Low cost room temperature electrochemical carbon monoxide and toxic gas sensor with humidity compensation based on protonic conductive membranes

Abstract

A low cost room temperature electrochemical gas sensor with humidity compensation for sensing CO, alcohol vapors and other toxic analyte gases has a solid protonic conductive membrane with a low bulk ionic resistance. A sensing electrode and a counter electrode, optionally a counter electrode and a reference electrode, which are separated by the membrane, can be made of mixed protonic-electronic conductors, or can be made of a thin electrically conducting film such as platinum. A reservoir of water maintain the solid protonic conductive membrane at constant 100 percent relative humidity to compensate for ambient humidity changes. Embodiments of the inventive sensor also include an electrochemical analyte gas pump to transport the analyte gas away from the counter electrode side of the sensor. Analyte gas pumps for the inventive sensor include dual pumping electrodes situated on opposite sides of the membrane, and include a means for applying a DC power across the membrane to the sensing and counter electrodes. Another embodiment of the inventive sensor has first and second solid protonic conductive membranes, one of which has a sensing electrode and a counter electrode separated by the first membrane, and the other of which has dual pump electrodes situated on opposite sides of the second membrane.

What is claimed and desired to be secured by United States Letters Patent is: 
     
       1. An electrochemical gas sensor for quantitative measurement of a gas in a ambient atmosphere comprising:
 a sensing electrode permeable to water vapor and comprised of an electrical conducting material and having a surface exposed to the ambient atmosphere; 
 a counter electrode permeable to water vapor and comprised of an electrical conducting material; 
 a first protonic conductive electrolyte membrane permeable to water vapor and situated between and in contact with the sensing and counter electrodes, the sensing electrode reacting with the gas to produce a change in electrical characteristic between the sensing electrode and the counter electrode; 
 means for electrical measurement electrically connected to said sensing and counter electrodes; 
 means, containing a volume of water vapor, for exposing a surface of said counter electrode to said water vapor, wherein the electrical conducting material of at least one of said sensing and counter electrodes is a proton-electron mixed conductive material having 10-50 wt % of a proton conductor material and 50-90 wt % of a first and a second electrical conductor material; whereby, in a positive ambient atmosphere concentration of said gas, said electrical measurement means detects changes in said electrical characteristic. 
 
     
     
       2. The electrochemical gas sensor as defined in  claim 1 , wherein said water vapor containing means contains a volume of water and an antifreeze additive. 
     
     
       3. The electrochemical gas sensor as defined in  claim 1 , wherein the surface of said sensing electrode that is exposed to the ambient atmosphere has a surface area that is smaller than the surface area of the surface of the counter electrode that is exposed to said water vapor, whereby the first protonic conductive electrolyte membrane is exposed to substantially 100 percent relative humidity, and a positive pressure of said water vapor exists from the surface of said counter electrode exposed to said water vapor to the surface of said sensing electrode exposed to the ambient atmosphere. 
     
     
       4. The electrochemical gas sensor as defined in  claim 3 , wherein the surface area of the surface of the counter electrode that is exposed to said water vapor is separated from said means for exposing a surface of said counter electrode to said water vapor by a hydrophobic membrane permeable to water vapor and substantially impervious to water. 
     
     
       5. The electrochemical gas sensor as defined in  claim 1 , wherein the first protonic conductive electrolyte membrane has opposing surfaces, each of said opposing surfaces being in contact with one of the sensing and counter electrodes, wherein at least one of the opposing surfaces of said first protonic conductive electrolyte membrane in contact with one of the sensing and counter electrodes is substantially nonplanar. 
     
     
       6. The electrochemical gas sensor as defined in  claim 1 , wherein at least one of the sensing and counter electrodes is comprised of film having a thickness in the range of about 50 Angstroms to 10,000 Angstroms. 
     
     
       7. The electrochemical gas sensor as defined in  claim 6 , wherein the film is substantially composed of a noble metal. 
     
     
       8. The electrochemical gas sensor as defined in  claim 7 , wherein the noble metal is platinum. 
     
     
       9. The electrochemical gas sensor as defined in  claim 1 , wherein the first protonic conductive electrolyte membrane is substantially composed of a solid, perfluorinated, ion-exchange polymer. 
     
     
       10. The electrochemical gas sensor as defined in  claim 1 , wherein the first protonic conductive electrolyte membrane is a hydrated metal oxide protonic conductor electrolyte membrane. 
     
     
       11. The electrochemical gas sensor as defined in  claim 1 , wherein the proton conductor material for said at least one of the sensing and counter electrodes is a copolymer having a tetrafluoroethylene backbone with a side chain of perfluorinated monomers containing at least one of a sulfonic acid group or a carboxylic acid group. 
     
     
       12. The electrochemical gas sensor as defined in  claim 1 , wherein one of the first and second electrical conductor materials for said at least one of the sensing and counter electrodes is about 50-99 wt % of carbon black, and the other of the first and second electrical conductor materials for said at least one of the sensing and counter electrodes is about 1-50 wt % of platinum. 
     
     
       13. The electrochemical gas sensor as defined in  claim 1 , wherein one of the first and second electrical conductor materials for said at least one of the sensing and counter electrodes is about 50-99 wt % of carbon black, and the other of the first and second electrical conductor materials for said at least one of the sensing and counter electrodes is about 1-50 wt % of Ru oxide. 
     
     
       14. The electrochemical gas sensor as defined in  claim 1 , wherein the electrochemical gas sensor further comprises:
 first and second pump electrodes comprised of an electrical conducting material permeable to water vapor, separate from said sensing and counter electrodes, and situated on opposite sides of and in contact with said first protonic conductive electrolyte membrane, said second pump electrode being situated on the same side of said first protonic conductive membrane as the counter electrode and having a surface thereon exposed to the water vapor in said means for exposing a surface of said counter electrode to said water vapor; and 
 means for applying a DC power across the first protonic conductive electrolyte membrane, said first and second pump electrodes having in electrical connection therebetween said means for applying DC power across the first protonic conductive electrolyte membrane; 
 whereby the gas is transported away from the counter electrode when the DC power means applies a DC power to the first and second pump electrodes. 
 
