Multilayer structure incorporating a mat of carbon nanotubes as diffusion layer in a PEMFC

Patent metadata

Field	Value
Publication number	US-11271220-B2
Application number	US-201816165277-A
Country	US
Kind code	B2
Filing date	Oct 19, 2018
Priority date	Oct 20, 2017
Publication date	Mar 8, 2022
Grant date	Mar 8, 2022

Abstract

A multilayer structure, of use as composite diffusion layer in a proton-exchange membrane fuel cell, including at least one mat of carbon nanotubes having a unit diameter of less than or equal to 20 nm, defining at least one face of the structure, the mat of carbon nanotubes being superposed on a support based on carbon fibres. It also relates to a process for preparing such a multilayer structure and to the use thereof for an electrode of a PEMFC.

First claim

The invention claimed is:

1. A multilayer structure, of use as composite diffusion layer in a proton-exchange membrane fuel cell, comprising at least one mat of carbon nanotubes having a unit diameter of less than or equal to 20 nm, defining at least one face of said structure, said mat of carbon nanotubes being superposed on a support based on carbon fibres, wherein the support based on carbon fibres is impregnated over part of its volume by at least one hydrophobic agent, and/or a face of the support opposite the CNT mat is hydrophobic or coated with a film incorporating at least one hydrophobic agent,
wherein the interface between the support based on carbon fibres and the mat of carbon nanotubes which is superposed thereon comprises a stack of thin layers comprising, in this order, from the support up to the mat of nanotubes:
a/optionally a metal layer made of metal M or layer made of metal alloy based on the metal M or layer made of graphene;
b/a titanium layer;
c/an aluminium layer;
d/a layer of material(s) that catalyse(s) the growth of carbon nanotubes.

2. The multilayer structure according to claim 1 , wherein the CNT mat has a density greater than or equal to 10 11 CNT per cm 2 .

3. The multilayer structure according to claim 1 , wherein the CNT mat has a density between 10 11 and 10 13 CNT per cm 2 .

4. The multilayer structure according to claim 1 , wherein the CNT mat has a thickness between 1 and 200 μm.

5. The multilayer structure according to claim 1 , wherein the CNT mat has a thickness between 5 and 100 μm.

6. The multilayer structure according to claim 1 , wherein the CNT mat has a thickness between 5 and 50 μm.

7. The multilayer structure according to claim 1 , wherein the support based on carbon fibres is impregnated over part of its volume by at least one hydrophobic agent, and/or has, on the face of the support opposite the CNT mat, a film incorporating at least one hydrophobic agent.

8. The multilayer structure according to claim 1 , wherein said hydrophobic agent is selected from fluoropolymers and perfluoropolymers.

9. The multilayer structure according to claim 1 , wherein said hydrophobic agent is selected from poly(vinylidene fluoride), polytetrafluoroethylene, fluorinated ethylene propylene, poly(vinylidene fluoride-co-hexafluoropropylene), poly(ethylene-co-tetrafluoroethylene) and perfluoroalkoxy.

10. The multilayer structure according to claim 1 , comprising two CNT mats defining two opposite faces of said structure.

11. The multilayer structure according to claim 1 , wherein the support based on carbon fibres comprises:
a substrate based on carbon fibres; and
a layer based on carbon fibres on at least one of the faces of said substrate, comprising less than 30% by weight of hydrophobic agent;
said layer having, on at least the face opposite said substrate, said mat of carbon nanotubes,
wherein the substrate based on carbon fibres is hydrophobic.

12. The multilayer structure according to claim 11 , wherein the substrate based on carbon fibres is impregnated by at least one hydrophobic agent.

13. The multilayer structure according to claim 11 , wherein said substrate has between 2% and 40% by weight of hydrophobic agent(s), relative to its total weight.

14. The multilayer structure according to claim 11 , wherein the layer based on carbon fibres comprises less than 10% by weight of hydrophobic agent.

