Modified electrode, its preparation method and application

Abstract

The present invention provides a modified electrode, a preparation method thereof and an application. The modified electrode includes an electrode substrate and a mixed coating distributed on the surface of the electrode substrate. The mixed coating includes a metal element and a metal oxide. Among them, in the direction away from the electrode substrate, in the mixed coating, the weight percentage content of the metal oxide increases, and the weight percentage content of the metal element decreases; the metal element includes one or more of nickel, cobalt and zinc. By constructing a gradient distribution mixed coating of a metal element and a metal oxide on the surface of the electrode substrate, the synergistic effect of the metal oxide and the metal element not only effectively solves the problems of insufficient pore structure and poor coating stability of the traditional oxide electrode, but also significantly improves the catalytic performance and service life of the electrode.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogen production by electrolyzing water, and more particularly, to a modified electrode, a preparation method thereof, and an application thereof. Background Art

[0002] Hydrogen, as a clean energy carrier, not only has a high energy density, but also only produces water after combustion without greenhouse gas emissions. Therefore, its efficient and sustainable production technology has become a research hotspot. Among them, electrolyzing water to produce hydrogen using renewable energy is regarded as an important way to realize the hydrogen economy, and the demand for catalysts is becoming increasingly prominent.

[0003] Catalysts in the process of electrolyzing water, especially metal oxide catalysts, have attracted much attention due to their high cost-effectiveness, potential high catalytic activity, and good environmental compatibility. Transition metal oxides, such as oxides of iron, cobalt, nickel, etc., theoretically can provide high catalytic activity due to their rich electronic structures and tunability. However, in actual industrial applications, their potential has not been fully explored. The main technical bottlenecks are as follows: 1. Insufficient pore structure: Compared with porous Raney nickel electrodes, the surface porosity of metal oxide electrodes is relatively low, which limits the exposure of active sites and thus affects the improvement of the catalytic active area. The pore structure can promote the penetration of electrolytes and the diffusion of products during the electrolysis process. The lack of pores greatly restricts the performance of metal oxide electrodes. 2. Electrode adhesion and stability problems: The adhesion between the oxide coating and the electrode substrate (such as nickel foam, carbon cloth, etc.) is weak, which leads to the formation of cracks in the coating during the electrolysis of water, especially at high current densities, and the coating peeling phenomenon is more obvious. Coating peeling not only affects the lifespan of the electrode, but also may cause a decrease in catalyst activity, thereby affecting the efficiency and cost of hydrogen production by electrolyzing water. 3. Difficulties in large-scale processing: Although metal oxide electrodes have cost advantages, when preparing large-area, especially industrial-grade electrodes, there is a lack of effective and reproducible processing technologies. Traditional electrode preparation methods such as physical vapor deposition and chemical vapor deposition can prepare high-quality coatings, but these methods are usually difficult to achieve large-area continuous processing, which limits their application in large-scale electrolyzers.

[0004] Therefore, developing an electrode and its preparation method that can overcome the above defects has important theoretical and practical significance for promoting the commercialization process of hydrogen production technology by electrolyzing water and realizing the efficient and economical production of hydrogen. Summary of the Invention

[0005] The main object of the present invention is to provide a modified electrode, a preparation method thereof, and an application thereof to solve the problems in the prior art that the electrolyzing water electrode has few pore structures, the coating is easy to peel off, resulting in low catalytic activity, low efficiency, short lifespan, and difficulty in large-scale processing of the electrode.

[0006] To achieve the above object, according to one aspect of the present invention, a modified electrode is provided, which includes an electrode substrate and a mixed coating distributed on the surface of the electrode substrate. The mixed coating includes metallic elements and metal oxides. Among them, in the direction away from the electrode substrate, in the mixed coating, the weight percentage content of the metal oxides increases, and the weight percentage content of the metallic elements decreases; the metallic elements include one or more of nickel, cobalt, and zinc.

[0007] Further, in the mixed coating, the weight ratio of the metallic elements to the metal oxides is (1-10):10; and / or, in the direction away from the electrode substrate, in the mixed coating, the weight percentage content of the metal oxides increases from 25-50% to 50-75%, and the weight percentage content of the metallic elements decreases from 50-75% to 25-50%; preferably, in the direction away from the electrode substrate, the mass concentration growth rate of the metal oxides in the mixed coating is 1-5% / μm; preferably, in the direction away from the electrode substrate, the mass concentration reduction rate of the metallic elements in the mixed coating is 1-5% / μm.

[0008] Further, the metal oxides include oxides of one or more of titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, ruthenium, rhodium, palladium, osmium, iridium, and platinum; and / or, the electrode substrate includes one of nickel felt, nickel foam, and nickel mesh. Preferably, the porosity of the electrode substrate is 25-75%.

[0009] Further, the thickness of the mixed coating is 10-200μm; and / or, the porosity of the mixed coating is 25-75%.

