The effect of through plane pore gradient GDL on the water distribution of PEMFC

The effect of through plane pore gradient of gas diffusion layer (GDL) on the performance of Polymer Electrolyte Membrane Fuel Cell is investigated experimentally. The performance with GDLs having no, medium and high pore gradient are compared at 2 different relative humidity (RH) conditions. The medium pore gradient GDL shows generally the best performance in both RH conditions. The performance difference is analyzed based on the water distribution. The water distribution is measured through the X-ray visualization. The amount of water is reduced with the pore gradient GDL. This change reduces the concentration over-potential, and thereby increases the performance at high RH condition. However, the reduction of liquid water results in dehydration of the membrane at low RH condition. This makes lower performance with high pore gradient. The highest performance is not matched with the highest pore gradient. The effect of pore gradient is distinct when water exists sufficiently.