SORFC system with non-noble metal electrode compositions

• US 7,150,927 B2
• Filed: 09/10/2003
• Issued: 12/19/2006
• Est. Priority Date: 09/10/2003
• Status: Active Grant

• Current Assignee: Bloom Energy Corporation
• Original Assignee: Bloom Energy Corporation
• Inventors: Russell, Ian, Hickey, Darren
• Primary Examiner(s): APICELLA, KARIE O
• Application Number:
  US10/658,275
• Publication Number:
  US 20050053812A1
• Time in Patent Office: 1,196 Days
• Field of Search: 429/12, 429/30, 429/46
• US Class Current: 429/411
• CPC Class Codes: H01M 4/8621 containing only metallic or ceramic material, e.g. made by sintering or sputtering
• CPC Class Codes: H01M 4/8885 Sintering or firing
• CPC Class Codes: H01M 4/9016 Oxides, hydroxides or oxygenated metallic salts
• CPC Class Codes: H01M 4/9033 Complex oxides, optionally doped, of the type M1MeO3, M1 being an alkaline earth metal or a rare earth, Me being a metal, e.g. perovskites
• CPC Class Codes: H01M 4/9066 of metal-ceramic composites or mixtures, e.g. cermets
• CPC Class Codes: H01M 8/04097 with recycling of the reactants H01M8/04119, H01M8/04104 take precedence
• CPC Class Codes: H01M 8/04164 by condensers, gas-liquid separators or filters
• CPC Class Codes: H01M 8/1253 the electrolyte containing zirconium oxide
• CPC Class Codes: H01M 8/126 the electrolyte containing cerium oxide
• CPC Class Codes: H01M 8/186 by electrolytic decomposition of the electrolytic solution or the formed water product
• CPC Class Codes: Y02E 60/50 Fuel cells
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product

Abstract

A solid oxide regenerative fuel cell includes a ceramic electrolyte, a first electrode which is adapted to be positively biased when the fuel cell operates in a fuel cell mode and in an electrolysis mode, and a second electrode which is adapted to be negatively biased when the fuel cell operates in the fuel cell mode and in the electrolysis mode. The second electrode comprises less than 1 mg/cm² of noble metal. By maintaining a reducing atmosphere on the second electrode at all times noble metals can be eliminated from the electrode composition which substantially reduces the cost of the fuel cell.

Claims

1. A method of operating a solid oxide regenerative fuel cell, comprising:

operating the solid oxide regenerative fuel cell in a fuel cell mode by providing a fuel to a negative electrode and providing an oxidizer to a positive electrode to generate electricity and water vapor at the negative electrode;

operating the solid oxide regenerative fuel cell in an electrolysis mode by providing electricity to the fuel cell and providing water vapor to the negative electrode to generate fuel at the negative electrode and oxygen at the positive electrode; and

providing a sufficient reducing atmosphere to the negative electrode when the solid oxide regenerative fuel cell operates in the electrolysis mode to prevent the negative electrode from oxidizing, wherein the negative electrode comprises no noble metal or an unavoidable trace impurity amount of noble metal.

2. The method of claim 1, wherein the fuel and the reducing atmosphere comprise hydrogen.

3. The method of claim 2, wherein the water to hydrogen ratio at the negative electrode during the electrolysis mode is 8 or less.

4. The method of claim 1, wherein the reducing atmosphere comprises forming gas.

5. The method of claim 1, wherein the reducing atmosphere comprises carbon monoxide.

6. The method of claim 1, wherein:

the positive electrode comprises at least one of LSM, LSCo, LCo, LSF, LSCoF, PSM or a combination thereof with an ionic conducting phase; and

the negative electrode comprises at least one of Ni, Cu, Fe or a combination thereof with an ionic conducting phase.

7. The method of claim 6, wherein:

the positive electrode consists essentially of LSM; and

the negative electrode consists essentially of a Ni—

YSZ cermet.

8. The method of claim 1, wherein the reducing atmosphere does not chemically participate in the electrolysis process and is cycled through the fuel cell without being consumed.

9. The method of claim 8, wherein the fuel cell is cycled between the fuel cell mode and the electrolysis mode at least 30 times.

10. The method of claim 9, further comprising:

generating hydrogen at the negative electrode in the electrolysis mode by electrolysis of water vapor;

providing remaining water vapor and the generated hydrogen to a water-hydrogen separator to separate the hydrogen from water;

providing the separated hydrogen to a compressor;

providing a first portion of the compressed hydrogen to a hydrogen storage vessel; and

providing a second portion of the compressed hydrogen to the negative electrode to maintain the sufficient reducing atmosphere at the negative electrode.

