Optimization of gradient catalyst layers for enhancing performance and durability of PEMFCs

Cathode catalyst layer (CCL) is the key components in the Proton exchange membrane fuel cells (PEMFCs). This work investigates the impact of platinum (Pt) gradient and ionomer gradient in the CCL on the performance and durability of PEMFCs. A multi-scale model is developed to simulate the performance and degradation of PEMFCs. Using artificial neural networks (ANN) and genetic algorithms (GA), we determine the optimal gradient structural parameters of CCLs. The results indicate that, in contrast to the CCL optimization without considering Pt degradation, the optimal Pt loading should be reduced from the gas diffusion layer (GDL) side to the membrane (MEM) side when Pt degradation is considered (positive Pt gradient), for alleviating concentration loss and Pt degradation. The optimal ionomer gradient should decrease from the MEM side to the GDL side (negative ionomer gradient), which can alleviate the degradation of the Pt distributed on the GDL side by increasing the Pt2+ concentration in the local ionomer to inhibit Pt dissolution and improving the performance of PEMFC. Conversely, when the ionomer is mainly distributed on the GDL side (positive ionomer gradient), it slows the loss of Pt2+ into MEM, which is achieved at the expense of performance to improve durability.