Nanowire structures comprising carbon

• US 20080280169A1
• Filed: 06/12/2007
• Published: 11/13/2008
• Est. Priority Date: 12/09/2004
• Status: Active Grant

• Current Assignee: ONED Material Incorporated
• Original Assignee: Nanosys Incorporated (Shoei Electronic Materials, Inc.)
• Inventors: Niu, Chunming, Qian, Baixin, Stefan, Ionel
• Granted Patent: US 7,842,432 B2
• Time in Patent Office: Days
• US Class Current: 429/13
• CPC Class Codes: H01B 1/04 mainly consisting of carbon-silicon compounds, carbon or silicon
• CPC Class Codes: H01M 4/133 Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
• CPC Class Codes: H01M 4/8605 Porous electrodes
• CPC Class Codes: H01M 4/8657 layered
• CPC Class Codes: H01M 4/8807 Gas diffusion layers
• CPC Class Codes: H01M 4/9016 Oxides, hydroxides or oxygenated metallic salts
• CPC Class Codes: H01M 4/92 Metals of platinum group H01M4/94 , H01M4/9058 take precedence
• CPC Class Codes: H01M 4/926 on carbon or graphite
• CPC Class Codes: H01M 8/0234 Carbonaceous material
• CPC Class Codes: H01M 8/0241 Composites
• CPC Class Codes: H01M 8/04194 Concentration measuring cells
• CPC Class Codes: H01M 8/1007 with both reactants being gaseous or vaporised H01M8/12 takes precedence
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02E 60/50 Fuel cells
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product

Abstract

The present invention is directed to nanowire structures and interconnected nanowire networks comprising such structures, as well as methods for their production. The nanowire structures comprise a nanowire core, a carbon-based layer, and in additional embodiments, carbon-based structures such as nanographitic plates consisting of graphenes formed on the nanowire cores, interconnecting the nanowire structures in the networks. The networks are porous structures that can be formed into membranes or particles. The nanowire structures and the networks formed using them are useful in catalyst and electrode applications, including fuel cells, as well as field emission devices, support substrates and chromatographic applications.

Claims

1. A method for controlling fuel concentration at a proton exchange membrane of a fuel cell, the method comprising providing a diffusion-controlling barrier comprising a network of interconnected nanowires between an anode of the fuel cell and a fuel source.

2. The method of claim 1, further comprising providing a coating comprising poly(tetrafluoroethylene) or silicone.

3. The method of claim 1, wherein the providing the network of interconnected nanowires comprises spraying nanowires having a pre-determined length.

4. The method of claim 1, wherein the providing the network of interconnected nanowires provides a fuel concentration at the proton exchange membrane that is less than about 30% of the fuel concentration at the fuel source.

5. A fuel cell comprising a fuel source, a proton exchange membrane, an anode electrode, a cathode electrode and a diffusion-controlling barrier comprising an interconnected network of nanowires, wherein fuel concentration at the proton exchange membrane is less than about 30% of that of the fuel source.

6. The fuel cell of claim 5, wherein the diffusion-controlling barrier further comprises poly(tetrafluoroethylene) or silicone.

7. A fuel cell gas diffusion layer comprising an interconnected network of nanowires.

8. The fuel cell gas diffusion layer of claim 7, wherein the nanowires comprise a core and a carbon-based structure formed on the core.

9. The fuel cell gas diffusion layer of claim 8, wherein the carbon-based structure comprises at least one nanographitic plate formed on the interfacial carbide layer.

10. The fuel cell gas diffusion layer of claim 8, wherein the core comprises semiconductor material.

11. The fuel cell gas diffusion layer of claim 10, wherein the semiconductor material is selected from the group consisting of Si, B, SiC and GaN.

12. The fuel cell gas diffusion layer of claim 8, wherein the core comprises an inorganic oxide selected from the group consisting of SiO₂, Al₂O₃, TiO₂, SnO₂, ZrO₂, HfO₂ and Ta₂O₅;

an inorganic carbide selected from the group consisting of TiC, ZrC, HfC, NbC, WC, W₂C, MoC and Mo₂C;

or an inorganic nitride selected from the group consisting of TiN, ZrN, HfN, WN, MoN and BN.

