A multi-mechanism degradation model for PEMFC to unravel the aging processes on cell lifetime

Degradation of catalysts and proton exchange membrane in the membrane electrode assemblies (MEAs) are two key factors leading to the performance loss of proton exchange membrane fuel cells (PEMFCs). However, the interactions between degradation processes and the reactive transport processes in the cells remain unclear, limiting further improvements in cell durability. Herein, a fuel cell model coupling the two degradation mechanisms is developed to reveal the impact of simultaneous degradation of the catalyst and membrane on cell performance. The results show that the two degradation processes interact with each other through the local electrochemical reaction environment, resulting in higher decay rates than if only one degradation mechanism is simulated. Cell performance loss is dominated by Pt degradation at high potential, accounting for over 95%, while membrane degradation contributes more at low potential. Moreover, the contribution of membrane degradation to performance loss gradually increases with prolonged operation. Increasing the operating current density would mitigate both Pt and the membrane degradation. Compared to operation at 100 mA·cm⁻², the cell at 400 mA·cm⁻² showed an 8.64% higher remaining ECSA and a 1.97 S·m⁻¹ greater proton conductivity. Finally, the model is used to study the effects of membrane thickness and Pt particle size on cell degradation during operation, and it is found that thicker membranes help mitigate cell degradation, but excessive thickness increases ohmic losses. Increasing the particle size helps mitigate catalyst degradation but slightly accelerates membrane degradation due to the reduction in electrochemical active surface area. Simulation results indicate that adjusting particle size in accordance with operating time requirements can optimize the end-of-life performance of fuel cells. This study reveals the interaction between multiple degradation mechanisms and reactive transport within the cell, providing a theoretical basis for fuel cell durability optimization.