Claims
- 1. A porous diffusion media comprising a porous matrix carrying a distribution of water transfer particles, wherein:
said distribution of water transfer particles defines a plurality of high particle density regions characterized by a relatively high density of said water transfer particles and a plurality of low particle density regions characterized by a relatively low density of said water transfer particles; said relatively high and relatively low particle density regions alternate across a major planar dimension of said porous diffusion media parallel to first and second major faces of said diffusion media; and said water transfer particles are characterized by dimensions sufficiently small enough to permit migration of said water transfer particles through a thickness dimension of said porous matrix defined between said first and second major faces of said diffusion media.
- 2. A porous diffusion media as claimed in claim 1 wherein said water transfer particles are selected from carbon, graphite, non-perfluorinated polymers, metal oxides, and combinations thereof.
- 3. A porous diffusion media as claimed in claim 2 wherein said non-perfluorinated polymers comprise polyvinylidine fluoride (PVDF) and said metal oxides comprise silicon dioxide.
- 4. A porous diffusion media as claimed in claim 1 wherein said water transfer particles comprise a carbon/polymer composite.
- 5. A porous diffusion media as claimed in claim 1 wherein said water transfer particles are selected from carbon fibers or powders, graphite fibers or powders, and combinations thereof.
- 6. A porous diffusion media as claimed in claim 1 wherein said water transfer particles comprise a material forming said porous matrix.
- 7. A porous diffusion media as claimed in claim 6 wherein said porous matrix comprises carbon paper and said water transfer particles comprise carbon fibers or powders.
- 8. A porous diffusion media as claimed in claim 6 wherein said porous matrix comprises carbon paper and a layer of hydrophobic material and said water transfer particles comprise carbon fibers or powders.
- 9. A porous diffusion media as claimed in claim 1 wherein said water transfer particles comprise unbound dust.
- 10. A porous diffusion media as claimed in claim 1 wherein said water transfer particles are distributed across a cross section of said porous diffusion media between said first and second major faces of said diffusion media.
- 11. A porous diffusion media as claimed in claim 1 wherein said relatively high and relatively low particle density regions alternate across at least one of said first and second major faces of said diffusion media.
- 12. A porous diffusion media as claimed in claim 11 wherein said alternating density regions are characterized by a periodicity of less than about 1 cm.
- 13. A porous diffusion media as claimed in claim 1 wherein said relatively high and relatively low particle density regions alternate across said first and second major faces of said diffusion media.
- 14. A porous diffusion media as claimed in claim 1 wherein respective cross-sectional dimensions of said relatively high and relatively low particle density regions vary inversely across a cross section of said porous diffusion media between said first and second major faces of said diffusion media.
- 15. A porous diffusion media as claimed in claim 14 wherein said respective cross-sectional dimensions of said relatively high and relatively low particle density regions vary such that one of said major faces is dominated by said relatively high particle density regions while the other of said major faces is dominated by said relatively low particle density regions.
- 16. A porous diffusion media as claimed in claim 1 wherein respective properties of said relatively high and relatively low particle density regions vary across a cross section of said porous diffusion media between said first and second major faces of said diffusion media such that said first major face is collectively more hydrophilic than said second major face and said second major face is collectively more hydrophobic than said first major face.
- 17. A porous diffusion media as claimed in claim 1 wherein a characteristic density value of said relatively high particle density regions remains substantially uniform from one high particle density region to the next across one of said first and second major faces of said diffusion media.
- 18. A porous diffusion media as claimed in claim 1 wherein a characteristic density value of said relatively high particle density regions varies from one high particle density region to the next across one of said first and second major faces of said diffusion media.
- 19. A porous diffusion media as claimed in claim 18 wherein said variation in said characteristic density value defines a characteristic density value profile that increases from a flow field inlet region of said diffusion media to a flow field outlet region of said flow field.
- 20. A porous diffusion media as claimed in claim 1 wherein said high particle density regions are sufficiently hydrophilic to define an advancing contact angle of between about 135° and about 180° along one of said first and second major surfaces of said diffusion media.
