Proton exchange membrane fuel cell power system

• US 6,218,035 B1
• Filed: 12/21/1999
• Issued: 04/17/2001
• Est. Priority Date: 11/20/1997
• Status: Expired due to Term

• Current Assignee: Emergent Power Inc. (Plug Power Inc.)
• Original Assignee: Avista Laboratories Inc. (Plug Power Inc.)
• Inventors: DeVries, Peter David, Somers, Gregory M., Stokes, Ronald G., Lloyd, Greg Alden, Lott, David R., Fuglevand, William A., Bayyuk, Shiblihanna I., Scartozzi, John P.
• Primary Examiner(s): KALAFUT, STEPHEN J
• Application Number:
  US09/470,321
• Time in Patent Office: 483 Days
• Field of Search: 429/30, 429/33, 429/41, 429/42, 429/44
• US Class Current: 429/480
• CPC Class Codes: H01M 8/0247 characterised by the form characterised by a channel configuration H01M8/0258
• CPC Class Codes: H01M 8/04097 with recycling of the reactants H01M8/04119, H01M8/04104 take precedence
• CPC Class Codes: H01M 8/04141 by water containing exhaust gases
• CPC Class Codes: H01M 8/04335 of cathode reactants at the inlet or inside the fuel cell
• CPC Class Codes: H01M 8/04753 of fuel cell reactants
• CPC Class Codes: H01M 8/04835 of fuel cell reactants
• CPC Class Codes: H01M 8/2475 Enclosures, casings or containers of fuel cell stacks
• CPC Class Codes: H01M 8/249 comprising two or more groupings of fuel cells, e.g. modular assemblies
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

A proton exchange membrane fuel cell power system for producing electrical power is described and which includes a plurality of discrete fuel cell modules having at least two membrane electrode diffusion assemblies, each of the membrane electrode diffusion assemblies having opposite anode and cathode sides; a pair of current collectors are individually disposed in juxtaposed ohmic electrical contact with opposite anode and cathode sides of each of the membrane electrode diffusion assemblies; and individual force application assemblies apply a given force to the pair current collectors and the individual membrane electrode diffusion assemblies. The proton exchange membrane fuel cell power system also includes an enclosure mounting a plurality of subracks which receive the discrete fuel cell modules. Additionally, a control system is disclosed which optimizes the performance parameters of the discrete proton exchange membrane fuel cell modules.

Claims

1. A membrane electrode diffusion assembly comprising:

an electrolyte membrane having opposing first and second surfaces;

a catalytic anode having opposing first and second surfaces, and wherein the first surface of said catalytic anode is placed in ionic contact with said first surface of said electrolyte membrane;

a catalytic cathode having opposing first and second surfaces, and wherein the first surface of said catalytic cathode is placed in ionic contact with said second surface of said electrolyte membrane;

a first electrically conductive diffusion layer having first and second surfaces, and wherein the first surface of said diffusion layer is placed in ohmic electrical contact with the second surface of said catalytic anode;

a second electrically conductive diffusion layer having first and second surfaces, and wherein the first surface of said second diffusion laver is placed in ohmic electrical contact with the second surface of said catalytic cathode;

a third electrically conductive diffusion layer having first and second surfaces, and wherein the first surface of said third diffusion layer is placed in ohmic electrical contact with said second surface of said first diffusion layer;

a fourth electrically conductive diffusion layer having first and second surfaces, and wherein the first surface of said fourth diffusion layer is placed in ohmic electrical contact with said second surface of said second diffusion layer; and

wherein additional diffusion layers are placed in ohmic electrical contact on the second surface of the third and fourth diffusion layers.

2. A membrane electrode diffusion assembly comprising:

an electrolyte membrane having opposing first and second surfaces;

a catalytic anode having opposing first and second surfaces, and wherein the first surface of said catalytic anode is placed in ionic contact with said first surface of said electrolyte membrane;

a catalytic cathode having opposing first and second surfaces, and wherein the first surface of said catalytic cathode is placed in ionic contact with said second surface of said electrolyte membrane;

a first electrically conductive diffusion layer having first and second surfaces, and wherein the first surface of said diffusion layer is placed in ohmic electrical contact with the second surface of said catalytic anode;

a second electrically conductive diffusion layer having first and second surfaces, and wherein the first surface of said second diffusion layer is placed in ohmic electrical contact with the second surface of said catalytic cathode;

a third electrically conductive diffusion layer having first and second surfaces, and wherein the first surface of said third diffusion layer is placed in ohmic electrical contact with said second surface of said first diffusion layer;

a fourth electrically conductive diffusion layer having first and second surfaces, and wherein the first surface of said fourth diffusion layer is placed in ohmic electrical contact with said second surface of said second diffusion layer; and

a binding agent positioned between the first and second diffusion layers, and the third and fourth diffusion layers.

