A self-supporting ni-fe-mn oxygen evolution electrocatalyst and a preparation method thereof

Abstract

The application provides a self-supporting Ni-Fe-Mn oxygen evolution electrocatalyst and a preparation method thereof, and belongs to the technical field of catalytic material preparation. The Ni, Fe and Mn metal raw materials are repeatedly smelted, and after smelting, suction casting is carried out to obtain a cast plate. The cast plate is subjected to homogenization treatment, and then is cut and polished. Finally, etching is carried out in a nitric acid solution to obtain the self-supporting Ni-Fe-Mn oxygen evolution electrocatalyst. The self-supporting electrocatalyst is prepared by the method of arc smelting, heat treatment and chemical etching, and has the advantages of simple preparation process, easy industrialization, adjustable size, excellent stability and excellent OER performance.

Description

Technical Field

[0001] This invention relates to the field of catalytic material preparation technology, and in particular to a self-supporting Ni-Fe-Mn oxygen evolution electrocatalyst and its preparation method. Background Technology

[0002] In recent years, the overexploitation and use of traditional fossil fuels have led to a severe energy crisis and environmental pollution. Therefore, finding pollution-free and sustainable new energy sources to replace fossil fuels is urgently needed. Hydrogen energy, due to its high specific energy density (142 MJ / kg), high conversion efficiency, and environmentally friendly combustion products, is considered one of the most promising new energy sources to replace fossil fuels, and is expected to replace them to the greatest extent possible. Water electrolysis, as a pollution-free and sustainable hydrogen production technology, has great development prospects. However, water electrolysis for hydrogen production still needs to overcome some electrochemical technical bottlenecks. Water electrolysis involves two half-reactions: the oxygen evolution reaction (OER) at the anolyte and the hydrogen evolution reaction (HER) at the catholyte. The OER, involving a four-electron process, has a slower kinetic rate compared to the two-electron process of HER, and typically exhibits a larger overpotential, hindering the entire water electrolysis process. Therefore, finding efficient and stable OER electrocatalysts is key to the industrial application of water electrolysis for hydrogen production technology and an important prerequisite for the industrial application of hydrogen energy.

[0003] Powdered electrocatalysts attached to external electrodes using polymer binders suffer from drawbacks such as easy agglomeration and detachment, and are not suitable for large-scale industrial production. In contrast, self-supported electrodes with in-situ growth of nanocatalyst materials on highly conductive substrates exhibit more structural advantages, mainly in the following two aspects: First, the in-situ growth of nanocatalysts on the substrate avoids the coating process and the addition of binders, thus simplifying the electrode preparation process and significantly reducing costs; Second, the catalyst material and the substrate are tightly connected, and no polymer binder is needed to maintain electrical contact, ensuring rapid charge transfer, reducing agglomeration, exposing more catalytic sites, and preventing catalyst detachment during long-term cycling or high-current operation. Commercial noble metal-based catalysts exhibit excellent performance, but their high cost and scarce resources hinder large-scale industrial use. In recent years, transition metal compounds, especially nickel-iron-based transition metal compounds, have been widely studied as OER catalysts due to their low cost and theoretically high activity. However, the catalytic activity and stability of nickel-iron-based transition metal compounds still lag significantly behind noble metal catalysts, especially under high current conditions, requiring further improvement.

[0004] Numerous studies have shown that strategies such as element doping (e.g., Mn) and the construction of nanostructures can effectively enhance electrocatalytic performance. Therefore, developing large-size, self-supporting nickel-iron-based electrocatalysts that maintain excellent catalytic activity and stability under high current is crucial for industrialization. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a self-supporting Ni-Fe-Mn oxygen evolution electrocatalyst and its preparation method. The preparation method provided by this invention is simple, and the electrocatalyst has excellent electrocatalytic activity and stability.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing a self-supporting Ni-Fe-Mn oxygen evolution electrocatalyst, wherein Ni, Fe, and Mn metal raw materials are repeatedly smelted, and after smelting, they are suction-cast to obtain a cast plate. The cast plate is then homogenized, cut, and polished, and finally etched in a nitric acid solution to obtain the final product.

