The oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs) is severely hindered by the strong adsorption of sulfonate groups in perfluorinated sulfonic acid (PFSA) ionomers on Pt, which not only blocks the catalytic sites, but also induces dense PFSA films resisting O₂ toward Pt. Herein, we address this issue by incorporating hydroxyphenyl metal porphyrins (MPOHs) as additives in cathodic catalyst layers (CCLs). Detailed physical and electrochemical characterization techniques and molecular dynamics simulations reveal that MPOHs enable ORR-favorable Pt/ionomer interfaces by a dual promotion mechanism, by forming hydrogen-bonding networks with hydronium and sulfonates to break the sulfonate–Pt interaction and enlarge the O₂-diffusive hydrophilic domains in ionomer films, thus enriching and carrying O₂ molecules through adsorption/desorption processes. Consequently, the fuel cells with MPOH-added CCLs exhibit marked reduction in the local oxygen transport resistance of ionomer films and notable improvements in the output power accordingly, with CuPOH, which is suggested by density functional theory calculations as an optimal O₂ carrier due to the near zero O₂ adsorption free energy, showing a more pronounced improvement. These results should inspire more molecule-level strategies to boost PEMFC efficiency through regulating Pt/ionomer interfaces and stimulate the development of electrode optimization-oriented materials in a broad range of application areas of various electrochemical energy technologies.

中文翻译：

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羟基苯基金属卟啉对膜电极组件中 Pt 氧还原的双重促进


质子交换膜燃料电池 （PEMFC） 中的氧还原反应 （ORR） 受到全氟磺酸 （PFSA） 离聚物对 Pt 上磺酸盐基团的强烈吸附的严重阻碍，这不仅阻塞了催化位点，而且还诱导了致密的 PFSA 膜，抵抗 O₂ 朝向 Pt。在本文中，我们通过在阴极催化剂层 （CCL） 中加入羟苯基金属卟啉 （MPOH） 作为添加剂来解决这个问题。详细的物理和电化学表征技术以及分子动力学模拟表明，MPOH 通过与水合氢离子和磺酸盐形成氢键网络来打破磺酸盐-Pt 相互作用并扩大离聚物膜中的 O₂ 扩散亲水结构域，从而富集和携带 O₂，从而通过双重促进机制实现有利于 ORR 的 Pt/离聚物界面分子通过吸附/解吸过程。因此，添加 MPOH 的 CCL 的燃料电池表现出离聚物薄膜的局部氧传输阻力显著降低，输出功率也相应显着提高，密度泛函理论计算表明 CuPOH 是最佳 O₂ 载体，因为 O₂ 接近零吸附自由能，显示出更明显的改善。这些结果应该激发更多的分子水平策略，通过调节 Pt/离聚物界面来提高 PEMFC 效率，并刺激电极优化导向材料在各种电化学能源技术的广泛应用领域的发展。