The degradation of the membrane electrode assembly, originating from microstructural changes in the catalyst layer, inhibits the commercialization of polymer electrolyte membrane fuel cell. In particular, changes in relative humidity during starting/working conditions cause crack growth and propagation within the catalyst layer, but the reason is still not clear. Here, accelerated stress tests are designed from starting conditions (25 ^oC, 45% RH) to working conditions with different RHs (20%, 45% and 99%) at 85 ^oC for different cycles. For low working RH of 20%, no obvious change can be observed, while the accelerated stress test to high working RH induces apparent changes in the catalyst layer structure, with ionomer aggregation and migration leading to crack generation. The obtained results indicated that ionomer migration plays an important role in the structure changes of catalyst layer, suggesting that the design of ionomer with high stability and reliable water retention is necessary to improve the structural stability of the catalyst layer.

膜电极组件的降解源自催化剂层的微结构变化，从而抑制了聚合物电解质膜燃料电池的商业化。特别地，在开始/工作条件期间相对湿度的变化引起裂纹扩展和在催化剂层内的扩展，但是其原因仍不清楚。在这里，加速应力测试的设计范围是从初始条件（25 ^o C，相对湿度45％）到在85 ^o时具有不同RH（20％，45％和99％）的工作条件C为不同的周期。对于20％的低工作RH，没有观察到明显的变化，而对高工作RH的加速应力测试则引起了催化剂层结构的明显变化，离聚物的聚集和迁移导致了裂纹的产生。所得结果表明离聚物的迁移在催化剂层的结构变化中起着重要作用，这表明必须设计具有高稳定性和可靠的保水性的离聚物来提高催化剂层的结构稳定性。