Electrode body, arc wire spraying device and method for manufacturing an electrode body

Abstract

The electrode body K according to the invention has an active layer 32 made of a nickel-molybdenum alloy, which is permeated by a dense, continuous capillary network open at the top O. Immediately after the manufacture of the electrode body K, the capillary network is still filled with an alkali-sensitive metal, e.g., zinc, aluminum, magnesium, or the like, which is dissolved from the capillary network in a formation step, e.g., during the initial commissioning of the electrode body as an electrode in an electrolyzer. The associated arc wire spraying device 10 according to the invention comprises a two-wire burner in which an arc 16 is maintained between two wires 17, 18. The wires 17, 18 consist of different metals with different physical and chemical properties. They are continuously fed to the arc 16.The wire 17 is made of an alloy containing at least nickel and molybdenum as its main components. The other wire serves to create interconnected inclusions of alkali-sensitive metal within the nickel-molybdenum layer. The invention enables the coating of the substrate 30 with the most precise possible dosage of the nickel and molybdenum components on the one hand and the filler metal on the other. By using an arc wire spraying process, large areas can be coated in a relatively short coating process.

Description

[0001] The invention relates to an arc wire spraying device for coating an electrode body (preferably metallic), such as a metal plate, a metal sheet, or a metal grid. The electrode body can be used, for example, as a cathode in an electrolyzer for the production of hydrogen or as an anode. The invention also relates to a coated electrode body and an arc wire spraying process for manufacturing an electrode body.

[0002] In the field of alkaline electrolysis (AEL), it is common practice to coat the electrode bodies to increase the efficiency of the electrolyzer, for example by increasing the surface area of ​​the electrode body in contact with the electrolyte.

[0003] In "Improving plasma sprayed Raney-type nickel-molybdenum electrodes towards high-performance hydrogen evolution in alkaline medium" by Fatemeh Razmjooei, Taikai Liu, Daniela Aguiar Azevedo, Efi Hadjixenophontos, Regine Reissner, Günter Schiller, Syed Asif Ansar, and Kaspar Andreas Friedrich, Scientific Reports 10 10948, DOI: 10.1038 / s41598-020-67954-y, a sheet coated with a nickel-aluminum-molybdenum alloy is described, intended to serve as a cathode for an alkaline electrolyzer. The coating disclosed therein has a composition of 44 wt% nickel, 39 wt% aluminum, and 17 wt% molybdenum. In alkaline electrolyzers, a potassium hydroxide solution, also known as caustic soda, serves as the electrolyte. A potassium hydroxide solution is typically used, with a concentration in the range of 20 to 40%. Potassium hydroxide is particularly reactive towards aluminum, causing rapid and severe corrosion.Nickel, on the other hand, is highly resistant to alkaline solutions and can serve as a kind of shield against the highly corrosive electrolyte in the coating. The addition of molybdenum increases the intrinsic activity, thereby improving the efficiency of hydrogen production in alkaline electrolysis. Other alloying elements that can increase intrinsic activity include tungsten, iron, cobalt, titanium, niobium, tantalum, chromium, gold, iridium, rhenium, rhodium, and platinum. During the initial operation of the alkaline electrolyzer with electrode bodies coated in this way, the aluminum components in the coating are leached by the electrolyte, resulting in a porous structure with a relatively large surface area, which further enhances the coating's catalytic properties.

[0004] This nickel-aluminum-molybdenum coating is applied in the prior art exclusively by atmospheric plasma spraying with powder or by vacuum plasma spraying with powder (see "Development of Highly Efficient Raney Nickel Electrodes for Alkaline Water Electrolysis" by Günter Schiller, Asif Ansar, Taikai Liu, and Regine Reißner at the European Hydrogen Energy Conference (EHEC 2018) in Malaga, Spain). However, both coating methods achieve only low deposition rates, making them unsuitable for large-area electrode bodies due to the relatively long coating time required in production. Furthermore, with these coating methods, the composition of the coating can only be adjusted by the amount of powder added, which can significantly complicate the precise control of the proportions of molybdenum, nickel, and aluminum in the resulting coating.

