WO2024261241A1 - Electrode body, arc wire spray device, and method for producing an electrode body - Google Patents

Abstract

The electrode body K according to the invention has an active layer (32) made of a nickel-molybdenum alloy which is drawn through a dense continuous capillary network that is open on the upper face O. Immediately after the production 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 removed from the capillary network in a forming step, e.g. when the electrode body is first operated as an electrode in an electrolyzer. The corresponding arc wire spray device (10) according to the invention comprises a dual-wire torch 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, and the wires are continuously supplied to the arc (16). The wire (17) is made of an alloy which contains at least nickel and molybdenum as main constituents. The other wire is used to produce continuous intercalations of alkali-sensitive metal in the nickel-molybdenum layer. The invention allows the support body (30) to be coated with a proportion of nickel and molybdenum constituents and filler metal which is as exact as possible. By using the arc wire spraying method, large surfaces can be coated in a relatively brief coating process.

Description

Electrode body and arc wire spraying device and

Method for producing an electrode body

[0001] The invention relates to an arc wire spraying device for coating a (preferably metallic) electrode body, 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 generating hydrogen or as an anode. The invention also relates to a coated electrode body and an arc wire spraying method for producing an electrode body.

[0002] In the field of alkaline electrolysis (AEL), it is generally known to provide the electrode bodies with coatings in order, for example, to increase the efficiency of the electrolyzer by increasing the surface 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 Hadj ixenophontos , Regine Reissner, Günter Schiller, Syed Asif Ansar and Kaspar Andreas Friedrich, Scientific Reports 10 10948, DOI: 10 . 1038 / s41598- 020- 67954-y describes a sheet coated with a nickel-aluminium-molybdenum alloy that is 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 potash, serves as the electrolyte. Usually, a potassium hydroxide solution is used that has a concentration in the range of 20 to 40 %. Caustic potash is particularly reactive towards aluminum, so that the aluminum is quickly and severely corroded by the caustic potash. Nickel, on the other hand, is very resistant to alkaline solutions and can serve as a type of shield against the highly corrosive electrolyte in the coating. The addition of molybdenum serves to increase the intrinsic activity in order to increase the efficiency of hydrogen production in alkaline electrolysis. Other alloy components that can increase the intrinsic activity include: tungsten, iron, cobalt, titanium, niobium, tantalum, chromium, gold, iridium, rhenium, rhodium and platinum. During (initial) operation of the alkaline electrolyzer with electrode bodies coated in this way, the aluminum components in the coating are leached out by the electrolyte, so that the coating forms a porous structure with a relatively large surface area, which can further improve the catalytic properties of the coating.

[ 0004 ] This nickel-aluminium-molybdenum coating is applied in the state of the art exclusively by atmospheric plasma spraying with powder or by vacuum plasma spraying with powder (see “Development of Highly Efficient cient 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, only low deposition rates can be achieved with both coating processes, so that they are not particularly suitable for large-area electrode bodies due to the relatively long coating time in production. In addition, with these coating processes, the composition of the coating can only be adjusted via the powder admixture, which can make the exact adjustment of the proportions of molybdenum, nickel and aluminum in the coating produced considerably more difficult.

[0005] In "Wire-arc sprayed nickel based coating for hydrogen evolution reaction in alkaline solutions" by Joel Fournier, Danielle Miousse and Jean-Gabriel Legoux 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 layer of nickel-aluminum is applied to an electrode body using an arc wire spraying process. In this process, an arc is generated between two wires. The tips of the wires are melted by the arc while the wires are continuously fed. The molten wire material is accelerated by a gas stream in the direction of the electrode body and is thereby applied to it. Nickel-aluminum and/or aluminum wires are used as wires, for example.

[0006] In “Kinetics of hydrogen evolution reaction on skeleton nickel and nickel-titanium electrodes obtained by thermal arc spraying technique” by Andrea Kellenberger, Nicolae Vas zilcsin, Waltraut Brandl and Narcis Duteanu, October 2007 , International Journal of Hydrogen Energy 32 ( 15 ) : 3258-3265 , DOI : 10 . 1016/ j . ij hydene . 2007 . 02 . 028 is also an arc wire spraying process with two melting wires, where one wire is made of nickel-titanium and the other wire is made of aluminum.

[ 0007 ] Based on this, the invention is based on the object of creating a highly effective electrode body with which alkaline electrolysis in hydrogen production can be carried out with increased efficiency. It is also the object of the invention to provide an arc wire spraying device suitable for producing such electrode bodies and a corresponding method. The method should be able to produce a coating with a highly active and highly porous structure.

