Numerical investigation of delamination onset and propagation in catalyst layers of PEM fuel cells under hygrothermal cycles

Durability is one of the main obstacles that inhibits the commercialization of polymer electrolyte membrane (PEM) fuel cells for transport applications, in which the microstructure of the catalyst layers (CLs) deteriorates under dynamic loading operation. In this study, CLs’ naturally random porous structure is simplified to be a random three-phase microstructure consisting of ionomers, catalyst agglomerates and pores, and the onset and growth of delamination process between the ionomer and catalyst agglomerate is investigated numerically by considering the catalyst agglomerate as elastic while the ionomer is elasto-viscoplastic, influenced by the cell assembly force arising from the cell clamping and variations in temperature and relative humidity. It is found that increasing clamping stress delays the delamination onset but has marginal effect on delamination propagation. The amplitude of hygrothermal cycles is the dominating factor in delamination and more frequent startup/shutdown of PEM fuel cells alleviates the delamination. Correlation between the rate of plastic strain accumulation in the ionomer and the interface delamination has been observed.