15. The multilayer structure according to claim 11 , wherein the substrate is intercalated between two layers based on carbon fibres, comprising less than 30% by weight of hydrophobic agent, each of the layers having, on its face opposite said substrate, a CNT mat.

16. The multilayer structure according to claim 11 , further comprising a mat of carbon nanotubes intercalated between at least one layer based on carbon fibres and said substrate.

17. The multilayer structure according to claim 11 , wherein the layer based on carbon fibres borne by at least one of the faces of said substrate, comprises less than 10% by weight of hydrophobic agent.

18. The multilayer structure according to claim 11 , wherein the layer based on carbon fibres borne by at least one of the faces of said substrate is free of hydrophobic agent.

19. The multilayer structure according to claim 1 , wherein the support based on carbon fibres is formed of a solid substrate based on carbon fibres, said solid substrate having, on one of its faces, said mat of carbon nanotubes, wherein said substrate is impregnated, on the face opposite the CNT mat, by at least one hydrophobic agent, and/or the face opposite the CNT mat is hydrophobic or coated with a film comprising at least one hydrophobic agent.

20. The multilayer structure according to claim 19 , having on each of the two opposite faces of said substrate, a mat of carbon nanotubes.

21. The multilayer structure according to claim 19 , wherein said substrate is impregnated, on the face opposite the CNT mat, by at least one hydrophobic agent, and/or has, on the face opposite the CNT mat a film comprising at least one hydrophobic agent.

22. The multilayer structure according to claim 19 , wherein the substrate is impregnated over a thickness, e, extending from the face opposite the CNT mat, that is less than the total thickness of the substrate.

23. The multilayer structure according to claim 19 , wherein the substrate is impregnated over a thickness e representing less than 95% of the total thickness of the substrate.

24. The multilayer structure according to claim 19 , wherein the substrate is impregnated over a thickness e representing less than 80% of the total thickness of the substrate.

25. An electrode for a proton-exchange membrane fuel cell, comprising a multilayer structure as defined according to claim 1 , at least one CNT mat of said structure being positioned in contact with the active layer of the electrode.

26. A proton-exchange membrane fuel cell comprising at least one electrode comprising a multilayer structure as defined according to claim 1 , at least one CNT mat of said structure being positioned in contact with the active layer of the electrode.

27. A process for preparing a multilayer structure, of use as composite diffusion layer in a proton-exchange membrane fuel cell, comprising at least the following steps:
(i) producing, on at least one of the faces of a support based on carbon fibres, comprising less than 30% by weight of hydrophobic agent, a catalytic stack of thin layers, comprising in this order:
a/ optionally a metal layer made of metal M or layer made of metal alloy based on the metal M or layer made of graphene;
b/ a titanium layer;
c/ an aluminium layer;
d/ a layer of material(s) that catalyse(s) the growth of carbon nanotubes; and
(ii) growing a mat of carbon nanotubes on the stack according to a chemical vapour deposition technique, which is optionally plasma enhanced, and optionally hot-filament activated.

28. The process according to claim 27 , wherein said support based on carbon fibres is submitted, prior to its use in step (i), to a heat treatment at a temperature of between 500° C. and 700° C., under an atmosphere of inert gas(es), air, hydrogen, oxygen, or a mixture of these gases.

29. The process according to claim 27 , comprising at least the following steps:
(a1) producing, according to steps (i) and (ii), a CNT mat on at least one of

Assignees

• Commissariat Energie Atomique

Inventors

• Morin Arnaud
• Dijon Jean
• Ramos Raphael

Classifications

• H01M4/8657

  layered · CPC title

• H01M8/0234

  Carbonaceous material · CPC title

• H01M4/8875

  Methods for shaping the electrode into free-standing bodies, like sheets, films or grids, e.g. moulding, hot-pressing, casting without support, extrusion without support · CPC title

• H01M4/8626

  characterised by the form · CPC title

• H01M4/96 Primary

  Carbon-based electrodes · CPC title