Electrode for alkaline water electrolysis, electrolysis cell comprising such an electrode and method for producing such an electrode

Abstract

The invention relates to an electrode (10) for use in alkaline water electrolysis, comprising a metal substrate (12) on which a catalyst layer (18) is applied at least in some sections, wherein the catalyst layer has a contact surface (20) in contact with the metal substrate and an opposite surface (22), wherein the catalyst layer has a Raney nickel material (24), wherein the catalyst layer also has metal particles (26) made of a metal alloy different from the Raney nickel material, wherein at least a partial number of these metal particles are arranged in such a way that they form the contact surface in some sections.

Description

[0001]

[0002] Title: Electrode for alkaline water electrolysis, electrolysis cell comprising such an electrode and method for manufacturing such an electrode

[0003] Description

[0004] The invention relates to an electrode for alkaline water electrolysis, an electrolysis cell comprising such an electrode, and a method for manufacturing such an electrode.

[0005] Alkaline water electrolysis is a well-known electrolysis process for producing hydrogen and oxygen from water, which has proven to be a promising technology for the industrial production of hydrogen, e.g. for use in fuel cells, particularly in the context of the energy transition.

[0006] A typical electrolysis cell for the alkaline electrolysis of water (also called an electrolyzer) comprises a first electrode (cathode) and a second electrode (anode), between which a gas-tight separator, in particular a so-called diaphragm, is arranged. During operation, the electrodes are surrounded by potassium hydroxide solution (KOH) as the electrolyte.

[0007] Electrodes for alkaline water electrolysis and methods for their production are generally known from the prior art, e.g. from DE 102022 124917 B3.

[0008] Expanded metal mesh or wire mesh, for example, are used as substrates. So-called "Raney nickel alloys" have proven particularly advantageous as catalyst materials. These Raney nickel alloys primarily consist of nickel-aluminum alloys, which have a structure comprising an aluminum-rich phase and an aluminum-poor phase. The aluminum-rich phase can be leached out, particularly by etching with potassium hydroxide (typically referred to as "leaching"), resulting in a porous structure. Due to their porosity, such leached Raney nickel alloys exhibit particularly high catalytic activity. However, there is room for improvement regarding the durability and mechanical stability of Raney nickel-based catalyst layers.

[0009] In EP 4 198 174 Al, in contrast to catalyst layers based on Raney nickel, an anode for use in alkaline water electrolysis is proposed in which a lamellar structure of nickel areas and aluminium areas is first created on a substrate in the form of an expanded metal grid and subsequently the aluminium areas are removed with the formation of pores in the micrometer range.

[0010] The invention addresses the problem of providing electrodes with durable and mechanically stable catalyst layers based on Raney nickel.

[0011] This problem is solved by an electrode with the features of claim 1. The electrode is specifically designed for use in an electrolysis cell for the alkaline electrolysis of water. The electrode comprises a metal substrate. The metal substrate is coated, at least partially, with a catalyst layer. Thus, a catalyst layer is applied to at least one section of the metal substrate.

[0012] The catalyst layer has a first surface and an opposing second surface. The first surface is in contact with the metal substrate and thus forms a contact surface of the catalyst layer (also referred to as the interface with the metal substrate). The second surface faces away from the metal substrate; that is, the second surface is not in contact with the metal substrate. Therefore, the second surface forms a surface of the catalyst layer.

[0013] The catalyst layer contains a Raney nickel material. In particular, the Raney nickel material is a Raney nickel alloy, and more specifically, a leached Raney nickel alloy, i.e., a Raney nickel alloy from which the aluminum-rich phase has been at least partially leached out.

[0014] The catalyst layer also contains metal particles made of a metal alloy different from the Raney nickel material, specifically one containing nickel. At least a subset of these metal particles is arranged such that they form the contact surface with the metal substrate in sections. These metal particles are thus in contact with the metal substrate. In particular, these metal particles are bound to the metal substrate by mechanical (interlocking) and / or physical forces. The contact surface therefore forms, in particular, a bonding surface with the metal substrate.

