Electrochemical sensor with which to measure gas concentrations

• US 5,538,620 A
• Filed: 09/12/1994
• Issued: 07/23/1996
• Est. Priority Date: 11/11/1991
• Status: Expired due to Term

• Current Assignee: Advanced Technology Materials, Inc. (Entegris Incorporated)
• Original Assignee: Mst Micro-Sensor Technologie, GmbH
• Inventors: Nikolskaja, Elena
• Primary Examiner(s): Bell, Bruce F.
• Application Number:
  US08/232,084
• Time in Patent Office: 680 Days
• Field of Search: 204/431, 204/432, 204/415, 204/414, 204/421, 204/430, 204/412, 204/153.17, 204/153.16, 204/153.18, 422/88, 422/98
• US Class Current: 205/782
• CPC Class Codes: G01N 27/404 Cells with anode, cathode and cell electrolyte on the same side of a permeable membrane which separates them from the sample fluid , e.g. Clark-type oxygen sensors
• CPC Class Codes: G01N 27/4045 for gases other than oxygen

Abstract

The invention concerns a novel electrochemical sensor with which to measure gas concentrations and comprising a measuring electrode and an associated electrode containing a carbonaceous material with a specific surface of at least 40 m² /g and with electrochemically active surface compounds which can be reversibly oxidized/reduced.

Claims

1. An electrochemical sensor to determine a gas concentration of a gas to be quantified, comprising a housing, a measuring electrode located within the housing and comprising a catalytic material which causes a reaction of the gas to be quantified, an associated electrode located within the housing and comprising a carbonaceous material, and an electrolyte in contact with the measuring and associated electrodes,

wherein the carbonaceous material in the associated electrode has a specific surface of at least 40 m² /g and comprises reversibly oxidizable or reducible electrochemically active surface compounds.

2. The electrochemical sensor defined in claim 1, wherein the carbonaceouse material in the associated electrode is a porous, activated carbon with oxygenous, electrochemically active surface compounds.

3. The electrochemical sensor defined in claim 1, wherein the carbonaceous material in the associated electrode evinces a specific surface of 1000 to 3000 m² /g.

4. The electrochemical sensor defined in claim 1, wherein the catalytic material in the measuring electrode is selected from the group consisting of platinum, carbon and gold.

5. The electrochemical sensor defined in claim 1, wherein the electrochemically active surface compounds comprise hydroquinone or quinone.

6. The electrochemical sensor defined in claim 1, wherein the electrolyte is embedded in a solid matrix.

7. The electrochemical sensor defined in claim 1, wherein the housing comprises apertures for electrode terminals and a gas cell having intake apertures, the gas cell allowing the gas to be quantified to contact the measuring electrode.

8. The electrochemical sensor defined in claim 1, further comprising an ion-permeable separator located between the measuring electrode and associated electrode.

9. The electrochemical sensor defined in claim 1, wherein the housing comprises a gas cell and a gas-permeable diffusion membrane, wherein the gas-permeable diffusion membrane is located between the gas cell and the measuring electrode.

10. The electrochemical sensor defined in claim 1, wherein the gas to be quantified is ionized at the measuring electrode to form ions, and the electrolyte contains the ions which are generated in the gas ionization at the measuring electrode.

11. The electrochemical sensor defined in claim 1, wherein the sensor further comprises a reference electrode.

12. The electrochemical sensor defined in claim 1, wherein the sensor further comprises a supplement electrode.

13. The electrochemical sensor defined in claim 1, wherein the sensor comprises at least two measuring electrodes.

14. The electrochemical sensor defined in claim 1, wherein the electrolyte is a solid electrolyte comprising a polymer comprising an electrolytic solution.

15. The electrochemical sensor defined in claim 14, wherein the solid electrolyte comprises a polymer prepared by polymerization of at least one monomer and an electrolytic solution.

16. The electrochemical sensor defined in claim 15, wherein the monomer is methylmethacrylate, the electrolytic solution comprises at least one acid, and the solid electrolyte further comprises a polymerization initiator.

17. The electrochemical sensor defined in claim 16, wherein the electrolytic solution comprises at least one acid selected from the group consisting of sulfuric acid, trifluoromethane sulfonic acid and phosphoric acid.

18. A method for quantifying at least one gas, comprising:

providing an electrochemical sensor comprising a housing, a measuring electrode located within the housing and comprising a catalytic material which causes a reaction of the gas to be quantified, an associated electrode located within the housing and comprising a carbonaceous material, and an electrolyte in contact with the measuring and associated electrodes, wherein the carbonaceous material in the associated electrode has a specific surface of at least 40 m² /g and comprises reversibly oxidizable or reducible electrochemically active surface compounds;

exposing the electrochemical sensor to the gas to be quantified;

setting an external voltage across the measuring electrode and the associated electrode; and

measuring the current flowing between the measuring electrode and the associated electrode to quantify the gas to be quantified.

19. The method defined in claim 18, wherein the gas to be quantified is selected from the group consisting of hydrogen, oxygen, carbon monoxide and silane.

20. The method defined in claim 18, wherein the gas to be quantified is hydrogen, the measuring electrode comprises platinum, the associated electrode comprises activated carbon with a specific surface of 1000 to 1,700 m² /g, the electrolyte comprises a strong mineral acid, and the external voltage is about 0.3 volts.

21. The method defined in claim 18, further comprising regenerating the electrochemical sensor, after said measuring step, by reversing the external voltage set across the measuring electrode and the associated electrode.

22. An electrochemical sensor to determine a gas concentration of a gas to be quantified, comprising:

a housing comprising apertures for electrode terminals and a gas cell having intake apertures,

a measuring electrode located within the housing and comprising a catalytic material which causes a reaction of the gas to be quantified,

an associated electrode located within the housing and comprising a carbonaceous material,

an electrolyte in contact with the measuring and associated electrodes, and

an electrical means for applying a voltage across the measuring electrode and the associated electrode, the electrical means having electrode terminals located in the apertures in the housing,

wherein the gas cell allows the gas to be quantified to contact the measuring electrode,

and wherein the carbonaceous material in the associated electrode has a specific surface of at least 40 m² /g and comprises reversibly oxidizable or reducible electrochemically active surface compounds.