Catalyst materials for water electrolysis

Abstract

The invention relates to a catalyst material for water electrolysis, wherein the catalyst material comprises nickel, iron and cobalt, and wherein a) the catalyst material has a nickel content between 48 atomic% and 74 atomic%, an iron content between 13 atomic% and 26 atomic%, and a cobalt content between 13 atomic% and 26 atomic%, each based on the total number of atoms of the sum of nickel, iron and cobalt, or b) the catalyst material has a cobalt content between 48 atomic % and 74 atomic %, an iron content between 13 atomic % and 26 atomic %, and a nickel content between 13 atomic % and 26 atomic %, each based on the total number of atoms of the sum of nickel, iron and cobalt. Furthermore, the invention relates to a catalyst comprising the catalyst material described above. The invention also relates to the use of the catalyst material described above, or of the catalyst described above, in water electrolysis.

Description

[0001] The invention relates to the field of catalyst materials for water electrolysis.

[0002] Furthermore, the invention relates to a catalyst comprising the above catalyst material.

[0003] Furthermore, the invention relates to the use of the above catalyst material or the use of the above catalyst in water electrolysis.

[0004] In water electrolysis, the water molecule is split into hydrogen and oxygen gases using electrical energy at the cathode and anode of an electrolysis cell, respectively. An important application of water electrolysis is hydrogen production, as it has the potential to replace hydrogen production from fossil fuels as renewable energy sources expand.

[0005] Furthermore, water electrolysis enables the chemical storage of surplus wind and solar power generated from fluctuating renewable energy sources, particularly wind and solar power. The hydrogen produced can be used for chemical processes or fed directly into the natural gas grid as methane, either directly or after subsequent methanization.

[0006] The catalyst materials used in water electrolysis typically have a very high precious metal content, which is associated with high costs. Furthermore, the availability of sufficient quantities and the environmental impact of mining or extracting these precious metals are problematic. Additionally, the stability or activity of currently known catalyst materials for water electrolysis is not always sufficient. In particular, catalyst materials containing transition metals exhibit low activity, making water electrolysis with these materials uneconomical. Especially with low catalyst activity, high overvoltages are required for electrolysis. Accordingly, there is a need to improve the efficiency of water electrolysis.

[0007] Nickel is a well-known catalyst material for alkaline water electrolysis. Nickel-iron catalyst materials are also well-known for water electrolysis. However, the stability of these catalyst materials, particularly with reversible currents that occur after the electrolyzer is switched off, often leads to a deterioration in their activity.

[0008] Based on this, the object of the invention is to improve water electrolysis and in particular to provide catalyst materials and / or catalysts with high activity and stability at low cost.

[0009] The problem is solved according to the invention by the features of the independent claims. Preferred embodiments of the invention are specified in the dependent claims, each of which, individually or in combination, can represent an aspect of the invention.

[0010] This problem is solved by a catalyst material for water electrolysis, wherein the catalyst material comprises nickel, iron and cobalt, and wherein a) the catalyst material has a nickel content between 48 atomic% and 74 atomic%, an iron content between 13 atomic% and 26 atomic%, and a cobalt content between 13 atomic% and 26 atomic%, each based on the total number of atoms of the sum of nickel, iron and cobalt, or b) the catalyst material has a cobalt content between 48 atomic % and 74 atomic %, an iron content between 13 atomic % and 26 atomic %, and a nickel content between 13 atomic % and 26 atomic %, each based on the total number of atoms of the sum of nickel, iron and cobalt.

[0011] Furthermore, the task is solved by a catalyst comprising the above catalyst material.

[0012] Furthermore, the problem is solved by using the above catalyst material in water electrolysis. The problem is also solved by using the above catalyst in water electrolysis.

[0013] In this context, "catalyst material" preferably refers to the catalytically active material of the anode or cathode of an electrolysis cell or electrolyzer for water electrolysis. The catalyst material can preferably be used as the catalytically active material of the cathode in the hydrogen evolution reaction (HER). Furthermore, the catalyst material can preferably be used as the catalytically active material of the anode in the oxygen evolution reaction (OER).