[0005] In "Wire-arc sprayed nickel based coating for hydrogen evolution reaction in alkaline solutions" by Joel Fournier, Danielle Miousse, and Jean-Gabriel Legoux, published in the International Journal of Hydrogen Energy, Volume 24, Issue 6, 1999, Pages 519-528, ISSN 0360-3199, a coating process is described in which a nickel-aluminum layer is applied to an electrode body using an arc wire spraying process. In this process, an electric arc is generated between two wires. The tips of the wires are melted by the arc while the wires are continuously advanced. The molten wire material is accelerated by a gas stream toward the electrode body and thus deposited onto it. Nickel-aluminum and / or aluminum wires, for example, are used as the wires.

[0006] In “Kinetics of hydrogen evolution reaction on skeleton nickel and nickel-titanium electrodes obtained by thermal arc spraying technique” by Andrea Kellenberger, Nicolae Vaszilcsin, Waltraut Brandl and Narcis Duteanu, October 2007, International Journal of Hydrogen Energy 32(15):3258-3265, DOI:10.1016 / j.ijhydene.2007.02.028, an arc wire spraying process with two consumable wires is also described, in which one wire is made of nickel-titanium and the other wire of aluminum.

[0007] Based on this, the invention aims to create a highly effective electrode body that enables alkaline electrolysis in hydrogen production to be carried out with increased efficiency. Furthermore, the invention aims to provide an arc wire spraying device and a corresponding method suitable for manufacturing such electrode bodies. The method should enable the production of a coating with a highly active and highly porous structure.

[0008] This problem is solved with the electrode body according to claim 1, the arc wire spraying device for coating a carrier body of an electrode body according to claim 6, the arc wire spraying method according to claim 12 and the electrolyzer according to claim 15:

[0009] The electrode body according to the invention comprises a support body on which an active layer is arranged. The support body is, in particular, a metallic component, such as a sheet, a plate, or a metal grid or sieve. The electrode body is preferably suitable for use in an (alkaline) electrolyzer. Immediately after its production, the active layer of the electrode body is a layer in which zones of a filler metal, e.g., aluminum, magnesium, zinc, or another alkali-sensitive metal, and zones of a nickel-molybdenum alloy are present. These zones interpenetrate one another, with few to no isolated areas enclosed by the other metal. Thus, each zone forms a largely continuous body, with the two bodies preferably being interlocked without voids.The zones of the unused electrode body can have a volume ratio between 1:1 and 3:1, particularly advantageously 2:1.

[0010] The electrode body is not yet ready for use in this form. It is made ready for use through a forming process. For this, the electrode body is brought into contact with an alkaline solution and, if necessary, connected to the positive terminal of a DC voltage source, which dissolves the filler metal. The electrode body can now be used as an electrode, in particular as the cathode of an electrolyzer. Formation can be carried out, for example, during the (initial) operation of the alkaline electrolyzer by the alkaline electrolyte or in a leaching step before commissioning the alkaline electrolyzer. Potassium hydroxide solution, for example, can be used to leach out the filler metal. The nickel-molybdenum structure remaining after leaching is both highly porous and sponge-like. The structure is particularly open-pored, meaning that at least a large proportion of the individual pores are interconnected.

[0011] In its formed state, the active layer is a highly porous, open-pore nickel-molybdenum layer with interconnected microchannels. Preferably, the microchannels have an inner surface with high roughness and thus high catalytic activity. The pores form channels that extend from the nickel surface to the top of the active layer. After removal of the aluminum body by leaching, the active layer is formed by an open-pore, interconnected nickel-molybdenum body whose pore volume to the volume of the nickel-molybdenum body is in a ratio of 1:1 to 3:1, particularly advantageously 2:1. The active layer consists predominantly of nickel with a proportion of 1 wt.% to 32 wt.% molybdenum and optionally minor components.

[0012] In the electrode body according to the invention, the active layer preferably has a volume ratio between filler metal, in particular aluminum, and nickel-molybdenum alloy of at least substantially 2:1. The active layer forms a highly porous and highly active structure. The resulting layer can, for example, contain 40 to 60 wt.% nickel, 10 to 25 wt.% molybdenum (nickel and molybdenum alloy), and 20 to 45 wt.% aluminum (or other filler metal). The resulting layer can also be flat and exhibit low surface waviness, for example, waviness corresponding to a value of 0.5 times the material thickness of the resulting layer. Waviness describes the spacing between periodically recurring components in the surface texture.Minimal coating waviness is particularly advantageous when the electrode body is used as the cathode (or anode) in an alkaline electrolyzer. This allows the plate-shaped electrode body to lie as flush as possible against an (ion-conducting) diaphragm, preventing the accumulation of hydrogen bubbles that could reduce the electrolyzer's efficiency. Additionally, the overall length of the alkaline electrolyzer is reduced, and the capacitance is increased by decreasing the electrode plate spacing, further improving efficiency.

