Direct coating of anion-exchange membrane with catalytically active substance

Abstract

To provide a coating process of anion-exchange membrane (AEM) with a catalytically active substance, in which: a CCM produced in such a process is used for an electrochemical cell, specifically in an alkaline water electrolysis; surface smoothness needed for the AEM is maintained; ideally, the use of a removable film and CMR substances is avoided; a method of producing the CCM by direct coating is provided; swelling must also be minimized; and this process must also be feasible with an ionomer without fluorine.SOLUTION: The notion of the present invention is based on the finding (anti-swelling agent) that addition of a specific organic substance results in only a small degree of swelling even though an AEM swells. A substance suitable as the anti-swelling agent is found to be identifiable by a solubility behavior thereof, or more specifically, by the Hansen parameter. Figure 4 accompanies the summary.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to the coating of anion exchange membranes with catalytically active materials. [Background technology]

[0002] Catalytically active coated anion exchange membranes are used in electrochemical cells, particularly in water electrolysis.

[0003] Anion exchange membranes (AEMs) are installed in electrochemical cells. They are typically used to separate reaction products from the anode and cathode and conduct negatively charged ions (anions) toward the anode, making the electrochemical reactions carried out within the cell more efficient, safer, or even possible.

[0004] An example of an electrochemical process performed using an anion exchange membrane is alkaline water electrolysis to produce hydrogen and oxygen. This is done by using an anion exchange membrane as a separator between the electrodes of the cell. For this reason, the process is also called alkaline membrane water electrolysis (AEMWE). Because the reaction occurs in an alkaline medium, AEM water electrolysis is often also called alkaline membrane water electrolysis.

[0005] In AEM-based water electrolysis, an electrochemical cell is filled with water or a basic aqueous electrolyte, and a voltage is applied between the anode and cathode. At the cathode, water (HO) is converted into hydrogen (H) and hydroxide ions (OH). - ) (Equation K). The anion exchange membrane transports the hydroxide ions to the anode side, where they are oxidized to oxygen (O2) (Equation A). This results in the formation of oxygen on the anode side and hydrogen on the cathode side. Therefore, the anode side is also called the oxygen side, and the cathode side is also called the hydrogen side.

[0006] 2H2O+2e-→H2+2OH - (K) Reduction / Cathode Reaction 2OH- → 1 / 2O2 + H2O + 2e - (A) Oxidation / anodic reaction To achieve the described effect, the anion exchange membrane must conduct hydroxide ions between the anode and cathode. Apart from ionic conductivity, it must also be as electrically insulating as possible to prevent electrical shorts between the anode and cathode. Finally, the anion exchange membrane must have as low gas permeability as possible to avoid backmixing of the gases that would otherwise form. Furthermore, the anion exchange membrane must be resistant to the alkaline conditions present in AEM water electrolysis. These properties are met by specific anion-conducting polymers (also known as anion-conducting ionomers). Anion exchange membranes are made entirely or at least partially from such anion-conducting monomers. AEMs typically exist in the form of flat membranes.

[0007] To promote the reactions within the electrochemical cell, catalytically active or activatable materials (also known as electrocatalysts) are incorporated into both the cathode and anode sides. This is achieved by introducing catalytically active layers into the cell or by catalytically active coatings of the cell components. These may be present on a substrate or porous transport layer specially introduced into the cell for the purpose (catalyst-coated substrate, CCS), or the membrane may be directly coated with the catalytically active material (catalyst-coated membrane, CCM).

[0008] A good overview of the construction and materials of electrochemical cells currently used in AEM water electrolysis is given by:

[0009] Miller, Hamish Andrew et al:Green hydrogen from anion exchange membrane water electrolysis:a review of recent developments in critical materials and operating conditions.Sustainable Energy Fuels,2020,4,2114 DOI:10.1039 / c9se01240k After addressing the fundamental issues regarding material selection and operating conditions, a question that arises in the development of a system for operating an electrochemical process is how the individual components of the electrochemical cell can be manufactured on an industrial scale.

[0010] Therefore, keeping the internal resistance of the electrochemical cell as low as possible is important for energy efficiency, which can be made possible in a compact design by locating the electrodes particularly close to the separator and by locating the electrocatalysts as close as possible to their respective electrodes.

[0011] One way to achieve this compact structure is the aforementioned CCM design, in which the anion exchange membrane is coated with a catalytically active / catalytically activatable material. Thus, the anion exchange membrane prepared in this manner already incorporates the electrode catalyst during cell assembly. This eliminates the need for catalyst handling during cell assembly and achieves a compact cell structure that allows for low internal resistance.

[0012] When coating an anion exchange membrane with an electrocatalyst, it should be noted that the substrate (membrane) and the coating material (catalyst) are very different materials: the membrane generally consists of an ion-conducting specialty polymer (ionomer) in the form of a film, while the electrocatalyst used is typically in the form of a metal or metal oxide in the form of particles. To fix the catalytically active particles on the film, a polymer adhesion promoter is used, which adhesively bonds the particles to the membrane. The adhesion promoter can also be an ionomer made from a material similar to the material of the anion exchange membrane.

[0013] The fabrication of CCMs is challenging due to the heterogeneity of the materials involved. Handling the materials during coating is also difficult.

[0014] One process used in both the manufacturing and industrial production of CCMs is the so-called decal method. In this process, the catalyst is first mixed with a thermoplastic adhesion promoter to form a coating compound, which is then applied to a transfer substrate, usually a PTFE film. The coated transfer substrate is then pressed against an anion exchange membrane and heated. The thermoplastic melts, adhesively bonding the catalyst particles to the membrane. The PTFE film is then removed from the membrane like a decal and discarded. The coating remains on the membrane and consists of the adhesion promoter and the catalyst particles fixed within it.

[0015] The outline of the decal method is as follows: Frolich, Konstantin: "Der Decal-Prozess zur Herstellung katalysatorbeschichteter Membranen fur PEM-Brennstoffzelen Schriftenreihe des Institutes fur Angewandte Materialien, Karlsruher Institut fur Technologie.", DOI: 10.5445 / KSP / 1000045306.

[0016] Although Frolich describes the decal method in terms of CCMs intended for use in PEM fuel cells (PEM stands for proton exchange membrane - proton conducting membrane), the teachings therein can in principle also be applied to CCMs as used in AEM-based water electrolysis.

[0017] However, the decal process has recognized fundamental drawbacks, such as the need for high pressure and high temperature during pressing in order for the adhesion promoter to correspondingly bond the catalyst particles to the membrane material. However, membrane materials used in alkaline water electrolysis are often very temperature sensitive, and as a result, the temperatures typically used in the decal process are too high. This is even more true when an anion-conducting polymer is used as the adhesion promoter.