[0010] According to another aspect of the present invention, a preparation method of the above-mentioned modified electrode is provided. The modified electrode includes an electrode substrate and a mixed coating on the surface of the electrode substrate. The mixed coating includes metallic elements and metal oxides. Among them, in the direction away from the electrode substrate, in the mixed coating, the weight percentage content of the metal oxides increases, and the weight percentage content of the metallic elements decreases; the metallic elements include one or more of nickel, cobalt, and zinc. The preparation method includes the following steps: Step S1, mixing the raw materials of the metal oxides, then performing a hydrothermal reaction to obtain a metal compound, and then performing calcination to obtain the metal oxides; Step S2, mixing the metal oxides with the metallic elements and performing ball milling to obtain a metal mixture; Step S3, in the presence of a magnetic field, sending a laser beam, and using a magnetic field-assisted laser cladding method to melt the metal mixture and then deposit it on the surface of the electrode substrate to obtain the modified electrode.

[0011] Further, in step S1, the raw materials of the metal oxide include a metal precursor salt, a complexing agent, a precipitant, a surfactant and a solvent, preferably, the metal precursor salt includes one or more of metal chloride, nitrate, sulfate, acetate and acetylacetonate, the metal includes one or more of titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, ruthenium, rhodium, palladium, osmium, iridium and platinum, and the concentration of the metal precursor salt is 0.01-1 mol / L; and / or, preferably, the complexing agent includes one or more of potassium citrate, potassium sodium tartrate, diethanolamine, sodium tripolyphosphate, sodium alginate and sodium gluconate, and the molar ratio of the complexing agent to the metal precursor salt is (0.1-10):1; and / or, preferably, the precipitant includes one or more of sodium carbonate, potassium carbonate, sodium oxalate, potassium oxalate, sodium bicarbonate, potassium bicarbonate, sodium hydroxide and potassium hydroxide, and the molar ratio of the precipitant to the metal precursor salt is (0.1-10):1; And / or, preferably, the surfactant includes one or more of polyvinyl alcohol, hexadecyltrimethylammonium bromide, polyethyleneimine, polyvinyl alcohol ether, sodium octenylbenzene sulfonate, polyglutamic acid, chitosan and sodium dodecyl sulfate, and the molar ratio of the surfactant to the metal precursor salt is (0.1-10):1; and / or, preferably, the solvent includes one or more of water, ethanol and ether; and / or, the temperature of the hydrothermal reaction is 120-180°C, and the time is 2-24h; and / or, step S1 also includes the steps of washing, filtering and first drying the metal compound; preferably, the metal compound is washed 4 times with water, ethanol, acetone and water in sequence; preferably, the first drying is carried out by forced air drying or vacuum drying, the drying temperature is 60-100°C, and the time is 1-12h; and / or, the calcination temperature is 300-500°C, the time is 2-4h, and the atmosphere is one or more of air, oxygen and nitrogen.

[0012] Furthermore, in step S2, the particle size of the metal element is 100-500 mesh; and / or the weight ratio of the metal element to the metal oxide is (0.01-1):1; and / or the rotation speed of the ball mill is 150-500 rpm, and the time is 0.5-10 h; preferably, zircon beads of 10-30 mm are used as ball milling beads for ball milling; and / or, step S2 also includes the step of adding a dispersant during the ball milling process and performing a second drying on the mixture; preferably, the amount of the dispersant added is 10-50% of the metal element by weight percentage, and the dispersant includes one or more of ethanol, pentane and acetone; preferably, the second drying is forced air drying at a temperature of 25-60°C and a time of 0.5-24 h.

[0013] Further, in step S3, the intensity of the magnetic field is 0.001 - 0.1 T; and / or, the angle between the direction of the magnetic field and the perpendicular direction of the surface of the electrode substrate is ≤ 10°; and / or, the magnetic field is applied from the side of the electrode substrate away from the mixed coating; preferably, the magnetic field is sourced from an electromagnet or a permanent magnet.

[0014] Further, in step S3, the focal diameter of the laser beam is 100 - 500 μm, and the distance between the nozzle for emitting the laser beam and the side of the electrode substrate close to the mixed coating is 10 - 30 mm; and / or, the atmosphere for emitting the laser beam includes one or more of argon, helium, and carbon dioxide, and the gas flow rate is 5 - 20 L / min; and / or, the laser power is 1000 - 2500 W, and the cladding rate of the metal oxide and / or the metal element is 0.1 - 0.25 m / min; and / or, the metal mixture is fed into the reaction system through an inert gas, the inert gas includes argon and / or helium, and the gas flow rate is 1 - 5 L / min; and / or, the feeding rate of the metal mixture is 0.03 - 0.1 g / mm; and / or, the heat input in the laser cladding method is 400 - 600 J / mm.

[0015] According to another aspect of the present invention, there is provided an application of the above - modified electrode in the field of electrolyzing water.

