Sulfur tolerant composite cermet electrodes for solid oxide electrochemical cells

• US 4,702,971 A
• Filed: 05/28/1986
• Issued: 10/27/1987
• Est. Priority Date: 05/28/1986
• Status: Expired due to Fees

• Current Assignee: Siemens Westinghouse Power Corporation
• Original Assignee: Westinghouse Electric Corporation (Paramount Global (f/k/a ViacomCBS Inc.))
• Inventors: Isenberg, Arnold O.
• Primary Examiner(s): Niebling, John F.
• Assistant Examiner(s): Marquis, Steven P.
• Application Number:
  US06/867,860
• Time in Patent Office: 517 Days
• Field of Search: 42/30, 42/31, 42/41, 42/44, 42/45, 42/33
• US Class Current: 429/482
• CPC Class Codes: C25B 11/00 Electrodes; Manufacture thereof not otherwise provided for
• CPC Class Codes: C25B 9/19 with diaphragms
• CPC Class Codes: G01N 27/4075 Composition or fabrication of the electrodes and coatings thereon, e.g. catalysts
• CPC Class Codes: H01M 8/12 operating at high temperature, e.g. with stabilised ZrO2 electrolyte
• CPC Class Codes: Y02E 60/36 Hydrogen production from non-carbon containing sources, e.g. by water electrolysis
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

An electrochemical apparatus is made containing an exterior electrode bonded to the exterior of a tubular, solid, oxygen ion conducting electrolyte where the electrolyte is also in contact with an interior electrode, said exterior electrode comprising particles of an electronic conductor contacting the electrolyte, where a ceramic metal oxide coating partially surrounds the particles and is bonded to the electrolyte, and where a coating of an ionic-electronic conductive material is attached to the ceramic metal oxide coating and to the exposed portions of the particles.

Claims

1. An electrode bonded to a solid, ion conducting electrolyte, said electrode comprising:

(A) particles of an electronic conductor,

(B) an ion conducting ceramic metal oxide partially surrounding said particles, and bonded to the electrolyte, and

(C) an ionic-electronic conductive coating on said ion conducting ceramic metal oxide and exposed portions of the particles.

2. The electrode of claim 1, where the particles are metal particles, and the ionic-electronic conductive material comprises an oxide selected from the group consisting of ceria, doped ceria, urania, doped urania, and mixtures thereof.

3. The electrode of claim 1, where the electrolyte and the ion conducting ceramic metal oxide comprises stabilized zirconia.

4. The electrode of claim 1 where the ceramic metal oxide is an essentially only ionic conductive skeleton structure partially surrounding the particles, the ionic-electronic conductive material consists essentially of ceria, urania, doped ceria, doped urania and mixtures thereof where the dopant for ceria is selected from the group consisting of zirconia and thoria, the electrolyte and the ion conducting ceramic metal oxide consist essentially of stabilized zirconia, and where the ionic-electronic conductive material is effective to provide electrochemically active sites over its entire surface and sulfur stability while operating in the presence of sulfur and sulfur species.

5. An electrode bonded to a solid, oxygen ion conducting electrolyte, said electrode comprising particles of an electronic conductor partly embedded in a

skeletal member of an ion conducting ceramic metal oxide, where exposed surfaces of the particles and ion conducting skeletal member are coated with ionic-electronic conductive material.

6. The electrode of claim 5, bonded to an electrolyte comprising stabilized zirconia, and where the skeletal member comprises stabilized zirconia.

7. The electrode of claim 5, being an exterior electrode where the electrolyte is in tubular form and the electrolyte is also in contact with an interior electrode.

8. The electrode of claim 7, where the electrolyte and skeletal member each comprise yttria doped zirconia and the outer ionic-electronic conductive material comprises an oxide selected from the group consisting of ceria, doped ceria, urania, doped urania, and mixtures thereof.

9. The electrode of claim 5, wherein the particles are from about 1 micron to about 5 microns in size and are a metal selected from the group consisting of platinum, nickel, cobalt, gold, copper, iron, alloys thereof and mixtures thereof.

