Fatigue crack propagation behavior of fuel cell membranes after chemical degradation

Abstract

The durability of fuel cells is significantly impaired by chemical and mechanical degradations of perfluorosulfonic-acid membranes. However, how the mechanical degradation, especially the fatigue crack propagation behavior, is impacted by chemical degradation is not clear. In this paper, the fatigue crack propagation behavior of Nafion 212 and Nafion XL composite membranes after chemical degradation are investigated. The fluoride release rates of Nafion 212 and Nafion XL membrane are 0.335 and 0.095 μmol cm−2 h−1, respectively. Likewise, the fatigue crack propagation rate of Nafion 212 membrane is also larger, which is attributed to two fatigue crack propagation mechanisms induced by chemical degradation, including bubble collapsing and pore interconnecting. By contrast, the fatigue crack propagation mechanism of Nafion XL membrane is not significantly changed where chemical degradation only accelerates crack growth in exterior surface layers. These findings provide new insights into the failure mechanisms under combined chemical and mechanical degradations.