[0007] Preferably, the preparation method specifically includes the following steps:

[0008] (1) Prepare the Ni, Fe and Mn metal raw materials;

[0009] (2) Place the weighed raw materials into the crucible of the vacuum non-consumable electric arc melting furnace and circulate the gas for washing 3 to 5 times.

[0010] (3) After the arc is started, adjust the arc current to 200-250A to melt the titanium ingot to remove the residual oxygen. Then adjust the current to 250-300A to melt the alloy in the crucible. Repeat the melting process 3-5 times.

[0011] (4) Transfer the alloy ingot after melting to a suction casting crucible for suction casting. The arc current is 250-300A. After the alloy ingot is completely melted, turn on the suction casting switch to perform suction casting. After the suction casting is completed, NiFeMn as-cast plate is obtained.

[0012] (5) The NiFeMn as-cast plate obtained in step (4) is sealed using a sealing machine, and then the NiFeMn plate in vacuum after sealing is homogenized. After the homogenization process is completed, it is water-quenched to obtain the target plate.

[0013] (6) After cutting and polishing the target plate obtained in step (5), it is etched in nitric acid solution to obtain the self-supported Ni-Fe-Mn oxygen evolution electrocatalyst.

[0014] More preferably, in step (1), the ingredients are prepared according to a total mass fraction of 45 to 55 parts of Ni, Fe and Mn, wherein the Mn content is 10 to 50% of the total raw material, and the remainder is Ni and Fe, with a mass ratio of Ni to Fe of (2 to 3):(3 to 5).

[0015] More preferably, the specific operation of the circulating gas washing in step (2) is as follows: the vacuum non-consumable arc melting furnace is evacuated to 6×10 -4 ~8×10 -4 Below Pa, purge with argon gas to -0.01 to -0.05 MPa, and repeat this step.

[0016] More preferably, the melting time in step (3) is 1 to 2 minutes.

[0017] More preferably, the homogenization temperature in step (5) is 1173–1373 K, and the homogenization time is 22–26 h.

[0018] More preferably, the nitric acid solution in step (6) is prepared by mixing concentrated nitric acid, water and anhydrous ethanol in a volume ratio of (1-2):(4-4.5):(4-4.5).

[0019] Preferably, step (1) further includes pretreatment of Ni, Fe, and Mn metal raw materials before batching.

[0020] More preferably, the pretreatment is as follows: the Ni and Fe metal raw materials are removed from the metal surface oxide layer and impurities by mechanical grinding, the metal Mn is removed from the surface oxide layer by a mixed solution of concentrated nitric acid, hydrofluoric acid and water, after cleaning, it is placed in anhydrous ethanol for ultrasonication, and after ultrasonication, it is dried for later use.

[0021] The present invention also provides a self-supporting Ni-Fe-Mn oxygen evolution electrocatalyst prepared by the preparation method described in the above technical solution.

[0022] Beneficial technical effects:

[0023] 1. This invention uses an electric arc melting + heat treatment + chemical etching method to prepare a self-supporting electrocatalyst. This method is not only simple to operate, but also produces products with high purity, adjustable product size, and easy-to-control morphology, making it suitable for large-scale industrial production.

[0024] 2. The supported Ni-Fe-Mn oxygen evolution electrocatalyst provided by this invention has a unique structure. A large number of structurally stable conical nano-amorphous structures exist on the surface of nickel-iron-manganese metal, exhibiting excellent catalytic activity. Furthermore, the nickel-iron-based catalyst has a low overpotential. By doping with manganese to form a ternary alloy, the electronic structure of the catalyst can be further optimized, improving the catalytic activity. In addition, the self-supporting nano-metal structure composed of interlocking nanocones is beneficial to the improvement of material stability, exhibiting excellent electrochemical stability.

