer supported Pt single atoms (Pt₁/Co@N-C) catalyst is employed enhance the durability of membrane electrode assemblies (MEA) under SU/SD situations. The Pt₁/Co@N-C catalyst with ultralow Pt loading exhibits a comparable hydrogen oxidation reaction (HOR) activity compared to the Pt/C catalyst, and a suppression of oxygen reduction reaction (ORR) activity. Notably, the encapsulated Co nanoparticles with an fcc crystal structure act as the hydrogen buffer, the storage/escape of H₂ in the lattice interstices of Co metal can effectively resist current reversal of the MEA. The Pt₁/Co@N-C with ultralow Pt loading (35 μg_Pt cm^-2) displays an outstanding performance in the HT-PEMFCs, achieving a peak power density of 555 mW cm^-2 and a stability of 54 μV h^-1. The catalyst demonstrates a markedly enhanced durability compared to the Pt/C catalyst during SU/SD, and improves the resist current reversal time to 50 min (Pt/C, 2 min) under fuel starvation condition. This work presents innovative strategies for developing anode catalyst with low Pt loading and superior durability in HT-PEMFCs.