[ 0008 ] This object is achieved 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, with the arc wire spraying method according to claim 12 and with the electrolyzer according to claim 15:

[ 0009 ] The electrode body according to the invention has a carrier body on which an active layer is arranged. The carrier body is in particular a metallic component, such as a sheet metal, a plate or a metal grid or sieve. The electrode body is preferably suitable for use in an (alkaline) electrolyzer. The active layer of the electrode body is, immediately after its production, a layer in which zones made of a filler metal, e.g. aluminum, magnesium, zinc or another metal sensitive to alkalis, and zones made of a nickel-molybdenum alloy. These zones penetrate each other, with little to no isolated areas enclosed by the other metal. Each zone thus forms a largely coherent body, with the two bodies preferably interlocking with one another without any cavities. The zones of the unused electrode body can have a volume ratio of 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 by forming. To do this, the electrode body is brought into contact with an alkali solution and, if necessary, connected to the positive pole of a direct voltage source, which dissolves the filler metal body. The electrode body can now be used as an electrode, in particular the cathode of an electrolyzer. Forming can be carried out, for example, during (first-time) operation of the alkaline electrolyzer using the alkaline electrolyte or in a leaching step before the alkaline electrolyzer is put into operation. Potassium hydroxide, for example, can be used to leach the filler metal. The nickel-molybdenum structure that remains after leaching is both highly porous and sponge-like. The structure is particularly open-pored, i.e. at least a large proportion of the individual pores are connected to one another.

[0011] In the formed state, the active layer is a highly porous, open-pored nickel-molybdenum layer with hanging microchannels. Preferably, the microchannels have an inner surface with high roughness and thus high catalytic activity. The pores form channels, each of which extends from the nickel surface to the top of the active layer. After the aluminum body has been removed by leaching, the active layer is formed by 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. The active layer consists predominantly of nickel with a proportion of 1 wt.% to 32 wt.% molybdenum and optionally secondary 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 layer produced can, for example, contain a proportion of 40 to 60 wt.% nickel, a proportion of 10 to 25 wt.% molybdenum (nickel and molybdenum in alloy) and a proportion of 20 to 45 wt.% aluminum (or other filler metal). The layer produced can also be flat and have a low surface waviness, for example a waviness that corresponds to a value of 0.5 times the material thickness of the layer produced. The waviness describes the distance between periodically recurring components in the surface texture. The lowest possible waviness of the coating is particularly important when using the electrode body as a cathode (or anode) in an alkaline electrolyzer. advantageous because the plate-shaped electrode body can lie as flush as possible against an (ion-conductive) diaphragm without hydrogen bubbles accumulating in between, which could reduce the efficiency of the electrolyzer. In addition, the overall length of the alkaline electrolyzer is shortened and the capacity is increased by reducing the distance between the electrode plates, which once again contributes to increasing efficiency.

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

[ 0014 ] If the base layer is made of a nickel-aluminium alloy, the aluminium content is preferably less than 20 wt.%. The base layer ensures reliable adhesion of the active layer to the carrier body and is suitable for shielding the carrier body 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. aluminium, magnesium, zinc or similar). An arc wire spraying process can be used, for example. which uses two wire electrodes each made of a nickel alloy or two wire electrodes each made of a nickel-aluminium alloy.

[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 in order 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 assigned a feed unit that is designed to continuously feed the respective wire to the arc zone. One of the wires is made of an alloy that contains at least nickel and molybdenum as main components. The other wire consists of a metal that is soluble in an alkali solution, for example aluminum, magnesium, zinc or their alloys or the like. The two wires can have the same or different diameters. The diameter of the aluminum wire is preferably 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 the nickel and molybdenum components in the layer produced. By using the arc wire spraying process with simultaneous feeding of two wires of different material into an arc zone, large areas in particular 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 inventive Both the appropriate coating equipment and the coating process are superior to conventional systems and processes, in particular powder coating systems and processes.

[ 0017 ] A special feature of the arc wire spraying device according to the invention is that it can be used to produce a highly porous and at the same time highly active coating on the carrier body. The volume fraction of the nickel-molybdenum alloy in the layer produced can be precisely adjusted.

[ 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 takes place without or with only brief interruptions, for example with interruptions in the millisecond range.

[ 0019 ] The wires, insofar as they consist of alloys, have main components and secondary components. The main components of an alloy are in particular those components which make up the largest proportion in weight % in the alloy. The main component is in particular the base metal from which the alloy is composed.

[ 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 can be made of nickel-molybdenum and aluminum, magnesium or zinc, where the aluminum or zinc portion in the structure is not alloyed with the nickel-molybdenum portion of the structure.