13. The fuel cell gas diffusion layer of claim 8, wherein each core has a cross-sectional diameter of less than about 500 nm and a length of greater than about 50 nm.

14. The fuel cell gas diffusion layer of claim 8, wherein the at least one nanographitic plate extends away from each core a distance of about 1 nm to about 100 nm, comprises at least 2-15 layers of graphene, and is oriented relative the major axis of the core at an angle of between about 0°

and about 90°

.

15. A method of preparing a fuel cell gas diffusion layer comprising disposing an interconnected network of nanowires on a substrate.

16. The method of claim 15, wherein the disposing comprises disposing the interconnected network of nanowires on carbon paper, or a graphite substrate.

17. The method of claim 16, wherein the disposing comprises spraying the interconnected network of nanowires on the substrate.

18. The method of claim 16, wherein the disposing comprises spraying the interconnected network of nanowires on a substrate comprising an interconnected network of nanowires with active catalytic nanoparticles dispersed thereon.

19. A method for preparing a fuel cell membrane electrode assembly, comprising:

(a) disposing a gas diffusion layer comprising one or more nanowires;

(b) disposing a first composition of catalyst metal-associated nanowires adjacent the gas diffusion layer;

(c) disposing a membrane adjacent the first catalyst metal-associated nanowire composition; and

(d) disposing a second composition of catalyst metal-associated nanowires adjacent the membrane.

20-30. -30. (canceled)

31. A membrane electrode assembly prepared by a process comprising:

(a) disposing a first gas diffusion layer comprising one or more nanowires;

(b) disposing a first composition of catalyst metal-associated nanowires adjacent the first gas diffusion layer;

(c) disposing a membrane adjacent the first catalyst metal-associated nanowire composition;

(d) disposing a second composition of catalyst metal-associated nanowires adjacent the membrane; and

(e) disposing a second gas diffusion layer comprising one or more nanowires adjacent the second composition of catalyst metal-associated nanowires, thereby forming the membrane electrode assembly.

32. A fuel cell prepared by a process comprising:

(a) disposing a first gas diffusion layer comprising one or more nanowires on a first end plate;

(b) disposing a first composition of catalyst metal-associated nanowires adjacent the first gas diffusion layer;

(c) disposing a membrane adjacent the first catalyst metal-associated nanowire composition;

(d) disposing a second composition of catalyst metal-associated nanowires adjacent the membrane;

(e) disposing a second gas diffusion layer comprising one or more nanowires adjacent the second composition of catalyst metal-associated nanowires;

(f) disposing a bipolar plate adjacent the second gas diffusion layer; and

(g) repeating (a)-(f) until a desired number of compositions of catalyst metal-associated nanowires have been disposed, wherein a last bipolar plate is replaced with a second end plate, thereby generating the fuel cell.

33-34. -34. (canceled)

35. A fuel cell membrane electrode assembly, comprising:

(a) a first gas diffusion layer comprising one or more nanowires;

(b) a first composition of catalyst metal-associated nanowires and ionomer adjacent the gas diffusion layer;

(c) a proton-conducing membrane layer adjacent the first catalyst metal-associated nanowire composition;

(d) a second composition of catalyst metal-associated nanowires and ionomer adjacent the proton-conducting membrane layer; and

(e) a second gas diffusion layer comprising one or more nanowires adjacent the second catalyst metal-associated nanowire composition,

wherein an ionomer concentration gradient is present in the first and second compositions of catalyst-metal associated nanowires such that ionomer concentration is greatest adjacent the proton-conducting membrane layer.

36-42. -42. (canceled)

43. A method of disposing a composition comprising metal catalyst-associated nanowires and ionomer on a substrate, the method comprising:

dispersing the nanowires and the ionomer in a mixture of two or more solvents to form a dispersion; and

disposing the dispersion on the substrate.

44-54. -54. (canceled)