[0016] The modified electrode of the present invention constructs a gradient - distributed mixed coating of metal elements and metal oxides on the surface of the electrode substrate. The synergistic effect of the metal oxides and the metal elements can not only effectively solve the problems of insufficient pore structure and poor coating stability of traditional oxide electrodes, but also significantly improve the catalytic performance and service life of the electrode. Description of the Drawings

[0017] The specification drawings forming a part of this application are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0018] Figure 1 It shows a schematic diagram of the preparation process of the modified electrode of Embodiment 1 of the present invention;

[0019] Figure 2 It shows a schematic diagram of the principle during the preparation of the modified electrode of Embodiment 1 of the present invention by the magnetic - field - assisted laser cladding method;

[0020] Figure 3 It shows a micro - morphology diagram of the modified electrode of Embodiment 1 of the present invention under a magnification of 200 times;

[0021] Figure 4 It shows a micro - morphology diagram of the modified electrode of Embodiment 1 of the present invention under a magnification of 20000 times; and

[0022] Figure 5 The schematic diagram of the principle of the electrode of Comparative Example 1 of the present invention during the preparation process by laser cladding method is shown.

[0023] Among them, the above-mentioned drawings include the following reference numerals:

[0024] 1. Electrode substrate; 2. Metal element; 3. Metal oxide. Specific embodiments

[0025] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the drawings and in combination with the embodiments.

[0026] As described in the background art of the present invention, in the prior art, there are technical problems such as few pore structures of the electrodes for electrolyzing water, easy peeling of the coating, resulting in low catalytic activity, low efficiency, short service life, and difficulty in large-scale processing of the electrodes. To solve the above problems, in a typical embodiment of the present invention, a modified electrode is provided, which includes an electrode substrate and a mixed coating distributed on the surface of the electrode substrate. The mixed coating includes a metal element and a metal oxide. Among them, in the mixed coating, in the direction away from the electrode substrate, the weight percentage content of the metal oxide increases, and the weight percentage content of the metal element decreases; the metal element includes one or more of nickel, cobalt, and zinc.

[0027] The modified electrode of the present application includes an electrode substrate and a mixed coating. In the mixed coating, in the direction away from the electrode substrate, the weight percentage content of the metal oxide increases, and the weight percentage content of the metal element decreases. This gradient distribution design enables the metal oxide to be fully exposed outside the coating, providing abundant active sites, thereby optimizing the contact interface between the electrode and the electrolyte and effectively improving the electrocatalytic efficiency, especially the catalytic activity of hydrogen evolution and oxygen evolution reactions. At the same time, the metal element close to the electrode substrate acts as a "binder", which can enhance the bonding strength between the coating and the substrate, prevent the peeling and crack formation of the coating under strong electrolysis conditions, and ensure the long-term stability and mechanical reliability of the electrode.

[0028] The synergistic effect between the metal element and the metal oxide can not only improve the bonding force of the coating, but also enable the metal element to penetrate and surround the metal oxide, forming a multi-layer structure with a gradient distribution. This structure can not only maintain the porous characteristics of the metal oxide, which is beneficial to the penetration of the electrolyte and the rapid transmission of products, but also the high conductivity of the metal element can improve the overall conductivity of the electrode, reduce the electrochemical impedance, and make the electrode operate efficiently and stably at a high current density.

[0029] It should be noted that in this application, the metal element is particularly selected from one or more of nickel, cobalt and zinc. Metals within this range can not only act as a binder during the laser cladding process, enhancing the bonding force between the coating and the electrode substrate, effectively preventing the coating from peeling off during the electrolysis of water, and improving the stability of the electrode, but also, due to the high electrical conductivity and catalytic activity of nickel, cobalt and zinc themselves, they can promote the progress of electrochemical reactions, especially for the oxygen evolution reaction and hydrogen evolution reaction, thus being conducive to enhancing the catalytic performance of the electrode.

[0030] In summary, for the modified electrode of this application, by constructing a gradient-distributed mixed coating of metal element and metal oxide on the surface of the electrode substrate, the structural stability and catalytic activity of the coating can be balanced, which is conducive to promoting the industrialization process of renewable energy hydrogen production.

[0031] In a preferred embodiment, in the mixed coating, the weight ratio of the metal element to the metal oxide is (1-10):10. Under the above conditions, the metal element inside the coating can act as a "binder" and the metal oxide can act as a "catalyst" more effectively in balance. While further enhancing the bonding force between the coating and the electrode substrate, it can also provide more abundant active sites.

[0032] In a preferred embodiment, in the direction away from the electrode substrate, in the mixed coating, the weight percentage content of the metal oxide increases from 25-50% to 50-75%, and the weight percentage content of the metal element decreases from 50-75% to 25-50%. Under the above conditions, more porous metal oxide active sites can be exposed, which is more conducive to increasing the rate of the electrocatalytic reaction. It can also further increase the structural strength of the coating while ensuring good electrical conductivity, enabling the electrode to remain stable even at a high current density.