[0025] 3. This invention can prepare self-supported Ni-Fe-Mn oxygen evolution electrocatalysts of various sizes, exhibiting excellent OER catalytic performance: at 10 mA / cm²... 2 At a current density of 100 mA / cm², its oxygen evolution overpotential is 191 mV. 2 At a current density of 282mV, its oxygen evolution overpotential is 282mV, and at 500mA / cm 2 At a current density of 500 mA / cm², its oxygen evolution overpotential is 323 mV, exhibiting excellent electrochemical oxygen evolution catalytic activity; this electrocatalyst exhibits excellent electrochemical oxygen evolution catalytic activity at 500 mA / cm². 2 After a 100-hour stability test under constant current, the potential only decreased slightly, indicating that it still has excellent catalytic stability under high current. Attached Figure Description

[0026] Figure 1 The XRD pattern of the self-supporting Ni-Fe-Mn oxygen evolution electrocatalyst prepared in Example 1 is shown below.

[0027] Figure 2 The image shows the SEM image of the self-supporting Ni-Fe-Mn oxygen evolution electrocatalyst prepared in Example 1.

[0028] Figure 3 The TEM image of the self-supporting Ni-Fe-Mn oxygen evolution electrocatalyst prepared in Example 1 is shown below.

[0029] Figure 4 The LSV oxygen evolution performance curve of the self-supported Ni-Fe-Mn oxygen evolution electrocatalyst prepared in Example 1 is shown.

[0030] Figure 5 The stability curve of the self-supported Ni-Fe-Mn oxygen evolution electrocatalyst prepared in Example 1 is shown. Detailed Implementation

[0031] This invention provides a method for preparing a self-supporting Ni-Fe-Mn oxygen evolution electrocatalyst. The method involves repeatedly melting Ni, Fe, and Mn metal raw materials, followed by suction casting to obtain a cast plate after melting. The cast plate is then homogenized, cut, and polished, and finally etched in a nitric acid solution to obtain the final product.

[0032] In this invention, the preparation method specifically includes the following steps:

[0033] (1) The Ni and Fe metal raw materials are mechanically polished to remove the oxide layer and impurities on the metal surface. The Mn metal is cleaned by a mixed solution of concentrated nitric acid, hydrofluoric acid and water to remove the oxide layer on the surface. After cleaning, it is placed in anhydrous ethanol for ultrasonication. After ultrasonication, it is dried. The processed Ni, Fe and Mn metal raw materials are batched according to a total mass ratio of 45 to 55 parts of Ni, Fe and Mn, wherein the Mn content is 10 to 50% of the total raw material, and the remainder is Ni and Fe. The mass ratio of Ni to Fe is (2 to 3): (3 to 5). In this invention, the total mass of Ni, Fe and Mn is preferably 45-55 g. In this invention, the volume ratio of concentrated nitric acid, hydrofluoric acid and water is 20:5:75.

[0034] (2) Place the weighed raw materials into the crucible of the vacuum non-consumable arc melting furnace, and evacuate the vacuum non-consumable arc melting furnace to a vacuum level of 6×10. -4 ~8×10 -4 Below Pa, argon gas is introduced to -0.01 to -0.05 MPa, and this step is repeated, with gas purging 3 to 5 times; in this invention, the purity of the argon gas is 99.99 wt.%.

[0035] (3) After the arc is started, adjust the arc current to 200-250A and melt the titanium ingot for 1-2 minutes to remove the residual oxygen. Then adjust the current to 250-300A and melt the alloy in the crucible for 1-2 minutes. Repeat the melting process 3-5 times.

[0036] (4) Transfer the alloy ingot after melting to a suction casting crucible for suction casting. The arc current is 250-300A. After the alloy ingot is completely melted, turn on the suction casting switch to perform suction casting. After the suction casting is completed, NiFeMn as-cast plate is obtained.

