FUEL CELLS

• US 20090325002A1
• Filed: 04/24/2007
• Published: 12/31/2009
• Est. Priority Date: 04/25/2006
• Status: Active Grant

• Current Assignee: Clean Power Limited
• Original Assignee: ACAL Energy Ltd
• Inventors: Liu, Jian-Guo, Creeth, Andrew Martin
• Granted Patent: US 8,753,783 B2
• Time in Patent Office: Days
• US Class Current: 429/495
• CPC Class Codes: H01M 8/10 Fuel cells with solid electrolytes
• CPC Class Codes: H01M 8/1009 with one of the reactants being liquid, solid or liquid-charged H01M8/12 takes precedence
• CPC Class Codes: H01M 8/1011 Direct alcohol fuel cells [DAFC], e.g. direct methanol fuel cells [DMFC]
• CPC Class Codes: H01M 8/1013 Other direct alcohol fuel cells [DAFC]
• CPC Class Codes: H01M 8/18 Regenerative fuel cells, e.g. redox flow batteries or secondary fuel cells
• CPC Class Codes: H01M 8/188 by recharging of redox couples containing fluids; Redox flow type batteries
• 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

Abstract

The invention provides a fuel cell comprising an anode in an anode region of the cell and a cathode in a cathode region of the cell, the anode being separated from the cathode by an ion selective polymer electrolyte membrane, the anode region of the cell being supplied in use thereof with an alcoholic fuel, the cathode region of the cell being supplied in use thereof with an oxidant, the cell being provided with means for generating an electrical circuit between the anode and the cathode and with a non-volatile redox couple in solution in flowing fluid communication with the cathode in the cathode region of the cell, the redox couple being at least partially reduced at the cathode in operation of the cell, and at least partially re-generated by reaction with the oxidant after such reduction at the cathode, the redox couple and/or the concentration of the redox couple in the catholyte solution being selected so that the current density generated by the cell in operation is substantially unaffected by the crossover of the alcoholic fuel from the anode region of the cell to the cathode region of the cell across the polymer electrolyte membrane.

Claims

1. A fuel cell comprising:

an anode in an anode region of the cell and a cathode in a cathode region of the cell, the anode being separated from the cathode by an ion selective polymer electrolyte membrane, the anode region of the cell being supplied in use thereof with an alcoholic fuel and the cathode region of the cell being supplied in use thereof with an oxidant;

an electrical circuit between the anode and the cathode; and

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

wherein at least one of the redox couple and the concentration of the redox couple in the catholyte solution is selected so that the current density generated by the cell in operation is substantially unaffected by the oxidation of alcoholic fuel due to crossover of the alcoholic fuel from the anode region of the cell to the cathode region of the cell across the polymer electrolyte membrane.

2. A fuel cell according to claim 1 wherein the alcoholic fuel comprises at least one low molecular weight alcohol.

3. A fuel cell according to claim 2 wherein the alcoholic fuel is selected from the group consisting of methanol, ethanol, propanol, isopropanol, butanol, dipropylene glycol, ethylene glycol, and mixtures of two or more thereof.

4. A fuel cell according to claim 1 wherein the redox potential of the redox couple is about 0.01V to 0.3V different from the potential of oxygen.

5. A fuel cell according to claim 1 wherein the operating temperature of the fuel cell is below about 100°

C.

6. A fuel cell according to claim 1 wherein the redox couple comprises at least one transition metal complex.

7. A fuel cell according to claim 6 wherein the redox couple comprises a polyoxometallate species.

8. A fuel cell according to claim 1 wherein the concentration of the redox couple in the catholyte solution is at least about 0.1 M.

9. A fuel cell according to claim 1 wherein the cathode region of the cell is provided with a reservoir for storing the catholyte solution.

10. A fuel cell according to claim 1 wherein the fuel cell comprises a switchable electronic valve that allows reverse flow of electrons along the circuit when electromotive force is supplied to the fuel cell.

11. A fuel cell according to claim 7 wherein the polyoxometallate is represented by the formula:

X_a[Z_bM_cO_d]

wherein;

X is selected from the group consisting of;

hydrogen, alkali metals, alkaline earth metals, and ammonium, and combinations of two or more thereof;

Z is selected from the group consisting of;

B, P, S, As, Si, Ge, Ni, Rh, Sn, Al, Cu, I, Br, F, Fe, Co, Cr, Zn, H₂, Te, Mn and Se, and combinations of two or more thereof,

M is a metal selected from the group consisting of;

Mo, W, V, Nb, Ta, Mn, Fe, Co, Cr, Ni, Zn, Rh, Ru, Tl, Al, Ga, In, metals selected from the 1st, 2nd and 3rd transition metal series, and the lanthanide series, and combinations of two or more thereof;

a is a number of X necessary to charge balance the [M_cO_d] anion;

b is from 0 to 20;

c is from 1 to 40; and

d is from 1 to 180.

12. A fuel cell according to claim 11 wherein b is from 0 to 2.

13. A fuel cell according to claim 11 wherein M is selected from the group consisting of:

vanadium, molybdenum, and combinations thereof.

14. A fuel cell according to claim 11 wherein Z is phosphorus.

15. A fuel cell according to claim 11 wherein X comprises a combination of hydrogen with alkali metal ions and/or alkaline earth metal ions.

16. A fuel cell according to claim 15, wherein X comprises hydrogen and sodium.

17. A fuel cell according to claim 7 wherein the polyoxometallate comprises one of molybdophosphoric acid (H₃PMo₁₂O₄₀) and molybdovanadophosphoric acid (H₅PMo₁₀V₂O₄₀).

18. A fuel cell according to claim 1 wherein the current density generated by the cell in operation varies by less than 10% upon oxidation of the alcoholic fuel due to crossover.

19. A method of generating electricity by the fuel cell of claim 1, comprising:

supplying the alcoholic fuel to the anode region;

supplying the oxidant to the cathode region; and

generating electricity through the electrical circuit between the anode and the cathode.