3. A membrane electrode diffusion assembly comprising:

an electrolyte membrane having opposing first and second surfaces;

a catalytic anode having opposing first and second surfaces, and wherein the first surface of said catalytic anode is placed in ionic contact with said first surface of said electrolyte membrane;

a catalytic cathode having opposing first and second surfaces, and wherein the first surface of said catalytic cathode is placed in ionic contact with said second surface of said electrolyte membrane;

a first electrically conductive diffusion layer having first and second surfaces, and wherein the first surface of said diffusion layer is placed in ohmic electrical contact with the second surface of said catalytic anode;

a second electrically conductive diffusion layer having first and second surfaces, and wherein the first surface of said second diffusion layer is placed in ohmic electrical contact with the second surface of said catalytic cathode;

a third electrically conductive diffusion layer having first and second surfaces, and wherein the first surface of said third diffusion laver is placed in ohmic electrical contact with said second surface of said first diffusion layer;

a fourth electrically conductive diffusion layer having first and second surfaces, and wherein the first surface of said fourth diffusion layer is placed in ohmic electrical contact with said second surface of said second diffusion layer, and wherein

the third and fourth diffusion layers comprise a porous hydrophobic lamina, and wherein the porous hydrophobic lamina is coated with a liquid suspension comprising about 95% to about 99% by weight of water;

about 1% to about 5% by weight of alcohol; and

about 1% to about 5% by weight of a compatible surfactant.

4. A membrane electrode diffusion assembly comprising:

an electrolyte membrane having opposing first and second surfaces;

a catalytic anode having opposing first and second surfaces, and wherein the first surface of said catalytic anode is placed in ionic contact with said first surface of said electrolyte membrane;

a catalytic cathode having opposing first and second surfaces, and wherein the first surface of said catalytic cathode is placed in ionic contact with said second surface of said electrolyte membrane;

a first electrically conductive diffusion layer having first and second surfaces, and wherein the first surface of said diffusion layer is placed in ohmic electrical contact with the second surface of said catalytic anode;

a second electrically conductive diffusion layer having first and second surfaces, and wherein the first surface of said second diffusion layer is placed in ohmic electrical contact with the second surface of said catalytic cathode;

a third electrically conductive diffusion layer having first and second surfaces, and wherein the first surface of said third diffusion layer is placed in ohmic electrical contact with said second surface of said first diffusion layer;

a fourth electrically conductive diffusion layer having first and second surfaces, and wherein the first surface of said fourth diffusion layer is placed in ohmic electrical contact with said second surface of said second diffusion layer, and wherein the first and second diffusion layers comprise a composite of successive coatings, and wherein each of the successive coatings has a specific degree of hydrophobicity, and wherein the first and second diffusion layers have a hydrophobic gradient, and wherein the hydrophobic gradient is established by adjusting the hydrophobicity of the successive coatings forming the composite.

5. A membrane electrode diffusion assembly as claimed in 4, wherein the successive coatings closest to the third and fourth diffusion layers are the least hydrophobic of all the successive coatings.

6. A membrane electrode diffusion assembly as claimed in 4, wherein the successive coatings closest to the third and fourth diffusion layers are the most hydrophobic of all the successive coatings.

7. A membrane electrode diffusion assembly comprising:

an electrolyte membrane having opposing first and second surfaces;

a catalytic anode having opposing first and second surfaces, and wherein the first surface of said catalytic anode is placed in ionic contact with said first surface of said electrolyte membrane;

a catalytic cathode having opposing first and second surfaces, and wherein the first surface of said catalytic cathode is placed in ionic contact with said second surface of said electrolyte membrane;

a first electrically conductive diffusion layer having first and second surfaces, and wherein the first surface of said diffusion layer is placed in ohmic electrical contact with the second surface of said catalytic anode;

a second electrically conductive diffusion layer having first and second surfaces, and wherein the first surface of said second diffusion layer is placed in ohmic electrical contact with the second surface of said catalytic cathode;

a third electrically conductive diffusion layer having first and second surfaces, and wherein the first surface of said third diffusion layer is placed in ohmic electrical contact with said second surface of said first diffusion layer;

a fourth electrically conductive diffusion layer having first and second surfaces, and wherein the first surface of said fourth diffusion layer is placed in ohmic electrical contact with said second surface of said second diffusion layer; and

wherein the third and fourth diffusion layers comprise a porous hydrophobic lamina which are coated with a liquid suspension comprising about 95% to about 99% by weight of water; and

about 1% to about 5% by weight of a surfactant.

