Abstract <p>The performance and durability of proton exchange membrane fuel cells (PEMFCs) are closely related to their operating temperature. Although existing studies have revealed the macroscopic relationship between temperature and performance, the degradation mechanisms of the membrane electrode assembly (MEA) are complex and involve mesoscale structures. These mechanisms are difficult to analyze in detail using conventional experimental methods. In this study, a multiscale numerical model was developed to couple the common degradation mechanisms of PEMFC MEAs, including carbon corrosion, platinum (Pt) oxidation, dissolution, redeposition, and changes in structural characteristics. The model was used to investigate the effects of different operating temperatures on MEA degradation. The results show that operating temperature significantly affects the relative humidity distribution, carbon corrosion rate, Pt dissolution rate, and degradation of the proton exchange membrane (PEM) in PEMFCs. Specifically, at low temperatures (45°C), higher relative humidity leads to more severe carbon corrosion, while at high temperatures (85°C), the dissolution rate of Pt and the degradation rate of PEM increase. For every 1°C increase in temperature, the average Pt dissolution rate increases by 5.8 × 10⁻⁸ g/m². Moreover, the membrane degradation exhibits a higher degradation rate as the temperature decreases at temperatures below 90°C, with the degradation rate at 45°C being faster than at 85°C.This study provides a theoretical basis for optimizing the operating temperature of PEMFCs to enhance their performance and durability and offers new insights into the relationship between temperature and degradation mechanisms.</p>