Fiber structures including catalysts and methods associated with the same

• US 20060019819A1
• Filed: 07/23/2004
• Published: 01/26/2006
• Est. Priority Date: 07/23/2004
• Status: Active Grant

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Shao-Horn, Yang, Kurpiewski, John Paul, Horn, Quinn C.
• Granted Patent: US 7,229,944 B2
• Time in Patent Office: Days
• US Class Current: 502/4
• CPC Class Codes: D01D 5/0038 the fibre formed by solvent evaporation, i.e. dry electro-spinning
• CPC Class Codes: D01F 1/02 Addition of substances to the spinning solution or to the melt addition of substances to viscose D01F2/08
• CPC Class Codes: D01F 9/14 by decomposition of organic filaments
• CPC Class Codes: D01F 9/20 from polyaddition, polycondensation or polymerisation products D01F9/145, D01F9/16, D01F9/18 take precedence
• CPC Class Codes: D01F 9/24 from macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
• CPC Class Codes: H01M 4/663 containing carbon or carbonaceous materials as conductive part, e.g. graphite, carbon fibres
• CPC Class Codes: H01M 4/90 Selection of catalytic material
• CPC Class Codes: H01M 4/9083 on carbon or graphite
• CPC Class Codes: H01M 4/926 on carbon or graphite
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02E 60/50 Fuel cells
• CPC Class Codes: Y10T 428/2918 including free carbon or carbide or therewith [not as steel]

Abstract

Fiber structures that include a catalytic material are provided. The fiber structures (e.g., membranes) may be formed of interconnected carbon fibers. The catalytic material may be in the form of nanosize particles supported on the fibers. In one method of the invention, the structures are produced by electrospinning a polymeric material fiber structure that is subsequently converted to a carbon fiber structure in a heat treatment step which also causes the catalytic material particles to nucleate on the carbon fibers and grow to a desired size. The catalytic material may be uniformly distributed across the carbon fiber structure and the amount of catalytic material may be controlled. These factors may enhance catalytic performance and/or enable using less catalytic material for equivalent catalytic performance which can lead to cost savings, amongst other advantages. The fiber structures may be used in a variety of applications including electrodes in batteries and fuel cells.

Claims

1. A method of forming a carbon fiber structure comprising:

electrospinning a polymer solution to form a polymeric material fiber structure; and

heat treating the polymeric material fiber structure to convert the polymeric material fiber structure to a carbon fiber structure including catalytic material particles supported on the carbon fiber structure.

2. The method of claim 1, wherein the polymer solution comprises a catalytic material precursor.

3. The method of claim 2, wherein the catalytic material precursor is dissolved in the polymer solution.

4. The method of claim 2, wherein the catalytic material precursor comprises solid catalytic material particles dispersed in the polymer solution.

5. The method of claim 1, wherein the catalytic material particles are nucleated on surfaces of carbon fiber of the structure during heat treating.

6. The method of claim 1, wherein the catalytic material particles have an average particle size of less than about 50 nanometers.

7. The method of claim 1, further comprising forming the polymer solution by dissolving a polymeric material and a salt of a catalytic metal.

8. The method of claim 7, further comprising mixing the polymer solution to form a homogenous polymer solution prior to electrospinning.

9. The method of claim 1, wherein heat treating comprises heating the polymeric material fiber structure to a temperature within a first temperature range followed by a temperature within a second temperature range greater than the first range.

10. The method of claim 9, wherein the first temperature range is between about 100°

C. and about 500°

C. and the second temperature range is between about 750°

C. and about 1150°

C.

11. The method of claim 1, wherein the carbon fiber structure comprises carbon fiber having an average diameter of between about 100 nm and about 500 nm.

12. The method of claim 1, further comprising forming an electrochemical device comprising the carbon fiber structure as an electrode.

13. The method of claim 1, wherein carbon fiber of the structure has a resistivity of less than about 0.1 Ohms-m.

14. The method of claim 1, wherein the carbon fiber structure is a membrane.

15. A method of forming a carbon fiber structure comprising:

converting a polymeric material fiber structure to a carbon fiber structure; and

associating a catalytic material with the carbon fiber structure.