[0013] According to the invention, the active layer is arranged on a non-porous, alkali-impermeable nickel surface formed on the carrier body. The carrier body can be made of a material whose main component is not nickel, with the nickel surface being formed on a base layer applied to the carrier body. This base layer can consist of nickel, a nickel alloy, or a nickel-aluminum alloy. Alternatively, the carrier body itself can be made of nickel, a nickel alloy, or a nickel-aluminum alloy.

[0014] If the base layer is formed from a nickel-aluminum alloy, the aluminum content is preferably less than 20 wt.%. The base layer ensures reliable adhesion of the active layer to the substrate and is suitable for shielding the substrate from direct contact with the electrolyte. The base layer can also be applied using an arc wire spraying process, particularly before the application of the active layer made of nickel-molybdenum and an alkali-sensitive material (e.g., aluminum, magnesium, zinc, etc.). For example, an arc wire spraying process can be used in which two wire electrodes, each made of a nickel alloy, or two wire electrodes, each made of a nickel-aluminum alloy, are employed.

[0015] The arc wire spraying device according to the invention has at least two electrodes made of wire. They are connected to at least one power source to maintain an arc in an arc zone. The electrodes are each designed as a wire that can be melted by the arc. Each wire is associated with a feed unit configured to continuously supply the respective wire to the arc zone. One of the wires is made of an alloy containing at least nickel and molybdenum as its main constituents. The other wire consists of a metal soluble in an alkaline solution, for example, aluminum, magnesium, zinc, or alloys thereof, or the like. The two wires can have the same or different diameters. Preferably, the diameter of the aluminum wire is larger than the diameter of the nickel-molybdenum wire.

[0016] This enables the electrode body to be coated with the most precise possible dosage of nickel and molybdenum components in the resulting layer. By using the arc wire spraying process with the simultaneous feeding of two wires of different materials into an arc zone, particularly large areas can be coated in a relatively short coating process. Both in terms of control over the layer composition and in terms of the application volume per coating system, the coating device according to the invention, as well as the coating process, are superior to conventional systems and processes, especially powder coating systems and processes.

[0017] A special feature of the arc wire spraying device according to the invention is that it can produce a highly porous and simultaneously highly active coating on the substrate. The volume fraction of the nickel-molybdenum alloy in the resulting layer can be precisely controlled.

[0018] The arc wire spraying device according to the invention includes the consumable wires, which melt upon contact with the arc. The arc wire spraying device is designed to continuously feed the wires into the arc zone. The feeding preferably occurs without interruptions or with only very brief interruptions, for example, interruptions in the millisecond range.

[0019] Wires, insofar as they consist of alloys, have main constituents and minor constituents. The main constituents of an alloy are, in particular, those constituents that constitute the largest proportion by weight in the alloy. The main constituent is, in particular, the base metal from which the alloy is made.

[0020] While the first wire consists of an alkali-resistant, catalytically active metal, the second wire consists of a material that is not alkali-resistant. The main components of this material differ from those of the first electrode. The main component of the alloy of the second wire is preferably aluminum, magnesium, or zinc. By using two wires as electrodes, a structure of nickel-molybdenum and aluminum, magnesium, or zinc can be produced, wherein the aluminum or zinc component in the structure is not alloyed with the nickel-molybdenum component of the structure.

[0021] Each electrode, i.e., each wire, is assigned its own feed unit, designed to continuously supply the respective wire to the arc zone. The feed rates specified by the first and second feed units can be adjusted independently by setting their feed speeds independently. This allows the ratio of nickel-molybdenum alloy to aluminum, magnesium, or zinc in the coating to be precisely controlled via the feed rates of the two wires into the arc zone. The feed rate is defined as the amount of material supplied per unit of time, measured by volume or weight. The feed rate depends on the wire diameter and the feed speed.

