Structural design of electrochemical cells

Abstract

The present invention relates to an electrochemical cell comprising an anode, a cathode, and an anion conducting membrane disposed between the anode and the cathode. The present invention also relates to the use of the electrochemical cell in a process for producing hydrogen and oxygen by the electrochemical decomposition of water. The present invention further relates to an electrolyzer having a multiplicity of cells, and a method for manufacturing the electrolyzer.

Description

[Technical field]

[0001] The present invention relates to an electrochemical cell comprising an anode, a cathode, and an anion conducting membrane disposed between the anode and the cathode. The present invention also relates to the use of the electrochemical cell in a process for producing hydrogen and oxygen by the electrochemical decomposition of water. The present invention further relates to an electrolyzer having a multiplicity of cells, and a method for manufacturing the electrolyzer. [Background technology]

[0002] Electrochemical cells are used to carry out electrochemical processes. There are a large number of electrochemical processes, with widely different purposes. An important electrochemical process is the decomposition of chemical compounds. This process is called electrolysis.

[0003] The industrial implementation of electrochemical cells for performing electrolysis is called an electrolyzer. An electrolyzer typically contains a number of interconnected electrochemical cells.

[0004] An electrochemical cell always has two electrodes: a cathode and an anode. The cell is usually divided into two compartments by an electrically insulating separator. The anode resides in the first, "anode" compartment, and the cathode resides in the second, "cathode" compartment. The two electrodes or compartments are electrically separated from each other by the separator. The electrochemical cell is filled or permeated with water or an aqueous basic electrolyte.

[0005] An important electrochemical process is the production of hydrogen and oxygen by the electrochemical decomposition of water. One variant of water electrolysis is characterized by the use of an anion conducting membrane (anion exchange membrane, AEM) as a separator. This is commonly referred to as AEM water electrolysis (AEMWE). Because the reaction is accomplished in an alkaline medium, AEM water electrolysis is also often referred to as alkaline membrane water electrolysis.

[0006] For AEM water electrolysis, an electrochemical cell is filled with water or a basic water-based electrolyte and a voltage is applied between the anode and cathode. On the cathode side, water is converted into hydrogen (H 2 ) and hydroxide ion (OH - ) (Equation 1). The membrane transports the hydroxide ions to the anode side, where they are converted to oxygen (O 2 ) (Equation 2). This results in the formation of oxygen on the anode side and hydrogen on the cathode side. Therefore, the anode side is also called the oxygen side and the cathode side is also called the hydrogen side.

[0007] 2H 2 O+2e - →H 2 +2OH - (1) 2OH - →1 / 2O 2 +H 2 O+2e - (2)

[0008] To enable the described effects, the membrane must conduct hydroxide ions between the anode and the cathode. At the same time, it must be electrically insulating so that there is no electrical short circuit between the anode and the cathode. Finally, the anion-conducting membrane must be as gas-tight as possible so that there is no backmixing of the gases formed. In addition, the anion-conducting membrane must be resistant to the alkaline conditions present in AEM water electrolysis. These properties are met by certain anion-conducting polymers (also called anion-conducting ionomers).

[0009] To promote the reaction, catalytically active substances (also called electrocatalysts) are placed on both the cathode and anode sides. This is achieved by introducing catalytically active layers or coatings. These may be present on a substrate or on a porous transport layer specially introduced into the cell for the purpose (catalyst-coated substrate, CCS) or the membrane may be directly coated with the catalytically active material (catalyst-coated membrane, CCM).

[0010] In AEM water electrolysis, the flow of water or basic electrolyte through the cell and the flow of gas / electrolyte leaving the cell must be carried out to supply fresh water for the electrolysis and to take back again the hydrogen and oxygen formed, or the water or basic electrolyte they are enriched in. This is generally made possible by a porous transport layer (PTL), which, firstly, is closely adjacent to the catalytically active layer to allow good electrical contact, and, secondly, is electrically conductive and has sufficient porosity to transport the gases to the outside and to supply the water and electrolyte. To improve the transport of the water or basic electrolyte through the cell, a specific channel structure (called a flow field, FF) is incorporated into the cell. This structure has electrical contact with the porous transport layer, is electrically conductive, and establishes electrical contact with the end plate or bipolar plate (BPP). The bipolar plate electrically connects the two adjacent cells. The specific channel structure is often directly incorporated into the bipolar plate, for example by mechanical deformation. For efficient water electrolysis, it is particularly important that the contact resistances at (i) the contact surface of the catalytically active layer with the porous transport layer, (ii) the contact surface of the porous transport layer with the flow field, and (iii) the contact surface of the flow field with the bipolar plate are kept to a minimum and do not increase during operation of the electrolyzer as a result of possible oxidation or passivation of the contact surfaces, which would otherwise lead to an increase in cell voltage and a decrease in efficiency, as well as an increase in energy consumption.

[0011] A good overview of the electrochemical cell structures and materials currently used in AEM water electrolysis is provided by: 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.

[0012] A general objective in the development of electrolysers for water electrolysis is to improve the efficiency of the process and reduce the manufacturing costs of the electrolyser.

[0013] Recently, this idea has arisen from the use of textile structures as electrodes in alkaline water electrolysis. For example, Zhu Silu's research group coated stainless steel fiber felt with nickel-iron hydroxide and used it as an anode and cathode in water electrolysis: Zhu Silu et al.: Fast Electrodeposited Nickle-Iron Hydroxide Nanosheets on Sintered Stainless Steel Felt as Bifunctional Electrocatalyst for Overall Water Splitting.ACS Sustainable Chem.Eng.2020,8,9885-9895 DOI:10.1021 / acssuschemeng.0c03017.

[0014] The advantage of this process is the high catalytically active surface area of ​​the electrode that is obtained through nanostructuring. The extent to which such materials can be incorporated into electrochemical cells remains unclear by Zhu et al., for example, the electrochemical cell present in the article does not have any separator or membrane to separate the gases formed. As a result, backmixing of the hydrogen and oxygen gases formed at the anode and cathode is anticipated here, which could lead to hydrogen / oxygen gas explosions. Such a cell could be operated in the laboratory for research purposes, but is clearly not suitable for the industrial production of hydrogen. [Prior art documents] [Non-patent literature]

[0015] [Non-Patent Document 1] Miller, Hamish Andrew et al: Green hydrogen from anion exchange membrane water electrolysis: a review of recent developments in critical materials and operating conditions. Sustainable Energy Fuels, 2020, 4, 2114 DOI: 10.1039 / c9se01240k. [Non-Patent Document 2] Zhu Silu et al.: Fast Electrodeposited Nickle-Iron Hydroxide Nanosheets on Sintered Stainless Steel Felt as Bifunctional Electrocatalyst for Overall Water Splitting.ACS Sustainable Chem.Eng.2020,8,9885-9895 DOI:10.1021 / acssuschemeng.0c03017. Summary of the Invention [Problem to be solved by the invention]

[0016] The objective of the present invention is to identify an electrochemical cell capable of performing AEM water electrolysis on an industrial scale, which allows for energy efficient production of hydrogen and oxygen with reduced production costs. [Means for solving the problem]

[0017] This object is achieved by an electrochemical cell as claimed in claim 1. The present invention thus provides an electrochemical cell comprising an anode, a cathode, and an anion conducting membrane disposed between the anode and the cathode, the anode being fabricated at least in part as a first woven fabric comprising a catalytically active linear woven structure, the first woven fabric being in direct contact with the membrane.

[0018] An important finding of the present invention is that the woven structures are not only suitable as electrodes and electrocatalysts, but can also simultaneously assume the function of a porous transport layer and a flow field for the electrolyte and / or the formed gas; due to the presence of cavities between the individual linear structures, the woven fabric is in principle porous. Water or basic electrolyte can penetrate into these cavities and thus come into contact with the electrocatalyst. The formed gas can likewise flow out of the cavities. In this way, the textiles perform not only electrochemical functions, but also fluid functions. Due to their fluid-conducting properties, the textile electrodes can be brought into direct contact with the membrane. This means that the textile fabric is directly and two-dimensionally adjacent to the membrane. There is thus a direct mechanical contact between the membrane and the textile fabric, preferably over the entire area of ​​the membrane and the electrode. At the same time, there are no contact problems in the electrical sense, since the membrane is not conductive. Due to the fluid-conducting properties of the textile, the electrochemical cell according to the present invention can function without an additional porous transport layer and without additional flow fields. This reduces the electrical internal resistance of the cell, since there is no contact resistance between the individual components typically used.

[0019] A further advantage of the electrochemical cell according to the invention is that there is no absolute need for an ionomer (often also called binder) to immobilize the electrocatalyst directly on the substrate or electrode (CCS) of the electrolyzer or on the membrane (CCM) on the anode side. The oxygen formed during electrolysis is very active and can chemically attack (oxidize) the ionomer, which can lead to impairment of the mechanical and ionic conduction properties of the ionomer and can even cause the detachment of the electrocatalyst. This in turn leads to an increase in the required cell voltage and to a rise in energy consumption. As a result, the proposed electrochemical cell structure reduces its manufacturing costs and allows an energy-efficient process due to its low electrical resistance.