[0018] A further inherent drawback of the decal method is the need for a transfer substrate. These transfer substrates (usually films made of PTFE) are removed from the coated membrane and discarded after coating or at the latest before the CCM is installed in the cell (removable film). This is of concern for environmental reasons, especially when fluorine-containing polymers such as PTFE are used as the film material for the transfer substrate.

[0019] Therefore, it is important to develop a method for making CCMs that can be used for alkaline membrane water electrolysis without using transfer films. The ion exchange membranes shall be directly coated with a catalytically active or activatable layer, among other things.

[0020] The corresponding direct coating process is described by Koch et al.: Already proposed by Koch, S., Metzler, L., Kilian, SK, Heizmann, PA, Lombeck, F., Breitwieser, M., Vierrath, S., Toward Scalable Production: Catalyst-Coated Membranes (CCMs) for Anion-Exchange Membrane Water Electrolysis via Direct Bar Coating. Adv. Sustainable Syst. 2023, 7, 2200332. DOI: 10.1002 / adsu.202200332.

[0021] In this method, a flat anion-conducting membrane is first masked with a PTFE film, and its free areas are then directly coated with the catalyst-containing composition. A protective film, also made of PTFE, is then attached by adhesive bonding. The mask is used to absorb stress within the membrane, preventing excessive distortion during coating. The change in membrane shape is due to the solvents (water and methanol) present in the composition swelling the membrane material. The penetration of the solvent mixture into the membrane material increases the membrane's volume during coating, resulting in the introduction of mechanical stresses at the interface between the catalyst and the membrane, which leads to distortion of the coated membrane. In extreme cases, the coated membrane may even wrinkle. It is virtually impossible to install a distorted or wrinkled CCM in an electrochemical cell.

[0022] However, even slight deviations from planarity of the CCM can result in the electrochemical cell's sealing elements not properly seating in the CCM's contact areas, thus leading to potential leaks in the electrochemical cell. Because many electrolysis processes produce potentially toxic or explosive gases, clean sealing of the cell is essential. This can only be achieved with a sufficiently wrinkle-free CCM. However, even during CCM fabrication, membrane swelling should be avoided to the greatest extent possible, as it reduces processability in the coating machine and therefore hinders belt transport, especially in streamlined roll-to-roll processes. For all these reasons, Susanne Koch's research group used masking films to reduce membrane distortion during coating.

[0023] A drawback of the method proposed by Koch et al. is the need for a masking film to prevent swelling of the membrane and, ultimately, wrinkle formation. Similar to the transfer substrate in the decal method, the mask serves only to fabricate the CCM and must be removed from the CCM again in a ready-to-use state. Therefore, the mask must also be considered a removable film. This process also requires a lot of manual labor and does not yet appear to be scalable from an industrial perspective.

[0024] Furthermore, the composition used by Koch et al. to coat the AEM contains methanol as a solvent for the adhesion promoter. Because methanol is known to be carcinogenic, mutagenic, or reproductively toxic, this solvent is classified as a CMR substance according to the GHS, and appropriate safety precautions must be taken when using it. While this does not pose a major problem in the laboratory, on an industrial scale, it would be very complicated and therefore expensive.

[0025] WO 2023088714 discloses a composition containing a dissolved anion-conducting ionomer and an electrocatalyst. The composition contains dimethyl sulfoxide (DMSO) as a solvent for the anion-conducting polymer and an ethanol / water mixture as a dispersion medium. Neither of these substances is classified as a CMR-related material. This composition is used to produce CCMs or CCSs that can be used in AEMWEs. In the experimental section of WO 2023088714, the composition is applied directly to various substrates using an ultrasonic spray coater. Subsequent experiments described therein demonstrate that AEMs coated with this composition develop wrinkles.

[0026] Chinese Patent No. 115832338 discloses a machine for manufacturing CCMs for PEM fuel cells. The machine performs a roll-to-roll process. Temperature control is adapted to reduce membrane swelling. The processed ionomer conducts only protons and is therefore not suitable for use in AEMWEs.

[0027] EP 4223417 describes a coating composition for producing water electrolysis cells. The composition comprises a nickel-iron (oxide) hydroxide as an electrocatalyst, an organic polymer, and a solvent. In this formulation, the solvent and polymer are selected so that the Hansen parameters of these two components maintain a certain geometric distance from the Hansen parameters of the electrocatalyst. In the examples, different solvent mixtures are tested, for example, a mixture of 1-propanol and ethanol or a mixture of 2-propanol and water. The Hansen parameters of these solvents are shown in Table 1. The organic polymer is in both cases Nafion®, a proton-conducting fluoropolymer. The polymer transports hydroxide ions OH - It does not conduct ions, making it inherently unsuitable for use as an ionic conductor in AEM-based water electrolysis. There are also concerns about its use due to its fluorine content.

[0028] WO 2023183721 describes a composition containing a carbon-supported precious metal catalyst, in which the solvent present is water and at least one substance selected from 1-propanol, 2-propanol, NMP, DMAC, DMSO, DMF, and cyclopentanone. The solvents N,N-dimethylacetamide (DMAC), N,N-dimethylformamide (DMF), and N-methyl-2-pyrrolidone (NMP) are all known to be carcinogenic, mutagenic, or reproductively toxic, and therefore are classified as CMR substances under the GHS. Therefore, as mentioned above, their industrial use requires expensive safety measures. The composition described in WO 2023183721 is further intended for the production of carbon capture and storage (CCS) catalysts for use in high-temperature fuel cells, which require special proton-conducting ionomers.

[0029] Various CMR-free compositions for producing CCM for AEMWE are described in European Patent Application No. 24159645.1 by the same applicant, which has not yet been published at the time of filing this application, and which contain the solvents dimethyl sulfoxide, ethanol and / or 2-propanol together with acetonitrile and water.

[0030] A further European patent application by the same applicant, No. 24152389.3, which has not yet been published at the time of filing this application, also relates to a composition containing an electrocatalyst, an ionomer, and a solvent. The solvent is a mixture of dimethyl sulfoxide, ethanol, and a small amount of acetonitrile. This composition is also intended for the production of CCMs that can be used for alkaline water electrolysis.