[0022] The alloy of the first wire contains in particular a proportion of 1 to 32 wt.% molybdenum, preferably a proportion of 15 to 25 wt.% molybdenum, particularly preferably a proportion of 17 to 22 wt.% molybdenum, whereby the coating produced has particularly good catalytic activity.

[0023] Preferably, the alloy of the first wire contains at least one of the following minor components: iron, tungsten, copper, cobalt, silver, titanium, chromium, niobium, and tantalum. This further improves the catalytic activity of the resulting layer. Minor components of an alloy are defined as additions to the alloy that are not present in such a quantity that they are considered major components. In particular, the alloy of the first wire contains 0.05 to 12 wt.% iron, 0.05 to 10 wt.% tungsten, and / or 0.05 to 10 wt.% chromium. Preferably, the alloy contains one or more components with the following proportions: 3 to 8 wt.% iron, 0.5 to 7 wt.% tungsten, and / or 0.5 to 8 wt.% chromium.

[0024] The arc wire spraying device has, in particular, a nozzle configured to direct a gas stream flowing through the arc zone, accelerating the wire material melted in the arc zone in a spray cone towards the support body of the electrode body to be produced. The gas stream mixes and atomizes the molten wire material, i.e., the droplets of molten wire material are broken down, for example, by the shear forces occurring during flight. The gas stream can be a pure gas stream or a mixed gas stream, e.g., an air stream. The gas can be an inert gas, particularly a noble gas such as argon. Nitrogen or another inert gas prevents oxidation of the molten wire material before it impacts the surface of the support body.This allows a layer of melted wire material to form on the surface of the carrier body.

[0025] The nozzle is arranged such that the spray cone is ejected from the arc wire spraying device at a predetermined angle and strikes the carrier body. The angle between the spray cone and the surface of the carrier body can, for example, be between 70° and 110°, preferably between 80° and 100°, and particularly preferably at least substantially 90°.

[0026] In particular, the spray cone is oriented, at least substantially, horizontally or vertically to the nozzle. If the spray cone is oriented vertically to the nozzle, the acceleration forces of the gas flow and gravity act parallel to the droplets contained in the gas flow. If the spray cone is oriented, at least substantially, horizontally to the nozzle, gravity acts perpendicular to the direction of travel of the droplets, so that a certain proportion of the droplets in the gas flow can leave the spray cone. The distance between the arc zone and the surface of the support body is preferably in the range of 100 mm to 500 mm.

[0027] In particular, the gas stream at least partially, and preferably completely, envelops the wire material melted in the arc zone. The gas stream can thus form a protective sheath enveloping the droplet stream.

[0028] It is preferred that the first electrode is connected to the positive terminal of the power source and the second electrode to the negative terminal. In this configuration, the first electrode can act as the anode and the second as the cathode for the arc. The anode can be 200°C to 500°C hotter than the cathode. Depending on the required melting point of the wire, the polarity of the circuit can thus be adjusted. Alternatively, the first electrode can be connected to the negative terminal of the power source and the second electrode to the positive terminal.

[0029] In an alternative embodiment, the arc wire spraying device has a third electrode, here referred to as the cathode. The first and second electrodes are each connected to one terminal (e.g., the positive terminal) of separate power sources, and the third electrode is connected to the opposite terminal of each of the two separate power sources. Conversely, the first and second electrodes can each be connected to a negative terminal of a separate power source. Alternatively, the higher-melting-point wire can be connected to the positive terminal of its power source, and the lower-melting-point wire to the negative terminal of its power source. The third electrode is connected to the opposite terminal of each of the two power sources. The cathode is made of a durable material, e.g., tungsten, which is not meltable in the arc.

[0030] The object of the invention is further achieved by an arc wire spraying process for coating a carrier body of an electrode body, which comprises the following steps: - Maintaining an electric arc in an arc zone with at least two electrodes, wherein at least the electrodes are designed as meltable wires, one of which is made of an alloy containing at least nickel and molybdenum as its main constituents: and - continuous feeding of the wires into the arc zone.

[0031] All features and advantages described in relation to the arc wire spraying device according to the invention are also applicable to the method according to the invention.

