ALKALINE MEMBRANE FUEL CELLS AND APPARATUS AND METHODS FOR SUPPLYING WATER THERETO

• US 20100021777A1
• Filed: 06/03/2009
• Published: 01/28/2010
• Est. Priority Date: 06/04/2008
• Status: Active Grant

• Current Assignee: Hydrolite Limited
• Original Assignee: Cellera, Inc.
• Inventors: Gottesfeld, Simshon, Dekel, Dario, Gottesfeld, Ziv, Simakov, Stanislav David
• Granted Patent: US 7,943,258 B2
• Time in Patent Office: Days
• US Class Current: 429/429
• CPC Class Codes: H01M 4/8605 Porous electrodes
• CPC Class Codes: H01M 4/8807 Gas diffusion layers
• CPC Class Codes: H01M 4/881 Electrolytic membranes
• CPC Class Codes: H01M 4/8825 Methods for deposition of the catalytic active composition
• CPC Class Codes: H01M 4/8853 Electrodeposition
• CPC Class Codes: H01M 4/886 Powder spraying, e.g. wet or dry powder spraying, plasma spraying
• CPC Class Codes: H01M 4/8871 Sputtering
• CPC Class Codes: H01M 4/8892 Impregnation or coating of the catalyst layer, e.g. by an ionomer
• CPC Class Codes: H01M 8/023 Porous and characterised by the material
• CPC Class Codes: H01M 8/0289 Means for holding the electrolyte solid polymer electrolytes H01M8/1018
• CPC Class Codes: H01M 8/083 Alkaline fuel cells
• CPC Class Codes: H01M 8/103 having nitrogen, e.g. sulfonated polybenzimidazoles [S-PBI], polybenzimidazoles with phosphoric acid, sulfonated polyamides [S-PA] or sulfonated polyphosphazenes [S-PPh]
• CPC Class Codes: H01M 8/106 characterised by the chemical composition of the porous support
• CPC Class Codes: H01M 8/1062 characterised by the physical properties of the porous support, e.g. its porosity or thickness
• CPC Class Codes: H01M 8/1067 characterised by their physical properties, e.g. porosity, ionic conductivity or thickness
• CPC Class Codes: H01M 8/1088 Chemical modification, e.g. sulfonation
• CPC Class Codes: H01M 8/1093 mechanical, e.g. pressing, puncturing
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product

Abstract

A device to produce electricity by a chemical reaction without the addition of liquid electrolyte comprises an anode electrode, a polymer membrane electrolyte fabricated to conduct hydroxyl (OH—) ions, the membrane being in physical contact with the anode electrode on a first side of the membrane, and a cathode electrode in physical contact with a second side of the membrane. The anode electrode and cathode electrode contain catalysts, and the catalysts are constructed substantially entirely from non-precious metal catalysts. Water may be transferred to the cathode side of the membrane from an external source of water.

Claims

1. A device to produce electricity by a chemical reaction without the addition of liquid electrolytes, the device comprising:

an anode electrode;

a polymer membrane electrolyte configured to conduct hydroxyl (OH—

) ions, the membrane being in physical contact with the anode electrode on a first side of the membrane; and

a cathode electrode in physical contact with a second opposite side of the membrane;

wherein the anode electrode and cathode electrode contain catalysts, the catalysts being constructed substantially entirely from non-precious metal catalysts.

2. The device of claim 1 where the membrane thickness is under about 30 micrometers.

3. The device of claim 1 wherein the anode electrode and cathode electrode are prepared using a solution of substantially the same polymer from which the membrane is made.

4. The device of claim 3 wherein the volume concentration of the alkali hydroxyl (OH—

) ions in the polymer within the electrodes is at least about 5% higher than that of OH—

ion volume concentration in the membrane.

5. The device of claim 1 wherein the anode electrode and cathode electrode are prepared from a recast hydroxyl (OH—

) ion conducting polymer of chemical composition different from which the membrane is made.

