An experimental study of the liquid water saturation level in the cathode gas diffusion layer of a PEM fuel cell

► Liquid saturation level in cathode GDL was determined by a switchable flow field. ► Pressure drop across GDL in interdigitated mode correlates with saturation level. ► Serpentine mode has higher liquid saturation level in GDL and lower performance. ► Interdigitated mode has lower saturation level and higher performance. ► Fuel cell became unstable when average liquid saturation level in GDL exceeds 0.2.