[0032] Preferably, the introduction of the gas flow into the arc zone creates a droplet flow of the molten wire material, which reaches a current velocity of 60 m / s, preferably 70 m / s, particularly preferably 80 m / s or more.

[0033] Further details and advantageous embodiments or specifics of the invention will become apparent from the drawings, the description, and the claims. These show: Fig. 1 a schematic representation of an example of the arc wire spraying device according to the invention; Fig. 2 a schematic detail view of the electrode body with the generated coating; Fig. 3a to 3c show several examples of how the arc wire burner can be arranged relative to the electrode body; and Fig. Figures 4a to 4b show several examples of how the electrodes are connected to the power source.

[0034] Fig. Figure 1 shows a schematic view of an example of the arc wire spraying device 10 according to the invention. Fig. Figure 1 shows a type of arc wire spraying device 10, wherein the arc wire spraying device 10 can, however, stand for any type of arc wire spraying device in which the concept according to the invention can be realized with a wire as an electrode which melts in an arc zone and which is made of an alloy which mainly contains nickel and molybdenum.

[0035] The arc wire spraying device 10 is designed for coating a carrier body 30 to produce an electrode body K. The carrier body 30 can be formed, for example, by a sheet, a metal plate, or even a non-planar shaped body made of metal or another electrically conductive material.

[0036] The arc wire spraying device 10 comprises an arc wire torch 11 with two electrodes 12 and 13, which are connected to a power source 14. The power source 14 preferably has a falling current / voltage characteristic. It may also have a communication interface for exchanging information with other components.

[0037] Between the first electrode 12 and the second electrode 13, an arc 16 is maintained by the power source 14 in an arc zone 15. The first electrode 12 is formed by a first wire 17 and the second electrode 13 by a second wire 18. The first wire 17 and the second wire 18 are meltable in the arc 16 in the arc zone 15 and are guided laterally into the arc zone 15 in one plane.

[0038] The arc wire spraying device 10 also includes a feed unit 19, which is configured to continuously supply the two wires 17, 18 to the arc zone 15, where the wires 17 and 18 are melted by the arc 16. The feed unit 19 has a first feed unit 20 and a second feed unit 21, each assigned to one of the wires 17, 18. The first feed unit 20 is configured to supply the first wire 17 to the arc zone 15 at an adjustable feed rate, while the second feed unit 21 is configured to supply the second wire 18 to the arc zone 15 at an adjustable feed rate. The first wire 17 and the second wire 18 are each supplied from a reservoir (not shown), which may, for example, be formed by unwindable wire reels.

[0039] The first and second wires 17 and 18 are connected to the power source 14 via a first contact 22 and a second contact 23. The arc wire spraying device 10 also has a nozzle 24 which is configured to introduce a gas flow 25 into the arc zone 15.

[0040] In the Fig. In the example shown, the first wire 17 is made of an alloy containing nickel and molybdenum as its main components. The second wire 18, on the other hand, is made of an alloy whose main component is aluminum. The first wire 17 is preferably connected to the positive terminal of the power source 14 via contact 22, while the second wire 18 is connected to the other terminal of the power source 14 via contact 23. A reverse polarity to that shown in Fig. Polarity 1 shown is also possible.

[0041] The in Fig. The arc wire spraying device 10 shown in Figure 1 also has a control unit 26 which can be communicatively connected to the feed units 20, 21 and the power source 14. Additionally, the control unit 26 can also be communicatively connected to the nozzle 24 or to an element regulating the gas flow of the nozzle.

[0042] The power source 14 is controllable; for example, the control unit 26 can specify a desired current, voltage, or characteristic curve for the power source 14. The control unit 26 can also be configured to adjust the feed rates of the first feed unit 20 and the second feed unit 21 separately. The feed rates are determined by the conveying speeds of the two feed units 20 and 21.

[0043] The control unit 26 can, for example, adjust the feed rates of the two wires 17, 18 in a desired ratio, e.g., 1:2, thereby establishing a suitable current from the power source 14. The ratio of the two feed rates results from the desired ratio of nickel / molybdenum alloy and aluminum in the coating, in which an unalloyed mixture of nickel-molybdenum and aluminum is produced. The control unit 26 can increase or decrease the feed rates according to the detected current (preferably in a fixed ratio to each other) in order to achieve a desired current.