[0014] The catalyst material according to the invention comprises the materials nickel, iron, and cobalt, which makes the catalyst material and the catalyst comprising the catalyst material particularly cost-effective compared to precious metal-based catalyst materials. The catalyst material has been shown to exhibit high stability.

[0015] The catalyst material is suitable for both alkaline and acidic water electrolysis in a membrane-electrode array (AEM) in anion exchange membrane (AEM) water electrolysis. It can also be used in the standard alkaline water electrolysis configuration. The catalyst material is particularly well-suited for alkaline water electrolysis using a 0.2 M to 9 M KOH solution as the electrolyte.

[0016] The catalyst material can contain elements other than nickel, iron, and cobalt. Alternatively, the catalyst material can consist solely of nickel, iron, and cobalt – meaning it contains no other elements.

[0017] In a first variant of the catalyst material, the nickel content is comparatively high, between 48 atomic% and 74 atomic%, based on the total number of atoms of the sum of nickel, iron and cobalt, and the proportions of iron and cobalt are comparatively low, between 13 atomic% and 26 atomic%, based on the total number of atoms of the sum of nickel, iron and cobalt.

[0018] In a second variant of the catalyst material, the cobalt content is comparatively high, between 48 atomic% and 74 atomic%, based on the total number of atoms of the sum of nickel, iron and cobalt, and the proportions of nickel and iron are comparatively low, between 13 atomic% and 26 atomic%, based on the total number of atoms of the sum of nickel, iron and cobalt.

[0019] The catalyst material of the first variant is preferably designed with a high nickel content. The first variant exhibits particularly high activity in the hydrogen evolution reaction and the oxygen evolution reaction.

[0020] The nickel, iron, and cobalt are preferably present in the catalyst material as elemental metals – that is, in oxidation state 0. In other words, the nickel, iron, and cobalt are preferably not present as metal salts or metal oxides in the catalyst material.

[0021] The atomic percentages mentioned above refer to the sum of nickel, iron, and cobalt in the catalyst material. If the catalyst material contains no other elements, i.e., consists only of nickel, iron, and cobalt, the stated atomic percentages also correspond to the atomic percentages of the catalyst material itself.

[0022] As already mentioned, the catalyst material in the first variant has a high nickel content. In this context, a preferred embodiment of the invention provides that the nickel content is between 50 atomic percent and 70 atomic percent, based on the total number of atoms of nickel, iron, and cobalt. It is further preferred that the nickel content is between 57 atomic percent and 70 atomic percent, and particularly preferably between 58 atomic percent and 63 atomic percent, based on the total number of atoms of nickel, iron, and cobalt. It has been found that the catalyst material is very active in this composition range, so that only very low overpotentials are required for alkaline water electrolysis, both when used as an anode and a cathode.

[0023] In relation to the first variant, according to a further preferred embodiment of the invention, the iron content is between 15 atomic % and 25 atomic %, and more preferably between 15 atomic % and 20 atomic %, based on the total number of atoms of the sum of nickel, iron and cobalt.

[0024] In a preferred embodiment, the catalyst material has, for example, a nickel content of between 50 and 70 atomic percent, an iron content of between 15 and 25 atomic percent, and a cobalt content of between 15 and 25 atomic percent, based on the total number of atoms of nickel, iron, and cobalt. In a further preferred embodiment, the catalyst material has, for example, a nickel content of between 57 and 70 atomic percent, an iron content of between 15 and 20 atomic percent, and a cobalt content of between 13 and 22 atomic percent, based on the total number of atoms of nickel, iron, and cobalt.

