Method for producing a metal substrate catalyst unit

Abstract

Method for producing a metal substrate catalyst unit in which, in a first process step (i) a foil of aluminium, manganese, iron, cobalt or zinc or aluminium, manganese, iron, cobalt or zinc powder is applied to at least one surface of a planar substrate consisting of nickel, copper or cobalt, or the substrate is formed from an iron alloy coated on at least one outer surface with nickel, copper or cobalt, by means of roll cladding to form an aluminium, manganese, iron, cobalt or zinc cover layer, in a second procedural step ii) perforations are formed through the substrate coated in this way, in a third procedural step iii) a heat treatment is carried out at a minimum temperature that is at least 70% of the melting temperature of the foil material on the Kelvin scale and a maximum temperature that is below the lowest melting temperature of the coated substrate, and thereafter in a fourth procedural step iv) a leaching of aluminium, manganese, iron, cobalt or zinc with a basic or acidic aqueous liquid to form a Raney structure on the at least one surface formed with aluminium, manganese, iron, cobalt or zinc is carried out.

Description

[0001] The invention relates to a method for producing a metal substrate catalyst unit and its use, in particular in water electrolysis.

[0002] Electrodes with a Raney surface structure are commonly produced using electroplating processes (EP 3 159 433 A1) or thermal coating processes (thermal spraying). However, these known manufacturing methods have the significant disadvantage that continuous production does not appear to be possible.

[0003] US 3 846 344 A relates to a process for the production of nickel catalysts.

[0004] The disclosures of US 4 439 297 A and US 4 240 895 A are directed toward the manufacture of cathodes for chlor-alkali cells using a Raney alloy.

[0005] Furthermore, reference should be made to a page on "plattieren" in wissen / de / lexikon (https: / / wwww.wissen.de / lexikon / plattieren-metallbearbeitung).

[0006] The known manufacturing processes also have a low tolerance for iron impurities.

[0007] It is therefore an object of the invention to provide possibilities for a simplified and continuous manufacturing of metal substrate catalyst units, in particular electrodes whose surface has a covering layer with a Raney structure.

[0008] According to the invention, this problem is solved by a method according to claim 1. Advantageous embodiments and further developments of the invention can be realized with features specified in dependent claims.

[0009] In the process according to the invention, the procedure is such that in a first process step i) a foil of aluminium, manganese, iron, cobalt or zinc or aluminium, manganese, iron, cobalt or zinc powder is applied to at least one surface of a planar substrate consisting of nickel, copper or cobalt, or in which the substrate is formed from an iron alloy coated on at least one outer surface with nickel, copper or cobalt, by means of plating to form an aluminium, manganese, iron, cobalt or zinc cover layer.

[0010] In a subsequent second process step ii), openings are formed through the substrate thus coated.

[0011] Then, in a third process step iii), a heat treatment is carried out at a minimum temperature that is at least 70% of the melting temperature of the material of the film based on the Kelvin scale and a maximum temperature that is below the lowest melting temperature of the coated substrate.

[0012] Following this, in a fourth process step iv) a leaching of aluminium, manganese, iron, cobalt or zinc is carried out with a basic or acidic aqueous liquid to form a Raney structure on the at least one surface formed with aluminium, manganese, iron, cobalt or zinc.

[0013] Preferably, metal substrate catalyst units should be manufactured with a substrate of nickel or a nickel-coated substrate of an iron alloy, in particular a steel, which is provided with at least one covering layer of aluminium on at least one surface of the substrate.

[0014] Substrates in the form of sheets with a thickness ranging from 0.1 mm to 5 mm can be used. If substrates coated with nickel, copper, or cobalt are used, a foil of aluminum, manganese, iron, cobalt, or zinc can be plated onto them. This plated coating should have a thickness ranging from 10 µm to 500 µm.

[0015] In process step i), it is advantageous to provide two opposing surfaces of the respective substrate with a covering layer by plating.

[0016] Process step i) is carried out by means of roll cladding. In this process, the substrate and film are guided together through the roll gap of the cladding stand and, by applying very high rolling pressure and thus a significant reduction in thickness, are brought into metallic adhesion. By using the substrate and film in the form of wound strip coils, the resulting composite material can be continuously produced in coil form with a large strip length.

[0017] The substrate and film can be fed together through the roller gap, and the cladding process can be carried out using the film material. Alternatively, the films can be fed through the roller gap at the two opposing surfaces of the substrate, and the substrate can be cladding at these two opposing surfaces.

[0018] When a powder is used to form a top layer, it can be applied evenly to a surface. The substrate coated in this way can then be passed through the roller gap and the top layer formed with the powder material by plating.

[0019] Alternatively, a binder can be added to the powder, the powder-binder mixture applied to at least one substrate surface, and the adhesive forces of the binder utilized. It is advantageous to use a binder that can be removed in one of the subsequent process steps, particularly in process step iii). To remove a binder, an additional process step can be carried out in which the binder is removed thermally or, for example, by dissolving it with a solvent suitable for the binder.

[0020] The formation of the openings in process step ii) can be carried out by plastic deformation, punching, drilling, stretching, cutting and / or simultaneous stretching deformation, with non-cutting methods being preferred. Openings should be formed in a regular arrangement, each with the same size and geometry of the free cross-sectional area. The free cross-sectional areas should have a size in the range of 0.01 mm. 2 up to 30 mm 2 be trained.

