Analysis of performance degradation on the components in polymer electrolyte membrane fuel cell by dissecting the oxygen diffusion region

Performance degradation due to mechanical effect is an important durability issue for polymer electrolyte membrane fuel cells (PEMFCs). Mechanical degradation mainly occurs during the startup/shutdown mode at subzero temperature. However, studies about the contribution of mechanical degradation to the main PEMFC components of the gas diffusion layer (GDL) and catalyst-coated membrane (CCM) have not been analyzed quantitatively under various operating conditions. In this study, the freeze-thaw accelerated stress test (AST) is newly developed and performed to identify the exclusive effect of mechanical degradation on the GDL and CCM under normal and subzero conditions. Under normal conditions, the PEMFC performance result indicates that CCM has a larger degradation than the GDL owing to an increase in oxygen transport resistance and low water saturation point. Under subzero conditions, a cold start is experimentally investigated using the constant voltage method, revealing that the oxygen transfer coefficient dominantly affects the heat generation term in the 0-D model. Therefore, this study provides design guidelines for high-durability PEMFC components (GDL and CCM) and new insights into the interactive effects between heat and oxygen transport under normal and subzero conditions.