[0025] In a preferred embodiment, the catalyst material has, for example, a nickel content of 58 atomic percent, an iron content of 25 atomic percent, and a cobalt content of 17 atomic percent, based on the total number of atoms of nickel, iron, and cobalt. A nickel foam electrode modified with this exemplary catalyst material exhibits overpotentials of 370 mV and 390 mV at 0.5 A / cm². 2 and 1 A / cm 2 The oxygen evolution reaction (OER) was measured in a model electrolyzer with an AEM membrane and 1 M KOH at an operating temperature of 20 °C. The overpotential remained stable even after 3 hours of stepwise galvanostatic operation.

[0026] Further preferably, the catalyst material has, for example, a nickel content of 63 atomic percent, an iron content of 25 atomic percent, and a cobalt content of 13 atomic percent, based on the total number of atoms of the sum of nickel, iron and cobalt.

[0027] As already mentioned, the catalyst material in the second variant has a high cobalt content. In this context, a preferred embodiment of the invention provides that the nickel content is between 16 atomic percent and 21 atomic percent, based on the total number of atoms of nickel, iron, and cobalt. Alternatively or additionally, the second variant may provide that the iron content is between 20 atomic percent and 26 atomic percent, based on the total number of atoms of nickel, iron, and cobalt. A further alternative or additionally, the second variant may provide that the cobalt content is between 50 atomic percent and 60 atomic percent, based on the total number of atoms of nickel, iron, and cobalt. It has been shown that the catalyst material is particularly active in the oxygen evolution reaction within this composition range.

[0028] In a preferred embodiment, the catalyst material has, for example, a nickel content between 16 atomic % and 21 atomic %, an iron content between 20 atomic % and 26 atomic %, and a cobalt content between 50 atomic % and 60 atomic %, based on the total number of atoms of the sum of nickel, iron and cobalt.

[0029] According to a further preferred embodiment of the invention, in relation to the first variant – i.e., the variant with a high nickel content – ​​the atomic ratio of iron to cobalt is in the range of 0.8:1.2 to 1.2:0.8 and preferably in the range of 0.9:1.1 to 1.1:0.9. A 1:1 atomic ratio of iron to cobalt is particularly preferred.

[0030] According to a further preferred embodiment of the invention, with regard to the second variant – i.e., the variant with a high cobalt content – ​​the atomic ratio of iron to nickel is in the range of 0.8:1.2 to 1.2:0.8 and preferably in the range of 0.9:1.1 to 1.1:0.9. A 1:1 atomic ratio of iron to nickel is particularly preferred.

[0031] According to a further preferred embodiment of the invention, the catalyst material comprises less than 1 atomic percent precious metals. In other words, the catalyst material is essentially free of precious metals. This makes the catalyst material cost-effective. For the purposes of this invention, precious metals are understood to be the classic precious metals ruthenium, rhodium, palladium, silver, osmium, iridium, platinum, gold, and mercury.

[0032] As already mentioned, the catalyst material can comprise elements other than nickel, iron, and cobalt. In this context, according to a further preferred embodiment of the invention, the catalyst material comprises up to 25 atomic percent of other metals, based on the total number of atoms of the catalyst material. In other words, at least 75 atomic percent of the catalyst material consists of nickel, iron, and cobalt.

[0033] With regard to the other metals, according to a further preferred embodiment of the invention, the other metals include aluminium, tantalum, chromium, manganese, titanium, vanadium, molybdenum, yttrium, zirconium, niobium, copper, zinc, tin and / or mixtures thereof.

[0034] According to a further preferred embodiment of the invention, the catalyst material consists essentially of nickel, iron, and cobalt. The catalyst material is therefore preferably a ternary material system, with further components present in the catalyst material at less than 1 atomic percent. It is particularly preferred that the catalyst material comprises less than 1 atomic percent of further components selected from platinum, sulfur, and / or molybdenum(IV) sulfide.

[0035] According to a further preferred embodiment of the invention, the catalyst material is designed as an alloy. For the purposes of this invention, an alloy is preferably understood to be a macroscopically homogeneous metallic material consisting of more than one element, wherein at least one of the several elements is a metal and wherein the several elements of the catalyst material jointly exhibit the typical metallic characteristic of metallic bonding.