     
     
       15. The electrochemical gas sensor of  claim 14 , wherein the electrical conducting material of the first and second pump electrodes is substantially composed of carbon. 
     
     
       16. The electrochemical gas sensor as defined in  claim 14 , wherein the electrical conducting material of the first and second pump electrodes is substantially composed of noble metals. 
     
     
       17. The electrochemical gas sensor as defined in  claim 14 , wherein the electrical conducting material of the first and second pump electrodes is substantially composed of conductive hydrated metal oxides. 
     
     
       18. The electrochemical gas sensor as defined in  claim 14 , wherein at least one of the first and second pump electrodes is comprised of a film having a thickness in the range of about 50 Angstroms to 10,000 Angstroms. 
     
     
       19. The electrochemical gas sensor as defined in  claim 14 , wherein the electrical conducting material of said first and second pump electrodes is a proton-electron mixed conductive material having 10-50 wt % of a proton conductor material and 50-90 wt % of a first and a second electrical conductor material. 
     
     
       20. The electrochemical gas sensor as defined in  claim 19 , wherein the proton conductor material for both the first and second pump electrodes is a copolymer having a tetrafluoroethylene backbone with a side chain of perfluorinated monomers containing at least one of a sulfonic acid group or a carboxylic acid group. 
     
     
       21. The electrochemical gas sensor as defined in  claim 19 , wherein one of the first and second electrical conductor materials for the first pump electrode is about 50-99 wt % of carbon black, and the other of the first and second electrical conductor materials for the first pump electrode is 1 to 50 wt % of platinum. 
     
     
       22. The electrochemical gas sensor as defined in  claim 19 , wherein one of the first and second electrical conductor materials for the second pump electrode is about 50-99 wt % of carbon black, and the other of the first and second electrical conductor materials for the second pump electrode is 1 to 50 wt % of Ru oxide. 
     
     
       23. The electrochemical gas sensor as defined in  claim 1 , wherein the electrochemical gas sensor further comprises:
 a second protonic conductive electrolyte membrane permeable to water vapor; 
 first and second pump electrodes permeable to water vapor and comprised of an electron conductive material, and being separate from said sensing and counter electrodes and situated on opposite sides of and in contact with said second protonic conductive electrolyte membrane, said means for exposing a surface of said counter electrode to said water vapor exposing a surface of said second pump electrode to said water vapor, and said first pump electrode having a surface exposed to the ambient atmosphere; and 
 means for applying a DC power across said second protonic electrolyte membrane, said first and second pump electrodes having in electrical connection therebetween said means for applying DC power across said second protonic electrolyte membrane; 
 whereby the gas is transported away from the counter electrode when the DC power means applies a DC power to the first and second pump electrodes. 
 
     
     
       24. The electrochemical gas sensor as defined in  claim 23 , wherein the second protonic conductive electrolyte membrane is substantially composed of a solid, perfluorinated, ion-exchange polymer. 
     
     
       25. The electrochemical gas sensor as defined in  claim 23 , wherein the second protonic conductive electrolyte membrane is a hydrated metal oxide protonic conductor electrolyte membrane. 
     
     
       26. The electrochemical gas sensor as defined in  claim 23 , wherein the surface area of the surface of said first pump electrode that is exposed to the ambient atmosphere is smaller than the surface area of the surface of the second pump electrode that is exposed to said water vapor, whereby the second protonic conductive electrolyte membrane is exposed to substantially 100 percent relative humidity, and a positive pressure of said water vapor exists from the surface of said second pump electrode that is exposed to said water vapor to the surface of said first pump electrode that is exposed to the ambient atmosphere. 
     
     
       27. The electrochemical gas sensor as defined in  claim 26 , wherein the surface area of the surface of the second pump electrode that is exposed to said water vapor is separated from said means for exposing a surface of said counter electrode to said water vapor by a hydrophobic membrane permeable to water vapor and substantially impervious to water. 
     
     
       28. The electrochemical gas sensor as defined in  claim 1 , further comprising:
 means for applying a DC pulse power source across the first protonic conductive membrane, said sensing and counter electrodes having in electrical connection therebetween said means for applying DC pulse power across the first protonic conductive membrane; and 
 switch means for alternating the connection between the sensing and counter electrodes from the electrical measurement means to the DC pulse power means; 
 whereby, in a positive ambient atmosphere concentration of said gas, said electrical measurement means detects changes in said electrical characteristic when said switch means connects said electrical measurement means to the sensing and counter electrodes; and 
 whereby said DC pulse power means moves the gas away from a side of the gas sensor where the counter electrode is placed when said switch means connects said DC pulse power means to the sensing and counter electrodes. 
 
     
     
