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DE-102024133250-A1 - METHOD FOR RECOVERING IONOMER AND CATALYST MATERIAL FROM A CATALYST MATERIAL-IONOMER MIXTURE

DE102024133250A1DE 102024133250 A1DE102024133250 A1DE 102024133250A1DE-102024133250-A1

Abstract

A process for recovering ionomer and catalyst material from a catalyst material-ionomer mixture comprises the following steps: Dispersing the catalyst material-ionomer mixture in a solvent to obtain a mixture of a catalyst material dispersion and an ionomer solution; Adding counterions to the mixture of the catalyst material dispersion and the ionomer solution to improve ionomer dissolution; and Separation of the catalyst material dispersion from the ionomer solution.

Inventors

  • Siebrand Johannes Thomas Homan
  • Kerem Aylar

Assignees

  • CELLCENTRIC GMBH & CO. KG

Dates

Publication Date
20260513
Application Date
20241113

Claims (16)

  1. A process for recovering ionomer (20) and catalyst material (10) from a catalyst material-ionomer mixture (10, 20), comprising the steps of: dispersing the catalyst material-ionomer mixture (10, 20) in a solvent (40) to obtain a mixture of a catalyst material dispersion and an ionomer solution; adding counterions (50) to the mixture of the catalyst material dispersion and the ionomer solution to improve the dissolution of the ionomer (20); and separating the catalyst material dispersion from the ionomer solution.
  2. Method according to the preceding claim, wherein the solvent (40) contains or is water and, after the addition of the counterions (50), the mixture of the catalyst material dispersion and the ionomer solution with the counterions (50) is heated to a temperature in the range of 180 °C to 220 °C.
  3. Procedure according to Claim 1 , in which the solvent (40) contains water and a water-soluble alcohol and, after the addition of the counterions (50), the mixture of the catalyst material dispersion and the ionomer solution with the counterions (50) is heated to a temperature in the range of 70 °C to 110 °C.
  4. Procedure according to Claim 1 , wherein the solvent (40) contains esters, ethers, alkylamines, alkylimines or aziridines or a mixture of two or more of the aforementioned solvents.
  5. Method according to any of the preceding claims, wherein the addition of counterions (50) involves the addition of an alkaline salt.
  6. Method according to the preceding claim, wherein the alkaline salt contains NaOH, NaCl, KCl, NaNH 2 , KNO 3 , CsCl or CaCl 2 or a mixture of two or more of the aforementioned alkaline salts.
  7. Method according to any of the preceding claims, wherein the ionomer (20) is an ionic polymer of perfluorosulfonic acid or contains a hydrocarbon skeleton with hydrocarbon side chains having sulfonic acid groups.
  8. Method according to any of the preceding claims, wherein the catalyst material (10) comprises carbon-supported platinum or a platinum alloy.
  9. The method according to the preceding claim, wherein the catalyst material (10) contains platinum supported on carbon, to which iridium oxide and/or ruthenium oxide and/or nickel and/or rhodium are added.
  10. Method according to any of the preceding claims, wherein the separation of the catalyst material dispersion from the ionomer solution is carried out by filtration.
  11. A method according to any of the preceding claims, wherein the catalyst material ionomer mixture (10, 20) is lost during the execution of a method for producing a membrane electrode assembly for use in a fuel cell.
  12. Method according to the preceding claim, wherein the catalyst material ionomer mixture (10, 20) falls off during the production of a catalyst dispersion, during the application of the catalyst dispersion to a support film, during the pressing of electrodes onto a membrane and simultaneous removal of the support film, or during the cutting of the coated membrane.
  13. Method according to any of the preceding claims, further comprising isolating the catalyst material (10) from the catalyst material dispersion and isolating the ionomer (20) from the ionomer solution.
  14. Method according to the preceding claim, wherein the isolation of the catalyst material (10) comprises drying the separated catalyst material dispersion and/or the method further comprises reactivation of the ionomer (20) in the ionomer solution prior to isolating the ionomer (20).
  15. Method according to the preceding claim, wherein the reactivation of the ionomer (20) is carried out using sulfuric acid.
  16. Use of a method according to one of the Claims 13 until 15 isolated catalyst material (10) and/or ionomer (20) for the production of a membrane electrode assembly for a fuel cell.

