Patent ID: 7670704

Claim:
A polymer electrolyte membrane fuel cell comprising: a membrane electrode assembly comprising an ion exchange membrane disposed between a pair of catalytic electrode layers; first and second electrically conductive diffusion media formed as a layer wherein said first diffusion media is in fluid and electrical communication with a first of said catalytic electrode layers and said second diffusion media is in fluid and electrical communication with a second of said catalytic electrode layers; and an anode flow field in fluid communication with one of said first and second diffusion media layers and a cathode flow field in fluid communication with the other of said first and second diffusion media layers, wherein: said first or second diffusion media layers or both comprises a diffusion media substrate and a mesoporous layer; said first or second diffusion media substrate comprises a porous fibrous matrix defining first and second major faces comprising an electrically conductive carbonaceous material; said first or second diffusion media substrate carries said mesoporous layer along at least a portion of one of said first and second major faces of said substrate; said first or second mesoporous layer comprises hydrophobic and hydrophilic components defining hydrophobic and hydrophilic regions within said mesoporous layer; said first or second mesoporous layer comprises an electrically conductive carbonaceous material; said first or second mesoporous layer is characterized by a porosity greater than a porosity of said first or second diffusion media substrate; and said first or second diffusion media substrate is free of fluorinated polymers outside of said portion of one of said first and second major faces of said substrate carrying said mesoporous layer; wherein said first or second mesoporous layer is characterized by pore sizes between 1 nm and 1 μm.