Claims
- 1. A method of conditioning a membrane electrode assembly of a direct methanol fuel cell comprising the steps of:
supplying methanol to a first surface of the membrane electrode assembly, said first surface intended for use as a fuel cell anode; supplying air to a second surface of the membrane electrode assembly, said second surface intended for use as a fuel cell cathode; and drawing an electrical current of polarity reversed to that used in a functioning direct methanol fuel cell through the membrane electrode assembly; wherein surface oxides present on the first surface are reduced.
- 2. The method of claim 1, wherein the first surface comprises a platinum-ruthenium electrocatalyst.
- 3. The method of claim 2, wherein the second surface comprises a platinum electrocatalyst.
- 4. The method of claim 1, wherein the method further comprises the step of raising the temperature of the membrane electrode assembly to a temperature of from about 20° C. to about 100° C. during passage of the conditioning current.
- 5. The method of claim 4, wherein the step of raising the temperature of the membrane electrode assembly comprises raising the temperature of the membrane electrode assembly to a temperature of from about 70° C. to about 90° C.
- 6. The method of claim 5, wherein the step of raising the temperature of the membrane assembly comprises raising the temperature of the membrane electrode assembly to a temperature of about 80° C.
- 7. The method of claim 1, wherein the step of drawing an electrical current of polarity reversed to that used in a functioning direct methanol fuel cell through the membrane electrode assembly comprises drawing a current of from about 100 mA/cm2 to about 200 mA/cm2 through the membrane electrode assembly.
- 8. The method of claim 7, wherein the step of drawing an electrical current of polarity reversed to that used in a functioning direct methanol fuel cell through the membrane electrode assembly comprises drawing a current of from about 120 mA/cm2 to about 180 mA/cm2 through the membrane electrode assembly.
- 9. The method of claim 8, wherein the step of drawing an electrical current of polarity reversed to that used in a functioning direct methanol fuel cell through the membrane electrode assembly comprises drawing a current of 150 mA/cm2 through the membrane electrode assembly.
- 10. The method of claim 1, wherein the methanol is about 1 M.
- 11. The method of claim 1, wherein the step of drawing an electrical current of polarity reversed to that used in a functioning direct methanol fuel cell through the membrane electrode assembly is applied for a period of from about 1 minute to about 120 minutes in length.
- 12. The method of claim 1, wherein the step of drawing an electrical current of polarity reversed to that used in a functioning direct methanol fuel cell through the membrane electrode assembly is applied for a period of from about 15 minutes to about 60 minutes in length.
- 13. A method of conditioning a membrane electrode assembly of a direct methanol fuel cell comprising the steps of:
supplying methanol to a first surface of the membrane electrode assembly intended for use as a fuel cell anode; allowing the methanol to cross over a polymer electrolyte membrane of the membrane electrode assembly to a second surface of the membrane electrode assembly; said second surface intended for use as a fuel cell cathode; and applying a voltage to the membrane electrode assembly having the same polarity as an operating direct methanol fuel cell; wherein methanol is oxidized at the second surface of the membrane electrode assembly, and surface oxides at the first surface is reduced.
- 14. The method of claim 13, wherein the second surface of the membrane electrode assembly is also supplied with air.
- 15. The method of claim 13, wherein the second surface of the membrane electrode assembly is shielded from exposure to air.
- 16. The method of claim 14, wherein the first surface comprises a platinum-ruthenium electrocatalyst.
- 17. The method of claim 14, wherein the second surface comprises a platinum electrocatalyst.
- 18. The method of claim 13, wherein the method further comprises the step of raising the temperature of the membrane electrode assembly to a temperature of from about 20° C. to about 100° C. during conditioning.
- 19. The method of claim 18, wherein the step of raising the temperature of the membrane electrode assembly comprises raising the temperature of the membrane electrode assembly to a temperature of from about 70° C. to about 90° C.
- 20. The method of claim 19, wherein the step of raising the temperature of the membrane assembly comprises raising the temperature of the membrane electrode assembly to a temperature of about 80° C.
- 21. The method of claim 13, wherein the step of applying a voltage to the membrane electrode assembly having the same polarity as an operating direct methanol fuel cell comprises applying a voltage of from about 0.2 V to about 1.6 V to the membrane electrode assembly.
- 22. The method of claim 21, wherein the step of applying a voltage to the membrane electrode assembly having the same polarity as an operating direct methanol fuel cell comprises applying a voltage of from about 0.5 V to about 1.2 V through the membrane electrode assembly.
- 23. The method of claim 22, wherein the step of applying a voltage to the membrane electrode assembly having the same polarity as an operating direct methanol fuel cell comprises applying a voltage of about 0.8 V to the membrane electrode assembly.
- 24. The method of claim 13, wherein the methanol has a concentration of from about 1 M to about 17 M.
- 25. The method of claim 24, wherein the methanol has a concentration of from about 2 M to about 4 M.
- 26. The method of claim 25, wherein the methanol has a concentration of about 3 M.
- 27. The method of claim 13, wherein the step of applying a voltage to the membrane electrode assembly of having the same polarity as an operating direct methanol fuel cell is applied for a period of from about 1 minute to about 120 minutes in length.
- 28. The method of claim 13, wherein the step of applying a voltage to the membrane electrode assembly having the same polarity as an operating direct methanol fuel cell is applied for a period of from about 15 minutes to about 60 minutes in length.
- 29. A method of conditioning a membrane electrode assembly of a direct methanol fuel cell comprising the steps of:
supplying methanol to a first surface of the membrane electrode assembly, said first surface intended for use as a fuel cell anode; supplying air to a second surface of the membrane electrode assembly, said second surface intended for use as a fuel cell cathode; raising the temperature of the membrane electrode assembly to a temperature of from about 60° C. to about 100° C.; and drawing an electrical current of 150 mA/cm2 through the membrane electrode assembly having a polarity opposite to that in a functioning direct methanol fuel cell for a period of from about 1 minute to about 120 minutes, wherein surface oxides present on the catalyst on the first surface are reduced.
- 30. The method of claim 29, wherein the step of drawing an electrical current of 150 mA/cm2 through the membrane electrode assembly having a polarity opposite to that in a functioning direct methanol fuel cell is conducted for a period of from about 15 minutes to about 60 minutes.
- 31. A method of conditioning a membrane electrode assembly of a direct methanol fuel cell comprising the steps of:
supplying methanol having a concentration of from about 1M to about 17 M to a first surface of the membrane electrode assembly intended for use as a fuel cell anode; allowing the methanol to cross over a polymer electrolyte membrane of the membrane electrode assembly to a second surface of the membrane electrode assembly; said second surface intended for use as a fuel cell cathode; raising the temperature of the membrane electrode assembly to a temperature of from about 20° C. to about 100° C.; and applying a voltage of about 0.8 V having the same polarity as an operating direct methanol fuel cell to the membrane electrode assembly for a period of from about 1 minute to about 120 minutes; wherein methanol is oxidized at the second surface of the membrane electrode assembly.
- 32. The method of claim 31, wherein the step of applying a voltage of about 0.8V having the same polarity as an operating direct methanol fuel cell to the membrane electrode assembly is conducted for a period of from about 15 minutes to about 60 minutes.
GOVERNMENT RIGHTS
[0001] This invention was made with Government support under Contract Number W-7405-ENG-36 awarded by the United States Department of Energy to The Regents of the University of California. The Government has certain rights in the invention.
Provisional Applications (1)
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Number |
Date |
Country |
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60457390 |
Mar 2003 |
US |