[0020] Due to the advantages of the woven structure, the anode is preferably made completely in the form of a woven fabric. This means that a woven fabric is used as the anode. However, it is also conceivable to use an anode that is only partially in the form of a woven fabric and otherwise consists of a non-woven material. For example, it is also possible to fix the woven fabric on a solid panel, or on a flat or molded sheet, or on an otherwise non-woven material, such as expanded metal, metal mesh.

[0021] The term "woven fabric" is used here as is customary in the textile technology. It refers to essentially two-dimensional textile structures, regardless of their connections, such as woven fabrics, braids, knitted materials, meshes, knits, nonwovens, waddings and felts. Woven fabrics with a multi-layer structure in the context of the present invention are considered to be two-dimensional textile structures. The fact that a woven fabric has a certain thickness does not mean that it is not two-dimensional.

[0022] Woven fabrics are formed from linear textile structures. A linear textile structure in this context is an essentially one-dimensional textile structure, such as fibers, filaments, threads or yarns. The fibers may be continuous or confined.

[0023] It is essential that the linear woven structures are catalytically active. This means that they are made at least in part from materials that facilitate the electrochemical reactions that take place in the cell. The catalytically active material must be present at least on the surface of the linear woven structures.

[0024] The catalytically active material is preferably an element selected from the group consisting of Au, Pt, Pd, Ir, Rh, Ru, Ag, Ni, Co, Cu, Fe, Mn, Mo. The elements can be used in elemental form (e.g. in the form of a uniform catalytically active coating or catalytically active particles) or in the form of alloys or compounds, such as oxides, mixed oxides, hydroxides, mixed hydroxides, spinels or perovskites. All of these substances are capable of promoting electrochemical reactions, in particular alkaline water electrolysis.

[0025] In a preferred embodiment of the invention, the catalytically active linear structure consists of a nickel-containing material. As a result, the undiluted material is catalytically active. This has the advantage that in the event of erosion of the surface, the catalytically active material does not disappear but is always present. This embodiment is particularly powerful. The catalytically active undiluted material is also available cheaply, i.e. as nickel, or as nickel-containing alloys, for example, in particular Hastelloy, Cronin, Monel, Inconel, Incoloy, Invar, Kovar. It is also possible to use nickel-containing steels, nickel-containing stainless steels, steels of the steel grades AISI 301, AISI 301L, AISI 302, AISI 304, AISI 304L, AISI310, AISI310L, AISI316, AISI316L, AISI 317, AISI 317L, AISI 321. The use of these standard materials as catalytically active materials for the first textile fabric eliminates the need to coat the fibers with other catalysts.

[0026] In a second embodiment of the invention, the linear woven structure comprises a substrate with a catalytically active coating on the surface, where the catalytically active coating comprises at least one element selected from the group consisting of Au, Pt, Ir, Ru, Rh, Pd, Ag, Ni, Co, Cu, Fe, Mn, Mo, or a compound of the selected elements, for example an oxide, mixed oxide, hydroxide, mixed hydroxide, spinel or perovskite. The substrate in that case does not have to be catalytically active itself. The linear woven structures obtain their catalytic activity by means of their coating. It is possible, for example, to use inexpensive carbon fibers that are chemically inert and have a long life. The catalytic activity is realized by the coating. Of course, it is also possible to further coat the catalytically active substrate with catalytically active substances in order to achieve a particularly high activity. In particular, the following substrate materials are useful: nickel; nickel-containing alloys such as Hastelloy, Cronin, Monel, Inconel, Incoloy, Invar, Kovar; nickel-containing steels, nickel-containing stainless steels, steel types AISI 301, AISI 301L, AISI 302, AISI 304, AISI 304L, AISI 310, AISI310L, AISI316, AISI 316L, AISI 317, AISI 317L, AISI 321; titanium, carbon.

[0027] The substrate is preferably coated with the catalytically active material without the use of a polymer binder. The catalytically active coating then does not contain a polymer. This has the advantage that the coating is chemically more stable and cannot be peeled off upon decomposition of the polymer. Coating without polymer is possible, for example, by electrodeposition of the catalytically active material onto the substrate or by sputtering or vapor deposition. More specifically, the coating does not contain an ionomer, i.e. an ion-conducting polymer.

[0028] Since the textile fabrics described herein are also suitable as cathodes, a preferred development of the invention envisages that not only the anode but also the cathode is at least partially made as a textile fabric, in order to distinguish between textiles used as cathodes and textiles used as anodes, a first textile fabric is used here for the material used as anode and a second textile fabric is used for the material used as cathode.

[0029] On the cathode side, the incorporation of catalytic activity into the textile material is not absolutely necessary. Nevertheless, it is preferred if the catalytically active material is also used in the second textile fabric. Here, the same material as on the anode side is preferred. In the simplest case, the same material is utilized on both the anode and cathode sides. However, this does not necessarily have to be the case. Therefore, a distinction between the first textile fabric and the second textile fabric is appropriate. Preferably, the cathode is created entirely as a textile fabric.

[0030] The second woven fabric not only performs the electrochemical function as a cathode, but also the function of a porous transport layer and a flow field for the water or basic electrolyte and / or the formed gas.

[0031] The electrochemical cell with two textile electrodes can be constructed in two variations. In a first variant, the second textile fabric (cathode, hydrogen side) is in direct contact with the membrane, unless the membrane itself is then coated with a catalytically active material (electrocatalyst), which requires that either the catalytically active substance is applied to the linear structures of the second textile fabric or that the material of the second textile fabric itself is catalytically active.

[0032] In a second variant, a catalytically active layer (electrocatalyst) is placed between the second woven fabric (cathode, hydrogen side) and the membrane. The linear woven structure from which the second woven fabric is constructed does not necessarily have to be catalytically active or coated with a catalytically active substance. The linear structure of the second woven fabric in this case must simply be conductive to allow electrical contact between the catalytically active layer (electrocatalyst) and the flow field or bipolar plate (for example, a woven fabric made of carbon fibers and / or carbon filaments). This structure is advantageous when it is intended to use electrocatalysts that cannot be incorporated into the fibers or cannot be manufactured into the fibers and / or filaments or cannot be endowed with long-term stability on the fibers and / or filaments or that have a higher catalytic activity than the fiber or filament material itself.

[0033] In a particularly preferred embodiment of the present invention, the first woven fabric and / or the second woven fabric are felts or nonwovens. The linear woven fabric structure from which the felts or nonwovens are constructed is fibrous. In felts and nonwovens, the fibers are laid in irregular multi-directions and adjacent fibers are joined to each other via transverse bonds. The transverse bonds of the metal fibers are preferably carried out by calendaring. Thermoplastic materials may also be fused to each other.

[0034] The nonwoven fabric or felt preferably comprises at least two types of catalytically active linear textile structures: a first type with a higher catalytic activity and a second type with a lower catalytic activity. The two relative terms "lower" and "higher" relate to the catalytic activity of each of the other catalytically active linear textile structures. A complete description of the catalytic activity is not useful here. All that matters is that the catalytic activity of one type is greater than the other. The two types of catalytically active linear structures are distributed differently in the textile fabric: one type is concentrated in a first region and the other type in a second region. The regions with linear structures of higher catalytic activity are then located closer to the membrane than the regions with linear structures of lower catalytic activity. The effect of this is that the catalytic activity of the textile structure in the interface region with the membrane is higher compared to the face of the textile remote from the membrane. It is therefore possible to use particularly active and correspondingly more expensive materials near the membrane. In places where the electrochemical reactions proceed only to a lower extent, i.e. in the regions of the textile fabric remote from the membrane, less catalytically active and cheaper materials are used. Advantageously, the linear woven structures of the type with low catalytic activity are made from particularly oxidation- or corrosion-resistant materials. A particularly high corrosion resistance of the cell components used is particularly important for efficient water electrolysis, since possible oxidation or passivation of the contact surfaces between the individual cell components during operation of the electrolyzer leads to an increase in the contact resistance. This therefore leads to an increase in the cell voltage and a decrease in efficiency as well as an increase in energy consumption. For the same reason, it is also particularly advantageous if the metal mesh, onto which the non-woven material, for example expanded metal, non-woven fabric or felt, can be fixed, is made from a particularly oxidation- or corrosion-resistant material.

[0035] The felt preferably consists entirely of fibers of catalytically active material. If the felt also contains catalytically inactive linear structures, this proportion must be small, preferably less than 50% by weight, more preferably less than 10% by weight, based on the total weight of the felt.

