Analysis of the degradation mechanism of high-power PEM fuel cells: end-plate effect due to hydrogen recirculation structure

Proton Exchange Membrane Fuel Cells (PEMFC), with the advantages of long endurance and fast charging, are considered to be the future development direction of power sources for commercial vehicles. In this paper, a 2000-h accelerated decay test was conducted on an 80 kW fuel cell with a hydrogen recirculation structure, and analyzed the impact of the hydrogen recirculation structure on the end-plate effect of the stack. The experimental results indicate that the power decay of the stack reaches 7.8 %, with the increase in concentration impedance being the primary cause of stack degradation, and the degradation rate of concentration impedance under rated conditions (1.8 A cm−2) is 2.14 times that of activation impedance. The single cells with the most severe degradation are located at the end-plate sides of the stack. The voltage degradation rate of the single cell at the gas-distribution end reaches 5.35 times that of the stack, which significantly shortens the overall service life of the stack. The first single cell at the gas-distribution end exhibits the most severe concentration impedance degradation, primarily due to carbon corrosion caused by liquid water accumulation, leading to hydrophobicity degradation of the GDL, where liquid water is introduced due to the hydrogen recirculation structure. A mitigation strategy involving the installation of a water separation manifold was proposed, and the results show that this approach reduces the anode pressure drop by 22.3 % and decreases the voltage fluctuation of the single cell at the gas-distribution-end by 65 %. This research provides a theoretical foundation for the performance optimization of high-power PEMFC stacks.