Specially prepared gas diffusion media improve the performance of PEM fuel
cells. The media are made by first dipping an electrically conductive
porous material such as carbon fiber paper into a suspension of
hydrophobic polymer and drying the paper to create a desired deposition
pattern of hydrophobic polymer on the substrate. Then a paste containing
a fluorocarbon polymer and carbon particles is applied to a desired side
of the substrate, and thereafter the paste and hydrophobic polymer are
sintered together at high temperature on the paper. In particular,
nonionic surfactants remain on the carbon fiber paper after the initial
hydrophobic polymer is applied to the electrically conductive porous
material. When the paste is coated on the dried paper, the paste is in
contact with a hydrophilic surface.