Impact of Gas Diffusion Layers (GDLs) on Water Transport in PEFCs

Abstract

The gas diffusion layer (GDL) is a critical component for water management in PEFCs (Polymer Electrolyte Fuel Cells). The impact of anode GDLs and the hydrophobic/hydrophilic nature of GDLs were studied in order to determine the effect of water transport on membrane-electrode assembly (MEA) performance. Anode GDLs, regardless of their hydrophobic or hydrophilic nature, are of minimal bearing on the MEA performance, as long as they are thick enough to prevent flooding at the anode side. MEA performance largely depends on the combination of hydrophobic and hydrophilic anode and cathode GDLs. The best performance was obtained for the MEA using a hydrophilic GDL for both anode and cathode. In the case of an MEA with a non-hydrophobic anode GDL, use of a hydrophobic cathode GDL instead of a hydrophilic cathode GDL increased flooding of the anode, suggesting that water produced in the cathode catalyst layer was pushed across the membrane to the anode side by a pressure barrier created by the hydrophobic cathode MPL. The MEA using a hydrophilic MPL for both cathode and anode GDLs has proven to be advantageous by demonstrating stable performance for 200 hours, operating at 2.0 A/cm2, at 64ºC and 100%RH.