[0031] Yet another European Patent Application No. 24169671.5 by the same applicant, which has not yet been published at the time of filing this application, describes a catalyst ink containing at least one first solvent, at least one polymer dissolved in the first solvent, at least one particulate electrocatalytically active or activatable electrocatalyst, and at least one particulate inorganic material different from the electrocatalyst. Solvents considered include dimethyl sulfoxide (DMSO), ethanol (EtOH), acetonitrile (ACN), or methanol (MeOH). The catalyst ink may further contain a dispersion medium, such as water (HO), N-methyl-2-pyrrolidone (NMP), N,N-dimethylacetamide (DMAC), acetone (ACT), or 2-propanol (IPA). A special feature of this catalyst ink is that it is intended for application to a transfer substrate, not an anion exchange membrane. [Prior art documents] [Patent documents]

[0032] [Patent Document 1] International Publication No. 2023088714 [Patent Document 2] Chinese Patent No. 115832338 [Patent Document 3] European Patent Application Publication No. 4223417 [Patent Document 4] International Publication No. 2023183721 [Patent Document 5] European Patent Application No. 24159645.1 [Patent Document 6] European Patent Application No. 24152389.3 [Patent Document 7] European Patent Application No. 24169671.5 [Non-patent literature]

[0033] [Non-Patent Document 1] Miller, Hamish Andrew et al:Green hydrogen from anion exchange membrane water electrolysis:a review of recent developments in critical materials and operating conditions.Sustainable Energy Fuels,2020,4,2114 DOI:10.1039 / c9se01240k [Non-patent document 2] Frolich, Konstantin: "Der Decal-Prozess zur Herstellung katalysatorbeschichteter Membranen fur PEM-Brennstoffzelen Schriftenreihe des Institutes fur Angewandte Materialien, Karlsruher Institut fur Technologie.", DOI: 10.5445 / KSP / 1000045306 [Non-patent document 3] Koch, S., Metzler, L., Kilian, SK, Heizmann, PA, Lombeck, F., Breitwieser, M., Vierrath, S., Toward Scalable Production:Catalyst-Coated Membranes(CCMs) for Anion-Exchange Membrane Water Electrolysis via Direct Bar Coating.Adv.Sustainable Syst.2023,7,2200332.DOI:10.1002 / adsu.202200332 Summary of the Invention [Problem to be solved by the invention]

[0034] In view of this prior art, the objective of the present invention is to identify a method for producing coated anion exchange membranes by direct coating with an electrocatalytically active or activatable material that maintains the necessary flatness of the AEM and ideally avoids the use of removable films. The catalytically coated anion exchange membrane (CCM) should be usable for alkaline water electrolysis. Minimizing swelling is necessary to improve processability in industrial-scale mechanized manufacturing. The method should also be feasible with fluorine-free ionomers and ideally eliminate CMR materials. [Means for solving the problem]

[0035] The objective is to achieve the following non-chronological processes: a) At least the following ingredients: i) an electrocatalyst; ii) a solvent; and iii) anionic conductive polymers; providing a viscous composition comprising: b) providing an anion exchange membrane comprising at least one membrane material; c) applying a viscous composition to the anion exchange membrane; d) drying the viscous composition applied to the anion exchange membrane; e) obtaining a coated anion exchange membrane comprising a layer comprising an electrocatalyst and an anion-conducting polymer on at least one side, wherein the electrocatalyst is bonded to the membrane material via the anion-conducting polymer; This is achieved by a method comprising: the anion-conducting polymer, the membrane material, and the solvent are selected to be compatible with each other so that the anion-conducting polymer and the membrane material are each soluble in the solvent; The viscous composition comprises the following components: iv) an organic substance different from the solvent, Hansen solubility parameters δD, δP and δH in the following ranges: 15 MPa 0.5 <δD<35MPa 0.5 6 MPa 0.5 <δP<15MPa 0.5 2.5MPa 0.5 <δH<7.1MPa 0.5 The present invention is characterized in that it additionally contains an organic substance in which

[0036] An essential feature of the present invention is that the membrane material, the anion-conducting polymer, the solvent, and any additional organic substances present are selected to be compatible with one another. The solubility behavior of the solvent is matched with respect to the membrane material and the anion-conducting polymer. The solvent is specifically selected to dissolve both the membrane material and the anion-conducting polymer present in the composition.

[0037] The issue of monosolubility can be clarified by the following test: 27 g of the organic substance under investigation and 3 g of the anion-conducting polymer / membrane material under investigation are placed in a container. No other organic substances are added. The container is sealed and shaken at 60°C for 4 hours. If the anion-conducting polymer or membrane material is dissolved by this procedure, the anion-conducting polymer or membrane material is soluble in the organic substance under investigation in the context of this invention. If the anion-conducting polymer or membrane material does not dissolve during this treatment, it is not soluble in the substance under investigation.

[0038] The question of whether an anion-conducting polymer or membrane material is soluble in the combination of two organic substances is answered by the following experiment.

[0039] A container is charged with 13.5 g of the first organic substance under investigation and 13.5 g of the second organic substance under investigation. 3 g of the anion-conducting polymer or membrane material under investigation is added to the container. No other organic substances are added. The container is sealed and shaken at 60°C for 4 hours. If the anion-conducting polymer or membrane material is dissolved by this procedure, then the anion-conducting polymer or membrane material is soluble in the combination of the two organic substances under investigation in the context of the present invention. Otherwise, it is insoluble.

[0040] The present invention is based on the finding that the addition of certain organic substances to a composition results in the composition swelling the anion exchange membrane only to a small extent, if at all. Accordingly, the additionally present organic substances are also referred to as "anti-swelling agents."

[0041] Since the solvent is generally also an organic substance, the viscous composition contains at least two organic substances: a solvent and an anti-swelling agent.

[0042] These two organic substances fulfill two functions within the viscous composition system. The first function is to dissolve the anion-conducting polymer. Therefore, the first function is that of a solvent. The second function is to prevent swelling of the anion-exchange membrane. Therefore, the second function is that of an anti-swelling agent. These two functions are only needed during the coating process. Both organic substances are evaporated by drying after coating. Therefore, the anion-conducting polymer precipitates from the solution, immobilizing the electrode catalyst on the anion-exchange membrane.

[0043] After drying, the electrocatalyst and anion-conducting polymer form a catalytically active coating on the anion-exchange membrane, with the anion-conducting polymer acting as an adhesion promoter to anchor the electrocatalyst onto the anion-exchange membrane by connecting it to the membrane material.

[0044] Surprisingly, it has been found that substances suitable as antiswelling agents can be distinguished in both cases by their solubility behavior, more precisely by their Hansen solubility parameters δD, δP and δH, which are called "Hansen parameters" for short and are given below: Hansen, Charles.M.: The Universality of the Solubility Parameter. First described by Ind.Eng.Chem.Prod.Res.Dev.1969,8,1,2-11 DOI 10.1021 / i360029a002.

[0045] The Hansen parameters of the contemplated materials can be found in the literature or can be measured. The measurement temperature is 20°C. Table 1 lists the Hansen parameters of the materials considered here. In case of doubt, the values ​​in Table 1 apply.

