Method for the production of spinel coatings and their use in the production of solid oxide electrolysis devices

Abstract

The application relates to a preparation method of a manganese-cobalt spinel coating, which comprises the following steps: (a) preparing a metal precursor powder, wherein the metal precursor powder is manganese powder and cobalt powder; (b) configuring a metal precursor suspension liquid; (c) heating a substrate to a specified temperature, so that the metal precursor suspension liquid dispersant can be fully gasified on the surface of the substrate; (d) spraying the metal precursor suspension liquid on the surface of the substrate by using a high-pressure atomization spraying method, a rotary atomization spraying method or an ultrasonic atomization spraying method, so as to form a metal precursor layer attached to the surface of the substrate; (e) densifying and sintering; and (f) oxidizing and sintering. The preparation method can effectively eliminate the pores existing in the precursor coating, is helpful for preparing the manganese-cobalt spinel coating with uniform and dense texture and high thickness, and has the advantages of simple process, easy operation and strong economy.

Description

Technical Field

[0001] This application relates to the field of high-temperature ceramic materials technology, and in particular to a method for preparing a spinel coating and its application in the preparation of a solid oxide electrolysis device. Background Technology

[0002] An electrolytic cell is a device that directly converts electrical energy into chemical energy through an electrolytic reaction. It is mainly used for hydrogen production and chemical energy storage, and boasts advantages such as high energy conversion efficiency, low environmental pollution, low noise, high reliability, and ease of construction. Depending on the electrolyte used, electrolytic cells can be classified into alkaline electrolytic cells, proton exchange membrane electrolytic cells, and solid oxide electrolytic cells, among others.

[0003] Solid oxide electrolyzers are electrolyzers that use solid oxides as electrolytes and operate at high temperatures. They typically use yttrium-stabilized zirconia or other solid ceramic electrolytes and operate at temperatures between 650 and 1000°C. A solid oxide electrolyzer mainly consists of an electrolyte, a hydrogen electrode, and an oxygen electrode. During operation, water molecules are electrolyzed into hydrogen and oxygen ions at the oxygen electrode. Hydrogen is collected as an electrolysis product, while oxygen ions, under the influence of an applied electric field, migrate through oxygen vacancies in the electrolyte to the oxygen electrode and release electrons to generate O2. Compared to other types of electrolyzers, solid oxide electrolyzers offer advantages such as lower material costs, higher hydrogen production efficiency, higher energy conversion efficiency, and the ability to co-electrolyze CO2.

[0004] In flat-plate solid oxide electrolysis units, connectors are required between the solid oxide electrolytic cells to conduct current between them and separate hydrogen and oxygen. Furthermore, these connectors also serve as supports for the electrolysis unit, ensuring its mechanical stability. Currently, ferritic stainless steel is primarily used for casting these connectors. Ferritic stainless steel offers advantages such as low manufacturing cost, high mechanical strength, strong electrical conductivity, and good creep resistance.

[0005] Although the linker can form an antioxidant layer with Cr2O3 as the main component on its surface, it will still undergo continuous oxidation in the working environment of a solid oxide electrolytic cell (650-800℃), generating a Cr2O3 layer with poor conductivity. This damages the perovskite structure of the oxygen electrode, weakens the oxygen electrode material's ability to conduct oxygen ions, and leads to a rapid decline in the performance of the oxygen electrode and even the overall SOEC.

[0006] To address the problems caused by oxidation on the connector surface, the most effective solution is to prepare a manganese-cobalt spinel coating with good conductivity and oxidation resistance. Manganese-cobalt spinel is chemically stable at 650–850℃, has good conductivity, and low oxygen ion conductivity, making it suitable as the main material for the oxidation-resistant coating. This delays connector oxidation while inhibiting the outward diffusion of chromium compounds. By preparing a 20–30 μm thick manganese-cobalt spinel coating on the cathode side of the solid oxide battery connector, the oxidation rate of the connector can be effectively reduced, and the outward diffusion of chromium compounds can be inhibited, thus delaying performance degradation.