[0015] The metal particles are embedded, at least partially, in a matrix of Raney nickel material. In this respect, the catalyst layer, in a boundary zone adjacent to the contact surface, exhibits a structure in which metal particles from a nickel-containing metal alloy different from Raney nickel material are incorporated into a matrix of Raney nickel material.

[0016] Such an electrode exhibits high catalytic activity while simultaneously being mechanically robust and durable. Within the scope of the invention, it was recognized that the metal particles can serve as anchor points to stabilize the catalyst layer, particularly the Raney nickel material, and especially to improve the adhesion of the catalyst layer to the metal substrate. Furthermore, the design of the anchor particles from a metal alloy provides good electrical conductivity, which has a positive effect on the internal resistance of the electrode and thus on the efficiency of alkaline water electrolysis.

[0017] In this context, the term "particle" encompasses various particle shapes. The particles can be regularly or irregularly shaped.

[0018] Preferably, the surface area of ​​the metal particles in relation to the total contact area with the metal substrate is at least 5%, preferably at least 10%, more preferably at least 20%, and preferably not more than 90%. Such a surface area has proven particularly advantageous with regard to stable anchoring of the catalyst layer to the metal substrate while simultaneously ensuring good electrical contact between the catalyst layer and the metal substrate.

[0019] The area fraction of the metal particles on the contact surface can be determined, for example, by taking a cross-sectional image (micrograph) of preferably at least 5 sections of the electrode using an optical microscope or an electron microscope (e.g. at 200x magnification) in such a way that a boundary line between the catalyst layer and the metal substrate runs within the micrograph.

[0020] - then a proportion of contact lines in which the metal particles form the boundary line is determined at the boundary line or at a specified section of the boundary line.

[0021] The proportion of contact lines can be determined in particular by measuring the length of the contact lines and summing the individual contact lines.

[0022] Furthermore, it can be advantageous if the concentration of metal particles in a marginal zone of the catalyst layer adjacent to the contact surface is higher compared to a central region of the catalyst layer. Such a marginal zone can be easily detected by electron microscopic analysis of a metallographic section.

[0023] The metal substrate is in particular a nickel-based substrate (i.e. made of nickel or nickel alloy or nickel-plated metal).

[0024] The metal substrate can have various shapes. Advantageously, the metal substrate is a flat metallic material. Preferably, the metal substrate has a plurality of openings. For example, the metal substrate can be in the form of a wire mesh or perforated sheet with a plurality of openings. Further advantageous embodiments of the substrate include: expanded metal mesh, wire woven fabric, metal fleece, and metal foam.

[0025] The metal substrate can be regularly or irregularly shaped. The metal substrate can be curved. Preferably, however, the metal substrate is flat.

[0026] The metal substrate preferably has two opposite sides. The metal substrate can be coated with the catalyst layer on one or both sides.

[0027] The metal alloy from which the metal particles are produced is in particular a non-leached metal alloy, i.e. a metal alloy which, in the course of an etching treatment with alkali, in particular with potassium hydroxide, does not undergo any significant structural change, or at least a reduced structural change compared to the Raney nickel material, in particular reduced leaching of aluminum.

[0028] Preferably, the metal alloy contains nickel. Such an alloy has proven particularly advantageous with regard to its good compatibility with the Raney nickel material on the one hand, and with the metal substrate, especially one also containing nickel, on the other.

[0029] Preferably, the metal alloy from which the metal particles are manufactured is selected from the group consisting of

[0030] - Nickel-aluminium alloy, in particular nickel-aluminium alloy consisting of 5-20 wt.% aluminum, balance nickel and unavoidable impurities;

[0031] - Nickel-chromium alloy, in particular NiCr20, i.e., nickel-chromium alloy consisting of 18-22 wt.%, preferably 19-21 wt.%, chromium, the remainder nickel and unavoidable impurities; and

[0032] - Stainless steel, in particular rust- and acid-resistant steel, further in particular stainless steel with a material number (steel key) of 1.40xx to 1.45xx.

[0033] According to a first aspect, the catalyst layer can comprise a Raney nickel material and metal particles made of a nickel-aluminum alloy different from the Raney nickel material. Nickel-aluminum alloys consisting of 5-20 wt.%, in particular 5-15 wt.%, and further, in particular 5-10 wt.%, aluminum, the remainder nickel, and unavoidable impurities have proven to be particularly advantageous.