       29. The electrochemical gas sensor as defined in  claim 1 , wherein the gas is CO. 
     
     
       30. The electrochemical gas sensor as defined in  claim 1 , wherein the gas is NO x . 
     
     
       31. The electrochemical gas sensor as defined in  claim 1 , wherein the gas is hydrogen. 
     
     
       32. The electrochemical gas sensor as defined in  claim 1 , wherein the gas is H 2 S. 
     
     
       33. The electrochemical gas sensor as defined in  claim 1 , wherein the gas is H 2 O vapor. 
     
     
       34. The electrochemical gas sensor as defined in  claim 1 , wherein the gas is alcohol vapor. 
     
     
       35. An electrochemical gas sensor for quantitative measurement of a gas in an ambient atmosphere comprising:
 a sensing electrode permeable to water vapor and comprised of an electrical conducting material and having a surface exposed to the ambient atmosphere; 
 a counter electrode permeable to water vapor and comprised of an electrical conducting material; 
 a first protonic conductive electrolyte membrane permeable to water vapor and situated in between and in contact with the sensing and counter electrodes, the sensing electrode reacting with the gas to produce a change in electrical characteristic between the sensing electrode and the counter electrode; 
 a second protonic conductive electrolyte membrane permeable to water vapor; 
 first and second pump electrodes permeable to water vapor and comprised of an electrical conductive material, and being separate from said sensing and counter electrodes and situated on opposite sides of and in contact with said second protonic conductive electrolyte membrane; 
 means, containing a volume of water vapor, for exposing a surface of said second pump electrode to said water vapor, and said first pump electrode having a surface exposed to the ambient atmosphere, said second pump electrode being separated from said counter electrode by said means for exposing a surface of said second pump electrode to said water vapor, and said counter electrode having a surface exposed to said water vapor by said means for exposing a surface of said second pump electrode to said water vapor; 
 means for electrical measurement in electrical communication with said sensing electrode and said counter electrode; and 
 means for applying a DC power across said second protonic electrolyte membrane in electrical contact with said first and second pump electrodes; 
 whereby the gas is transported away from the counter electrode when the DC power means applies a DC power across said second protonic electrolyte membrane; and 
 whereby, in a positive ambient concentration of said gas, said electrical measurement means detects changes in said electrical characteristic. 
 
     
     
       36. The electrochemical gas sensor as defined in  claim 35 , wherein at least one of said first and second protonic conductive electrolyte membranes is substantially comprised of a solid, perfluorinated, ion-exchange polymer. 
     
     
       37. The electrochemical gas sensor as defined in  claim 35 , wherein at least one of the first and second protonic conductive electrolyte membranes is a hydrated metal oxide protonic conductor electrolyte membrane. 
     
     
       38. The electrochemical gas sensor as defined in  claim 35 , wherein the surface of said first pump electrode that is exposed to the ambient atmosphere has a surface area smaller than the surface area of the surface of the second pump electrode that is exposed to said water vapor, and wherein the surface of said sensing electrode that is exposed to the ambient atmosphere has a surface area smaller than the surface area of the surface of the counter electrode that is exposed to said water vapor, whereby the first protonic conductive electrolyte membrane is exposed to substantially 100 percent relative humidity, a positive pressure of said water vapor exists from the surface of said counter electrode that is exposed to said water vapor to the surface of said sensing electrode that is exposed to the ambient atmosphere, the second protonic conductive electrolyte membrane is exposed to substantially 100 percent relative humidity, and a positive pressure of said water vapor exists from the surface of said second pump electrode that is exposed to said water vapor to the surface of said first pump electrode that is exposed to the ambient atmosphere. 
     
     
       39. The electrochemical gas sensor as defined in  claim 38 , wherein the surface area of each of the surfaces of the second pump and counter electrodes that are exposed to said water vapor by said means for exposing a surface of said second pump electrode to said water vapor are each separated from said means for exposing a surface of said second pump electrode to said water vapor by a hydrophobic membrane permeable to water vapor and substantially impervious to water. 
     
     
       40. The electrochemical gas sensor as defined in  claim 35 , wherein said means for exposing a surface of said second pump electrode to said water vapor further contains an antifreeze additive. 
     
     
       41. The electrochemical gas sensor as defined in  claim 35 , wherein at least one of the surfaces of said first protonic conductive electrolyte membrane in contact with one of the sensing and counter electrodes is substantially nonplanar, and wherein at least one of the surfaces of said second protonic conductive electrolyte membrane in contact with one of the first and second pump electrodes is substantially nonplanar. 
     
     
       42. The electrochemical gas sensor as defined in  claim 35 , wherein at least one of the sensing, counter, first pump, and second pump electrodes is comprised of film having a thickness in the range of about 50 Angstroms to 10,000 Angstroms. 
     
     
       43. The electrochemical gas sensor as defined in  claim 42 , wherein the film is substantially composed of a noble metal. 
     
     
       44. The electrochemical gas sensor as defined in  claim 43 , wherein the noble metal is platinum. 
     
     
       45. The electrochemical gas sensor as defined in  claim 35 , wherein the at least one of the sensing, counter, first pump, and second pump electrodes is substantially comprised of proton conductive material. 
     
     
       46. The electrochemical gas sensor as defined in  claim 35 , wherein at least one of the first and second protonic conductive electrolyte membranes is substantially comprised of a solid, perfluorinated, ion-exchange polymer. 
     
     
       47. The electrochemical gas sensor as defined in  claim 35 , wherein at least one of the first and second protonic conductive electrolyte membranes is a hydrated metal oxide protonic conductive electrolyte membrane. 
     
     
       48. The electrochemical gas sensor as defined in  claim 35 , wherein the electrical conducting material of at least one of said sensing, counter, first pump, and second pump electrodes is a proton-electron mixed conductive material having 10-50 wt % of a proton conductor material and 50-90 wt % of a first and a second electrical conductor material. 
     
     
       49. The electrochemical gas sensor as defined in  claim 48 , wherein the proton conductor material for said at least one of the sensing, counter, first pump, and second pump electrodes is a copolymer having a tetrafluoroethylene backbone with a side chain of perfluorinated monomers containing at least one of a sulfonic acid group or a carboxylic acid group. 
     
     
       50. The electrochemical gas sensor as defined in  claim 48 , wherein one of the first and second electrical conductor materials for said at least one of the sensing, counter, first pump, and second pump electrodes is about 50-99 wt % of carbon black, and the other of the first and second electrical conductor materials for said at least one of the sensing, counter, first pump and second pump electrodes is about 1-50 wt % of platinum. 
     
     
       51. The electrochemical gas sensor as defined in  claim 48 , wherein one of the first and second electrical conductor materials for said at least one of the sensing, counter, first pump, and second pump electrodes is about 50-99 wt % of carbon black, and the other of the first and second electrical conductor materials for said at least one of the sensing, counter, first pump, and second pump electrodes is about 1-50 wt % of Ru oxide. 
     