[0007] Compared to solid oxide batteries, the oxygen electrode in a solid oxide electrolyzer continuously releases oxygen during electrolysis, leading to a significant increase in the oxygen partial pressure on the oxygen electrode side of the connector. Furthermore, the applied current in the solid oxide electrolyzer accelerates the directional migration rate of oxygen and chromium ions, resulting in a significant increase in the rates of connector oxidation and chromium diffusion. Under harsh operating conditions, to maintain the long-term performance of the connector, the thickness needs to be increased to 80–120 μm while maintaining the density of the manganese-cobalt spinel coating.

[0008] Existing coating preparation technologies mainly include physical vapor deposition (PVD), thermal spraying, and liquid phase deposition (including electrophoretic deposition, impregnation, liquid phase spraying, and screen printing). PVD and thermal spraying produce coatings with high density (porosity <10%), but their material utilization rate is too low (<20%), leading to excessively high material costs and making them unsuitable for mass production. For example, impregnation, electrophoretic deposition, or ultrasonic atomization spraying have an optimal target coating thickness range of 20–40 micrometers. Beyond this range, due to the weak adhesion of the precursor coating and the impact of the deposition process on the existing coating structure, continued deposition may damage the existing coating structure, thus making them unsuitable for preparing spinel coatings with a thickness of 60–120 micrometers.

[0009] For liquid phase deposition, CN113584466A discloses a technique for preparing a manganese cobalt spinel coating by coating a metal oxide precursor (e.g., metal nitrate). The technique involves obtaining a spinel oxide film by repeating ultrasonic atomization spraying and heating steps, followed by sintering to obtain the spinel coating. However, the process has the following problems: (1) In the densification sintering step, Co2O3 is reduced to Co and MnO2 is reduced to MnO, resulting in a significant volume shrinkage (30-45%) of the coating as a whole, leading to the generation of μm-level structural defects; (2) Due to the performance of the connecting steel material, the high-temperature reducing atmosphere sintering temperature generally cannot exceed 1000℃, otherwise it will cause the steel to soften severely. However, at this temperature, Co (melting point 1495℃) and MnO (melting point 1650℃) cannot be effectively softened, making it difficult to reduce the porosity inside the precursor coating through high-temperature sintering; (3) In the oxidation sintering step, MnO and Co are re-oxidized to form manganese cobalt spinel, but compared with the initial metal oxide coating, its volume still shrinks by 5-10%, which seriously hinders the formation of a dense coating structure. Summary of the Invention

[0010] To address any of the aforementioned technical problems in the prior art, this application provides the following technical solution:

[0011] This application provides a method for preparing a manganese cobalt spinel coating, wherein the spinel in the manganese cobalt spinel coating has the molecular formula Mn. X Co 3-X O4 (1.0≤X≤2.0) is mainly formed by a mixture of MnCo2O4 in the formal spinel form and Mn2CoO4 in the trans spinel form;

[0012] The preparation method includes the following steps:

[0013] (a) Prepare metal precursor powder, wherein the metal precursor powder is manganese powder and cobalt powder, wherein the molar ratio of manganese powder to cobalt powder is X:(3-X), and the average particle size of manganese powder and cobalt powder should be below 10μm.

[0014] (b) Prepare a metal precursor suspension, wherein the dispersed phase in the metal precursor suspension is the metal precursor powder, the total mass concentration of the dispersed phase is less than 2%, and the dispersant in the metal precursor suspension is a non-oxidizing and volatile liquid.

[0015] (c) Heat the matrix to a specified temperature, which should be 5 to 50°C higher than the boiling point of the dispersant;

[0016] (d) The metal precursor suspension is sprayed onto the substrate surface using high-pressure atomization spraying, rotary atomization spraying or ultrasonic atomization spraying to form a metal precursor layer with an average thickness of more than 40 μm adhering to the substrate surface.

[0017] (e) The substrate carrying the metal precursor layer is placed in a high-temperature reducing atmosphere for densification sintering.

[0018] (f) After densification sintering is completed, the substrate is placed in a high-temperature oxidizing atmosphere for oxidation sintering, and after cooling, the manganese cobalt spinel coating is prepared.

[0019] This application also provides a manganese cobalt spinel coating prepared by the above-described method.

[0020] This application also provides the application of the above-mentioned method for preparing manganese cobalt spinel coating in the preparation of solid oxide electrolysis devices.

