SOLID STATE ELECTROCHEMICAL GAS SENSOR AND METHOD FOR FABRICATING SAME

• US 20070102294A1
• Filed: 09/20/2006
• Published: 05/10/2007
• Est. Priority Date: 11/08/2005
• Status: Active Grant

• Current Assignee: Integrated Device Technology Incorporated (Renesas Electronics Corporation)
• Original Assignee: Synkera Technologies (Renesas Electronics Corporation)
• Inventors: Kostelecky, Clayton, Dorisio Deininger, Debra
• Granted Patent: US 7,918,977 B2
• Time in Patent Office: Days
• US Class Current: 204/421
• CPC Class Codes: G01N 27/4071 using sensor elements of laminated structure
• CPC Class Codes: G01N 27/4074 for detection of gases other than oxygen
• CPC Class Codes: G01N 33/004 for CO, CO2
• CPC Class Codes: G01N 33/0044 for H2S, sulfides
• CPC Class Codes: G01N 33/0047 for organic compounds

Abstract

An electrochemical gas sensor, a method for making the sensor and methods for the detection of a gaseous species. The electrochemical gas sensor is a solid-state gas sensor that includes a solid polymer electrolyte. A working electrode is separated from a counter electrode by the solid polymer electrolyte. The sensor can include a multilaminate structure for improved detection properties, where electrode microbands are disposed within the solid polymer electrolyte.

Claims

1. An electrochemical sensor, comprising:

a) a solid polymer electrolyte comprising a solid polymer matrix and a salt dispersed within said solid polymer matrix;

b) a working electrode contacting said solid polymer electrolyte; and

c) a counter electrode contacting said solid polymer electrolyte,

wherein said working electrode is separated from said counter electrode by said solid polymer electrolyte.

2. An electrochemical sensor as recited in claim 1, wherein said solid polymer matrix is selected from the group consisting of poly(oxides), poly(vinyl ethers), polyvinylpyrrolidone, poly(acrylics), poly(methacrylics) and polyvinyl alcohol.

3. An electrochemical sensor as recited in claim 1, wherein said solid polymer matrix comprises a poly(oxide).

4. An electrochemical sensor as recited in claim 1, wherein said solid polymer matrix comprises poly(ethylene oxide).

5. An electrochemical sensor as recited in claim 1, wherein said solid polymer matrix is substantially amorphous.

6. An electrochemical sensor as recited in claim 1, wherein said solid polymer matrix has a molecular weight of at least about 100,000 and not greater than about 10,000,000.

7. An electrochemical sensor as recited in claim 1, wherein said salt is a monovalent cation salt.

8. An electrochemical sensor as recited in claim 1, wherein said salt is an inorganic salt selected from the group consisting of a lithium salt, a sodium salt, an ammonium salt and a magnesium salt.

9. An electrochemical sensor as recited in claim 1, wherein said salt is selected from the group consisting of lithium perchlorate, lithium tetrafluorborate, lithium chloride, sodium chlorate, sodium perchlorate, sodium tetrafluroborate, ammonium tetrafluorborate and ammonium perchlorate.

10. An electrochemical sensor as recited in claim 1, wherein said salt comprises lithium perchlorate.

11. An electrochemical sensor as recited in claim 1, wherein said solid polymer electrolyte comprises at least about 2 wt. % of said salt.

12. An electrochemical sensor as recited in claim 11, wherein said solid polymer electrolyte comprises not greater than about 25 wt. % of said salt.

13. An electrochemical sensor as recited in claim 1, wherein said solid polymer electrolyte comprises at least about 10 wt. % and not greater than about 15 wt. % of said salt.

14. An electrochemical sensor as recited in claim 1, wherein said solid polymer electrolyte further comprises inorganic particulates dispersed within said solid polymer matrix.

15. An electrochemical sensor as recited in claim 14, wherein said solid polymer electrolyte comprises at least about 3 wt. % and not greater than about 15 wt. % of said inorganic particulates.

16. An electrochemical sensor as recited in claim 14, wherein said inorganic particulates comprise metal oxide particulates.

17. An electrochemical sensor as recited in claim 16, wherein said inorganic particulates are selected from the group consisting of aluminum oxide, silica and titania.

18. An electrochemical sensor as recited in claim 14, wherein said inorganic particulates have an average particle size of not greater than about 1 μ

m.

19. An electrochemical sensor as recited in claim 14, wherein said inorganic particles have an average particle size of at least about 5 nanometers and not greater than about 500 nanometers.

20. An electrochemical sensor as recited in claim 1, wherein said working electrode comprises a material selected from the group consisting of gold, platinum, silver, palladium, ruthenium, iridium, carbon and mixtures thereof.

21. An electrochemical sensor as recited in claim 1, wherein said working electrode comprises a noble metal.

22. An electrochemical sensor as recited in claim 1, wherein said working electrode comprises gold.

23. An electrochemical sensor as recited in claim 1, wherein said working electrode comprises platinum.

24. An electrochemical sensor as recited in claim 1, wherein said working electrode comprises a material that is different than said counter electrode.

