Direct measurement of the capillary pressure characteristics of water–air–gas diffusion layer systems for PEM fuel cells

A method and apparatus for measuring the relationship between air–water capillary pressure and water saturation in PEMFC gas diffusion layers is described. Capillary pressure data for water injection and withdrawal from typical GDL materials are obtained, which demonstrate permanent hysteresis between water intrusion and water withdrawal. Capillary pressure, defined as the difference between the water and gas pressures at equilibrium, is positive during water injection and negative during water withdrawal. The results contribute to the understanding of liquid water behavior in GDL materials which is necessary for the development of effective PEMFC water management strategies.