Impacts of bubble defects in proton exchange membranes on fuel cell performance and durability

The proton exchange membrane (PEM) is a critical component of PEM fuel cells, which is typically fabricated by casting an ionomer dispersion on a substrate and then annealing the remaining ionomer film after solvent evaporation. Due to the high viscosity of the ionomer dispersion, gas bubbles of various sizes may get lodged within the dispersion during the casting process, and some of these bubbles may even persist after annealing. To improve the understanding of the tolerance of PEM bubbles and their impact on the fuel cell performance and durability, we fabricated NafionTM PEMs with intentionally infused air bubbles with different sizes and quantities for fuel cell testing and evaluation against pristine, bubble-free PEMs. The results show that bubbles embedded in the PEM significantly reduce fuel cell performance and durability. In addition, the tensile strength of PEMs with bubbles is discovered to be lower than that of pristine PEMs. A burst test reveals that the failure cross-pressure of PEMs with bubbles is one magnitude lower than for pristine PEMs, suggesting heightened sensitivity to pressure differentials in PEMs containing bubbles. Overall, the low tolerance of membrane bubbles is deemed critical for production of robust fuel cells.