In this study, porous components of a proton exchange membrane (PEM) fuel cell, i.e., single-layer gas diffusion layer (GDL, carbon paper), double-layer GDL (microporous layer (MPL) deposited carbon papers), and catalyzed electrodes, are subjected to 60 repetitive freeze-thaw cycles between −40 °C and 30 °C under water-submerged conditions; and their morphological and microstructural characteristics are investigated at each 15 cycles and compared with those of virgin materials. The results indicate that consecutive cycling of temperature causes different degradation patterns in different components. The single-layer GDL shows a unique degradation mechanism, in which macro-scale pores volumetrically expand, and relatively small-scale hollows and cracks form on the polymeric binder and carbon fiber interfaces, respectively. For the double-layer GDL, large-scale surface cracks form on the MPL surface after 15 cycles, and the morphology and microstructure degradation gains momentum with the formation of these cracks, and upon completion of 30 cycles, large-scale carbon/hydrophobic agent flakes start to detach from the surface. For the catalyzed electrodes, due to their inherently cracked surface, the catalyst layers (CLs) degrade first through expansion of the cracks in the in- and through-plane directions, and then through swelling and agglomeration of the ionomer; and combination of these two patterns triggers detachment of large CL flakes from the surface, negatively affecting the microstructure.

在这项研究中，质子交换膜（PEM）燃料电池的多孔组件，即单层气体扩散层（GDL，碳纸），双层GDL（微孔层（MPL）沉积的碳纸）和催化电极在浸水条件下，在−40°C和30°C之间经受60次重复的冻融循环；并在每15个循环中研究其形态和微观结构特征，并与原始材料进行比较。结果表明，温度的连续循环在不同的组件中导致不同的降解模式。单层GDL显示出独特的降解机理，其中宏观尺度的孔体积膨胀，并且在聚合物粘合剂和碳纤维界面上分别形成相对较小尺度的空洞和裂缝。对于双层GDL，15个循环后在MPL表面形成了大规模的表面裂纹，随着这些裂纹的形成，形貌和微结构的退化得到了动力，并且在完成30个循环后，大规模的碳/疏水剂薄片开始从表面脱离。对于催化电极，由于其固有的破裂表面，催化剂层（CLs）首先通过裂纹在平面内和贯通平面方向上的膨胀，然后通过离聚物的溶胀和附聚来降解；然后通过离子键的膨胀和附聚来降解。这两种模式的组合会触发大的CL薄片从表面分离，从而对微观结构产生负面影响。在完成30个循环后，大规模的碳/疏水剂薄片开始从表面脱离。对于催化电极，由于其固有的破裂表面，催化剂层（CLs）首先通过裂纹在平面内和贯通平面方向上的膨胀，然后通过离聚物的溶胀和附聚来降解；然后通过离子键的膨胀和附聚来降解。这两种模式的组合会触发大的CL薄片从表面分离，从而对微观结构产生负面影响。在完成30个循环后，大规模的碳/疏水剂薄片开始从表面脱离。对于催化电极，由于其固有的破裂表面，催化剂层（CLs）首先通过裂纹在平面内和贯通平面方向上的膨胀，然后通过离聚物的溶胀和附聚来降解；然后通过离子键的膨胀和附聚来降解。这两种模式的组合会触发大的CL薄片从表面分离，从而对微观结构产生负面影响。