     
       52. An electrochemical gas sensor for quantitative measurement of a gas in an ambient atmosphere comprising:
 a sensing electrode permeable to water vapor and comprised of an electrical conducting material and being exposed to the ambient atmosphere; 
 a reference electrode permeable to water vapor and comprised of an electrical conducting material; 
 a counter electrode permeable to water vapor and comprised of an electrical conducting material and being separate from both said sensing and reference electrodes, and being exposed to the ambient atmosphere; 
 a protonic conductive electrolyte membrane permeable to water vapor, having top and bottom sides, said bottom side of said protonic conductive membrane being in contact with the counter electrode, and the top side of said protonic conductive membrane being in contact with the sensing and reference electrodes; 
 means, containing a volume of water vapor, for exposing a surface of said counter electrode to said water vapor, the sensing electrode reacting with the gas to produce a change in electrical characteristic between the sensing electrode and the counter electrode; and 
 means for electrical measurement in electrical contact between the sensing electrode and the counter electrode, wherein the electrical conducting material of at least one of said sensing, counter, and reference electrodes is a proton-electron mixed conductive material having 10-50 wt % of a proton conductor material and 50-90 wt % of a first and a second electrical conductor material; 
 whereby, in a positive ambient concentration of said gas, said electrical measurement means detects changes in said electrical characteristic. 
 
     
     
       53. The electrochemical gas sensor as defined in  claim 52 , further comprising:
 means for applying a DC power across said protonic electrolyte membrane in electrical contact between the sensing electrode and said counter electrode, whereby the gas is transported away from the counter electrode when the DC power means applies a DC power across said protonic electrolyte membrane. 
 
     
     
       54. The electrochemical gas sensor as defined in  claim 52 , wherein said means for exposing a surface of said counter electrode to said water vapor further contains an antifreeze additive. 
     
     
       55. The electrochemical gas sensor as defined in  claim 52 , wherein the surface of said sensing electrode that is exposed to the ambient atmosphere has a surface area smaller than the surface area of the surface of the counter electrode that is exposed to said water vapor, whereby the first protonic conductive electrolyte membrane is exposed to substantially 100 percent relative humidity, and a positive pressure of said water vapor exists from the surface of said counter electrode that is exposed to said water vapor to the surface of said sensing electrode that is exposed to the ambient atmosphere. 
     
     
       56. The electrochemical gas sensor as defined in  claim 55 , wherein the surface area of the surface of the counter electrode that is exposed to said water vapor is separated from said means for exposing a surface of said counter electrode to said water vapor by a hydrophobic membrane permeable to water vapor and substantially impervious to water. 
     
     
       57. The electrochemical gas sensor as defined in  claim 52 , wherein at least one of the surfaces of said protonic conductive electrolyte membrane in contact with one of the sensing, counter, and reference electrodes is substantially nonplanar. 
     
     
       58. The electrochemical gas sensor as defined in  claim 52 , wherein at least one of the sensing, counter, and reference electrodes is comprised of film having a thickness in the range of about 50 Angstroms to 10,000 Angstroms. 
     
     
       59. The electrochemical gas sensor as defined in  claim 58 , wherein the film is substantially composed of a noble metal. 
     
     
       60. The electrochemical gas sensor as defined in  claim 59 , wherein the noble metal is platinum. 
     
     
       61. The electrochemical gas sensor as defined in  claim 52 , wherein the protonic conductive electrolyte membrane is substantially comprised of a solid, perfluorinated, ion-exchange polymer. 
     
     
       62. The electrochemical gas sensor as defined in  claim 52 , wherein the protonic conductive electrolyte membrane is a hydrated metal oxide protonic conductor electrolyte membrane. 
     
     
       63. The electrochemical gas sensor as defined in  claim 52 , wherein the proton conductor material for said at least one of the sensing, counter, and reference electrodes is a copolymer having a tetrafluoroethylene backbone with a side chain of perfluorinated monomers containing at least one of a sulfonic acid group or a carboxylic acid group. 
     
     
       64. The electrochemical gas sensor as defined in  claim 52 , wherein one of the first and second electrical conductor materials for said at least one of the sensing, counter, and reference electrodes is about 50-99 wt % of carbon black, and the other of the first and second electrical conductor materials for said at least one of the sensing, counter, and reference electrodes is about 1-50 wt % of platinum. 
     
     
       65. The electrochemical gas sensor as defined in  claim 52 , wherein one of the first and second electrical conductor materials for said at least one of the sensing, counter, and reference electrodes is about 50-99 wt % of carbon black, and the other of the first and second electrical conductor materials for said at least one of the sensing, counter, and reference electrodes is about 1-50 wt % of Ru oxide. 
     
     
       66. A two-electrode electrochemical gas sensor for quantitative measurement of a gas in an ambient atmosphere comprising:
 a sensing electrode permeable to water vapor and comprised of an electrical conducting material and having a surface exposed to the ambient atmosphere;   a counter electrode permeable to water vapor and comprised of an electrical conducting material;   a first protonic conductive electrolyte membrane permeable to water vapor and situated between and in contact with the sensing and counter electrodes, the sensing electrode and the counter electrode being the only two electrodes in contact with the first protonic conductive electrolyte membrane and the sensing electrode reacting with the gas to produce a change in electrical characteristic between the sensing electrode and the counter electrode;   means for electrical measurement electrically connected to said sensing and counter electrodes;   means, containing a volume of water vapor, for exposing a surface of said counter electrode to said water vapor,   wherein the electrical conducting material of at least one of said sensing and counter electrodes is a proton-electron mixed conductive material having 10-50 wt % of a proton conductor material and 50-90 wt % of a first and a second electrical conductor material;   whereby, in a positive ambient atmosphere concentration of said gas, said electrical measurement means detects changes in said electrical characteristic.   
     
