Production of electrocatalytically active layered bodies with anion conductivity

Abstract

The invention relates, inter alia, to an electrocatalytically active layered body, to the production thereof and to the use thereof as an anion exchange membrane in alkaline water electrolysis. The problem addressed was that of producing a catalytically active anion exchange membrane on an industrial scale without distortion. Said anion exchange membrane is intended to be stable under alkaline conditions, to have good conductivity for hydroxide ions and to make it possible to carry out alkaline membrane water electrolysis with high efficiency. Production is intended to be carried out without the use of fluoropolymers, and as far as possible CMR substances should not be used. In the method described here, a layer of an ionomer which has a conductivity for OH− is applied to a catalytically active substrate. The ionomer layer forms the later membrane and the substrate forms the catalyst layer. An essential aspect of the method is that the catalytically active substrate, which is coated with the ionomer, is provided with dissolvable structure-forming agents. These substances can be leached or washed out of the catalyst layer, thereby leaving pores. The invention also relates to a not yet leached-out or washed-out precursor of the layered body.

Description

[0001] Production of electrocatalytically active composites with anion conductivity

[0002] The invention relates to an electrocatalytically active or activatable laminated body, its production, and its use as an anion exchange membrane. Furthermore, the invention relates to a precursor of the laminated body, which is passed through during its production. Furthermore, the invention relates to an electrolyzer incorporating the laminated body or its precursor. Finally, the invention relates to a process for producing hydrogen and oxygen by electrolysis of water in an alkaline environment in the presence of the laminated body or its precursor.

[0003] Catalytically coated membranes (CCMs) are laminated bodies comprising at least a first layer of an ion-conducting polymer (ionomer) and at least a second layer of an electrocatalytically active or activatable material (electrocatalyst). The first layer serves as the membrane, the second layer as the catalyst. There is direct contact between the ionomer layer and the electrocatalyst layer. In some cases, the adjacent layers merge into one another. CCMs are used in electrochemical cells, such as fuel cells or electrolyzers. The chemical nature of the electrocatalyst and ionomer depends on the intended application of the electrochemical cell.

[0004] One application is water electrolysis to produce hydrogen and oxygen (water splitting).

[0005] One variant of water splitting is alkaline membrane water electrolysis. It is important that the membranes exhibit good conductivity for hydroxide anions (OH). This conductivity is achieved through anion-conducting polymers. The membranes made from these ionomers are therefore called anion exchange membranes (AEM). Since the reaction takes place in an alkaline environment, the AEM must be stable under basic conditions. Alkaline membrane water electrolysis is also often called AEM-based water splitting (AEMWE).

[0006] An excellent overview of the structure and materials of the electrochemical cells currently used in AEM-based water splitting is provided by:

[0007] 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.

[0008] As described by Miller in section 5.2 of his above-cited review, catalytically coated membranes COM are also used in the AEMWE.

[0009] CCM is traditionally produced—as the name suggests—by coating an uncoated membrane made of an ion-conducting polymer with a catalytically active layer. The catalytically active layer is usually applied to the ionomer layer in the form of a catalyst ink. The catalyst ink typically contains the electrocatalyst, a binder, as well as solvent and dispersing media. The binder is dissolved in the solvent. The solvent and dispersing media dry after the ink is applied, leaving the electrocatalyst and the now undissolved binder on the membrane, forming the electrocatalytically active layer. The binder forms a solid matrix that immobilizes the electrocatalyst in the layer and on the membrane. Solvent-soluble polymers are usually used as binders, often including those that are ionically conductive like the membrane.

[0010] A corresponding process for producing a COM usable in the AEMWE is described, for example, in WO2023088714A1.

[0011] Such an approach involves various technical difficulties: Among other things, it is important to ensure that the catalyst ink applied to the membrane does not attack the membrane. In particular, solvents contained in the ink can swell the ionomer contained in the membrane, making application more difficult, or distort the membrane so severely that it is almost impossible to install or seal in a cell.

[0012] The membrane's shape change is caused by the solvent contained in the ink (e.g., water or methanol) penetrating the membrane material, causing it to swell. As the solvent mixture penetrates the membrane material, the membrane's volume increases during coating, creating mechanical stresses in the interface between the catalyst and the membrane, which distort the coated membrane as a whole. In extreme cases, the coated membrane wrinkles. Incorporating a distorted or even wrinkled CCM into an electrochemical cell would then be virtually impossible.

[0013] To counteract this, the working group led by Susanne Koch developed a process for coating AEM in which the membrane is protected against distortion during coating by a mask:

[0014] 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.

[0015] Here, a flat, anion-conducting membrane is first masked with a PTFE film, and the exposed areas are then directly coated with a catalyst ink. A protective film, also made of PTFE, is then applied. The mask serves to absorb stresses in the membrane, preventing excessive distortion during the coating process.

[0016] The disadvantage of the process proposed by Koch et al. is that it requires the masking film to prevent the membrane from swelling and ultimately wrinkling. The mask is used exclusively for the production of the CCM and must be removed once the CCM is ready for use. Since the mask is made of the fluoropolymer PTFE, discarding it is unacceptable from an environmental perspective. Furthermore, the process still requires a great deal of manual labor and does not yet appear to be scalable from an industrial perspective. Furthermore, the catalyst ink used by Koch et al. contains methanol as a solvent. Since methanol is known to be carcinogenic, mutagenic, or toxic to reproduction, this solvent is classified as a CMR substance under the REACH regulation, which requires appropriate safety measures during its processing. This is not a major problem in the laboratory; however, on an industrial production scale, it is very complex and correspondingly costly.

[0017] Breitwieser et al., however, have pointed to a process called “direct membrane deposition” (DMD), in which not the catalytically active layer is applied to the membrane, but conversely a membrane is applied to a catalytically active substrate (Section 2.5; Figure 1d):

[0018] M. Breitwieser, M. Klingele, S. Vierrath, R. Zengerle, S. Thiele: Tailoring the Membrane-Electrode Interface in PEM Fuel Cells: A Review and Perspective on Novel Engineering Approaches. Adv. Energy Mater. 2018, 8, 1701257., DOI: 10.1002 / aenm.201701257.

[0019] However, the CCMs described by Breitwieser et al., produced using the DMD process, are exclusively proton exchange membranes (PEMs) made of the proton-conducting fluoropolymer Nation®. These CCMs cannot be used in alkaline water electrolysis because they do not exhibit significant conductivity for hydroxide anions (OH). Furthermore, the PEM CCMs are also intended for use in fuel cells, i.e., for water synthesis and not for water splitting.

[0020] Similarly, Xing et al. describe the fabrication of a membrane electrode assembly (MEA) for a PEM fuel cell. A catalyst layer (CL) containing platinum supported on carbon (Pt / C) is first sprayed onto a gas distribution layer (GDL). An ionomer solution (Nation® in n-propanol) is then sprayed onto the catalyst layer. The still-liquid Nafion® layer is used to bond the MEA:

[0021] Yijing Xing, Lei Liu, Zhiyong Fu, Yifan Li, and Haibin Li: Preparation of an Integrated Membrane Electrode Assembly for Proton Exchange Membrane Fuel Cells Using a Novel Wet-Bonding Strategy. Energy & Fuels 2023 37 (16), 12360-12368 DOI: 10.1021 / acs.energyfuels.3c01800.

[0022] The resulting MEA cannot be used in alkaline water electrolysis because the ionomers used (Nation®) conduct protons but not hydroxide ions. The same applies to the fully coated membrane electrode assembly (CC-MEA) proposed by Stähler et al., which is constructed entirely using a slotted die and is also intended for PEM water electrolysis:

[0023] Markus Stähler, Andrea Stähler, Fabian Scheepers, Marcelo Carmo, Detlef Stolten:

[0024] A completely slot the coated membrane electrode assembly. International Journal of Hydrogen Energy, Volume 44, Issue 14, 2019, Pages 7053-7058, DOI: 10.1016 / j.ijhydene.2019.02.016.

[0025] European patent application 24152389.3, still unpublished at the time of filing, relates to a process for producing CCM for AEMWE, in which a catalyst layer is applied to an anion-conducting membrane. The surface of the catalyst layer is geometrically undefined. Porosity is imparted to the catalyst layer using dissolvable structuring agents.

[0026] In light of this state of the art, the task is to produce an electrocatalytically active or activatable anion exchange membrane on an industrial scale without distortion. The resulting anion exchange membrane should be stable under basic conditions, exhibit good conductivity for hydroxide ions, and enable alkaline membrane water electrolysis with high efficiency. The production should be carried out without the use of fluoropolymers and, if possible, avoid CMR substances.

[0027] The object is achieved by a method for producing a catalytically active or catalytically activatable layered body, comprising the following steps: a) providing a transfer substrate; b) providing a catalyst ink containing at least a first solvent, at least one polymer dissolved in the first solvent, at least one particulate electrocatalyst that is electrocatalytically active or activatable, and at least one particulate inorganic material different from the electrocatalyst; c) applying the catalyst ink to the transfer substrate so that a fresh catalyst layer is formed on the transfer substrate;d) depleting the first solvent from the fresh catalyst layer so that a solid catalyst layer is formed on the transfer substrate, said solid catalyst layer comprising at least three phases, namely a first phase formed by the now undissolved polymer, a second phase formed by the particulate electrocatalyst, and a third phase formed by the particulate inorganic material, wherein the second phase and the third phase are dispersed in the first phase; e) optionally: separating the transfer substrate from the solid catalyst layer; f) providing an ionomer solution containing at least a second solvent and at least one anion-conducting polymer dissolved in the second solvent; g) applying the ionomer solution to the fresh or solid catalyst layer so that a fresh ionomer layer is formed on the fresh or solid catalyst layer;h) Depleting the second solvent from the fresh ionomer layer so that a solid ionomer layer is formed on the catalyst layer, in which the now undissolved anion-conducting polymer is enriched; i) Providing an aqueous alkaline solution containing at least one alkali metal selected from the group consisting of sodium, potassium, and lithium; k) If this has not already been done: separating the transfer substrate from the solid catalyst layer; l) Applying the aqueous alkaline solution to the solid catalyst layer; m) Reacting at least a portion of the inorganic material with the alkaline solution to form a product within the solid catalyst layer; n) Washing out at least a portion of the product from the solid catalyst layer; o) Obtaining the electrocatalytically active or activatable laminated body, wherein the laminated body comprises the washed-out solid catalyst layer and the solid ionomer layer applied thereto.

