Gas diffusion medium with microporous bilayer
A gas diffusion medium with microporoous bilayer is disclosed. The gas diffusion medium includes a diffusion medium substrate, with a dual layer, including a first sublayer that is comprised of a variation in particle sizes and second layer composed of one material with a uniform particle size. The gas diffusion medium with microporous bilayer has enhanced cushioning and water management properties.
1 . A gas diffusion medium comprising:
a diffusion medium substrate;
a sublayer; and
a microporous layer coating provided on said sublayer.
2 . The gas diffusion medium of claim 1 wherein said sublayer comprises conductive particles and an at least partially fluorinated polymer.
3 . The gas diffusion medium of claim 2 wherein said conductive particles comprises particles having an average particle size ranging from about 0.1 to about 40 micrometer.
4 . The gas diffusion medium of claim 2 wherein said sublayer has a thickness of from about 10 to about 100 micrometer.
5 . The gas diffusion medium of claim 1 wherein said microporous layer coating comprises carbon black particles and an at least partially fluorinated polymer.
6 . The gas diffusion medium of claim 5 further comprising pH-adjusting chemicals in said microporous layer coating.
7 . The gas diffusion medium of claim 5 wherein said sublayer comprises black carbon, graphite powder having a particle size of between about 1 μm and about 20 μm and polytetrafluoroethylene.
8 . The gas diffusion medium of claim 7 wherein said graphite particles have a mean particle size between 1 um and 10 μm.
9 . A gas diffusion medium comprising:
a diffusion medium substrate;
a sublayer comprising graphite on said substrate; and
a microporous layer coating substantially devoid of graphite provided on said sublayer.
10 . The gas diffusion medium of claim 9 wherein said sublayer further comprises black carbon and polytetrafluoroethylene.
11 . The gas diffusion medium of claim 10 wherein said graphite comprises graphite particles having a particle size of between about 1 μm and about 20 μm.
12 . The gas diffusion medium of claim 11 wherein said graphite particles have a mean particle size between 1 and 10 μm.
13 . The gas diffusion medium of claim 9 wherein said microporous layer coating comprises black carbon, polytetrafluoroethylene and a pH adjusting compound.
14 . The gas diffusion medium of claim 13 wherein said pH-adjusting compound comprises ammonium carbonate.
15 . The gas diffusion medium of claim 13 wherein said graphite comprises graphite particles having a particle size of between about 1 μm and about 20 μm.
16 . The gas diffusion medium of claim 15 wherein said graphite particles have a mean particle size between 1 um and 10 μm.
17 . A method of fabricating a gas diffusion medium, comprising:
providing a diffusion medium substrate;
providing a sublayer comprising graphite said substrate; and
providing a microporous layer coating on said sublayer.
18 . The method of claim 17 wherein said graphite has a particle size of between about 1 μm and about 20 μm.
19 . The method of claim 18 wherein said graphite has a mean particle size between 1 um and 10 μm.
20 . The method of claim 19 wherein said microporous layer coating comprises black carbon, polytetrafluoroethylene and a pH-adjusting compound.