[0036] As already mentioned, the invention also relates to the catalyst, comprising the catalyst material described above. In this context, a preferred embodiment of the invention provides that the catalyst is configured as an electrode. The electrode can be a cathode or an anode, preferably of an electrolyzer for water electrolysis. The electrode is preferably electrically conductive.

[0037] According to a preferred embodiment of the invention, the catalyst material is applied as a coating to a conductive support. The support is preferably porous. Alternatively and / or additionally, the support can be configured as a foam, a mesh, a sheet with holes, expanded metal, a metal mesh, and / or a nonwoven fabric. It is further preferred that the catalyst material forms the electrode. It is also further preferred that the catalyst and / or the catalyst material is configured as a sheet, wire, foam, a mesh, a sheet with holes, expanded metal, a metal mesh, and / or a nonwoven fabric.

[0038] With regard to the support material, it may be provided that the support material comprises nickel, titanium, stainless steel, and / or carbon. More preferably, it may be provided that the support material consists of nickel, titanium, stainless steel, and / or carbon. For example, the support material is nickel foam. Nickel foam is a cost-effective and readily available support material that makes water electrolysis economically viable.

[0039] The catalyst and / or the electrode can be produced in different ways. For example, the support can be coated with the catalyst material from a solution using electroplating and / or electrodeposition.

[0040] Alternatively, the support can be coated with the catalyst material by sputtering. Furthermore, it is possible to coat the support with the catalyst material, which is in powder or wire form, by plasma spraying and / or direct energy deposition.

[0041] Furthermore, it is possible and preferably intended that the catalyst and / or the electrode are produced from the catalyst material by melting. In this case, the catalyst material preferably forms the catalyst or the electrode. For example, a sheet can be metallurgically produced from the catalyst material and this can be further processed into a sheet with holes or into expanded metal.

[0042] Alternatively, a wire can be metallurgically produced from the catalyst material and further processed into a mesh or metal mesh.

[0043] According to a particularly preferred embodiment of the invention, the catalyst and / or the catalyst material is produced by a melting process. The preferably metallurgical melting process makes the production of the catalyst material and / or the catalyst particularly simple. In particular, complex process steps can be dispensed with. It is especially preferred that the catalyst and / or the catalyst material is not produced by precipitation from a solution.

[0044] The technical characteristics and advantages of the catalyst are evident to a person skilled in the art from the description of the catalyst material.

[0045] The invention further relates to the use of the previously described catalyst material, or the use of the previously described catalyst, in water electrolysis. The water electrolysis can be acidic, alkaline, PEM, or AEM. Preferably, the catalyst material and / or the catalyst is used in alkaline water electrolysis. In alkaline water electrolysis, 0.2 M to 9 M KOH solutions are preferably used as the electrolyte solution.

[0046] A nickel foam electrode modified with the catalyst material exhibits overpotentials of 370 mV and 390 mV at 0.5 A / cm². 2 and 1 A / cm 2The oxygen evolution reaction (OER) was carried out in a model electrolyzer with an AEM membrane and 1 M KOH at an operating temperature of 20 °C. The overpotential remained stable even after 3 h of stepwise galvanostatic operation. The catalyst material comprises or consists of elements that are readily available, technically easy to process, and inexpensive. Furthermore, a small proportion of the iron in the catalyst material can dissolve in the electrolyte, which is particularly advantageous for the efficiency of alkaline water electrolysis.

[0047] The person skilled in the art will derive further technical aspects and advantages of the use of the catalyst material and / or the use of the catalyst from the above description of the catalyst material and / or the catalyst.

