Redox fuel cell with catholyte redox mediator

• US 8,951,695 B2
• Filed: 01/23/2009
• Issued: 02/10/2015
• Est. Priority Date: 01/23/2008
• Status: Expired due to Fees

• Current Assignee: Clean Power Limited
• Original Assignee: ACAL Energy Ltd
• Inventors: Knuckey, Kathryn, Rochester, David
• Primary Examiner(s): Ryan, Patrick
• Assistant Examiner(s): O Donnell, Lucas J
• Application Number:
  US12/864,359
• Publication Number:
  US 20110091746A1
• Time in Patent Office: 2,209 Days
• Field of Search: 429/7, 429/101
• US Class Current: 429/498
• CPC Class Codes: H01M 2008/1095 Fuel cells with polymeric electrolytes
• CPC Class Codes: H01M 8/188 by recharging of redox couples containing fluids; Redox flow type batteries
• CPC Class Codes: Y02E 60/50 Fuel cells

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 the multi-dentate N-donor ligand comprising at least one heterocyclic substituent selected from pyrrole, imidazole, 1,2,3-triazole, 1,2,4-triazole, pyrazole, pyridazine, pyrimidine, pyrazine, indole, tetrazole, quinoline, isoquinoline and from alkyl, alkenyl, aryl, cycloalkyl, alkaryl, alkenaryl, aralkyl, aralkenyl groups substituted with one or more of the aforesaid heterocyclic groups.

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 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, the catholyte solution further comprising a complexed multidentate N-donor ligand as at least one of said redox mediator and as a redox catalyst catalysing the regeneration of the said mediator, the multi-dentate N-donor ligand comprises at least one heterocyclic substituent selected from pyrrole, imidazole, 1,2,3-triazole, 1,2,4-triazole, pyrazole, pyridazine, pyrimidine, pyrazine, indole, tetrazole, quinoline, isoquinoline and from alkyl, alkenyl, aryl, cycloalkyl, alkaryl, alkenaryl, aralkyl, aralkenyl groups substituted with one or more of the aforesaid heterocyclic groups,

wherein the multidentate N-donor ligand comprises a non-polymeric molecule containing up to 8 nitrogen atoms capable of coordinating to a transition metal centre.

2. A redox fuel cell according to claim 1 wherein the ligand may coordinate through each or any of the nitrogen atoms.

3. A redox fuel cell according to claim 1 wherein the multidentate N-donor ligand comprises from three to six nitrogen atoms capable of coordinating to a transition metal centre.

4. A redox fuel cell according to claim 3 wherein the N-donor ligand comprises from four to six nitrogen atoms capable of coordinating to a transition metal centre.

5. A redox fuel cell according to claim 4 wherein the N-donor ligand comprises five or six nitrogen atoms capable of coordinating to a transition metal centre.

6. A redox fuel cell according to claim 1 wherein the heterocyclic substituent comprises one or more substituent functional groups thereon, at any position or positions on the ring.

7. A redox fuel cell according to claim 6 wherein the substituent group is selected from alkyl, aryl, alkenyl, alkynyl, amine, protonated amine, quaternary amine, sulfate, sulfonate, sulfonic acid, phosphate, phosphonate, phosphonic acid, carboxylate, carboxylic acid, halides and combinations of two or more thereof on the same or on different positions on the ring.

8. A redox fuel cell according to claim 7 wherein each substituent group is spaced from the heterocyclic substituent by one or more spacer elements.

9. A redox fuel cell according to claim 8 wherein the or each spacer element is selected from straight or branched chain alkyl, alkenyl, aryl, cycloalkyl, alkaryl, aralkyl, aralkenyl and combinations of two or more thereof.

10. A redox fuel cell according to claim 1 wherein the N-donor ligand comprises the structure:

11. A redox fuel cell according to claim 10 wherein a, b and c are independently any integer from 1 to 3.

12. A redox fuel cell according to claim 10 wherein one or more of A, B and C are independently substituted with one or more substituent functional groups at any position or positions on the ring.

