Comparative analysis of degradation mechanisms in HT-PEM fuel cells under start-stop and load cycling with hydrogen and nitrogen-diluted feeds

The integration of reformers into high -temperature polymer electrolyte membrane (HT-PEM) fuel cells presents a significant opportunity to improve fuel flexibility and cost-effectiveness. To understand their degradation, we applied two start-stop cycling procedures: one with pure H 2 and another with an 80 vol % H 2 and 20 vol % N 2 mix to simulate reformate gas. We also performed a load cycling test with H 2 as anode gas. The results indicated that degradation rate of pure H 2 start-stop cycling showed 306 mu V h -1 , while load cycling demonstrated a degradation rate of 19.7 mu V h -1 for the current density of 0.2 A cm -2 , and 88.2 mu V h -1 for the current density of 0.4 A cm -2 . Start-stop cycling with diluted gas resulted in a constant voltage drop with a degradation rate of 3.129 mV h -1 . Electrochemical impedance spectroscopy (EIS) indicated an increased ohmic resistance during start-stop cycling and higher charge transfer (high -frequency) and mass transport (low -frequency) resistance with nitrogen introduction. Scanning electron microscope results confirmed MEA degradation. In conclusion, start-stop cycling and anode gas dilution are stressors that accelerate HT-PEM fuel cell degradation, reducing its lifetime.