Kinetic studies of cathode degradation on PEM fuel cell short stack level undergoing freeze startups with different states of residual water and current draws

One of the biggest challenges for a wide spread introduction of polymer electrolyte membrane fuel cells in automotive applications is the freeze start at subzero temperatures as this poses a severe threat to fuel cell performance and overall lifetime. Therefore, the impact of current draw during stack freeze startup at various rest water contents and current densities was investigated applying state of the art in-situ testing as quasi cyclic voltammetry.The results indicate a clear dependency between number of freeze startups and performance loss, whereas higher initial water content within the stack reduced its destructive impacts.In our earlier work we were able to show the dependency between residual water and degradation for non-freeze-startup-capable systems at the unit cell level 31]. With this work we confirm that the same physical relationship also applies to freeze-startup-capable systems on the short stack level.Furthermore, reversible performance losses that were encountered during this study can be assigned to oxidizable fuel contaminants, which are believed to be CO, and an easy cleansing procedure is being suggested.