     
       67. An electrochemical gas sensor for quantitative measurement of a gas in an ambient atmosphere comprising:
 a sensing electrode permeable to water vapor and comprised of an electrical conducting material and having a surface exposed to the ambient atmosphere;   a counter electrode permeable to water vapor and comprised of an electrical conducting material;   a first protonic conductive electrolyte membrane permeable to water vapor and situated between and in contact with the sensing and counter electrodes, the sensing electrode reacting with the gas to produce a change in electrical characteristic between the sensing electrode and the counter electrode in the absence of an applied voltage to the sensing electrode;   means for electrical measurement electrically connected to said sensing and counter electrodes;   means, containing a volume of water vapor, for exposing a surface of said counter electrode to said water vapor,   wherein the electrical conducting material of at least one of said sensing and counter electrodes is a proton-electron mixed conductive material having 10-50 wt % of a proton conductor material and 50-90 wt % of a first and a second electrical conductor material;   whereby, in a positive ambient atmosphere concentration of said gas, said electrical measurement means detects changes in said electrical characteristic.   
     
     
       68. A non-biased electrochemical gas sensor for quantitative measurement of a gas in an ambient atmosphere comprising:
 a sensing electrode permeable to water vapor and comprised of an electrical conducting material and having a surface exposed to the ambient atmosphere;   a counter electrode permeable to water vapor and comprised of an electrical conducting material;   a first protonic conductive electrolyte membrane permeable to water vapor and situated between and in contact with the sensing and counter electrodes, the sensing electrode reacting with the gas to produce a change in electrical characteristic between the sensing electrode and the counter electrode;   means for electrical measurement electrically connected to said sensing and counter electrodes;   means, containing a volume of water vapor, for exposing a surface of said counter electrode to said water vapor,   wherein the electrical conducting material of at least one of said sensing and counter electrodes is a proton-electron mixed conductive material having 10-50 wt % of a proton conductor material and 50-90 wt % of a first and a second electrical conductor material;   whereby, in a positive ambient atmosphere concentration of said gas, said electrical measurement means detects changes in said electrical characteristic in the absence of any biasing voltage.   
     
     
       69. The non-biased electrochemical gas sensor of claim 68 in which the sensing electrode and the counter electrode are the only two electrodes in contact with the first protonic conductive electrolyte membrane. 
     
     
       70. A two-electrode electrochemical gas sensor for quantitative measurement of a gas in an ambient atmosphere comprising:
 a sensing electrode permeable to water vapor and comprised of an electrical conducting material and having a surface exposed to the ambient atmosphere;   a counter electrode permeable to water vapor and comprised of an electrical conducting material;   a first protonic conductive electrolyte membrane permeable to water vapor and situated between and in contact with the sensing and counter electrodes, the sensing electrode and the counter electrode being the only two electrodes in contact with the first protonic conductive electrolyte membrane, and the sensing electrode reacting with the gas to produce a change in electrical characteristic between the sensing electrode and the counter electrode in the absence of an applied voltage to the sensing electrode;   means for electrical measurement electrically connected to said sensing and counter electrodes;   means, containing a volume of water vapor, for exposing a surface of said counter electrode to said water vapor,   wherein the electrical conducting material of at least one of said sensing and counter electrodes is a proton-electron mixed conductive material having 10-50 wt % of a proton conductor material and 50-90 wt % of a first and a second electrical conductor material;   whereby, in a positive ambient atmosphere concentration of said gas, said electrical measurement means detects changes in said electrical characteristic.   
     
     
       71. An electrochemical gas sensor for quantitative measurement of a gas in an ambient atmosphere comprising:
 a sensing electrode permeable to water vapor and comprised of an electrical conducting material and having a surface exposed to the ambient atmosphere;   a counter electrode permeable to water vapor and comprised of an electrical conducting material;   a first protonic conductive electrolyte membrane permeable to water vapor and situated between and in contact with the sensing and counter electrodes, the sensing electrode reacting with the gas to produce a change in electrical characteristic between the sensing electrode and the counter electrode, the sensing electrode and the counter electrode being on opposite sides of the first protonic conductive electrolyte membrane;   means for electrical measurement electrically connected to said sensing and counter electrodes;   means, containing a volume of water vapor, for exposing a surface of said counter electrode to said water vapor,   wherein the electrical conducting material of at least one of said sensing and counter electrodes is a proton-electron mixed conductive material having 10-50 wt % of a proton conductor material and 50-90 wt % of a first and a second electrical conductor material;   whereby, in a positive ambient atmosphere concentration of said gas, said electrical measurement means detects changes in said electrical characteristic.   
     
     
       72. The electrochemical gas sensor of claim 71 in which the sensing electrode and the counter electrode are the only two electrodes in contact with the first protonic conductive electrolyte membrane. 
     
     
       73. The electrochemical gas sensor of claim 72 in which the sensing electrode reacts with the gas to produce a change in electrical characteristic between the sensing electrode and the counter electrode in the absence of an applied voltage to the sensing electrode. 
     
     
       74. The electrochemical gas sensor of claim 71 in which the sensing electrode reacts with the gas to produce a change in electrical characteristic between the sensing electrode and the counter electrode in the absence of an applied voltage to the sensing electrode. 
     
     
       75. An electrochemical gas sensor for quantitative measurement of a gas in an ambient atmosphere at room temperature comprising:
 a sensing electrode permeable to water vapor and comprised of an electrical conducting material and having a surface exposed to the ambient atmosphere;   a counter electrode permeable to water vapor and comprised of an electrical conducting material;   a first protonic conductive electrolyte membrane permeable to water vapor and situated between and in contact with the sensing and counter electrodes, the sensing electrode reacting with the gas to produce a change in electrical characteristic between the sensing electrode and the counter electrode;   means for electrical measurement electrically connected to said sensing and counter electrodes, said means for electrical measurement being capable of detecting changes in said electrical characteristic in a positive ambient atmosphere concentration of said gas;   means, containing a volume of water vapor, for exposing a surface of said counter electrode to said water vapor,   wherein the electrical conducting material of at least one of said sensing and counter electrodes is a proton-electron mixed conductive material having 10-50 wt % of a proton conductor material and 50-90 wt % of a first and a second electrical conductor material.   
     
