RAPID RESPONSE SENSOR FOR CARBON MONOXIDE

Abstract

Species detection techniques are described based on measurement of a dynamic response to an external stimulus. One embodiment includes a voltage stimulus applied to a polymer electrolyte fuel cell (PEFC), with the response to said stimulus used to measure CO concentration on the anode catalyst. The principles of symbolic dynamics, finite state machines or a simplified peak response-to-asymptotic value measurement can be used to achieve a high degree of precision for measuring CO concentrations. Using the techniques of the present invention, CO poisoning of a fuel cell can be monitored and diagnosed before reaching a critical condition, thereby allowing early implementation of mitigation or graceful degradation strategies.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a polymer electrolyte fuel cell (PEFC);

FIG. 2 illustrates a finite state automation; and

FIGS. 3A and 3B show the current responses to a particular stimulus for various known levels of carbon monoxide (CO) in a polymer electrolyte fuel cell.

Claims

1. An electrochemical sensor for a chemical species, which chemical species is a contaminant in a fluid stream, comprising: an electrochemical device having an electrode, said electrode having a catalyst facilitating a chemical reaction in a component of a fluid stream, said catalyst being capable of being poisoned by a contaminant in said fluid stream;a voltage source, said voltage source operable to provide an electrical stimulus to said electrode; anda monitor, said monitor operable to detect and monitor a time-dependent response of said electrode to said electrical stimulus,said time-dependent response being correlatable with the presence and/or amount of said contaminant.

2. The sensor of claim 1, wherein said electrode is an anode of a fuel cell, said catalyst includes platinum, said component of said fluid stream is hydrogen gas, and the contaminant is carbon monoxide.

3. The sensor of claim 2, wherein the electrical stimulus is an overvoltage applied to said fuel cell, the overvoltage being sufficient to oxidize molecules of said contaminant bound to said catalyst.

4. The sensor of claim 3, wherein the overvoltage is applied to the fuel cell for a time period of between 1 and 20 seconds.

5. The sensor of claim 2, wherein said time-dependent response is the magnitude of the peak-to-asymptotic output potential of said fuel cell at a time after the initiation of the electrical stimulus.

6. An electrochemical sensor for a chemical species, which chemical species is a contaminant in a fluid stream, said sensor comprising: a fuel cell, said fuel cell having an anode and an anode catalyst facilitating a chemical reaction in a component of a fluid stream, said anode catalyst being capable of being poisoned by a contaminant in said fluid stream;an electrical circuit, said circuit having a voltage source, a variable resistor and a monitor;said voltage source and variable resistor operable to provide an overvoltage to said anode of said fuel cell; andsaid monitor operable to detect and monitor a time-dependent response of said anode to said overvoltage,the time-dependent response being correlatable to a contaminant bound to said anode catalyst.

7. The sensor of claim 6, wherein said overvoltage is sufficient to oxidize molecules of said contaminant bound to said anode catalyst.

8. The sensor of claim 6, wherein the circuit is operable to apply overvoltage to said anode for a time period of between 0.5 and 50 seconds.

9. The sensor of claim 6, wherein the time-dependent response to said overvoltage applied to said anode is the magnitude of peak-to-asymptotic output potential of said fuel cell after the initiation of the overvoltage.

10. The sensor of claim 6, wherein said fuel cell is operable to facilitate a chemical reaction in a fuel gas.

11. A method for detecting the presence and/or a concentration of a contaminant within a fluid stream, the method comprising: exposing a catalyst to a fluid stream, the fluid stream having a contaminant therein, the contaminant poisoning the catalyst;applying a stimulus to the catalyst; andmonitoring the time-dependent catalyst performance to the stimulus, the time-dependent catalyst performance being correlatable to presence and/or concentration of the contaminant bound to the catalyst.

12. The method of claim 11, wherein applying the stimulus to the catalyst removes the contaminant from the catalyst.

13. The method of claim 11, wherein the stimulus is an electrical potential sufficient to oxidize the contaminant bound to the catalyst; and monitoring the time dependence of the catalyst performance comprises monitoring the output potential of a fuel cell with the catalyst therein.

14. The method of claim 11, wherein the contaminant is carbon monoxide.

15. The method of claim 13, wherein the contaminant is carbon monoxide within a fuel gas supplied to the fuel cell.