8. A membrane electrode diffusion assembly comprising:

an electrolyte membrane having opposing first and second surfaces;

a catalytic anode having opposing first and second surfaces, and wherein the first surface of said catalytic anode is placed in ionic contact with said first surface of said electrolyte membrane;

a catalytic cathode having opposing first and second surfaces, and wherein the first surface of said catalytic cathode is placed in ionic contact with said second surface of said electrolyte membrane;

a first electrically conductive diffusion layer having first and second surfaces, and wherein the first surface of said diffusion layer is placed in ohmic electrical contact with the second surface of said catalytic anode;

a second electrically conductive diffusion laver having first and second surfaces, and wherein the first surface of said second diffusion layer is placed in ohmic electrical contact with the second surface of said catalytic cathode;

a third electrically conductive diffusion layer having first and second surfaces, and wherein the first surface of said third diffusion layer is placed in ohmic electrical contact with said second surface of said first diffusion layer;

a fourth electrically conductive diffusion layer having first and second surfaces, and wherein the first surface of said fourth diffusion layer is placed in ohmic electrical contact with said second surface of said second diffusion layer, and wherein the first and second diffusion layers comprise a composite of successive coatings, and wherein each of the successive coatings has a specific degree of hydrophobicity, and wherein the first and second diffusion layers have a hydrophobic gradient, and wherein the hydrophobic gradient is established by adjusting the hydrophobicity of the successive coatings forming the composite, and wherein the successive coatings closest to the third and fourth diffusion layers are the least hydrophobic of all the successive coatings.

9. A membrane electrode diffusion assembly comprising:

an electrolyte membrane having opposing first and second surfaces;

a catalytic anode having opposing first and second surfaces, and wherein the first surface of said catalytic anode is placed in ionic contact with said first surface of said electrolyte membrane;

a catalytic cathode having opposing first and second surfaces, and wherein the first surface of said catalytic cathode is placed in ionic contact with said second surface of said electrolyte membrane;

a first electrically conductive diffusion layer having first and second surfaces, and wherein the first surface of said diffusion layer is placed in ohmic electrical contact with the second surface of said catalytic anode;

a second electrically conductive diffusion layer having first and second surfaces, and wherein the first surface of said second diffusion layer is placed in ohmic electrical contact with the second surface of said catalytic cathode;

a third electrically conductive diffusion layer having first and second surfaces, and wherein the first surface of said third diffusion layer is placed in ohmic electrical contact with said second surface of said first diffusion layer;

a fourth electrically conductive diffusion layer having first and second surfaces, and wherein the first surface of said fourth diffusion layer is placed in ohmic electrical contact with said second surface of said second diffusion layer, and wherein the first and second diffusion layers comprise a composite of successive coatings, and wherein each of the successive coatings has a specific degree of hydrophobicity, and wherein the first and second diffusion layers have a hydrophobic gradient, and wherein the hydrophobic gradient is established by adjusting the hydrophobicity of the successive coatings forming the composite, and wherein the successive coatings closest to the third and fourth diffusion layers are the most hydrophobic of all the successive coatings.

10. A membrane electrode diffusion assembly comprising:

an electrolyte membrane having opposing first and second surfaces;

a catalytic anode having opposing first and second surfaces, and wherein the first surface of said catalytic anode is placed in ionic contact with said first surface of said electrolyte membrane;

a catalytic cathode having opposing first and second surfaces, and wherein the first surface of said catalytic cathode is placed in ionic contact with said second surface of said electrolyte membrane;

a first electrically conductive diffusion layer having first and second surfaces, and wherein the first surface of said diffusion layer is placed in ohmic electrical contact with the second surface of said catalytic anode;

a second electrically conductive diffusion layer having first and second surfaces, and wherein the first surface of said second diffusion layer is placed in ohmic electrical contact with the second surface of said catalytic cathode;

a third electrically conductive diffusion layer having first and second surfaces, and wherein the first surface of said third diffusion layer is placed in ohmic electrical contact with said second surface of said first diffusion layer;

a fourth electrically conductive diffusion layer having first and second surfaces, and wherein the first surface of said fourth diffusion layer is placed in ohmic electrical contact with said second surface of said second diffusion layer, and wherein the diffusion layers disposed on the catalytic cathode side of the membrane electrode diffusion assembly have different diffusion characteristics from the diffusion layers disposed on the catalytic anode side.