[0021] Based on the above technical solutions, the preparation method of the manganese cobalt spinel coating of this application effectively avoids the structural defects caused by oxygen loss and shrinkage of the precursor coating during the densification sintering process by using manganese powder and cobalt powder to construct the precursor coating, thereby improving the densification sintering effect and increasing the density of the spinel coating; and by using a low-boiling-point organic liquid with a mild evaporation process as a dispersant, the rapid preparation of a high-thickness precursor coating is achieved.

[0022] This preparation method has at least one of the following advantages over existing technologies:

[0023] (1) This application directly uses manganese cobalt metal powder to prepare the precursor coating. Compared with metal oxides, manganese cobalt metal powder has the following advantages: manganese cobalt metal powder avoids the volume shrinkage and generation of micron-level structural defects in the densification sintering step; manganese has a melting point of only 1244℃. If it is mixed with cobalt at high temperature to form an alloy, its melting point will be reduced to below 1200℃. It can be significantly softened at 850~1000℃, which can effectively reduce the porosity in the precursor coating; during the oxidation of manganese cobalt metal to form spinel, its volume expands by 90~105%, which can effectively eliminate the pores in the precursor coating and help to prepare a uniform, dense, and thick manganese cobalt spinel coating.

[0024] (2) The preparation method of this application has the advantages of simple process, easy operation and strong economy. Attached Figure Description

[0025] The following description, in conjunction with the accompanying drawings, further illustrates this application:

[0026] Figure 1 This is a schematic diagram of the preparation process of this application;

[0027] Figure 2 This is a surface morphology diagram of the precursor layer obtained by spraying according to Embodiment 1 of this application;

[0028] Figure 3 This is a surface morphology diagram of the coating obtained after densification sintering in Example 1 of this application;

[0029] Figure 4 This is a surface morphology diagram of the MnCo2O4 spinel coating obtained after oxidation sintering, as provided in Example 1 of this application.

[0030] Figure 5 This is a cross-sectional morphology diagram of the MnCo2O4 spinel coating obtained after oxidation sintering in Example 1 of this application.

[0031] Figure 6 The graph shows the trend of surface resistivity increase in Examples 1-5 and Comparative Example 1 at 800°C in an air atmosphere.

[0032] Figure 7 This is a graph showing the oxidation weight gain trend of Examples 1-5 and Comparative Example 1 in an air atmosphere at 800°C. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with specific embodiments.

[0034] like Figure 1 As shown, the preparation method of the manganese cobalt spinel coating of this application mainly includes preparing a metal precursor suspension mainly composed of manganese powder and cobalt powder, spraying the suspension onto the surface of the connector to form a metal precursor layer, densification sintering, and oxidation sintering.

[0035] In one embodiment, the average particle size of the manganese powder in step (a) is preferably 2 μm, the average particle size of the cobalt powder is preferably 5 μm, the purity of the manganese powder is >99.5%, and the purity of the cobalt powder is >99%. The spraying process mainly consumes basic industrial raw materials such as manganese and cobalt metal powders, and the raw material utilization rate can be as high as 95% or more, which can effectively reduce material costs.

[0036] In one embodiment, in step (b), the concentration of manganese powder in the suspension is 5.0 g / L and the concentration of cobalt powder is 10.0 g / L.

[0037] In one embodiment, the dispersant in step (b) includes one or more of the following: C1-C3 alcohols, C3-C5 ketones, C5-C9 alkanes, C2-C4 ethers, and C1-C2 haloalkanes, preferably ethanol.

[0038] In one embodiment, step (b) may further include the addition of a surfactant and a coating binder to the dispersant. The surfactant and coating binder should be organic compounds composed entirely of carbon, hydrogen, oxygen, and nitrogen. The specific elements are chosen to ensure that the surfactant and coating binder can be completely vaporized and removed during sintering, without affecting the final composition of the coating. The surfactant is primarily used to maintain the stability of the suspension and prevent excessively rapid sedimentation. Specifically, surfactants may include polyvinyl alcohol, polyethylene glycol, polypropylene, etc. The coating binder is primarily used to maintain the structural stability of the precursor coating, the internal bonding force of the coating, and the interfacial bonding force between the coating and the connector, especially on the vertical substrate surface. Coating binders include methyl cellulose, ethyl cellulose, epoxy resin, polymethyl acrylate, etc. Since organic matter will eventually form pores after evaporation or oxidation, the mass concentration of the surfactant should not exceed 20% of the sum of the mass concentrations of manganese powder and cobalt powder, and the mass concentration of the coating binder should not exceed 15% of the sum of the mass concentrations of manganese powder and cobalt powder, in order to effectively control the porosity of the precursor coating. By making reasonable adjustments to the preparation method, the coating preparation process can form a stable precursor coating on near-plane (tilt angle 0-5°), inclined (tilt angle 5-80°) and near-vertical (80-85°) surfaces, which can be adapted to various connector structure designs.