[0028] Although individual procedural steps require the completion of a previous procedural step, this list of steps is not intended to be chronological: As described below, some steps may occur in a different chronological order than listed above, or even simultaneously. More on this later.

[0029] In the process according to the invention, a layer of an ionomer with OH- conductivity is applied to a catalytically active or activatable substrate. The ionomer layer forms the future membrane, and the substrate forms the catalyst layer. The resulting laminate is therefore a membrane-coated catalyst layer (MCCL) rather than a catalytically coated membrane (CCM).

[0030] The catalyst layer is obtained by coating an electrocatalytically inert transfer substrate with catalyst ink. The transfer substrate is a material that is insoluble in the first solvent and is preferably flat, i.e., essentially two-dimensional, such as a plate made of glass or polyethylene terephthalate (PET). Alternatively, a film or a textile fabric can be used as the transfer substrate. Both are flexible compared to a rigid plate and allow processing in a streamlined roll-to-roll process. The film and textile fabric are preferably made of PET. Textile fabrics such as woven fabrics or nonwovens are generally porous, which facilitates the drying of the catalyst ink.

[0031] After the ink dries, a solid catalyst layer forms on the transfer substrate. The transfer substrate will eventually be removed from the catalyst layer. It will not become part of the final composite.

[0032] Although the transfer substrate does not form part of the final layered body, it is nevertheless highly relevant for the layered body: Since the amorphous catalyst ink is applied to the transfer substrate and solidifies there to form the catalyst layer, the catalyst layer at the interface to the transfer substrate assumes the geometric shape predetermined by the transfer substrate. If the transfer substrate is a glass plate, for example, the catalyst layer receives a flat surface, which then becomes visible as soon as the transfer substrate is detached from the catalyst layer. Since this surface is no longer coated with ionomer, the shape of the catalyst layer predetermined by the transfer substrate is retained, so that the later final layered body still has this shape. In this way, it is possible to specify the surface of the catalyst layer through the shape of the transfer substrate.

[0033] Transferring the shape of the transfer substrate to the surface of the catalyst layer is a primary forming process within the meaning of DIN 8580:2022-12, so that the surface of the catalyst layer of the laminated body produced according to the invention is primary formed. In this context, it should be noted that the production of the catalyst layer is not a coating process within the meaning of the aforementioned standard, since the transfer substrate is coated here, which does not form part of the workpiece (i.e., the laminated body). However, the conventional production of a CCM is considered a coating process within the meaning of the standard, because the coated substrate, namely the catalytically coated membrane, represents the workpiece itself.

[0034] Key steps of the process are g) applying the ionomer solution to the fresh or solid catalyst layer, so that a fresh ionomer layer is formed on the fresh or solid catalyst layer; h) and depleting the second solvent from the fresh ionomer layer, so that a solid ionomer layer is formed on the catalyst layer, in which the now undissolved anion-conducting polymer is enriched. This means that the solid ionomer layer, which forms the later membrane, only forms on the fresh or solid catalyst layer. The membrane material is therefore contacted with the catalyst layer in dissolved form, namely as an ionomer solution. The solid membrane is only formed on the catalyst layer and not before contact with the catalyst layer. In this respect, the process according to the invention differs from conventional COM orhot press processes in which the catalyst layer is contacted with an already solid ionomer layer or membrane.

[0035] Another key aspect of the process is that the catalytically active substrate, which is coated with the ionomer, is equipped with soluble structuring agents. These soluble structuring agents are particulate inorganic materials, such as silica and / or alumina powders. These substances leach or wash out of the catalyst layer, leaving pores. The structuring agents thus act as placeholders for the later pores. Since the catalyst layer is not yet porous when coated with the ionomer, the dissolved ionomer hardly penetrates the catalyst layer.Since the pores in the catalyst layer are only created after the ionomer layer has solidified by leaching / washing out the structure-forming agents, the catalytically active centers of the electrocatalyst are easily accessible to the electrolyte penetrating the pores during electrolysis, so that water splitting can be carried out efficiently.

[0036] A further advantage of the process is that the ionomer is applied in dissolved form and therefore stress-free. This counteracts membrane distortion.

[0037] Another advantage of the process is that it can be performed without the use of auxiliary films for masking, which are later discarded. This avoids waste. Since no auxiliary films need to be manipulated, industrial-scale production is also comparatively easy. The transfer substrate can be recycled.

[0038] The laminated body produced by this process comprises at least two layers, each of which can be applied in multiple layers if necessary. The layers differ in their material composition, while the individual layers of each layer consist of the same material. The ionomer layer forms the actual anion-conducting membrane, and the catalyst layer is the catalytically active material.

[0039] Both layers are applied with fresh catalyst ink or ionomer solution and then solidified by removing the respective solvent, and in the simplest case, dried. Unlike conventional CCM production, the ionomer layer, which later forms the membrane, is solidified on top of the catalyst layer. Therefore, the catalyst layer is coated with the membrane, rather than the membrane with the catalyst layer.

[0040] The composite can be constructed in two basic ways: In the first variant, the ionomer layer is applied to the catalyst layer only after the catalyst layer has dried. Accordingly, the ionomer solution is applied to the solid catalyst layer and the first solvent is removed from the fresh catalyst layer before the second solvent is removed from the fresh ionomer layer.

[0041] In a second variant, the ionomer layer is applied to the still fresh catalyst layer before it has dried. The removal of the first solvent from the fresh catalyst layer and the removal of the second solvent from the fresh ionomer layer can then even occur simultaneously. Simultaneous drying of both layers is particularly time-saving. It is also possible to dry the ionomer layer first and then the catalyst layer. It is also conceivable to apply both layers simultaneously, for example, using a double slot die.

[0042] Once the two layers have been built up and solidified in any order, a precursor of the later laminated body is obtained, which is characterized by the fact that its catalyst layer still contains the particulate inorganic material, which is different from the also particulate electrocatalyst.

[0043] The precursor must be separated from the transfer substrate. This can be done at the earliest after the catalyst layer has solidified, but can also be done after the ionomer layer has solidified.

[0044] The precursor is then subjected to a forming process, during which the particulate inorganic material is removed from the catalyst layer, leaving pores in the catalyst layer. The inorganic material is removed by leaching with alkali hydroxide followed by washing.

[0045] More specifically, the formation process begins with the precursor catalyst layer being brought into contact with the aqueous alkaline solution (leaching). This converts the inorganic particulate material within the solid catalyst layer into a leachable product. The leachable product formed during leaching depends on the choice of inorganic material and the alkali.

[0046] Silicon dioxide (silica - SiO2) and aluminum oxide (alumina - Al2O3), as well as mixtures thereof (silica / alumina), are particularly suitable as particulate inorganic materials. A suitable aqueous alkaline solution is a sodium, potassium, or lithium lye, or a mixture thereof.

[0047] If silicon dioxide is used as the particulate inorganic material and potassium hydroxide (KOH) as the alkali, the particulate silicon dioxide (SIO2) present in the catalyst layer of the precursor is converted to the products potassium silicate (K2SiO2) and water (H2O):

[0048] SiO2+ 2 KOH -> K2SiO3+ H2O (1) The product potassium silicate is water-soluble and can be easily washed out of the catalyst layer.

[0049] The product water anyway.

[0050] If another alkali metal is used for leaching instead of potassium, such as lithium or sodium, lithium silicate or sodium silicate is formed analogously to formula (1).

[0051] If aluminum oxide (Al2O3) is used as the particulate inorganic material, water-soluble aluminates form with the alkali. For example, if sodium hydroxide (NaOH) is used as the alkali, the product sodium aluminate (NaAl(OH)4) is formed according to formula (2):

[0052] AI2O3 + 2 NaOH + 3 H2O 2 NaAI(OH)4(2)

[0053] Sodium aluminate is water-soluble and can be easily washed out.

[0054] It is also possible to use particulate silica and particulate alumina simultaneously, or even mixed phases of the two. In this case, the reactions described above occur in parallel during leaching, and several products are obtained in parallel.

[0055] The silicates and / or aluminates remaining in the catalyst layer after leaching can then be washed out of the catalyst layer using an aqueous solution, thus imparting porosity to the catalyst layer. The polymer and the particulate electrocatalyst contained in the catalyst layer remain unaffected by the leaching and washing processes and ultimately form the catalytically active layer of the finished laminate. The original shape of the catalyst layer is also retained by the forming process, particularly because the polymer matrix is ​​not altered. However, the forming process creates open pores in the surface, namely in the areas previously occupied by the inorganic particulate material. However, the pores always open within the shape of the catalyst layer determined by the original forming process.

[0056] The resulting composite differs from conventional CCMs, particularly in the pre-formed surface of its catalyst layer: Since in CCMs, the catalyst ink is applied to the membrane, which remains part of the CCM, the catalyst ink lacks a predetermined shape on the side of the catalyst layer facing away from the membrane. Consequently, the catalyst layer of a CCM is always irregular and not geometrically determined.

[0057] Another advantage of the process is that the shape of the catalyst layer of the laminated body can be relatively easily specified by the shape of the transfer substrate: If a flat transfer substrate with a high surface quality is used, the catalyst layer also has a high level of planarity and low roughness. This is an advantage if the laminated body is later used as a catalytically active anion exchange membrane in an electrochemical cell, because it improves the electrical contact between the catalyst layer and the adjacent electrodes, which are generally also flat. Furthermore, it is possible to preshape the surface of the catalyst layer in such a way that it acquires a macrostructure, for example with grooves or channels suitable for conducting electrolyte. The transfer substrate must then have a negative form of this macrostructure, such as projections.

[0058] A preferred embodiment provides that the transfer substrate is provided with at least one character that protrudes from or is recessed into the surface of the transfer substrate. This causes a negative of the character to be imaged on the surface of the catalyst layer. Information can be transmitted using the character. Based on this character or the information encoded therein, the catalyst layer or the entire layered body or a precursor of the layered body can be identified. The character can be, for example, a letter, a number, or a barcode. The character can, for example, assist in the correct alignment of the layered body during cell assembly.