[0044] Furthermore, the control device 26 can be configured to specify a suitable voltage to the power source or to regulate the gas flow 25.

[0045] The control unit 26 can access data stored in a memory unit 27, such as models, to set the parameters (feed rates of the feed units and current, voltage, characteristic curve type, etc.). The models stored in the memory unit 27 can describe a relationship between the individual parameters and the expected composition of the produced coating. For example, predefined compositions of nickel-molybdenum to aluminum or zinc in the stored models can be assigned one or more sets of parameters with which the composition in the coating can be achieved.

[0046] The gas stream 25 introduced into the arc zone 15 mixes and accelerates the wire material 28, which is molten in the arc 16, in a spray cone 29 towards the support body 30. The molten wire material 28 is preferably completely enveloped by the gas stream 25. The gas in the gas stream is, for example, nitrogen, so that oxidation of the molten material 28 in the spray cone 29 can be at least largely avoided. The wire material 28, accelerated towards the support body 30, forms a layer 32 on the surface 40 of the support body 30.

[0047] The in Fig. The electrode body K shown in Figure 1 has a base layer 31 between the carrier body 30 and the layer 32, which is made of a nickel alloy or a nickel-aluminum alloy. The base layer 31 can be applied, for example, using an arc wire spraying device 10 of the type described above, in which case the first wire 17 and the second wire 18 can each be made of a nickel or nickel-aluminum alloy. A single-wire torch can also be used instead of this two-wire torch to produce the base layer 31.

[0048] Fig. Figure 2 shows a detailed view of the electrode body K with the support body, the base layer 31, and the layer 32 applied by the arc wire spraying device 10. The applied layer 32 has a nickel-molybdenum structure 33 (in Fig. 2 shown hatched) and another structure 34 made of aluminium (in Fig. (2 not shown hatched) which are mixed together such that the volume ratio of nickel-molybdenum alloy to aluminum is as close as possible to 1:2. The aluminum structure 34 extends continuously from the base layer 31 to the top surface O. Likewise, the structure 33 extends continuously from the base layer 31 to the top surface O. The aluminum structure 34 can be leached from layer 32 with a potassium hydroxide solution (with potassium hydroxide solution), so that after the aluminum has been leached, only the nickel-molybdenum structure 33 remains, which forms a continuous, open-pored, capillary-rich, highly active layer on the electrode plate 30. The nickel-molybdenum structure 34 has a multitude of cavities 36, which are interconnected via a multitude of passages 35.

[0049] Fig. Figures 3a to 3c show several different examples of how the arc wire spraying device 10 can be arranged relative to the carrier body 30.

[0050] In the Fig. In the example shown, the arc wire spraying device 10 is arranged vertically above the horizontally oriented carrier body 30, such that the main axis 37 of the spray cone 29 is at an angle of approximately 90° to the surface 40 of the carrier body 30.

[0051] In Fig. 3a The arc wire spraying device 10 is also arranged above the carrier body 30. However, in this example, the angle 38 between the main axis 37 of the spray cone 29 and the surface 40 of the carrier body 30 is less than 90°.

[0052] In Fig. Figure 3b shows an example in which the arc wire spraying device 10 is arranged next to the carrier body 30. This arrangement is also referred to as a horizontal arrangement. The principal axis 37 of the spray cone 29 emerging from the arc wire spraying device 10 is arranged at approximately 90° to the surface 40 of the carrier body 30.

[0053] Fig. Figure 3c shows another example of a horizontal arrangement, but the angle 38 between the principal axis 37 of the spray cone 29 emerging from the arc wire spraying device 10 and the surface 40 of the carrier body 30 is less than 90°.

[0054] In Fig. Figure 4a shows an example of an equivalent circuit diagram for the wiring of the arc wire spraying device 10. The first electrode 12 is formed by the first wire 17 and is connected to the positive terminal of the power source 14. The second electrode 13, or the second wire 18, is connected to the negative terminal of the power source 14. An arc 16 is formed between the two wire tips of the two wires 17 and 18. The polarity of the two wires can also be reversed.

