Reduction of SOFC anodes to extend stack lifetime

• US 20060222929A1
• Filed: 04/01/2005
• Published: 10/05/2006
• Est. Priority Date: 04/01/2005
• Status: Active Grant

• Current Assignee: Bloom Energy Corporation
• Original Assignee: Bloom Energy Corporation
• Inventors: Hickey, Darren, Karuppaiah, Chockkalingam, McElroy, James
• Granted Patent: US 7,514,166 B2
• Time in Patent Office: Days
• US Class Current: 429/413
• CPC Class Codes: H01M 2008/1293 Fuel cells with solid oxide electrolytes
• CPC Class Codes: H01M 4/8621 containing only metallic or ceramic material, e.g. made by sintering or sputtering
• CPC Class Codes: H01M 4/8878 Treatment steps after deposition of the catalytic active composition or after shaping of the electrode being free-standing body
• CPC Class Codes: H01M 4/9066 of metal-ceramic composites or mixtures, e.g. cermets
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

One embodiment of the invention provides a method of operating a solid oxide fuel cell, including providing a solid oxide fuel cell comprising an anode electrode containing nickel, and electrochemically reducing an anode side of the fuel cell. Another embodiment of the invention provides a method of operating a solid oxide fuel cell, including providing a solid oxide fuel cell comprising an anode electrode containing nickel, periodically operating the fuel cell to generate electricity, and reducing an anode side of the fuel cell between electricity generation operation periods of the fuel cell.

Claims

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

providing a solid oxide fuel cell comprising an anode electrode comprising nickel; and

electrochemically reducing an anode side of the fuel cell.

2. The method of claim 1, wherein the fuel cell comprises a non-reversible solid oxide fuel cell.

3. The method of claim 2, wherein the anode electrode comprises a cermet comprising the nickel and ceria.

4. The method of claim 3, wherein:

the ceria in the anode electrode cermet comprises gadolinia doped ceria;

the anode electrode cermet further comprises doped zirconia; and

the solid oxide fuel cell further comprises an ionically conductive ceramic electrolyte and an electrically conductive cathode electrode.

5. The method of claim 1, wherein the step of electrochemically reducing is conducted prior to electricity generation operation of the fuel cell.

6. The method of claim 5, wherein:

at least a portion of the nickel in the anode electrode is in a form of nickel oxide prior to the step of electrochemically reducing; and

at least a portion of the nickel oxide is reduced to nickel during the step of electrochemically reducing.

7. The method of claim 1, wherein the step of electrochemically reducing is conducted on at least one of the anode electrode and an anode contact layer between electricity generation operation periods of the fuel cell.

8. The method of claim 7, wherein the step of electrochemically reducing is conducted a plurality of times at predetermined periodic intervals.

9. The method of claim 7, further comprising detecting at least one of when a voltage generated by a fuel cell stack containing the solid oxide fuel cell drops below a first predetermined voltage or when the fuel cell stack degradation rate reaches a second predetermined value.

10. The method of claim 9, wherein the step of electrochemically reducing is conducted after the at least one of when the voltage generated by the fuel cell stack containing the solid oxide fuel cell drops below the first predetermined voltage or when the fuel cell stack degradation rate reaches the second predetermined value.

11. The method of claim 1, wherein the step of electrochemically reducing comprises:

applying an external potential to the fuel cell; and

providing a humidified carrier gas to the anode side of the fuel cell.

12. The method of claim 11, wherein:

the external potential causes oxygen ions from nickel oxide present in the anode electrode to diffuse through an electrolyte of the fuel cell to a cathode electrode of the fuel cell to reduce the nickel oxide to nickel; and

water in the humidified carrier gas is preferentially reduced compared to a doped zirconia present in the anode electrode to at least partially protect the doped zirconia from being reduced during the step of electrochemically reducing.

13. The method of claim 11, wherein the humidified carrier gas comprises at least one of a humidified argon, hydrogen or nitrogen carrier gas.

14. The method of claim 11, further comprising providing an oxygen containing gas to the cathode electrode of the fuel cell.

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

providing a solid oxide fuel cell comprising an anode electrode comprising nickel;

periodically operating the fuel cell to generate electricity; and

reducing an anode side of the fuel cell between electricity generation operation periods of the fuel cell.

16. The method of claim 15, wherein the fuel cell comprises a non-reversible solid oxide fuel cell.

17. The method of claim 15, wherein the step of reducing is conducted a plurality of times at predetermined periodic intervals.

18. The method of claim 15, further comprising detecting at least one of when a voltage generated by a fuel cell stack containing the solid oxide fuel cell drops below a first predetermined voltage or when the fuel cell stack degradation rate reaches a second predetermined value, wherein the step of periodically reducing is conducted after the at least one of when the voltage generated by the fuel cell stack containing the solid oxide fuel cell drops below the first predetermined voltage or when the fuel cell stack degradation rate reaches the second predetermined value.

19. The method of claim 15, wherein the anode electrode comprises a cermet comprising the nickel and ceria.

20. The method of claim 19, wherein:

the ceria in the anode electrode cermet comprises gadolinia doped ceria;

the anode electrode cermet further comprises doped zirconia; and

the solid oxide fuel cell further comprises an ionically conductive ceramic electrolyte and an electrically conductive cathode electrode.

21. The method of claim 15, wherein the step of reducing the anode side of the fuel cell comprises electrochemically reducing at least one of the anode electrode and a nickel containing anode contact layer.

22. The method of claim 15, wherein the step of reducing the anode side of the fuel cell comprises providing hydrogen or a hydrogen containing gas to the anode side of the fuel cell to reduce at least one of the anode electrode and a nickel containing anode contact layer.

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

providing a solid oxide fuel cell comprising an anode electrode comprising nickel oxide; and

electrochemically reducing the nickel oxide in the anode electrode to nickel prior to electricity generation operation of the fuel cell.

24. The method of claim 23, wherein the fuel cell comprises a non-reversible solid oxide fuel cell.

25. The method of claim 24, wherein:

at least a portion of nickel in the anode electrode is in a form of the nickel oxide prior to the step of electrochemically reducing;

at least a portion of the nickel oxide is reduced to nickel during the step of electrochemically reducing; and

the anode electrode comprises a cermet comprising the nickel and ceria after the step of electrochemically reducing.

26. The method of claim 25, wherein:

the ceria in the anode electrode cermet comprises gadolinia doped ceria;

the anode electrode cermet further comprises doped zirconia; and

the solid oxide fuel cell further comprises an ionically conductive ceramic electrolyte and an electrically conductive cathode electrode.

27. The method of claim 23, further comprising:

after the step of electrochemically reducing the nickel oxide, periodically operating the fuel cell to generate electricity; and

further reducing the anode electrode between electricity generation operation periods of the fuel cell.