Fuel cells having silicon substrates and/or sol-gel derived support structures

• US 6,641,948 B1
• Filed: 11/17/2000
• Issued: 11/04/2003
• Est. Priority Date: 11/17/1999
• Status: Expired due to Fees

• Current Assignee: Neah Power Systems, Inc.
• Original Assignee: Neah Power Systems, Inc.
• Inventors: Rice, Gordon L., Ohlsen, Leroy J., Nelson, Craig E., Chan, Chung M., Mallari, Jonathan C., Cooke, Aaron M.
• Primary Examiner(s): Gulakowski, Randy
• Assistant Examiner(s): Crepeau, Jonathan
• Application Number:
  US09/715,830
• Time in Patent Office: 1,082 Days
• Field of Search: 429/30, 429/32, 429/40, 429/41, 429/42, 429/44, 429/46
• US Class Current: 429/480
• CPC Class Codes: H01M 4/8605 Porous electrodes
• CPC Class Codes: H01M 4/8647 consisting of more than one material, e.g. consisting of composites
• CPC Class Codes: H01M 4/921 Alloys or mixtures with metallic elements
• CPC Class Codes: H01M 8/023 Porous and characterised by the material
• CPC Class Codes: H01M 8/0245 in the form of layered or coated products
• CPC Class Codes: H01M 8/0258 characterised by the configuration of channels, e.g. by the flow field of the reactant or coolant
• CPC Class Codes: H01M 8/026 characterised by grooves, e.g. their pitch or depth
• CPC Class Codes: H01M 8/1004 characterised by membrane-electrode assemblies [MEA] H01M8/12 takes precedence
• CPC Class Codes: H01M 8/1011 Direct alcohol fuel cells [DAFC], e.g. direct methanol fuel cells [DMFC]
• CPC Class Codes: H01M 8/2483 characterised by internal manifolds
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

Fuels cells, electrode assemblies, and electrodes that comprise silicon and/or sol-gel derived support structures, as well as to methods relating thereto, are disclosed herein. In one embodiment, the invention is directed to an electrode assembly adapted for use with a fuel cell comprises: an anode derived from a first planar silicon substrate; an electrolyte; a cathode derived from a second planar silicon substrate; wherein the anode and the cathode are parallel to each other and separated by an interstitial region comprising the electrolyte. In another embodiment, the invention is directed to electrode adapted for use with a fuel cell, wherein the electrode comprises a silicon substrate that functions as a current conductor, wherein the silicon substrate has a plurality of pores that define pore surfaces, wherein at least a portion of the pore surfaces have a catalyst thereon, wherein the catalyst is derived from one or more metallic precursors chemisorbed onto at least the pore surfaces.

Claims

1. An electrode assembly adapted for use with a fuel cell, comprising:

an anode derived from a first planar silicon substrate;

an electrolyte;

a cathode derived from a second planar silicon substrate;

wherein the anode and the cathode are spaced apart and substantially parallel to each other so as to define a spaced apart region, and wherein the electrolyte is interposed between the anode and the cathode, and wherein the anode and the cathode each have a plurality of porous regions that define anode pore surfaces and cathode pore surfaces, and wherein the anode pore surfaces and the cathode pore surfaces each have a catalyst dispersed thereon such that the catalyst is noncontiguously dispersed throughout the plurality of porous regions of the anode and the cathode.

2. The electrode assembly of claim 1 wherein the first and second planar silicon substrates are silicon wafers.

3. The electrode assembly of claim 1, further comprising a blocking media that is substantially impermeable to at least methanol and is substantially permeable to hydrogen atoms, wherein the blocking media is interposed between the anode and the cathode.

4. The electrode assembly of claim 3 wherein the blocking media is integrally connected to the cathode.

5. The electrode assembly of claim 3 wherein the blocking media comprises a metallic membrane.

6. The electrode assembly of claim 3 wherein the blocking media comprises palladium, niobium, tantalum, vanadium, or a combination thereof.

7. The electrode assembly of claim 3 wherein the blocking media is a plurality of proton conducting plugs.

8. The electrode assembly of claim 1 wherein the anode has a plurality of etched or micromachined flow channels.

9. The electrode assembly of claim 1 wherein the catalyst dispersed on the anode pore surfaces comprises a plurality of metallic particles.

10. The electrode assembly of claim 9 wherein the metallic particles are derived from platinum and ruthenium precursors.

11. The electrode assembly of claim 1 wherein the cathode has a plurality of etched or micromachined flow channels.

12. The electrode assembly of claim 1 wherein the plurality of porous regions of the cathode are nanoporous, mesoporous, and/or macroporous.

