Oxygen-consuming electrode and method for producing same

Patent metadata

Field	Value
Publication number	US-10711356-B2
Application number	US-201515510286-A
Country	US
Kind code	B2
Filing date	Aug 28, 2015
Priority date	Sep 12, 2014
Publication date	Jul 14, 2020
Grant date	Jul 14, 2020

Abstract

The invention relates to an oxygen-consuming electrode, in particular for use in chloralkali electrolysis, comprising a novel catalyst coating based on carbon nanotubes and a silver-based cocatalyst, and to an electrolysis device. The invention further relates to a method for producing said oxygen-consuming electrode and to the use thereof in chloralkali electrolysis or fuel cell technology.

First claim

The invention claimed is:

1. A gas diffusion electrode for the reduction of oxygen, where the gas diffusion electrode has at least one sheet-like, electrically conductive support, and a gas diffusion layer and an electrocatalyst applied to the support,
wherein the gas diffusion layer consists of at least a mixture of carbon nanotubes and a fluoropolymer,
wherein the carbon nanotubes and the fluoropolymer are dry mixed together with a silver-containing cocatalyst in powder form and then applied to the support and compacted with an application of a pressing force on the support and,
wherein the carbon nanotubes act as the electrocatalyst,
wherein from 1 to 55% by weight of the silver-containing cocatalyst, based on the total content of the electrocatalyst, the silver-containing cocatalyst, and the fluoropolymer, is present as a further electrocatalyst.

2. The gas diffusion electrode as claimed in claim 1 , wherein the mixture of the carbon nanotubes, the silver containing cocatalyst, and the fluoropolymer contains from 1 to 70% by weight of the fluoropolymer and 99-30% by weight of the carbon nanotubes and the silver containing cocatalyst.

3. The gas diffusion electrode as claimed in claim 1 , wherein the weight ratio of the silver-containing cocatalyst to the carbon nanotubes is from 1:98 to 55:40.

4. The gas diffusion electrode as claimed in claim 1 , wherein the electrode has a thickness of from 0.2 to 3 mm.

5. The gas diffusion electrode as claimed in claim 1 , wherein the porosity of the electrode is from 70 to 90%.

6. The gas diffusion electrode as claimed in claim 1 , wherein the silver containing cocatalyst consists of silver, silver oxide or a mixture of silver and silver oxide.

7. The gas diffusion electrode as claimed in claim 1 , wherein the gas diffusion layer has been applied on one side or two sides of the support.

8. The gas diffusion electrode as claimed in claim 1 , wherein the carbon nanotubes have a content of catalyst residues of a catalyst used for producing the carbon nanotubes of less than 1% by weight.

9. The gas diffusion electrode as claimed in claim 1 , wherein the carbon nanotube powder is present as an agglomerate, with at least 95% by weight of the agglomerate particles having an external diameter in the range from 30 μm to 5000 μm.

10. The gas diffusion electrode as claimed in claim 1 , wherein support is configured as mesh, nonwoven, foam, woven fabric, braid or expanded metal.

11. The gas diffusion electrode as claimed in claim 1 , wherein the support consists of carbon fibers, nickel, silver or nickel coated with noble metal.

12. A process for producing a gas diffusion electrode as claimed in claim 1 , where the gas diffusion electrode has at least one sheet-like, electrically conductive support, and a gas diffusion layer and an electrocatalyst applied to the support,
wherein the gas diffusion layer consists at least of a mixture of carbon nanotubes and a fluoropolymer, with the carbon nanotubes acting as the electrocatalyst,
wherein the carbon nanotubes and the fluoropolymer are dry mixed together with a silver containing cocatalyst in powder form and then applied to the support and compacted with application of a pressing force,
wherein from 1 to 55% by weight of the silver-containing cocatalyst, based on the total content of the electrocatalyst, the silver containing cocatalyst, and the fluoropolymer, is used as cocatalyst.

13. The process as claimed in claim 12 , wherein the dry mixing is carried out in a first phase to give a homogeneous premix, with the temperature of the mixture being not more than 25° C.

14. The process as claimed in claim 13 , wherein the dry mixing is carried out in a second phase using mixing tools after the homogeneous premix has been obtained from the first phase, with the temperature of the powder mixture being at least 30° C.

15. The process as claimed in claim 12 , wherein compaction is carried out by means of rollers in a roller apparatus, with the linear pressing force applied by the rollers to the support and the powder mixture is from 0.1 to 1 kN/cm.

16. The process as claimed in claim 15 , wherein the rolling is carried out at a constant ambient temperature.

17. A method comprising utilizing the gas diffusion electrode as claimed in claim 1 as an oxygen-depolarized electrode for the reduction of oxygen in an alkaline medium or as an electrode in an alkaline fuel cell or as electrode in a metal/air battery.

18. An electrolysis apparatus having a gas diffusion electrode as claimed in claim 1 as an oxygen-depolarized cathode.

Assignees

• Covestro Deutschland Ag

Inventors

• Bulan Andreas
• Kintrup Jürgen

Classifications

• H01M4/9041

  Metals or alloys (H01M4/92 takes precedence) · CPC title

• H01M4/8896

  Pressing, rolling, calendering (membrane electrode assemblies H01M8/1004) · CPC title

• H01M4/8657

  layered · CPC title

• H01M4/8652

  as mixture · CPC title

• H01M8/083

  Alkaline fuel cells · CPC title