Description

The present invention relates to a method for recovering ionomer and catalyst material from a catalyst material-ionomer mixture, and to the use of a catalyst material and/or ionomer isolated by the method for manufacturing a membrane electrode assembly for a fuel cell. The present invention relates in particular to a method for recovering ionomer and catalyst material (especially carbon-supported platinum, Pt/C) from electrode material that is lost during the manufacturing process of a membrane electrode assembly (MEA) for use in a fuel cell. From the US 8 124 261 B2 A process for recovering the ionomer of a polymer electrolyte membrane (PEM) and the catalyst materials from a membrane electrode assembly (MEA) is known. In this process, fragments of an MEA are first dispersed in an alcohol/water mixture, using specific alcohols such as n- and sec-butanol. The fragments are then sieved. The remaining ionomer/catalyst material/solvent dispersion is then separated into a catalyst material-containing fraction and an ionomer-containing fraction using known filtration techniques. The solvent is recovered. The filtered-off catalyst material is also recovered, for example, by burning the filter and the carbon particles in air. However, this process alters the catalyst material, preventing its direct reuse. The ionomer is also recovered by ultrafiltration. However, there is currently no way to separate raw materials used in fuel cell systems or electrolysis cells without damaging the raw materials. The raw material yield in the production of a MEA or CCM (catalyst-coated membrane) depends on the individual manufacturing steps. The steps of producing a catalyst dispersion (mixing), applying this dispersion to a carrier film (coating), pressing electrodes onto a membrane and simultaneously removing the carrier film (transfer process), and other possible steps (cutting, punching, etc.) each have a material utilization rate of 90–99.9% according to current technology. The overall process is therefore estimated at approximately 95%, meaning that 5% of the materials used cannot be utilized in the product. These materials are a cost driver for fuel cells and electrolyzers, and their recycling is currently inefficient and potentially environmentally harmful. One object of the present invention is to improve a method for recovering ionomer and catalyst material from a catalyst material-ionomer mixture. This problem is solved by the features of the independent patent claim. Further preferred embodiments of the invention are the subject of the dependent patent claims. According to a first aspect of the present invention, a method for recovering ionomer and catalyst material from a catalyst material-ionomer mixture comprises the following steps: Dispersing the catalyst material-ionomer mixture in a solvent to obtain a mixture of a catalyst material dispersion and an ionomer solution; Addition of counterions, in some versions the addition of an alkaline salt, to the mixture to improve the solubility of the ionomer; and Separation of the catalyst material dispersion from the ionomer solution. This eliminates the need, in some embodiments, to dissolve a precious metal contained in the catalyst material, which in some embodiments is or contains a catalytically active material. Furthermore, this enables the separation of raw materials from the catalyst material-ionomer mixture, which may include ink, offcuts, or similar components, directly within the catalyst dispersions and electrodes. This significantly reduces production losses, leads to a financial competitive advantage, and also protects the environment, as no fluorine is produced, as is the case with the combustion of polymers. If aged material, which has been physically altered, for example, by thousands of hours of use in fuel cells, is employed, this material can be processed more easily using the inventive method than by combustion or by chemically/electrochemically obtained pure metal. Furthermore, in some designs, this allows the original state of the materials in the catalyst material-ionomer mixture to be preserved or restored without burning organic materials or dissolving the precious metals through the use of acids, potentials, or similar processes. The solvents used, and optionally alkali salts or bases which may contain the counterions, can be purified in a batch process for reuse in the process according to the invention, thus creating a closed, energy-efficient cycle. In some embodiments, this can lead to cost savings and also represent an environmentally friendly way to avoid carbon dioxide and fluorine emissions, such as those produced during the combustion of fluoropolymers. The catalyst material-ionomer mixture can be provided wet or dry before dispersion. In some designs, when the catalyst material-ionomer mixture is dispersed in the solvent, the ionomer component can be completely dissolved (from the catalyst material). In some designs, the catalyst materi