Performance Degradation in Proton Exchange Membrane Fuel Cell Under Large Load Variation at Rapid Startup: Phenomena and Solution Based on Different Flow Fields.

The durability of proton exchange membrane fuel cells (PEMFCs) under large load variation at rapid startup is critical for commercialization. Experimental and numerical results indicate that the five-channel serpentine flow field (FSFF) design exhibited the optimal large load variation capability at rapid startup and more effective performance degradation mitigation. Therefore, experimental investigations are conducted on the performance degradation and membrane electrode assembly deterioration of PEMFCs with parallel flow field (PFF) and FSFF designs under rapid dynamic loads (20,000 cycles, 2 s load transients to 3000 mA cm^-2). The results demonstrate that the multi-channel FSFF with better gas distribution uniformity and water removal capability significantly mitigates voltage degradation (9.11% vs 20.77% for PFF), reducing both cathode charge transfer resistance and electrochemical surface area degradation. Spatial degradation analysis reveals severe catalyst layer (CL) thinning in outlet regions for both configurations, but FSFF exhibits better degradation mitigation: cathode CL thickness reduction in the outlet region is lower than PFF, accompanied by reduced Pt particle size evolution and agglomeration. These findings highlight the critical role of flow field design in optimizing dynamic durability under large load variation at rapid startup.