11. A membrane electrode diffusion assembly comprising:

an electrolyte membrane having opposing first and second substantially planar surfaces;

a catalytic anode having opposing first and second substantially planar surfaces;

said first planar surface of said catalytic anode placed into ionic contact with said first planar surface of said electrolyte membrane;

a catalytic cathode having opposing first and second substantially planar surfaces;

said first planar surface of said catalytic cathode placed into ionic contact with said second planar surface of said electrolyte membrane;

a first electrically conductive diffusion layer placed in ohmic electrical contact with the second planar surface of said catalytic anode; and

a second electrically conductive diffusion layer placed in ohmic electrical contact with the second planar surface of said catalytic cathode, and wherein at least one of the first or second diffusion layers has a hydrophobic gradient.

12. A membrane electrode diffusion assembly as claimed in 11, wherein said first diffusion layer has the hydrophobic gradient.

13. A membrane electrode diffusion assembly as claimed in 11, wherein said second diffusion layer has the hydrophobic gradient.

14. A membrane electrode diffusion assembly as claimed in 11, wherein both the first and second diffusion layers have the hydrophobic gradient.

15. A membrane electrode diffusion assembly as claimed in 11, wherein said first and second diffusion layers are hydrophobic;

and wherein the first and second diffusion layers are a composite formed of successive coatings which each have a variable degree of hydrophobicity; and

wherein the overall hydrophobicity of the first and second layers is established by adjusting the hydrophobicity of the respective successive coatings.

16. A membrane electrode diffusion assembly as claimed in 15, wherein the last of said hydrophobic coatings is the least hydrophobic.

17. A membrane electrode diffusion assembly as claimed in 15, wherein the last of said hydrophobic coatings is the most hydrophobic.

18. A membrane electrode diffusion assembly as claimed in 11, wherein the individual catalytic anode and catalytic cathode electrodes comprise:

particulate carbon;

a catalyst; and

a cross-linked copolymer incorporating sulfonic acid groups.

19. A membrane electrode diffusion assembly as claimed in 11, wherein the electrolyte membrane has a surface area, and the catalytic anode and the catalytic cathode have respective surface areas which are less than the surface area of the electrolyte membrane.

20. A membrane electrode diffusion assembly, comprising:

an electrolyte membrane having opposing first and second surfaces;

a catalytic anode having opposing first and second surfaces;

said first surface of said catalytic anode placed into ionic contact with said first surface of said electrolyte membrane;

a catalytic cathode having opposing first and second planar surfaces placed into ionic contact with said second planar surface of said electrolyte membrane;

a first electrically conductive diffusion layer placed into ohmic electrical contact with the second planar surface of said catalytic anode; and

a second electrically conductive diffusion layer placed into ohmic electrical contact with the second planar surface of said catalytic cathode, and wherein a binding agent is placed between at least one of the diffusion layers and the underlying catalytic anode or catalytic cathode.

21. A membrane electrode diffusion assembly as claimed in 20, wherein the binding agent is positioned between said catalytic anode and said first diffusion layer.

22. A membrane electrode diffusion assembly as claimed in 20, wherein the binding agent is positioned between said catalytic cathode and said second diffusion layer.

23. A membrane electrode diffusion assembly as claimed in 20, wherein the binding agent is positioned between said catalytic anode and said first diffusion layer, and between said catalytic cathode and said second diffusion layer.

24. A membrane electrode diffusion assembly as claimed in 20, wherein the binding agent is a synthetic.

25. A membrane electrode diffusion assembly as claimed in 24, wherein the binding agent is a thermoplastic.

26. A membrane electrode diffusion assembly as claimed in 20, wherein the binding agent is selected from the group consisting essentially of polyethylene and wax.

27. A membrane electrode diffusion assembly as claimed in 20, wherein the binding agent is substantially hydrophobic and is selected from the group consisting essentially of perflourinated hydrocarbons;

and wherein the first and second diffusion layers have about 20% to about 90%, by weight, of particulate carbon.

28. A membrane electrode diffusion assembly as claimed in 20, wherein the individual catalytic anode and catalytic cathode comprise:

particulate carbon;

a catalyst; and

a cross-linked copolymer incorporating sulfonic acid groups.

29. A membrane electrode diffusion assembly as claimed in 20, wherein the electrolyte membrane has a surface area, and the catalytic anode and the catalytic cathode have individual surface areas which are less than the surface area of the electrolyte membrane.