[0059] Due to these particular advantages of its pre-formed surface, a corresponding electrocatalytically active or activatable laminated body with at least one solid ionomer layer which contains or consists of an anion-conducting polymer and with at least one solid catalyst layer contacting the ionomer layer, which comprises at least two phases, namely a first phase which is formed by the aforementioned anion-conducting polymer and / or another polymer and a second phase which is formed by an electrocatalytically active or activatable, particulate electrocatalyst, wherein the second phase is dispersed in the first phase, is also a subject of the invention, provided that the catalyst layer has a pre-formed surface.

[0060] Such a laminated body is obtainable by the manufacturing process according to the invention.

[0061] Such a laminated body can also be obtained by forming its precursor. Since the precursor is passed through in the production process according to the invention, the precursor forms a further subject of the invention.

[0062] The precursor according to the invention has at least one solid ionomer layer which contains or consists of an anion-conducting polymer and it contains at least one solid catalyst layer which is in contact with the ionomer layer and which has a pre-formed surface and which comprises at least three phases, namely a first phase which is formed by the aforementioned anion-conducting polymer and / or another polymer, a second phase which is formed by an electrocatalytically active or activatable, particulate electrocatalyst and a third phase which is formed by a particulate inorganic material which is different from the electrocatalyst, wherein the second phase and the third phase are dispersed in the first phase. The catalyst layer of the precursor of the electrocatalytically active or activatableThe activatable composite body therefore always has at least three phases: a first phase formed by the anion-conducting polymer and / or another polymer, a second phase formed by the electrocatalytically active or activatable particulate electrocatalyst, and a third phase formed by a particulate inorganic material. The second phase and the third phase are each dispersed in the first phase.

[0063] The weight proportions of the three phases of the solid catalyst layer of the precursor based on the total weight of the solid catalyst layer of the precursor are preferably in the ranges given in Table 0, provided that the sum of all weight proportions is 100 wt.%.

[0064] Table 0: preferred weight fractions of the phases of the catalyst layer of the precursor

[0065] The precursor and the final form of the laminate differ, on the one hand, in the respective proportion of particulate structure-forming agents or their products generated by leaching, and, on the other hand, in the degree of porosity induced by the formation process. Both aspects relate to the catalyst layer. What the precursor and the final laminate have in common is the advantageous, pre-formed surface of the catalyst layer, which is imprinted on them by the transfer substrate, because the formation process changes the geometrically determined shape of the surface only insignificantly.

[0066] In the event that the particulate inorganic material is silicon dioxide and / or aluminum oxide and the alkali is potassium hydroxide or sodium hydroxide, the preferred contents or expected residual contents of these substances or their reaction products are set out in Table 1:

[0067] Table 1 : preferred contents of silica, alumina, silicate and aluminate All values ​​given in Table 1 are expressed as wt.% relative to the total mass of the catalyst layer. The values ​​refer to the sum of the individual weight fractions of the substances listed in the row. In the event that a substance is not included in the layer, the sum corresponds to the weight fraction of the substance included.

[0068] The higher silicate content of up to 6% before leaching is explained by the fact that some ionomers contain reactive OH groups, which begin to convert the silica into silicate even before contact with the alkaline solution. The same applies to the conversion of alumina to aluminate, because the conversion occurs in the presence of water, which is present as a production residue in the laminate or comes from atmospheric moisture.

[0069] Both the final composite and its precursor can be used as electrocatalytically active or activatable anion exchange membranes. The corresponding use is a further subject of the invention.

[0070] A particularly preferred use is the use of the laminated body according to the invention or its precursor as an anion exchange membrane in a process for producing hydrogen and oxygen by electrolysis of water in an alkaline medium (AEMWE). The use consists in carrying out the electrolysis in the presence of the laminated body or its precursor.

[0071] Such a process for producing hydrogen and oxygen by splitting water is carried out in an electrolyzer. An electrolyzer comprising at least one precursor according to the invention and / or a laminated body according to the invention is therefore a further subject of the invention.

[0072] The inventive method for producing the laminated body has the particular advantage that it can be divided into two stages, each of which can be carried out at a different location. For example, it is conceivable to produce the precursor in an AEM factory (first stage) and then incorporate the precursor into an electrochemical cell. The second stage of the process, i.e. the formation of the precursor into the final anion exchange membrane with a porous catalyst layer by leaching and washing, only takes place in the electrochemical cell, i.e. at the later site of use of the AEM. The treatment with alkali solution and the subsequent washing of the catalyst layer can generally be carried out without any problems in the cell because it is alkali-resistant and has means for exposing the catalytically coated AEM to the alkali or washing liquid.The media are the same devices required during electrolysis to pump the electrolyte through the cell. Since alkaline hydroxide is used as the electrolyte in alkaline water electrolysis anyway, the subsequent electrolyte can, in the simplest case, be used for both leaching and washing. In extreme cases, the formation of the precursor takes place during ongoing electrolysis. This simplifies the production of the catalytically active AEM because no extra alkali hydroxide needs to be kept on hand: the electrolyte that is already required is simply used for formation. Likewise, the operating equipment required for formation is eliminated in the production plant, and the existing electrolyzer units are used instead.

[0073] However, it is also possible to carry out the formation of the precursor at the location where the laminate was produced.

[0074] This means that there are basically two possibilities for formation: one at the site of production of the precursor (ex-situ) and one at the site of use of the final, catalytically active layered body, namely in the cell (in-situ).

[0075] Accordingly, the process steps associated with the formation: l) applying the aqueous alkaline solution to the solid catalyst layer; m) reacting at least a portion of the inorganic material with the alkaline solution to form a product within the solid catalyst layer; n) washing out at least a portion of the product from the solid catalyst layer; o) obtaining the electrocatalytically active or activatable layered body, wherein the layered body comprises the washed-out solid catalyst layer and the solid ionomer layer applied thereto; are carried out optionally within (in situ) or outside (ex situ) an electrochemical cell.

[0076] Of course, mixed forms are also conceivable, in which the formation steps are carried out partly inside and partly outside an electrochemical cell, such as ex-situ conversion and in-situ leaching. Of course, the steps can also be initiated outside the cell and completed within it. Accordingly, at least some of the formation steps are carried out inside or outside an electrochemical cell. The individual formation steps can also be partially carried out simultaneously.

[0077] The method is preferably carried out as a roll-to-roll process. The transfer substrate is provided in strip form on a roll. The transfer substrate must therefore be a flat, flexible film or a flat textile fabric. Flat means significantly longer and wider than thick, i.e. essentially two-dimensional. Films and textile fabrics are inherently flat and therefore mostly flexible. Strip-shaped means that a flat transfer substrate is significantly longer than wide and therefore virtually "endless". A strip-shaped transfer substrate can, for example, be 100 μm thick, 100 mm wide and 100 m long. The strip-shaped transfer substrate is provided wound up on a first roll. In the roll-to-roll process, the transfer substrate is continuously unwound from the first roll, coated and dried. The transfer substrate can also be continuously peeled off.If the formation is carried out ex-situ, the leaching and washing processes are also carried out continuously, resulting in a virtually endless, ribbon-like laminate. This is wound onto a second roll. Such a roll-to-roll process is very efficient because the individual steps occur continuously and simultaneously—as long as the first roll is not empty. The roll-to-roll process requires that the resulting ribbon-like laminate is also flexible, without the catalytically active coating flaking off again. If necessary, a larger bending radius is achieved on the second roll.

[0078] In the in-situ variant of the roll-to-roll process, formation takes place in the cell. For this purpose, the ribbon-shaped precursor is wound onto the second roll and delivered to the cell manufacturer. The manufacturer unwinds the ribbon-shaped precursor from the second roll, combines the ribbon-shaped precursor with ribbon-shaped electrodes to form a ribbon-shaped stack, and cuts this into individual pieces, each of which is assembled into a cell. Leaching and washing then take place in the cell, transforming the precursor into the final layered body used as a catalytically active membrane. Alternatively, the precursor can first be cut into individual pieces before these are assembled with the electrodes in the cell. In the in-situ variant of the roll-to-roll process, only the precursor is produced "on the line."

[0079] All variants of a roll-to-roll concept of the present process have in common that the transfer substrate is a band-shaped flexible film or a band-shaped flexible textile fabric, that the band-shaped transfer substrate is provided wound up on a first roll, that the band-shaped transfer substrate is continuously unwound from the first roll, that the catalyst ink is continuously applied to the band-shaped transfer substrate, and that the depletion of the first solvent, the application of the ionomer solution and the depletion of the second solvent take place continuously, whereby a band-shaped precursor of the laminated body is obtained.

[0080] In view of the production method at two different locations, the precursor of the catalytically active or activatable layered body, which has to be transported between these locations and which, from the perspective of the manufacturer of the electrolyzer, represents a supply product, is another subject of protection.

[0081] As already mentioned, silicon dioxide, aluminum oxide, or mixtures thereof can be used as particulate inorganic materials in this process. These substances form water-soluble products with the alkali metals contained in the alkali. Other inorganic substances can also be used as structure-imparting agents, provided they are present in solid, particulate form under processing conditions and can be reacted with the alkali to form washable, ideally water-soluble products. To give the catalyst layer the finest possible porosity, the inorganic material used should be in the form of a powder as fine as possible. Flame-pyrolytically produced (pyrogenic) aluminum oxide and / or silicon dioxide is preferably used. This type of material is particularly fine and particularly pure.

[0082] The flame pyrolytic production of alumina and / or silicon dioxide is practiced on an industrial scale and is described by, among others,

[0083] C. Schulze Isfort, M. Rochnia: Production and physico-chemical characterization of nanoparticles, Toxicology Letters, Volume 186, Issue 3, 2009, Pages 148-151, ISSN 0378-4274, DOI 10.1016 / j.toxlet.2008.11.021 and by

[0084] Bogdan, Anatoli and M. Kulmala: "Pyrogenic Silica and Alumina" , in Encyclopedia of Surface and Colloid Science, Third Edition. (2015) DOI 10.1081 / E-ESCS3-120000089.