[0055] In Fig. 4b shows another embodiment in the equivalent circuit diagram. In the Fig.In the example shown in Figure 4b, the arc wire spraying device 10 has two power sources 14' and 14". The first power source 14' is connected to the first electrode 12 or the first wire 17, with these being connected to the positive terminal of the first power source 14'. The positive (or negative) terminal of the second power source 14" is connected to the second electrode 13 or the second wire 18. The other terminals of the two power sources 14' and 14" are connected to a third, non-consumable electrode 39, which is also arranged in the arc zone 15. Arcs 16' and 16" are formed between the first electrode 12 and the third electrode 39, and between the second electrode 13 and the third electrode 39. The third electrode 39 is preferably made of a material that is non-consumable in the arc 16' or 16" respectively.

[0056] The electrode body K according to the invention has an active layer 32 made of a nickel-molybdenum alloy, which is permeated by a dense, continuous capillary network open at the top O. Immediately after the manufacture of the electrode body K, the capillary network is still filled with an alkali-sensitive filler metal, e.g., zinc, aluminum, magnesium, or the like, which is dissolved from the capillary network in a formation step, e.g., during the initial commissioning of the electrode body as an electrode in an electrolyzer. The associated arc wire spraying device 10 according to the invention comprises a two-wire burner in which an arc 16 is maintained between two wires 17, 18. The wires 17, 18 consist of different metals with different physical and chemical properties. They are continuously fed to the arc 16.The wire 17 is made of an alloy containing at least nickel and molybdenum as its main components. The other wire serves to create interconnected inclusions of alkali-sensitive metal within the nickel-molybdenum layer. The invention enables the coating of the substrate 30 with the most precise possible dosage of the nickel and molybdenum components on the one hand and the filler metal on the other. By using an arc wire spraying process, large areas can be coated in a relatively short coating process. Reference symbol: 10 Arc wire spraying device 11 arc wire burners 12 first electrode 13 second electrode 14 Power source 15 arc zone 16 arcs 17 first wire 18 second wire 19 Feed device 20 first feed unit 21 second feed unit 22 first contact 23 second contact 24 nozzle 25 Gas flow 26 Control unit 27 Storage device 28 molten wire material 29 spray cones K Electrode body 30 carrier bodies 31 Base layer 32 layers applied 33 Nickel-molybdenum structure 34 Aluminum structure 35 runs 36 cavities 37 Main axis of the spray cone 38 angles 39 third electrode 40 Nickel surface of the electrode body QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited non-patent literature

[0000] Improving plasma sprayed Raney-type nickel-molybdenum electrodes towards high-performance hydrogen evolution in alkaline medium” by Fatemeh Razmjooei, Taikai Liu, Daniela Aguiar Azevedo, Efi Hadjixenophontos, Regine Reissner, Günter Schiller, Syed Asif Ansar and Kaspar Andreas Friedrich, Scientific Reports 10 10948, DOI: 10.1038 / s41598-020-67954-y

[0003] Development of Highly Efficient Raney Nickel Electrodes for Alkaline Water Electrolysis” by Günter Schiller, Asif Ansar, Taikai Liu and Regine Reißner at the European Hydrogen Energy Conference (EHEC 2018) in Malaga, Spain

[0004] Wire-arc sprayed nickel based coating for hydrogen evolution reaction in alkaline solutions“ von Joel Fournier, Danielle Miousse und Jean-Gabriel Legoux im International Journal of Hydrogen Energy, Volume 24, Issue 6, 1999, Pages 519-528, ISSN 0360-3199

[0005] Kinetics of hydrogen evolution reaction on skeleton nickel and nickel-titanium electrodes obtained by thermal arc spraying technique“ von Andrea Kellenberger, Nicolae Vaszilcsin, Waltraut Brandl und Narcis Duteanu, October 2007, International Journal of Hydrogen Energy 32(15):3258-3265, DOI:10.1016 / j.ijhydene.2007.02.028

[0006]

Claims

[1] Electrode body (K), characterized by in that the electrode body (K) has a carrier body (30) on which an active layer (32) is arranged, wherein the active layer (32) is arranged on a non-porous nickel surface (40) which is formed on the carrier body (30). [2] Electrode body according to claim 1, characterized by that the carrier body (30) consists of a material whose main component is not nickel, and that the nickel surface (40) is formed on a base layer (31) applied to the carrier body (30) which consists of nickel or a nickel or nickel-aluminium alloy. [3] Electrode body according to one of the preceding claims, characterized bythat the active layer (32) of an unused electrode body (K) consists of a nickel-molybdenum alloy and a filler metal not alloyed therewith, wherein the volume ratio between the filler metal and the nickel-molybdenum alloy is between 1:1 and 3:1, particularly advantageously 2:

