Metal body and method for manufacturing a metal body

Abstract

The invention relates to a metal body comprising a substrate (1) made of a metal material. At least one first layer (L1) made of Ni-X-Y is deposited on the surface of the substrate (1), where X is a chemical element selected from the group consisting of Al, Zn, Mg, Mn, Sn and / or a plurality of the aforementioned elements, and Y is a chemical element selected from the group consisting of Mo, Cr, Fe, Cu, Co, Ti, V, Ce and / or a plurality of the aforementioned elements. The at least one first layer (L1) has at least two layered regions having different phases according to a ternary phase diagram. In order to increase the specific surface area of the at least one first layer (L1), at least one of the lamellar phases forming the regions of the at least one first layer (L1) is completely or partially leached.

Description

Technical Field

[0001] The invention relates to a metal body and to a method for producing a metal body. Background Art

[0002] In order to carry out alkaline electrolysis, cost-effective and long-term effective electrodes are needed, thereby significantly reducing the production cost of hydrogen. Electrodes containing precious metals are still generally used for this purpose. If electrodes containing non-precious metals are used, these electrodes are generally Raney nickel electrodes or Ni-Mo electrodes. In the case of Raney electrodes, Ni-Zn alloys or Ni-Al alloys activated by chemical leaching are used. For example, patent specification DE2926641C2 discloses a method for manufacturing Raney nickel catalysts.

[0003] However, the manufacturing process often produces a large process variability, which has a significant impact on the activity of the final electrode. However, the manufacturing process is not suitable as the main factor in accurately manufacturing active electrodes; instead, the electrode structure and especially the available electrode surface are the main factors for the final activity of the Raney Ni electrode. Summary of the Invention

[0004] The basic object of the present invention is therefore to propose a metal body and a method for producing the same, by which the aforementioned disadvantages are avoided, ie by which an improved electrode activity can be effectively achieved.

[0005] According to the invention, this object is met by a metal body according to the main claim and a method according to the independent claim. Advantageous embodiments and further developments are described in the dependent claims.

[0006] A metal body having a substrate composed of a metallic material, wherein at least one first layer composed of Ni-XY (nickel-XY) is deposited on the surface of the substrate, wherein X is a chemical element selected from Al (aluminum), Zn (zinc), Mg (magnesium), Mn (manganese), Sn (tin), and / or a plurality of these elements (e.g., in the form of an alloy), and Y is a chemical element selected from Mo (molybdenum), Cr (chromium), Fe (iron), Cu (copper), Co (cobalt), Ti (titanium), V (vanadium), Ce (cerium), and / or a plurality of these elements (e.g., in the form of an alloy). The at least one first layer has at least two regions arranged in a layered manner and having different phases according to the ternary phase diagram. To increase the specific surface area of the at least one first layer, at least one of the layered phases forming the region of the at least one first layer is fully or partially leached, i.e., in particular, treated with an alkaline solution. In this regard, the application of an alkaline solution to the at least one first layer typically at least partially removes the at least one chemical element X and / or Y from the at least one first layer.

[0007] Leaching produces a structure characterized by being more robust, i.e. less leached, and more porous, i.e. more leached flakes or intermetallic phases, thereby generally producing an increased specific surface area and therefore an increased catalytically active surface area. Thus, manufacturing parameters can be set in a targeted manner to provide highly active electrodes (anode and cathode) for alkaline electrolysis and related processes. "Layered" is here particularly to be understood as an arrangement of layers (usually arranged on top of another layer), wherein the layers are arranged in the same manner and ideally arranged in parallel. The ternary Ni-XY structure used makes it possible to form various alternating ternary layered phases in at least one layer, in each case at least one layer being more leached than the other layered phases.

[0008] It can be provided that a non-layered intermediate layer of Ni—XY, Ni—X, Ni—Y or XY is arranged between the substrate and the at least one first layer in order to set the properties of the metal body in a more targeted manner.

[0009] Alternatively or additionally, at least one second layer composed of Ni—X—Y may be arranged on the surface of the at least one first layer facing away from the substrate, in order to also be able to modify the properties in a more targeted manner. In this regard, the at least one second layer may have at least two regions arranged in a layered manner and having different phases, and in this regard, preferably, at least one of the phases of the at least one second layer may differ from the phase of the at least one first layer, for example in composition.

[0010] The thickness of the at least one first layer is generally kept in the range of 1 μm to 50 μm, preferably in the range of 10 μm to 30 μm, ie the thickness amounts to 1 μm to 50 μm, preferably in the range of 10 μm to 30 μm.

