The formation of liquid water inside polymer electrolyte membrane fuel cells is an ongoing technical challenge. Water is produced by the electrochemical reaction in proportion to the current density, so efforts to increase fuel cell power output must provide for effective removal of product water. Failure to do so results in excessive accumulation of liquid water in the porous electrode which severely hinders gas phase transport of reactants, leading to concentration polarization and mass transfer limited currents. Understanding the behavior and impact of liquid water inside the fuel cell electrode has been hampered by a lack of experimental and modeling techniques appropriate for these unique porous materials. The electrodes are very thin (< 400 microns), highly porous (> 80%), anisotropic, compressible and chemically heterogeneous leading to complex wettability characteristics. This talk will present and discuss numerous experimental methods that have been developed specifically to study these materials, with particular emphasis on air-water capillary pressure measurements. The use of water and air to measure the capillary pressure curves, rather than the more typically used mercury intrusion porosimetry technique, has provided critical information pertaining to the wettability behavior of these materials. Ongoing work at LBNL will be also be briefly discussed. For more information about this seminar, please contact: JoAnne Lambert 510.486.4835, or send e-mail to JMLambert[at]lbl.gov