10. The electrode of claim 5, where the ionic-electronic material is capable of expanding and contracting independent of the other components of the electrode.

11. The electrode of claim 5, where the ionic-electronic conductive material has a thickness of from about 0.5 micron to about 20 microns and is continuous over the entire surface of the electrode.

12. The electrode of claim 5, where the ionic-electronic conductive material comprises an oxide selected from the group consisting of ceria, doped ceria, urania, doped urania, and mixtures thereof.

13. The electrode of claim 5, where the ionic-electronic conductive material comprises an oxide selected from the group of doped ceria, doped urania, and mixtures thereof and the dopant is an oxide selected from the group consisting of zirconium, yttrium, scandium, thorium, rare earth mettals, and mixtures thereof.

14. The electrode of claim 5 where the ionic-electronic conductive material is effective to provide electrochemically active sites over its entire surface, and sulfur stability while operating in the presence of sulfur and sulfur species.

15. The electrode of claim 5, where the electrolyte and skeletal member each comprise yttria doped zirconia.

16. The electrode of claim 5, where the ceramic metal oxide is essentially only ionic conductive, the ionic-electronic conductive material consists essentially of ceria, urania, doped ceria, doped urania and mixtures thereof where the dopant for ceria is selected from the group consisting of zirconia and thoria, and the electrolyte and the ion conducting ceramic metal oxide consist essentially of stabilized zirconia.

17. An exterior electrode bonded to the exterior of a tubular, solid, oxygen ion conducting electrolyte, where the electrolyte is also in contact with an interior electrode, said exterior electrode comprising particles of an electronic conductor partly embedded in a skeletal structure of dense, essentially only ionic conductive ceramic metal oxide, where the electrolyte and skeletal structure comprise stabilized zirconia, and where the particles and skeletal structure are contacted by a separate, ionic-electronic conductive coating which consists essentially of an oxide selected from the group consisting of ceria, doped ceria, urania, doped urania and mixtures thereof.

18. The exterior electrode of claim 17, where the ionic-electronic conductive outer coating oxide is doped with from about 1 mo1% to about 70 mo1% of an oxide selected from the group consisting of zirconium, yttrium, scandium, thorium, rare earth metals, and mixtures thereof, and where said coating is capable of expanding and contracting independent of the other components of the electrode.

19. The exterior electrode of claim 17, where the ionic-electronic conductive coating is effective to provide electrochemically active sites over its entire surface and sulfur stability while operating in the presence of sulfur and sulfur species, and the exterior electrode, electrolyte, and interior electrode are capable of functioning as a fuel cell or as an electrolysis cell.

20. The exterior electrode of claim 17, where the ionic-electronic conductive material consists essentially of ceria, urania, doped ceria, doped urania and mixtures thereof where the dopant for ceria is selected from the group consisting of zirconia and thoria.

21. A tubular electrochemical cell containing an exterior electrode bonded to the exterior of a tubular, solid, oxygen ion conducting electrolyte, where the electrolyte is also in contact with an interior electrode, said exterior electrode comprising particles of an electronic conductor partly embedded in a skeletal structure of a dense, essentially only ionic conductive ceramic metal oxide, where the electrolyte and skeletal structure comprise stabilized zirconia, and where the particles and skeletal structure are contacted by a separate, ionic-electronic conductive coating which consists essentially of an oxide selected from the group consisting of doped ceria, doped urania, and mixtures thereof.

22. The tubular cell of claim 21, where the conductive outer coating oxide is doped with from about 1 mol % to about 70 mol % of an oxide selected from the group zirconium, yttrium, scandium, thorium, rare earth metals, and mixtures thereof, where said outer coating is capable of expanding and contracting independent of the other components, and where said cell is capable of operating as a fuel cell or an an electrolysis cell.

23. The tubular cell of claim 21 where the ionic-electronic conductive material consists essentially of ceria, urania, doped ceria, doped urania and mixtures thereof where the dopant for ceria is selected from the group consisting of zirconia and thoria, and where the ionic-electronic conductive material is effective to provide electrochemically active sites over its entire surface, and sulfur stability while operating in the presence of sulfur and sulfur species.