[0034] According to a second aspect, the catalyst layer can comprise a Raney nickel material and metal particles made of a nickel-chromium alloy different from the Raney nickel material. A NiCr20 alloy has proven particularly advantageous, i.e., a nickel-chromium alloy consisting of 18–22 wt.%, preferably 19–21 wt.%, chromium, the remainder being nickel, and unavoidable impurities. According to a third aspect, the catalyst layer can comprise a Raney nickel material and metal particles made of stainless steel.

[0035] The metal particles preferably have a minimum diameter, particularly in the thickness direction of the catalyst layer, of greater than 5 pm, and more particularly greater than 10 pm.

[0036] In a further advantageous embodiment, the catalyst layer can also include metal particles from the metal alloy in a surface zone adjacent to the surface (second surface), particularly at the surface itself. These metal particles are, in particular, at least partially embedded in a matrix of the Raney nickel material. Thus, the surface zone can have a structure in which metal particles from the metal alloy, different from the Raney nickel material, are embedded in a matrix of the Raney nickel material. The metal particles can, in particular, also be present without a direct connection to the metal substrate. In this case, the metal particles can serve as reinforcement, which has a positive effect on the stability of the catalyst layer, especially in thicker layers.

[0037] Preferably, the catalyst layer is a thermally sprayed layer, i.e., applied to the metal substrate by thermal spraying. Therefore, the Raney nickel material and the metal particles can also be thermally sprayed materials.

[0038] Preferably, the thickness of the catalyst layer is at least 5 pm, in particular at least 20 pm, further in particular 40 pm and a maximum of 200 pm, in particular a maximum of 150 pm.

[0039] The Raney nickel material comprises, in particular, a Raney nickel alloy. Preferably, the Raney nickel material comprises an leached Raney nickel alloy, i.e., a Raney nickel alloy from which aluminum has been leached by an etching treatment with alkali, in particular using potassium hydroxide. The Raney nickel alloy is, in particular, a nickel-aluminum alloy having an (leached) aluminum-rich phase and a (non-leached) aluminum-poor phase. In particular, the Raney nickel material can be an, in particular, leached aluminum-nickel alloy.

[0040] Molybdenum alloy or consist of it. A particularly advantageous aluminum-

[0041] Nickel-molybdenum alloy consists of:

[0042] 35-40 wt% nickel

[0043] 15-20 wt.% molybdenum, optionally up to 2 wt.% titanium

[0044] Residual aluminium, in particular 40 - 50 wt.%, and unavoidable impurities in a total of no more than 1 wt.%.

[0045] Furthermore, it proves advantageous for catalytic activity if the Raney nickel material has a porous structure, in particular a sub-microporous structure (i.e., a structure with pores in the sub-micrometer range). The porous structure can be obtained, in particular, by leaching a Raney nickel alloy, i.e., by treating the Raney nickel alloy with an etching liquid, especially potassium hydroxide. Additionally or alternatively, the porous structure can also be obtained by dissolving non-metallic particles.

[0046] The invention also relates to an electrolysis cell. The electrolysis cell is specifically designed for alkaline water electrolysis. The electrolysis cell comprises two electrodes with a separator arranged between them. In this respect, the electrolysis cell includes a first electrode (cathode), a second electrode (anode), and a separator arranged between the first and second electrodes. One or both of the electrodes are configured as described above. The electrolysis cell preferably also includes a bipolar plate for each electrode, with the respective electrode arranged between the bipolar plate and the separator.

[0047] The invention also relates to the use of a metal substrate described above, on which at least a catalyst layer described above is applied, as an electrode in the alkaline electrolysis of water, in particular as an electrode in an electrolysis cell for alkaline water electrolysis. The problem described above is also solved by a method for producing an electrode with the features of claim 11. The method is specifically designed for producing an electrode described above.