[0046] According to the present invention, the organic substance (anti-swelling agent) selected has a Hansen parameter in the following range: 15 MPa 0.5 <δD<35MPa 0.5 6 MPa0.5 <δP<15MPa 0.5 2.5MPa 0.5 <δH<7.1MPa 0.5 It is a substance found in

[0047] These requirements should be understood to mean that all three conditions must be cumulatively met: if only one of the three Hansen parameters δD, δP, and δH is outside the respective ranges defined above, the organic material will not be able to perform the function intended by the present invention.

[0048] δD<20MPa 0.5 is preferably further applied.

[0049] The anti-swelling effect of ionomers is believed to be due to the solubility or crosslinking behavior of the added organic materials. Polar materials with low dipole-dipole interactions and low energy from hydrogen bonding appear to be advantageous. Because of their mode of action, these organic materials are now described as "antiswelling agents."

[0050] Specific examples of suitable organic anti-swelling agents include (1S,5R)-6,8-dioxabicyclo[3.2.1]octan-4-one, cycloheptanone, cyclohexanone, and cyclopentanone. These substances exhibit excellent anti-swelling properties, are not listed as CMR substances, and can even be obtained from renewable raw materials. Other suitable anti-swelling agents include benzonitrile, butanone, acetone, and acetophenone.

[0051] In principle, it is also possible to use several individually suitable anti-swelling agents as an anti-swelling agent mixture. When two or more anti-swelling agents are used as a mixture, the weight fraction of the anti-swelling agent mixture is used as the weight fraction of the anti-swelling agent. Each individual anti-swelling agent present in the anti-swelling agent mixture must satisfy the parameters defined for its Hansen parameters.

[0052] According to the present invention, the anti-swelling agent and the solvent are chemically different. They are also particularly preferably functionally different, meaning that the anti-swelling agent cannot simultaneously function as a solvent. For this reason, the anion-conducting polymer, the membrane material, and the organic substance are preferably selected to be compatible with each other so that the anion-conducting polymer and the membrane material are insoluble in the organic substance, respectively. Insolubility is tested using the test described above.

[0053] The following solvents have proven particularly advantageous for blending viscous compositions: dimethyl sulfoxide, ethanol, 1-propanol, 2-propanol, acetonitrile. These solvents also do not contain CMR. Of course, it is also possible to use several of these solvents together as a mixed solvent. The statements made above regarding the individual solvents apply depending on the weight fraction of the solvent mixture.

[0054] Preferably, the anion-conducting polymer dissolves completely in the solvent / solvent mixture when the viscous composition is provided and / or applied. This allows for a lump-free viscous composition and facilitates application. During drying, the solvent evaporates, thus causing the anion-conducting polymer to precipitate from solution.

[0055] In addition to the four basic components of the electrode catalyst, solvent, anion-conducting polymer, and anti-swelling agent, the viscous composition used in accordance with the present invention may also contain additional components. It is particularly preferred to additionally contain a dispersion medium different from the solvent and anti-swelling agent. Water is recommended as the dispersion medium. The dispersion medium is used to adjust the viscosity of the composition. The dispersion medium is at least partially volatilized during drying.

[0056] The catalyst-containing viscous composition onto which the AEM is coated may have different degrees of viscosity; on the one hand, it is considered that the viscous composition is quite paste-like. The viscous composition is then also called a "catalyst paste." The catalyst paste is highly viscous. However, the viscous composition can also have a very low dynamic viscosity (mobility). In this form, the composition tends to be called a "catalyst ink."

[0057] It is also possible that the viscosity of the composition may change during processing, in which case the viscous composition may be provided as a paste but applied as an ink, by adjusting the processing temperature, which significantly affects the dynamic viscosity of the viscous composition.

[0058] The dynamic viscosity η can be quantified by a characteristic value. The characteristic value of the dynamic viscosity η of a composition is 10 1 mPas~10 4 The dynamic viscosity η should be measured at a temperature of 25 °C using a rotational rheometer with a plate-plate geometry. The diameter of the plates is 40 mm and the distance between the plates is 1 mm. The dynamic viscosity η is ...0.1 s -1 ~1000s -1 The characteristic values ​​used are measured at increasing shear rates between 1 s -1 Suitable rotational rheometers with plate-plate geometry are available, for example, from Malvern Kinexus.

[0059] To avoid introducing destructive substances into the catalytic layer of the anion exchange membrane that could impair electrolysis, the viscous composition should ideally consist only of the components explicitly listed above. However, in some situations, it may still be necessary to add additional components to the composition that are different from the above-mentioned components. These may be selected from organic or inorganic additives, such as dispersing agents, rheological agents, surfactants, or conductive additives. Specific examples of additional components include silica or carbon black. Carbon black is a conductive additive, and silica is suitable as a rheological agent.

[0060] Specific formulation specifications for the viscous compositions used in accordance with the present invention are set forth in Table 2.

[0061] [Table 2]

[0062] The weight percentages specified in Table 2 are in all cases based on the total weight of the viscous composition. Of course, the sum of the weight percentages of all the components listed here does not exceed 100% by weight. However, it is equally possible that the sum of the weight percentages of all the components listed here is less than 100%, i.e., if additional components other than the listed components are present.

[0063] It is preferred if the electrocatalyst is present in particulate form, i.e., as a powder or granules, which is a formulation that can be easily mixed into a catalyst paste or ink with the addition of polymers, solvents, and anti-swelling agents.

[0064] Electrocatalysts must contain at least one electrocatalytically active element to promote the intended electrochemical reaction. Examples of such electrocatalytically active elements include iridium (Ir), nickel (Ni), cobalt (Co), chromium (Cr), iron (Fe), ruthenium (Ru), copper (Cu), molybdenum (Mo), zinc (Zn), lead (Pb), manganese (Mn), tungsten (W), platinum (Pt), sulfur (S), tin (Sn), gold (Au), silver (Ag), palladium (Pd), rhenium (Re), rhodium (Rh), and cerium (Ce). These elements may be present in pure form, as oxides, hydroxides, oxide-hydroxides, or phosphides. In addition to the electrocatalytically active element, the electrocatalyst may also contain a support material, such as carbon.

[0065] In alkaline water electrolysis, three electrocatalysts in particular are used: platinum or platinum alloys supported on carbon (Pt / C) or nickel-iron (oxide) hydroxide (NiFe a Ob H c ) or nickel-iron phosphide (NiFe a P b ) has proven to be advantageous, where the indices a, b and c are each real numbers ranging from 0 to 8. Thus, the viscous composition is preferably Pt / C or NiFe a O b H c or NiFe a P b Contains an electrode catalyst.