     
       76. The electrochemical gas sensor as defined in claim 75, wherein said water vapor containing means contains a volume of water and an antifreeze additive. 
     
     
       77. The electrochemical gas sensor as defined in claim 75, wherein the surface of said sensing electrode that is exposed to the ambient atmosphere has a surface area that is smaller than the surface area of the surface of the counter electrode that is exposed to said water vapor, whereby the first protonic conductive electrolyte membrane is exposed to substantially 100 percent relative humidity, and a positive pressure of said water vapor exists from the surface of said counter electrode exposed to said water vapor to the surface of said sensing electrode exposed to the ambient atmosphere. 
     
     
       78. The electrochemical gas sensor as defined in claim 77, wherein the surface area of the surface of the counter electrode that is exposed to said water vapor is separated from said means for exposing a surface of said counter electrode to said water vapor by a hydrophobic membrane permeable to water vapor and substantially impervious to water. 
     
     
       79. The electrochemical gas sensor as defined in claim 75, wherein the first protonic conductive electrolyte membrane has opposing surfaces, each of said opposing surfaces being in contact with one of the sensing and counter electrodes, wherein at least one of the opposing surfaces of said first protonic conductive electrolyte membrane in contact with one of the sensing and counter electrodes is substantially nonplanar. 
     
     
       80. The electrochemical gas sensor as defined in claim 75, wherein at least one of the sensing and counter electrodes is comprised of film having a thickness in the range of about 50 Angstroms to 10,000 Angstroms. 
     
     
       81. The electrochemical gas sensor as defined in claim 80, wherein the film is substantially composed of a noble metal. 
     
     
       82. The electrochemical gas sensor as defined in claim 81, wherein the noble metal is platinum. 
     
     
       83. The electrochemical gas sensor as defined in claim 75, wherein the first protonic conductive electrolyte membrane is substantially composed of a solid, perfluorinated, ion-exchange polymer. 
     
     
       84. The electrochemical gas sensor as defined in claim 75, wherein the first protonic conductive electrolyte membrane is a hydrated metal oxide protonic conductor electrolyte membrane. 
     
     
       85. The electrochemical gas sensor as defined in claim 75, wherein the proton conductor material for said at least one of the sensing and counter electrodes is a copolymer having a tetrafluoroethylene backbone with a side chain of perfluorinated monomers containing at least one of a sulfonic acid group or a carboxylic acid group. 
     
     
       86. The electrochemical gas sensor as defined in claim 75, wherein one of the first and second electrical conductor materials for said at least one of the sensing and counter electrodes is about 50-99 wt % of carbon black, and the other of the first and second electrical conductor materials for said at least one of the sensing and counter electrodes is about 1-50 wt % of platinum. 
     
     
       87. The electrochemical gas sensor as defined in claim 75, wherein one of the first and second electrical conductor materials for said at least one of the sensing and counter electrodes is about 50-99 wt % of carbon black, and the other of the first and second electrical conductor materials for said at least one of the sensing and counter electrodes is about 1-50 wt % of Ru oxide. 
     
     
       88. The electrochemical gas sensor as defined in claim 75, wherein the electrochemical gas sensor further comprises:
 first and second pump electrodes comprised of an electrical conducting material permeable to water vapor, separate from said sensing and counter electrodes, and situated on opposite sides of and in contact with said first protonic conductive electrolyte membrane, said second pump electrode being situated on the same side of said first protonic conductive membrane as the counter electrode and having a surface thereon exposed to the water vapor in said means for exposing a surface of said counter electrode to said water vapor; and means for applying a DC power across the first protonic conductive electrolyte membrane, said first and second pump electrodes having in electrical connection therebetween said means for applying DC power across the first protonic conductive electrolyte membrane;   whereby the gas is transported away from the counter electrode when the DC power means applies a DC power to the first and second pump electrodes.   
     
     
       89. The electrochemical gas sensor of claim 88, wherein the electrical conducting material of the first and second pump electrodes is substantially composed of carbon. 
     
     
       90. The electrochemical gas sensor as defined in claim 88, wherein the electrical conducting material of the first and second pump electrodes is substantially composed of noble metals. 
     
     
       91. The electrochemical gas sensor as defined in claim 88, wherein the electrical conducting material of the first and second pump electrodes is substantially composed of conductive hydrated metal oxides. 
     
     
       92. The electrochemical gas sensor as defined in claim 88, wherein at least one of the first and second pump electrodes is comprised of a film having a thickness in the range of about 50 Angstroms to 10,000 Angstroms. 
     
     
       93. The electrochemical gas sensor as defined in claim 88, wherein the electrical conducting material of said first and second pump electrodes is a proton-electron mixed conductive material having 10-50 wt % of a proton conductor material and 50-90 wt % of a first and a second electrical conductor material. 
     
     
       94. The electrochemical gas sensor as defined in claim 93, wherein the proton conductor material for both the first and second pump electrodes is a copolymer having a tetrafluoroethylene backbone with a side chain of perfluorinated monomers containing at least one of a sulfonic acid group or a carboxylic acid group. 
     
     
       95. The electrochemical gas sensor as defined in claim 93, wherein one of the first and second electrical conductor materials for the first pump electrode is about 50-99 wt % of carbon black, and the other of the first and second electrical conductor materials for the first pump electrode is 1 to 50 wt % of platinum. 
     
     
       96. The electrochemical gas sensor as defined in claim 93, wherein one of the first and second electrical conductor materials for the second pump electrode is about 50-99 wt % of carbon black, and the other of the first and second electrical conductor materials for the second pump electrode is 1 to 50 wt % of Ru oxide. 
     