[0048] The invention is explained below by way of example with reference to the accompanying drawings and preferred embodiments, wherein the features shown below can represent an aspect of the invention, either individually or in combination. The drawings show: Fig. 1 Results of a high-throughput screening for the oxygen evolution reaction for catalyst materials according to preferred embodiments of the invention and compared with reference catalyst materials, Fig. 2 further results of the high-throughput screening for catalyst materials according to preferred embodiments of the invention and compared with reference catalyst materials, Fig. 3 enlarged sections of the data from Fig. 2, Fig. 4 results for the in Fig. 3 data shown, Fig. 5 SEM images and element distribution of a galvanically coated electrode according to a preferred embodiment of the invention, Fig. 6. Measurement setup for electrolysis experiments with the electrode as anode made of Fig. 5, Fig. 7 Current-voltage diagram for the measurement setup recorded using linear sweep voltammetry (LSV). Fig. 6 as a 3-electrode setup before and after 3 h chronopoteniometric electrolysis at different current levels 0.05 A / cm 2 A / cm 2 - 3 A / cm 2 , Fig. 8 results of a 30 h stability test of the electrode with the measurement setup from Fig. 6 as a 2-electrode setup, Fig. 9 Current-voltage diagram recorded using linear sweep voltammetry (LSV) for the measurement setup Fig. 6 as a 2-electrode setup before the stability test, after a first switch-off after 24 h and after a second switch-off after 30 h, Fig. 10 Concentration of dissolved metals nickel, iron and cobalt in the electrolyte during the stability test of the electrode with the measuring setup made of Fig. 6, Fig. 11 Results of electrolysis experiments obtained by stepwise chronopotentiometry at different current densities for the measurement setup from Fig. 6 as a 3-electrode setup and for a comparison electrode, Fig. 12 Current-voltage diagrams for the measurement setup, recorded using voltammetry and normalized to the electrochemically active surface. Fig. 6 and for a comparison electrode, and

[0049] Fig. Figure 1 shows results of a high-throughput screening of the oxygen evolution reaction for catalyst materials according to preferred embodiments of the invention and compared with reference catalyst materials. Thin films of iron (Fe), cobalt (Co), and nickel (Ni) with different chemical compositions were produced by sputtering. The thin films were measured using linear sweep voltammetry (LSV) to record current-voltage diagrams in a relevant potential range. Ternary diagram 10 shows the electrolysis current during the oxygen evolution reaction at a potential of 1600 mV as a function of the chemical composition of the ternary catalyst material. In the high-throughput screening, the catalyst material consists of the elements nickel, iron, and cobalt.Circle 12 designates a range where the catalyst material has a nickel content between 48 atomic% and 74 atomic%, an iron content between 13 atomic% and 26 atomic%, and a cobalt content between 13 atomic% and 26 atomic%, based on the total number of atoms of the catalyst material.

[0050] Circle 14 designates an area with a reference catalyst material, wherein the reference catalyst material has a nickel content of 41 atomic%, an iron content of 17 atomic% and a cobalt content of 42 atomic%, based on the total number of atoms of the catalyst material.

[0051] Fig. Figure 2 shows further results of the high-throughput screening. The Y-axis (16) shows the electrolysis current in µA for the oxygen evolution reaction at a potential of 1600 mV. The X-axis (18) shows the overpotential for the hydrogen evolution reaction in mV. Each data point (20) corresponds to a catalyst material with a specific composition. Two composition clusters can be identified, whereby Fig. 3 enlarged sections of the two composition clusters from Fig. 2 shows.

[0052] In Fig. In section 3, five data points (20) are highlighted with numbers, whose current-voltage diagrams are shown in Fig. Figure 4 shows the composition of the catalyst materials highlighted with numbers. Nummer Kobaltanteil in Atom-% Eisenanteil in Atom-% Nickelanteil in Atom-% 20' 13 20 66 21' 13 18 68 23' 14 14 70 35' 16 18 65 68' 22 19 57 268' 52 26 21 286' 55 26 18 303' 58 24 16 304' 59 22 17 305' 60 20 19

[0053] Fig. Figure 4 shows the electrolysis current in µA on the Y-axis (22) as a function of the potential in mV shown on the X-axis (24). The two composition clusters differ in their proportions: One cluster, comprising data points 20 with numbers 20', 21', 23', 35', and 68', is rich in nickel, with a nickel content of 57 to 70 atomic percent. The other cluster, comprising data points 20 with numbers 268', 286', 303', 304', and 305', is rich in cobalt, with a cobalt content of 50 to 60 atomic percent. While both clusters show similar performance in the oxygen evolution reaction, the nickel-rich cluster exhibits high activity in both the oxygen evolution and hydrogen evolution reactions.

