Claims
- 1. An aqueous ionomer gel substantially free of organic solvents, having an ionomer solids content ranging from about 4% to about 18% by weight of the gel and a viscosity in excess of 5,000 centipoise at a shear rate of 10 seconds−1.
- 2. The gel of claim 1 wherein the ionomer is in the form of inverse micelles having the hydrophobic portion disposed outwardly and the ionic portion disposed inwardly.
- 3. The gel of claim 1 wherein the ionomer is a graft copolymer having a hydrophobic backbone and pendent ionic portions grafted thereto.
- 4. The gel of claim 1 wherein the ionomer is a proton conducting ionomer.
- 5. The gel of claim 4 wherein the proton conducting ionomer is a perfluorosulfonate ionomer.
- 6. The gel of claim 4 wherein the perfluorosulfonate ionomer is Nafion®.
- 7. The gel of claim 1 wherein the organic solvent contaminants are at a concentration below 4% by volume.
- 8. The gel of claim 1 wherein the organic solvent contaminants are at a concentration below 2% by volume.
- 9. The gel of claim 1 wherein the ionomer solids content ranges from about 6 to about 12% by weight.
- 10. The gel of claim 1 wherein the ionomer solids content is about 10% by weight.
- 11. The gel of claim 1 wherein the viscosity is in excess of 10,000 centipoise at a shear rate of 10 seconds−1.
- 12. A catalyst ink comprising an aqueous ionomer gel of claim 1 and a catalyst.
- 13. The catalyst ink of claim 12 wherein the catalyst is a noble metal catalyst.
- 14. The catalyst ink of claim 13 wherein the noble metal is platinum.
- 15. The catalyst ink of claim 12 having a catalyst solids contend ranging from about 4 to about 40% by weight of the catalyst ink.
- 16. The catalyst ink of claim 12 having a catalyst solids contend ranging from about 20 to about 40% by weight of the catalyst ink.
- 17. The catalyst ink of claim 12 further comprising a filler, binder, pore forming material or combination thereof.
- 18. A coated substrate, wherein the substrate has at least one surface coated with the catalyst ink of claim 12.
- 19. The coated substrate of claim 18 wherein the substrate is an electrode.
- 20. The coated substrate of claim 19 wherein the electrode is an electrochemical fuel cell electrode.
- 21. An electrochemical fuel cell comprising a coated surface of claim 18.
- 22. A membrane comprising the catalyst ink of claim 12.
- 23. A method for making an aqueous ionomer gel having an ionomer solids content ranging from about 4% to about 18% by weight of the gel and a viscosity in excess of 5,000 centipoise at a shear rate of 10 seconds−1, comprising the steps of:
providing a solution comprising an ionomer, water and a nonaqueous solvent having a boiling point less than 100° C., wherein the nonaqueous solvent is miscible with water; and evaporating the nonaqueous solvent at less than ambient pressure to produce the aqueous ionomer gel.
- 24. The method of claim 23 wherein the nonaqueous solvent is evaporated in the absence of applied heat.
- 25. The method of claim 23 further comprising the step of cooling the aqueous ionomer gel following the evaporating step.
- 26. The method of claim 23 further comprising the step of adding a catalyst to the aqueous ionomer gel following the evaporating step.
- 27. The method of claim 23 wherein the solution comprising the ionomer, water and the nonaqueous solvent further comprises a catalyst prior to the evaporation step.
- 28. The method of claim 23 wherein the nonaqueous solvent has a boiling point ranging from about 50 to less than 100° C.
- 29. The method of claim 23 wherein the nonaqueous solvent is an alcohol or a ketone.
- 30. The method of claim 29 wherein the alcohol is methanol.
- 31. The method of claim 29 wherein the ketone is acetone.
- 32. The method of claim 23 wherein the solution comprising the ionomer, water and the nonaqueous solvent is provided by addition of the nonaqueous solvent to an aqueous solution of ionomer.
- 33. The method of claim 23 wherein, prior to the step of evaporating, the solution comprising the ionomer, water and the nonaqueous solvent is heated to facilitate solvation of the ionomer.
- 34. The method of claim 33 wherein heating to facilitate solvation is at a temperature up to about 40° C.
- 35. The method of claim 23 wherein the solution comprising the ionomer, water and the nonaqueous solvent is provided by addition of water to a nonaqueous solution of ionomer.
- 36. A method for making an aqueous ionomer gel having an ionomer solids content ranging from about 4% to about 18% by weight of the gel and a viscosity in excess of 5,000 centipoise at a shear rate of 10 seconds−1, comprising the steps of:
rapidly cooling an aqueous ionomer solution to a temperature below −5° C. to form a substantially frozen form of the aqueous ionomer solution; and thawing the substantially frozen form of the aqueous ionomer solution to produce the aqueous ionomer gel.
- 37. The method of claim 36 wherein the aqueous ionomer solution is cooled at a rate greater than 6° C./minute.
- 38. The method of claim 37 wherein the aqueous ionomer solution is cooled at a rate greater than 10° C./minute.
- 39. The method of claim 36 wherein the aqueous ionomer solution is cooled to temperature below −25° C.
- 40. The method of claim 39 wherein the aqueous ionomer solution is cooled to temperature below about −70° C.
- 41. The method of claim 36 further comprising the step of diluting the aqueous ionomer gel to achieve a desired viscosity.
- 42. The method of claim 36 wherein the aqueous ionomer solution further comprises a catalyst.
- 43. The method of claim 39 further comprising the step of adding a catalyst to the aqueous gel.
- 44. The method of claim 23 or 36 further comprising the step of suspending a catalyst ink in the aqueous ionomer gel after or simultaneously with formation of the aqueous ionomer gel to yield a catalyst ink.
- 45. The method of claim 44 further comprising the step of applying the catalyst ink to at least one surface of a substrate.
- 46. The method of claim 45 further comprising the step of annealing the catalyst ink.
- 47. A substrate made by the method of claim 45.
- 48. An annealed substrate made by the method of claim 46.
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a divisional of U.S. patent application Ser. No. 10/015,528, filed Dec. 12, 2001, now allowed, which application is incorporated herein by reference in its entirety.
Divisions (1)
|
Number |
Date |
Country |
Parent |
10015528 |
Dec 2001 |
US |
Child |
10712400 |
Nov 2003 |
US |