FUEL CELLS

• US 20100112388A1
• Filed: 07/19/2007
• Published: 05/06/2010
• Est. Priority Date: 07/19/2006
• Status: Active Grant

• Current Assignee: Clean Power Limited
• Original Assignee: ACAL Energy Ltd
• Inventors: Knuckey, Kathryn, Creeth, Andrew
• Granted Patent: US 9,136,554 B2
• Time in Patent Office: Days
• US Class Current: 429/492
• CPC Class Codes: C07D 213/61 Halogen atoms or nitro radicals
• CPC Class Codes: H01M 4/8605 Porous electrodes
• CPC Class Codes: H01M 4/9041 Metals or alloys H01M4/92 takes precedence
• CPC Class Codes: H01M 8/0618 Reforming processes, e.g. autothermal, partial oxidation or steam reforming
• CPC Class Codes: H01M 8/1053 consisting of layers of polymers with at least one layer being ionically conductive
• CPC Class Codes: H01M 8/20 Indirect fuel cells, e.g. fuel cells with redox couple being irreversible H01M8/18 takes precedence
• CPC Class Codes: Y02E 60/50 Fuel cells
• CPC Class Codes: Y02P 20/584 Recycling of catalysts

Abstract

This invention provides a redox fuel cell comprising an anode and a cathode separated by an ion selective polymer electrolyte membrane; means for supplying a fuel to the anode region of the cell; means for supplying an oxidant to the cathode region of the cell; means for providing an electrical circuit between the anode and the cathode; a non-volatile catholyte solution flowing in fluid communication with the cathode, the catholyte solution comprising a redox mediator which is at least partially reduced at the cathode in operation of the cell, and at least partially regenerated by, optionally indirect, reaction with the oxidant after such reduction at the cathode, and a transition metal complex of a multidentate N-donor ligand as a redox catalyst catalysing the regeneration of the mediator.

Claims

1. A redox fuel cell comprising:

an anode region comprising an anode and a cathode region comprising a cathode, said regions being separated by an ion selective polymer electrolyte membrane;

a fuel passage through which fuel is supplied to the anode region of the cell;

an oxidant inlet that supplies an oxidant to the cathode region of the cell;

an electrical circuit between the anode and the cathode;

a catholyte solution comprising at least one non-volatile catholyte component flowing in fluid communication with the cathode, the catholyte solution comprising a redox mediator, wherein the redox mediator is at least partially reduced at the cathode in operation of the cell, and at least partially regenerated by reaction with the oxidant after such reduction at the cathode; and

wherein the catholyte solution further comprises a complexed multidentate N-donor ligand as at least one of the redox mediator and a redox catalyst catalyzing the regeneration of the redox mediator.

2. A fuel cell according to claim 1 wherein the catholyte solution comprises the complexed multidentate N-donor ligand as said redox mediator, and as said redox catalyst.

3. A fuel cell according to claim 1 wherein the catholyte solution comprises a material which is not the complexed multi-dentate N-donor ligand as the redox mediator and the complexed multidentate N-donor ligand as the redox catalyst for the redox mediator.

4. A fuel cell according to claim 1 wherein the catholyte solution comprises the complexed multidentate N-donor ligand as the redox mediator and a further material which is not the complexed multi-dentate N-donor ligand as the redox catalyst for the ligand complex redox mediator.

5. A fuel cell according to claim 1 wherein in operation of the cell, the oxidant is reduced in the catholyte solution by the redox catalyst.

6. A fuel cell according to claim 5 wherein the redox catalyst, after reduction of the oxidant in the catholyte solution, is effective to at least partially oxidize the mediator to regenerate the redox mediator after its reduction at the cathode.

7. A fuel cell according to claim 1 wherein the catholyte solution is an aqueous solution.

8. A fuel cell according to claim 1 wherein the complexed multidentate N-donor ligand comprises a transition metal complex of the multidentate N-donor ligand.

9. A fuel cell according to claim 8 wherein the multidentate N-donor ligand comprises at least one pyridine substituent.

10. A fuel cell according to claim 9 wherein the multidentate N-donor ligand comprises at least two pyridine substituents.

11. A fuel cell according to claim 10 wherein the multidentate ligand is complexed to a transition metal via 3 to 6 nitrogen atoms.

12. A fuel cell according to claim 11 wherein one to five of said nitrogen atoms are contained in one or more aromatic heterocycles.

13. A fuel cell according to claim 1 wherein the N-donor ligand has the structure:

14. A fuel cell according to claim 1 wherein the multidentate N-donor ligand has the structure:

15. A fuel cell according to claim 1 wherein the multidentate N-donor ligand has the structure:

16. A fuel cell according to claim 1 wherein the multidentate N-donor ligand is selected from the group consisting of N4Py (N,N-bis(pyridine-2-yl-methyl)-bis(pyridine-2-yl)methylamine) and derivatives thereof, pydien (1,9-bis(2-pyridyl)-2,5,8-triazanonane) and derivatives thereof, trilen (N-methyl-N,N′

,N′

-tris(2-pyridylmethyl)ethane-1,2-diamine) and derivatives thereof, and tpen (N,N,N′

,N′

-Tetrakis(2-pyridylmethyl)ethane-1,2-diamine) and derivatives thereof.

17. A fuel cell according to claim 13 wherein said organic groups which include at least one N donor atom are aromatic heterocycles.

18. A fuel cell according to claim 17 wherein said aromatic heterocycles comprise pyridine or pyridine derivatives.

19. A fuel cell according to claim 1 wherein the ion selective polymer electrolyte membrane is a cation selective membrane which is selective in favor of protons versus other cations.