[0054] Fig. Figure 5 schematically shows SEM imaging ( Fig. 5 (a), (b), (c) and (d)) and element distribution ( Fig. 5 (e), (f) and (g)) of an electroplated electrode according to a preferred embodiment of the invention. The electrode was produced by electroplating layers onto nickel foam.

[0055] Fig. Figure 6 schematically shows a measurement setup 26 for electrolysis experiments with the electrode made of Fig. 5 as the anode. This is evident in Fig. 6, that the measuring setup 26 comprises a flow electrolyzer in a membrane electrode arrangement (MEA) configuration. An anion exchange membrane 32 is positioned between the anode 28 and the cathode 30. An electrolyte 34 – in this case 1 M KOH – is supplied to the individual half-cells by two peristaltic pumps 36. The measuring setup 26 can be operated as a 2-electrode setup, in which case the anode 28 forms the working electrode at a positive cell voltage. The measuring setup 26 can also be operated as a 3-electrode setup via the connection 68 for a reference electrode, in which case, during the oxygen evolution reaction in the 3-electrode setup, the anode 28 forms the working electrode at a positive voltage.

[0056] Fig. Figure 7 schematically shows a current-voltage diagram 38 recorded by linear sweep voltammetry (LSV) for the measurement setup 26. Fig. 6 as a 3-electrode setup, with data 40 before and data 42 after 3 h chronopotentiometric electrolysis at 1 A / cm² 2 The Y-axis 44 in Fig. Figure 7 shows the electrolysis current normalized to the geometric electrode surface area in A / cm². 2 as a function of the potential shown on the x-axis 46 relative to a reference electrode in V. To correct the potential for the ohmic voltage drop, the ohmic resistance between the working and reference electrodes is measured. The electrode made of Fig. 5 as an anode shows overpotentials of 370 mV and 390 mV at 0.5 A / cm² 2 and 1 A / cm 2 The oxygen evolution reaction (OER) was measured at an operating temperature of 20 °C. The overpotential remained stable after 3 hours of stepwise galvanostatic operation.

[0057] Fig. Figure 8 shows the results of a 30-hour stability test of the electrode using the measurement setup 26. Fig. 6 as a 2-electrode setup, wherein in Fig. The potential on the Y-axis (48) is corrected to 90% of the ohmic voltage drop in V, and the X-axis (50) represents time in hours. Arrow 51 indicates the time the measurement setup (26) was switched off.

[0058] To correct the potential for the ohmic voltage drop, the ohmic resistance between the working and counter electrodes is measured.

[0059] Fig. Figure 9 schematically shows a current-voltage diagram 52 recorded by linear sweep voltammetry (LSV) for the measurement setup 26. Fig. 6 as a 2-electrode setup with data 54 before the stability test, data 56 after a first shutdown after 24 h and data 58 after a second shutdown after 30 h. The Y-axis 60 in Fig. Figure 9 shows the electrolysis current normalized to the electrode surface in A / cm². 2as a function of the potential in V, corrected by 90% of the ohmic voltage drop and plotted on the x-axis 62. The ohmic resistance between the working and counter electrodes is measured to correct the potential for the ohmic voltage drop.