[0066] Due to their particulate form, electrocatalysts can achieve a large specific surface area. This allows for better access to the catalytically active centers for the reactants, thus improving the reaction efficiency. Furthermore, the electrocatalyst is better utilized in this way, since electrocatalytically active material rarely reaches the interior of the catalyst and remains unused. This allows for a reduction in the material cost of the electrocatalyst, which is particularly interesting for expensive or rare precious metal catalysts. Therefore, a large specific catalytic surface area has many advantages. The specific surface area can be easily increased by using particulate electrocatalysts with particularly fine particle sizes. The finer the particles, the greater the specific surface area. It is also possible to increase the specific surface area of ​​an electrocatalyst by using porous materials.

[0067] The specific surface area of ​​the electrode catalyst is 0.5m 2 / g~2000m 2 / g or 20m 2 / g~200m 2 / g. The specific surface area is determined by the method described by Brunauer-Emmett-Teller (BET method), i.e., nitrogen adsorption. The BET procedure can be performed in an automated manner using commercially available particle analyzers, such as the Micromeritics ASAP 2460 instrument.

[0068] It is preferred to use an anion-conducting polymer comprising at least one structure conforming to any of formulas (I), (II) or (III), [ka]

[0069] In (I), X is C 1 and C 2 and a structural element containing a positively charged nitrogen atom which is bonded to one or two hydrocarbon groups via two bonds, and which contains 1 to 12, preferably 1 to 6, particularly preferably 1 or 5 carbon atoms, In (I), Z is C 3 and C 4 and a structural element comprising carbon atoms, including at least one six-membered aromatic ring directly bonded to one of the oxygen atoms, the six-membered aromatic ring being optionally substituted with one or more halogen groups and / or one or more C1-C4 alkyl groups, [ka]

[0070] In (II), X is C 1 and C 2 and a structural element containing a positively charged nitrogen atom which is bonded to one or two hydrocarbon groups via two bonds, and which contains 1 to 12, preferably 1 to 6, particularly preferably 1 or 5 carbon atoms, In (II), Z is C 3 and C 4 and a structural element comprising carbon atoms bonded to at least one aromatic six-membered ring directly bonded to one of the oxygen atoms, which aromatic six-membered ring may be substituted in the 3- and 5-positions with identical or different C1-C4 alkyl groups, in particular with methyl, isopropyl or tert-butyl groups, preferably with methyl groups, [ka]

[0071] In (III), X is a ketone group or a sulfone group, In (III), Z is a structural element comprising at least one tertiary carbon atom and at least one aromatic six-membered ring, the aromatic six-membered ring being directly bonded to one of the two oxygen atoms; In (III), Y is a structural element containing at least one positively charged nitrogen atom, which nitrogen atom is bonded to the structural element Z.

[0072] Such ionomers are described in EP-A-3770201, EP-A-4032934 and EP-A-4059988. They have good anionic conductivity, are resistant to swelling and are fluorine-free.

[0073] It is preferred that the membrane material and the anion-conducting polymer contain the same repeating units or even be identical. In particular, an ionomer containing at least one of structures (I), (II), or (III) can be used as both the anion-conducting polymer and the membrane material in the composition. This not only improves the adhesion of the electrocatalyst to the membrane, but also facilitates compatibility of the system of the anion-conducting polymer, membrane material, solvent, and anti-swelling agent, since the system is three-dimensional instead of four-dimensional.

[0074] Because the catalyst-containing coating composition hardly swells the AEM due to the anti-swelling agent present in the composition, it can be directly coated onto the membrane without complex fixation, making wrinkle-free processing easier. In particular, the viscous composition can be applied to the anion exchange membrane without using a removable film such as a transfer film or masking film. This avoids waste, especially for fluoropolymers such as PTFE.

[0075] A particular advantage of the viscous compositions described herein is that they cause little, if any, swelling of the anion exchange membrane being coated. Thus, the viscous compositions are particularly suitable for direct coating of AEMs. This means that the step of applying the viscous composition to the ion exchange membrane is performed by applying the viscous composition directly to the anion exchange membrane, i.e., without using a transfer substrate, as is customary in decal methods.

[0076] In particular, when using CMR-free anti-swelling agents, such as cycloheptanone, (1S,5R)-6,8-dioxabicyclo[3.2.1]octan-4-one, cyclohexanone, cyclopentanone, benzonitrile, butanone, acetone, and acetophenone, and CMR-free solvents, such as dimethyl sulfoxide, ethanol, 1-propanol, 2-propanol, and acetonitrile, the manufacturing method according to the present invention allows for production cost savings due to the lower safety requirements for using these substances. Therefore, certain embodiments of the method provide that the solvents and anti-swelling agents are further selected so that they are not designated as carcinogenic, mutagenic, or reproductively toxic. This is the case when the substance is not classified as a CMR substance according to the UN Globally Harmonized System of Classification and Labeling of Chemicals. Table 1 identifies which substances are considered CMR-free. The current version of the GHS is binding in this regard. [Brief explanation of the drawings]

[0077] [Figure 1] FIG. 1 shows a membrane coated with a conventional composition. [Figure 2] FIG. 1 shows a membrane coated with a composition of the present invention. [Figure 3A] FIG. 1 shows a commercially available anion exchange membrane coated with a composition of the present invention. [Figure 3B] FIG. 1 shows a commercially available anion exchange membrane coated with a conventional composition. [Figure 4] FIG. 2 is a diagram showing a current / voltage characteristic line. DETAILED DESCRIPTION OF THE INVENTION

[0078] The advantage of the manufacturing method according to the present invention is that it not only affects the manufacturing cost but also leads to a better product, and experiments have shown that coating with the compositions described herein leads to a better efficiency of the coated AEM, which is due to a better coating quality. Thus, the present invention also provides catalytically coated AEMs that can be obtained by the coating method according to the present invention.

[0079] The anion exchange membrane coated according to the present invention comprises a membrane material and at least one layer containing an electrocatalyst and an anion-conducting polymer, with the electrocatalyst bound to the membrane material via the anion-conducting polymer. Due to the anti-swelling agent present in the composition, the anion exchange membrane coated according to the present invention contains trace amounts of the anti-swelling agent and / or its decomposition products. The trace amounts are residues of the anti-swelling agent that did not completely evaporate during drying. The decomposition products are generated when the anti-swelling agent decomposes. The nature of the trace amounts or decomposition products present in the anion exchange membrane depends on the specific anti-swelling agent used. It is preferred that the AEM coated according to the present invention contain trace amounts or decomposition products of (1S,5R)-6,8-dioxabicyclo[3.2.1]octan-4-one, cyclohexanone, cyclopentanone, cycloheptanone, benzonitrile, butanone, acetone, or acetophenone. The present invention further provides such coated anion exchange membranes.