[0039] In one embodiment, the surfactant in step (b) is polyethylene glycol with a concentration of 0.5 g / L, and / or the coating binder is polymethyl acrylate with a concentration of 0.4 g / L.

[0040] In one embodiment, the substrate in step (c) is a connector, and / or the substrate is SUS430 ferritic stainless steel.

[0041] In one embodiment, during the spraying process in step (d), the substrate surface temperature is 120°C.

[0042] In one embodiment, in step (d), the average thickness of the metal precursor layer is 50–60 μm, and the porosity is 40%.

[0043] In one embodiment, in step (d), the suspension is delivered to the nozzle at a rate of 2.0 ml / min, and / or the spray area covers the substrate surface with a radius of 1.5 cm.

[0044] In one embodiment, in step (e), before the densification sintering begins, the substrate is placed in an atmosphere furnace, and a N2 / H2 mixed gas is introduced into the atmosphere furnace to purge the air inside the furnace, wherein the N2 volume percentage is 90% and the H2 volume percentage is 10%. Subsequently, the furnace temperature is increased to 900°C at a heating rate of 5°C / min and held at that temperature for 48 hours. During the temperature holding process, the N2 / H2 mixed gas is continuously introduced into the furnace to ensure that the connector and the metal precursor coating do not oxidize.

[0045] In one embodiment, the oxidation sintering in step (f) refers to cooling the furnace temperature at a rate of 5°C / min to a specified oxidation sintering temperature of 850°C. After the furnace temperature reaches the specified oxidation sintering temperature, N2 is first introduced to purge H2 into the furnace, followed by air to purge N2 into the furnace, and the temperature is kept constant for 48 hours.

[0046] In one embodiment, the cooling in step (f) refers to the vacuum sintering furnace temperature being reduced to below 50°C at a rate of 5°C / min.

[0047] In one embodiment, the average thickness of the manganese cobalt spinel coating in step (f) is 75–85 μm.

[0048] In one embodiment, the preparation method further includes a step of pretreating the substrate surface before spraying.

[0049] In one embodiment, the pretreatment step is to sandblast or grind the substrate surface to remove the oxide layer.

[0050] Example

[0051] Those skilled in the art can refer to the content of this document to appropriately improve the process parameters. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included within this application. The methods and applications of this application have been described through preferred embodiments. Those skilled in the art can obviously modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit, and scope of this application to implement and apply the technology of this application. The following examples further illustrate this application: Example 1

[0052] A method for preparing a spinel coating, the method comprising the following steps:

[0053] (1) Provide SUS430 ferritic stainless steel to remove the oxide layer on the surface and ensure that the metal powder can adhere to the surface of the connector.

[0054] (2) Prepare a suspension of manganese and cobalt metal powder with ethanol as the dispersant. The purity of ethanol is ≥99.5%. The concentration of manganese powder in the suspension is 5.0 g / L, the concentration of cobalt powder is 10.0 g / L, the concentration of surfactant polyethylene glycol is 0.5 g / L, and the concentration of coating binder polymethyl acrylate is 0.4 g / L.

[0055] (3) Place the connector after grinding in step (1) on the hot table and set the temperature of the hot table to 120°C. Then use an injection pump to deliver the manganese cobalt metal powder suspension to the high-pressure nozzle at a rate of 2 ml / min. The coverage radius of the spray area on the surface of the connector is 1.5 cm. The nozzle moves left and right repeatedly during the spraying process to cover the entire spraying area. Its movement speed is 10 cm / s and the width is 0.5 mm. The metal precursor layer is obtained by spraying.

[0056] (4) Repeat step (3) above until a metal precursor layer with an average thickness of 55 μm is formed on the surface of the ferritic stainless steel. Figure 2 This is a surface morphology diagram of the metal precursor layer obtained by ultrasonic spraying before sintering in this embodiment.