[0060] Fig. Figure 10 schematically shows the concentration of dissolved metals in the electrolyte during the stability test of the electrode with the measuring setup from Fig. 6. The Y-axis (64) shows the concentration in µmol / L of the dissolved metals, and the X-axis (50) shows the time in hours. The leaching of the catalyst material during electrolysis was investigated using inductively coupled plasma mass spectrometry (ICP-MS). The data show that initially a certain concentration of iron (Fe) dissolves, but the amount of dissolved iron remains stable over a period of 30 hours. Accordingly, the electrode is stable under the chosen conditions. A certain concentration of iron in the electrolyte can also increase the efficiency of alkaline electrolysis.

[0061] Fig. Figure 11 shows further results from electrolysis experiments for the measurement setup 26. Fig. Figure 6 shows a 3-electrode setup and a reference electrode, which were used for stepwise chronopotentiometry at different current densities. The Y-axis (70) shows the potential corrected for 80% of the ohmic voltage drop relative to the reference electrode in V, while the X-axis (72) shows the current density in mA / cm². 2 The data show that catalyst material 66, with a nickel content of 58 atomic percent, an iron content of 25 atomic percent, and a cobalt content of 17 atomic percent, exhibits a lower overpotential compared to the reference catalyst materials 74 and 76, based on the total number of atoms of the catalyst material.

[0062] The comparison catalyst materials 74 and 76 have a nickel content of 33 atomic percent, an iron content of 33 atomic percent, and a cobalt content of 33 atomic percent, respectively. The comparison catalyst material 76 has a composition that is within the range specified in Fig. 1 lies within the area represented by circle 14.

[0063] Fig. Figure 12 shows the current-voltage diagram 78 of the catalyst material 66, recorded by voltammetry and normalized to the electrochemically active surface, with data points 66a before and 66b after the stepwise chronopotentiometry. Data for the reference catalyst materials 74 and 76 are also shown for comparison. The y-axis 80 shows the current density in mA / cm². 2The x-axis 82 shows the potential corrected by 80% of the ohmic voltage drop relative to the reference electrode in V. The data show that the catalyst material 66, with a nickel content of 58 atomic%, an iron content of 25 atomic%, and a cobalt content of 17 atomic%, exhibits a lower overpotential compared to the reference catalyst materials 74 and 76 before and after chronopotentiometry (data points 66a) and after chronopotentiometry (data points 66b).

[0064] The invention originates from a funded research project within the framework of the EXIST research transfer grant number FKZ 03EFTNW306. Reference sign 10 ternary diagram 12 Area with catalyst material according to preferred embodiment 14 Area with comparison catalyst material 16 Y-axis; Electrolysis current in µA during the oxygen evolution reaction at a potential of 1600 mV 18 X-axis; Overpotential in the hydrogen evolution reaction in mV 20 data points 22 Y-axis; electrolysis current in µA 24 Potential in mV 26 Measurement setup 28 Anode 30 Cathode 32 anion exchange membrane 34 Electrolyte 36 Hose pump 38 Current-Voltage Diagram 40 data points prior to chronopotentiometric electrolysis 42 data points after chronopotentiometric electrolysis 44 Y-axis; Electrolysis current standardized to geometric electrode surface area in A / cm² 2 46 X-axis; potential relative to the reference electrode in V 48 Y-axis; potential in V corrected to 90% of the ohmic voltage drop 50 X-axis; time in h 51 Arrow 52 Current-Voltage Diagram 54 data points before the stability test 56 data points after an initial shutdown after 24 hours 58 data points after a second shutdown after 30 hours 60 Y-axis; electrolysis current standardized on electrode surface in A / cm² 2 62 X-axis; potential in V corrected to 90% of the ohmic voltage drop 64 Y-axis; Concentration of dissolved metals in µmol / L 66 Catalyst material Co 17 Ni 58 Fe 25 68 Connection for reference electrode; 70 Y-axis; potential corrected to 80% of the ohmic voltage drop relative to the reference electrode in V 72 X-axis; current density in mA / cm² 2 74 Comparison catalyst material Co 33 Ni 33 Fe 33 76 Comparison catalyst material Co 42 Ni 41 Fe 17 78 Current-voltage diagram normalized to the electrochemically active surface 80 Y-axis; current density in mA / cm²2 82 X-axis; potential corrected to 80% of the ohmic voltage drop relative to the reference electrode in V