6. The device of claim 1 further comprising at least one catalyst layer adjacent to the membrane configured with a mixture of non-precious catalyst and polymer solution on a support chosen from the group consisting of woven carbon, non-woven carbon, metal mesh, and metal foam.

7. The device of claim 1 further comprising at least one catalyst layer configured with a mixture of non-precious catalyst and polymer solution and disposed directly on the membrane to form a catalyst coated membrane (“

CCM”

).

8. The device of claim 7 wherein the CCM is prepared by:

(a) direct air-spraying of a catalyst ink onto one side of the OH—

ion conducting membrane placed on a heated vacuum table; and

(b) direct air-spraying of the catalyst ink on the opposite side of the membrane.

9. The CCM described in claim 8 wherein the overall thickness of the catalyst layer is less than about 5 micrometers.

10. The CCM described in claim 8 wherein the catalyst ink is made by vigorous mixing of a metal or carbon supported non-precious catalyst with a solution of ionomer in water/alcohol mixture.

11. The device of claim 1 further comprising at least one non-precious catalyst layer configured by impregnating the catalyst layer with a polymer solution.

12. The device of claim 1 wherein at least one electrode further comprises a front layer of high volume concentration of non-precious metal catalyst in physical contact with a side of the membrane and is configured by the technique chosen from the group consisting of sputtering, e-beaming, and direct electro-less deposition.

13. The device of claim 1 wherein the membrane further comprises a concentrated front layer of non-precious metal catalyst on at least one side of the membrane and is in physical contact with an electrode and is configured by the technique chosen from the group consisting of sputtering, e-beaming, and direct electro-less deposition.

14. The device of claim 1 wherein at least one electrode further comprises a layer of an array of catalyst-coated micro-dendrites embedded into the membrane.

21. The cell of claim 1 wherein initial activation of the cell achieved by setting the cell voltage at about or near 50 mV and keeping it at this voltage until the cell current plateaus while the cell temperature reaches a design operation point.

22. The cell activation described in claim 21 wherein the current plateaus near 1 A/cm² and the cell temperature design point is between 60 and 70 degrees Celsius.

35. A fuel cell stack built by stacking a plurality of cells of the type recited in the device of claim 1 wherein bipolar plates separating adjacent cells are constructed of machined aluminum coated by a film of nickel applied by electroless plating.

36. The device of claim 35 wherein the aluminum plate metal is a type 6061 material.

37. The device of claim 35 wherein the nickel coat thickness is greater than about 1 micrometer, preferably about 25 micrometers.

15. An alkaline membrane fuel cell, the fuel cell comprising:

an anode electrode;

a polymer membrane electrolyte configured to conduct hydroxyl (OH—

) ions, the membrane being in physical contact with the anode electrode on a first side of the membrane; and

a cathode electrode in physical contact with a second opposite side of the membrane;

wherein the fuel cell is configured and disposed with a dead end anode chamber and is configured to transfer water from the anode electrode through the membrane to the cathode electrode at a rate substantially equivalent to water generation at the anode electrode.

16. The fuel cell in claim 15 wherein water transport across the membrane is facilitated by a highly hydrophilic membrane or mesh shaped and placed as a frame around the active area on both the anode and cathode sides.

17. The fuel cell of claim 15, further comprising a mixed hydrophilic/hydrophobic layer proximate to the anode electrode.

18. The fuel cell of claim 15, further comprising a hydrophobic layer proximate to the cathode electrode.

19. The fuel cell of claim 18 operating in air breathing mode, further comprising a gas diffusion layer proximate to the hydrophobic layer and an adjustable shutter proximate to the gas diffusion layer.

20. The fuel cell of claim 18 operating in air breathing mode with the cathode GDL thickness and porosity designed for a water vapor release matching a selected cell current and inner temperature according to the equation:

P*_H2O,Tcell=0.4 [J_cell/J_lim,cath] atm., where P*_H2O,Tcell is the water vapor pressure at the inner cell temperature and J_lim,cath is the limiting current set by the max. transport rate of oxygen from air through the GDL.

