REDUCED THERMAL CONDUCTIVITY IN PEM FUEL CELL GAS DIFFUSION LAYERS
A fuel cell for a fuel cell power plant having gas diffusion layers which do not have microporous layers, includes a PEM ( 9 ), a cathode comprising at least a cathode catalyst ( 10 ) and a gas diffusion layer ( 17 ) on one side of the PEM, and an anode comprising at least an anode catalyst ( 11 ) and a gas diffusion layer ( 14 ) on the opposite side of the PEM, and a porous water transport plate having reactant gas flow field channels ( 31, 32 ) ( 21, 28 ) adjacent to each of said support substrates as well as water flow channels ( 22 ) in at least one of said water transport plates. The thermal conductivity of the cathode and/or the anode gas dif- fusion layers is less than about one-quarter of the thermal conductivity of conventional gas diffusion layers, less than about 0.25 W/m/K, to promote flow of water from the cathodes to the anodes and to the adjacent water transport plates, during start-up at normal ambient temperatures (lower than normal PEM fuel cell operating temperatures).
1 . A fuel cell for a fuel cell power plant which converts hydrogen and oxygen into electricity, heat and water, comprising:
a polymer electrolyte, proton exchange membrane (PEM);
a cathode catalyst layer on a first surface of said PEM;
an anode catalyst layer on a second surface of said PEM opposite to said first surface;
an anode gas diffusion layer adjacent to said anode catalyst and having a through-plane thermal conductivity, said anode gas diffusion layer devoid of a microporous layer;
a cathode gas diffusion layer adjacent to said cathode catalyst and having a through-plane thermal conductivity, said cathode gas diffusion layer devoid of a microporous layer;
a flow field plate having oxidant reactant gas flow field channels therein adjacent to said cathode;
a flow field plate having fuel reactant gas flow field channels therein adjacent to said anode gas diffusion layer;
characterized by:
either or both of said gas diffusion layers having a through-plane thermal conductivity which is less than about 0.25 W/m/K.
2 . A fuel cell according to claim 1 further characterized in that:
the thermal conductivity of either or both of said gas diffusion layers is between about 0.08 W/m/K and about 0.25 W/m/K.
3 . A fuel cell according to claim 1 further characterized in that:
the thermal conductivity of said cathode gas diffusion layer is between about 0.08 W/m/K and about 0.25 W/m/K and the thermal conductivity of said anode gas diffusion layer is between about 1.0 W/m/K and 1.5 W/m/K.
4 . A fuel cell power plant comprised of fuel cells according to claim 1 .
5 . A fuel cell power plant comprised of fuel cells according to claim 2 .
6 . A fuel cell power plant comprised of fuel cells according to claim 3 .