[0048] According to the method, a metal substrate, in particular nickel-based, is first provided. The metal substrate is preferably in the form of a flat material, and more specifically in the form of a perforated sheet, expanded metal mesh, wire fabric or knitted fabric, metal fleece, or metal foam.

[0049] In a further step, at least one coating material is provided. The coating material is primarily in the form of a powder mixture. The coating material comprises at least two components:

[0050] - a first powder made from a (leached) Raney nickel alloy and

[0051] - a second powder made from a metal alloy different from the Raney nickel alloy, in particular containing nickel.

[0052] In a further step, the at least one coating material, in particular the powder mixture of the first and the second powder, is applied to at least one section of the metal substrate. In this respect, the process comprises coating at least one section of the metal substrate with the at least one coating material.

[0053] Optionally, before coating the metal substrate with at least one coating material, at least the section of the metal substrate to be coated can be mechanically blasted, e.g. sandblasted.

[0054] The coating of the metal substrate with the at least one coating material is preferably carried out such that the resulting coating has a structure in which particles from the second powder are arranged at a contact surface between the coating and the metal substrate, and these particles are particularly embedded in a matrix of the Raney nickel alloy. In this respect, the coating of the metal substrate with the coating material is particularly carried out such that particles from the second powder are embedded in a matrix of the Raney nickel alloy and form a contact surface between the coating and the metal substrate in certain sections.

[0055] The particles from the second powder may consist of individual powder grains, which may have been deformed during the coating process. Alternatively, the particles may be agglomerates of several grains of the second powder.

[0056] As mentioned above, the metal alloy from which the second powder is produced is preferably selected from the group consisting of

[0057] - Nickel-aluminium alloy, in particular nickel-aluminium alloy consisting of 5-20 wt.% aluminum, balance nickel and unavoidable impurities;

[0058] - Nickel-chromium alloy, in particular NiCr20, i.e., nickel-chromium alloy consisting of 18-22 wt.%, preferably 19-21 wt.%, chromium, the remainder nickel and unavoidable impurities; and

[0059] - Stainless steel, in particular rust- and acid-resistant steel, further in particular stainless steel with a material number (steel key) of 1.40xx to 1.45xx.

[0060] Preferably, the Raney nickel alloy from which the first powder is produced is an aluminum-nickel-molybdenum alloy or consists thereof. A particularly advantageous aluminum-nickel-molybdenum alloy consists of:

[0061] - 35 - 40 wt.% nickel

[0062] - 15 - 20 wt% molybdenum

[0063] - possibly up to 2 wt.% titanium

[0064] - Residual aluminium, in particular 40 - 50 wt.%, and unavoidable impurities in a total of no more than 1 wt.%.

[0065] The coating material can be applied in various ways. Preferably, the coating material is applied by thermal spraying. The application of the catalyst layer can be achieved using different thermal spraying methods.

[0066] Coating is preferably carried out by plasma spraying, in particular atmospheric plasma spraying (APS) or vacuum plasma spraying. Cold gas spraying, flame spraying, or high-velocity oxygen fuel (HVOF) spraying are also conceivable. It is also conceivable that the

[0067] Coating is carried out using arc wire spraying.

[0068] Furthermore, it proves advantageous if the proportion of the second powder in the coating material, i.e. based on a total weight of the coating material, is 5 to 40 wt.%, preferably 10 to 30 wt.%, and more preferably 15 to 25 wt.%.

[0069] Furthermore, it proves advantageous if the second powder has a mean particle diameter d50 of 10–100 pm, preferably 15–50 pm, and more preferably 20–45 pm. Particles of this size have proven particularly advantageous with regard to an anchoring effect. At the same time, such particles can be readily incorporated into the Raney nickel matrix.

[0070] The first powder preferably has a particle size / mean particle diameter d50 of 10-100 pm.

[0071] The particle diameter can be determined according to ISO 13320:2020-01. In particular, the particle diameter can be determined by laser light scattering using a "Laser Scattering Particle Size Distribution Analyzer", e.g., the "Partica LA-960V2" from Horiba Scientific.

[0072] Within the scope of the invention, it was also recognized that it is advantageous if a particle size of the second powder is adapted to a geometry of the metal substrate to be coated.

