Effects of clamp load on PEFC performance and over voltages (comparison of contact pressure between paper and cloth type GDLs)

The performance and over voltages of the polymer electrolyte fuel cells (PEFC) with paper and cloth type gas diffusion layers (GDL) were evaluated using a test apparatus in which the clamp load of a test cell could be changed. The contact pressure distribution of GDL was also evaluated using a pressure measuring film. Under moderate humidification condition, an increase in the clamp load is effective in reducing IR over voltage, and thereby improving the PEFC performance. The performance of the paper type GDL is higher than that of the cloth type GDL at all clamp loads. The GDL contact pressure has a peak at the center of the separator rib and has a bottom at the separator channel. The pressure distribution becomes more uniform when using the paper type GDL rather than the cloth type GDL. The GDL electrical resistance amounts to only about 20% of the overall IR resistance. The difference of the overall IR voltage between the paper and cloth type GDLs is more significant than that of the GDL electrical resistance. This is because the uniform pressure distribution obtained with the paper type GDL enhances the contact between MEA and GDL, thereby reducing the MEA resistance.