[0057] (5) The connector carrying the metal precursor layer is placed in an atmosphere furnace for sintering. This allows the metal precursor layer to be fully densified. The specific sintering method is as follows: the air in the furnace is purged with 90% N2 / 10% H2; the atmosphere furnace is heated from room temperature to 900℃ at a heating rate of 5℃ / min and held at 900℃ for 48 hours to achieve densification sintering. Figure 3 and Figure 4 The images show the surface and cross-sectional morphology of the coating obtained after densification sintering in Example 1 of this invention. The temperature was then lowered to 850°C at a rate of 5°C / min; H2 was purged with N2, followed by air purging of N2 and holding at this temperature for 48 hours; the furnace temperature was then lowered to room temperature at a rate of 5°C / min, resulting in a manganese-cobalt spinel coating with an average thickness of approximately 80 μm on the surface of the connector. The metal powder adhering to the surface of the connector underwent the following reaction under a high-temperature oxidizing atmosphere:

[0058] 3Mn + 2O2 = Mn3O4;

[0059] 3Co + 2O₂ = Co₃O₄;

[0060] Mn3O4 + 2Co3O4 = 3MnCo2O4.

[0061] Figure 5 This is a surface morphology diagram of the MnCo2O4 spinel coating obtained in this embodiment.

[0062] Example 2

[0063] The main difference was that the concentration of manganese powder in the suspension in Example 1 was adjusted to 7.2 g / L, and the concentration of cobalt powder was adjusted to 7.8 g / L. The spinel coating after sintering was mainly composed of Mn. 1.5 Co 1.5 O4, the rest are the same as in Example 1.

[0064] Example 3

[0065] The main difference was that the concentration of manganese powder in the suspension in Example 1 was adjusted to 9.7 g / L and the concentration of cobalt powder was adjusted to 5.3 g / L. The main component of the spinel coating after sintering was Mn2CoO4, and the rest were the same as in Example 1.

[0066] Example 4

[0067] The main difference is that the average thickness of the precursor coating in Example 1 was adjusted to 42 μm, and the average thickness of the sintered manganese cobalt spinel coating was 60 μm. The rest is the same as in Example 1.

[0068] Example 5

[0069] The main difference is that the average thickness of the precursor coating in Example 1 was adjusted to 80 μm, and the average thickness of the sintered manganese cobalt spinel coating was 116 μm. The rest is the same as in Example 1.

[0070] Comparative Example 1

[0071] SUS430 sample that has only been polished and has not been coated.

[0072] To test the long-term stability of the manganese-cobalt spinel coating in this application under the operating environment of a solid oxide electrolysis device, the coating samples from Examples 1-5 and Comparative Example 1 were placed in an air atmosphere at 800°C for 2000 hours, and the change in their areal resistivity under high-temperature conditions was measured. The measurement results of the increase in areal resistivity and the weight gain due to oxidation are as follows: Figure 6 and Figure 7 As shown.

[0073] Long-term testing results show that the uncoated connector sample, lacking an antioxidant coating, exhibits a rapid oxidation rate, resulting in a rapid increase in surface resistivity and mass during the 2000-hour long-term test. The sample in the example, protected by a manganese-cobalt spinel coating, shows a slower rate of increase in surface resistivity and mass. The spinel coating effectively improves the connector's oxidation resistance and stability at high temperatures. The performance of the manganese-cobalt spinel coating is negatively correlated with its thickness; increasing the thickness significantly improves the coating's long-term oxidation resistance.

