Effect of Flow Field Pattern and Microporous Layer on Gas Purge of a Polymer Electrolyte Fuel Cell

The effect of flow field pattern and microporous layer (MPL) on the exhaust of the residual water at the flow channel, gas diffusion layer (GDL), and catalyst layer (CL) in the cathode of a polymer electrolyte fuel cell during gas purge after shutdown is separately studied for preventing freeze damage and efficient cold start below freezing point. The time variations of the high frequency and charge transfer resistances are obtained from electrochemical impedance spectroscopy to detect the drying of each component separately. This can be used to stop the purging appropriately to minimize energy consumption. An interdigitated type flow field drys the GDL substrate faster than a serpentine flow field. In addition, MPL drying process and its moisture retention effect on the drying of the CL and electrolyte membrane are observed. The serpentine flow field is shown to dry the MPL faster than the interdigitated type flow field.