[0037] (5) The NiFeMn as-cast plate obtained in step (4) is sealed using a sealing machine. The NiFeMn plate in vacuum after sealing is then homogenized at 1173-1373K for 22-26 hours. After the homogenization process is completed, it is water-quenched to obtain the target plate.

[0038] (6) After cutting and polishing the target plate obtained in step (5), it is etched in a nitric acid solution to obtain a self-supported Ni-Fe-Mn oxygen evolution electrocatalyst. In this invention, the polishing is done by grinding the surface with 240#, 800#, 1500# and 2000# sandpaper until it is bright, then rough polishing with 3.0μm polishing paste, and finally fine polishing with 1.5μm polishing paste on red velvet cloth until it is mirror-like. The nitric acid solution is prepared by mixing concentrated nitric acid, water and anhydrous ethanol in a volume ratio of (1~2):(4~4.5):(4~4.5). The concentrated nitric acid is the commonly used concentrated nitric acid in the laboratory, with a mass fraction of about 68% and a concentration of about 15.2mol / L. The etching time is 1~4h.

[0039] This invention uses nitric acid solution as the etching agent in the chemical etching reaction. By strictly controlling the reaction time, a cone-shaped amorphous nanostructure with a large active area and abundant active sites is prepared. Nitric acid plays a crucial role in the reaction; replacing it with equal amounts of hydrochloric acid or sulfuric acid solution fails to produce the cone-shaped amorphous nanostructure.

[0040] The present invention also provides a self-supporting Ni-Fe-Mn oxygen evolution electrocatalyst prepared by the preparation method described in the above technical solution.

[0041] The self-supported electrocatalysts of various sizes prepared in this invention exhibit a large number of structurally stable conical amorphous nanostructures on their nickel-iron-manganese metal surfaces, resulting in large active areas and abundant active sites, thus demonstrating excellent catalytic activity. Furthermore, the nickel-iron-based catalysts possess low overpotentials, and by doping with manganese to form ternary alloys, the electronic structure of the catalyst can be further optimized, enhancing catalytic activity. In addition, the self-supported nanostructures composed of interlocking nanocones contribute to improved material stability, exhibiting excellent electrochemical stability.

[0042] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0043] Example 1

[0044] (1) Remove the oxide layer and impurities on the surface of Ni and Fe metal raw materials by mechanical grinding. Remove the oxide layer on the surface of Mn metal by a mixed solution of nitric acid, hydrofluoric acid and water, wherein the volume ratio of nitric acid, hydrofluoric acid and water is 20:5:75. After cleaning, place it in anhydrous ethanol for ultrasonication. After ultrasonication, dry it. Then weigh 15g Ni, 20g Fe and 16g Mn.

[0045] (2) Place the weighed raw materials into the crucible of the vacuum non-consumable arc melting furnace, and evacuate the vacuum non-consumable arc melting furnace to 8×10⁻⁶. -4Below Pa, purge with 99.99 wt.% argon gas to -0.05 MPa, repeat this step, and purge the gas 3 times.

[0046] (3) After the arc is started, adjust the arc current to 200A and melt the titanium ingot for 2 minutes to remove the residual oxygen. Then adjust the current to 250A and melt the alloy in the crucible for 2 minutes. Repeat the melting process 3 times.

[0047] (4) Transfer the smelted alloy ingot to a suction casting crucible for suction casting. The arc current is 300A. After the alloy ingot is completely melted, turn on the suction casting switch to perform suction casting. After the suction casting is completed, the ingot will have dimensions of 25×6×45mm. 3 NiFeMn as-cast plate;

[0048] (5) The NiFeMn as-cast plate obtained in step (4) is sealed using a sealing machine, and then the NiFeMn plate in vacuum after sealing is homogenized at 1373K for 24h. After the homogenization treatment is completed, it is water-quenched to obtain the target plate.

