In the field of proton exchange membrane fuel cells (PEMFCs), short-side-chain (SSC) ionomers are widely considered to enhance the catalytic activity of the catalyst layer, but the mechanism of enhancement is controversial. In this work, the density functional theory (DFT) calculations and practical membrane electrode assemblies (MEAs) experiments were performed to explore the mechanism of the improved catalytic activity by SSC ionomers. The interactions between Pt representative crystal planes and low-molecular-weight model anions/PFSA fragments were investigated by DFT calculations, which revealed and divided the effects of sulfonic groups, ether groups, and side-chain structures on the adsorption energy and adsorption state. The calculations showed that the ether group of the short side chain has difficulty in interacting with the Pt surface, while the ether group around the midpoint of the long side chain could still interact with the platinum. Therefore, the ionomers having longer side chains more strongly block ORR. In practical catalyst layers, the SSC ionomer significantly improved the MEA performance especially at high voltages, and increased the rated power density by up to 56.3% compared with conventional Nafion®. This work provides a reference for developing desirable ionomers to enhance the catalytic activity of PEMFC catalyst layers.

中文翻译：

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短侧链离聚物提高PEMFC催化剂层催化活性的机理研究：聚焦离聚物/Pt界面


在质子交换膜燃料电池（PEMFC）领域，短侧链（SSC）离聚物被广泛认为可以增强催化剂层的催化活性，但增强的机制存在争议。在这项工作中，通过密度泛函理论（DFT）计算和实际膜电极组件（MEA）实验来探索SSC离聚物提高催化活性的机制。通过DFT计算研究了Pt代表晶面与低分子量模型阴离子/PFSA片段之间的相互作用，揭示并划分了磺酸基、醚基和侧链结构对吸附能和吸附状态的影响。计算表明，短侧链的醚基难以与铂表面相互作用，而长侧链中点周围的醚基仍能与铂发生相互作用。因此，具有较长侧链的离聚物更强烈地阻断ORR。在实际催化剂层中，SSC离聚物显着提高了MEA性能，尤其是在高电压下，与传统Nafion®相比，额定功率密度提高了高达56.3%。该工作为开发理想的离聚物以增强质子交换膜燃料电池催化剂层的催化活性提供了参考。