     
       97. The electrochemical gas sensor as defined in claim 75, wherein the electrochemical gas sensor further comprises:
 a second protonic conductive electrolyte membrane permeable to water vapor;   first and second pump electrodes permeable to water vapor and comprised of an electron conductive material, and being separate from said sensing and counter electrodes and situated on opposite sides of and in contact with said second protonic conductive electrolyte membrane, said means for exposing a surface of said counter electrode to said water vapor exposing a surface of said second pump electrode to said water vapor, and said first pump electrode having a surface exposed to the ambient atmosphere; and   means for applying a DC power across said second protonic electrolyte membrane, said first and second pump electrodes having in electrical connection therebetween said means for applying DC power across said second protonic electrolyte membrane;   whereby the gas is transported away from the counter electrode when the DC power means applies a DC power to the first and second pump electrodes.   
     
     
       98. The electrochemical gas sensor as defined in claim 97, wherein the second protonic conductive electrolyte membrane is substantially composed of a solid, perfluorinated, ion-exchange polymer. 
     
     
       99. The electrochemical gas sensor as defined in claim 97, wherein the second protonic conductive electrolyte membrane is a hydrated metal oxide protonic conductor electrolyte membrane. 
     
     
       100. The electrochemical gas sensor as defined in claim 97, wherein the surface area of the surface of said first pump electrode that is exposed to the ambient atmosphere is smaller than the surface area of the surface of the second pump electrode that is exposed to said water vapor, whereby the second protonic conductive electrolyte membrane is exposed to substantially 100 percent relative humidity, and a positive pressure of said water vapor exists from the surface of said second pump electrode that is exposed to said water vapor to the surface of said first pump electrode that is exposed to the ambient atmosphere. 
     
     
       101. The electrochemical gas sensor as defined in claim 100, wherein the surface area of the surface of the second pump electrode that is exposed to said water vapor is separated from said means for exposing a surface of said counter electrode to said water vapor by a hydrophobic membrane permeable to water vapor and substantially impervious to water. 
     
     
       102. The electrochemical gas sensor as defined in claim 75, further comprising:
 means for applying a DC pulse power source across the first protonic conductive membrane, said sensing and counter electrodes having in electrical connection therebetween said means for applying DC pulse power across the first protonic conductive membrane; and   switch means for alternating the connection between the sensing and counter electrodes from the electrical measurement means to the DC pulse power means;   whereby, in a positive ambient atmosphere concentration of said gas, said electrical measurement means detects changes in said electrical characteristic when said switch means connects said electrical measurement means to the sensing and counter electrodes; and   whereby said DC pulse power means moves the gas away from a side of the gas sensor where the counter electrode is placed when said switch means connects said DC pulse power means to the sensing and counter electrodes.   
     
     
       103. The electrochemical gas sensor as defined in claim 75, wherein the gas is CO. 
     
     
       104. The electrochemical gas sensor as defined in claim 75, wherein the gas is NO x . 
     
     
       105. The electrochemical gas sensor as defined in claim 75, wherein the gas is hydrogen. 
     
     
       106. The electrochemical gas sensor as defined in claim 75, wherein the gas is H 2 S. 
     
     
       107. The electrochemical gas sensor as defined in claim 75, wherein the gas is H 2 O vapor. 
     
     
       108. The electrochemical gas sensor as defined in claim 75, wherein the gas is alcohol vapor. 
     
     
       109. An electrochemical gas sensor for quantitative measurement of a gas in an ambient atmosphere at room temperature comprising:
 a sensing electrode permeable to water vapor and comprised of an electrical conducting material and being exposed to the ambient atmosphere;   a reference electrode permeable to water vapor and comprised of an electrical conducting material;   a counter electrode permeable to water vapor and comprised of an electrical conducting material and being separate from both said sensing and reference electrodes, and being exposed to the ambient atmosphere;   a protonic conductive electrolyte membrane permeable to water vapor, having top and bottom sides, said bottom side of said protonic conductive membrane being in contact with the counter electrode, and the top side of said protonic conductive membrane being in contact with the sensing and reference electrodes;   means, containing a volume of water vapor, for exposing a surface of said counter electrode to said water vapor, the sensing electrode reacting with the gas to produce a change in electrical characteristic between the sensing electrode and the counter electrode; and   means for electrical measurement in electrical contact between the sensing electrode and the counter electrode,   wherein the electrical conducting material of at least one of said sensing, counter, and reference electrodes is a proton-electron mixed conductive material having 10-50 wt % of a proton conductor material and 50-90 wt % of a first and a second electrical conductor material;   whereby, in a positive ambient concentration of said gas, said electrical measurement means detects changes in said electrical characteristic.   
     
     
       110. The electrochemical gas sensor as defined in claim 109, further comprising:
 means for applying a DC power across said protonic electrolyte membrane in electrical contact between the sensing electrode and said counter electrode, whereby the gas is transported away from the counter electrode when the DC power means applies a DC power across said protonic electrolyte membrane.   
     
     
       111. The electrochemical gas sensor as defined in claim 109, wherein said means for exposing a surface of said counter electrode to said water vapor further contains an antifreeze additive. 
     
     
       112. The electrochemical gas sensor as defined in claim 109, wherein the surface of said sensing electrode that is exposed to the ambient atmosphere has a surface area smaller than the surface area of the surface of the counter electrode that is exposed to said water vapor, whereby the first protonic conductive electrolyte membrane is exposed to substantially 100 percent relative humidity, and a positive pressure of said water vapor exists from the surface of said counter electrode that is exposed to said water vapor to the surface of said sensing electrode that is exposed to the ambient atmosphere. 
     
     
       113. The electrochemical gas sensor as defined in claim 112, wherein the surface area of the surface of the counter electrode that is exposed to said water vapor is separated from said means for exposing a surface of said counter electrode to said water vapor by a hydrophobic membrane permeable to water vapor and substantially impervious to water. 
     
     
       114. The electrochemical gas sensor as defined in claim 109, wherein at least one of the surfaces of said protonic conductive electrolyte membrane in contact with one of the sensing, counter, and reference electrodes is substantially nonplanar. 
     