[0036] The felt is preferably formed from at least two felt layers, in which case the two felt layers consist of fibers of different thicknesses. In that case, the felt layer composed of finer fibers should be placed closer to the membrane than the felt layer composed of thicker fibers. The effect is that the electrodes consist of finer fibers towards the membrane. This is desirable since a higher density of catalytically active sites is required near the membrane and a higher permeability of water or electrolyte and formed gas away from the membrane. It is also possible to form the felt from three or more layers, for example three or four or five or six layers. The thickness of the fibers and / or filaments then decreases stepwise in the membrane direction from layer to layer. Correspondingly, the spatial concentration of catalytically active sites increases in the membrane direction. It is important that the felt layer has a porosity ε sufficient for the transport of water or basic electrolyte or formed gas, preferably between 50% and 90%. The porosity ε is determined by formula (3):

[0037] ε = (ρ solid -ρ porous body ) / ρ solid *100%(3)

[0038] In equation (3), ρ solid denotes the density of the solid non-porous material, and ρ porous body indicates the density of the porous body.

[0039] The porosity ε of the felt determined by this method is preferably 50% to 90% in the region in contact with the membrane and 50% to 90% in the region away from the membrane.

[0040] The diameter of the fibers and / or filaments of the felt can be determined by scanning electron microscopy (SEM).

[0041] The diameter of the felt fibers determined by this method is preferably 1 μm to 25 μm in the region in contact with the membrane and 5 μm to 1000 μm in the region away from the membrane.

[0042] The felt layers can be joined to each other by lateral bonds, which allows the felt to be handled as one component despite its layered structure, facilitating assembly of the cells.

[0043] Particularly advantageously, stainless steel filter felts of type SAE 316L can be used as electrode material. Such products are very widely available at low cost from various suppliers. This steel type contains nickel and is therefore inherently catalytically active as an undiluted material.

[0044] As already mentioned above, the variant of the invention having a catalytic layer between the cathode and the membrane has the advantage that it can contain electrocatalysts that cannot be easily applied to the textile substrate.The catalytic layer can thus contain catalytically active particles or coatings or compounds (electrocatalysts) that contain elements such as Au, Pt, Ir, Ru, Rh, Pd, Ag, C, Ni, Mn, Mo, Co, Cu, Fe, etc.

[0045] It is particularly advantageous if the catalytically active particles of the electrode catalyst are embedded in an anion-conducting polymer. Ion-conducting polymers are called ionomers. Embedding the catalytically active particles in an anion-conducting ionomer allows the hydroxide ions formed during the reduction of water at the cathode to pass directly through the membrane after the reaction. It is very particularly preferred if the ion-conducting polymer has very good adhesion to the surface of the membrane and very good conductivity of hydroxide ions. In that case there is a particularly effective integration of the catalyst particles with the membrane and a particularly good anion-conducting bond of the catalyst particles to the membrane.

[0046] However, in contrast to known CCM designs (where both sides of the membrane are coated with electrocatalysts), the membrane of the present structure preferably comprises a catalyst layer only on the cathode, hydrogen-producing side. It does not have a catalyst layer on the anode, oxygen-producing side, with the electrocatalyst integrated into the anode material on the oxygen side. Thus, the variant with a catalyst layer only on the cathode side may be considered a "half CCM cell."

[0047] The material from which the anion-conducting membrane is formed is also an ionomer. In principle, all anion-conducting ionomers can be incorporated into the electrochemical cell according to the invention and into the function of the separation active membrane material therein and / or used for immobilizing catalytically active particles. It is preferred that the same anion-conducting polymer is used as the separation active membrane material and for immobilizing the catalytically active particles in the membrane, since this ensures a particularly good anion-conducting bond of the catalytically active sites to the membrane. In this case, the same anion-conducting polymer is present in both the catalyst layer and the membrane.

[0048] It is particularly preferred to use anion conducting polymers according to structural formula (I) or (II) or (III).

[0049] Common advantages of the ionomers of structural formula (I), (II) or (III) are their good ionic conductivity, high swelling resistance in alkaline media, and low synthesis cost.

[0050] The ionomers of structural formula (I) or (II) or (III) can be used as binders for the preparation of membranes or for immobilization of electrocatalysts to catalytically active layers or inert linear woven structures.

[0051] The anion conducting polymer of structural formula (I) is defined as follows: TIFF2024544360000002.tif71170

[0052] In the formula, X is C 1 and C 2 and Z is a structural element containing a positively charged nitrogen atom bonded to one or two hydrocarbyl radicals via two bonds containing 1 to 12, preferably 1 to 6, more preferably 1 or 5 carbon atoms; 3 and C 4 and a structural element comprising a carbon atom containing at least one aromatic six-membered ring directly bonded to one of the oxygen atoms, the aromatic six-membered ring being at least one halogen radical and / or at least one C 1 -~C4 - may be substituted by an alkyl radical.

[0053] The preparation of ionomers of structural formula (I) is described in WO 2021 / 013694.

[0054] The anion conducting polymer of structural formula (II) is defined as follows: TIFF2024544360000003.tif72170

[0055] In the formula, X is C 1 and C 2 and Z is a structural element containing a positively charged nitrogen atom bonded to one or two hydrocarbyl radicals via two bonds containing 1 to 12, preferably 1 to 6, more preferably 1 or 5 carbon atoms; 3 and C 4 and a structural element containing a carbon atom containing at least one aromatic six-membered ring directly bonded to one of the oxygen atoms, the aromatic six-membered rings in positions 3 and 5 being identical or different C 1 -~C 4 - may be substituted by an alkyl radical, in particular a methyl, isopropyl or tert-butyl group, preferably a methyl group.

[0056] The preparation of ionomers of structural formula (II) is described in European Patent Application No. 21152487.1, which was not yet published at the filing date of the present application. The anion conducting polymer of structural formula (III) is defined as follows: TIFF2024544360000004.tif73170

[0057] In the formula, X is a ketone group or a sulfone group; Z is a structural element that contains at least one tertiary carbon atom and at least one aromatic six-membered ring, which is directly bonded to one of the two oxygen atoms, Y is a structural element that contains at least one nitrogen atom carrying a positive charge, which nitrogen atom is bonded to the structural element Z.

[0058] The preparation of ionomers of structural formula (III) is described in European Patent Application No. 21162711.2, which was not yet published at the filing date of the present application.

[0059] Regardless of whether the electrochemical cell comprises one or two woven fabrics (electrodes), it is advantageous for the first and / or second woven fabric to be in contact with the bipolar plate on the side remote from the membrane. What is meant here by "contact" is at least in the electrical sense, and preferably both in the electrical and mechanical sense, since the bipolar plate is electrically conductive. The contact is preferably achieved over the entire area. More preferably, a direct electrical and mechanical contact is envisaged, in which case no further material is incorporated in the cell between the electrode and the bipolar plate. In this way, the cell becomes particularly compact and cost-effective. The fluid conducting function of the woven fabric is then optimally exploited. If necessary, a fluid conductor or transport layer of a non-woven material can be incorporated between the woven fabric and the bipolar plate, for example an expanded metal or metal mesh. The fluid conductor or transport layer in that case must be electrically conductive to ensure electrical contact between the woven material and the bipolar plate. However, in this configuration there is no direct mechanical contact between the woven fabric and the bipolar plate, but rather only direct mechanical contact via a non-woven fluid conductor or transport layer. The bipolar plate can be used to make electrical contact with adjacent electrochemical cells. It is therefore possible to connect multiple electrochemical cells in a stack in a space-saving series fashion. See below.

[0060] The bipolar plates preferably consist of one of the following materials: nickel; nickel-containing alloys, such as Hastelloy, Cronin, Monel, Inconel, Incoloy, Invar, Kovar; nickel-containing steel, nickel-containing stainless steel, steels of type AISI 301, AISI 301L, AISI 302, AISI 304, AISI 304L, AISI 310, AISI310L, AISI316, AISI 316L, AISI 317, AISI 317L, AISI 321; nickel-plated steel, nickel-plated stainless steel, nickel-plated titanium, nickel-plated brass, carbon. The electrochemical cell presented here is optimized for use in alkaline membrane water electrolysis (AEM-based water electrolysis). Thus, the present invention provides for the production of hydrogen and oxygen by electrochemical decomposition of water having the following process steps: providing at least one electrochemical cell of the present invention; providing water or an aqueous electrolyte having a pH between 7 and 14; providing a voltage source; · Immersing and permeating at least one textile fabric with water or an aqueous electrolyte; contacting the anode and the cathode with a voltage drawn from a voltage source; extracting oxygen from the first textile fabric; Extracting hydrogen from the second textile fabric.

[0061] As used herein, the electrolyte contains the water to be electrolyzed. The water contains one or more compounds, such as NaOH, KOH, Na 2 CO 3 , K 2 CO 3 , NaHCO 3 , K.H.C.O. 3 By adding, it is possible to adjust the pH of the resulting electrolyte (depending on the compound) to within the range of pH 7 to pH 14.