[0073] In a particularly advantageous embodiment, the metal substrate can be configured as a wire mesh (i.e., a fabric of wires). In this case, it can be advantageous if the ratio of the minimum wire diameter to the mean particle diameter d50 of the second powder is greater than four. Such a ratio has proven particularly beneficial for effective coating and good adhesion of the catalyst layer.

[0074] In a further advantageous development of the process, the application of the coating material can involve the sequential application of several material layers on top of each other. In this respect, several material layers can be applied radially to one another. The material layers then together form the coating (catalyst layer). Applying comparatively thin material layers as multilayers reduces heat input to the metal substrate and also makes it possible to optimize the individual material layers with regard to their composition, in particular the proportion of metal particles.

[0075] For example, it is conceivable that all material layers are made of the same coating material. It is also conceivable that at least a subset of the material layers are made of a different coating material or a coating material with a different composition. Therefore, at least a subset of the material layers can consist of a different material or a material with a different composition.

[0076] In particular, it is conceivable that the volume ratio of the first and second powder between the material layers is changed.

[0077] In an advantageous implementation of the process, the application of a material layer closest to the metal substrate (base layer) can be carried out using a first coating material, and the application of at least one further material layer can be carried out using a second coating material that differs from the first coating material. In particular, the first coating material can contain a larger proportion of the second powder by weight than the second coating material. Therefore, the proportion of the second powder by weight in the first coating material can be greater than the proportion of the second powder by weight in the second coating material.

[0078] As mentioned above, for the catalytic activity of the catalyst layer, it can be advantageous if the Raney nickel alloy is leached after coating, i.e., if aluminum is at least partially removed. Therefore, the process can include leaching the Raney nickel alloy after the coating material has been applied to the metal substrate. In particular, the process can include at least the partial removal of aluminum from the Raney nickel alloy, especially by etching using potassium hydroxide. In a further advantageous embodiment, the coating material can, in addition to the first and second powders, contain non-metallic particles as a third component.

[0079] In this context, the term "non-metallic" means that the particles do not consist of a pure metal or a metal alloy. Therefore, the term "non-metallic" excludes particles made of a pure metal or a metal alloy, such as metal powder or powder made of a metal alloy. However, the term "non-metallic" should not be understood to mean that the particles must not contain any metal atoms. As explained in more detail below, "non-metallic" particles within the meaning of this application can also include particles made of metal-non-metal compounds, such as glass particles.

[0080] The non-metallic particles can remain in the catalyst layer during use of the electrode in an electrolysis cell. Therefore, the catalyst layer can contain non-metallic particles in addition to the metal particles.

[0081] Alternatively, it may be advantageous to remove at least some of the non-metallic particles before using the electrode in an electrolysis cell – thereby creating pores in the catalyst layer. In this respect, the proposed method can include at least the partial removal of the non-metallic particles after coating with the coating material.

[0082] The at least partial removal of non-metallic particles can be achieved in various ways, depending particularly on the type of non-metallic particles used. For example, at least partial removal of non-metallic particles can involve heating, especially thermal decomposition, of at least a subset of the non-metallic particles. Heating the non-metallic particles can be accomplished by heating the coated substrate, e.g., in an oven, and / or by locally applying heat, e.g., using a laser. Alternatively or additionally, at least partial removal of the non-metallic particles can involve dissolving at least a subset of the non-metallic particles using a dissolving fluid. This dissolving process can include dissolving the non-metallic particles in the dissolving fluid.The dissolution process can also include the chemical decomposition of the non-metallic particles by the dissolution fluid. The dissolution fluid can be, for example, a chemical solvent, an acid, an alkali, water, or a chemical reagent.

[0083] The non-metallic particles can be made from various materials. Suitable non-metallic particles include:

[0084] - Silicon-containing particles, in particular glass particles, further in particular glass powder or glass spheres;

[0085] - Particles of precipitated silica;

[0086] - Plastic particles, in particular made of a polymer from the group comprising PBT, PET, PC and PEEK;

[0087] - Salt particles, especially of a carbonate, further especially of KHCO3 or K2CO3;

[0088] - Particles made of a carbon material, in particular graphite and / or carbon black, wherein the removal of the non-metallic particles comprises heating the coated substrate in an oxygen-containing atmosphere, in particular at a temperature between 300 and 450°C;

[0089] - Particles of a mineral, in particular sodium tetraborate or potassium tetraborate; and combinations thereof.