[0021] A temperature in the range of 450 °C to 1400 °C should be maintained in process step iii), while maintaining an inert atmosphere.

[0022] Through heat treatment in process step iii), diffusion effects and phase transformation lead to increased long-term efficiency during the operation of a metal substrate catalyst unit, in particular an electrode.

[0023] In process step iv), sodium hydroxide or potassium hydroxide solution in combination with potassium / sodium tartrate solution, as well as an ammonium sulfate solution, can be used to leach aluminum, manganese, iron, cobalt, or zinc from the surface layer. Up to 5 M sodium hydroxide solution, 1.8 M potassium hydroxide solution, 1.5 M potassium / sodium tartrate solution, or 5 M ammonium sulfate solution can be used. Potassium hydroxide solution in combination with potassium / sodium tartrate solution is preferred for leaching aluminum.

[0024] Leaching should be carried out over a period of at least 1 hour at a temperature in the range of 5 °C to 95 °C.

[0025] Aluminium, manganese, iron, cobalt or zinc can be removed from the respective top layer in the range of 0.1 wt.% to 95 wt.%, preferably 37 wt.% to 90 wt.%.

[0026] In process step i), a uniform layer thickness of an aluminium, manganese, iron, cobalt or zinc cover layer in the range of 10 µm to 500 µm, preferably in the range of 50 µm to 100 µm, should be maintained.

[0027] Separation at the substrate and singulation after process step i) or one of the other three process steps ii) to iv) can be carried out in order to provide individual metal substrate catalyst units in a specific predefinable geometry and dimension, in particular for use as an electrode.

[0028] The invention enables the production of electrodes, as an example of metal substrate catalyst units, with increased productivity and at lower costs.

[0029] The metal substrate catalyst units produced by the inventive method can be used in electrolysis processes, in particular designed and used as electrodes, for the production of hydrogen, oxygen, chlorine or also for the reduction of carbon derivatives, such as CO2 or unsaturated hydrocarbons.

[0030] The metal substrate catalyst units can be used particularly advantageously in alkaline water electrolysis, especially in so-called zero-gap and membrane electrolyzers.

[0031] The invention will now be explained in more detail using an example.

[0032] In a first process step i) aluminium plating foil is applied to both sides of a nickel sheet as a substrate by roller plating, resulting in a total thickness of 1 mm.

[0033] In the second process step ii), openings are formed by cutting and subsequent stretching with dimensions of 1 mm × 5 mm.

[0034] The heat treatment in process step iii) is carried out at temperatures between 450 °C and 650 °C under an N2 atmosphere, preferably between 560°C and 640°C.

[0035] The chemical leaching of the heat-treated and aluminium-plated substrate is carried out in process step iv) by immersion in 1.8 M potassium hydroxide solution (KOH) and 1.5 M potassium / sodium tartrate solution for 24 h at temperatures up to 80°C and formation of hydrogen gas.

[0036] Electrical overvoltages of less than 100 mV were possible at an electrical current density of 300 mA / cm². 2for the hydrogen evolution reaction in an alkaline electrolyte (30 wt% KOH, 60°C) with an electrode produced in this way as an example of a metal substrate catalyst unit in alkaline water electrolysis.

Claims

[1] Process for the production of a metal substrate catalyst unit in which in a first process step (i) a foil of aluminium, manganese, iron, cobalt or zinc or aluminium, manganese, iron, cobalt or zinc powder is applied to at least one surface of a planar substrate consisting of nickel, copper or cobalt, or the substrate is formed from an iron alloy coated on at least one outer surface with nickel, copper or cobalt, by means of roll cladding to form an aluminium, manganese, iron, cobalt or zinc cover layer, in a second procedural step ii) perforations are formed through the substrate coated in this way, in a third procedural step iii) a heat treatment is carried out at a minimum temperature that is at least 70% of the melting temperature of the foil material on the Kelvin scale and a maximum temperature that is below the lowest melting temperature of the coated substrate, and thereafter in a fourth procedural step iv) a leaching of aluminium, manganese, iron, cobalt or zinc with a basic or acidic aqueous liquid to form a Raney structure on the at least one surface formed with aluminium, manganese, iron, cobalt or zinc is carried out. [2] Method according to claim 1, characterized by , that the formation of the openings in process step ii) is carried out by plastic deformation, punching, cutting, drilling, shearing and / or simultaneous stretching deformation. [3] Method according to any one of the preceding claims, characterized by, that a temperature in the range of 450 °C to 1400 °C is maintained in process step iii), while maintaining an inert atmosphere. [4] Method according to any one of the preceding claims, characterized by , that in process step iv) sodium or potassium hydroxide in combination with potassium / sodium tartrate in an aqueous solution or even just ammonium sulfate in an aqueous solution is used for leaching. [5] Method according to the preceding claim, characterized by that the leaching process is carried out over a period of at least one hour at a temperature in the range of 5°C to 95°C. [6] Method according to any one of the preceding claims, characterized by , that in process step ii) openings are formed in a regular arrangement, each with the same size and geometry of the free cross-sectional area. [7] Method according to any one of the preceding claims, characterized by, that in process step i) a uniform layer thickness of an aluminium, manganese, iron, cobalt or zinc cover layer in the range of 10 µm to 500 µm is maintained. [8] Method according to any one of the preceding claims, characterized by , that in process step iv) aluminium, manganese, iron, cobalt or zinc is removed in a proportion ranging from 0.1 wt% to 95 wt%.