Fuel cells

• US 9,136,554 B2
• Filed: 07/19/2007
• Issued: 09/15/2015
• Est. Priority Date: 07/19/2006
• Status: Expired due to Fees

• Current Assignee: Clean Power Limited
• Original Assignee: ACAL Energy Ltd
• Inventors: Knuckey, Kathryn, Creeth, Andrew
• Primary Examiner(s): Ruddock, Ula C
• Assistant Examiner(s): PARSONS, THOMAS H
• Application Number:
  US12/374,371
• Publication Number:
  US 20100112388A1
• Time in Patent Office: 2,980 Days
• Field of Search: 429/99, 429/500, 429/502, 429/504, 429/505
• US Class Current: 1/1
• 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 catalyzing 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; and

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 and a separate redox catalyst, 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;

wherein the catholyte solution comprises a complexed multidentate N-donor ligand as the redox catalyst.

2. 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.

3. 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.

4. 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.

5. A fuel cell according to claim 4 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.

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

7. 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.

8. A fuel cell according to claim 7 wherein the multidentate N-donor ligand comprises at least one pyridine substituent.

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

10. A fuel cell according to claim 9 wherein the multidentate ligand is complexed to a transition metal via 3 to 6 nitrogen atoms.

11. A fuel cell according to claim 10 wherein one to five of said nitrogen atoms are contained in one or more aromatic heterocycles.

12. A fuel cell according to claim 11, wherein the aromatic heterocycles are substituted aromatic heterocycles.

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

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

15. A fuel cell according to claim 14 wherein said aromatic heterocycles comprise pyridine or pyridine derivatives.

16. A fuel cell according to claim 14, wherein the aromatic heterocycles are substituted aromatic heterocycles.

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

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

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

20. A fuel cell according to claim 18, wherein the aromatic heterocycles are substituted aromatic heterocycles.

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

22. A fuel cell according to claim 21 wherein said organic groups which include at least one N donor atom are aromatic heterocycles.

23. A fuel cell according to claim 22 wherein said aromatic heterocycles comprise pyridine or pyridine derivatives.

24. A fuel cell according to claim 22, wherein the aromatic heterocycles are substituted aromatic heterocycles.

25. 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.

26. 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.

27. A fuel cell according to claim 26 wherein the catholyte is acidic.

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

29. A fuel cell according to claim 28 wherein the catholyte is alkaline.

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

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

32. The fuel cell of claim 1, wherein the redox mediator is at least partially regenerated by indirect reaction with the oxidant after reduction at the cathode.