[0085] The inorganic material obtained by flame pyrolysis is characterized by its large specific surface area. Optimally, the specific surface area of ​​the particulate inorganic material determined according to the BET method is between 50 m 2 / g and 450 m 2 / g. For example, Aerosil® 300, which can be used as a structuring agent, has a BET surface area of ​​about 300 m 2 / g. The BET surface area is determined as usual by nitrogen adsorption according to the well-known method of Brunauer, Emmett, and Teller:

[0086] Brunauer, S., Emmett, PH, Teller, E.: Adsorption of Gases in Multimolecular Layers. Journal of the American Chemical Society. Vol. 60, Issue 2, 1938, Pages 309-319 DOI: 10.1021 / ja01269a023.

[0087] The determination of the BET surface area can be carried out automatically using commercially available measuring devices, such as the Micromeritics 5 TriStar II 3020 V1 .03.

[0088] Suitable particulate inorganic materials for the intended purpose are available from Evonik under the brand names AEROSIL® (fumed silica) and AEROXID® (fumed alumina), among others. In particular, but not exclusively, the following products: AEROSIL® OX 50, AEROSIL® 90, AEROSIL® 200, AEROSIL® 300, AEROSIL® 380 or AEROXIDE® 130. These materials have a specific surface area (BET) of 10 m 2 / g up to 1000 m 2 / g, preferably 50 m 2 / g up to 400 m 2 / g. Furthermore, it is possible to use already dispersed fumed metal oxides and silicas, either in water or solvent. Such materials are available, for example, from Evonik under the brand names AERODISP® or VP Disp®. These include, but are not limited to, the following products: AERODISP® W 1226, AERODISP® W 7225, AERODISP® W 7512 S, AERODISP® W 7520, AERODISP® W 7622, ​​VP Disp® W 7610 S, or AERODISP® W 925. A special feature of fumed silica is that its primary particles combine to form branched aggregates (secondary particles), which create particularly advantageous porosity in the layer. The primary particles have a particle size of up to 20 nm, while the aggregates are approximately 100 nm in size.

[0089] As an alternative to fumed silica, precipitated silica can also be used as a particulate inorganic material. By appropriate grinding of the precipitated silica, it achieves a specific surface area (BET) in the preferred range of 50 m 2 / g up to 400 m 2 / g. Precipitated silica is available, for example, from Evonik under the brand name SIPERNAT®.

[0090] The first solvent contained in the catalyst ink serves to dissolve the polymer also contained in the ink. The following solvents have proven particularly suitable for this purpose: dimethyl sulfoxide (DMSO), ethanol (EtOH), acetonitrile (AON), and methanol (MeOH). These solvents can be used alone or in mixtures with one another. These solvents can also dissolve ionomers. Furthermore, these solvents are comparatively human-friendly: only MeOH from this group is currently classified as a CMR substance. It is therefore recommended that the second solvent contained in the ionomer solution be selected from the same group. To reduce the number of chemicals to be processed, it is recommended to use the same solvent or solvent mixture selected from the group in both the catalyst ink and the ionomer solution. The first solvent is then identical to the second solvent.

[0091] With regard to the catalyst ink, it is recommended to add a different liquid dispersion medium in addition to the primary solvent. The dispersion medium is particularly necessary when the solid content of the ink formed by the electrocatalyst and the inorganic material is so high compared to the primary solvent that the ink cannot be processed properly. By adding the dispersion medium, the solid content of the overall catalyst ink is reduced, so that the ink achieves a lower viscosity and is easier to process. The ink is diluted with the dispersion medium. Undiluted ink tends to be pasty.

[0092] Regardless of the set viscosity and formulation, the catalyst ink always forms a dispersion, namely with a liquid phase consisting of polymer dissolved in the first solvent and, if applicable, the liquid dispersion medium, as well as with a first solid phase consisting of the electrocatalyst and a second solid phase consisting of the inorganic material.

[0093] Water (H2O), N-methyl-2-pyrrolidone (NMP), N,N-dimethylacetamide (DMAC), acetone (ACT), and 2-propanol (IPA) are particularly suitable as dispersing media for diluting the ink. These dispersing media can be used alone or in mixtures with one another.

[0094] If necessary, the catalyst ink can also contain other auxiliary substances or additives, such as dispersing agents, rheological aids, or surfactants. The addition of such auxiliary substances or additives is preferably avoided so that the subsequent catalyst layer does not contain any disruptive, electrocatalytically inactive foreign substances. However, in many cases, conductivity additives must be included, which increase the electrical conductivity of the subsequent catalyst layer or even create it in the first place. Many polymers used in the ink exhibit, at best, ionic conductivity but hardly any conductivity for electrons. Typical conductivity additives are carbon blacks, especially specialty carbon blacks such as Ketjenblack® from Nouryon or Vulcan® XC72 from Cabot Corporation.

[0095] Suitable compositions for an ink are given in Table 2:

[0096] Table 2: Preferred formulations of catalyst inks

[0097] The weight proportions of the components contained in the ink add up to a total that does not exceed 100% by weight.

[0098] The polymer contained in the ink at least acts as a binder, immobilizing the electrocatalyst in the catalyst layer. Since the hydroxide ions transported by the ionomer layer must come into contact with the catalytically active centers of the electrocatalyst, an ionically conductive connection between the electrocatalyst and the ionomer layer is required. This is most easily achieved via the electrolyte, which penetrates the pores of the catalyst layer during use. Additionally, ionically conductive substances can be added to the ink, which are enclosed in the polymer and impart a certain ionic conductivity. However, it is better to use a polymer as a binder that has intrinsic conductivity for hydroxide ions. Such anion-conducting polymers are preferably used as binders in the catalyst ink or the catalyst layer produced from it.The use of ionomers creates an additional ionically conductive connection to the catalytically active centers through the ionomer. This allows for an increase in electrolysis efficiency. A particularly preferred embodiment of the invention therefore provides for the catalyst ink to contain a polymer that conducts anions. After the catalyst layer has solidified, the polymer forms a solid phase that encloses at least the electrocatalyst.

[0099] In the simplest case, commercially available anion-conducting polymers are used. These are usually polymers that contain cationic groups. These groups are either grafted onto the polymer or are part of the backbone. The cationic groups are usually quaternary trialkyl ammonium salts. Polystyrene, polysulfone, polyethersulfone, polyaryl ether, polybenzimidazoles, or polyphenylene oxide, often in fluorinated form, typically serve as the backbone.

[0100] The disadvantage of these ionomers is that they usually contain fluorine, which is why they are increasingly being viewed with reservations. Therefore, fluorine-free anion-conducting polymers are being used instead.

[0101] Such compounds are known. Fluorine-free ionomers having one of the following three structures (I), (II), (III) are preferably used: where in (I) X represents a structural element comprising a positively charged nitrogen atom which is attached to C 1 and C 2 and which is bonded via two bonds to one or two hydrocarbon radicals comprising 1 to 12, preferably 1 to 6, particularly preferably 1 or 5 carbon atoms and wherein in (I) Z stands for a structural element comprising a carbon atom which is bonded to C 3 and C 4and which comprises at least one aromatic six-membered ring which is directly bonded to one of the oxygen atoms, wherein the aromatic six-membered rings may be substituted by one or more halogen and / or one or more Ci- to C4-alkyl radicals; where in (II) X represents a structural element comprising a positively charged nitrogen atom which is attached to C 1 and C 2 and which is bonded via two bonds to one or two hydrocarbon radicals comprising 1 to 12, preferably 1 to 6, particularly preferably 1 or 5 carbon atoms, and wherein in (II) Z represents a structural element comprising a carbon atom which is bonded to C 3 and C 4and which comprises at least one aromatic six-membered ring which is directly bonded to one of the oxygen atoms, wherein the aromatic six-membered ring may be substituted in positions 3 and 5 with the same or different Ci to C4 alkyl radicals, in particular with a methyl, isopropyl or tert-butyl group, the methyl group being preferred; wherein in (III) X represents a ketone or sulfone group; wherein in (III) Z represents a structural element comprising at least one tertiary carbon atom and at least one aromatic six-membered ring, wherein the aromatic six-membered ring is directly bonded to one of the two oxygen atoms; and wherein in (III) Y represents a structural element comprising at least one nitrogen atom with a positive charge, wherein this nitrogen atom is bonded to the structural element Z.

[0102] The fluorine-free ionomers with structures (I), (II), and (III) are suitable both for use in anion exchange membranes and for immobilizing the catalyst on the membrane. Furthermore, these ionomers are excellently suited for processing using the process according to the invention. These polymers of structures (I), (II), and (III) should at least be present in the composition. These ionomers are known from patent applications EP3770201 A1, EP4032934A1, and EP4059988A1, respectively.

[0103] In addition to the catalyst ink, an ionomer solution is also required for the inventive production of the laminate. The ionomer solution contains at least two components, namely a second solvent and an anion-conducting polymer (ionomer). The weight proportions of these components, based on the total weight of the ionomer solution, are preferably within the ranges specified in Table 3 and add up to a total that does not exceed 100 wt. %. Table 3: Preferred formulations for ionomer solutions

[0104] Preferably, the ionomer solution used to create the ionomer layer contains the same ionomer as the ionomer used as a binder in the catalyst ink. This reduces the variety of materials to be processed and creates a good bond between the catalyst layer and the ionomer layer.

[0105] The ionomer used in the ionomer layer and / or the catalyst layer should have a specific conductivity S for hydroxide ions that is preferably between 50 mS / cm and 150 mS / cm. The fluorine-free ionomers described above achieve a specific conductivity of approximately 100 mS / cm.

[0106] The specific conductivity of ionomers today generally ranges between 5 mS / cm and 300 mS / cm. These conductivity values ​​refer to hydroxide ions (OH). The specific conductivity is often also given for chloride ions (Cl). The values ​​for chloride are then approximately one-fifth of the values ​​for hydroxide.

