Spatially heterogeneous degradation behaviors and mechanisms of catalyst layers in large-scale PEMFC stacks under dynamic operating conditions

Regional non-uniform decay of membrane electrode assemblies (MEAs) in Proton Exchange Membrane Fuel Cells (PEMFCs) is a critical factor causing fuel cell performance degradation. This study conducts a 5000-h accelerated stress test under dynamic driving conditions on a 30 kW PEMFC stack, analyzing the regional decay behavior of the catalyst layer (CL). The results show that MEAs exhibit non-uniform decay along the gas flow channel, with the performance decay rate of MEAs at the air inlet (38.6% voltage loss at 1 A cm −2 ) significantly higher than that at the hydrogen inlet (18.1%). Tests indicate that the electrochemical active surface area of the cathode CL at the air inlet decreases by up to 56%, with carbon support corrosion far exceeding that of Pt catalysts. Accompanied by mesoporous structure collapse, mass transfer processes are severely hindered, leading to a 118.7% increase in mass transfer resistance at the air inlet. Further analysis indicates that electrochemical oxidation processes within the cathode CL is a major contributor to ionomer side-chain degradation. This study reveals the influence of the synergistic mechanism between regional carbon corrosion and ionomer decay in CLs on fuel cell performance, providing a theoretical basis for enhancing PEMFC durability.