[0049] (6) Cut the target sheet obtained in step (5) into 15×10×0.5mm pieces. 3 Thin sheets are ground and polished until smooth, and then etched in a nitric acid solution (nitric acid, water and alcohol are prepared in a volume ratio of 1:4.5:4.5) for 1 hour to obtain a self-supported Ni-Fe-Mn oxygen evolution electrocatalyst.

[0050] The phase composition of the final sample was determined using X-ray diffraction (XRD):

[0051] X-ray testing equipment and conditions: Rigaku D / max 2500, X-ray source: CuKα rays, λ = 0.154178 nm. Figure 1 The XRD pattern of the sample shown is from Figure 1 As can be seen, the diffraction pattern matches the PDF card 00-047-1417, proving the successful synthesis of the product.

[0052] Its morphological structure was characterized using SEM:

[0053] SEM characterization equipment: FEI Quanta 450, operating voltage 15kV. From Figure 2 It can be seen that the morphology of the sample is characterized by a large number of nanocones covering the surface of nickel-iron-manganese metal, and the interlacing structure between the nanocones is beneficial to the catalytic activity and stability of the material.

[0054] Its morphological structure was characterized using TEM.

[0055] TEM characterization equipment: JEOL JEM-2100F. From Figure 3 The sample is amorphous and has abundant active sites, which is beneficial to the catalytic activity of the material.

[0056] Test its electrocatalytic oxygen evolution activity:

[0057] Electrocatalytic oxygen evolution test conditions: The test was conducted using a Biologic SP-150 electrochemical workstation in 1M KOH solution. The prepared product was used as the working electrode, a Pt sheet as the auxiliary electrode, and a saturated calomel electrode as the reference electrode. The scan rate was 5 mV / s. The test results are shown in [Figure number missing]. Figure 4 .from Figure 4 It can be seen from 10mA / cm 2 At a current density of 100 mA / cm², its oxygen evolution overpotential is 191 mV. 2 At a current density of 282mV, its oxygen evolution overpotential is 282mV, and at 500mA / cm 2 At a current density of 323 mV, its oxygen evolution overpotential is 323 mV, exhibiting excellent electrochemical oxygen evolution catalytic activity.

[0058] Test its electrocatalytic stability:

[0059] Stability testing conditions: Stability was tested using a Biologic SP-150 electrochemical workstation via the galvanostatic method. During the test, the OER current was kept constant at 500 mA / cm². 2 As can be seen from Figure 5, when the constant current density is 500 mA / cm² 2 After a 100-hour constant current stability test, the potential only decreased slightly, indicating that the electrocatalyst still has excellent catalytic stability under high current.

[0060] The above results indicate that the material preparation method of the present invention is simple and suitable for large-scale industrial production, and the obtained self-supported Ni-Fe-Mn oxygen evolution electrocatalyst has excellent catalytic activity and stability.

[0061] Example 2

[0062] (1) Remove the oxide layer and impurities on the surface of Ni and Fe metal raw materials by mechanical grinding. Remove the oxide layer on the surface of Mn metal by a mixed solution of nitric acid, hydrofluoric acid and water, wherein the volume ratio of nitric acid, hydrofluoric acid and water is 20:5:75. After cleaning, place it in anhydrous ethanol for ultrasonication. After ultrasonication, dry it. Then weigh 18g Ni, 27g Fe and 5g Mn.

[0063] (2) Place the weighed raw materials into the crucible of the vacuum non-consumable arc melting furnace, and evacuate the vacuum non-consumable arc melting furnace to 8×10⁻⁶. -4Below Pa, purge with 99.99 wt.% argon gas to -0.05 MPa, repeat this step, and purge the gas 3 times.

[0064] (3) After the arc is started, adjust the arc current to 200A and melt the titanium ingot for 2 minutes to remove the residual oxygen. Then adjust the current to 250A and melt the alloy in the crucible for 2 minutes. Repeat the melting process 5 times.