[0107] The measurement of the specific conductivity S for hydroxide ions of the ionomer is carried out as follows:

[0108] A solution of the ionomer is applied evenly to a glass plate using a doctor blade. After drying for 3 hours at 80 °C, the dry film thickness is determined. This should be in the range of 60 - 120 μm and as constant as possible across the surface. The film-like ionomer layer is separated from the glass plate by immersing it in a 1 M KOH solution. This produces an ionomer film.

[0109] Subsequently, an ion exchange process is carried out in the absence of CO2 using a glove box and / or tightly sealable boxes. The exclusion of CO2 is intended to prevent the carbonate formation of potassium hydroxide or OH' ions in the ionomer layer. A 1 M potassium hydroxide solution (standard solution from Carl Roth; K017.1) is used for the ion exchange. The contact between the ionomer film and the potassium hydroxide solution required for the ion exchange takes place in tightly sealable boxes.

[0110] The tightly sealable boxes are first washed with the potassium hydroxide solution in the glove box and then filled so that the ionomer film is well covered. The boxes are tightly sealed. The filled, sealed boxes are then placed in a 60°C shaking bath filled with water for one hour. The water is placed outside the glove box. This process is repeated three times, each time with fresh potassium hydroxide solution.

[0111] After the ionomer film has been ion-exchanged three times for one hour at 60 °C, it is again contacted with fresh potassium hydroxide solution and shaken for two days in a shaking bath at 60 °C. Ultrapure water is used to wash the ionomer film. All washing operations in this step also take place in the glove box. At the beginning of this step, the existing potassium hydroxide solution is removed from the boxes; for this purpose, the box is rinsed twice with ultrapure water. The box is filled with fresh ultrapure water and washed for 20 minutes at 60 °C in the shaking bath. The ionomer film is thus transferred to hydroxide form and washed.

[0112] For conductivity measurement, rectangular pieces measuring 25 mm x 15 mm are punched out of the washed ionomer foil (in hydroxide form) using a punching iron, which are referred to below as “test ionomer foils”.

[0113] Each ionomer film is installed in a conductivity cell, which allows the ionic conductivity within the plane of the film to be measured. This occurs while the membrane is flushed with deionized water. The intrinsic conductivity of the film, which is equal to the conductivity of the ionomer, can be calculated from the measurement geometry (distance or area of ​​the electrodes, film thickness, and film width).

[0114] The measuring cell and the measurement procedure (in this case for a Nation® 117 membrane) is described by Mana Jesus Gonzalez-Pabon et al. in section “2.6 Conductivity determination” of the preprint of

[0115] High-performance biodegradable membrane for point of need paper-based micro-scale microbial fuel cell analytical devices. bioRxiv 351890; doi: 10.1101 / 351890.

[0116] Here you will also find the instructions for calculating the conductivity of the foil from the measuring geometry.

[0117] The particulate electrocatalyst contained in the catalyst ink or in the catalyst layer produced therefrom is a substance which is capable of being catalytically active in the electrochemical reaction in which the layered body is to be placed. This means that the electrocatalyst accelerates the desired electrochemical reaction or even enables it without being consumed. Of course, it is conceivable that the electrocatalyst becomes deactivated, i.e. ages, over time. A deactivated electrocatalyst which no longer has the desired catalytic activity is also an electrocatalyst within the meaning of the invention. It is also conceivable that the electrocatalyst contained in the catalyst layer does not yet have the desired catalytic activity but must first be activated. For these reasons, the layered body is referred to here as being electrocatalytically active oris at least electrocatalytically activatable. In principle, all known electrocatalytically active substances can be considered as electrocatalysts, as long as they are in particulate form. Electrocatalysts are usually in powder or granular form. However, electrocatalysts can also be present in a dispersion. Water or alcohol, for example, serves as a dispersion medium. The dispersion medium in which the electrocatalyst is provided can be identical to or different from the dispersion medium found in the ink.

[0118] Since the final layered body is primarily intended for use in AEMWE, materials known to catalyze the formation of hydrogen (hydrogen evolution reaction - HER) or the formation of oxygen (oxygen evolution reaction - OER) are used as the electrocatalyst. Depending on whether the catalyst layer within the electrochemical cell is oriented toward the anode or the cathode, the catalyst layer contains an OER electrocatalyst or a HER electrocatalyst.

[0119] It is also conceivable to provide the laminated body with two catalyst layers, one containing an OER electrocatalyst, while the other contains a HER electrocatalyst. Both catalyst layers are then separated from each other by at least one ionomer layer.

[0120] In such a situation, it is helpful to identify the two catalyst layers using a symbol to prevent the double-sided catalytically active anion exchange membrane from being installed upside down. The symbol can be formed, as discussed above, preferably over the transfer substrate.

[0121] Specifically, within the scope of the invention, the following elements can be used as particulate electrocatalysts: 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 can be used as electrocatalysts in pure form, as oxides, hydroxides, oxide hydroxides, or phosphides, individually or in combination.

[0122] Particularly preferred is an ink which uses platinum or platinum alloy supported on carbon (Pt / C) or a nickel-iron (oxide) hydroxide (NiFeaObHc) or a nickel-iron phosphide (NiFe a Pt>). The indices a, b, and c represent real numbers in the interval from 0 to 8. The indices a, b, and c can be the same or different. The nickel-iron ratio in the nickel-iron (oxide) hydroxide should ideally be in the range of 2:1 to 10:1. Figure description

[0123] The process according to the invention, the resulting laminated body, and the precursor stage of the laminated body undergone during the process will now be explained in more detail with reference to the accompanying drawings. The drawings show schematically:

[0124] Figure 1 : Application of the catalyst ink to the transfer substrate;

[0125] Figure 2: Fresh catalyst layer on transfer substrate;

[0126] Figure 3: Depletion of the first solvent from the catalyst layer;

[0127] Figure 4: Solid catalyst layer on transfer substrate;

[0128] Figure 5: Application of the ionomer layer to the catalyst layer;

[0129] Figure 6: Fresh ionomer layer on solid catalyst layer;

[0130] Figure 7: Depletion of the second solvent from the fresh ionomer layer;

[0131] Figure 8: Removing transfer substrate;

[0132] Figure 9: Pre-product;

[0133] Figure 10: Application of the aqueous alkaline solution;

[0134] Figure 1 1 : Washing out at least part of the alkali silicate;

[0135] Figure 12: Final composite with catalytic activity;

[0136] Figure 13: EDX spectrum of the silica precursor before leaching;

[0137] Figure 14: EDX spectrum of the silica-coated composite after leaching;

[0138] Figure 15: Electrolysis measurement of a laminated body produced according to the invention (round

[0139] symbols, solid line) compared to a reference layer body (diamond-shaped symbols, dashed line);

[0140] Figure 16 A: 3D scan of the surface of the catalyst layer of a laminated body produced according to the invention;

[0141] Figure 16 B: Line scan of the surface of the catalyst layer of a laminated body produced according to the invention;

[0142] Figure 17 A: 3D scan of the surface of the catalyst layer of a COM not produced according to the invention;

[0143] Figure 17 B: Line scan of the surface of the catalyst layer of a COM not produced according to the invention;

[0144] Figure 18: as Figure 15, additionally with a further inventively produced

[0145] Layered body (square symbols, dotted line).

[0146] First, a transfer substrate 1 is prepared. This is a flat glass plate. However, other materials, such as PET, can also be used as the transfer substrate. The glass plate does not need to be flat; it can also contain grooves. Instead of a rigid plate, a film or a textile fabric can also be used as the transfer substrate.

[0147] Furthermore, a catalyst ink 2 is provided, which essentially comprises the following components: a solid particulate electrocatalyst 3, solid particulate silicon dioxide 4, and a liquid solution 5 containing a first solvent and a polymer dissolved in the first solvent (solution 5 is shown as a clear liquid in Figures 1 and 2). The catalyst ink 2 can optionally contain further components, such as a dispersing medium or dispersing aid. Due to its solid and dissolved constituents, the catalyst ink 2 has the form of a heterogeneous mixture (dispersion). Depending on the formulation and the processing temperature, the catalyst ink 2 can be either low-viscosity or high-viscosity. Apart from the silicon dioxide 4 it contains, the catalyst ink 2 corresponds to conventional catalyst inks, such as those used for the catalytically active coating of membranes (CCM) or electrodes (CCS).

[0148] The catalyst ink 2 is applied to the transfer substrate 1. This is done conventionally by direct coating with a doctor blade or slotted nozzle, by spraying, by screen printing, or indirectly via a transfer medium (a so-called decal). Since this application corresponds to the state of the art, this process is shown in a very simplified manner in Figure 1.

[0149] By applying the catalyst ink 2 to the transfer substrate 1, the transfer substrate 1 receives a fresh catalyst layer 6 (Figure 2). The thicknesses of the fresh catalyst layer 6 and the transfer substrate 1 are not shown to scale in Figure 2 or the other figures: In a technical application, the thickness of the transfer substrate 1 is approximately 20 μm to 1000 μm, while the catalyst layer is very thin at approximately 10 μm to 20 μm. The fresh catalyst layer 6 still contains the transparent solution 5.

[0150] In a next step, the first solvent 7 contained in the solution 5 is depleted from the fresh catalyst layer 6. This is most easily achieved by drying. Figure 3 shows a schematic of how the first solvent 7 evaporates from the fresh catalyst layer. As a result of the removal of the first solvent 7, the polymer 8 previously dissolved in the solution 5 precipitates and forms a solid matrix that encloses the particulate materials 3, 4. In practice, the surface of the matrix is ​​not as sharply defined as simplified in Figures 3 to 5. Rather, the polymer 8 deposits on or around the individual particles 3, 4, spans the interstices, and thus forms an irregular, non-planar surface.

[0151] Once the drying process is complete, the polymer 8 matrix extends across the entire thickness of the catalyst layer down to the transfer substrate 1 (Figure 4). In this way, the transfer substrate 1 receives a closed, solid catalyst layer 9 formed from the three phases: polymer 8, electrocatalyst 3, and silicon dioxide 4.

