Characterization of the Catalyst Layer in a PEMFC During Subzero Operation

Abstract

In-situ isothermal constant voltage (ICV) experiments and stack freeze start-ups at -25{degree sign}C, in combination with ex-situ image analysis (Cryo-FESEM) has been used to investigate the behaviour of product water at subzero temperatures. Use of these tools enables more small scale, rapid material screening to design membrane electrode assemblies (MEAs) with improved subzero operation capability. Cryo-FESEM images at different stages of sustained subzero operation suggests that any ice present prior to operation melts and migrates away from the membrane towards the GDL where it is frozen along with newly produced product water. More and more water is frozen until reactants can no longer reach the catalyst sites.