[0033] In a preferred embodiment, in the direction away from the electrode substrate, in the mixed coating, the mass concentration growth rate of the metal oxide is 1-5% / μm. This gradient distribution can promote the enrichment of the porous metal oxide on the surface of the coating, which is more conducive to enhancing the catalytic activity of the electrode, optimizing the contact between the electrolyte and the electrode surface, and reducing the reaction overpotential. In a preferred embodiment, in the direction away from the electrode substrate, in the mixed coating, the mass concentration reduction rate of the metal element is 1-5% / μm. This range can ensure a high bonding strength between the bottom of the coating and the substrate, more effectively prevent the coating from peeling off during electrolysis, and guarantee the long-term stability of the electrode.

[0034] In a preferred embodiment, in order to more precisely regulate the interfacial effect between the metal oxide and the electrode substrate, the metal oxide includes one or more oxides of titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, ruthenium, rhodium, palladium, osmium, iridium, and platinum; and / or, the electrode substrate includes one or more of nickel felt, nickel foam, and nickel mesh. Preferably, the porosity of the electrode substrate is 25-75%. The above-mentioned metal oxides have unique chemical properties and porous structures, can combine with metal elements such as nickel, cobalt, and zinc, and cooperate with the electrode substrate to more significantly improve the catalytic activity and stability of the electrode.

[0035] In a preferred embodiment, the thickness of the mixed coating is 10-200 μm; under the above conditions, it can ensure that the coating has sufficient catalytic active sites, and at the same time can avoid the decrease in conductivity caused by the too thick coating, thus facilitating the maintenance of good electrocatalytic performance and the rapid transmission of the electrolyte. In a preferred embodiment, the porosity of the mixed coating is 25-75%. This pore structure not only more facilitates the full contact between the electrolyte and the electrode, but also allows the gas generated by the reaction to escape quickly, effectively preventing the retention of bubbles, thereby further improving the active area and reaction efficiency of the electrode. As mentioned above, the charge transfer efficiency of the coating in this application is fast, and the electrocatalytic activity is high. The electrode containing this coating has fast efficiency and good stability during the alkaline electrolytic water hydrogen production process.

[0036] In another typical embodiment of the present invention, a preparation method of the above-mentioned modified electrode is also provided. The modified electrode includes an electrode substrate and a mixed coating on the surface of the electrode substrate. The mixed coating includes a metal element and a metal oxide. Among them, in the direction away from the electrode substrate, in the mixed coating, the weight percentage content of the metal oxide increases, and the weight percentage content of the metal element decreases; the metal element includes one or more of nickel, cobalt, and zinc. The preparation method includes the following steps: Step S1, mix the raw materials of the metal oxide, then carry out a hydrothermal reaction to obtain a metal compound, and then carry out calcination to obtain a metal oxide; Step S2, mix the metal oxide and the metal element, and carry out ball milling to obtain a metal mixture; Step S3, in the presence of a magnetic field, send a laser beam, and use the magnetic field-assisted laser cladding method to melt the metal mixture, and then deposit it on the surface of the electrode substrate to obtain a modified electrode.

[0037] In the preparation method of the present application, a metal compound is first generated by a hydrothermal reaction, and then the metal compound is decomposed and oxidized by calcination to form a porous metal oxide ball. This structure is conducive to increasing the electrochemical active area and promoting electrolyte penetration and product release. Then, in the ball milling step, the porous metal oxide is mixed with the metal element to achieve high dispersion and uniformity. This process can not only promote the close contact between the metal element and the metal oxide, but also create favorable conditions for the melting of the metal element and the stable bonding of the metal oxide during subsequent laser cladding. Finally, in the magnetic field-assisted laser cladding step, the laser melts the metal element, and the guidance of the magnetic field can control the distribution of the metal element and the metal oxide in the coating, so that the metal oxide is enriched outside the coating, and the porous structure of the metal oxide is retained, while the metal element is concentrated in the inner layer close to the electrode substrate. This process can not only enhance the bonding force between the coating and the substrate, prevent the coating from falling off in the electrolysis of water reaction, but also optimize the internal structure of the metal oxide, fully expose its active sites, and enhance the catalytic activity of the electrode.

[0038] The application of laser cladding technology can ensure uniform cladding of the metal mixture and rapid cooling on the substrate surface, which is conducive to forming a dense and stable coating structure and improving the overall durability and electrocatalytic efficiency of the electrode. The combination of laser cladding and magnetic field assistance is conducive to achieving high activity and high stability of the coating.

[0039] In summary, the modified electrode preparation method of the present application, through the synergistic effect of metal oxides and metal elements, combined with magnetic field-assisted laser cladding technology, can construct a mixed coating with a composition gradient distribution. This method can not only effectively solve the problems of insufficient pore structure and poor coating stability of traditional oxide electrodes, but also significantly improve the catalytic performance and service life of the electrode. In addition, compared with traditional methods of preparing oxide electrodes such as coating calcination and plasma thermal spraying, this application prepares a hydrogen production electrode with catalytic performance and structural strength that meets industrial applications based on porous oxide powders. This preparation method not only has a simple process flow, a wide selection of raw materials, low prices, and is easy to achieve large-scale production, but also can significantly improve the catalytic efficiency and durability of the electrode.