[ 0021 ] Each electrode, i.e. each wire, is assigned its own feed unit which is designed to continuously feed the respective wire into the arc zone. The feed rates specified by the first and second feed units can be adjusted independently of one another by independently adjusting the feed speeds of the feed units. This allows the ratio of nickel-molybdenum alloy to aluminum or magnesium or zinc in the coating to be precisely adjusted via the feed rates of the two wires into the arc zone. The feed rate is understood to mean the amount of material fed per unit of time by volume or weight. The feed rate depends on the wire thickness 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 can further improve the catalytic activity of the layer produced. Components of an alloy are understood to mean additions to the alloy which are not present in such an amount that they are among the main components. In particular, the alloy of the first wire contains a proportion of 0.05 to 12 wt.% iron, a proportion of 0.05 to 10 wt.% tungsten and/or a proportion of 0.05 to 10 wt.% chromium. Preferably, the alloy contains one or more components with the following proportions: from 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 which is designed to direct a gas flow through the arc zone, whereby the wire material molten in the arc zone is accelerated in a spray cone in the direction of the carrier body of the electrode body to be produced. The gas flow can in particular mix and atomize the molten wire material, i.e. the droplets of the molten wire material are broken down, for example, by the shear forces occurring in flight. The gas flow can be a pure gas flow or a mixed gas flow, e.g. an air flow. The gas can be an inert gas or an inert gas, in particular a noble gas such as argon. The nitrogen or another inert gas prevents oxidation of the molten wire material before the wire material hits the surface of the carrier body. This allows a layer of melted wire material to form on the surface of the carrier body.

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

[0026] In particular, the spray cone is aligned, at least substantially, horizontally or vertically to the nozzle. If the spray cone is aligned vertically to the nozzle, the acceleration forces of the gas flow and gravity act in parallel on the droplets contained in the gas flow. If the spray cone is aligned, at least substantially horizontally to the nozzle, gravity acts transversely to the direction of flight 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 carrier body is preferably in a range of 100 mm to 500 mm.

[0027] In particular, the gas stream at least partially, 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 a positive pole of the power source and the second electrode to a negative pole of the power source. The first electrode can thereby form the anode and the second electrode the cathode for the arc. The anode can be 200°C up to 500°C hotter than the cathode. Depending on the required melting temperature of the wire The polarity of the circuit can be adjusted in this way. Alternatively, the first electrode can be connected to the negative pole of the power source and the second electrode to the positive pole of the power source.

[ 0029 ] In an alternative embodiment, the arc wire spraying device has a third electrode, referred to here as the cathode, wherein the first and the second electrode are each connected to one, e.g. the positive pole of separate power sources and the third electrode is connected to the other pole of the two separate power sources. Conversely, the first and the second electrode can each be connected to a negative pole of separate power sources. The higher-melting wire can also be connected to the positive pole of its source and the lower-melting wire to the negative pole of its source. The third electrode is connected to the other pole of the two sources. The cathode consists of a durable material, e.g. tungsten, which cannot be melted in the arc.

[ 0030 ] The object of the invention is also achieved by an arc wire spraying method for coating a carrier body of an electrode body, which comprises the following steps:

- Maintaining an arc in an arc zone with at least two electrodes, wherein at least the electrodes are designed as wires which can be melted by the arc, wherein one of the wires is made of an alloy which contains at least nickel and molybdenum as main components: and - continuous feeding of the wires into the arc zone.

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

[0032] Preferably, by introducing the gas stream into the arc zone, a droplet stream of the molten wire material is created which reaches a flow velocity of 60 m/s, preferably 70 m/s, particularly preferably 80 m/s or more.

[0033] Further details as well as advantageous developments or details of the invention emerge from the drawings, the description and the claims. They show:

[0034] Figure 1 is a schematic representation of an example of the arc wire spraying device according to the invention;

[0035] Figure 2 is a schematic detailed view of the electrode body with produced coating;

[0036] Figures 3a to 3c show several examples of how the arc wire torch can be arranged relative to the electrode body; and

[0037] Figures 4a to 4b show several examples of how the electrodes are connected to the power source.

[0038] Figure 1 shows a schematic view of a Example of the arc wire spraying device 10 according to the invention. Figure 1 shows one type of arc wire spraying device 10, but the arc wire spraying device 10 can stand for any type of arc wire spraying device on which the inventive concept can be implemented with a wire melting in an arc zone as an electrode, which wire is made of an alloy that mainly contains nickel and molybdenum.

[ 0039 ] The arc wire spraying device 10 is provided for coating a carrier body 30 to produce an electrode body K. The carrier body 30 can be formed, for example, by a sheet metal, a metal plate or also a non-planar body made of metal or another electrically conductive material.

