Method and apparatus for selectively removing oxygen using a non-catalytic electrode in an electrochemical cell

• US 6,565,737 B2
• Filed: 12/14/2000
• Issued: 05/20/2003
• Est. Priority Date: 12/14/2000
• Status: Expired due to Fees

• Current Assignee: Battelle Memorial Institute
• Original Assignee: Battelle Memorial Institute
• Inventors: Marina, Olga A., Habeger, Craig F.
• Primary Examiner(s): Phasge, Arun S.
• Application Number:
  US09/741,223
• Publication Number:
  US 20020108863A1
• Time in Patent Office: 887 Days
• Field of Search: 205/765, 205/781, 204/252, 204/421, 204/424, 204/425, 204/426, 204/431, 204/432
• US Class Current: 205/765
• CPC Class Codes: B01D 53/326 in electrochemical cells
• CPC Class Codes: H01M 8/0662 Treatment of gaseous reactants or gaseous residues, e.g. cleaning
• CPC Class Codes: H01M 8/1231 with both reactants being gaseous or vaporised
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

A method and apparatus for selectively removing oxygen from a gas stream containing NO_x and oxygen by contacting the gas stream with an electrochemical cell made from an electrode consisting of La_1-XM_XFeO₃, (where M is selected from the group consisting of Sr, Ba, Ca, and combinations thereof, and X is between 0.05 and 0.5), a solid oxide electrolyte and a counter electrode, wherein the La_1-XM_XFeO₃ electrode is on one side of a solid oxide electrolyte, and a counter electrode is on the opposite side of the solid oxide electrolyte, and applying a voltage to the electrochemical cell. The apparatus is preferably employed in a two chambered NO_x sensor utilizing solid electrolyte electrochemical cells, wherein an electrochemical cell capable of catalyzing oxygen reduction without catalyzing NO_x decomposition is formed as integral to the first chamber.

Claims

1. A method of selectively removing oxygen from a gas stream containing NO_x and oxygen comprising the steps of:

a) contacting the gas stream with an electrochemical cell comprising an electrode consisting of La_1-XM_XFeO₃, where M is selected from the group consisting of Sr, Ba, Ca, and combinations thereof, and X is between 0.05 and 0.5, wherein the electrode is on one side of a solid oxide electrolyte, and wherein a counter electrode is on the opposite side of the solid oxide electrolyte, and

b) applying a voltage to the electrochemical cell.

2. The method of claim 1 wherein said counter electrode is a metal stable in air at the operating temperature of the electrochemical cell.

3. The method of claim 1 wherein X is about 0.2.

4. The method of claim 1 wherein the solid oxide electrolyte is provided as stabilized zirconia.

5. An electrochemical cell for selectively removing oxygen from a gas stream containing NO_x and oxygen comprising:

a) an electrode consisting of La_1-XM_XFeO₃, where M is selected from the group consisting of Sr, Ba, Ca, and combinations thereof, and X is between 0.05 and 0.5,

b) the electrode being affixed to one side of a solid oxide electrolyte,

c) a counter electrode affixed to the opposite side of the solid oxide electrolyte.

6. The electrochemical cell of claim 5 wherein the counter electrode is a metal stable in air at the operating temperature of the electrochemical cell.

7. The electrochemical cell of claim 5 wherein X is about 0.2.

8. The electrochemical cell of claim 5 wherein the solid oxide electrolyte is stabilized zirconia.

9. An improvement to a two chambered NO_x sensor utilizing solid electrolyte electrochemical cells, the improvement comprising forming an electrochemical cell with an electrode capable of catalyzing oxygen reduction without catalyzing NO_x decomposition as integral to the first chamber of the two chambered NO_x sensor.

10. The improved NO_x sensor of claim 9 wherein said electrochemical cell comprises:

a) an electrode consisting of La_1-XM_XFeO₃, where M is selected from the group consisting of Sr, Ba, Ca, and combinations thereof, and X is between 0.05 and 0.5,

b) the electrode being affixed to one side of a solid oxide electrolyte, and

c) a counter electrode affixed to the opposite side of the solid oxide electrolyte.

11. The improved NO_x sensor of claim 10 wherein said counter electrode is a metal stable in air at the operating temperature of the electrochemical cell.

12. The improved NO_x sensor of claim 10 wherein X is about 0.2.

13. The electrochemical cell of claim 10 wherein the solid oxide electrolyte is stabilized zirconia.