Method for producing a composite layer, electrochemical unit and use of the composite layer

Patent metadata

Field	Value
Publication number	US-11791473-B2
Application number	US-202117408046-A
Country	US
Kind code	B2
Filing date	Aug 20, 2021
Priority date	Feb 22, 2019
Publication date	Oct 17, 2023
Grant date	Oct 17, 2023

Abstract

A method is proposed by means of which a composite layer is producible in as simple and controlled a manner as possible, and by means of which composite layers with different predetermined properties can be produced with as little expenditure as possible, and thus economically. The method includes: providing a nanofiber material, comminuting the nanofiber material while forming nanorods, providing a liquid medium, which comprises an ionomer component and a dispersant, dispersing the nanorods in the liquid medium while forming a nanorod ionomer dispersion, and applying the nanorod ionomer dispersion to a surface region of a substrate while forming a composite layer. An electrochemical unit including the composite layer is provided. The composite layer is useful in a fuel cell (hydrogen fuel cell or direct alcohol fuel cell), in a redox flow cell, in an electrolytic cell, or in an ion exchanger, and useful for anion or proton conduction.

First claim

The invention claimed is:

1. A method for producing a composite layer, wherein the method comprises:
providing a nanofiber material, wherein the nanofiber material comprises a hydrophobic polymer selected from the group consisting of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polybenzimidazole (PBI), polyolefins, polyether-etherketone (PEEK), and combinations thereof;
comminuting the nanofiber material while forming nanorods;
providing a liquid medium, which comprises an ionomer component and a dispersant;
dispersing the nanorods in the liquid medium while forming a nanorod ionomer dispersion; and
applying the nanorod ionomer dispersion to a surface region of a hydrogen fuel cell substrate while forming a composite layer as a part of said hydrogen fuel cell.

2. The method in accordance with claim 1 , wherein the nanofiber material is provided by means of an electrospinning method, wherein an injection rate is in a range from about 0.1 μl/min to about 600 μl/min and/or an acceleration voltage is in a range from about 5 kV to about 30 kV.

3. The method in accordance with claim 2 , wherein the electrospinning method is a needlefree electrospinning method.

4. The method in accordance with claim 1 , wherein the nanofiber material is provided by means of a centrifugal spinning method, wherein a rotational speed is in a range from about 10 revolutions/min to about 6000 revolutions/min.

5. The method in accordance with claim 1 , wherein the nanofiber material is provided by means of a solution blow spinning method, wherein an injection rate is in a range from about 10 μl/min to about 30 μl/min and/or a gas pressure of a carrier gas stream is in a range from about 100 kPa to about 500 kPa.

6. The method in accordance with claim 1 , wherein the nanofiber material is provided as a fibrous body, wherein the fibrous body is a tangled mesh and/or as a non-woven fabric and/or as a fiber mat.

7. The method in accordance claim 1 , wherein the nanofiber material comprises nanofibers, which have an average diameter of about 20 nm to about 3000 nm, or about 50 nm to about 700 nm.

8. The method in accordance with claim 1 , wherein the nanofiber material is sintered before the comminution or the nanorods are sintered before the dispersion.

9. The method in accordance with claim 1 , wherein the application of the nanorod ionomer dispersion comprises one or more of the following methods: drop-casting, print-coating methods, wherein the print-coating methods include doctor-blading, screen printing, slit printing, engraving, inkjet printing, and spray coating methods.

10. The method in accordance with claim 1 , wherein the nanorod ionomer dispersion is applied in a plurality of layers.

11. The method in accordance with claim 1 , wherein the nanorods are contained in the nanorod ionomer dispersion with a share of about 1% by weight to about 50% by weight based on the total weight of the dispersion.

12. The method in accordance with claim 1 , wherein the ionomer component is contained in the composite layer with a share of about 80% by weight to about 95% by weight based on the total weight of the composite layer.

13. The method in accordance with claim 1 , wherein the composite layer has a total thickness in a range from about 1 μm to about 100 μm, or a range from about 5 μm to about 25 μm or in a range from about 20 μm to about 80 μm.

