Fe Single-Atom Catalysts on MOF-5 Derived Carbon for Efficient Oxygen Reduction Reaction in Proton Exchange Membrane Fuel Cells

The development of Fe single-atom catalysts (Fe SACs) with abundant, accessible Fe sites is a key step toward enhancing the efficiency of the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs). In this study, Zn4O(1,4-benzenedicarboxylate)(3) (MOF-5), which has a 3D microporous cubic structure, is used as the precursor to prepare highly-porous carbon (denoted as C-MOF-5) with an ultrahigh specific surface area (2751 m(2) g(-1)) and high external surface area (1651 m(2) g(-1)). C-MOF-5 is demonstrated as an effective carbon support to yield Fe SAC-MOF-5 with a large amount of accessible FeNx sites (2.35 wt%). Fe SAC-MOF-5 delivers a half-wave potential of 0.83 V (vs RHE) in a 0.5 m H2SO4 electrolyte, and achieves a peak power density of 0.84 W cm(-2) in a 0.2 MPa H-2-O-2 PEMFC. This excellent performance originates from the ultrahigh specific surface area of C-MOF-5 for the formation of a high density of single Fe atoms, and high external surface area for the increased exposure of active sites. This work may inspire the rational design of metal single-atom catalysts derived from a wider range of MOF precursors with ultrahigh specific area to improve the performance of the oxygen reduction reaction in PEMFCs.