[0080] The weight fraction of the anti-swelling agent or its degradation products should be expected to be between 0% and 10% by weight, the weight fraction being based on the total weight of the coated anion exchange membrane.

[0081] Since the advantages of the anion exchange membrane coated according to the present invention are particularly evident in AEMWE, i.e., in improving efficiency, the present invention further provides the use of the catalytically coated anion exchange membrane according to the present invention in alkaline water electrolysis. It is used when alkaline water electrolysis is carried out in the presence of a catalytically coated anion exchange membrane. The electrocatalyst present in the coating catalyzes alkaline water electrolysis. The coating can simultaneously function as an electrode. The membrane and ionomer present in the coating convert hydroxide ions OH - is transported from the cathode compartment to the anode compartment of the electrochemical cell. [Example]

[0082] A method for producing a catalytically coated AEM using a platinum / carbon-based viscous composition is described below, thus experimentally verifying the effects achieved by the present invention.

[0083] 1. Preparation of Ionomers (not part of this invention) An anion-conducting cationic polymer was synthesized according to Example 3 of EP 3770201. The polymer was first prepared as a solution and then processed into a powder by drying. The dried polymer was then further dried in a vacuum drying cabinet at 80 °C for 48 h to minimize residual solvent content.

[0084] The dry powder was used to prepare two different ionomer solutions used in the following examples.

[0085] 1.1 Preparation of 20% Ionomer Solution (Not Part of This Invention) First, a 20% ionomer solution was prepared by mixing 20 parts by weight of dry polymer powder with 80 parts by weight of DMSO. The mixture was first heated to 60°C in a sealed container and then shaken using a nutating mixer for 24 hours until the polymer was completely dissolved.

[0086] 1.2 Preparation of 12% Ionomer Solution (Not Part of the Invention) Next, a 12% ionomer solution was produced by further diluting the previously prepared 20% solution to 12% by weight by adding equal weight fractions of acetonitrile and ethanol. The mass fractions in the solution were 12 parts by weight of polymer, 48 parts by weight of DMSO, and 20 parts by weight of acetonitrile and ethanol in each case. To ensure complete mixing, the sealed container was also shaken for 24 hours using a natating mixer.

[0087] 2. Experiments on the solubility of ionomers in ethanol, 1-propanol and 2-propanol For this purpose, three containers were prepared: the first containing 27 g of ethanol, the second 27 g of 1-propanol, and the third 27 g of 2-propanol. 3 g of the cationic polymer powder synthesized in Example 1 was added to each of these containers, and the containers were sealed and shaken for 4 hours at 60° C. This resulted in the formation of a slightly swollen and softened polymer mass at the bottom of each container, which was barely dissolved.

[0088] 3. Experiment on the solubility of ionomers in acetonitrile For this purpose, 3 g of the cationic polymer powder synthesized from Example 1 was added to a vessel containing 27 g of acetonitrile, and the resulting mixture was shaken for 4 hours at 60° C. Again, no significant dissolution of the polymer was observed.

[0089] 4. Experiments on the solubility of ionomers in mixtures of ethanol or 1-propanol or 2-propanol in combination with acetonitrile For this purpose, three containers were prepared: the first containing 13.5 g of ethanol and 13.5 g of acetonitrile, the second containing 13.5 g of 1-propanol and 13.5 g of acetonitrile, and the third containing 13.5 g of 2-propanol and 13.5 g of acetonitrile. 3 g of the cationic polymer powder synthesized in Example 1 was added to each of these containers, and the containers were shaken at 60°C for 4 hours. The result was a substantially clear solution. The polymer was dissolved in all three containers.

[0090] 5. Interim findings: solubility behavior of ionomers The ionomers investigated are soluble in the solvent mixtures ethanol and acetonitrile, but not in ethanol or acetonitrile alone, as well as in mixtures of 1-propanol and acetonitrile and 2-propanol and acetonitrile.

[0091] 6. Fabrication of Anion Exchange Membranes (Not Part of the Invention) The cationic polymer synthesized in Example 1 was used to prepare an anion-conducting membrane as described in Example 4 of EP 3770201. The polymer solution was used before drying.

[0092] 7. Provision of compositions without anti-swelling agents (not part of the present invention) A viscous composition was prepared using the cationic polymer synthesized in Example 1 as described in Example 12 of WO2023088714.

[0093] The ionomer was first dissolved in dimethyl sulfoxide with stirring and at a temperature of 60°C for 16 hours. Subsequently, a platinum-on-charcoal (Pt / C, approximately 50 wt%) catalyst was dispersed in a dispersion medium composed of equal volume fractions of water and ethanol using an ultrasonic wave (BRANSONIC™ B-1200 E2, Branson Ultrasonics Corporation, Brookfield, Connecticut, USA) at 30 W power for 30 minutes in an ice bath. Following the addition of the ionomer solution, the mixture was further dispersed using an ultrasonic wave at 30 W for 1 minute in an ice bath and then dispersed using a shaker (MS1 Minishaker, IKA, Staufen, Germany) at 2500 rpm for 10 seconds. The contents were selected according to Table 1, Example 12. This resulted in a solids content of 11 mg / ml, a Pt / C catalyst particle content of 3 parts by weight, and an ionomer solids content of 1 part by weight. This resulted in a low-viscosity composition.

[0094] 8. Provision of a composition containing an anti-swelling agent (part of the present invention) A catalyst-containing ink (20.9 g) was prepared as a composition of the present invention. To this end, 3 g of Pt / C (approximately 50 wt. % Pt) was weighed into a splash-proof container (100 ml capacity) under an oxygen-free atmosphere, followed by the addition of 8.6 g of (1S,5R)-6,8-dioxabicyclo[3.2.1]octanon-4-one (Cyrene®, Sigma-Aldrich, Germany), 0.5 g of DMSO, 1 g of ethanol, 1 g of acetonitrile, and 4.3 g of cyclopentanone. Finally, 30 g of yttrium-stabilized zirconium grinding balls were added. The mixture was dispersed in a shaker mixer (Lau, Germany) for 2 hours. 2.5 g of ionomer solution (20 wt. % in DMSO—Example 1.1) was then added, and the mixture was finally shaken in a shaker mixer for 5 minutes.

[0095] In this example, DMSO, EtOH, and ACN form the solvent mixture. Cyrene® and cyclopentanone form the anti-swelling agent mixture.