14. The method in accordance with claim 1 , wherein the composite layer and/or the components thereof are crosslinked by treatment with electromagnetic radiation in the ultraviolet region and/or by of chemical methods including ionic or covalent crosslinking, and/or by thermal methods.

15. The method in accordance with claim 1 , wherein the nanofiber material, optionally in the form of a fibrous body, is functionalized before the comminution by bringing the nanofiber material into contact with and/or heating the nanofiber material in caustic soda or caustic potash or sulfuric acid or phosphoric acid or in a metal salt solution including a platinum salt solution, a rhodium salt solution, a palladium salt solution, a ruthenium salt solution, or a mixed metal salt solution, wherein the mixed metal salt solution comprises a platinum cobalt salt solution or a platinum nickel salt solution.

16. The method in accordance with claim 1 , wherein the nanofiber material is optionally provided in the form of a fibrous body, wherein the nanofiber material and/or the fibrous body comprises one or more additives, wherein in particular the one or more additives form a component of nanofibers of the nanofiber material, are applied to the nanofibers and/or are mixed with the nanofibers.

17. The method in accordance with claim 16 , wherein the one or at least one of the plurality of additives comprise functional nanoparticles in granular form and/or fiber form, wherein the functional nanoparticles in granular form and/or fiber form comprise platinum, palladium, platinum cobalt, zirconium phosphate, zeolite materials, silicon oxide, and/or one or more metal oxides, wherein the one or more metal oxides is selected from cerium oxide and transition metal oxides including titanium oxide and/or manganese oxide.

18. The method in accordance with claim 1 , wherein the nanofiber material upon comminution is acted upon with mechanical or thermal energy, and wherein the nanofiber material is comminuted by means of ultrasonic treatment and/or mechanical comminution, wherein the ultrasonic treatment and/or the mechanical comminution is conducted in a ball mill and/or in a mortar.

19. The method in accordance with claim 1 , wherein the nanofiber material comprises or is substantially formed of coated nanofibers, and wherein the nanofibers are coated with noble metal selected from the group consisting of platinum, palladium, and combinations thereof.

20. The method in accordance with claim 1 , wherein the nanorods have an aspect ratio of average length to average diameter of the nanorods of about 5 to about 25000, or about 10 to about 500, and wherein the nanorods have an average length of about 2 μm to about 500 μm, or about 5 μm to about 30 μm.

21. The method in accordance with claim 1 , wherein the liquid medium comprises one or more of the following materials: fluorinated copolymers with sulfonic acid groups, in particular Nafion®, Aciplex®, Aquivion®, 3M® PFSA (Perfluorosulfonic Acid), Fumion®, and non-fluorinated polymers including hexamethyl-p-terphenyl-poly(benzimidazole), and polysulfones including polyarylethersulfones, ethylene-tetrafluoroethylene-copolymers and polyetheretherketone (PEEK).

22. The method in accordance with claim 1 , wherein the surface region is a surface region of an electrode or of a carrier, wherein the carrier is a carrier film, wherein the surface region comprises or is substantially formed of carbon and/or metal.

23. The method in accordance with claim 1 , wherein the composite layer is detached from the surface region and is handled as a separate element.

24. An electrochemical unit, comprising a composite layer, wherein the composite layer is produced in a method in accordance with claim 1 .

25. The method according to claim 1 , wherein the hydrophobic polymer comprises a polyolefin selected from the group consisting of polyethylene (PE), polypropylene (PP), and combinations thereof.

Assignees

• Hahn Schickard Ges Fuer Angewandte Forschung E V

Inventors

• Breitwieser Matthias
• Lombeck Florian

Classifications

• H01M4/8892 Primary

  Impregnation or coating of the catalyst layer, e.g. by an ionomer · CPC title

• H01M4/8832

  Ink jet printing · CPC title

• H01M8/1011

  Direct alcohol fuel cells [DAFC], e.g. direct methanol fuel cells [DMFC] · CPC title

• H01M8/1053

  consisting of layers of polymers with at least one layer being ionically conductive · CPC title

• H01M8/1081

  starting from solutions, dispersions or slurries exclusively of polymers · CPC title