[0090] It is advantageous if the particle diameter of the non-metallic particles is less than 150 pm, preferably 5–50 pm, more preferably 5–40 pm, and more preferably 10–30 pm. The coating material can also comprise a mixture of non-metallic particles with different particle diameters. The particle diameter can be determined according to ISO 13320:2020-01. In particular, the particle diameter can be determined by laser light scattering using a Laser Scattering Particle Size Distribution Analyzer, such as the Partica LA-960V2 from Horiba Scientific.

[0091] The advantages and optional features described above in connection with the electrode can also serve to further develop the process, so reference is made to the above disclosure to avoid repetition.

[0092] The invention is explained in more detail below with reference to the figures. Figure 1 shows a simplified schematic representation of an exemplary embodiment of an electrode in top view;

[0093] Figure 2 shows a section of the electrode according to Figure 1 in a sectional view along the

[0094] Figure 1 shows the section plane ll-ll;

[0095] Figure 3 shows a further embodiment of an electrode corresponding to Figure 2.

[0096] Sectional view;

[0097] Figure 4 shows a diagram illustrating the adhesion strength of catalyst layers with different proportions of metal particles; and

[0098] Figure 5 shows a simplified schematic representation of an exemplary embodiment of an electrolysis cell comprising two electrodes according to Figure 1.

[0099] In the following description and in the figures, the same reference symbols are used for identical or corresponding features. The figures are merely schematic and, in particular, not to scale.

[0100] Figure 1 shows a simplified schematic representation of an exemplary design of an electrode, which is generally designated by the reference numeral 10.

[0101] The electrode 10 has a metal substrate 12. In this example, the metal substrate is formed as a wire mesh 14 made of interwoven metal wires 16.

[0102] The metal wires 16 can have a round cross-sectional shape. The metal wires 16, or at least a subset of the metal wires 16, can also have an anisotropic cross-sectional shape. For example, at least a subset of the metal wires 16 can be formed as flat-rolled wires.

[0103] The metal wires 16 can be identical to one another. However, it is also conceivable that the wire mesh 14 is made up of two or more types of metal wires 16.

[0104] In embodiments not shown, the metal substrate 12 can also have other forms, e.g., be designed as a perforated sheet. The metal substrate 12 / wire mesh 14 is coated on one side with a catalyst layer 18 (see Fig. 2). In embodiments not shown, both sides of the metal substrate 12 can also be coated with a catalyst layer 18.

[0105] The catalyst layer 18 has a contact surface 20 with which it contacts the metal substrate 12, and an opposing surface 22, which is free in this example. The contact surface 20, in particular, forms a connection between the catalyst layer 18 and the metal substrate 12.

[0106] The catalyst layer 18 is specifically designed to catalyze the electrolysis of water.

[0107] In this example, the catalyst layer 18 has two components: a Raney nickel material 24 and metal particles 26 made of a metal alloy different from the Raney nickel material 24.

[0108] As can be seen from Fig. 2, at least a subset of the metal particles 26 are arranged at the contact surface 20. In particular, the metal particles 26 arranged at the contact surface 20 are in direct contact with the metal substrate 12. The metal particles 26 are arranged in a matrix of the Raney nickel material 24.

[0109] It is conceivable that the metal particles 26 are arranged exclusively in a marginal zone 28 of the catalyst layer 18 adjacent to the contact surface 20 (see Fig. 2).

[0110] It is also conceivable that, in addition to the metal particles 26 at the contact surface 20, metal particles 26 are also arranged in a surface zone 30 adjacent to the surface 22, in particular on the surface 22 of the catalyst layer 18 itself (see Fig. 3).

[0111] In the example shown in Fig. 3, the metal particles 26 protrude above the Raney nickel matrix 24. In embodiments not shown, the metal particles 26 can also be completely embedded in a matrix of the Raney nickel material 24.