[0011] The thickness of the regions with different phases, i.e., the individual flakes, is kept in the range of 100 nm to 10 μm, preferably in the range of 1 μm to 7 μm, particularly preferably in the range of 3 μm to 5 μm, i.e., the total thickness of the regions with different phases is 100 nm to 10 μm, preferably 1 μm to 7 μm, particularly preferably in the range of 3 μm to 5 μm. Thus, a relatively thin layered structure can be provided which still has a sufficiently large specific surface area.

[0012] The substrate may be formed as an open-cell foam to provide a sufficiently large surface to be coated.

[0013] Aqueous potassium hydroxide solutions and potassium / sodium tartrate solutions can be used as leaching solutions, but it is also possible to use NaOH, KOH, LiOH in pure form or mixtures thereof.

[0014] In particular, electrodes for alkaline electrolysis, or catalysts, may have a metal body having the above-mentioned properties.

[0015] In a method for producing a metal body, at least one first layer composed of Ni—XY is deposited on the surface of a substrate composed of a metallic material, where X is a chemical element selected from the group consisting of Al, Zn, Mg, Mn, and Sn, and / or a plurality of these elements, and Y is a chemical element selected from the group consisting of Mo, Cr, Fe, Cu, Co, Ti, V, and Ce, and / or a plurality of these elements. After application, the at least one first layer is subjected to a heat treatment that is terminated before complete concentration compensation, resulting in the formation of at least two regions in the at least one first layer that are arranged in a layered manner and have different phases according to the ternary phase diagram. Subsequently, to increase the specific surface area of the at least one first layer, at least one of the layered phases in the regions forming the at least one first layer is fully or partially leached.

[0016] Due to the formation of at least two phases, a structure is produced which reacts to different degrees to the application of alkali and is correspondingly modified to different degrees by leaching. The formation of two phases is made possible primarily by terminating the heat treatment before complete concentration compensation.

[0017] The heat treatment is typically performed at a temperature in the range of 600°C to 850°C (preferably 600°C to 700°C). This heat treatment is also preferably performed in a nitrogen atmosphere or an inert gas atmosphere. The heat treatment is typically performed for a period of 1 second to 15 minutes, but preferably for a maximum of 60 seconds. Therefore, the parameters can be set as needed to enable the formation of two phases.

[0018] The metal body is generally produced by the method. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Examples of embodiments of the present invention are shown in the accompanying drawings and will be referred to below. Figures 1 to 3 Provide explanation.

[0020] It shows:

[0021] Figure 1 a schematic side view of a coated metal body;

[0022] Figure 2 With two different layers corresponding to Figure 1 a view of a metal body; and

[0023] Figure 3 The corresponding Figure 1 view.

[0024] Figure 1A metal body consisting of a substrate 1 and a layered layer L1 arranged thereon is shown in a schematic side view. In the embodiment example shown, in the embodiment example selected, the substrate 1 is an open-pore nickel foam, the pore diameter of which is between 100 μm and 5000 μm. The layered layer L1 is applied to one side of the nickel foam, in other embodiment examples this can also take place on both sides. The metal body shown is used as a catalyst in heterogeneous and electrochemical catalysis. The microstructure achieved by this metal body is characterized in that a Ni-Al-Y layer is applied to the substrate 1 as a metal core, where Y is a chemical element which can be selected from Mo, Cr, Fe, Cu, Co, Ti, V and Ce or a plurality of these elements, for example Mo and Cr. This Ni-Al-Y layer can also surround the entire substrate 1 and be formed so that, starting from the substrate 1, Figure 1 In the layered structure shown, two different Ni—Al—Y phases always exist one after another, according to the ternary phase diagram; that is, they are arranged alternately in this layer L1. The flakes of this layered structure typically extend parallel or approximately parallel to the surface of the substrate 1, i.e., at an angle of up to 10°, preferably up to 5°. The thickness of individual flakes ranges from 100 nm to 10 μm; the thickness of the entire layer L1 ranges from 1 μm to 50 μm.

[0025] like Figure 2 Corresponding to Figure 1 As shown in a schematic side view of , in another embodiment example, another thin layer L2 can be applied to layer L1, or in principle, even more of these layers can be present. In this figure and the other figures, repeated features have the same reference numerals. Layer L2 also consists of (usually exactly) two different Ni-Al-X phases. In this regard, the phases of L1 and L2 can be different, with the further layer L2 usually having at least one phase different from the first layer L1. However, layer L2 can also have exactly one phase different from layer L1. The thickness of layer L2 and other such layers is also between 1 μm and 50 μm respectively. Even if aluminum is used in the embodiment example shown, the first layer L1 or the further layer L2 can also be formed from Ni-XY, where X is a chemical element selected from Al, Zn, Mg, Mn, Sn, or a combination of these elements.