[0040] The inventors further precisely regulated the raw material composition of the metal oxide. In a preferred embodiment, in step S1, the raw materials of the metal oxide include a metal precursor salt, a complexing agent, a precipitating agent, a surfactant, and a solvent. Preferably, the metal precursor salt includes one or more of chloride salts, nitrate salts, sulfate salts, acetate salts, and acetylacetonate salts. Among them, the metal elements include one or more of titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, ruthenium, rhodium, palladium, osmium, iridium, and platinum. The concentration of the metal precursor salt is 0.01-1 mol / L; and / or, preferably, the complexing agent includes one or more of potassium citrate, potassium sodium tartrate, diethanolamine, sodium tripolyphosphate, sodium alginate, and sodium gluconate. The molar ratio of the complexing agent to the metal precursor salt is (0.1-10):1; and / or, preferably, the precipitating agent includes one or more of sodium carbonate, potassium carbonate, sodium oxalate, potassium oxalate, sodium bicarbonate, potassium bicarbonate, sodium hydroxide, and potassium hydroxide. The molar ratio of the precipitating agent to the metal precursor salt is (0.1-10):1; and / or, preferably, the surfactant includes one or more of polyvinyl alcohol, cetyltrimethylammonium bromide, polyethyleneimine, polyvinyl alcohol ether, sodium octenylbenzenesulfonate, polyglutamic acid, chitosan, and sodium dodecyl sulfate. The molar ratio of the surfactant to the metal precursor salt is (0.1-10):1; and / or, preferably, the solvent includes one or more of water, ethanol, and ether. Under the above conditions, not only can the formation of the metal oxide be promoted, but also its microstructure can be optimized, significantly improving the electrochemical performance. In a preferred embodiment, during the hydrothermal reaction process, the volume content of the mixture of the metal oxide raw materials in the hydrothermal equipment is 20-75%.

[0041] In a preferred embodiment, the temperature of the hydrothermal reaction is 120-180 °C, and the time is 2-24 h. Under the above conditions, the chemical reaction between the metal precursor salt, the complexing agent, the precipitating agent, and the surfactant can be further promoted, ensuring the full generation and transformation of the compound, more effectively avoiding incomplete reactions, and at the same time, in the above environment, it is more conducive to the formation of spherical metal compound precipitates.

[0042] In order to further reduce the impurity content in the spherical metal compound precipitate, in a preferred embodiment, step S1 further includes the steps of washing, suction filtration, and first drying of the metal compound; preferably, the metal compound is washed 4 times in sequence with water, ethanol, acetone, and water; preferably, the first drying is carried out by blowing drying or vacuum drying, and the drying temperature is 60-100 °C, and the time is 1-12 h. Under the above conditions, the residual surfactant, precursor salt, and precipitating agent in the precipitate product can be effectively removed.

[0043] In order to more fully convert the spherical metal compound precipitate into a metal oxide with a high specific surface area, high porosity, high stability and porous structure, in a preferred embodiment, the metal compound precipitate is calcined at a temperature of 300 to 500°C for 2 to 4 hours in an atmosphere of one or more of air, oxygen and nitrogen. Under the above conditions, it is more conducive to increasing the density of its catalytic active sites and avoiding structural collapse caused by excessively high temperatures.

[0044] In order to further enhance the electrode coating bonding and optimize the internal structure, thereby further improving the electrode stability and catalytic efficiency, in a preferred embodiment, in step S2, the particle size of the metal element is 100-500 mesh; under this condition, the dispersion of the metal element in the ball milling mixing process can be further increased to form a more uniform coating cladding raw material, which is more conducive to increasing the uniformity and stability of the internal structure of the coating, and / or, the weight ratio of the metal element to the metal oxide is (0.01-1):1. Under the above conditions, the coating bonding strength and catalytic activity can be balanced, which is more conducive to avoiding the shielding of active sites caused by excessive metal elements, while also ensuring more sufficient metal connections, further improving the adhesion of the coating on the electrode substrate.

[0045] In order to further improve the homogenization and dispersion of the metal mixture, thereby being more conducive to improving the bonding strength and catalytic activity of the coating, in a preferred embodiment, the ball milling speed is 150-500 rpm, and the time is 0.5-10 h; preferably, 10-30 mm zircon beads are used as ball milling beads for ball milling; and / or, step S2 also includes adding a dispersant during the ball milling process, and performing a second drying step on the metal mixture; preferably, the amount of the dispersant added is 10-50% of the metal element in terms of weight percentage, and the dispersant includes one or more of ethanol, pentane and acetone; preferably, the second drying is forced air drying, the temperature is 25-60°C, and the time is 0.5-24 h.

