Water Transport Characteristics of Gas Diffusion Layer in a PEM Fuel Cell
Ashok S. Damle, Techverse, Inc., 124 Goldenthal Court, Cary, NC 27519 and Vernon Cole, CFD Research Corporation, 215 Wynn Drive, Huntsville, AL 35805.
Effective management of water produced in a Proton Exchange Membrane (PEM) fuel cell is essential to avoid deterioration of fuel cell performance due to flooding of the catalyst and gas diffusion layers (GDL) or by drying of the membrane over the full operating temperature and load range. Ineffective water management leads to liquid-phase water blockage and mass-transport-limited performance or decreased protonic conductivity in the membrane and catalyst/GDL due to dehumidification of the ionomer. The characteristics of the GDL and catalyst layers, membrane and gas flow fields in bipolar plates affect water management and operation with GDL media being the most critical component influencing water transport in PEM fuel cells. This paper will present experimentally determined water transport characteristics through GDL media. Capillary pressure-water saturation correlations of various grades of GDL media were determined by “direct water displacement” technique with applied hydrostatic head. Dry as well as wet media gas permeability of the GDL media was also determined. In general, inhomogeneous nature of media pore structure was found to lead to water breakthrough at isolated locations on GDL surface predominantly influencing water/gas transport.