Dithiine-Linked Metalphthalocyanine Framework on Carbon Nanotubes for Efficient and Stable Proton Exchange Membrane...

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.