[0152] An ionomer solution 10 is then applied to the solid catalyst layer 9 (Figure 5). The ionomer solution is liquid and contains an anion-conductive ionomer dissolved in a second solvent. The liquid ionomer solution 10 spreads over the solid catalyst layer 9, thereby leveling out the unevenness of the matrix surface. Since the catalyst layer is still closed at this point, the ionomer solution cannot penetrate the solid catalyst layer 9. Once the ionomer solution 10 has completely spread over the surface of the solid catalyst layer 9, it forms a fresh ionomer layer 11 thereon (Figure 6). The surface of the fresh ionomer layer 11 is much flatter than the surface of the solid catalyst layer 9, which now forms a boundary layer 12 between the catalyst layer and the ionomer layer.

[0153] A second drying process now follows, during which the second solvent 13 contained in the fresh ionomer layer 11 is depleted from the fresh ionomer layer 11 (Figure 7). This forms a solid ionomer layer 14, which consists of the now no longer dissolved anion-conducting ionomer 15. The solid ionomer layer 14 first forms on the side facing away from the solid catalyst layer 9, so that residues of the fresh ionomer layer 11 remain between the solid ionomer layer 14 and the solid catalyst layer 9. Over time, the ionomer layer 14 dries thoroughly until it is completely solid. If a porous transfer substrate is used, such as a porous fleece or expanded PTFE, drying can also take place from the direction of the transfer substrate 1 (not shown).

[0154] At this point, it should be mentioned that it is also possible to apply the ionomer solution to the fresh catalyst layer 6 and not, as shown here, to the solid catalyst layer 9. The drying of both fresh layers 6, 11 then takes place in one process, whereby the solidification of the outer ionomer layer also begins before the solidification of the catalyst layer.

[0155] At the latest when both layers 9 and 14 are solid, the transfer substrate 1 is detached from the solid catalyst layer 9 (Figure 8), so that the solid catalyst layer 9 is freely accessible on the side facing away from the ionomer layer. The now freely accessible surface O of the catalyst layer 9 is particularly flat, as it has received its shape from the transfer substrate 1. The surface O is preformed.

[0156] At this point, the precursor 16 shown in Figure 9 is obtained. The precursor 16 is already a laminated body comprising the solid catalyst layer 9 and the solid ionomer layer 14. Both solid layers 9 and 14 are bonded to one another in the region of the boundary layer 12 because the anion-conducting ionomer 15 contained in the ionomer layer 14 bonded to the matrix-forming polymer 8 contained in the solid catalyst layer 9 during solidification. In practice, it is advisable to use the same material for polymer 8 and anion-conducting ionomer 15. This makes the bond between the two solid layers 9 and 14 particularly strong and durable.

[0157] With the receipt of precursor 16, the first stage of the process (Figures 1 to 9) is completed. Now the second stage of the process begins, namely formation (Figures 10 to 12).

[0158] During the formation process, the solid catalyst layer 9 of the precursor 16 is first exposed to an aqueous alkaline solution, such as potassium hydroxide (potassium hydroxide - KOH). The exposure, shown only schematically in Figure 10, can be carried out most simply by applying the potassium hydroxide solution to the solid catalyst layer 9 with a brush or by immersing it in a bath of potassium hydroxide (KOH). At least the initially formed surface O of the catalyst layer 9 must be exposed to the aqueous alkaline solution.

[0159] The hydroxide contained in the alkaline solution reacts with the particulate silicon dioxide 4 present in the solid catalyst layer 9 to form the corresponding alkali silicate. In the case of the potassium hydroxide solution KOH used here, potassium silicate 17 and liquid water H2O are formed according to equation (1).

[0160] Since potassium silicate 17 is water-soluble, it can be washed out of the solid catalyst layer 9 with water (H2O) or an aqueous washing solution; see Figure 11 . Pores 18 remain in the polymer 8 matrix at the locations where the silicon dioxide or potassium silicate particles were previously located. The solid catalyst layer 9 thus becomes openly porous.

[0161] The manufacturing process is now complete with the formation. Figure 12 schematically shows the final electrocatalytically active or electrocatalytically activatable laminated body 19, comprising the solid catalyst layer 9 and the solid ionomer layer 14 deposited thereon. The solid catalyst layer 9 comprises the particulate electrocatalyst 3 and the polymer matrix 8, which now contains pores 18. Furthermore, the catalyst layer 9 of the final laminated body 19 also contains isolated, unreacted silicon dioxide 4 and unleached potassium silicate 17, since both the conversion and the leaching do not occur perfectly, particularly in the region of the boundary layer 12 between the catalyst layer 9 and the ionomer layer 14.Neglecting the unreacted and washed-out particles 4 and 17, the solid catalyst layer 9 of the formed layered body 19 therefore appears to be essentially two-phase, namely with the polymer 8 as the first phase and the electrocatalyst 3 as the second phase.

[0162] The laminated body 19 shown in Figure 12 has only a single catalyst layer 9 on one side of the ionomer layer 14. In practice, it may be expedient to provide the solid ionomer layer 14 with a second catalytically active layer on its side facing away from the solid catalyst layer 9. This can again be achieved by applying a second catalyst ink to the solid ionomer layer 14 and subsequently drying it (not shown). The second catalyst layer then contains a second electrocatalyst that differs from the electrocatalyst 3 contained in the first catalyst layer 9: For example, the first-produced catalyst layer 9 may contain a cathode catalyst (HER), while the second electrocatalyst contained in the second catalyst layer is an anode catalyst (OER).

[0163] Instead of coating the ionomer layer with a catalyst layer on each side, it is also possible to produce an anodic layer with an OER catalyst and a cathodic layer with a HER catalyst. These two layers can be incorporated into an electrochemical cell so that they are adjacent to each other with their respective ionomer layers and the respective catalyst layer faces the corresponding electrode. Examples:

[0164] The following describes the process for producing electrocatalytically active composites with anion conductivity and a porous catalyst layer using a platinum / carbon-based catalyst layer as an example. The effects achieved with the invention are then experimentally demonstrated.

[0165] 1 . Preparation of an ionomer (not part of the invention)

[0166] An anion-conducting cationic polymer was synthesized according to Example 3 of EP3770201A1.

[0167] 2. Providing a catalyst ink without dissolvable structuring agents (as a comparative experiment, not part of the invention)

[0168] A screw-capped jar was filled one-third with yttrium-stabilized zirconium oxide grinding balls (5 mm diameter). Two parts by weight of catalyst powder (platinum on carbon, 50% platinum loading) were then poured into the jar. 19 parts by weight of water were then added, the lid was sealed, and the jar was shaken for one minute using a vortex shaker (model "lab dancer", IKA). The jar was reopened, 19 parts by weight of ethanol were added, resealed, and shaken for another minute. The jar was then alternately placed on a tilt / roll mixer at 60 rpm for at least five hours and in an ultrasonic bath (180 W) for five minutes. This process was repeated twice.

[0169] 76 parts of water and 76 parts of ethanol were added and shaken for one minute using a vortex shaker.

[0170] Finally, an ionomer solution (5% ionomer as prepared in 1., dissolved in DMSO) was added until the solids content of the ionomer reached 14% of the total solids content, the vessel was sealed, the solution was rolled on the tilt / roll mixer for one hour and finally placed in an ultrasonic bath at 180 W for five minutes.

[0171] 3. Providing a catalyst ink with silica (part of the invention)

[0172] The production using silica was largely analogous to the production of the comparison ink described above under 2., but the silica was also added during the last addition of water and ethanol:

[0173] The screw-cap jar was filled one-third with yttrium-stabilized zirconium oxide grinding balls (5 mm diameter). Two parts by weight of catalyst powder (platinum on carbon, 50% platinum loading) were then poured into the jar. 19 parts by weight of water were then added, the lid was sealed, and the jar was shaken for one minute using a vortex shaker (model "lab dancer", IKA). The jar was reopened, 19 parts by weight of ethanol were added, resealed, and shaken for another minute. The jar was then alternately placed on a tilt / roll mixer at 60 rpm for at least five hours and in an ultrasonic bath (180 W) for five minutes. This process was repeated twice.

[0174] 0.6 parts by weight of silica, 76 parts each of water and 76 parts of ethanol were added and shaken for 1 minute using a vortex shaker. The silica was added in the form of a silica with a BET surface area of ​​300 m². 2 / g (AEROSIL® 300), in a dispersion in water with a 10% solids content. The amount of water in the dispersion was taken into account in the total amount of water added.

[0175] Finally, ionomer solution (5% ionomer prepared according to 1., dissolved in DMSO) was added until the solids content of the ionomer reached 14% of the total solids content, the vessel was closed, the solution was rolled on the tilt / roll mixer for one hour and finally placed in an ultrasonic bath at 180 W for five minutes.

[0176] 4. Coating a transfer substrate with the comparison ink (not inventive)

[0177] For the comparative test (without silica), the ink provided under 2. was applied in several layers to a transfer substrate using a spray coater. The transfer substrate was a planar glass plate. During coating, the glass plate was fixed to a heated (60 °C) surface.

[0178] The coating parameters were adjusted to achieve a homogeneous platinum surface loading of 0.45 mgpt / cm 2 Care was taken to ensure that each individual layer was thoroughly dry before the next layer was applied. Finally, the coated glass plate was dried for 30 minutes on the heated surface.

[0179] In this way, a glass plate was obtained which was provided with a dry catalyst layer.

[0180] 5. Coating the transfer substrate with the silica-containing catalyst ink (part of the invention)

[0181] For the experiment according to the invention (with silica), the ink provided under 3. was applied to a transfer substrate using a spray coater. The transfer substrate was a planar glass plate. During coating, the glass plate was fixed to a surface heated to 60°C.

[0182] The coating parameters were adjusted to achieve a homogeneous coating with approximately 90 layers.

[0183] Platinum surface loading of 0.45 mgpt / cm 2 Care was taken to ensure that each individual layer was thoroughly dry before the next layer was applied. Finally, the coated glass plate was dried for 30 minutes on the heated surface.

[0184] In this way, a glass plate was obtained which was provided with a dry catalyst layer containing silica.

[0185] 6. Structure of a comparative composite body without silica (not part of the invention)

[0186] An ionomer layer made from the cationic polymer synthesized in 1. was then applied to the catalyst layer of the glass plate obtained in 4. This process was carried out as described in Example 4 of EP3770201A1, except that the catalyst-coated glass plate obtained in 4. was used instead of an uncoated glass plate.