[0026] like Figure 3 Corresponding to Figure 1 and 2 As shown in the schematic side view of FIG, there may be an intermediate layer 2 between the layered structures L1 and L2 and the substrate 1. The intermediate layer 2 is preferably made of Ni 2-x X x Al3 is formed and also has a thickness between 1 μm and 50 μm.

[0027] After applying the layers L1, L1 and L2, or the intermediate layers 2 and L1, L1 and L2, a leaching step is performed for the selective leaching of aluminum (or, if aluminum is not used, a corresponding alternative). This results in a preferential dissolution of one of the two platelet-forming phases within the respective layer L1 or L2. This results in a layered structure characterized by more solid (i.e., less leached) and more porous (i.e., more leached) platelets or phases. Overall, this results in an increase in the specific surface area, i.e., a larger catalytically active surface. DETAILED DESCRIPTION

[0028] Thus, in a first example, the manufacturing process of the metal body can be described as follows: Ni-Mo powder is applied to Ni foam, which is then alloyed in a first heat treatment step. This produces a Ni-Mo foam. Aluminum is then coated on one side of the Ni-Mo foam by atmospheric plasma spraying, and a second heat treatment step is performed. However, the second heat treatment step is completed before complete concentration compensation can occur, resulting in the formation of a lamellar phase region composed of the components Ni, Mo, and Al. This foam is now referred to as a Raney-Ni-Mo foam. Finally, the aluminum content in the Raney-Ni-Mo foam is leached in an alkaline solution. This leaching is carried out under ambient conditions in an aqueous solution of potassium hydroxide (1.8 M) and potassium / sodium tartrate (1.5 M). In the illustrated embodiment, the leaching step takes 24 hours, but can also take 18 to 30 hours. Subsequently, the leaching solution is replaced and heated to 353 K until gas production ceases, which typically takes 2 to 4 hours. One of the two phases can be leached better than the other, resulting in a structure with a very large internal surface area and a more durable sheet. The metal body produced in this way is removed from the leaching solution and thoroughly rinsed with water. This last-mentioned leaching step is always the same for the variants discussed below, except for the adjustment of the temperature (which, however, is always within the range of 330 K to 370 K) or the adjustment of the composition of the leaching solution.

[0029] In a first variation of the first embodiment, a composition of Ni 71.2 Mo 28.9 Ni-Mo powder is applied, and the first heat treatment is performed at 1280°C for one hour. Due to atmospheric plasma spraying, aluminum coating is then applied, and the second heat treatment is performed at 670°C in a nitrogen atmosphere. Typically, this heat treatment (the second heat treatment in this embodiment example) is performed at a temperature that is at least 10K and at most 20K higher than the melting temperature of the element to which the coating is applied.

[0030] In the second variant, the composition of Ni is again taken out 71.2 Mo 28.9As in the first variant, the aluminum coating is also applied by atmospheric plasma spraying, and the second heat treatment is carried out at 670°C, but now in an argon atmosphere.

[0031] In a third variant, the second heat treatment can also be carried out at a reduced temperature of 660° C., while the other parameters correspond to the second variant.

[0032] In a fourth variation of the first example, the Ni 71.2 Mo 28.9 Ni-Mo powder was prepared and the first heat treatment was carried out at 1280℃ for one hour. Aluminum powder was then sprayed on one side of the sample to be treated until the weight ratio of aluminum powder to foam (the mass of aluminum powder m Al粉 / (mass of the net m 网 +Mass of aluminum powder m Al粉 As in the second variant, the final heat treatment is carried out at 670° C. in an argon atmosphere.

[0033] In a second example, a Ni-Mo-Y mesh (e.g., Hastelloy C276 mesh) is coated with aluminum and subjected to a first heat treatment so that the lamellar phase region is formed by the components Ni, Mo, and Al and is now referred to as a Raney Ni-Mo mesh. Within 24 hours, the aluminum content is again leached out by the aforementioned leaching solution. Then, as in the first example, the leaching solution is replaced with a fresh potassium hydroxide (1.8 M) solution and a potassium / sodium tartrate (1.5 M) solution and heated to 353 K until gas generation stops after 2 to 4 hours. The metal body is thoroughly rinsed with water as usual. The leaching steps are also the same for all variations of the second example mentioned below.

[0034] In a first variant of the second example, a mesh serving as substrate 1 is sprayed with aluminum powder until the weight ratio of aluminum powder to mesh (mass of aluminum powder m Al粉 / (mass of the net m 网 +Mass of aluminum powder m Al粉 )) reached 13.4%. Heat treatment (corresponding to the second heat treatment of the first example) was then performed at 680°C in a nitrogen atmosphere.

