Effects of catalyst layer structure and wettability on liquid water transport in polymer electrolyte membrane fuel cell

Optimal water levels in polymer electrolyte membrane (PEM) fuel cells are the key to prevent liquid water flooding and to reduce membrane dry out. A good understanding of liquid water transport is therefore essential to maintain an optimum water balance. In this study, a two-dimensional, two-phase, volume-averaged numerical model is developed and used to simulate the effect of catalyst layer structure and its surface wettability on liquid water transport in the cathode catalyst layer (CCL) of PEM fuel cells. The model is capable of handling liquid water transport across both the catalyst and gas diffusion layers. The simulation results are compared with literature, and a good agreement is found. The highest liquid water saturation in the CCL is observed under the rib, and the lowest value is observed under the flow channel. It is also observed that the wetting and geometric characteristics of CCL have significant influence on the liquid water transport, and the mobile liquid water saturation in a hydrophilic catalyst layer decreases with CCL surface wettability, that is, lower CCL contact angle yields lower liquid water saturation. Copyright (C) 2011 John Wiley & Sons, Ltd.