Pt alloy electrocatalysts (e.g., Pt₃Co) for oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs) have attracted a great deal of interest from worldwide researchers in past decades, due to the excellent ORR activity and cost-effective properties. However, the long period operation would yield sever dissolution of the non-precious metal which effects the ionomer microstructure, thus leading to significantly decreased ORR activity of catalyst and aggravated of the oxygen transport resistance in cathode catalyst layers (CCLs), especially the local oxygen transport resistance caused by the ultrathin ionomer film covering on catalyst surface. Herein, in this paper, the effects of Co²⁺ contamination on structure of ionomer films and the corresponding local oxygen transport behavior in CCLs are explored via physicochemical characterizations and molecular dynamics (MD) simulations, limiting current method, as well as fuel cell performance measurement. It is found that Co²⁺ contamination reduces water content and increases the modulus of the ultrathin ionomer film, while reducing the distance between the sulfonic acid groups and increasing the aggregation size of the ionomer, which is related to the volume of hydrophilic domains. Additionally, the electrochemical measurement results demonstrate that as the degree of Co²⁺ contamination increases from 0 to 85 %, the local oxygen transport resistance increases from 27.74 s cm⁻¹ to 42.43 s cm⁻¹, and the peak power density of fuel cell reduces from 510 mW cm⁻² to 453 mW cm⁻². The reason behind lies on that contaminated Co²⁺ tends to connect with sulfonate, then suppress the ionomer mobility and dislocate the local oxygen transport channels.

用于质子交换膜燃料电池 (PEMFC) 中氧还原反应 (ORR) 的Pt 合金电催化剂（例如 Pt ₃ Co）由于其优异的 ORR 活性和成本效益，在过去几十年中引起了全世界研究人员的极大兴趣特性。然而，长时间运行会导致非贵金属的严重溶解，从而影响离聚物微观结构，从而导致催化剂的ORR活性显着降低，并加剧阴极催化剂层（CCL）的氧传输阻力，尤其是局部氧由覆盖在催化剂表面的超薄离聚物膜引起的传输阻力。在此，在本文中，Co ^2+的影响通过物理化学表征和分子动力学 (MD) 模拟、限流法以及燃料电池性能测量，探索了离子聚合物薄膜结构的污染和 CCL 中相应的局部氧传输行为。发现Co ²⁺污染降低了水含量并增加了超薄离聚物膜的模量，同时减少了磺酸基团之间的距离并增加了离聚物的聚集尺寸，这与亲水域的体积有关。此外，电化学测量结果表明，随着Co ²⁺污染程度从0增加到85 %，局部氧传输阻力从27.74 s cm ^-1增加到42.43 s cm^-1，燃料电池的峰值功率密度从510 mW cm ^-2降低到453 mW cm ^-2。其背后的原因在于受污染的Co ²⁺倾向于与磺酸盐连接，从而抑制离聚物的迁移率并使局部氧传输通道错位。