[ 0040 ] The arc wire spraying device 10 has 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 can also have a communication interface in order to exchange information with other components.

[ 0041 ] 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 connected by a first wire 17 and the second electrode

13 is formed by a second wire 18. The first wire 17 and the second wire 18 can be melted in the arc 16 in the arc zone 15 and are guided laterally in a plane into the arc zone 15. [ 0042 ] For this purpose, the arc wire spraying device 10 also has a feed device 19 which is designed to continuously feed the two wires 17, 18 to the arc zone 15, in which the wires 17 and 18 are melted by the arc 16. The feed device 19 has a first feed unit 20 and a second feed unit 21, each of which is assigned to one of the wires 17, 18. The first feed unit 20 is designed to feed the first wire 17 to the arc zone 15 at an adjustable feed rate, while the second feed unit 21 is designed to feed the second wire 18 to the arc zone 15 at an adjustable feed rate. The first wire 17 and also the second wire 18 are each obtained from a reservoir not shown in detail, which can be formed, for example, by unrollable wire rolls.

[ 0043 ] 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 designed to introduce a gas flow 25 into the arc zone 15.

[ 0044 ] In the example shown in Figure 1, the first wire 17 is made of an alloy containing nickel and molybdenum as the main components. The second wire 18, however, is made of an alloy whose main component is aluminum. The first wire 17 is preferably connected to the positive pole of the power source 14 via the contact 22, while the second wire 18 is connected to the positive pole of the power source 14 via the contact 22. the contact 23 is connected to the other pole of the power source 14. A reverse polarity to the polarity shown in Figure 1 is also possible.

[ 0045 ] The arc wire spraying device 10 shown in Figure 1 also has a control device 26 which can be communicatively connected to the feed units 20, 21 and the power source 14. In addition, the control device 26 can also be communicatively connected to the nozzle 24 or an element regulating the gas flow of the nozzle.

[ 0046 ] The power source 14 is controllable, for example the control device 26 can predetermine a desired current intensity, a desired voltage or a desired characteristic curve for the power source 14. The control device 26 can also be set up to set the feed rates of the first feed unit 20 and the second feed unit 21 separately from one another. The feed rates are determined by the conveying speeds of the two feed units 20, 21.

[ 0047 ] The control device 26 can, for example, set the feed rates of the two wires 17, 18 in a desired ratio of e.g. 1:2, which sets a suitable current of 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 device 26 can increase or decrease the feed rates according to the detected current (preferably in a fixed ratio to one another) in order to achieve a desired current strength. [ 0048 ] In addition, the control device 26 can be designed to provide the power source with an appropriate voltage or to regulate the gas flow 25.

[ 0049 ] The control device 26 can access data, such as models, stored in a memory device 27 for setting the parameters (feed rates of the feed units and current intensity, voltage, characteristic curve type, etc.). The models stored in the memory device 27 can describe a relationship between the individual parameters and the expected composition of the coating produced. For example, predetermined compositions of nickel molybdenum to aluminum or zinc can be assigned one or more parameter sets in the stored models, with which the composition can be achieved in the coating.

[ 0050 ] The gas stream 25 introduced into the arc zone 15 mixes and accelerates the wire material 28 molten in the arc 16 in a spray cone 29 in the direction of the carrier body 30 . The molten wire material 28 is preferably completely enveloped by the gas stream 25 . The gas of 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 in the direction of the carrier body 30 forms a generated layer 32 on the surface 40 of the carrier body 30 .

[ 0051 ] The electrode body K shown in Figure 1 has between the carrier body 30 and the layer 32 a base layer 31 which consists of a nickel alloy or a Nickel-aluminium alloy. The base layer 31 can be applied, for example, using an arc wire spraying device 10 of the above type, but then the first wire 17 and the second wire 18 can each be made of a nickel or nickel-aluminium alloy. Instead of this two-wire burner, a single-wire burner can also be provided for producing the base layer 31.

[ 0052 ] Figure 2 shows a detailed view of the electrode body K with the carrier body, the base layer 31 and the layer 32 applied with the arc wire spraying device 10. The applied layer 32 has a structure

33 made of nickel-molybdenum (shown hatched in Figure 2) and another structure 34 made of aluminum (not hatched in Figure 2), which are mixed together in such a way that the volume ratio of nickel-molybdenum alloy to aluminum is as close to 1:2 as possible. The aluminum structure 34 extends continuously from the base layer 31 to the top 0. The structure 33 also extends continuously from the base layer 31 to the top 0. The aluminum structure 34 can be leached out of the layer 32 with a potassium hydroxide solution (with potassium hydroxide solution), so that after the aluminum has been leached out, only the nickel-molybdenum structure 33 remains, which forms a continuous, open-pored, highly active layer on the electrode plate 30, permeated by capillaries. The nickel-molybdenum structure

34 has a plurality of cavities 36 which are connected to one another via a plurality of passages 35.

