Fuel cell CO sensor

• US 6,001,499 A
• Filed: 10/24/1997
• Issued: 12/14/1999
• Est. Priority Date: 10/24/1997
• Status: Expired due to Term

• Current Assignee: GM Global Technology Operations LLC (General Motors Company), Regents of the University of California (University of California)
• Original Assignee: General Motors Corporation (Motors Liquidation Co. GUC Trust)
• Inventors: Borup, Rodney Lynn, Gutowski, Stanley, Grot, Stephen Andreas, Neutzler, Jay Kevin, Weisbrod, Kirk, Meltser, Mark Alexander
• Primary Examiner(s): Nuzzolillo, Maria
• Assistant Examiner(s): Martin, Angela J.
• Application Number:
  US08/957,563
• Time in Patent Office: 781 Days
• Field of Search: 429/12, 429/17, 429/23, 429/22, 429/90, 204/426, 204/424, 204/422, 422/98, 422/94, 48/127.7
• US Class Current: 429/412
• 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: H01M 2300/0082 Organic polymers
• CPC Class Codes: H01M 8/04089 of gaseous reactants
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

The CO concentration in the H₂ feed stream to a PEM fuel cell stack is monitored by measuring current and/or voltage behavior patterns from a PEM-probe communicating with the reformate feed stream. Pattern recognition software may be used to compare the current and voltage patterns from the PEM-probe to current and voltage telltale outputs determined from a reference cell similar to the PEM-probe and operated under controlled conditions over a wide range of CO concentrations in the H₂ fuel stream. A CO sensor includes the PEM-probe, an electrical discharge circuit for discharging the PEM-probe to monitor the CO concentration, and an electrical purging circuit to intermittently raise the anode potential of the PEM-probe'"'"'s anode to at least about 0.8 V (RHE) to electrochemically oxidize any CO adsorbed on the probe'"'"'s anode catalyst.

Claims

1. A carbon monoxide sensor comprising a gas-monitoring PEM-probe including a proton exchange membrane having an anode and a cathode affixed to opposing first and second surfaces of said membrane, a first electrical current collector engaging said anode, a second electrical current collector engaging said cathode, an electrical discharge circuit connectable between said current collectors, said discharge circuit having a first electrical resistance valued for discharging said PEM-probe at a first rate selected to monitor the degrading output of said PEM-probe incident to CO contamination of said anode, an electrical purging circuit connectable between said current collectors, said purging circuit having a second electrical resistance which is less than said first electrical resistance such that upon discharge of said PEM-probe through said second resistance the potential of said anode is raised to at least 0.8 V (RHE) to effect electrochemical oxidation of any CO adsorbed on said anode, and an electrical switch in electrical series connection between said current collectors and adapted to intermittently, alternately electrically connect said current collectors to said discharge and said purging circuits.

2. A sensor in accordance with claim 1 including a timer operatively connected to said switch for effecting said alternate connecting of said current collectors at predetermined time intervals.

3. A sensor in accordance with claim 2 including a timer operatively connected to said switch for periodically effecting said alternate connecting of said current collectors.

4. A sensor in accordance with claim 1 including a passage for admitting a gas to be monitored to said anode, and a valve operatively associated with said passage for restricting the flow of said gas to said anode when said switch connects said current collectors to said purging circuit.

5. A carbon monoxide sensor comprising a gas-monitoring PEM-probe including a proton exchange membrane having an anode and a cathode affixed to opposing first and second surfaces of said membrane, a first electrical current collector engaging said anode, a second electrical current collector engaging said cathode, an electrical discharge circuit connectable between said current collectors, said discharge circuit having a first electrical resistance valued for discharging said PEM-probe at a rate selected to monitor the degrading output of said PEM-probe incident to CO contamination of said anode, an electrical purging circuit connectable between said current collectors, said purging circuit including a voltage source having a potential capable of raising the potential of said anode to at least about 0.8 V (RHE) to effect electrochemical oxidation of any CO adsorbed on said anode, and an electrical switch in electrical series connection between said current collectors and adapted to intermittently, alternately connect said contacts to said discharge and said purging circuits.

6. A sensor according to claim 5 wherein said voltage source is a charge storage device.

7. A sensor according to claim 6 wherein said charge storage device is a voltaic device.

8. A sensor according to claim 6 wherein said voltage source is a capacitor.

9. A sensor according to claim 5 including a timer operatively connected to said switch for periodically effecting said alternate connecting of said contacts.

10. In a fuel cell system comprising (a) a stack of PEM H₂ --O₂ fuel cells each comprising principally a proton exchange membrane having an anode and a cathode affixed to opposing first and second surfaces thereof, a first flow channel adjacent said anode for flowing hydrogen into contact with said anode, and a second flow channel adjacent said cathode for flowing an oxygen-bearing gas into contact with said cathode, (b) an oxygen-feed manifold supplying oxygen to said cells, and (c) an hydrogen-feed manifold supplying hydrogen to said cells, the improvement comprising:

a carbon monoxide sensor communicating with said hydrogen-feed manifold for sensing the concentration of any CO in said manifold, said sensor comprising a gas-monitoring PEM-probe including a proton exchange membrane having an anode and a cathode affixed to opposing first and second surfaces of said membrane such that said anode from said PEM-probe is exposed to said hydrogen from said hydrogen-feed manifold, a first electrical current collector engaging the anode from said PEM-probe, a second electrical current collector engaging the cathode of said PEM-probe, an electrical discharge circuit having a first electrical resistance valued for discharging said PEM-probe at a rate selected to monitor the degrading output of said PEM-probe incident to CO contamination of said anode, an electrical purging circuit adapted to raise the potential of said anode from said PEM-probe sufficiently to effect electrochemical oxidation of any CO adsorbed on said anode, and an electrical switch in electrical series connection between said current collectors and adapted to alternately connect said contacts to said discharge and said purging circuits.

11. A carbon monoxide sensor comprising a gas-monitoring PEM-probe including a proton exchange membrane having an anode and a cathode affixed to opposing first and second surfaces of said membrane, a first electrical current collector engaging said anode, a second electrical current collector engaging said cathode, an electrical discharge circuit connectable between said current collectors, said discharge circuit having a first electrical resistance valued for discharging said PEM-probe at a first rate selected to monitor the degrading output of said PEM-probe incident to CO contamination of said anode, an electrical purging circuit connectable between said current collectors an adapted to raise the potential of said anode to at least 0.8 V (RHE) to effect electrochemical oxidation of any CO adsorbed on said anode, and an electrical switch in electrical series connection between said current collectors and adapted to intermittently, alternately electrically connect said current collectors to said discharge and said purging circuits.