[0062] This process can be carried out in two variants: wet and semi-dry. In the wet variant, the two compartments are filled with water or electrolyte. In other words, the first and second woven fabrics are immersed in water or electrolyte and permeated with water or electrolyte during electrolysis. In the semi-dry procedure, only one of the two compartments is filled with water or electrolyte and only one of the two woven fabrics is permeated during electrolysis, either on the anode side (first woven fabric, semi-dry case 1) or on the cathode side (second woven fabric, semi-dry case 2).

[0063] In wet variants, the two compartments on either side of the membrane are immersed in water or an aqueous basic electrolyte, which permeates the two compartments during electrolysis. Hydrogen accumulates in the water or aqueous electrolyte on the cathode side, and oxygen on the anode side. If the gas does not spontaneously bubble out of the electrolyte, the electrolyte is drawn in from both compartments, and the desired gas is released. Generally, at the beginning of the electrolysis, the gas formed is in sufficient quantity that only the formed gas dissolves in the water or basic electrolyte, but the electrolyte becomes saturated with gas very quickly, and then gas bubbles spontaneously escape from the electrolyte (a gas-electrolyte mixture is formed). For example, in wet variants, gas-liquid separation must generally be performed. To prevent mixing of the generated gases (hydrogen and oxygen), gas-liquid separation must be performed in separate devices.

[0064] Specifically, the wet process variant has the following steps: a) providing at least one electrochemical cell comprising an anode, a cathode, and an anion conducting membrane disposed between the anode and the cathode, the anode being fabricated at least in part as a first woven fabric comprising a catalytically active linear woven structure, the first woven fabric being in direct contact with the membrane; b) providing water or an aqueous electrolyte having a pH of between 7 and 14; c) providing a voltage source; d) immersing and permeating the first textile fabric with water or an electrolyte; e) immersing and permeating a second textile fabric with water or an electrolyte; f) passing water or an electrolyte through the first textile fabric; g) passing water or an electrolyte through a second textile fabric; h) contacting the anode and the cathode with a voltage drawn from a voltage source; i) drawing oxygen from the first textile fabric and / or from oxygen-enriched water or electrolyte from the first textile fabric; j) withdrawing hydrogen from the second textile fabric and / or from the hydrogen-enriched water or electrolyte from the second textile fabric; k) optionally separating hydrogen from the hydrogen-enriched water or hydrogen-enriched electrolyte; l) Optionally, separating oxygen from the oxygen-enriched water or hydrogen-enriched electrolyte. As already mentioned, the electrolysis mode of operation allows the formed gases to escape spontaneously as bubbles, rather than hydrogen and / or oxygen remaining dissolved in the water or basic electrolyte in the respective compartments. This is advantageous since no removal is necessary and the desired gas is obtained directly. As a result, the electrolysis device costs can be somewhat reduced, since fewer components are required.

[0065] The wet process with complete degassing of hydrogen and oxygen then proceeds as follows: a) providing at least one electrochemical cell comprising an anode, a cathode, and an anion conducting membrane disposed between the anode and the cathode, the anode being fabricated at least in part as a first woven fabric comprising a catalytically active linear woven structure, the first woven fabric being in direct contact with the membrane; b) providing water or an aqueous electrolyte having a pH of between 7 and 14; c) providing a voltage source; d) immersing and permeating the first textile fabric with water or an electrolyte; e) immersing and permeating a second textile fabric with water or an electrolyte; f) passing water or an electrolyte through the first textile fabric; g) passing water or an electrolyte through a second textile fabric; h) contacting the anode and the cathode with a voltage drawn from a voltage source; i) drawing oxygen from the first textile fabric and / or from oxygen-enriched water or electrolyte from the first textile fabric; j) withdrawing hydrogen from the second textile fabric and / or from the hydrogen-enriched water or electrolyte from the second textile fabric. In fact, mixed forms are also possible, in which part of the gas formed spontaneously escapes from the fabric, while another part remains dissolved in the water or electrolyte and must be separated therefrom in a separate operation.

[0066] Unlike the wet process variants, in the semi-dry variants, only the anode side (first woven fabric, semi-dry case 1) or only the cathode side (second woven fabric, semi-dry case 2) is impregnated with water or basic electrolyte. The opposite compartment remains "dry". Hydrogen gas (semi-dry case 1) or oxygen gas (semi-dry case 2) is extracted from the second woven fabric (cathode) or the first woven fabric (anode). In case 1, oxygen accumulates in the anode compartment filled with water or basic electrolyte, as in the wet variant. In case 2, hydrogen accumulates in the cathode compartment filled with water or basic electrolyte, as in the wet variant.

[0067] An advantage of the two semi-dry variants is that they do not require separation from water or from the basic electrolyte and hydrogen (case 1) or oxygen (case 2), since the corresponding electrodes are not immersed in water or the basic electrolyte and therefore the gas formed contains almost no water.

[0068] The basic concept of the semi-dry AEM process (case 1), in which water is only present on the anode side, is described in WO 2011 / 004343. Specifically, the semi-dry process variant case 1 has the following steps: a) providing at least one electrochemical cell comprising an anode, a cathode, and an anion conducting membrane disposed between the anode and the cathode, the anode being fabricated at least in part as a first woven fabric comprising a catalytically active linear woven structure, the first woven fabric being in direct contact with the membrane; b) providing water or an aqueous electrolyte having a pH of between 7 and 14; c) providing a voltage source; d) immersing and permeating the first textile fabric with water or an electrolyte; e) passing water or an electrolyte through the first textile fabric; f) contacting the anode and the cathode with a voltage derived from a voltage source; g) withdrawing hydrogen from the second textile fabric. h) withdrawing oxygen from the first textile fabric and / or from the oxygen-enriched water or electrolyte from the first textile fabric; i) optionally separating oxygen from the oxygen-enriched water or oxygen-enriched electrolyte; Thus, in the semi-dry process (case 1), there is no need for immersion of a second fabric and water or separation of hydrogen from the hydrogen-enriched electrolyte: the hydrogen formed is directly in gaseous form in the cathode compartment and contains almost no water.

[0069] In fact, in case 1, there can also be a mixed form, where part of the oxygen spontaneously escapes from the first textile fabric, and another part remains dissolved in the water or electrolyte and must be separated therefrom in a separate operation. However, if hydrogen recovery is the only objective, it is possible to omit the separation of oxygen from the water or electrolyte extracted from the first textile fabric. The oxygen remains in part in the electrolyte. As a result, the electrolyzer costs can be somewhat reduced, since fewer components are required.

[0070] If the electrolysis is carried out in such a way that only the cathode side (second textile fabric, semi-dry case 2) is immersed and permeated with water or basic electrolyte, the separation of oxygen from the water or electrolyte can be omitted. The semi-dry variant of case 2 in this case takes the following form: a) providing at least one electrochemical cell comprising an anode, a cathode, and an anion conducting membrane disposed between the anode and the cathode, the anode being fabricated at least in part as a first woven fabric comprising a catalytically active linear woven structure, the first woven fabric being in direct contact with the membrane; b) providing water or aqueous electrolytes having a pH between 7 and 14; c) providing a voltage source; d) immersing and permeating a second textile fabric with water or an electrolyte; e) passing water or a basic electrolyte through a second textile fabric; f) contacting the anode and cathode with a voltage drawn from a voltage source; g) drawing oxygen from the first textile fabric; h) withdrawing hydrogen from the second textile fabric and / or from the hydrogen-enriched water or basic electrolyte from the second textile fabric; i) Separating hydrogen from the hydrogen-enriched water or hydrogen-enriched electrolyte, as the case may be.

[0071] In fact, even in case 2, a mixed form is also possible, in which part of the hydrogen spontaneously escapes from the first textile fabric, and another part remains dissolved in the water or basic electrolyte and must be separated therefrom in a separate operation.

[0072] Common to all process variants presented here is that the porous properties of the woven fabric are exploited to guide the fluids introduced into and withdrawn from the cell and the formed gases and to facilitate their transport through the electrochemical cell. According to the invention, the woven fabric always performs the function of a porous transport layer and a flow field (fluid conductor). According to the embodiments (wet, semi-dry case 1, semi-dry case 2), the fluids guided by the woven fabric are water, liquid aqueous electrolyte, liquid electrolyte with dissolved hydrogen, liquid electrolyte with dissolved oxygen, oxygen gas or hydrogen gas. Moreover, the fluid may comprise multiple phases composed of the mentioned gases and liquids.

[0073] A particular advantage of the electrochemical cell structure presented here is that it can be used for different process variants without the need for structural modifications. As a result, the electrochemical cell manufacturer only needs to manufacture one design of the cell, and the cell user can decide which process variant (wet, semi-dry case 1, semi-dry dry case 2) is most economically viable for the application in question. In this way, by reducing the complexity, the manufacturing costs of the cell, and therefore of the electrolyzer, are also significantly reduced.

