Analysis of Water Transport in Anisotropic Gas Diffusion Layers for Improved Flooding Performance of PEFC

Abstract

To improve the flooding performance of a polymer electrolyte fuel cell (PEFC), the effect of fiber direction of gas diffusion layer (GDL) is investigated by a lattice Boltzmann method (LBM). Because much water is generally accumulated in the GDL under the ribs, transport of the water into the channel is the focus in this report. The results show that the anisotropic GDL with the fibers approximately distributed in the direction perpendicular to the rib reduces the water accumulated in the GDL compared with an isotropic GDL, but the anisotropic GDL with the strongly aligned fibers increases the water accumulation. This is because the water transport in the direction perpendicular to the rib is improved due to the flow along the anisotropic fibers, but the water transport characteristic in the thickness direction deteriorates due to the sharp and narrow pores in case of the strongly aligned fibers. The experiment developed in our previous study demonstrates that the anisotropic GDL with somewhat oriented fibers reduces the water in the GDL. Next, an attempt to improve the water transport is carried out. By the surface treatment reducing the contact angle of the GDL surface, the water accumulated in the anisotropic GDL is reduced.