The development of highly efficient and durable electrocatalysts for the oxygen reduction reaction (ORR) is critical for advancing proton exchange membrane fuel cells (PEMFCs) technology. Herein, a novel CoPc-S-COF/CNT hybrid was fabricated by integrating a robust 2D dithiine-linked phthalocyaninato cobalt (CoPc)-based covalent organic framework (CoPc-S-COF) on carbon nanotubes (CNTs) as a superior ORR electrocatalyst. The CoPc-S-COF was synthesized from hexadecafluorophthalocyaninato cobalt and 1,2,4,5-benzenetetrathiol to ensure robust conjugation. The in situ growth on functionalized CNTs was specifically tailored to boost electrical conductivity and stability. The resulting CoPc-S-COF/CNT hybrid exhibits exceptional acidic ORR activity with a half-wave potential of 0.79 V vs. reversible hydrogen electrode, a limiting current density of 6.12 mA cm-2 and remarkable long-term stability (8 mV decay after 5000 cycles), comparable to commercial Pt/C. When implemented in a practical PEMFC, the CoPc-S-COF/CNT cathode achieves a peak power density of 1153.9 mW cm-2 at 200 kPa H2/O2 condition, outperforming most reported non-precious metal catalysts. In situ Fourier-transform infrared spectroscopy together with density functional theory calculations reveals that the dithiine bridge optimizes the electronic structure of Co-N4 active sites, lowering the energy barrier for *OOH intermediate formation. This work offers new insights into designing COF/CNT hybrids for high-performance energy conversion devices.
Jiang et al. (Wed,) studied this question.