Modification of Nafion's nanostructure for the water management of PEM fuel cells
Modification of Nafion's nanostructure for the water management of PEM fuel cells
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DOI：
10.1002/pol.20220774
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发表时间：
2023-03
影响因子：
3.4
通讯作者：
Yuanchao Li;Natalie L. Schwab;R. Briber;J. Dura;T. Nguyen
中科院分区：
文献类型：
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作者：
Yuanchao Li;Natalie L. Schwab;R. Briber;J. Dura;T. Nguyen
具有阴极催化剂层（CL）的Nafion离聚物相的PEM燃料电池在热压过程中暴露于热的干燥气体，在整个电流密度范围内表现出改善的性能，并且在80°C下使用加湿空气时峰值功率增加约220%。这种增强的性能归因于在MEA的热压过程中CL中全氟磺酸（PFSA）离聚物层的改性结构。高于玻璃化转变温度（Tg）的干燥气体暴露导致离子基团聚集以保留残余水分子。该过程将离聚物分离成离子基团富集域和离子基团稀疏域。离子基团稀疏结构域创建了疏水性界面和反应物传输通道，具有较低的水含量，从而在离聚物中具有较高的氧溶解度。因此，水不饱和离聚物及其表面疏水性分别增强了燃料电池极化曲线的动力学控制区域和浓度极化区域。通过接触角测量和XPS分析了离聚物层的表面疏水性。低于Tg的疏水效果的持久性通过煮沸经处理的材料来证明。用上述加湿气体暴露再处理疏水样品最终表现出亲水性特征，进一步证明了离子基团分布的可操纵性。
A PEM fuel cell with the Nafion ionomer phase of the cathode catalyst layer (CL) that was exposed to hot dry gas during the hot‐pressing process showed improved performance over the whole current density range and ~ 220% peak power increase with humidified air at 80°C. This enhanced performance is attributed to the modified structure of the perfluorosulfonic acid (PFSA) ionomer layer in the CL during the MEA's hot‐pressing process. The dry gas exposure above the glass transition temperature (Tg) results in the aggregation of the ionic groups to retain the residue water molecules. This process separates the ionomer into ionic‐group‐rich domains and ionic‐group‐sparse domains. The ionic‐group‐sparse domains create hydrophobic interface and reactant transport channels with lower water content and thus higher oxygen solubility in the ionomer. Accordingly, the water‐unsaturated ionomer and its surface hydrophobicity enhance the kinetic‐controlled and concentration‐polarized regions of the fuel cell polarization curve, respectively. The surface hydrophobicity of the ionomer layer is analyzed by the contact angle measurement and XPS. The durability of the hydrophobic effect belowTgis demonstrated by boiling the treated material. Re‐treating the hydrophobic sample with humidified gas exposure aboveTgeventually exhibits hydrophilic features, further proving the manipulability of the ionic group distribution.