Correlation between anisotropic bending stiffness of GDL and land/channel width ratio of polymer electrolyte membrane fuel cells

A correlation between anisotropic bending stiffness of a gas diffusion layer (GDL) and land/channel width ratios of metallic bipolar plates (MBPs) in polymer electrolyte membrane fuel cells has been systematically investigated. I–V performances of the fuel cells with 90° GDLs, whose directions of higher stiffness are perpendicular to the direction of the major flow field, are generally higher than those with 0° GDLs, whose directions of higher stiffness are parallel with the direction of the major flow field. However, the differences of I–V performances and high-frequency resistance values between 0° and 90° GDL cells gradually decrease with increasing land/channel width ratio, because of the reduced anisotropic stiffness effects of the GDLs due to the better support by the MBPs with wider lands. The cross-sectional images of GDLs upon compression indicate that the 0° GDL appears to be more deformed and intruded into channel than the 90° GDL under the narrowest lands, whereas both 0° and 90° GDLs show very little intrusion and deformation under the widest lands. The results clearly explain why some MBPs (i.e., narrower lands) exhibit strong effects of GDL’s anisotropic stiffness on cell performances, whereas other MBPs (i.e., wider lands) do not experience such effects.