[0187] After drying the ionomer layer, a laminated body was obtained with the catalyst layer and the ionomer layer applied on top. The laminated body was carefully removed from the glass plate using water.

[0188] 7. Construction of a laminated body with silica (part of the invention)

[0189] An ionomer layer was applied from the cationic polymer synthesized in 1. to the silica-containing catalyst layer of the glass plate obtained in 5. This process was carried out as described in Example 4 of EP3770201A1, except that the catalyst-coated glass plate obtained in 5. was used instead of an uncoated glass plate.

[0190] After drying the ionomer layer, a laminated body was obtained with the silica-containing catalyst layer and the ionomer layer applied on top. The laminated body was carefully removed from the glass plate using water.

[0191] This laminated body can already be used like a conventional, catalytically active anion exchange membrane in alkaline water electrolysis. However, to achieve maximum electrolysis efficiency, a formation step is required, which can also be carried out in an electrolysis cell.

[0192] 8. Formation-leaching process

[0193] To transfer the laminates obtained in steps 6 and 7 to their hydroxide form, both samples were immersed in 1 M KOH at room temperature for three hours. Simultaneously with the ion exchange within the ionomer layer, the silica in the catalyst layer (only in the laminate from step 7) was largely converted into water-soluble potassium silicate and partially dissolved out. 9. Energy-dispersive X-ray analysis of the coated membrane

[0194] To understand the leaching process, a silica composite prepared as described in 7. was examined before and after the leaching process described in 8. using energy dispersive X-ray analysis (EDX). The spectrum before leaching is shown in Figure 13; Figure 14 shows the spectrum after leaching.

[0195] Comparing both spectra, a reduction in the peak intensity at approximately 0.55 keV and an almost complete disappearance of the peak at 1.7 keV are evident. The other peaks change less significantly. These peaks are, as indicated in the figures, specific for oxygen and silicon, respectively. The reduction in both peak intensities clearly confirms the successful leaching of a significant portion of the silicon oxide (silica) from the composite.

[0196] 10. Testing of the inventive laminated body in an electrolysis test cell

[0197] The composite obtained in 7. and 8. with an active Pt / C catalyst coated area of ​​16 cm 2 was tested in an electrolysis test cell (BalticFuelCells GmbH, Germany). The catalyst layer served as the cathode catalyst. A dimensionally stable, porous stainless steel electrode was used on the anode side. The measuring cell was maintained at 60 °C during the electrolysis tests and flushed with 1 M KOH solution on both the anode and cathode sides. The characteristic current-voltage curve is plotted in Figure 15 (round symbols, solid line).

[0198] 11 . Testing of the reference composite in the electrolysis test cell

[0199] Under the same conditions as described in 10, the reference composite manufactured in 6 and 8 was tested. The corresponding current-voltage characteristic is also shown in Figure 15 with diamond-shaped symbols and a dashed line.

[0200] 12. Comparison of measured values

[0201] In both graphs shown in Fig. 15, the required voltage was plotted against the externally applied current. The current is related to the membrane area (current density). At a constant current or current density (e.g., 1500 mA / cm 2 ), a low voltage is preferable, as this reduces the electrical energy required to produce the same amount of hydrogen at the same production rate, thereby increasing efficiency. Currents above 500 mA / cm are particularly relevant for industrial applications. 2It can be seen that the current-voltage characteristic curve at the higher current densities of the catalytically coated AEM produced according to the invention is lower than that of the comparison laminated body. The lower current density results in lower power consumption at the same voltage, so that the specific energy requirement for electrolysis is lower in the presence of the AEM produced according to the invention. 13. Production of a conventional CCM (not part of the invention)

[0202] First, an anion-conducting membrane was prepared from the cationic polymer synthesized in 1., as described in Example 4 of EP3770201 A1. This membrane was then coated with an ink prepared as described in 2.

[0203] This ink was applied to the prepared membrane in several layers using a spray coater. During coating, the membrane was fixed to a heated (60 °C) surface. The coating parameters were adjusted to achieve a homogeneous platinum surface loading of 0.45 mgpt / cm with approximately 90 layers. 2 Care was taken to ensure that each layer was thoroughly dry before applying the next layer. Finally, the coated membrane was allowed to dry for 30 minutes on the heated surface.

[0204] In this way, a CCM was prepared by the conventional process, namely applying a catalyst layer to the membrane, as a comparison example.

[0205] 14. Investigation of surface topography

[0206] The surface of the catalyst layer of the inventively produced layered body as described in 7 and 8 was examined. For this purpose, the sample was bonded to a sample carrier on the membrane side so that the catalyst surface could be analyzed. The surface topography was recorded using a confocal microscope (MarSurf 3D CM expert). Figure 16A shows the observed section of 800 pm x 800 pm. A very low surface roughness can be seen, which is due to the manufacturing process and the use of a very flat substrate. The relatively low roughness is particularly clearly visible in the line scan of Figure 16B.

[0207] The catalyst surface of the conventionally prepared CCM prepared in 13 was examined analogously. Its surface topography is shown in Figure 17A. A significant increase in surface roughness is noticeable. This is particularly evident in the line scan shown in Figure 17B.

[0208] 15. Reproduction of the inventive manufacturing process with a flexible substrate (part of the invention)

[0209] Since a roll-to-roll coating process with glass substrates does not appear to be feasible, the extent to which flexible films are also suitable as a substrate was investigated. For this purpose, the inventive process was carried out using a silica-containing ink as provided in 3. A transfer substrate was coated with this ink analogously to 5. However, this was a flexible PET film that was stretched flat, instead of a glass plate. No problems arose when coating the PET film with catalyst ink. Subsequently, the PET film coated with catalyst ink was overcoated with an ionomer layer analogously to the process described in 7. Thus, the inventive laminated body was produced on a flexible substrate. This could be easily and apparently residue-free removed from the PET film when dry.

[0210] 16. Providing a catalyst ink with precipitated silica (part of the invention)

[0211] The preparation using precipitated silica was largely analogous to the preparation of the comparison ink described above under 2., but precipitated silica was also added during the last addition of water and ethanol:

[0212] The screw-cap jar was filled one-third with yttrium-stabilized zirconium oxide grinding balls (5 mm diameter). Two parts by weight of catalyst powder (platinum on carbon, 50% platinum loading) were then poured into the jar. 19 parts by weight of water were then added, the lid was sealed, and the jar was shaken for one minute using a vortex shaker (model "lab dancer", IKA). The jar was reopened, 19 parts by weight of ethanol were added, resealed, and shaken for another minute. The jar was then alternately placed on a tilt / roll mixer at 60 rpm for at least five hours and in an ultrasonic bath (180 W) for five minutes. This process was repeated twice.

[0213] 0.6 parts by weight of precipitated silica, 76 parts each of water and 76 parts of ethanol were added and the mixture was vortexed for 1 minute. The silica was added in the form of precipitated silica with a BET surface area of ​​165 m². 2 / g (SIPERNAT® 380).

[0214] Finally, ionomer solution (5% ionomer prepared according to 1., dissolved in DMSO) was added until the solids content of the ionomer reached 14% of the total solids content, the vessel was closed, the solution was rolled on the tilt / roll mixer for one hour and finally placed in an ultrasonic bath at 180 W for five minutes.

[0215] 17. Coating the transfer substrate with the catalyst ink containing precipitated silica (part of the invention)

[0216] For the experiment with precipitated silica, the ink provided under 16 was applied to a transfer substrate using a spray coater. The transfer substrate was a planar PET film. During coating, the PET film was fixed to a surface heated to 60°C.

[0217] The coating parameters were adjusted to achieve a homogeneous platinum surface loading of 0.45 mgpt / cm 2 Care was taken to ensure that each individual layer was largely dry before the next layer was applied. Finally, the coated PET film was dried on the heated surface for 30 minutes. This resulted in a PET film coated with a dry catalyst layer containing precipitated silica.

[0218] 18. Structure of a laminated body with precipitated silica (part of the invention)

[0219] An ionomer layer made from the cationic polymer synthesized in 1. was applied to the catalyst layer containing precipitated silica of the PET film obtained in 17. This process was carried out as described in Example 4 of EP3770201A1, except that the catalyst-coated PET film obtained in 17. was used instead of an uncoated glass plate.

[0220] After drying the ionomer layer, a laminate was obtained with the precipitated silica-containing catalyst layer, and the ionomer layer was applied on top. The laminate was carefully removed from the PET film using water.

[0221] This laminated body can already be used like a conventional, catalytically active anion exchange membrane in alkaline water electrolysis. However, to achieve maximum electrolysis efficiency, a formation step is required, which can also be carried out in an electrolysis cell.

[0222] 19. Testing the laminated body in the electrolysis test cell

[0223] The laminated body produced in Figures 17 and 18 was tested under the same conditions as described in Figures 10 and 11. The corresponding current-voltage characteristic is shown in Figure 18 with square symbols and a dotted line. Otherwise, Figure 18 corresponds to Figure 15.

[0224] 20. Comparison of measured values

[0225] In the graphs shown in Fig. 18, the required voltage was plotted against the externally applied current. The current is related to the membrane area (current density). At a constant current or current density (e.g., 1500 mA / cm 2 ), a low voltage is preferable, as this reduces the electrical energy required to produce the same amount of hydrogen at the same production rate, thereby increasing efficiency. Currents above 500 mA / cm are particularly relevant for industrial applications. 2It can be seen that the current-voltage characteristic curve at the higher current densities for both catalytically coated AEMs produced according to the invention is lower than that of the comparison laminate. The lower current density results in lower power consumption at the same voltage, so that the specific energy requirement for electrolysis is lower in the presence of the AEMs produced according to the invention. The graphs show that a production process using precipitated silica (such as SIPERNAT®) already has a positive effect on efficiency, but this efficiency increase is smaller than that achieved with silica from a pyrogenic production route (such as AEROSIL®). 21. Conclusion

[0226] From a comparison of the current-voltage characteristics shown in Figures 15 and 18, it is evident that the catalytically active layered body produced according to the invention with silica and subsequent leaching achieves higher efficiency as an AEM in alkaline water splitting than the comparative layered body produced without silica. The higher efficiency can be explained by the fact that leaching imparts porosity to the layer, which in turn improves the accessibility of the catalytically active centers. Furthermore, it was shown that the inventive process can produce a catalytically active layered body with reduced surface roughness. The production process can also be implemented with flexible, fluorine-free substrates. CMR-free solvents could be used.

