Channel intrusion of gas diffusion media and the effect on fuel cell performance

The effect of gas diffusion medium (GDM) intrusion on the performance of proton exchange membrane (PEM) fuel cells is investigated. The mechanical behaviors of various GDM are characterized in compressive, flexural, and shear tests. The results are used in a numerical model to calculate the channel intrusion of GDM. The intrusion calculation from the numerical model agrees well with the measurements from an intrusion measurement setup and a pressure drop measurement device for various GDM. A simplified reactant flow redistribution model of parallel channels developed in this study suggests that a 5% variation in GDM intrusion can result in a 20% reduction of reactant flow in the most intruded channel. The GDM intrusion and intrusion variation are found to induce significant performance discrepancy among cells of a 30-cell automotive fuel cell stack consisting of two different production lots of commercial GDM. The study suggests that in the future mass production of fuel cell stacks, GDM manufacturers need to greatly tighten their product variations in mechanical property and thickness to ensure reliable PEM fuel cell operations. (C) 2008 Global Technology Inc. Published by Elsevier B.V. All rights reserved.