- 21. A porous diffusion media as claimed in claim 1 wherein said high particle density regions are sufficiently hydrophilic to define an advancing contact angle of between about 160° and about 168° along one of said first and second major surfaces of said diffusion media.
- 22. A porous diffusion media as claimed in claim 1 wherein said high particle density regions are sufficiently hydrophilic to define a receding contact angle of between about 95° and about 135° along one of said first and second major surfaces of said diffusion media.
- 23. A porous diffusion media as claimed in claim 1 wherein said high particle density regions are sufficiently hydrophilic to define a receding contact angle of between about 95° and about 105° along one of said first and second major surfaces of said diffusion media.
- 24. A porous diffusion media as claimed in claim 1 wherein said porous matrix defines a substantially uniform porosity profile across said major planar dimension.
- 25. A porous diffusion media as claimed in claim 1 wherein said porous matrix comprises an electrically conductive material selected from carbon paper, graphite paper, cloth, felt, foam, carbon or graphite wovens, carbon or graphite non-wovens, metallic screens or foams, and combinations thereof.
- 26. A porous diffusion media as claimed in claim 1 wherein said porous matrix defines a thickness of between about 20 μm and about 1000 μm.
- 27. A porous diffusion media as claimed in claim 1 wherein said porous matrix defines a thickness of about 200 μm.
- 28. A porous diffusion media as claimed in claim 1 wherein said porous matrix defines a porosity characterized by a permeometer number of about 50 ft3/min./ft2 at about 0.5 inches of water.
- 29. A porous diffusion media as claimed in claim 1 wherein said porous matrix defines a porosity characterized by a Gurley permeometer number of between about 20 ft3/min./ft2 and about 100 ft3/min./ft2 at about 0.5 inches of water.
- 30. A porous diffusion media as claimed in claim 1 wherein said porous diffusion media further comprises a binder configured to at least partially secure said water transfer particles to said porous matrix.
- 31. A porous diffusion media as claimed in claim 30 wherein said binder comprises a fluoropolymer.
- 32. A porous diffusion media as claimed in claim 1 wherein said porous diffusion media further comprises hydrophobic material.
- 33. A porous diffusion media as claimed in claim 32 wherein said hydrophobic material is disposed along one of said first and second major faces of said diffusion media.
- 34. A porous diffusion media as claimed in claim 33 wherein said hydrophobic material comprises a layer.
- 35. A porous diffusion media as claimed in claim 34 wherein said hydrophobic layer has a thickness of up to about 125 μm.
- 36. A porous diffusion media as claimed in claim 33 wherein said hydrophobic material disposed along one of said first and second major faces is characterized by a loading of up to about 5 mg per cm2 of diffusion media surface area.
- 37. A porous diffusion media as claimed in claim 32 wherein said hydrophobic material is configured such that it is more repellent to water droplets than said relatively high and relatively low particle density regions of said porous diffusion media.
- 38. A porous diffusion media as claimed in claim 32 wherein said hydrophobic material comprises one of carbon, graphite, a fluoropolymer, a polymer, and combinations thereof.
- 39. A porous diffusion media as claimed in claim 38 wherein said hydrophobic material comprises a fluoropolymer produced from one of polytetrafluoroethylene (PTFE), tetrafluoroethylene (TFE), ethylenetetrafluoroethylene (ETFE), fluorinated ethylenepropylene (FEP), a perfluoroalkoxy compound, and combinations thereof.
- 40. A porous diffusion media as claimed in claim 38 wherein said hydrophobic material comprises a polymer selected from polyphenylene, polyvinylidine fluoride (PVDF), and combinations thereof.
- 41. A porous diffusion media as claimed in claim 32 wherein said hydrophobic material is disposed along only one of said first and second major faces of said diffusion media.
- 42. A device comprising a porous diffusion media positioned against a catalyst layer, wherein:
said porous diffusion media comprises a porous matrix carrying a distribution of water transfer particles; said distribution of water transfer particles defines a plurality of high particle density regions characterized by a relatively high density of said water transfer particles and a plurality of low particle density regions characterized by a relatively low density of said water transfer particles; said relatively high and relatively low particle density regions alternate across a major planar dimension of said porous diffusion media parallel to first and second major faces of said diffusion media; and said water transfer particles are characterized by dimensions sufficiently small enough to permit migration of said water transfer particles through a thickness dimension of said porous matrix defined between said first and second major faces of said diffusion media.
