Mitigation of mechanical membrane degradation in fuel cells – Part 2: Bonded membrane electrode assembly

Repetitive hygrothermal fluctuations cause mechanical membrane degradation in fuel cells, which requires mitigation for longevity. Part 1 of this work demonstrated that gas diffusion layers (GDLs) with low surface roughness can improve lifetime by reducing harmful buckling phenomena during wet/dry cycling. As a second novel mitigation approach in the present work (Part 2), the catalyst coated membrane (CCM) is bonded with the GDLs to eliminate relative motion and further curb mechanical degradation. A custom miniaturized fuel cell fixture is used within a laboratory-based X-ray computed tomography system to visualize the membrane degradation process during wet/dry cycling. Compared to a non-bonded baseline cell, membrane buckling is shown to be completely arrested with bonding and lead to a two-fold increase in lifetime. Membrane crack development is still observed as the key failure mode, preceded by cathode catalyst layer fracture. However, the root causes are related to bonding irregularities and compressive impingement of GDL fibers rather than membrane buckling. Complementary finite element simulations of a representative fuel cell assembly are carried out to fundamentally establish the favorable effect of improved CCM-GDL adhesion on membrane durability. Overall, the improved adhesion of the bonded cell provided substantial mitigation against fatigue-driven mechanical membrane degradation and failure.