[0074] All process variants presented here are preferably carried out continuously. This means that water or aqueous basic electrolyte is continuously fed and gas, or oxygen-enriched water and / or hydrogen-enriched water or oxygen-enriched electrolyte and / or hydrogen-enriched electrolyte is continuously withdrawn. The continuous feed of water compensates for losses caused by electrolysis of the water present in the water or electrolyte. Otherwise, the water will be completely consumed over time and the electrochemical reaction will stop. A batch process is conceivable, but not preferred on an industrial scale, in which the electrochemical cell is completely filled or at least its anode or cathode compartment is filled with water or basic electrolyte, which is then electrolyzed until the cell or the anode or cathode compartment is empty.

[0075] Water electrolysis using the electrochemical cell according to the invention preferably has a current of at least 300 mA / cm 2, or better still at least 500 mA / cm 2 The cells achieve higher process intensity at these higher current densities, which means more hydrogen production per unit of cell area. The current density is calculated from the quotient of the current flowing between the electrodes and the effective area of ​​the cell, i.e., the percentage of the membrane or electrode in contact with the electrolyte.

[0076] The process according to the invention is preferably carried out in an electrolyser comprising at least two electrochemical cells according to the invention sharing a common bipolar plate. This means that the bipolar plate is simultaneously in electrical contact with the anode of the first electrochemical cell of the electrolyser and with the cathode of the second electrochemical cell of the electrolyser. In this case two adjacent cells are connected in series. Such electrolyser forms a further part of the subject matter of the present invention.

[0077] The advantage of an electrolyzer in which adjacent cells each share a bipolar plate is its compact stack structure and therefore its small structural size. Preferably, the electrolyzer includes three or more adjacent cells sharing a common bipolar plate. Depending on the size of the individual electrochemical cells and the power required, it is possible to stack up to 500 cells via their bipolar plates to form an electrolyzer.

[0078] A further advantage of the electrolyser of the present invention is that it can be manufactured with a high degree of automation, since the individual components of the electrochemical cell can be stacked very efficiently by robots, thus further reducing the manufacturing costs of the electrolyser.

[0079] Likewise, the present invention provides a process for the manufacture of an electrolysis device comprising at least two electrochemical cells according to the present invention sharing a common bipolar plate, when during the course of manufacture the following components are stacked directly on top of each other in this order: In this process sequence, the stack goes from anode to cathode. a) a first woven fabric; b) an anion conducting membrane, which may be provided with a catalyst layer; c) a second textile fabric, which may be provided with a catalyst layer; d) bipolar plates; e) a first woven fabric; f) an anion conducting membrane, which may be provided with a catalyst layer; g) A second textile fabric, which may be provided with a catalyst layer. Stacking from cathode to anode is also possible. The stacking order is as follows: a) a second textile fabric, which may be provided with a catalyst layer; b) an anion conducting membrane, which may be provided with a catalyst layer; c) a first woven fabric; d) bipolar plates; h) a second textile fabric, which may be provided with a catalyst layer; i) an anion conducting membrane, which may be provided with a catalyst layer; j) a first woven fabric.

[0080] Both stacking sequences result in the same electrolyser.

[0081] In order to bring three or more adjacent cells according to the invention into contact with each other via a common bipolar plate according to the invention, it is possible to carry out the stacking sequence repeatedly, after each run it being necessary to insert a bipolar plate.

[0082] For example, if three cells are stacked from anode to cathode, the stacking order is as follows: a) a first woven fabric; b) an anion conducting membrane, which may be provided with a catalyst layer; c) a second textile fabric, which may be provided with a catalyst layer; d) bipolar plates; e) a first woven fabric; f) an anion conducting membrane, which may be provided with a catalyst layer; g) a second textile fabric, which may be provided with a catalyst layer; h) bipolar plates; i) a first woven fabric; j) an anion conducting membrane, which may be provided with a catalyst layer; k) A second textile fabric, which may be provided with a catalyst layer.

[0083] Every stack may be provided with end plates at both ends of the stack, which are correspondingly connected in a monopolar manner.

[0084] The stacking is preferably automated, especially using a robot.

[0085] The manufacture of the electrolyzer is particularly effective when the first and second textile fabrics are made of the same material. In this case, there are fewer component types, which increases the assembly speed and reduces the cost of the electrolyzer. Again, the stacking process can be better performed with a robot, since the robot does not need to distinguish between anodes and cathodes, but instead only needs to install one type of electrode.

[0086] The manufacture of the electrolyzer is furthermore efficient if the first and / or second textile fabrics are electrically connected and mechanically fixed to the bipolar plate before assembly of the electrolyzer so as to form a component. This can be achieved, for example, by spot welding the two textile fabrics and the bipolar plate together. In this way, the number of component types is further reduced, thereby further increasing the assembly speed and reducing the cost of the electrolyzer. The spot welding can be performed by a separate robot or by a robot that later assembles the cell. The invention will now be illustrated by examples. For this purpose, the figures show: [Brief description of the drawings]

[0087] [Figure 1a] FIG. 1 is a schematic diagram of the design of a first embodiment of an electrochemical cell. [Figure 1b]FIG. 1A is a schematic diagram of the operation of a first embodiment of an electrochemical cell (FIG. 1a) in a wet process variant. [Figure 1c] FIG. 1A is a schematic diagram of the operation of a first embodiment of an electrochemical cell (FIG. 1a) in a semi-dry process variant (case 1—“dry cathode”). [Figure 1d] FIG. 1B is a schematic diagram of the operation of a first embodiment of an electrochemical cell (FIG. 1a) in a semi-dry process variant (Case 2—“Dry anode”). [Figure 2a] FIG. 2 is a schematic diagram of the design of a second embodiment of an electrochemical cell. [Figure 2b] FIG. 2b is a schematic diagram of the operation of a second embodiment of an electrochemical cell (FIG. 2a) in a wet process variant. [Figure 2c] FIG. 2B is a schematic diagram of the operation of a second embodiment of an electrochemical cell (FIG. 2a) in a semi-dry process variant (Case 1—“Dry cathode”). [Figure 2d] FIG. 2B is a schematic diagram of the operation of a second embodiment of an electrochemical cell (FIG. 2a) in a semi-dry process variant (Case 2—“Dry anode”). [Diagram 3] FIG. 1 shows a schematic diagram of one operational variant of an electrolysis device comprising two electrochemical cells (FIG. 1a) according to a first embodiment. [Figure 4] FIG. 2a is a schematic diagram of the design of an electrolyser comprising two electrochemical cells according to a second embodiment. [Diagram 5] 1 is a graph showing UI characteristics of Examples 1 to 4 and 8. [Figure 6] 1 is a graph showing UI characteristics of Examples 4 to 7 and 9. [Figure 7] 1 is a graph showing UI characteristics of Examples 4 and 10 to 13. [Figure 8] 1 is a graph showing UI characteristics of Examples 4 and 13 to 16. [Figure 9] 1 is a graph showing UI characteristics of Examples 13 and 17 to 20. [Figure 10] 1 is a graph showing UI characteristics of Examples 21 to 25. [Figure 11]1 is a graph showing UI characteristics of Examples 4 and 26 to 29. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0088] Figure 1a shows a schematic diagram of a first embodiment of an electrochemical cell 0 in cross section. It comprises an anode 1, a cathode 2, and an anion-conducting membrane 3 disposed between the anode 1 and the cathode 2. The anode 1 and the cathode 2 are each fabricated as a woven fabric comprising Ni-containing fibers.

[0089] Membrane 3 is a two-dimensional membrane made from an ionomer produced according to Example 3 of WO 2021 / 013694. Membrane 3 was produced according to Example 4 of WO 2021 / 013694. Anode 1 and cathode 2 are each directly adjacent to membrane 3. Anode 1 and cathode 2 are each in contact with end plate 4 on the side remote from membrane 3.

[0090] The active areas of the anode 1 and cathode 2 extend perpendicular to the plane of the drawing. In particular, the electrochemical cell 0 does not have a separate flow distributor or a separate porous transport layer (PTL) or a separate catalytically active catalyst layer. The functions of the flow distributor and PLT are assumed by the anode 1 and the cathode 2 themselves, since they consist of a woven fabric that is simultaneously fluid conductive. The fibrous material contains nickel and iron. In the simplest case, the fibrous material is generally stainless steel containing nickel and iron. In the operation of the cell, the oxidation of nickel and iron forms catalytically active mixed Ni-Fe oxides or mixed Ni-Fe hydroxides. As a result, the fibrous material provides the catalytically active material and no additional catalyst layer is necessary.

[0091] The electrochemical cell 0 allows for three operating modes: wet, semi-dry case 1 and semi-dry case 2.

[0092] Figure 1b is a schematic diagram of the operation of the electrochemical cell of Figure 1a in a wet process variant, where the anode 1 and cathode 2 are immersed in and permeated with water or a basic electrolyte in an electrolytic operation.