23. The fuel cell of claim 15, wherein the dead-end anode further comprises includes a one-way valve, the one-way valve opening periodically to the ambient by normal pressure to periodically purge water buildup.

24. An alkaline membrane fuel cell, the fuel cell comprising:

an anode electrode;

a polymer membrane electrolyte configured to conduct hydroxyl (OH—

) ions, the membrane being in physical contact with the anode electrode on a first side of the membrane;

a cathode electrode in physical contact with the second opposite side of the membrane;

the anode electrode and the cathode electrode each containing catalysts, the catalysts being constructed substantially entirely from non-porous metal catalysts; and

an external source of water;

wherein the fuel cell is configured to transfer water to the cathode side of the membrane from the external source of water.

25. The fuel cell of claim 24 wherein direct supply of liquid water to the cathode side of the membrane is provided by means of a water channel about 1 millimeter wide surrounding the active area of the fuel cell.

26. The direct liquid water supply in claim 25 with water transfer from the water channel to and along the membrane surface facilitated by a wicking mesh incorporated as part of the membrane, preferably on the side adjacent the cathode catalyst.

27. The wicking mesh in claim 25 where the wicking mesh is incorporated to become an integral part of the membrane by placing it along the major surface of the membrane during membrane casting.

28. The wicking mesh in claim 25 where the wicking mesh is attached onto the surface of a pre-fabricated membrane by using a solution of an ionomer to fill the spaces in the mesh and to provide a bonding function following subsequent ionomer recasting.

29. The fuel cell of claim 24 where liquid water supply to the cathode side of the membrane is provided from a stationary reservoir of liquid water with the water wicked from such reservoir into and along the cathode side of the membrane.

30. A method of operating the fuel cell recited in claim 24, the steps comprising:

(a) providing water to hydrate the fuel cell membrane to increase the ionic conductivity of the membrane;

(b) dialing a low voltage across the cell while providing fuel and airflow to the cell for a predetermined amount of time;

(c) dialing a load for testing power output of the cell;

(d) checking cell voltage;

(e) if the cell voltage is stable, continuing to operate the fuel cell at that voltage;

(f) if the cell voltage is not stable, providing additional water volume to the cell; and

(g) after step (f), rechecking cell voltage and if cell voltage rises in response to the addition of water in step (f), continue adding water at an optimal rate to the cell until the cell provides power to be operable.

31. An alkaline membrane fuel cell comprising:

an anode electrode;

a polymer membrane electrolyte configured to conduct hydroxyl (OH—

) ions, the membrane being in physical contact with the anode electrode on a first side of the membrane;

a cathode electrode in physical contact with a second opposite side of the membrane;

wherein the fuel cell is configured and designed to transfer water from the anode electrode through the membrane to the cathode electrode;

further comprising a water exchanger operatively connected with the fuel cell and disposed to exchange water from the cathode electrode exhaust stream to the cathode electrode inlet stream.

32. The device of claim 31 wherein the water exchanger includes a membrane, the membrane being of high water permeability and low gas permeability to enable transport of water from the humidified cathode electrode exhaust stream to an inlet stream of dry air.

33. An alkaline membrane fuel cell comprising:

an anode electrode;

a polymer membrane electrolyte configured to conduct hydroxyl (OH—

) ions, the membrane being in physical contact with the anode electrode on a first side of the membrane;

a cathode electrode in physical contact with a second opposite side of the membrane;

wherein the fuel cell is configured and designed to transfer water from the anode electrode through the membrane to the cathode electrode; and

further comprising a water exchanger operatively connected with the fuel cell and disposed to transfer water from the cathode electrode exhaust stream to the inlet stream of dry air.

34. The device of claim 33 wherein the water exchanger includes a membrane, the membrane being of high water permeability and low gas permeability to enable transport of water from the humidified anode electrode exhaust stream to an inlet stream of dry air.