[0074] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A method for preparing a manganese cobalt spinel coating, characterized in that, The spinel in the manganese-cobalt spinel coating has the molecular formula Mn. X Co 3-X O4, 1.0≤X≤2.0, is mainly formed by MnCo2O4 in the formal spinel form, or mainly formed by Mn2CoO4 in the trans spinel form, or mainly formed by a mixture of MnCo2O4 in the formal spinel form and Mn2CoO4 in the trans spinel form. The preparation method includes the following steps: (a) Prepare metal precursor powder, wherein the metal precursor powder is manganese powder and cobalt powder, wherein the molar ratio of manganese powder to cobalt powder is X:(3-X). (b) Prepare a metal precursor suspension, wherein the dispersed phase in the metal precursor suspension is the metal precursor powder, and the dispersant in the metal precursor suspension is a non-oxidizing and volatile liquid. (c) Heating the matrix to a specified temperature, said specified temperature being higher than the vaporization point of the suspension dispersant; (d) A metal precursor suspension is sprayed onto the surface of a substrate using a high-pressure atomization spraying, rotary atomization spraying, or ultrasonic atomization spraying method to form a metal precursor layer attached to the surface of the substrate; the surface temperature of the substrate is 80~160℃, the porosity of the metal precursor layer is below 45%, and the average thickness of the metal precursor layer is 42~80μm; (e) The substrate carrying the metal precursor layer is placed in a high-temperature reducing atmosphere for densification sintering. (f) After densification sintering is completed, the substrate is placed in a high-temperature oxidizing atmosphere for oxidation sintering, and after cooling, the manganese cobalt spinel coating is prepared.

2. The method for preparing the manganese-cobalt spinel coating according to claim 1, characterized in that, The average particle size of the manganese powder and cobalt powder in step (a) is no greater than 10 μm; in step (b), the total mass concentration of the metal powder is less than 2%; and the dispersant in step (b) is selected from one or more of the following: C1-C3 alcohols, C3-C5 ketones, C5-C9 alkanes, C2-C4 ethers, and C1-C2 haloalkanes.

3. The method for preparing the manganese-cobalt spinel coating according to claim 1, characterized in that, The dispersant in step (b) is ethanol. In step (b), a surfactant and / or coating binder are added to the dispersant. The surfactant and coating binder are organic compounds composed entirely of carbon, hydrogen, oxygen, and nitrogen. The surfactant includes polyvinyl alcohol, polyethylene glycol, and / or polypropylene. The coating binder includes methyl cellulose, ethyl cellulose, epoxy resin, or polymethyl acrylate. The mass concentration of the surfactant is less than 20% of the sum of the mass concentrations of the manganese powder and cobalt powder, and the mass concentration of the coating binder is less than 15% of the sum of the mass concentrations of the manganese powder and cobalt powder. The surfactant in step (b) is polyethylene glycol, and the coating binder is polymethyl acrylate.

4. The method for preparing the manganese-cobalt spinel coating according to claim 1, characterized in that, In step (d), the coverage radius of the sprayed area on the substrate surface is 1~5cm.

5. The method for preparing the manganese-cobalt spinel coating according to claim 1, characterized in that, In step (e), before densification sintering begins, the matrix is ​​placed in an atmosphere furnace and N2 / H2 mixed gas is introduced into the atmosphere furnace. The temperature is then raised to 850-1000°C and kept constant. During the temperature-keeping process, N2 / H2 mixed gas is continuously introduced into the furnace.

6. The method for preparing the manganese-cobalt spinel coating according to claim 5, characterized in that, In step (e), the N2 / H2 mixed gas has an H2 volume percentage of more than 1%, a heating rate of less than 10℃ / min, and a constant temperature duration of more than 6h.

7. The method for preparing the manganese-cobalt spinel coating according to claim 1, characterized in that, The oxidation sintering mentioned in step (f) refers to cooling the furnace temperature of the atmosphere furnace to the specified oxidation sintering temperature at a cooling rate of less than 10℃ / min. The specified oxidation sintering temperature is 800-900℃. After the furnace temperature reaches the specified oxidation sintering temperature, N2 is first introduced to purge H2 in the furnace, followed by air to purge N2, and the temperature is kept constant for more than 6 hours. After the oxidation sintering mentioned in step (f) is completed, the furnace temperature of the vacuum sintering furnace is cooled to below 50℃ at a cooling rate of less than 10℃ / min.

8. The method for preparing the manganese-cobalt spinel coating according to claim 1, characterized in that, The substrate in step (c) is a connector, and / or the substrate is ferritic stainless steel; the preparation method further includes a step of pretreating the substrate surface before spraying.

9. The method for preparing the manganese-cobalt spinel coating according to claim 8, characterized in that, The pretreatment step is to sandblast or grind the substrate surface to remove the oxide layer.

10. A manganese cobalt spinel coating prepared by the method of preparing a manganese cobalt spinel coating according to any one of claims 1 to 9.

11. The application of a method for preparing a manganese cobalt spinel coating according to any one of claims 1 to 9 in the preparation of a solid oxide electrolysis device.

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