[0093] Figure 1c shows a variant of the semi-dry process in which only the anode 1 of the electrochemical cell 0 of Figure 1a is immersed in and permeated by water or a basic electrolyte in the electrolysis operation (semi-dry case 1). The cathode 2 remains dry.

[0094] FIG. 1d shows a variant of the semi-dry process in which only the cathode 2 of the electrochemical cell 0 of FIG. 1a is immersed in and permeated with water or a basic electrolyte in the electrolysis operation (semi-dry case 2), while the anode 1 remains dry.

[0095] FIG. 2a shows a schematic diagram of the design of a second embodiment of an electrochemical cell 0 in cross section. It comprises an anode 1, a cathode 2, and an anion-conducting membrane 3 arranged between the anode 1 and the cathode 2. The anode 1 and the cathode 2 are each made as a woven fabric comprising Ni-containing fibers. The membrane 3 is a two-dimensional membrane made from an ionomer produced according to Example 3 of WO 2021 / 013694. The membrane 3 was produced according to Example 4 of WO 2021 / 013694. Two electrodes (anode 1 and cathode 2) are directly adjacent to the membrane 3. The anode 1 and the cathode 2 are each in contact with an end plate 4 on the side remote from the membrane 3.

[0096] The second embodiment is characterized by a catalytic layer 5 arranged between the cathode 2 and the membrane 3. The catalytic layer 5 may here be applied to the cathode 2 and / or to the cathode side of the membrane 3. The catalytic layer 5 comprises catalytically active particles or catalytically active coatings (electrocatalysts) immobilized on the cathode 2 without the use of ionomers (Examples 11-12), or immobilized on the cathode 2 with the use of ionomers (Examples 1-10), or immobilized on the membrane 3 via ionomers (Examples 13-20). The catalytically active particles or catalytically active coatings are Au, Pt, Rh, Ru, Pd, Ag, Ni, Co, Cu, Fe, Mn, Mo-containing metal particles or alloys or coatings or compounds, such as sulfides, selenides, oxides, mixed oxides, hydroxides, mixed hydroxides, spinels or perovskites, with particle sizes or coating thicknesses between 1 nm and 10 μm. The catalytically active particles may be unsupported or may be made of carbonaceous materials, such as carbon black or charcoal, or oxides, such as CeO 2 , TiO 2 Or WO 3 The concentration of active material may be less than 0.01 mg / cm based on the membrane or electrode area (cathode 2). 2 ~25mg / cm 2 , preferably 0.05 mg / cm 2 ~5mg / cm 2 The thickness of the particle-containing catalyst layer is 1 μm to 500 μm, preferably 5 μm to 100 μm. The ionomer is the same material from which the membrane 3 is made (example 3 of WO 2021 / 013694). The membrane 3, due to its active catalyst layer 5, shall be considered as a "catalyst-coated membrane" -CCM-, and the cathode 2, due to its active catalyst layer 5, shall be considered as a "catalyst-coated substrate" -CCS.

[0097] The anode 1, cathode 2 and end plate 4 in the second embodiment (FIG. 2a) are similar to those in the first embodiment (FIG. 1a). Again, components 1, 2, 3 and 4 are in direct contact with each other with catalyst layer 5 disposed between cathode 2 and membrane 3. However, this is not contradictory since catalyst layer 5 is considered as a component of cathode 2 (CCS approach) or membrane 3 (CCM approach).

[0098] The electrochemical cell 0 of FIG. 2a allows for three modes of operation: wet, semi-dry case 1 and semi-dry case 2.

[0099] FIG. 2b shows a wet process variant in which the anode 1 and cathode 2 are immersed in and permeated with water or a basic electrolyte in an electrolytic operation.

[0100] FIG. 2c shows a semi-dry process variant where only the anode 1 is immersed in and permeated by water or basic electrolyte during the electrolysis operation (Semi-dry case 1).

[0101] FIG. 2d shows a semi-dry process variant where only the cathode 2 is immersed in and permeated by water or basic electrolyte during the electrolysis operation (Semi-dry Case 2).

[0102] 3 shows a schematic diagram of a first electrolyser 6 in wet operation. The electrolyser 6 comprises two adjacent electrochemical cells 0 according to a first embodiment, which are of identical construction and contacted via a common bipolar plate 7.

[0103] For the execution of water electrolysis using the first electrolyser 6, all electrodes are immersed in water or a basic electrolyte and permeated with it successively in the electrolysis operation. This mode of operation corresponds to the process variant described above as "wet", since all the textile fabrics are immersed and permeated with water or a basic electrolyte. A voltage acting between the anode 1 and the cathode 2 is then applied to each cell. This effect, according to the above-mentioned principles, is the electrolysis of water and the generation of hydrogen (H 2) and oxygen (O 2 ) is the associated release of oxygen (O 2 ), hydrogen (H 2 ) and non-electrolyzed water (H 2 O) or basic electrolyte is withdrawn from the anode 1 and the cathode 2 correspondingly, and water and basic electrolyte are pumped continuously through the anode 1 and the cathode 2.

[0104] 4 shows a schematic diagram of a second electrolyser 8 in operation. The second electrolyser 8 comprises two adjacent electrochemical cells 0 according to a second embodiment, which are of identical construction and contacted via a common bipolar plate 7.

[0105] For the execution of water electrolysis using the second electrolyser 8, all electrodes are immersed in and permeated with water or a basic electrolyte in the electrolysis operation. This mode of operation corresponds to the process variant described above as "wet", since both felts are immersed and permeated with water or a basic electrolyte. A voltage acting between the anode 1 and the cathode 2 is then applied to each cell. This effect, according to the principles described above, is the electrolysis of water and the production of hydrogen (H 2 ) and oxygen (O 2 ) and the associated release of oxygen (O2), hydrogen (H2) and non-electrolyzed water (H2O) or basic electrolyte are correspondingly withdrawn from the anode 1 and cathode 2, and water and basic electrolyte are continuously pumped through the anode 1 and cathode 2. EXAMPLES

[0106] All examples include an anode 1, a cathode 2, a membrane 3, and an active area of ​​16 cm 2This was carried out in an electrochemical cell consisting of two end plates 4 with a 1.5 mm wide channel on one side and a 2.5 mm wide channel on the other side. This was carried out in two different types of end plates in each case on the cathode and cathode sides: type I end plate (with a flow distributor in the form of an elongated channel of 1.5 mm width, with one feed and one drain per channel) and type II end plate (without flow distributor, with a 1.5 mm wide channel on one side and a 2.5 mm wide channel on the other side) in 10 circular feeds with D = 1.5 mm on the opposite side in = 1.5 mm). Membrane 3 is a two-dimensional membrane made from an ionomer produced according to Example 3 of WO 2021 / 013694. Membrane 3 was produced according to Example 4 of WO 2021 / 013694 and has a thickness of 50 μm. Membrane 3 was ion-exchanged in 1 M KOH at 60 ° C for 24 h before each experiment. The electrolyte used was 1 M KOH, which was pumped through anode 1 and / or cathode 2 at 50 ml / min. All experiments were carried out at 60 ° C with only the electrolyte temperature controlled. The individual special features of each example are described separately.

[0107] The following materials were utilized: · SAE 316L stainless steel felt (2 plies (ply 1 - finer 4μm fibers, ply 2 - coarser 8μm fibers, thickness = 300μm, porosity = 80%, sample name "Steel felt"); · SAE 316L stainless steel felt (1 ply composed of 2 μm fibers, thickness = 200 μm, porosity = 80%, sample name "1L-2 μm steel felt"); · SAE 316L stainless steel felt (1 ply composed of 4 μm fibers, thickness = 270 μm, porosity = 80%, sample name "1L-4 μm steel felt"); · SAE 316L stainless steel felt (1 ply composed of 8 μm fibers, thickness = 350 μm, porosity = 80%, sample name "1L-8 μm steel felt"); · Nickel felt (S80422, thickness = 300 μm, porosity = 80%, sample name "Ni felt", Stanford Advanced Materials, USA); · Carbon fiber web (TGP-H120, thickness = 370 μm, porosity = 78%, sample name "Carbon fiber web", Toray Industries, Inc., Japan); · Pt / C (60 wt% Pt on carbon support, product number AB204745, abcr GmbH, Germany); Ir (99.8% Ir, product number 12071, Alfa Aesar GmbH&Co KG, Germany).

[0108] A first test ink containing catalytically active Pt / C and a second test ink containing catalytically active Ir were prepared as follows:

[0109] The basis for the preparation of test inks with ionomers is the preparation of an ionomer solution. Examples of suitable solvents are N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC) or dimethylsulfoxide (DMSO), with DMSO being preferred as it is classified as a non-hazardous substance. The proportion of polymer is between 10 mg / ml and 500 mg / ml, preferably between 25 mg / ml and 200 mg / ml.

[0110] The mass ratio of ionomer to catalytically active material is, for example, 1:1 to 1:20 or 1:3 to 1:5 in the case of platinum on carbon (Pt / C) or iridium (Ir) based catalysts.

