Influences of gas diffusion layer permeability on the performance of polymer electrolyte fuel cells

In-plane air permeance of gas diffusion layers (GDLs) was measured under compression conditions typical of polymer electrolyte fuel cells (PEFCs). When the compression pressure increases, maximum and mean flow pore diameters of GDLs decrease, causing the permeability to be deteriorated. In the case of the GDL coated with a micro porous layer (MPL), through-plane permeance measured using the conventional Gurley method decreases significantly, however, in-plane permeance decreases slightly when compared to the GDL without MPL. The MPL thickness penetrated in the carbon paper substrate can be estimated by the comparison of in-plane permeances with and without MPL. The permeance increases in proportion to the value of porosity multiplied by squired mean flow pore diameter. This relationship provides effective means to evaluate the porosity of GDLs with MPL. Increasing thickness and porosity of the GDL substrate enhances in-plane permeability of GDLs with MPL. This is effective in reducing flooding, thereby improving the PEFC performance under high-humidity conditions.