20. A fuel cell according to claim 19 wherein the catholyte is acidic.

21. A fuel cell according to claim 1 wherein the ion selective polymer electrolyte membrane is an anion selective membrane.

22. A fuel cell according to claim 21 wherein the catholyte is alkaline.

23. A fuel cell according to claim 1 wherein the ion selective polymer electrolyte membrane is a bimembrane.

24. A fuel cell according to claim 1 wherein the redox mediator comprises a modified ferrocene species.

28. The catholyte solution of claim 1, wherein the redox mediator is at least partially regenerated by indirect reaction with the oxididant after reduction at the cathode.

29. A fuel cell according to claim 14 wherein said organic groups which include at least one N donor atom are aromatic heterocycles.

30. A fuel cell according to claim 29 wherein said aromatic heterocycles comprise pyridine or pyridine derivatives.

31. A fuel cell according to claim 15 wherein said organic groups which include at least one N donor atom are aromatic heterocycles.

32. A fuel cell according to claim 31 wherein said aromatic heterocycles comprise pyridine or pyridine derivatives.

53. A fuel cell according to claim 12, wherein the aromatic heterocycles are substituted aromatic heterocycles.

54. A fuel cell according to claim 17, wherein the aromatic heterocycles are substituted aromatic heterocycles.

55. A fuel cell according to claim 29, wherein the aromatic heterocycles are substituted aromatic heterocycles.

56. A fuel cell according to claim 31, wherein the aromatic heterocycles are substituted aromatic heterocycles.

25. A catholyte solution for use in a fuel cell, the catholyte solution comprising:

a redox mediator; and

a redox catalyst;

wherein at least one of the redox mediator and redox catalyst comprise a multidentate N-donor ligand complex.

26. A method of operating a proton exchange membrane fuel cell comprising the steps of:

a) forming H⁺ions at an anode situated adjacent to a proton exchange membrane;

b) supplying the catholyte solution of claim 25 with its redox mediator in an oxidized state and its redox catalyst in a reduced state to a cathode situated oppositely adjacent to the proton exchange membrane; and

c) allowing the redox mediator to become reduced upon contact with the cathode concomitantly with H⁺ions passing through the membrane to balance charge.

33. A catholyte solution according to claim 25 wherein the catholyte solution comprises the complexed multidentate N-donor ligand as said redox mediator, and as said redox catalyst.

34. A catholyte solution according to claim 25 wherein the catholyte solution comprises a material which is not the complexed multi-dentate N-donor ligand as the redox mediator and the complexed multidentate N-donor ligand as the redox catalyst for the redox mediator.

35. A catholyte solution according to claim 25 wherein the catholyte comprises the complexed multidentate N-donor ligand as the redox mediator and a further material which is not the complexed multi-dentate N-donor ligand as the redox catalyst.

36. A catholyte solution according to claim 25 wherein the catholyte solution is an aqueous solution.

37. A catholyte solution according to claim 25 wherein the complexed multidentate N-donor ligand comprises a transition metal complex of the multidentate N-donor ligand.

38. A catholyte solution according to claim 37 wherein the multidentate N-donor ligand comprises at least one pyridine substituent.

39. A catholyte solution according to claim 38 wherein the multidentate N-donor ligand comprises at least two pyridine substituents.

40. A catholyte solution according to claim 39 wherein the multidentate ligand is complexed to a transition metal via 3 to 6 nitrogen atoms.

41. A catholyte solution according to claim 40 wherein one to five of said nitrogen atoms are contained in one or more aromatic heterocycles.

42. A catholyte solution according to claim 25 wherein the N-donor ligand has the structure:

43. A catholyte solution according to claim 42 wherein said organic groups which include at least one N donor atom are aromatic heterocycles.

44. A catholyte solution according to claim 43 wherein said aromatic heterocycles comprise pyridine or pyridine derivatives.

45. A catholyte solution according to claim 25 wherein the multidentate N-donor ligand has the structure:

46. A catholyte solution according to claim 45 wherein said organic groups which include at least one N donor atom are aromatic heterocycles.

47. A catholyte solution according to claim 46 wherein said heterocycles comprise pyridine or pyridine derivatives.

48. A catholyte solution according to claim 25 wherein the multidentate N-donor ligand has the structure:

49. A catholyte solution according to claim 48 wherein said organic groups which include at least one N donor atom are aromatic heterocycles.

50. A catholyte solution according to claim 49 wherein said aromatic heterocycles comprise pyridine or pyridine derivatives.

51. A catholyte solution according to claim 25 wherein the multidentate N-donor ligand is selected from the group consisting of N4Py (N,N-bis(pyridine-2-yl-methyl)-bis(pyridine-2-yl)methylamine) and derivatives thereof, from pydien (1,9-bis(2-pyridyl)-2,5,8-triazanonane) and derivatives thereof, trilen (N-methyl-N,N′

,N′

-tris(2-pyridylmethypethane-1,2-diamine and derivatives thereof, and tpen (N,N,N′

,N′

-Tetrakis(2-pyridylmethypethane-1,2-diamine) and derivatives thereof.

52. A catholyte solution according to claim 25 wherein the redox mediator comprises a modified ferrocene species.

57. A catholyte solution according to claim 41, wherein the aromatic heterocycles are substituted aromatic heterocycles.

58. A catholyte solution according to claim 43, wherein the aromatic heterocycles are substituted aromatic heterocycles.

59. A catholyte solution according to claim 46, wherein the aromatic heterocycles are substituted aromatic heterocycles.

60. A catholyte solution according to claim 49, wherein the aromatic heterocycles are substituted aromatic heterocycles.

27. N-methyl-N,N′

,N′

,-tris(2-(4-chloro)-pyridylmethypethane-1,2-diamine (trilen-Cl₃).