[0111] First, the catalyst and ionomer solutions are dispersed (e.g., mixed under shear action) to adjust the particle size (d in the range of 0.1 μm to 50 μm). 50) and dispersion by ULTRA-TURRAX® dispersing system (IKA, Staufen, Germany) or a three-roll mill (e.g. EXAKT, Norderstedt, Germany)), which can then be applied directly (e.g. by screen printing or knife coating methods). It is then possible to prepare an aqueous dispersion, in particular for application by a spraying process, in which case the catalyst can be applied by ultrasound or a dispenser (e.g. further particle size: d 50 The ionomer solution is first dispersed in a solution of water and a lower alcohol (preferably ethanol, 1-propanal or 2-propanol) under the operation of an ULTRA-TURRAX® dispersion system (IKA, Staufen, Germany) that adjusts the particle size in the range of 0.1 μm to 50 μm, and then an ionomer solution (preferably 50 mg / ml) is added, followed by further dispersion under ultrasonic waves. Here, the solids concentration is 5 mg / ml to 100 mg / ml, preferably 10 mg / ml to 25 mg / ml. The mg / ml unit of the ionomer solution is based on the mass of the polymer / volume of the solvent or dispersion to the mass of the catalyst / volume of the liquid components.

[0112] The ionomers used in the preparation of the test inks are materials prepared as described in Example 3 of WO 2021 / 013694. Table 1 shows the compositions of the test inks.

[0113] [Table 1]

[0114] The preparation of anode 1 or cathode 2 coated with the test ink (both as CCS approach) or membrane 3 coated with test ink #1 (CCM approach) was carried out as follows.

[0115] The Pt / C test ink #1 or Ir-containing test ink #2 described above was sprayed onto the selected substrate (carbon fiber web or steel felt) using a PRISM 400 ultrasonic spray coater (Ultrasonic Systems, Inc, Haverhill, MA, USA) or, in the case of the Pt / C-containing test ink #1, was also sprayed directly onto one side (i.e., unilaterally) of the membrane 3. The ink was continuously stirred during the process and the substrate and membrane 3 were maintained at a temperature of 60° C., resulting in the dispersant continuously evaporating and the electrocatalyst remaining as a thin solid layer on the substrate or membrane surface. The resulting Pt loading was 0.6 mg Pt / cm 2 The amount of Ir supported was 1 mg. Ir / cm 2 It was.

[0116] In the case of direct one-sided coating of the membrane 3, an additional porous transport layer (carbon fiber web or steel felt) was placed on the cathode side between the end plate and the one-sided coated membrane 3 in the electrolysis tests.

[0117] As an alternative to the spraying method, sputtering of a thin 50 nm Pt layer onto the surface of the selected substrate (carbon fiber web or steel felt) was used. This was done using a Q150R ES PLUS sputtering machine (Quorum Technologies Ltd., UK), with control of the layer thickness being performed by an installed layer thickness monitor.

[0118] For a better overview, the conditions and ingredients used in the individual examples are summarized in Table 2.

[0119] [Table 2] TIFF2024544360000007.tif71170 Table 2: Summary of components used in the individual examples. [C] stands for cathode and [A] for anode. Details in the "Transport layer" column indicate whether an additional transport layer was used in the electrolysis test (carbon fiber web or steel felt) or not ("none"). "Substrate" indicates which material was used as substrate for electrocatalyst coating or as electrode without electrocatalyst coating. Electrode type indicates whether the CCS approach (substrate coated with electrocatalyst) or the CCM approach (membrane coated with electrocatalyst) was used. Details in the "Flow field" column indicate whether type I end plates (with flow distributor) or type II end plates (without flow distributor) were used. The details in the "Electrolyte" column indicate whether the corresponding electrode was operated "with" electrolyte (i.e., the electrode was immersed in and pumped through water or a basic electrolyte, i.e., wet process variants) or "without" electrolyte (i.e., the electrode was not immersed in or pumped through water or a basic electrolyte, i.e., semi-dry process variants).

[0120] Example 1 Carbon fiber web was selected as the substrate to fabricate the cathode. The substrate was coated with a Pt / C-containing ink using a PRISM 400 ultrasonic spray coater (Ultrasonic Systems, Inc, Haverhill, MA, USA), the preparation of which was described above. The resulting Pt loading was 0.6 mg / cm. 2 It was.

[0121] Steel felt was selected as the substrate to fabricate the anode. The substrate (the side with the finer 4 μm fibers) was coated with an Ir-containing ink using a PRISM 400 ultrasonic spray coater (Ultrasonic Systems, Inc, Haverhill, MA, USA), the preparation of which was described above. The resulting loading of Ir was 1 mg / cm. 2 The steel felt incorporated finer 4 μm fibers toward the membrane.

[0122] I-type end plates were used on both ends.

[0123] Example 2 This is the same as Example 1, except that a type II end plate was used on the anode side.

[0124] Example 3 The cathode utilized was the same electrode as in Example 1. The anode utilized was steel felt (the side with the finer 4 μm fibers) coated with 50 nm of Pt as an electrocatalyst. The steel felt incorporated the finer 4 μm fibers towards the membrane.

[0125] Example 4 Similar to Example 3, except that the anode utilized was uncoated steel felt. The steel felt incorporated finer 4 μm fibers toward the membrane.

[0126] Example 5 Similar to Example 4, except that the cathode was not immersed in or permeated with the electrolyte during electrolysis (semi-dry process variant, semi-dry case 1).

[0127] Example 6 Similar to Example 4, except that the anode was not immersed in or permeated with the electrolyte during electrolysis (semi-dry process variant, semi-dry case 2).

[0128] Example 7 Steel felt was selected as the substrate to fabricate the cathode. The substrate (the side with the finer 4 μm fibers) was coated with a Pt / C-containing ink using a PRISM 400 ultrasonic spray coater (Ultrasonic Systems, Inc, Haverhill, MA, USA), the preparation of which was described above. The resulting Pt loading was 0.6 mg / cm. 2 The anode utilized was uncoated steel felt incorporating finer 4 μm fibers toward the membrane.

[0129] Example 8 The cathode was the same as in Example 1. The anode utilized was uncoated steel felt incorporating finer 4 μm fibers towards the membrane. Type I end plates were used on the cathode side and Type II end plates were used on the anode side.

[0130] Example 9 This is the same as Example 8, except that an I-type end plate was used on the cathode side and a II-type end plate was used on the anode side.

[0131] Example 10 The cathode was the same as in Example 1. The anode utilized was uncoated Ni felt.

[0132] Example 11 The cathode utilized was steel felt coated (the side with the finer 4 μm fibers) with 50 nm of Pt as an electrocatalyst, and the anode utilized was uncoated steel felt.

[0133] Example 12 The cathode utilized was a carbon fiber web coated with 50 nm of Pt as an electrocatalyst, and the anode utilized was uncoated steel felt incorporating finer 4 μm fibers toward the membrane.

[0134] Example 13 The cathode was fabricated by single-sided coating of the membrane (cathode side only) directly with the Pt / C-containing ink, the preparation of which was described above, using a PRISM 400 ultrasonic spray coater (Ultrasonic Systems, Inc, Haverhill, MA, USA). The resulting Pt loading was 0.6 mg / cm. 2 The porous transport layer used on the cathode side was a carbon fiber web. The anode utilized was uncoated steel felt with finer 4 μm fibers embedded toward the membrane.

[0135] Example 14 Similar to Example 13, except that the cathode was not immersed in or pumped through the electrolyte during electrolysis (semi-dry process variant, semi-dry case 1).

[0136] Example 15 Similar to Example 13, except that the anode was not immersed in or pumped through the electrolyte during electrolysis (semi-dry process variant, semi-dry case 2).

[0137] Example 16 Similar to Example 13, except that the porous transport layer used on the cathode side was steel felt incorporating finer 4 μm fibers towards the membrane.

[0138] (Example 17) Same as Example 13, except that a type II end plate was used on the cathode side.

[0139] (Example 18) Similar to Example 17, except that the cathode was not immersed in or permeated with electrolyte during electrolysis (semi-dry process variant, semi-dry case 1).

[0140] (Example 19) Similar to Example 17, except that the anode was not immersed in or permeated with the electrolyte during electrolysis (semi-dry process variant, semi-dry case 2).

[0141] (Example 20) Similar to Example 17, except that the porous transport layer used on the cathode side was steel felt incorporating finer 4 μm fibers towards the membrane.

[0142] Example 21 The anode 1 utilized was uncoated steel felt incorporating finer 4 μm fibers towards the membrane, and the cathode 2 utilized was uncoated Ni felt.

[0143] Example 22 Similar to Example 21, except that the cathode was not immersed in or pumped through the electrolyte during electrolysis (semi-dry process variant, semi-dry case 1).

