Designing gradient Pt particle size for degradation mitigation and performance maintenance of proton exchange membrane fuel cells

Gradient platinum (Pt) particle size design is a promising strategy to alleviate Pt degradation in the catalyst layer (CL) of proton exchange membrane fuel cells (PEMFCs), while it could reduce initial cell performance. Thereby, better performance maintenance for more durable PEMFCs during long-term operation is of great importance. In this study, gradient CLs with dual-layer and multi-layer Pt particle sizes are comprehensively evaluated by coupling a one-dimensional (1D) CL model and a 3D PEMFC model that simulates Pt degradation and cell performance, respectively. The simulation results show great benefits of gradient CLs in balancing Pt degradation mitigation and cell performance maintenance. Notably, we verified the “Pt retention step change” observed experimentally at Pt particle size transition interface in dual-layer CLs. Furthermore, our work revealed that the varying influence of different degradation mechanisms determines that excessive particle size disparity in gradient CLs would lead to reduced benefits for PEMFC durability owing to more Pt loss. Moreover, multi-layer designs diminish step changes in Pt retention across CLs after degradation, and the gradient CL with the exponential particle size growth pattern exhibits the best performance and outperforms the optimal dual-layer CL during the entire life cycle, mainly due to higher initial active reaction area and pronounced improvement of Pt distribution uniformity at the end of life. This study offers new insights into designing the gradient Pt particle size distribution in CLs, promoting PEMFC's durability and performance maintenance during long-term operation.