[0046] In order to further enhance the bonding strength of the coating and expose the active sites more fully, in a preferred embodiment, the strength of the magnetic field is 0.001 to 0.1 T. Under the above conditions, the fluidity of the metal element and the distribution of the metal oxide particles can be more effectively optimized, and the molten metal of the metal element during the laser cladding process can be guided to be more concentrated on the surface of the electrode substrate, thereby forming a stronger bond between the coating and the substrate, preventing the coating from peeling off during the electrolysis of water, and further enhancing the mechanical stability of the electrode.

[0047] In order to further optimize the distribution of metal oxides, in a preferred embodiment, the angle between the direction of the magnetic field and the perpendicular direction of the electrode substrate surface is ≤10°, preferably, the angle is ≤5°. Under the above conditions, a gradient distribution can be formed inside the coating, which promotes the porous metal oxide spheres to be more fully distributed in the outer layer of the coating, further increasing the electrochemical active area, while maintaining the density of the metal element at the substrate interface, and enhancing the stability and conductivity of the coating.

[0048] For the purpose of further optimizing the distribution of metal elements and metal oxide particles, in a preferred embodiment, the magnetic field is applied from the side of the electrode substrate away from the mixed coating. Under the above conditions, the metal elements can form a more uniform and dense connection between the electrode substrate and the oxide, and at the same time, the internal structure of the metal oxide can be more effectively prevented from being excessively affected, and the integrity of its porous network can be maintained, which is more conducive to the improvement of catalytic activity. In a preferred embodiment, the magnetic field originates from an electromagnet or a permanent magnet.

[0049] In order to further improve the uniformity and stability of the coating, and promote the formation and retention of the porous structure of the metal oxide, in a preferred embodiment, in step S3, the focal diameter of the laser beam is 100-500 μm, and the distance between the nozzle that sends the laser beam and the side of the electrode substrate close to the mixed coating is 10-30 mm. Under the above conditions, the efficient use of laser energy can be ensured, so that the metal oxides and metal elements in the cladding process can be melted more evenly to form a denser and more solid mixed coating, thereby further enhancing the bonding between the electrode substrate and the coating, preventing the coating from peeling off in the electrolytic environment, and further improving the mechanical stability and service life of the electrode.

[0050] In a preferred embodiment, the atmosphere for sending the laser beam includes one or more of argon, helium and carbon dioxide, and the gas flow rate is 5 to 20 L / min. Under the above conditions, not only can an oxygen-free and pollution-free cladding environment be created to prevent the added metal element from being oxidized at high temperature, so that it maintains good bonding with the metal, but also the inert gas can take away the heat and smoke generated by the cladding process, prevent the heat-affected zone from being too large, and is more conducive to improving the integrity of the electrode substrate and the uniformity of the coating.

[0051] In a preferred embodiment, the laser power is 1000-2500 W. Under this condition, the metal element can be melted more quickly, promoting its combination with the oxide particles to form a more stable interface; the cladding rate of the metal oxide and / or the metal element is 0.1-0.25 m / min. Under this condition, the coating can be fully melted and quickly solidified to avoid cracks inside the coating, and the porous structure of the oxide can be more effectively maintained, thereby further increasing the electrochemical active area and improving the catalytic efficiency.

[0052] For the purpose of further improving the stability of the coating and the catalytic performance of the electrode, in a preferred embodiment, in step S3, the metal mixture is fed into the reaction system through an inert gas, and the inert gas includes argon and / or helium, and the gas flow rate is 1-5 L / min; under the above conditions, a pure inert atmosphere can be provided for laser cladding, which is more conducive to preventing the oxidation and pollution of materials during the cladding process, and ensuring the chemical stability and electrochemical activity of the coating; and / or, the feeding rate of the metal mixture is 0.03-0.1 g / mm; under the above conditions, the uniform cladding of the coating raw materials can be ensured, and the performance degradation caused by too thick or too thin coatings can be avoided, thereby making the binding force of the coating stronger and the catalytic activity higher. In a preferred embodiment, the heat input in the laser cladding method is 400-600 J / mm. Under the above conditions, the melting and solidification of the material can be more precisely controlled, the close combination of the metal oxide and the substrate can be promoted, and at the same time, the porous structure of the oxide can be retained, which is more conducive to improving the catalytic efficiency and mechanical strength of the electrode.

[0053] In another typical embodiment of the present invention, the application of the above modified electrode in the field of water electrolysis is also provided. As mentioned above, through the magnetic field-assisted laser cladding technology, the present application successfully prepares an electrode with a coating having a gradient distribution, which is beneficial to significantly improving the catalytic activity and stability of the electrode. In the field of water electrolysis, the electrode of the present application can greatly reduce the reaction overpotential, improve the electrolysis efficiency, reduce the energy consumption, and at the same time, its stable binding force and porous structure can ensure the reliable performance under long-term operation, providing a high-performance and low-cost solution for the alkaline water electrolysis hydrogen production technology, and promoting the industrialization process of the renewable energy hydrogen production technology.

[0054] The following further describes the present application in detail with specific embodiments, and these embodiments should not be construed as limiting the scope claimed by the present application.