13. A redox fuel cell according to claim 12 wherein the or each substituent group is independently selected from alkyl, aryl, alkenyl, alkynyl, amine, protonated amine, quaternary amine, sulfate, sulfonate, sulfonate, sulfonic acid, sulfonic acid, phosphate, phosphonate, phosphonic acid, carboxylate, carboxylic acid and/or halides.

14. A redox fuel cell according to claim 10 wherein the N-donor ligand is selected from:

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

16. A redox fuel cell according to claim 15 wherein any one or more of R¹ to R⁵ is substituted with one or more substituent functional groups at any position or positions on the ring.

17. A redox fuel cell according to claim 16 wherein the or each substituent groups is independently selected from straight or branched chain alkyl, aryl, alkenyl, alkynyl, amine, protonated amine, quaternary amine, sulfate, sulfonate, sulfonic acid, phosphate, phosphonate, phosphonic acid, carboxylate, carboxylic acid, and halides and combinations of two or more thereof.

18. A redox fuel cell according to claim 16 wherein each substituent group is spaced from the heterocycle by any number of suitable spacer elements.

19. A redox fuel cell according to claim 18 wherein the or each spacer element is independently selected from optionally substituted straight or branched chain, alkyl, alkenyl, aryl, cycloalkyl, alkaryl, aralkyl, aralkenyl or combinations of two or more thereof.

20. A redox fuel cell according to claim 15 wherein the N-donor ligand is selected from:

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

22. A redox fuel cell according to claim 21 wherein the heterocycle contains any number of substituent functional groups at any position or positions on the ring.

23. A redox fuel cell according to claim 22 wherein the or each substituent group is independently selected from straight or branched chain alkyl, aryl, alkenyl, alkynyl, amine, protonated amine, quaternary amine, sulfate, sulfonate, sulfonic acid, phosphate, phosphonate, phosphonic acid, carboxylate, carboxylic acid, halides and combinations of one or more thereof.

24. A redox fuel cell according to claim 23 wherein each substituent group is spaced from the heterocycle by any number of suitable spacer elements.

25. A redox fuel cell according to claim 24 wherein the or each spacer element is independently selected from optionally substituted straight or branched chain alkyl, alkenyl, aryl, cycloalkyl, alkaryl, aralkyl or aralkenyl.

26. A redox fuel cell according to claim 21 wherein the N-donor ligand is selected from:

27. A redox 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.

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

29. A redox fuel cell according to claim 1 wherein the catholyte solution comprises the complexed multidentate N-donor ligand as redox mediator and a further material as redox catalyst.

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

31. A redox fuel cell according to claim 30 wherein the resulting oxidised redox catalyst is effective at least partially to oxidise the mediator to regenerate the mediator after its reduction at the cathode.

32. A redox fuel cell according to any one of claim 1 wherein the catholyte solution is an aqueous solution.

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

34. A redox fuel cell according to claim 33 wherein the multidentate N-donor ligand comprises one or more N-donor atoms which do not coordinate with the transition metal.

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

36. A redox fuel cell according to claim 35 wherein the catholyte is acidic.

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

38. A redox fuel cell according to claim 37 wherein the catholyte is alkaline.

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

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

41. The redox fuel cell according to claim 15, wherein from three to five of the R¹ to R⁵ groups comprise organic groups containing an N donor atom, and three to five of those N donor atoms belong to one or more of said optionally substituted heterocycles.

42. The redox fuel cell according to claim 21, wherein n is any integer from 1 to 5.

43. The redox fuel cell according to claim 21, wherein n is any integer from 1 to 3.

44. The redox fuel cell according to claim 21, wherein n is any integer from 1 to 3.

45. The redox fuel cell according to claim 21, wherein two to four of R¹ to R⁴ are organic groups containing an N donor atom from three to four of those N-donor atoms belonging to said optionally substituted heterocycle.