     
       115. The electrochemical gas sensor as defined in claim 109, wherein at least one of the sensing, counter, and reference electrodes is comprised of film having a thickness in the range of about 50 Angstroms to 10,000 Angstroms. 
     
     
       116. The electrochemical gas sensor as defined in claim 115, wherein the film is substantially composed of a noble metal. 
     
     
       117. The electrochemical gas sensor as defined in claim 116, wherein the noble metal is platinum. 
     
     
       118. The electrochemical gas sensor as defined in claim 109, wherein the protonic conductive electrolyte membrane is substantially comprised of a solid, perfluorinated, ion-exchange polymer. 
     
     
       119. The electrochemical gas sensor as defined in claim 109, wherein the protonic conductive electrolyte membrane is a hydrated metal oxide protonic conductor electrolyte membrane. 
     
     
       120. The electrochemical gas sensor as defined in claim 109, wherein the proton conductor material for said at least one of the sensing, counter, and reference electrodes is a copolymer having a tetrafluoroethylene backbone with a side chain of perfluorinated monomers containing at least one of a sulfonic acid group or a carboxylic acid group. 
     
     
       121. The electrochemical gas sensor as defined in claim 109, wherein one of the first and second electrical conductor materials for said at least one of the sensing, counter, and reference electrodes is about 50-99 wt % of carbon black, and the other of the first and second electrical conductor materials for said at least one of the sensing, counter, and reference electrodes is about 1-50 wt % of platinum. 
     
     
       122. The electrochemical gas sensor as defined in claim 109, wherein one of the first and second electrical conductor materials for said at least one of the sensing, counter, and reference electrodes is about 50-99 wt % of carbon black, and the other of the first and second electrical conductor materials for said at least one of the sensing, counter, and reference electrodes is about 1-50 wt % of Ru oxide. 
     
     
       123. A residential electrochemical gas sensor for quantitative measurement of carbon monoxide gas in an ambient atmosphere comprising:
 a sensing electrode permeable to water vapor and comprised of an electrical conducting material and having a surface exposed to the ambient atmosphere;   a counter electrode permeable to water vapor and comprised of an electrical conducting material;   a first protonic conductive electrolyte membrane permeable to water vapor and situated between and in contact with the sensing and counter electrodes, the sensing electrode reacting with the carbon monoxide gas to produce a change in electrical characteristic between the sensing electrode and the counter electrode;   means for electrical measurement electrically connected to said sensing and counter electrodes;   means, containing a volume of water vapor, for exposing a surface of said counter electrode to said water vapor,   wherein the electrical conducting material of at least one of said sensing and counter electrodes is a proton-electron mixed conductive material having 10-50 wt % of a proton conductor material and 50-90 wt % of a first and a second electrical conductor material;   whereby, in a positive ambient atmosphere concentration of the carbon monoxide gas at room temperature, said electrical measurement means detects changes in said electrical characteristic.   
     
     
       124. The electrochemical gas sensor of claim 123 in which the sensing electrode comprises a mixed protonic-electronic conductive electrode. 
     
     
       125. A two-electrode residential electrochemical gas sensor for quantitative measurement of carbon monoxide gas in an ambient atmosphere comprising:
 a sensing electrode permeable to water vapor and comprised of an electrical conducting material and having a surface exposed to the ambient atmosphere;   a counter electrode permeable to water vapor and comprised of an electrical conducting material;   a first protonic conductive electrolyte membrane permeable to water vapor and situated between and in contact with the sensing and counter electrodes, the sensing electrode and the counter electrode being the only two electrodes in contact with the first protonic conductive electrolyte membrane, and the sensing electrode reacting with the carbon monoxide gas to produce a change in electrical characteristic between the sensing electrode and the counter electrode in the absence of an applied voltage to the sensing electrode;   means for electrical measurement electrically connected to said sensing and counter electrodes;   means, containing a volume of water vapor, for exposing a surface of said counter electrode to said water vapor,   wherein the electrical conducting material of at least one of said sensing and counter electrodes is a proton-electron mixed conductive material having 10-50 wt % of a proton conductor material and 50-90 wt % of a first and a second electrical conductor material;   whereby, in a positive ambient atmosphere concentration of the carbon monoxide gas at room temperature, said electrical measurement means detects changes in said electrical characteristic;   wherein each of the sensing electrode and the counter electrode comprise a mixed protonic-electronic conductive electrode including platinum, carbon and a copolymer having a tetrafluoroethylene backbone with a side chain of perfluorinated monomers containing a sulfonic acid group; and   wherein the protonic conductive solid electrolyte membrane is substantially comprised of a solid, perfluorinated, ion-exchange polymer.   
     
     
       126. The two-electrode electrochemical gas sensor as defined in claim 125, wherein the sensing and counter electrodes have a diameter in a range of 1 mm to 15 mm, and the protonic conductive electrolyte membrane has a thickness in a range of 0.1 mm to 1 mm. 
     
     
       127. The two-electrode electrochemical gas sensor as defined in claim 125, wherein the sensing and counter electrodes have a diameter of about 15 mm, and the protonic conductive electrolyte membrane has a thickness of about 0.17 mm. 
     
     
       128. The two-electrode electrochemical gas sensor as defined in claim 125, wherein the electrical conducting material of at least one of said sensing and counter electrodes is a proton-electron mixed conductive material having at least approximately 25 wt % of a proton conductor material. 
     
     
       129. The two-electrode electrochemical gas sensor as defined in claim 125, wherein said counter electrode is exposed to said water vapor at a 100% relative humidity. 
     
     
       130. The two-electrode electrochemical gas sensor as defined in claim 125, wherein the surface of said sensing electrode that is exposed to the ambient atmosphere has a surface area that is smaller than the surface area of the surface of the counter electrode that is exposed to said water vapor, whereby a positive pressure of said water vapor exists from the surface of said counter electrode exposed to said water vapor to the surface of said sensing electrode exposed to the ambient atmosphere.