[0227] List of reference symbols

[0228] 1 transfer substrate

[0229] 2 catalyst ink

[0230] 3 Electrocatalyst

[0231] 4 Silicon dioxide

[0232] 5 Solution

[0233] 6 fresh catalyst layer

[0234] 7 first solvent

[0235] 8 Polymer

[0236] 9 solid catalyst layer

[0237] 10 ionomer solution

[0238] 11 fresh ionomer layer

[0239] 12 Boundary layer

[0240] 13 second solvent

[0241] 14 solid ionomer layer

[0242] 15 anion conductive ionomer

[0243] 16 Pre-stage

[0244] 17 Potassium silicate

[0245] 18 pores

[0246] 19 layered twill

[0247] O primordial surface

[0248] KOH potassium hydroxide solution

[0249] H2O water

Claims

Patent claims 1. A method for producing an electrocatalytically active or activatable layered body, comprising the following non-chronological steps: a) providing a transfer substrate; b) providing a catalyst ink containing at least a first solvent, at least one polymer dissolved in the first solvent, at least one particulate electrocatalyst that is electrocatalytically active or activatable, and at least one particulate inorganic material different from the electrocatalyst; c) applying the catalyst ink to the transfer substrate so that a fresh catalyst layer is formed on the transfer substrate;d) Depleting the first solvent from the fresh catalyst layer so that a solid catalyst layer is formed on the transfer substrate, said solid catalyst layer comprising at least three phases, namely a first phase formed by the now undissolved polymer, a second phase formed by the particulate electrocatalyst, and a third phase formed by the particulate inorganic material, wherein the second phase and the third phase are dispersed in the first phase; e) optionally: separating the transfer substrate from the solid catalyst layer; f) providing an ionomer solution containing at least a second solvent and at least one anion-conducting polymer dissolved in the second solvent; g) applying the ionomer solution to the fresh or solid catalyst layer so that a fresh ionomer layer is formed on the fresh or solid catalyst layer;h) depleting the second solvent from the fresh ionomer layer so that a solid ionomer layer is formed on the catalyst layer, in which the now undissolved anion-conducting polymer is enriched; i) providing an aqueous alkaline solution containing at least one alkali metal selected from the group consisting of sodium, potassium, and lithium; k) if not already done: separating the transfer substrate from the solid catalyst layer; l) applying the aqueous alkaline solution to the solid catalyst layer; m) reacting at least a portion of the inorganic material with the alkaline solution to form a product within the solid catalyst layer; n) washing at least a portion of the product out of the solid catalyst layer; o) obtaining the electrocatalytically active or activatable laminated body, wherein the laminated body comprises the washed-out solid catalyst layer and the solid ionomer layer applied thereto.

2. The method according to claim 1, wherein the ionomer solution is applied to the fresh catalyst layer, and wherein the depletion of the second solvent from the fresh ionomer layer takes place before or at the same time as the depletion of the first solvent from the fresh catalyst layer.

3. A process according to claim 1, wherein the ionomer solution is applied to the solid catalyst layer, and wherein the first solvent is removed from the fresh catalyst layer before the second solvent is removed from the fresh ionomer layer.

4. A process according to claim 1, 2 or 3, characterized in that the particulate inorganic material contains silicon dioxide and / or aluminum oxide.

5. Process according to one of claims 1 to 4, characterized in that the particulate inorganic material satisfies at least one of the following conditions: cc) the particulate inorganic material has a BET surface area whose value is between 50 m 2 / g and 450 m 2 / g, where the BET surface area is determined by nitrogen adsorption according to the method of Brunauer, Emmett, Teller DOI 10.1021 Zja01269a023; ß) the particulate inorganic material comprises aggregates of primary particles; y) the particulate inorganic material is obtained by flame pyrolysis.

6. Process according to one of claims 1 to 5, characterized in that at least one of the two solvents is selected from the group consisting of the following solvents: dimethyl sulfoxide (DMSO), ethanol (EtOH), acetonitrile (ACN), methanol (MeOH).

7. Method according to one of claims 1 to 6, characterized in that the catalyst ink additionally contains a dispersing medium different from the first solvent.

8. The method according to claim 7, characterized in that the dispersing medium is selected from the group of the following dispersing media: water (H2O), N-methyl-2-pyrrolidone (NMP), N,N-dimethylacetamide (DMAC), acetone (ACT), 2-propanol (IPA).

9. The method according to any one of claims 1 to 8, wherein the catalyst ink comprises the components listed in the table, characterized in that the weight proportions of the components based on the total weight of the catalyst ink are in the following ranges, provided that the sum of all components listed here does not exceed 100% by weight:

10. A process according to any one of claims 1 to 9, wherein the ionomer solution comprises the components listed in the table, characterized in that the weight proportions of the components based on the total weight of the ionomer solution are in the following ranges, provided that the sum of all components listed here does not exceed 100% by weight:

11. A process according to any one of claims 1 to 10, characterized by at least some of the steps: l) applying the aqueous alkaline solution to the solid catalyst layer; m) reacting at least a portion of the inorganic material with the alkaline solution to form a product within the solid catalyst layer; n) washing at least a portion of the product out of the solid catalyst layer; o) Obtaining the electrocatalytically active or activatable laminated body, wherein the laminated body comprises the washed-out solid catalyst layer and the solid ionomer layer applied thereto; carried out within an electrochemical cell.

12. The method according to any one of claims 1 to 10, characterized in that at least some of the steps: l) applying the aqueous alkaline solution to the solid catalyst layer; m) reacting at least a portion of the inorganic material with the alkaline solution to form a product within the solid catalyst layer; n) washing out at least a portion of the product from the solid catalyst layer; o) obtaining the electrocatalytically active or activatable laminated body, wherein the laminated body comprises the washed-out solid catalyst layer and the solid ionomer layer applied thereto; are carried out outside an electrochemical cell.

13. A process according to any one of claims 1 to 12, characterized in that the steps: l) applying the aqueous alkaline solution to the solid catalyst layer; m) reacting at least a portion of the inorganic material with the alkaline solution to form a product within the solid catalyst layer; n) washing out at least a portion of the product from the solid catalyst layer; take place at least partially simultaneously.

14. Method according to one of claims 1 to 13, characterized in that the transfer substrate is flat.

15. Method according to one of claims 1 to 14, characterized in that the transfer substrate is a plate or a film or a textile fabric.

16. The method according to claim 14 or 15, characterized in that the transfer substrate is provided with at least one character which protrudes from or recedes from the surface of the transfer substrate.

17. The method according to any one of claims 14 to 16, wherein the transfer substrate is a band-shaped flexible film or a band-shaped flexible textile fabric, characterized in that the band-shaped transfer substrate is provided wound up on a first roll, that the band-shaped transfer substrate is continuously unwound from the first roll, that the catalyst ink is continuously applied to the band-shaped transfer substrate, and that the depletion of the first solvent, the application of the ionomer solution and the depletion of the second solvent take place continuously, whereby a band-shaped precursor of the laminated body is obtained.

18. Precursor of an electrocatalytically active or activatable laminated body with at least one solid ionomer layer which contains or consists of an anion-conducting polymer and with at least one solid catalyst layer contacting the ionomer layer, which comprises at least three phases, namely a first phase formed by the aforementioned anion-conducting polymer and / or another polymer, a second phase formed by an electrocatalytically active or activatable, particulate electrocatalyst and a third phase formed by a particulate inorganic material which is different from the electrocatalyst, wherein the second phase and the third phase are dispersed in the first phase, characterized in that the catalyst layer has a preformed surface.

19. Precursor according to claim 18, characterized in that the particulate inorganic material is silicon dioxide and / or aluminum oxide, and that the total content of silicon dioxide and aluminum oxide is between 10 wt.% and 60 wt.%, based on the total mass of the catalyst layer.

20. Precursor according to claim 18 or 19, characterized in that the weight proportions of the phases based on the total weight of the solid catalyst layer are in the following ranges, with the proviso that the sum of all weight proportions is 100 wt.%:

21. An electrocatalytically active or activatable laminated body having at least one solid ionomer layer which contains or consists of an anion-conducting polymer and having at least one solid catalyst layer contacting the ionomer layer and comprising at least two phases, namely a first phase formed by the aforementioned anion-conducting polymer and / or another polymer and a second phase formed by an electrocatalytically active or activatable particulate electrocatalyst, the second phase being dispersed in the first phase, characterized in that the catalyst layer has a preformed surface.

22. A laminated body according to claim 21, which is obtained by a process according to any one of claims 1 to 17 and / or from a precursor according to claim 18 or 19 or 20.

23. Laminated body according to claim 21 or 22, characterized in that the catalyst layer additionally contains silicon dioxide and / or aluminum oxide, and that the content of silicon dioxide and aluminum oxide in total is between 0.2 wt.% and 25 wt.%, based on the total mass of the catalyst layer.

24. Precursor or laminated body according to one of claims 18 to 23, characterized in that the primary formed surface is provided with at least one mark which protrudes from or rebounds from the primary formed surface.

25. Use of a precursor or a laminated body according to one of claims 18 to 24 as an electrocatalytically active or activatable anion exchange membrane.

26. Use according to claim 25 in a process for producing hydrogen and oxygen by electrolysis of water in an alkaline medium.

27. Electrolyzer comprising at least one precursor or layered body according to one of claims 18 to 24.

28. Article according to one of the preceding claims 1 to 27, characterized in that the polymer contained in the catalyst ink or the catalyst layer is also anion-conductive.

29. Article according to one of claims 1 to 28, characterized in that the anion-conducting polymer has a specific conductivity S for hydroxide ions (OH ), measured after ion exchange in hydroxide, where S is between 5 mS / cm and 300 mS / cm or between 50 mS / cm and 150 mS / cm.

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