Oxygen-consuming electrode and method for producing same

Patent metadata

Field	Value
Publication number	US-2017298524-A1
Application number	US-201515510286-A
Country	US
Kind code	A1
Filing date	Aug 28, 2015
Priority date	Sep 12, 2014
Publication date	Oct 19, 2017
Grant date	—

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

1 .- 18 . (canceled)

19 . 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 electrocatalyst applied to the support, the gas diffusion layer consists at least of a mixture of carbon nanotubes and a fluoropolymer, the carbon nanotubes and fluoropolymer have been applied and compacted in powder form on the support and the carbon nanotubes act as electrocatalyst, wherein from 1 to 55% by weight of silver-containing cocatalyst, based on the total content of catalyst and fluoropolymer, is present as further electrocatalyst.

20 . The gas diffusion electrode as claimed in claim 19 , wherein the mixture of firstly carbon nanotubes and cocatalyst and secondly fluoropolymer, contains from 1 to 70% by weight of fluoropolymer and 99-30% by weight of carbon nanotubes and cocatalyst.

21 . The gas diffusion electrode as claimed in claim 19 , wherein the weight ratio of silver-containing cocatalyst to carbon nanotubes is from 1:98 to 55:40, preferably from 1:95 to 30:65.

22 . The gas diffusion electrode as claimed in claim 19 , wherein the electrode has a thickness of from 0.2 to 3 mm.

23 . The gas diffusion electrode as claimed in claim 19 , wherein the porosity of the electrode is from 70 to 90%.

24 . The gas diffusion electrode as claimed in claim 19 , wherein the cocatalyst consists of silver, silver oxide or a mixture of silver and silver oxide.

25 . The gas diffusion electrode as claimed in claim 19 , wherein the gas diffusion layer has been applied on one side or two sides to the surfaces of the support.

26 . The gas diffusion electrode as claimed in claim 19 , wherein the carbon nanotubes have a content of catalyst residues of the catalyst used for producing the carbon nanotubes of less than 1% by weight.

27 . The gas diffusion electrode as claimed in claim 19 , wherein the carbon nanotube powder is present as agglomerate, with at least 95% by weight of the agglomerate particles having an external diameter in the range from 30 μm to 5000 μm.

28 . The gas diffusion electrode as claimed in claim 19 , wherein the electrically conductive support is configured as mesh, nonwoven, foam, woven fabric, braid or expanded metal.

29 . The gas diffusion electrode as claimed in claim 19 , wherein the electrically conductive support consists of carbon fibers, nickel, silver or nickel coated with noble metal.

30 . A process for producing a gas diffusion electrode as claimed in claim 19 , where the gas diffusion electrode has at least one sheet-like, electrically conductive support and a gas diffusion layer and electrocatalyst applied to the support and the gas diffusion layer consists at least of a mixture of carbon nanotubes and fluoropolymer, with the carbon nanotubes acting as electrocatalyst, wherein the carbon nanotubes and the fluoropolymer are dry mixed together with a cocatalyst in powder form and then applied to the support and compacted with application of a pressing force, where from 1 to 55% by weight of silver-containing cocatalyst, based on the total content of catalyst and fluoropolymer, is used as cocatalyst.

31 . The process as claimed in claim 30 , 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.

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

33 . The process as claimed in claim 30 , wherein compaction is carried out by means of rollers in a roller apparatus, with the linear pressing force applied by the roller(s) used to the support and the sprinkled-on powder mixture preferably being from 0.1 to 1 kN/cm.

34 . The process as claimed in claim 30 , wherein rolling is carried out at constant ambient temperature.

35 . A method comprising utilizing the gas diffusion electrode as claimed in claim 19 as oxygen-depolarized electrode for the reduction of oxygen in an alkaline medium or as electrode in an alkaline fuel cell or as electrode in a metal/air battery.

36 . An electrolysis apparatus having a gas diffusion electrode as claimed in claim 19 as oxygen-depolarized cathode.

Assignees

• Covestro Deutschland Ag

Inventors

• Bulan Andreas
• Kintrup Jürgen

Classifications

• H01M12/06

  with one metallic and one gaseous electrode · CPC title

• H01M4/9041

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

• H01M4/96

  Carbon-based electrodes · CPC title

• H01M4/8605

  Porous electrodes · CPC title

• C25B1/34

  Simultaneous production of alkali metal hydroxides and chlorine, oxyacids or salts of chlorine, e.g. by chlor-alkali electrolysis · CPC title