13. The electrode assembly of claim 1 wherein the plurality of porous regions of the cathode are mesoporous, wherein each of the plurality of mesoporous regions comprise a random array of sponge-like interconnected pores having an open cell structure.

14. The electrode assembly of claim 1 wherein the catalyst dispersed on the cathode pore surfaces comprises a plurality of metallic particles.

15. The electrode assembly of claim 14 wherein the metallic particles are derived from a platinum precursor.

16. The electrode assembly of claim 1 wherein the electrolyte comprises a solid polymer electrolyte.

17. The electrode assembly of claim 16 wherein the solid polymer electrolyte comprises a perfluorosulfonic polymer membrane.

18. The electrode assembly of claim 1 wherein the electrolyte comprises first and second solid polymer electrolyte coatings and an acid, wherein the first solid polymer electrolyte coating is on the anode, and wherein the second solid polymer electrolyte coating is on the cathode, and wherein the acid is contained in an organic fuel that flows through the anode and the spaced apart region.

19. The electrode assembly of claim 18 wherein the organic fuel comprises water and an alcohol selected from the group consisting ethanol, propanol, methanol, or a combination thereof, and the acid is phosphoric acid, sulfuric acid, or a combination thereof.

20. The electrode assembly of claim 19 wherein the methanol and water are mixed together in about equal molar amounts, and wherein the acid is in amount of about 0.25 M.

50. The electrode assembly of claim 1, further comprising a spacing structure, wherein the spacing structure spans across the spaced apart region and connects the anode to the cathode.

52. A hydrogen or hydrocarbon fuel cell, comprising the electrode assembly of claim 1 or 21.

21. An electrode assembly adapted for use with a fuel cell, comprising:

an anode derived from a first planar silicon substrate, wherein the anode has integrally associated therewith a plurality of anode sol-gel derived support structures;

an electrolyte;

a cathode derived from a second planar silicon substrate, wherein the cathode has integrally associated therewith a plurality of cathode sol-gel derived support structures;

wherein the anode and the cathode are spaced apart and substantially parallel to each other so as to define a spaced apart region, and wherein the electrolyte is interposed between the anode and the cathode.

22. The electrode assembly of claim 21 wherein the first and second planar silicon substrates are silicon wafers.

23. The electrode assembly of claim 21, further comprising a blocking media that is substantially impermeable to at least methanol and is substantially permeable to hydrogen atoms, wherein the blocking media is interposed between the anode and the cathode.

24. The electrode assembly of claim 23 wherein the blocking media is integrally connected to the cathode.

25. The electrode assembly of claim 23 wherein the blocking media comprises a metallic membrane.

26. The electrode assembly of claim 23 wherein the blocking media comprises palladium, niobium, tantalum, vanadium, or a combination thereof.

27. The electrode assembly of claim 23 wherein the blocking media is a plurality of proton conducting plugs.

28. The electrode assembly of claim 23 wherein the anode has a plurality of etched or micromachined flow channels.

29. The electrode assembly of claim 21 wherein each of the plurality of anode and cathode sol-gel derived support structures contains a solid porous rectangular region having a volume of about 3×

10<sup>−

4</sup> cm³.

30. The electrode assembly of claim 29 wherein the solid porous rectangular regions of the anode are nanoporous, mesoporous, and/or macroporous.

31. The electrode assembly of claim 29 wherein the solid porous rectangular regions of the anode are mesoporous, and wherein each of the plurality of mesoporous regions comprise a random array a sponge-like interconnected pores having an open cell structure.

32. The electrode assembly of claim 29 wherein the solid porous rectangular regions of the anode contain anode pore surfaces, wherein the anode pore surfaces have a catalyst thereon.

33. The electrode assembly of claim 32 wherein the catalyst comprises a plurality of noncontiguous chemisorbed metallic particles.

34. The electrode assembly of claim 32 wherein the catalyst comprises a chemisorbed bi-metallic catalyst derived from platinum and ruthenium percursors.

35. The electrode assembly of claim 21 wherein the cathode has a plurality of etched or micromachined flow channels.

36. The electrode assembly of claim 29 wherein the solid porous rectangular regions of the cathode are nanoporous, mesoporous, and/or macroporous.

37. The electrode assembly of claim 36 wherein the solid porous rectangular regions of the cathode are mesoporous, wherein each of the plurality of mesoporous regions comprise a random array of sponge-like interconnected pores having an open cell structure.