[0035] In a second variant of the second example, the mesh was sprayed with aluminum powder until a proportion by weight of 33% was reached, and the heat treatment was again carried out in a nitrogen atmosphere.

[0036] In a third variant of the second example, a 0.1 mm thick aluminum foil was pressed on one side onto the Ni—Mo—X mesh at 70 MPa and the aforementioned heat treatment was again performed.

[0037] In a fourth variant of the second example, the aluminum foil was pressed on one side against a mesh at 145 MPa and then subjected to the heat treatment described.

[0038] The method can be configured flexibly: for example, the more readily leaching phase of layer L1 can also be present in layered layer L2, where a less readily leaching phase is present. By controlling the temperature and time, layer structures with specific properties can be produced in a targeted manner. The metal bodies are used as electrodes in electrolysis (e.g., alkaline electrolysis or chlor-alkali electrolysis) or other electrochemical processes (such as electroorganic synthesis or electrochemical CO2 reduction), and as Raney-Ni catalysts in heterogeneous catalysis.

[0039] Features of the various embodiments disclosed only in the embodiment examples can be combined with one another and can also be claimed individually.

Claims

1. A metal body comprising a substrate (1) made of a metal material, wherein: At least one first layer (L1) composed of Ni—XY is deposited on the surface of the substrate (1), wherein: X is a chemical element selected from Al, Zn, Mg, Mn, Sn and / or a plurality of the mentioned elements, and, Y is a chemical element selected from Mo, Cr, Fe, Cu, Co, Ti, V, Ce and / or a plurality of the mentioned elements, and, The at least one first layer (L1) has at least two regions arranged in a layered manner and having different phases according to the ternary phase diagram, wherein In order to increase the specific surface area of the at least one first layer (L1), at least one of the lamellar phases forming the region of the at least one first layer (L1) is completely or partially leached.

2. The metal body according to claim 1, characterized in that A non-laminated intermediate layer (2) consisting of Ni-XY, Ni-X, Ni-Y or XY is arranged between the substrate (1) and the at least one first layer (L1).

3. The metal body according to claim 1 or claim 2, characterized in that: At least one second layer (L2) composed of Ni—XY is arranged on the surface of the at least one first layer (L1) facing away from the substrate (1), wherein the at least one second layer (L2) has at least two regions arranged in a layered manner and having different phases, and in this regard, preferably at least one of the phases of the at least one second layer (L2) is different from the phase of the at least one first layer (L1).

4. Metal body according to any one of the preceding claims, characterized in that The thickness of the at least one first layer (L1) is maintained in the range of 1 μm to 50 μm, preferably in the range of 10 μm to 30 μm.

5. Metal body according to any one of the preceding claims, characterized in that The thickness of the regions with different phases, ie the thickness of the individual flakes, is kept in the range from 100 nm to 10 μm, preferably in the range from 1 μm to 7 μm, particularly preferably in the range from 3 μm to 5 μm.

6. Metal body according to any one of the preceding claims, characterized in that The substrate (1) is formed as an open-cell foam.

7. Metal body according to any one of the preceding claims, characterized in that The lamellar layer (L1) is formed on both sides of the substrate (1).

8. Metal body according to any one of the preceding claims, characterized in that The flakes in the lamellar layer (L1) are formed at an angle of at most 10°, preferably at most 5°, relative to the surface of the substrate (1).

9. An electrode or catalyst comprising the metal body according to any one of claims 1 to 8.

10. A method of manufacturing a metal body, wherein: At least one first layer (L1) composed of Ni—XY is deposited on the surface of a substrate (1) composed of a metal material, wherein: X is a chemical element selected from Al, Zn, Mg, Mn and Sn and / or a plurality of the mentioned elements, and Y is a chemical element selected from Mo, Cr, Fe, Cu, Co, Ti, V and Ce and / or a plurality of the mentioned elements, and The at least one first layer (L1) is subjected to a heat treatment after application, the heat treatment being terminated before complete concentration compensation, so that in the at least one first layer (L1), at least two regions are formed, which are arranged in a layered manner and have different phases according to the ternary phase diagram, and wherein Subsequently, in order to increase the specific surface area of the at least one first layer (L1), at least one of the lamellar phases forming the region of the at least one first layer (L1) is completely or partially leached.

11. The method according to claim 10, characterized in that The heat treatment is performed at a temperature in the range of 600° C. to 850° C., preferably in the range of 600° C. to 700° C., and is also preferably performed in a nitrogen atmosphere or a rare gas atmosphere.

12. The method according to claim 10 or claim 11, characterized in that The heat treatment is carried out over a period of 1 s to 15 min, but preferably a maximum of 60 s.

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