[0065] (4) Transfer the smelted alloy ingot to a suction casting crucible for suction casting. The arc current is 300A. After the alloy ingot is completely melted, turn on the suction casting switch to perform suction casting. After the suction casting is completed, the ingot will have dimensions of 25×6×45mm. 3 NiFeMn as-cast plate;

[0066] (5) The NiFeMn as-cast plate obtained in step (4) is sealed using a sealing machine. The NiFeMn plate in vacuum after sealing is then homogenized at 1173K for 24 hours. After the homogenization process is completed, it is water-quenched to obtain the target plate.

[0067] (6) Cut the target sheet material obtained in step (5) into 20×20×1mm pieces. 3 Thin sheets are ground and polished until smooth, and then etched in a nitric acid solution (nitric acid, water and alcohol are prepared in a volume ratio of 1:4.5:4.5) for 1 hour to obtain a self-supported Ni-Fe-Mn oxygen evolution electrocatalyst.

[0068] The obtained self-supported Ni-Fe-Mn oxygen evolution electrocatalyst was studied by X-ray diffraction (XRD), characterized by SEM and TEM, and its electrocatalytic oxygen evolution activity and electrocatalytic stability were tested. The results were similar to those of Example 1. The present invention successfully prepared a self-supported Ni-Fe-Mn oxygen evolution electrocatalyst. The morphology of the sample showed a structure in which a large number of nanocones covered the surface of nickel-iron-manganese metal, and the interlacing structure between the nanocones was beneficial to the catalytic activity and stability of the material. The sample was amorphous and had abundant active sites, which was beneficial to the catalytic activity of the material. The electrocatalytic oxygen evolution activity and electrocatalytic stability test results showed that the self-supported Ni-Fe-Mn oxygen evolution electrocatalyst provided by the present invention had excellent catalytic activity and stability.

[0069] Example 3

[0070] (1) Remove the oxide layer and impurities on the surface of Ni and Fe metal raw materials by mechanical grinding. Remove the oxide layer on the surface of Mn metal by a mixed solution of nitric acid, hydrofluoric acid and water, wherein the volume ratio of nitric acid, hydrofluoric acid and water is 20:5:75. After cleaning, place it in anhydrous ethanol for ultrasonication. After ultrasonication, dry it. Then weigh 10g Ni, 15g Fe and 25g Mn.

[0071] (2) Place the weighed raw materials into the crucible of the vacuum non-consumable arc melting furnace, and evacuate the vacuum non-consumable arc melting furnace to 8×10⁻⁶. -4 Below Pa, purge with 99.99 wt.% argon gas to -0.05 MPa, repeat this step, and purge the gas 3 times.

[0072] (3) After the arc is started, adjust the arc current to 200A and melt the titanium ingot for 2 minutes to remove the residual oxygen. Then adjust the current to 250A and melt the alloy in the crucible for 2 minutes. Repeat the melting process 4 times.

[0073] (4) Transfer the smelted alloy ingot to a suction casting crucible for suction casting. The arc current is 300A. After the alloy ingot is completely melted, turn on the suction casting switch to perform suction casting. After the suction casting is completed, the ingot will have dimensions of 25×6×45mm. 3 NiFeMn as-cast plate;

[0074] (5) The NiFeMn as-cast plate obtained in step (4) is sealed using a sealing machine. The NiFeMn plate in vacuum after sealing is then homogenized at 1215K for 24 hours. After the homogenization process is completed, it is water-quenched to obtain the target plate.

[0075] (6) Cut the target sheet material obtained in step (5) into 30×25×2mm pieces. 3 Thin sheets are ground and polished until smooth, and then etched in a nitric acid solution (nitric acid, water and alcohol are prepared in a volume ratio of 1:4.5:4.5) for 1 hour to obtain a self-supported Ni-Fe-Mn oxygen evolution electrocatalyst.

