Start/stop and local H₂ starvation mechanisms of carbon corrosion: Model vs. experiment

This paper discusses fundamental models developed to predict cathode carbon support corrosion induced by start-stop and local H₂ starvation in a PEM (proton exchange membrane) fuel cell. The model incorporating the electrode pseudo-capacitance agrees well with controlled start/stop experiments. When the pseudo-capacitive effect is included, the model not only captures the difference in CO₂ evolution between start and stop, but also matches the measured spatially resolved mass activity and limiting current distribution of the damaged cathode electrode. For long H₂/airfront residence times during start/stop, commonly used in accelerated materials tests, the electrode damage predicted by the capacitive model is similar to that predicted by previously published models that neglect pseudo-capacitive effects. However, for application relevant shorter residence times, significantly lower damages are predicted when capacitive effects are included, consistent with experiments. Because local H₂ starvation occurs on a longer time scale, pseudo-capacitive effects are less significant.