Rational Design of Fluorine-Modified High-Loading Cu–N–C Single-Atom Catalysts via Molecular Confinement for Enhanced Oxygen Reduction Reaction

Atomically dispersed transition-metal–nitrogen–carbon (TM–N–C) catalysts have emerged as promising candidates for the oxygen reduction reaction (ORR) due to their exceptional atomic utilization, tunable electronic structure, and high catalytic selectivity. Nevertheless, achieving a high-content metal loading while suppressing aggregation during high-temperature pyrolysis remains a critical challenge. Herein, we propose a confinement strategy to synthesize fluorine (F) and nitrogen (N) codoped porous carbon-supported copper single-atom catalysts (F-CuNC) with ultrahigh metal loading. The hyperbranched copper phthalocyanine precursor (H-CuPc) serves as a molecular scaffold to spatially isolate Cu species, effectively mitigating their thermal migration and aggregation. The resultant F-CuNC catalyst exhibits a remarkable Cu loading of 9.83 wt %, highlighting the synergistic confinement effect of the precursor architecture and heteroatom codoping. Electrochemical evaluation reveals that F-CuNC delivers robust ORR activity with a half-wave potential of 0.84 V vs. RHE and a limiting current density of 6.31 mA cm –2, outperforming the F-free counterpart (CuNC) by 60 and 1.56 mA cm –2, respectively. Furthermore, the introduction of electronegative F atoms adjacent to Cu–N–C moieties optimizes the electronic structure of the active sites, thereby enhancing both ORR kinetics and durability. After a 10 h accelerated degradation test by chronoamperometry, F-CuNC retains 83.1% of its initial current density, whereas CuNC degrades by 75.4%. This work not only advances the synthesis of high-loading single-atom catalysts through molecular confinement and heteroatomic modulation but also provides insights into designing robust TM–N–C systems for energy conversion applications.