Modeling the effects of capillary property of porous media on the performance of the cathode of a PEMFC

A two-phase model was developed to study the impact of the capillary property of the gas diffusion (GDL) and catalyst layers (CL) and the saturation-level jump condition at the interface between these two dissimilar materials on the liquid water transport rate and the liquid water saturation levels in these porous layers and the performance of the cathode of a proton exchange membrane fuel cell (PEMFC). The study involves adjusting various aspects of the capillary curves of these porous layers and studying how these changes affect the cathode electrochemical performance to identify the most sensitive aspects. The simulated results show that fuel cell performance and the liquid water saturation levels in the CL and GDL depend on both the individual two-phase properties of these components and their interactions at the GDL/CL interface. The boundary condition at the GDL/channel interface for saturated air operation constrains the transport phenomenon in the GDL and CL to the hydrophobic regions of the capillary pressure curves. It was also found that capillary properties of the GDL had a more significant effect on the fuel cell performance than those of the CL, and better fuel cell performance was obtained with GDL and CL with high capillary diffusion capability and low hydrophilic porosity. (c) 2008 The Electrochemical Society.