[0055] Example 1

[0056] The schematic diagram of the preparation process of the modified electrode is shown in Figure 1 。

[0057] Step S1, prepare an aqueous solution composed of 0.1 mol / L cobalt chloride, 0.12 mol / L potassium citrate, 0.12 mol / L sodium oxalate and 0.05 mol / L polyvinyl alcohol, with a volume of 100 mL. Add the above solution to a 150 mL polytetrafluoroethylene-lined hydrothermal autoclave. The proportion of the aqueous solution in the hydrothermal autoclave is 66.7%, the hydrothermal temperature is 150 °C, and the hydrothermal time is 3 h. The product is separated and filtered by suction filtration, and the powder is washed 4 times with water, ethanol, acetone, and water respectively, and then the powder is dried by blowing air, with a drying temperature of 60 °C and a time of 2 h to obtain spherical cobalt oxalate particles.

[0058] The spherical metal compound is calcined in a flowing air atmosphere at a temperature of 350 °C for 2.5 h, and the cooling method after calcination is natural cooling to obtain porous metal cobalt oxide spheres.

[0059] In step S2, 50 g of porous metal cobalt oxide spheres are mixed with 25 g of metal nickel powder with a particle size of 500 mesh, and then ball-milled and mixed at a rotation speed of 250 rpm for 2 h. Zirconium beads with a diameter of 20 mm are selected, and then the mixed powder is taken out and dried by blowing at a temperature of 60 °C for 6 h.

[0060] In step S3, the above-mentioned mixed powder is melted by means of magnetic field-assisted laser cladding and attached to the surface of a nickel felt with a porosity of 80% through gas. The focal diameter of the laser beam is 200 μm, which is set 20 mm above the substrate surface. The shielding gas is argon with a flow rate of 10 L / min; the powder delivery gas is argon with a flow rate of 2 L / min. The powder in the laser cladding process is directly injected into the molten pool. A single-channel coating with a laser power of 2000 W, a cladding speed of 0.2 m / min, a powder feeding rate of 0.06 g / mm, and a heat input of 450 J / mm is obtained. The magnetic field is sourced from a magnet, and the magnetic field is applied from the side of the electrode substrate away from the mixed coating. The applied magnetic field intensity is 0.05 T, and the angle between the direction of the magnetic field and the perpendicular direction of the electrode substrate surface is 0°, obtaining a modified electrode.

[0061] The schematic diagram of the principle of the modified electrode during the preparation by magnetic field-assisted laser cladding method is shown in Figure 2 , and the micrograph of the modified electrode at a magnification of 200 times is shown in Figure 3 , and the micrograph at a magnification of 20,000 times is shown in Figure 4 . It can be seen from the figure that during the preparation process, the metal element 2 (the magnetic molten nickel coating) is concentrated on the surface of the electrode substrate 1 (nickel substrate) under the action of the magnetic field and cooled. At the same time, more porous spherical metal oxides 3 on the surface are exposed, and a coating with a component gradient distribution is formed after cooling and solidification.

[0062] Example 2

[0063] The difference from Example 1 is only that: the raw materials of the metal oxide are different.

[0064] 0.1 mol / L cobalt chloride is replaced by 0.05 mol / L cobalt chloride and 0.05 mol / L iron chloride.

[0065] Example 3

[0066] The difference from Example 1 is only that: the raw materials of the metal oxide are different.

[0067] Replace 0.1 mol / L cobalt chloride with 0.025 mol / L cobalt chloride, 0.025 mol / L iron chloride, 0.025 mol / L copper chloride, and 0.025 mol / L nickel chloride.

[0068] Example 4

[0069] The difference from Example 1 is only that: the structure of the electrode substrate is different.

[0070] Replace the nickel felt with 80% porosity with a 46-mesh nickel mesh.

[0071] Example 5

[0072] The difference from Example 1 is only that: the raw material of the metallic element is metallic cobalt powder with a particle size of 100 mesh.

[0073] Example 6

[0074] The difference from Example 1 is only that: the magnetic field is sourced from an electromagnet, the intensity of the magnetic field is 0.001 T, and the angle between the direction of the magnetic field and the perpendicular direction of the electrode substrate surface is 0°.

[0075] Example 7

[0076] The difference from Example 1 is only that: the magnetic field is sourced from an electromagnet, the intensity of the magnetic field is 0.1 T, and the angle between the direction of the magnetic field and the perpendicular direction of the electrode substrate surface is 10°.

[0077] Example 8

[0078] The difference from Example 1 is only that:

[0079] The diameter of the laser beam focus is 100 μm, set 10 mm above the substrate surface, the shielding gas is argon with a flow rate of 5 L / min; the powder delivery gas is argon with a flow rate of 1 L / min, and the powder during the laser cladding process is directly injected into the molten pool. A single-channel coating with a laser power of 1000 W, a cladding speed of 0.1 m / min, a powder feed rate of 0.03 g / mm, and a heat input of 400 J / mm.