38. The electrode assembly of claim 37 wherein the solid porous rectangular regions of the cathode contain cathode pore surfaces, wherein the cathode pore surfaces have a catalyst thereon.

39. The electrode assembly of claim 38 wherein the catalyst comprises a plurality of noncontiguous chemisorbed metallic particles.

40. The electrode assembly of claim 38 wherein the catalyst comprises a chemisorbed metallic catalyst derived from a platinum percursor.

41. The electrode assembly of claim 21 wherein the electrolyte comprises a solid polymer electrolyte.

42. The electrode assembly of claim 41 wherein the solid polymer electrolyte comprises a perfluorosulfonic polymer membrane.

43. The electrode assembly of claim 32 wherein the anode pore surfaces having a catalyst thereon, further include at least a portion of the electrolyte thereon, wherein the electrolyte comprises a solid polymer electrolyte.

44. The electrode assembly of claim 43 wherein the solid polymer electrolyte is a thin film having a thickness ranging from about 0.05 to about 0.5 microns.

45. The electrode assembly of claim 38 wherein the cathode pore surfaces having a catalyst thereon, further include at least a portion of the electrolyte thereon, wherein the electrolyte comprises a solid polymer electrolyte.

46. The electrode assembly of claim 45 wherein the solid polymer electrolyte is a thin film having a thickness ranging from about 0.05 to about 0.5 microns.

47. The electrode assembly of claim 21 wherein the electrolyte comprises first and second solid polymer electrolyte coatings and an acid, wherein the first solid polymer electrolyte coating is on the anode, and wherein the second solid polymer coating is on the cathode, and wherein the acid is contained in an organic fuel that flows through the anode and the spaced apart region.

48. The electrode assembly of claim 47 wherein the organic fuel comprises water and an alcohol selected from the group consisting ethanol, propanol, methanol, or a combination thereof, and the acid is phosphoric acid, sulfuric acid, or a combination thereof.

49. The electrode assembly of claim 48 wherein the methanol and water are mixed together in about equal molar amounts, and wherein the acid is in amount of about 0.25 M.

51. The electrode assembly of claim 21, further comprising a spacing structure, wherein the spacing structure spans across the spaced apart region and connects the anode to the cathode.

53. An electrode assembly adapted for use with a fuel cell, comprising:

anode derived from a first planar silicon substrate;

an electrolyte;

a cathode derived from a second planar silicon substrate;

wherein the anode and the cathode are spaced apart and substantially parallel to each other so as to define a spaced apart region, and wherein the electrolyte is interposed between the anode and the cathode, and wherein the anode and the cathode each have a plurality of porous regions that define anode pore surfaces and cathode pore surfaces, and wherein the anode pore surfaces and the cathode pore surfaces each have a catalyst dispersed thereon such that the catalyst is noncontiguously dispersed throughout the plurality of porous regions of the anode and the cathode, and wherein the anode and the cathode each have been doped such that the anode and the cathode are each capable of functioning as a current conductor.

54. An electrode assembly adapted for use with a fuel cell, comprising:

anode derived from a first planar silicon substrate;

an electrolyte;

a cathode derived from a second planar silicon substrate;

wherein the anode and the cathode are spaced apart and substantially parallel to each other so as to define a spaced apart region, and wherein the electrolyte is interposed between the anode and the cathode, and wherein the anode and the cathode each have a plurality of porous regions that are separated from one another by a plurality of nonporous silicon regions and that define anode pore surfaces and cathode pore surfaces, and wherein the anode pore surfaces and the cathode pore surfaces each have a catalyst dispersed thereon such that the catalyst is noncontiguously dispersed throughout the plurality of porous regions of the anode and the cathode.

55. An electrode assembly adapted for use with a fuel cell, comprising:

anode derived from a first planar silicon substrate;

an electrolyte;

a cathode derived from a second planar silicon substrate;

wherein the anode and the cathode are spaced apart and substantially parallel to each other so as to define a spaced apart region, and wherein the electrolyte is interposed between the anode and the cathode, and wherein the anode and the cathode each have a plurality of porous regions that are separated from one another by a plurality of nonporous silicon regions and that define anode pore surfaces and cathode pore surfaces, and wherein the anode pore surfaces and the cathode pore surfaces each have a catalyst dispersed thereon such that the catalyst is noncontiguously dispersed throughout the plurality of porous regions of the anode and the cathode, and wherein the anode and the cathode each have been doped such that the anode and the cathode are each capable of serving as a current conductor.