Claims

[1] Catalyst material for water electrolysis, wherein the catalyst material comprises nickel, iron and cobalt, and wherein a) the catalyst material has a nickel content between 48 atomic% and 74 atomic%, an iron content between 13 atomic% and 26 atomic%, and a cobalt content between 13 atomic% and 26 atomic%, each based on the total number of atoms of the sum of nickel, iron and cobalt, or b) the catalyst material has a cobalt content between 48 atomic % and 74 atomic %, an iron content between 13 atomic % and 26 atomic %, and a nickel content between 13 atomic % and 26 atomic %, each based on the total number of atoms of the sum of nickel, iron and cobalt. [2] Catalyst material according to claim 1, wherein the catalyst material is designed according to feature a) and wherein the nickel content is between 50 atomic % and 70 atomic %, preferably between 57 atomic % and 70 atomic %, and particularly preferably between 58 atomic % and 63 atomic %, based on the total number of atoms of the sum of nickel, iron and cobalt. [3] Catalyst material according to claim 1 or 2, wherein the catalyst material is designed according to feature a) and wherein the iron content is between 15 atomic % and 25 atomic %, preferably between 15 atomic % and 20 atomic %, based on the total number of atoms of the sum of nickel, iron and cobalt. [4] Catalyst material according to any of the preceding claims, wherein the catalyst material is designed according to feature b) and wherein the nickel content is between 16 atomic % and 21 atomic %, the iron content is between 20 atomic % and 26 atomic %, and / or the cobalt content is between 50 atomic % and 60 atomic %, in each case based on the total number of atoms of the sum of nickel, iron and cobalt. [5] Catalyst material according to one of the preceding claims, wherein the catalyst material is configured according to feature a) and the atomic ratio of iron and cobalt to each other is in the range of 0.8:1.2 to 1.2:0.8 and preferably 1:1, or wherein the catalyst material is configured according to feature b) and the atomic ratio of iron and nickel to each other is in the range of 0.8:1.2 to 1.2:0.8 and preferably 1:

1. [6] Catalyst material according to any of the preceding claims, wherein the catalyst material comprises less than 1 atomic % precious metals. [7] Catalyst material according to any of the preceding claims, wherein the catalyst material comprises up to 25 atomic % of further metals, based on the total number of atoms of the catalyst material. [8] Catalyst material according to claim 7, wherein the further metals comprise aluminium, tantalum, chromium, manganese, titanium, vanadium, molybdenum, yttrium, zirconium, niobium, copper, zinc, tin and / or mixtures thereof. [9] Catalyst material according to any one of claims 1 to 6, wherein the catalyst material consists essentially of nickel, iron and cobalt and / or comprises less than 1 atomic % of further components selected from platinum, sulfur and / or molybdenum(IV) sulfide. [10] Catalyst material according to any of the preceding claims, wherein the catalyst material is designed as an alloy. [11] Catalyst comprising the catalyst material according to any one of claims 1 to 10. [12] Catalyst according to claim 11, wherein a) wherein the catalyst is designed as an electrode, and / or b) wherein the catalyst material is applied as a coating on a conductive support, and / or c) wherein the catalyst and / or catalyst material is designed as sheet metal, wire, foam, mesh, perforated sheet metal, expanded metal, metal mesh and / or nonwoven fabric. [13] Catalyst according to claim 11 or 12 or catalyst material according to any one of claims 1 to 10, wherein the catalyst and / or the catalyst material is produced by a melting process and / or wherein the catalyst and / or the catalyst material is not produced by precipitation from a solution. [14] Use of a catalyst material according to any one of claims 1 to 10 or 13, or use of the catalyst according to claims 11 to 13 in water electrolysis, in particular alkaline water electrolysis with 0.2 M to 9 M KOH solution as electrolyte.

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