Durability is one of the critical issues to restrict the commercialization of proton exchange membrane fuel cells (PEMFCs) for the vehicle application.The practical dynamic operation significantly affects the PEMFCs durability by corroding its key components.In this work,the degradation behavior of a single PEMFC has been investigated under a simulated automotive load-cycling operation,with the aim of revealing the effect of load amplitude (0.8 and 0.2 A/cm2 amplitude for the current density range of 0.1-0.9 and 0.1-0.3 A/cm2,respectively) on its performance degradation.A more severe degradation on the fuel cell performance is observed under a higher load amplitude of 0.8 A/cm2 cycling operation,with～10.5％ decrease of cell voltage at a current density of 1.0 A/cm2.The larger loss of fuel cell performance under the higher load amplitude test is mainly due to the frequent fluctuation of a wider potential cycling.Physicochemical characterizations analyses indicate that the Pt nanoparticles in cathodic catalyst layer grow faster with a higher increase extent of particle size under this circumstance because of their repeated oxidation/reduction and subsequent dissolution/agglomeration process,resulting in the degradation of platinum catalyst and thus the cell performance.Additionally,the detected microstructure change of the cathodic catalyst layer also contributes to the performance failure that causes a distinct increase in mass transfer resistance.