11. A method of operating a solid oxide regenerative fuel cell, comprising:

operating the solid oxide regenerative fuel cell in a fuel cell mode by providing a fuel to a negative electrode and providing an oxidizer to a positive electrode to generate electricity and water vapor at the negative electrode;

operating the solid oxide regenerative fuel cell in an electrolysis mode by providing electricity to the fuel cell and providing water vapor to the negative electrode to generate fuel at the negative electrode and oxygen at the positive electrode; and

providing a sufficient reducing atmosphere to the negative electrode when the solid oxide regenerative fuel cell operates in the electrolysis mode to prevent the negative electrode from oxidizing;

wherein;

the negative electrode comprises less than 1 mg/cm² of noble metal; and

the negative electrode comprises at least one of Ni, Cu, Fe or a combination thereof with an ionic conducting phase.

12. The method of claim 11, wherein the fuel and the reducing atmosphere comprise hydrogen.

13. The method of claim 12, wherein the water to hydrogen ratio at the negative electrode during the electrolysis mode is 8 or less.

14. The method of claim 11, wherein the reducing atmosphere comprises forming gas.

15. The method of claim 11, wherein the reducing atmosphere comprises carbon monoxide.

16. The method of claim 11, wherein the negative electrode comprises less than 20 weight percent of noble metal.

17. The method of claim 16, wherein the negative electrode comprises less than 0.1 mg/cm² of noble metal and less than 1 weight percent of noble metal.

18. The method of claim 17, wherein the negative electrode comprises no noble metal or an unavoidable trace impurity amount of noble metal.

19. The method of claim 18, wherein the positive electrode comprises at least one of LSM, LSCo, LCo, LSF, LSCoF, PSM or a combination thereof with an ionic conducting phase.

20. The method of claim 19, wherein:

the positive electrode consists essentially of LSM; and

the negative electrode consists essentially of a Ni—

YSZ cermet.

21. The method of claim 11, wherein the reducing atmosphere does not chemically participate in the electrolysis process and is cycled through the fuel cell without being consumed.

22. The method of claim 21, wherein the fuel cell is cycled between the fuel cell mode and the electrolysis mode at least 30 times.

23. The method of claim 22, further comprising:

generating hydrogen at the negative electrode in the electrolysis mode by electrolysis of water vapor;

providing remaining water vapor and the generated hydrogen to a water-hydrogen separator to separate the hydrogen from water;

providing the separated hydrogen to a compressor;

providing a first portion of the compressed hydrogen to a hydrogen storage vessel; and

providing a second portion of the compressed hydrogen to the negative electrode to maintain the sufficient reducing atmosphere at the negative electrode.

24. A method of operating a solid oxide regenerative fuel cell, comprising:

operating the solid oxide regenerative fuel cell in a fuel cell mode by providing a fuel to a negative electrode and providing an oxidizer to a positive electrode to generate electricity and water vapor at the negative electrode;

operating the solid oxide regenerative fuel cell in an electrolysis mode by providing electricity to the fuel cell and providing water vapor to the negative electrode to generate fuel at the negative electrode and oxygen at the positive electrode;

providing a sufficient reducing atmosphere to the negative electrode when the solid oxide regenerative fuel cell operates in the electrolysis mode to prevent the negative electrode from oxidizing, wherein the negative electrode comprises less than 1 mg/cm² of noble metal;

generating hydrogen at the negative electrode in the electrolysis mode by electrolysis of water vapor;

providing remaining water vapor and the generated hydrogen to a water-hydrogen separator to separate the hydrogen from water;

providing the separated hydrogen to a compressor;

providing a first portion of the compressed hydrogen to a hydrogen storage vessel; and

providing a second portion of the compressed hydrogen to the negative electrode to maintain the sufficient reducing atmosphere at the negative electrode.

25. The method of claim 24, wherein the fuel and the reducing atmosphere comprise hydrogen.

26. The method of claim 25, wherein the water to hydrogen ratio at the negative electrode during the electrolysis mode is 8 or less.

27. The method of claim 24, wherein the reducing atmosphere comprises forming gas.

28. The method of claim 24, wherein the reducing atmosphere comprises carbon monoxide.

29. The method of claim 24, wherein the negative electrode comprises less than 20 weight percent of noble metal.

30. The method of claim 29, wherein the negative electrode comprises less than 0.1 mg/cm² of noble metal and less than 1 weight percent of noble metal.

31. The method of claim 30, wherein the negative electrode comprises no noble metal or an unavoidable trace impurity amount of noble metal.

32. The method of claim 31, wherein:

the positive electrode comprises at least one of LSM, LSCo, LCo, LSF, LSCoF, PSM or a combination thereof with an ionic conducting phase; and

the negative electrode comprises at least one of Ni, Cu, Fe or a combination thereof with an ionic conducting phase.

33. The method of claim 32, wherein:

the positive electrode consists essentially of LSM; and

the negative electrode consists essentially of a Ni—

YSZ cermet.

34. The method of claim 24, wherein the reducing atmosphere does not chemically participate in the electrolysis process and is cycled through the fuel cell without being consumed.

35. The method of claim 34, wherein the fuel cell is cycled between the fuel cell mode and the electrolysis mode at least 30 times.