[ 0053 ] Figures 3a to 3c show several different Examples of how the arc wire spray device 10 can be arranged relative to the carrier body 30.

[ 0054 ] In the example shown in Figure 1, the arc wire spraying device 10 is arranged vertically above the horizontally oriented carrier body 30 so 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.

[ 0055 ] In Figure 3a, the arc wire spraying device 10 is also arranged above the carrier body 30. However, the angle 38 between the main axis 37 of the spray cone 29 and the surface 40 of the carrier body 30 is smaller than 90° in this example.

[ 0056 ] 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 main 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.

[ 0057 ] Figure 3c finally shows another example of a horizontal arrangement, however, the angle 38 between the main axis 37 of the spray cone 29 emerging from the arc wire spraying device 10 relative to the surface 40 of the carrier body 30 is less than 90 °.

[ 0058 ] Figure 4a shows an equivalent circuit diagram of the wiring of the arc wire spraying device 10 as an example. The first electrode 12 is formed by the first wire 17 and is connected to the positive pole of the power source 14. The second electrode 13 or the second wire 18 is connected to the negative pole 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.

[0059] Figure 4b shows a further embodiment in the equivalent circuit diagram. 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, which are connected to the positive pole of the first power source 14'. The positive (or negative) pole of the second power source 14'' is connected to the second electrode 13 or the second wire 18. The other poles 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 cannot be melted in the arc 16' or 16''.

[0060] The electrode body K according to the invention has an active layer 32 made of a nickel-molybdenum alloy, which is penetrated by a dense, coherent capillary network that is open at the top 0. Immediately after the electrode body K has been produced, the capillary network is filled with an alkali-sensitive filler metal, e.g. zinc, aluminum, magnesium or the like, which is formed in a forming step, e.g. when the electrode body is first put into operation as an electrode in an electrolyzer, from the capillary network is released. The associated arc wire spraying device 10 according to the invention comprises a two-wire torch 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 that contains at least nickel and molybdenum as main components. The other wire is used to produce coherent deposits of alkali-sensitive metal in the nickel-molybdenum layer. The invention enables the carrier body 30 to be coated 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 spray device

11 arc wire torches

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 stream

26 control device

27 storage device

28 on molten wire material

29 spray cones

K electrode body

30 carrier bodies

31 base layer

32 applied layers

33 nickel molybdenum structure

34 aluminum structure

35 rounds

36 cavities

37 Main axis of the spray cone

38 angles

39 third electrode

40 Nickel surface of the electrode body

Claims

Patent claims: 1. Electrode body (K), characterized 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 in 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-aluminum alloy. 3. Electrode body according to one of the preceding claims, characterized in that the active layer (32) of an unused electrode body (K) consists of a nickel-molybdenum alloy and a filler metal not alloyed therewith, the volume ratio between the filler metal and the nickel-molybdenum alloy being between 1:1 and 3:1, particularly advantageously 2:1. 4. Electrode body according to one of the preceding claims, characterized in that the active layer (32) has a continuous Nickel-molybdenum body and a continuous filling metal bodies that are interlocked and are each formed extending from the nickel surface (40) to the top (0) 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 whose pore volume 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 in 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 a second electrode (13) which are connected to at least one power source (14) in order to maintain an arc in an arc zone (15), wherein both electrodes (12, 13) are each designed as a wire (17, 18) which 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 which contains at least nickel and molybdenum as main components. 7. Arc wire spraying device (10) according to claim 6, characterized in 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 in 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 in 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 secondary 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 by a nozzle (24) which is designed to direct a gas stream (25) flowing through the arc zone (15) for transporting the molten metal in the arc zone (15) Wire material (28) 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) strikes a surface (40) of the electrode body (30) at a predetermined angle (38), wherein the spray cone (29) is preferably aligned at least substantially horizontally or vertically away from the nozzle (24) and the gas flow (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 in that the first electrode (12) is connected to one pole of the power source (14) and the second electrode (13) 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 one pole of separate power sources (14', 14''), the 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 of which is designed 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) consists of another metal; and - continuous feeding of the wires (17, 18) into the arc zone (15). 13. Method according to claim 12, characterized in that the wires (17, 18) are fed at different feed rates. 14. Method according to claim 12 or 13, characterized in 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.