[0112] As mentioned above, such electrodes 10 can be produced in particular by applying a powder mixture of a first powder of a Raney nickel alloy and a second powder of a metal alloy different from the Raney nickel alloy to the metal substrate 12, in particular by thermal spraying.

[0113] Examples:

[0114] As mentioned above, the addition of metal particles 26 can improve the adhesion strength of the catalyst layer 18, i.e., the bonding of the catalyst layer 18 to the metal substrate 12, compared to catalyst layers 18 without metal particles 26.

[0115] This is shown in Figure 4, which visualizes the adhesion strength of catalyst layers 18 as a function of the proportion of metal particles 26 on the catalyst layer 18.

[0116] For this purpose, powder mixtures were first produced from powder made of AI44Ni37Mol9 (as Raney nickel alloy) with a mean particle diameter d50 of 30 pm and NiAIS (as metal particles) with a mean particle diameter d50 of 40 pm according to the following table.

[0117] The powder mixtures produced in this way were then applied to a nickel substrate by atmospheric plasma spraying. The thickness of the resulting catalyst layers was approximately 60 pm.

[0118] Subsequently, the adhesion strength of the catalyst layer 18 was measured for each sample using a pressure water jet test. For this purpose, the samples were mounted in a test chamber and subjected to a pressure water jet according to the following parameters:

[0119] - Distance between water jet nozzle and sample: 50 mm

[0120] - Impact angle of water jet on sample: 90° - Spray pressure: 38 bar

[0121] - Nozzle type: Fan nozzle

[0122] - Water temperature (fully demineralized water): 40°C

[0123] - Test duration: 30 s

[0124] Subsequently, the width of the area of ​​the samples damaged by the water jet (removal width) was measured.

[0125] The removal widths of the example samples were then normalized to the removal width of the reference sample (relative adhesion strength) and applied to the mass fraction of the metal particles in the coating material (see Fig. 4).

[0126] As can be seen from Figure 4, the adhesion strength of the catalyst layer 18 could be significantly improved by adding metal particles 26.

[0127] Figure 5 shows a simplified schematic representation of an embodiment of an electrolysis cell 100 for alkaline water electrolysis.

[0128] The electrolysis cell 100 comprises (in Figure 5 from left to right) a first optional bipolar plate 102-1, a first electrode 10-1 (cathode), a separator 104, a second electrode 10-2 (anode) and a second optional bipolar plate 102-2.

[0129] The electrodes 10-1, 10-2 are each, or at least the first electrode 10-1, designed as described above.

[0130] During operation, an electrolyte, in particular an aqueous KOH solution for alkaline water electrolysis, surrounds the electrodes 10-1, 10-2. As mentioned above, when a DC voltage is applied to the electrodes 10-1, 10-2, hydrogen is produced at the cathode (e.g., electrode 10-1) and oxygen at the anode (e.g., electrode 10-2) as a result of the electrochemical decomposition of water. The product gases (hydrogen and oxygen) are carried away through the openings 32 of the electrodes 10-1, 10-2 and discharged upwards between the bipolar plate 102-1, 102-2 and the electrodes 10-1, 10-2.

Claims

Patent claims 1. Electrode (10) for use in alkaline water electrolysis, comprising a metal substrate (12) on which at least sectionally a catalyst layer (18) is applied, wherein the catalyst layer (18) has a contact surface (20) in contact with the metal substrate (12) and an opposing surface (22), wherein the catalyst layer (18) comprises a Raney nickel material (24), characterized in that the catalyst layer (18) also comprises metal particles (26) made of a metal alloy different from the Raney nickel material (24), in particular containing nickel, wherein at least a subset of these metal particles (26) are arranged such that they sectionally form the contact surface (20).

2. Electrode (10) according to claim 1, wherein the metal particles (26) are embedded in a matrix of the Raney nickel material (24).

