CeO2 Nanoparticles Boosted Fe‐N‐C Sites Derived from Dual Metal Organic Frameworks toward Highly Active and Durable Oxygen Reduction Reaction

The durability improvement of Fe‐N‐C electrocatalysts toward acidic oxygen reduction reaction (ORR) remains a grand challenge. H2O2 seriously degrades Fe‐N‐C sites, which account for a major origin of the low durability. Herein, the growth of hemin decorated zeolitic imidazole framework (hemin‐ZIF 8) on preformed Ce‐1,3,5‐benzenecarboxylic acid (Ce‐BTC) metal organic frameworks (MOFs) is reported. Interestingly, the resultant dual MOFs appear to be Ce‐BTC nanorods decorated with many hemin‐ZIF 8 dodecahedral nanocrystals, well resembling rice panicles. After pyrolysis, CeO2 nanoparticles are evenly distributed in carbonized nanorods and abundant Fe‐N‐C sites are embedded in shrunk dodecahedra, labeled as Fe‐N‐C‐CeO2. Fe‐N‐C‐CeO2 exhibits a high ORR activity in terms of a half wave potential (E1/2) of 0.800 V (vs RHE). The high ORR activity is closely correlated with the well exposure of Fe‐N‐C sites. In addition, the presence of CeO2 leads to a low H2O2 yield of Fe‐N‐C‐CeO2 (2.3%), much lower than that of Fe‐N‐C (4.3%) by itself in the absence of CeO2. After 5000 potential cycling, the E1/2 of Fe‐N‐C‐CeO2 degrades 15 mV superior to that of Fe‐N‐C (42 mV). Moreover, a single cell with Fe‐N‐C‐CeO2 as cathode degrades much slower than that of Fe‐N‐C (28 000 s vs 7200 s) during chronoamperometric measurements.