Engineering Abundant Mesopores in FeNC Single-Atom Catalysts via High-Gravity for High-Performance Oxygen Reduction Reaction.

The performance of FeNC single atom catalysts (SACs) is significantly influenced by the porous architecture of their N-doped carbon substrates. Although the pore structure of FeNC SACs has been widely investigated from a chemical methodology perspective, the role of synthesis process engineering has received much less attention. To address this, high-gravity technology is introduced during the precursor preparation stage to achieve intensive molecular mixing. This approach successfully yields FeNC SACs with a well-defined hierarchical micro-mesoporous structure. The resulting catalyst exhibits a narrower mesopore size distribution (4-6 nm), a higher specific surface area (800.3 m2·g-1), and a more positive half-wave potential (0.899 V) for the oxygen reduction reaction (ORR) compared to a reference sample produced in a conventional stirred tank reactor. Density functional theory (DFT) analysis further indicates that the abundant mesopores induce carbon defects, thereby enhancing the intrinsic ORR activity. Moreover, when integrated into a zinc-air battery and an anion-exchange membrane fuel cell, the catalyst delivers high peak power densities of 259.5 and 860 mW·cm-2, respectively, highlighting its potential for practical applications.