25. An electrochemical sensor as recited in claim 1, wherein said counter electrode comprises platinum.

26. An electrochemical sensor as recited in claim 1, wherein said counter electrode is also a reference electrode.

27. An electrochemical sensor as recited in claim 1, wherein said working electrode comprises a plurality of planar, spaced-apart microbands that are disposed within said solid polymer electrolyte.

28. An electrochemical sensor as recited in claim 27, wherein said counter electrode comprises a plurality of spaced-apart microbands that are disposed within said solid polymer electrolyte, the counter electrode microbands being disposed between said working electrode microbands and defining layers of solid polymer electrolyte therebetween.

29. An electrochemical sensor as recited in claim 28, wherein said layers of solid polymer electrolyte have an average thickness of at least about 25 μ

m and not greater than about 2.5 mm.

30. An electrochemical sensor as recited in claim 29, wherein said polymer electrolyte layers have an average thickness of not greater than about 1 mm.

31. An electrochemical sensor as recited in claim 28, wherein said electrochemical sensor comprises at least 5 working electrode microbands and at least 4 counter electrode microbands.

32. An electrochemical sensor as recited in claim 1, further comprising a reference electrode that is distinct from said counter electrode.

33. A method for making an electrochemical sensor, comprising the steps of:

(a) mixing at least a polymer, an inorganic salt and a solvent to form a polymer electrolyte mixture;

(b) forming the polymer electrolyte mixture into a layer;

(c) drying said layer of polymer electrolyte mixture to remove solvent therefrom and form a first polymer electrolyte layer having mutually opposed first and second major surfaces;

(d) applying a first working electrode layer to at least a portion of said first major surface; and

(e) applying a first counter electrode layer to at least a portion of said second major surface.

34. A method as recited in claim 33, wherein said step of applying a first counter electrode layer comprises the steps of:

(i) forming a second polymer electrolyte layer having mutually opposed first and second major surfaces;

(ii) applying a counter electrode to said first major surface of said second polymer electrolyte layer; and

(iii) laminating said first major surface of said second polymer electrolyte layer to said second major surface of said first polymer electrolyte layer such that said first counter electrode layer is disposed between said first and second polymer electrolyte layers.

35. A method as recited in claim 34, further comprising the step of:

(e) applying a second working electrode layer to said second major surface of said second polymer electrolyte layer.

36. A method as recited in claim 35, wherein said step of applying a second working electrode comprises the steps of:

(i) forming a third polymer electrolyte layer having mutually opposed first and second major surfaces;

(ii) applying a second working electrode layer to said first major surface of said third polymer electrolyte layer; and

(iii) laminating said first major surface of said third polymer electrolyte layer to said second major surface of said second polymer electrolyte layer such that said second working electrode layer is disposed between said second polymer electrolyte layer and said third polymer electrolyte layer.

37. A method as recited in claim 34, wherein said laminating step comprises heating to a temperature of not greater than about 70°

C.

38. A method as recited in claim 33, wherein said polymer electrolyte mixture comprises at least about 10 wt. % and not greater than about 30 wt. % of said polymer, at least about 1 wt. % and not greater than about 10 wt. % of said inorganic salt, and at least about 60 wt. % and not greater than about 80 wt. % of said solvent.

39. A method as recited in claim 33, wherein:

(a) said polymer is selected from the group consisting of poly(oxides), poly(vinyl ethers), polyvinylpyrrolidone, poly(acrylics), poly(methacrylics) and polyvinyl alcohol; and

(b) said inorganic salt is selected from the group consisting of a lithium salt, a sodium salt, an ammonium salt and a magnesium salt.

40. A method as recited in claim 39, wherein said polymer comprises poly(ethylene oxide).

41. A method as recited in claim 39, wherein said inorganic salt comprise a lithium salt.

42. A method as recited in claim 33, wherein said solvent comprises at least one of water, an alcohol or toluene.

43. A method as recited in claim 33, wherein said polymer electrolyte mixture further comprises inorganic particulates having an average particle size of not greater than about 1 μ

m.

44. A method as recited in claim 33, wherein said polymer electrolyte mixture comprises a precursor to an inorganic particulate.

45. A method as recited in claim 33, wherein said step of applying a first working electrode comprises applying a particulate material selected from the group consisting of platinum, gold, silver, palladium, ruthenium, iridium, carbon and mixtures thereof.

46. A method as recited in claim 45, wherein said step of applying a first working electrode comprises applying a thick-film paste comprising said particulate material.

47. A method as recited in claim 46, wherein said thick-film paste further comprises a polymer electrolyte.

48. A method as recited in claim 46, wherein said thick-film paste further comprises from about 0.1 wt. % to about 2 wt. % of a polymer electrolyte.

49. A method for the detection of a contaminant gas species in a gaseous environment, comprising the steps of contacting the gaseous environment with a working electrode to oxidize said contaminant gas species and detecting a current generated by said contacting step between the working electrode and a counter electrode, wherein a solid polymer electrolyte is disposed between the working electrode and the counter electrode to conduct ionic species from the working electrode to the counter electrode.

50. A method as recited in claim 49, wherein said contaminant gas species is H₂S.

51. A method as recited in claim 49, wherein said contaminant gas species is CO.

52. A method as recited in claim 49, wherein said contaminant gas species is ethanol.