To maintain proton exchange membrane fuel cells (PEFC) at high efficiencies without flooding, it is necessary to control the liquid water transport in the gas diffusion layer (GDL). This experimental study investigates the effects of the GDL fiber direction on the cell performance using an anisotropic GDL. The results of the experiments showed that the efficiency of the cell was much better when the fiber direction was perpendicular to the channel direction, and that the cell with perpendicular fibers was more tolerant to flooding than the cell with fibers parallel to the channel. To determine the mechanism that gives rise to the fiber direction effects, the liquid water behavior in the channel was observed through a glass window on the cathode side. Additionally, a small cell with a 2 cm2 active area was made, to investigate the water distribution inside the GDL by freezing the water and observing the ice distribution. These ice pictures showed that reactions are more active under channels than under ribs. This is because the accumulated water prevents reaction under the ribs, and indicates the importance of water removal from the rib zones.

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