[0096] 9. Coating of the membrane with a conventional composition without an anti-swelling agent (not part of this invention) For a reference experiment using the conventional formulation from WO2023088714, Example 12, the composition provided in Example 7 was applied to the membrane prepared in Example 6 using an automatic bar coater (Elcometer 4340, forward speed 5 mm / s, spiral bar coater, 60 μm). The coated membrane was then dried in a laboratory oven at 80° C. for 15 minutes, resulting in a CCM as shown in FIG. 1.

[0097] Figure 1: Membrane coated with conventional composition.

[0098] During coating, the film became severely wavy, resulting in an uneven coating, but is nevertheless in principle suitable as an electrode for water electrolysis.

[0099] 10. Coating of the membrane with a composition containing an anti-swelling agent (part of the present invention) For direct coating of the present invention using an anti-swelling agent-containing formulation, the composition provided in Example 8 was applied to the membrane prepared in Example 6 using an automatic bar coater (Elcometer 4340, forward speed 5 mm / s, spiral coating bar, 60 μm). The coated membrane was then dried in a laboratory oven at 80° C. for 15 minutes, resulting in a CCM as shown in FIG. 2.

[0100] FIG. 2: Membrane coated with a composition of the present invention.

[0101] During coating, the membrane rippled only at the edges, resulting in a uniform coating suitable for use as an electrode for water electrolysis.

[0102] 11. Coating of Commercially Available Membranes with Compositions Containing Anti-Swelling Agents (Part of the Invention) 23.5 g of catalyst-containing ink was prepared as a composition of the present invention. For this purpose, 3 g of Pt / C (approximately 50% by weight of Pt) was first weighed into a splash-proof container (100 ml capacity) under an oxygen-free atmosphere, followed by the addition of 18.0 g of cyclopentanone. Finally, 30 g of yttrium-stabilized zirconium grinding balls were added. The mixture was dispersed in a shaker mixer (manufactured by Lau, Germany) for 2 hours. Next, 3.0 g of the 12% ionomer solution described in 1.2 was added (12% polymer, 48% DMSO, 20% ethanol, 20% acetonitrile), and finally, the mixture was shaken in a shaker mixer for 5 minutes.

[0103] In this example, DMSO, EtOH and ACN form the solvent mixture. The anti-swelling agent is cyclopentanone.

[0104] For direct coating of the present invention using the antiswelling agent-containing formulation, the composition described in this example was applied to a commercially available anion exchange membrane (FAA-3-50, manufactured by Fumatech BWT GmbH, Germany) using an automatic bar coater (Elcometer 4340, forward speed 5 mm / s, spiral coating bar, 60 μm). The coated membrane was then dried in a laboratory oven at 80° C. for 15 minutes. This resulted in a CCM as shown in FIG. 3A.

[0105] FIG. 3A: Commercially available anion exchange membrane coated with a composition of the present invention.

[0106] During coating, the membrane rippled only at the edges, resulting in a uniform coating suitable for use as an electrode for water electrolysis.

[0107] 12. Coating of commercially available alternative membranes with conventional compositions without anti-swelling agents (not part of this invention) A non-inventive composition, 10.0 g of catalyst-containing ink, was prepared. For this purpose, 2.0 g of Pt / C (approximately 50% by weight of Pt) was weighed into a splash-proof container (100 ml capacity) under an oxygen-free atmosphere, followed by the addition of 3.0 g of water, 1 g of DMSO, and 4.0 g of the 12% ionomer solution described in 1.2 (12% polymer, 48% DMSO, 20% ethanol, 20% acetonitrile). Finally, 30 g of yttrium-stabilized zirconium grinding balls were added. The mixture was dispersed in a shaker mixer (manufactured by Lau, Germany) for 2 hours.

[0108] In this example, DMSO, EtOH and ACN form a solvent mixture. No anti-swelling agent was used.

[0109] For direct coating, which is not the present invention, the formulation described in this example was applied to a commercially available anion exchange membrane (FAA-3, Fumatech BWT GmbH, Germany) using an automatic bar coater (Elcometer 4340, forward speed 5 mm / s, spiral bar coater, 60 μm). The coated membrane was then dried in a laboratory oven at 80° C. for 15 minutes. This resulted in a CCM as shown in FIG. 3B.

[0110] Figure 3B: Commercially available anion exchange membrane coated with conventional composition.

[0111] In coating, the film exhibits a much greater degree of waviness compared to the film shown in Figure 3A, resulting in a less uniform coating.

[0112] 13. Testing the coated membrane in an electrolytic test cell The catalytically coated membranes from Examples 9 and 10 were placed on a 25 cm 2 The electrolysis was performed in an electrolysis cell with an active area of ​​1000 kJ / cm². The catalyst layer served as the cathode catalyst. A dimensionally stable porous stainless steel electrode was used on the anode side. During the electrolysis experiments, the measuring cell was heated to 60 °C and a 1 M KOH solution was passed through the anode and cathode sides. The current-voltage characteristic curves are shown in Figure 4. The relevant legends can be found in Table 3.

[0113] Figure 4: Current / voltage characteristic curve

[0114] [Table 3]

[0115] In the graph, the required voltage is plotted against the externally applied current intensity. 2 ), lower voltages are preferred because they reduce the electrical energy required to produce the same amount of hydrogen at the same production rate, thus increasing efficiency. Current intensities of particular relevance for industrial applications are 500 mA / cm 2It is clear that at higher current densities for the CCM made according to the present invention, the current-voltage characteristic curve is lower than that of the CCM made for reference (not according to the present invention). At lower current densities, the power consumption is lower at the same voltage, and therefore the specific energy demand of the CCM made according to the present invention is lower.

[0116] 14. Conclusion A comparison of the current-voltage characteristic curves in Figure 4 reveals that the CCMs prepared according to the present invention using the anti-swelling agent-containing composition achieve higher efficiency in alkaline water electrolysis than the CCMs coated with the conventional anti-swelling agent-free composition. The higher efficiency can be attributed to the fact that the coating was more uniform and that a somewhat thicker catalyst layer could be applied as a result of the increased viscosity.

[0117] Supplementary Materials

[0118] [Table 1]

[0119] * CMR Classification according to GHS08. CMR classification data is for the purposes of this application only. Substances with a CMR status of "none" are not necessarily safe. These data cannot be used to justify actions or omissions, especially in relation to legislation governing hazardous substances.