3. Electrode (10) according to claim 1 or 2, wherein the metal alloy is selected from the group consisting of - Nickel-aluminium alloy, in particular nickel-aluminium alloy consisting of 5-20 wt.% aluminum, balance nickel and unavoidable impurities; - Nickel-chromium alloy, in particular NiCr20, i.e., nickel-chromium alloy consisting of 18-22 wt.%, preferably 19-21 wt.%, chromium, the remainder nickel and unavoidable impurities; and - Stainless steel, in particular rust- and acid-resistant steel, furthermore in particular stainless steel with a material number of 1.40xx to 1.45xx.

4. Electrode (10) according to one of the preceding claims, wherein the area fraction of the metal particles (26) on the total contact area (20) is at least 5%, preferably at least 10%, further preferably at least 20%.

5. Electrode (10) according to one of the preceding claims, wherein the catalyst layer (18) is furthermore located in a surface zone (30) adjacent to the surface (22) comprising metal particles (22) made of the nickel-containing metal alloy, in particular wherein the metal particles (26) form section by section the surface (22).

6. Electrode (10) according to one of the preceding claims, wherein the catalyst layer (18) is thermally sprayed.

7. Electrode (10) according to one of the preceding claims, wherein the Raney nickel material (24) has a porous structure, in particular with pores in the sub-micrometer range.

8. Electrode (10) according to any of the preceding claims, wherein the Raney nickel material (24) comprises or consists of an aluminium nickel molybdenum alloy, in particular an aluminium nickel molybdenum alloy consisting of: - 35 - 40 wt.% nickel - 15 - 20 wt.% molybdenum - possibly up to 2 wt.% titanium - Residual aluminium, in particular 40 - 50 wt.%, and unavoidable impurities in a total of no more than 1 wt.%.

9. Use of an electrode (10) according to one of the preceding claims for oxygen generation in a half-cell of an electrolysis cell (100) for alkaline electrolysis of water.

10. Electrolysis cell (100), in particular for alkaline water electrolysis, comprising a first electrode (10-1), a second electrode (10-2) and a separator (102) arranged between the first and the second electrode (10-1, 10-2), wherein the first electrode (10-1) and / or the second electrode (10-2) is configured according to any one of claims 1 to 9.

11. Method for manufacturing an electrode (10) for use in alkaline water electrolysis, the method comprising: - Providing a metal substrate, in particular a nickel-based one (12); - Providing at least one coating material, comprising, in particular in the form of a powder mixture, o a first powder of a Raney nickel alloy and o a second powder made from a metal alloy different from the Raney nickel alloy, in particular containing nickel; - Coating at least one section of the metal substrate (12) with the at least one coating material such that a resulting coating has a structure in which particles (26) from the second powder are incorporated in a matrix of the Raney nickel alloy and section by section form a contact surface (20) of the coating with the metal substrate (12).

12. Method according to the preceding claim, wherein the coating material is applied by thermal spraying.

13. Method according to claim 11 or 12, wherein the proportion of the second powder in the coating material is 5 to 40 wt.%, preferably 10 to 30 wt.%, more preferably 15 to 25 wt.%.

14. Method according to any one of claims 11 to 13, wherein the second powder has a mean particle diameter d50 of 10-100 pm, preferably 15-50 pm, more preferably 20-45 pm.

15. Method according to any one of claims 11 to 14, wherein the metal substrate (12) is formed as a wire mesh (14), wherein the ratio of minimum wire diameter to mean particle diameter of the second powder from the metal alloy is greater than four.

16. Method according to any one of claims 11 to 15, wherein the application of the coating material comprises the sequential application of several layers of material on top of each other.

17. Method according to the previous claim, wherein the application of a material layer closest to the metal substrate (12) and encompassing the contact surface (20) is carried out with a first coating material, and wherein the application of at least one further material layer is carried out with a second coating material, wherein the first coating material has a larger weight fraction of second powder than the second coating material.

18. A method according to any one of claims 11 to 17, further comprising, after coating: leaching the Raney nickel alloy, in particular treating the Raney nickel alloy with an etching liquid, in particular lye, and further in particular potassium hydroxide.

19. A method according to any one of claims 11 to 18, wherein the coating material further comprises non-metallic particles, in particular having a particle diameter of less than 150 pm.

20. Method according to the preceding claim, further comprising, after coating: at least partial removal of the non-metallic particles.

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