16. The method of claim 15, further comprising electrospinning a polymer solution to form the polymeric material fiber structure.

17. The method of claim 15, wherein converting the polymeric material fiber structure comprises heat treating the polymeric material fiber structure to form a carbon fiber structure.

18. The method of claim 17, wherein heat treating comprises heating the polymeric material fiber structure to a temperature between about 100°

C. and about 500°

C. followed by a temperature between about 750°

C. and about 1150°

C.

19. The method of claim 15, wherein associating the catalytic material with the carbon fiber structure comprises forming catalytic material particles supported on the carbon fiber structure.

20. The method of claim 19, comprising nucleating the catalytic material particles on the carbon fiber structure during heat treatment.

21. The method of claim 19, wherein the catalytic material particles have an average particle size of less than about 50 nanometers.

22. The method of claim 15, wherein the carbon fiber structure comprises carbon fiber having an average diameter of between about 100 nm and about 500 nm.

23. The method of claim 15, further comprising forming an electrochemical device comprising the carbon fiber structure as an electrode.

24. A structure comprising:

a carbon fiber structure including at least one carbon fiber having a length of greater than about 500 microns; and

a catalytic material supported on the carbon fiber structure.

25. The structure of claim 24, comprising catalytic material particles supported on the carbon fiber structure.

26. The structure of claim 25, wherein the catalytic material particles have an average particle size of less than about 50 nanometers.

27. The structure of claim 25, wherein the catalytic material particles are formed on a surface of a carbon fiber of the structure.

28. The structure of claim 25, wherein the catalytic material particles are dispersed substantially throughout the carbon fiber structure.

29. The structure of claim 24, wherein the catalytic material concentration is substantially constant throughout the carbon fiber structure.

30. The structure of claim 24, wherein the catalytic material concentration is less than 0.2 mg catalytic material/cm² area of the carbon fiber structure.

31. The structure of claim 24, wherein carbon fiber of the structure has a conductivity of less than 0.1 Ohm-m.

32. The structure of claim 24, wherein the catalytic material is a metal.

33. The structure of claim 24, wherein the carbon fiber structure includes at least one carbon fiber having a length of greater than about 1 cm.

34. The structure of claim 24, wherein carbon fibers of the carbon fiber structure are solid.

35. The structure of claim 24, wherein a majority of the carbon fibers of the structure have a length of greater than about 500 microns.

36. The structure of claim 24, wherein carbon fiber of the structure has an average diameter of less than about 500 nanometers.

37. The structure of claim 24, wherein the structure is an electrode.

38. The structure of claim 24, wherein the carbon fiber structure has a thickness of less than 10 micron.

39. The structure of claim 24, wherein the carbon fiber structure is a membrane.

40. An electrode comprising:

a carbon fiber structure; and

a catalytic material supported on the carbon fiber structure, wherein the catalytic material concentration is less than 0.2 mg catalytic material/cm² area of the carbon fiber structure.

41. The electrode of claim 40, comprising catalytic material particles supported on the carbon fiber structure.

42. The electrode of claim 40, wherein the catalytic material particles have an average particle size of less than about 50 nanometers.

43. The electrode of claim 40, wherein the catalytic material particles are formed on a surface of a carbon fiber of the structure.

44. The electrode of claim 40, wherein the catalytic material concentration is substantially constant throughout the carbon fiber structure.

45. The electrode of claim 40, wherein the catalytic material concentration is less than 0.1 mg catalytic material/cm² area of the carbon fiber structure.

46. The electrode of claim 40, wherein the catalytic material concentration is between 0.02 mg catalytic material/cm² area of the carbon fiber structure and 0.2 mg catalytic material/cm² area of the carbon fiber structure.

47. The electrode of claim 40, wherein the catalytic material is a metal.

48. The electrode of claim 40, wherein the electrode has a thickness of less than 1 micron.