Claims

1. 1. A method for producing a coated anion exchange membrane, comprising the following non-chronological steps: a) at least the following ingredients: i) an electrocatalyst; ii) a solvent; and iii) an anion conducting polymer; providing a viscous composition comprising: b) providing an anion exchange membrane comprising at least one membrane material; c) applying the viscous composition to the anion exchange membrane; d) drying the viscous composition applied to the anion exchange membrane; e) obtaining a coated anion exchange membrane comprising, on at least one side thereof, a layer comprising the electrocatalyst and the anion-conducting polymer, wherein the electrocatalyst is bonded to the membrane material via the anion-conducting polymer; the anion-conducting polymer, the membrane material, and the solvent are selected to be compatible with each other such that the anion-conducting polymer and the membrane material are each soluble in the solvent; The viscous composition comprises the following components: iv) an organic substance different from the solvent, Hansen solubility parameters δD, δP and δH are in the following ranges: 15MPa ０．５ <δD<35MPa ０．５ 6MPa ０．５ <δP<15MPa ０．５ 2.5MPa ０．５ <δH<7.1MPa ０．５ 3. The method of claim 1, further comprising the step of:

2. 2. The method of claim 1, wherein the organic substance is selected from the group consisting of the following substances: (1S,5R)-6,8-dioxabicyclo[3.2.1]octan-4-one, cyclopentanone, cyclohexanone, cycloheptanone, benzonitrile, acetone, butanone, and acetophenone.

3. 3. The method according to claim 1 or 2, characterized in that the solvent is selected from the group consisting of the following substances: dimethyl sulfoxide, ethanol, methanol, 1-propanol, 2-propanol, acetonitrile.

4. 4. The method of claim 3, wherein the solvent is a solvent mixture containing two or more substances selected from the listed group.

5. 5. The method according to claim 1, wherein the anion-conducting polymer is completely dissolved in the solvent or solvent mixture.

6. 6. The method of any one of claims 1 to 5, characterized in that the electrocatalyst is in particulate form and contains at least one element selected from the group consisting of the following elements: iridium (Ir), nickel (Ni), cobalt (Co), chromium (Cr), iron (Fe), ruthenium (Ru), copper (Cu), molybdenum (Mo), zinc (Zn), lead (Pb), manganese (Mn), tungsten (W), platinum (Pt), sulfur (S), tin (Sn), gold (Au), silver (Ag), palladium (Pd), rhenium (Re), rhodium (Rh), cerium (Ce), wherein the element is present in its pure form, or as an oxide, or as a hydroxide, or as an oxide-hydroxide, or as a phosphide.

7. The electrode catalyst is platinum or platinum alloy supported on carbon (Pt / C) or nickel-iron (oxide) hydroxide (NiFe ａ O ｂ H ｃ ) or nickel-iron phosphide (NiFe ａ P ｂ ) and the exponents a, b and c are each real numbers in the range of 0 to 8.

8. The viscous composition comprises the following components: v) a dispersion medium, 8. The method of claim 1, further comprising the dispersion medium being neither the same as the solvent or solvent mixture nor the organic substance.

9. 9. The method of claim 8, wherein the dispersion medium is water.

10. 10. The method according to any one of claims 1 to 9, characterized in that the weight fractions of the components are in the following ranges, in each case based on the total weight of the viscous composition, with the proviso that the sum of the weight fractions of all components listed therein does not exceed 100% by weight:

11. 11. The method of any one of claims 1 to 10, additionally comprising at least one additive, said additive being selected from the group consisting of the following additives: rheological aids, conductive additives.

12. 12. The method of claim 11, wherein the additive is silica or carbon black.

13. The viscous composition has a dynamic viscosity η, the characteristic value of which is determined according to the method defined herein, and the characteristic value of the dynamic viscosity η is between 10 mPas and 10 ４ 13. The method according to claim 1, wherein the viscosity is 0.05 MPa.

14. 14. The method of any one of claims 1 to 13, wherein the anion-conducting polymer comprises at least one structure conforming to any of formulas (I), (II), or (III): [Chemical (I)] In (I), X is C １ and C ２ and a positively charged nitrogen atom bonded to one or two hydrocarbon groups via two bonds, which contains 1 to 12, preferably 1 to 6, particularly preferably 1 or 5 carbon atoms, In (I), Z is C ３ and C ４ and at least one aromatic six-membered ring bonded directly to one of the oxygen atoms, said aromatic six-membered ring being １ ~C ４ may be substituted with an alkyl group, 【Chemistry (II)】 In (II), X is C １ and C ２ and a positively charged nitrogen atom bonded to one or two hydrocarbon groups via two bonds, which contains 1 to 12, preferably 1 to 6, particularly preferably 1 or 5 carbon atoms, In (II), Z is C ３ and C ４ and a structural element comprising a carbon atom bonded to at least one aromatic six-membered ring directly bonded to one of the oxygen atoms, said aromatic six-membered ring having the same or different C １ ~C ４ may be substituted with alkyl groups, in particular methyl, isopropyl or tert-butyl groups, preferably methyl groups, 【Chemistry (III)】 In (III), X is a ketone group or a sulfone group; In (III), Z is a structural element comprising at least one tertiary carbon atom and at least one aromatic six-membered ring, said aromatic six-membered ring being directly bonded to one of the two oxygen atoms; In (III), Y is a structural element containing at least one positively charged nitrogen atom, said nitrogen atom being bonded to said structural element Z.

15. 15. The method according to any one of claims 1 to 14, characterized in that the membrane material and the anion-conducting polymer have the same repeating units or are identical.

16. 16. The method according to any one of claims 1 to 15, characterized in that neither the solvent or the solvent mixture nor the organic substance is carcinogenic, mutagenic or reproductively toxic.

17. c) applying the viscous composition to the anion exchange membrane, by applying the viscous composition directly to the anion exchange membrane, i.e., without using a transfer substrate; 17. The method of any one of claims 1 to 16.

18. 18. The method of any one of claims 1 to 17, wherein the anion-conducting polymer, the membrane material and the organic substance are selected to be compatible with each other such that the anion-conducting polymer and the membrane material are each insoluble in the organic substance.

19. A coated anion exchange membrane comprising a membrane material and at least one layer comprising an electrocatalyst and an anion-conducting polymer, wherein the electrocatalyst is bound to the membrane material via the anion-conducting polymer, and the coated anion exchange membrane contains trace amounts of substances selected from the group consisting of the following substances: (1S,5R)-6,8-dioxabicyclo[3.2.1]octan-4-one, cyclopentanone, cyclohexanone, cycloheptanone, benzonitrile, acetone, butanone, and acetophenone.

20. 20. The coated anion exchange membrane according to claim 19, wherein the weight fraction of the trace amount based on the total weight of the coated anion exchange membrane is 0% to 10% by weight.

21. 21. A coated anion exchange membrane according to claim 19 or 20, obtainable by a method according to any one of claims 2 to 18.

22. 22. Production of hydrogen and oxygen by alkaline water electrolysis, characterized by the presence of a coated anion exchange membrane according to claim 19, 20 or 21.

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