1. [4] Electrode body according to one of the preceding claims, characterized by , that the active layer (32) comprises a continuous nickel-molybdenum body and a continuous filler metal body, which are interlocked and each extend from the nickel surface (40) to the top side (O) of the active layer (32), and that the active layer (32) after removal of the filler metal body by leaching is an open-pored, coherent nickel-molybdenum body, the pore volume of which to the volume of the nickel-molybdenum body is in a ratio of between 1:1 and 3:1, particularly advantageously 2:

1. [5] Electrode body according to one of the preceding claims, characterized by that the active layer (32) contains nickel with a proportion of 1 to 32 wt.% molybdenum and that the filler metal is aluminum, magnesium, zinc or an alloy containing at least one of these metals. [6] Arc wire spraying device (10) for coating a carrier body (30) of an electrode body (K), comprising: at least one first electrode (12) and one second electrode (13) connected to at least one power source (14) to maintain an arc in an arc zone (15), both electrodes (12, 13) each being designed as a wire (17, 18) that can be melted by the arc, two feed units (20, 21) which are designed to continuously feed the respective wire (17, 18) to the arc zone (15), wherein the wire (17) of the first electrode (12) is made of an alloy containing at least nickel and molybdenum as main components. [7] Arc wire spraying device (10) according to claim 6, characterized by that the wire (18) of the second electrode (13) consists of an alloy whose main components differ from those of the wire (17) of the first electrode (12), the main component of the alloy being aluminum, magnesium or zinc. [8] Arc wire spraying device (10) according to claim 6 or 7, characterized by that the two feed units (20, 21) are connected to a control device (26) which is designed to adjust feed rates of the two feed units (20, 21) in a coordinated manner. [9] Arc wire spraying device (10) according to one of claims 6 to 8, characterized by that the alloy of the wire (17) of the first electrode (12) contains nickel and a proportion of 1 to 32 wt.% molybdenum and optionally one of the following minor components: iron, tungsten, copper, cobalt, chromium, gold, silver, titanium, niobium, tantalum and / or a proportion of: 0.05 to 12 wt.% iron, 0.05 to 10 wt.% tungsten and / or 0.05 to 10 wt.% chromium. [10] Arc wire spraying device (10) according to one of claims 6 to 9, characterized bya nozzle (24) which is designed to discharge a gas stream (25) flowing through the arc zone (15) for transporting the wire material (28) melted in the arc zone (15) in a spray cone (29) in the direction of the electrode body (K), wherein the nozzle (24) is preferably arranged such that the spray cone (29) impinges on a surface (40) of the electrode body (30) at a predetermined angle (38), wherein the spray cone (29) is preferably oriented at least substantially horizontally or vertically away from the nozzle (24) and the gas stream (25) is guided so as to envelop the wire material (28) melted in the arc zone (15). [11] Arc wire spraying device (10) according to one of claims 6 to 10, characterized by , that the first electrode (12) is connected to one pole of the power source (14) and the second electrode (13) is connected to another pole of the power source (14), or, that a common cathode (39) is assigned to the electrodes (12, 13), wherein the two electrodes (12, 13) are each connected to a pole of separate current sources (14', 14"), the respective other pole of which is connected to the common cathode. [12] Arc wire spraying method for coating a carrier body (30) of an electrode body (K) comprising the following measures: - maintaining at least one arc (16) in an arc zone (15) with at least two electrodes (12, 13), each formed as a wire (17, 18) that can be melted by the arc (16), one of the wires (17, 18) being made of an alloy containing at least nickel and molybdenum as main components, and the other of the two wires (17, 18) being made of another metal; and - continuous feeding of the wires (17, 18) into the arc zone (15). [13] Method according to claim 12, characterized bythat the wires (17, 18) are fed at different feed rates. [14] Method according to claim 12 or 13, characterized by that the composition of the active layer (32) is determined by influencing the feed rates of the two wires (17, 18). [15] Electrolyzer, in particular for producing hydrogen, with an electrode body (30) according to one of claims 1 to 5.

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