[0144] Example 23 Similar to Example 21, except that the anode was not immersed in or pumped through the electrolyte during electrolysis (semi-dry process variant, semi-dry case 2).

[0145] (Example 24) Same as Example 21, except that a type II end plate was used on the anode side.

[0146] (Example 25) Same as Example 21, except that a type II end plate was used on the cathode side.

[0147] (Example 26) The steel felt is similar to Example 4, except that the coarser 8 μm fibers were incorporated towards the membrane (the finer 4 μm fibers were not oriented towards the membrane, hence the "mis"incorporation).

[0148] Example 27 Similar to Example 4, except the anode incorporated was one ply of 1L-2 μm steel felt.

[0149] (Example 28) Similar to Example 4, except the anode incorporated was one ply of 1L-4 μm steel felt.

[0150] (Example 29) Similar to Example 4, except the anode incorporated was one ply of 1L-8 μm steel felt.

[0151] conclusion In Figure 11, 300 mA / cm 2 It is clear that in the case of higher current densities above 1000 kcal / s, in the case of the "mis" incorporation of the steel felt as well as in the case of the use of one ply of steel felt composed of 2 μm, 4 μm and 8 μm steel fibres, a higher cell voltage is required to achieve the same current density. This means that the power consumed by the cell increases. As a result, the energy demand in the case of a process with a single ply of felt or a mis-incorporated felt is greater than in the case of a two-ply felt with the finer fibres arranged in the direction of the membrane. The energy cost per unit of hydrogen produced is therefore higher. 500mA / cm 2 It is also evident in Figure 11 that at higher current densities above 0.1, the advantage of a correctly incorporated multi-ply felt is even more evident. Thus, the energy savings achievable by correct use of a multi-ply felt are particularly large when the electrolyser is operated at high process intensities. [Explanation of symbols]

[0152] 0 Electrochemical Cell 1. First woven fabric (anode) 2. Second woven fabric (cathode) 3 Anion-conducting membrane 4 End Plate 5 Catalyst layer 6 Electrolysis device according to a first embodiment, comprising two adjacent electrochemical cells 0 contacted via a common bipolar plate 7 7 Bipolar Plates 8 Electrolysis device according to a second embodiment, comprising two adjacent electrochemical cells 0 contacted via a common bipolar plate 7 H 2 O Water or alkaline electrolytes H 2 hydrogen O 2 oxygen

Claims

1. 1. An electrochemical cell comprising: an anode, a cathode, and an anion-conducting membrane disposed between the anode and the cathode, wherein the anode is at least partially fabricated as a first woven fabric comprising catalytically active linear woven structures, the first woven fabric being in direct contact with the membrane, the first woven fabric being a felt or nonwoven fabric, the felt or nonwoven fabric comprising at least two types of catalytically active linear woven structures, one type having a higher catalytic activity than the other types, the type of catalytically active linear woven structure having the higher catalytic activity being concentrated in an area of ​​the woven fabric more closely adjacent to the membrane than in an area of ​​the woven fabric where the type of catalytically active linear woven structure having the lower catalytic activity is concentrated.

2. 10. The electrochemical cell of claim 1, wherein the catalytically active linear woven structure is made of a nickel-containing material.

3. 3. The electrochemical cell of claim 2, wherein the nickel-containing material is selected from the group consisting of the following materials: nickel, nickel-containing alloys.

4. 10. The electrochemical cell of claim 1, wherein the catalytically active linear woven structure comprises a substrate having a catalytically active coating thereon, the catalytically active coating comprising at least one element selected from the group consisting of Au, Pt, Ir, Rh, Ru, Pd, Ag, Ni, Co, Cu, Fe, Mn, and Mo, or a compound of said selected elements.

5. 5. The electrochemical cell of claim 4, wherein the catalytically active coating is polymer-free.

6. 5. The electrochemical cell of claim 4, wherein the substrate material is selected from the group consisting of the following materials: nickel, nickel-containing alloys, titanium, and carbon.

7. 10. The electrochemical cell of claim 1, wherein the cathode is at least partially fabricated as a second woven fabric.

8. 8. The electrochemical cell of claim 7, wherein the second woven fabric comprises a catalytically active linear woven structure.

9. 9. The electrochemical cell of claim 8, wherein the second textile fabric is in direct contact with the membrane.

10. 8. The electrochemical cell of claim 7, wherein a catalyst layer is disposed between the second textile fabric and the membrane.

11. 10. The electrochemical cell of claim 1, wherein the second woven fabric is a felt or nonwoven fabric.

12. 2. The electrochemical cell of claim 1, wherein the felt or nonwoven fabric is formed from at least two felt or nonwoven fabric layers, the fibers and / or filaments of a first layer differing in diameter from the fibers and / or filaments of a second layer, the layer with finer fibers and / or filaments being positioned closer to the membrane than the layer with coarser fibers and / or filaments.

13. 11. The electrochemical cell of claim 10, wherein the catalytic layer contains catalytically active particles and / or a catalytically active coating, the catalytically active particles and / or the catalytically active coating containing elements selected from the group consisting of the following elements: Au, Pt, Ru, Rh, Pd, Ag, C, S, Se, Ni, Mo, Mn, Co, Cu, Fe, or compounds of the selected elements.

14. 14. The electrochemical cell of claim 13, wherein the catalytically active particles are embedded in an anion-conducting polymer.

15. 15. The electrochemical cell of claim 14, wherein the anion-conducting polymer is also present in the membrane.

16. 2. The electrochemical cell according to claim 1, characterized in that the first textile fabric and / or the second textile fabric are in at least electrical contact with the bipolar plate remote from the membrane.

17. 17. The electrochemical cell of claim 16, wherein the bipolar plates are made of a material selected from the group consisting of: nickel; nickel-containing alloys; nickel-plated steel, nickel-plated stainless steel, nickel-plated titanium, nickel-plated brass, and carbon.

18. 1. A method for producing hydrogen and oxygen by electrochemical decomposition of water, comprising: - providing at least one electrochemical cell according to claim 1; providing water or an aqueous electrolyte having a pH of 7 to 14; - providing a voltage source; - Immersing and permeating at least one textile fabric with water or an aqueous electrolyte; contacting the anode and cathode with a voltage derived from said voltage source; - withdrawing oxygen from said first textile fabric; extracting hydrogen from said second textile fabric.

19. 19. The method of claim 18, comprising the steps of: a) passing water or an electrolyte through the first textile fabric; b) passing water or an electrolyte through said second textile fabric; c) extracting water or electrolytes enriched with oxygen and / or gaseous oxygen from said first textile fabric; d) extracting water or electrolyte enriched with hydrogen and / or gaseous hydrogen from said second textile fabric; e) optionally separating hydrogen from the hydrogen-enriched water or the hydrogen-enriched electrolyte; f) optionally separating oxygen from said oxygen-enriched water or said oxygen-enriched electrolyte.

20. 19. The method of claim 18, comprising the steps of: a) passing water or an electrolyte through the first textile fabric; b) withdrawing gaseous hydrogen from said second textile fabric; c) extracting water or electrolytes enriched with oxygen and / or gaseous oxygen from said first textile fabric; d) optionally separating oxygen from said oxygen-enriched water or said oxygen-enriched electrolyte.

21. 19. The method of claim 18, comprising the steps of: a) passing water or an electrolyte through said second textile fabric; b) withdrawing gaseous oxygen from said first textile fabric; c) extracting water or electrolyte enriched with hydrogen and / or gaseous hydrogen from said second textile fabric; d) optionally separating hydrogen from said hydrogen-enriched water or said hydrogen-enriched electrolyte.

22. 20. An electrolysis apparatus for carrying out the method of claim 18, comprising at least two electrochemical cells of claim 16 sharing a common bipolar plate.

23. 23. A method of manufacturing an electrolyzer according to claim 22, in which the following components are stacked directly on top of each other in the following order: a) a first textile fabric; b) an anion conducting membrane, which may be provided with a catalyst layer; c) a second textile fabric, optionally provided with a catalyst layer; d) bipolar plates; e) a first textile fabric; f) an anion conducting membrane, which may be provided with a catalyst layer; g) A second textile fabric, which may be provided with a catalyst layer.

24. 23. A method of manufacturing an electrolyzer according to claim 22, in which the following components are stacked directly on top of each other in the following order: a) a second textile fabric, which may be provided with a catalyst layer; b) an anion conducting membrane, which may be provided with a catalyst layer; c) a first textile fabric; d) bipolar plates; e) a second textile fabric, optionally provided with a catalyst layer; f) an anion conducting membrane, which may be provided with a catalyst layer; g) a first woven fabric;

25. 23. A method of manufacturing an electrolysis device according to claim 22, wherein the first and / or second textile fabrics are electrically connected and mechanically secured to the bipolar plates prior to assembly of the electrolysis device.

26. At least 300 mA / cm ２ or 500 mA / cm ２ 20. The method of claim 18, wherein the current density is

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