- 43. A device as claimed in claim 42 wherein respective cross-sectional dimensions of said relatively high and relatively low particle density regions vary inversely across a cross section of said porous diffusion media between said first and second major faces of said diffusion media such that said first major face is characterized by high particle density regions of relatively large cross sectional dimensions and said second major face is characterized by high particle density regions of relatively small cross sectional dimensions.
- 44. A device as claimed in claim 43 wherein said diffusion media is positioned against said catalyst layer along said first major face of said diffusion media.
- 45. A device as claimed in claim 42 wherein respective cross-sectional dimensions of said relatively high and relatively low particle density regions vary across a cross section of said porous diffusion media between said first and second major faces of said diffusion media such that one of said major faces is dominated by said relatively high particle density regions while the other of said major faces is dominated by said relatively low particle density regions.
- 46. A device as claimed in claim 42 wherein respective properties of said relatively high and relatively low particle density regions vary across a cross section of said porous diffusion media between said first and second major faces of said diffusion media such that said first major face is collectively more hydrophilic than said second major face and said second major face is collectively more hydrophobic than said first major face.
- 47. A device as claimed in claim 46 wherein said diffusion media is positioned against said catalyst layer along said first major face of said diffusion media.
- 48. A device as claimed in claim 47 wherein said porous diffusion media comprises hydrophobic material disposed along said second major face of said diffusion media.
- 49. A device as claimed in claim 42 wherein said device further comprises additional structure defining, in combination with said catalyst layer and said porous diffusion media, a membrane electrode assembly interposed between an anode flow field and a cathode flow field.
- 50. A device as claimed in claim 49 wherein said device further comprises additional structure defining, in combination with said membrane electrode assembly, said anode flow field, and said cathode flow field, a fuel cell.
- 51. A device as claimed in claim 50 wherein said water transfer particles are characterized by migrational freedom sufficient to permit transfer of said water transfer particles to a surface of said catalyst layer during operation of said fuel cell.
- 52. A device as claimed in claim 50 wherein said device further comprises additional structure defining, in combination with said fuel cell, a vehicle.
- 53. A device as claimed in claim 51 wherein said fuel cell defines a motive power source of said vehicle.
- 54. A device comprising a membrane electrode assembly interposed between an anode flow field and a cathode flow field of a fuel cell, wherein:
a porous diffusion media is positioned against a catalyst layer of said membrane electrode assembly; said porous diffusion media comprises a porous matrix carrying a distribution of water transfer particles; said porous matrix comprises carbon paper and said water transfer particles comprise carbon fibers or powders; said distribution of water transfer particles defines a plurality of high particle density regions characterized by a relatively high density of said water transfer particles and a plurality of low particle density regions characterized by a relatively low density of said water transfer particles; said relatively high and relatively low particle density regions alternate across a major planar dimension of said porous diffusion media parallel to first and second major faces of said diffusion media; respective properties of said relatively high and relatively low particle density regions vary across a cross section of said porous diffusion media between said first and second major faces of said diffusion media such that said first major face is collectively more hydrophilic than said second major face and said second major face is collectively more hydrophobic than said first major face; said diffusion media is positioned against said catalyst layer along said first major face of said diffusion media; said diffusion media is positioned against a flow field of said fuel cell along said second major face of said diffusion media; said porous diffusion media comprises hydrophobic material disposed along said second major face of said diffusion media; and said hydrophobic material comprises polytetrafluoroethylene (PTFE).
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation-in-part of U.S. patent application Ser. No. 10/345,121 (GP-302361), filed Jan. 5, 2003. This application is also related to U.S. patent application Ser. No. 10/628,318 (GMC 0047 PA), Ser. No. 10/628,316 (GMC 0048 PA), and Ser. No. 10/628,856 (GMC 0051 PA) filed Jul. 28, 2003.
Continuation in Parts (1)
|
Number |
Date |
Country |
Parent |
10345121 |
Jan 2003 |
US |
Child |
10685346 |
Oct 2003 |
US |