[0076] The obtained self-supported Ni-Fe-Mn oxygen evolution electrocatalyst was studied by X-ray diffraction (XRD), characterized by SEM and TEM, and its electrocatalytic oxygen evolution activity and electrocatalytic stability were tested. The results were similar to those of Example 1. The present invention successfully prepared a self-supported Ni-Fe-Mn oxygen evolution electrocatalyst. The morphology of the sample showed a structure in which a large number of nanocones covered the surface of nickel-iron-manganese metal, and the interlacing structure between the nanocones was beneficial to the catalytic activity and stability of the material. The sample was amorphous and had abundant active sites, which was beneficial to the catalytic activity of the material. The electrocatalytic oxygen evolution activity and electrocatalytic stability test results showed that the self-supported Ni-Fe-Mn oxygen evolution electrocatalyst provided by the present invention had excellent catalytic activity and stability.

[0077] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a self-supporting Ni-Fe-Mn oxygen evolution electrocatalyst, characterized in that, Ni, Fe, and Mn metal raw materials are repeatedly smelted. After smelting, they are suction-cast to obtain as-cast plates. The as-cast plates are homogenized, cut, and polished. Finally, they are etched in nitric acid solution to obtain the final product. Specifically, the following steps are included: (1) Prepare the Ni, Fe and Mn metal raw materials; (2) Place the weighed raw materials into the crucible of the vacuum non-consumable electric arc melting furnace and circulate the gas for washing 3 to 5 times. (3) After the arc is started, adjust the arc current to 200-250A to melt the titanium ingot to remove the residual oxygen. Then adjust the current to 250-300A to melt the alloy in the crucible. Repeat the melting process 3-5 times. (4) Transfer the alloy ingot after melting to a suction casting crucible for suction casting. The arc current is 250-300A. After the alloy ingot is completely melted, turn on the suction casting switch to perform suction casting. After the suction casting is completed, NiFeMn as-cast plate is obtained. (5) The NiFeMn as-cast plate obtained in step (4) is sealed using a sealing machine, and then the NiFeMn plate in vacuum after sealing is homogenized. After the homogenization process is completed, it is water-quenched to obtain the target plate. (6) After cutting and polishing the target plate obtained in step (5), it is etched in nitric acid solution to obtain the self-supported Ni-Fe-Mn oxygen evolution electrocatalyst. In step (1), the ingredients are prepared according to a total mass ratio of 45 to 55 parts of Ni, Fe and Mn, wherein the Mn content is 10 to 50% of the total raw materials, and the remainder is Ni and Fe, with a mass ratio of Ni to Fe of (2 to 3):(3 to 5). In step (6), the nitric acid solution is prepared by mixing concentrated nitric acid, water and anhydrous ethanol in a volume ratio of (1-2):(4-4.5):(4-4.5).

2. The preparation method according to claim 1, characterized in that, The specific operation of the circulating gas washing in step (2) is as follows: the vacuum non-consumable arc melting furnace is evacuated to 6×10 -4 ~8×10 -4 Pa, fill with argon gas to -0.01 to -0.05 MPa, and repeat this step.

3. The preparation method according to claim 1, characterized in that, The melting time in step (3) is 1 to 2 minutes.

4. The preparation method according to claim 1, characterized in that, In step (5), the homogenization temperature is 1173–1373 K and the homogenization time is 22–26 h.

5. The preparation method according to claim 1, characterized in that, Before the batching process in step (1), the Ni, Fe, and Mn metal raw materials are pretreated.

6. The preparation method according to claim 5, characterized in that, The pretreatment is as follows: Ni and Fe metal raw materials are removed from the metal surface oxide layer and impurities by mechanical grinding, and the metal Mn is removed from the surface oxide layer by a mixed solution of concentrated nitric acid, hydrofluoric acid and water. After cleaning, the raw materials are placed in anhydrous ethanol for ultrasonication, and then dried for later use.

7. The self-supporting Ni-Fe-Mn oxygen evolution electrocatalyst prepared by the preparation method according to any one of claims 1 to 6.

Images