[0080] Example 9

[0081] The difference from Example 1 is only that:

[0082] The diameter of the laser beam focus is 500 μm, set 30 mm above the substrate surface, the shielding gas is helium with a flow rate of 20 L / min; the powder delivery gas is helium with a flow rate of 5 L / min, and the powder during the laser cladding process is directly injected into the molten pool. A single-channel coating with a laser power of 2500 W, a cladding speed of 0.25 m / min, a powder feed rate of 0.1 g / mm, and a heat input of 600 J / mm.

[0083] Example 10

[0084] The difference from Example 1 is only that:

[0085] Step S1, prepare an aqueous solution composed of 0.1 mol / L nickel chloride, 0.15 mol / L potassium sodium tartrate, 0.2 mol / L potassium carbonate and 0.05 mol / L sodium dodecyl sulfate, with a volume of 100 mL. Add the above solution to a 150 mL polytetrafluoroethylene-lined hydrothermal autoclave. The proportion of the aqueous solution in the hydrothermal autoclave is 66.7%. The hydrothermal temperature is 120 °C and the hydrothermal time is 24 h. Use suction filtration to separate and filter the product, wash the powder 4 times with water, ethanol, acetone, and water respectively, and then perform blast drying on the powder. The drying temperature is 100 °C and the time is 2 h to obtain spherical nickel carbonate.

[0086] Calcine the spherical metal compound in a flowing air atmosphere at a temperature of 300 °C for 4 h, and the cooling method after calcination is natural cooling to obtain porous metal nickel oxide spheres.

[0087] Step S2, mix 75 g of porous metal nickel oxide spheres with 25 g of metal nickel powder with a particle size of 500 mesh, and then perform ball milling. The rotation speed of the ball milling is 150 rpm and the time is 10 h. Select 10 mm zirconia beads, and then take out the mixed powder for blast drying. The temperature is 25 °C and the time is 24 h.

[0088] Example 11

[0089] The difference from Example 1 is only that:

[0090] Step S1, prepare an aqueous solution composed of 0.1 mol / L ruthenium acetylacetonate, 0.2 mol / L sodium tripolyphosphate, 0.3 mol / L sodium bicarbonate and 0.1 mol / L polyglutamic acid, with a volume of 100 mL. Add the above solution to a 150 mL polytetrafluoroethylene-lined hydrothermal autoclave. The proportion of the aqueous solution in the hydrothermal autoclave is 66.7%. The hydrothermal temperature is 180 °C and the hydrothermal time is 2 h. Use suction filtration to separate and filter the product, wash the powder 4 times with water, ethanol, acetone, and water respectively, and then perform blast drying on the powder. The drying temperature is 40 °C and the time is 5 h to obtain spherical ruthenium bicarbonate particles.

[0091] Calcine the spherical metal compound in a flowing air atmosphere at a temperature of 500 °C for 2 h, and the cooling method after calcination is natural cooling to obtain porous metal ruthenium oxide spheres.

[0092] Step S2: Mix 25 g of porous cobalt oxide spheres with 25 g of nickel powder with a particle size of 500 mesh, and then perform ball milling. The rotation speed of the ball milling is 500 rpm, and the time is 0.5 h. Select zirconia beads with a diameter of 30 mm. Then take out the mixed powder and perform air drying at a temperature of 60 °C for 0.5 h.

[0093] Comparative Example 1

[0094] The difference from Example 1 is only that: during the laser cladding process, there is no magnetic field assistance. The schematic diagram of the principle of the electrode during the preparation by laser cladding method is shown in Figure 5 .

[0095] Comparative Example 2

[0096] The difference from Example 1 is only that: without magnetic field assistance, using the conventional calcination method, after mixing porous cobalt oxide and nickel metal, it is loaded on the surface of a nickel felt with a porosity of 80% by calcination at 800 °C for 5 h.

[0097] Comparative Example 3

[0098] The difference from Example 1 is only that: without magnetic field assistance, using the conventional coating and sintering method, the aqueous solution prepared in S1 is directly coated on the surface of a nickel felt with a porosity of 80%, and then loaded by calcination at 800 °C for 5 h.

[0099] Comparative Example 4

[0100] The difference from Example 1 is only that: directly calcine 0.01 mol of cobalt chloride in a flowing air atmosphere to obtain cobalt oxide particles with an irregular morphology.

[0101] Comparative Example 5

[0102] An electrode, wherein the cathode catalyst for electrolytic water is 40 wt% Pt / C (model HiSPEC4000), the anode catalyst is IrO x (model I811643), the AEM is FAA-3-50, and the loadings of the cathode and anode catalysts on the AEM are both 2 mg / cm 2 .

[0103] Test method:

[0104] Alkaline electrolytic water system: Cut out a cuboid with a length of 1.5 cm and a width of 1 cm from the electrodes obtained in each of the examples and comparative examples, and use an electrode clamp to fix it as the working electrode for the oxygen evolution reaction (OER) in the alkaline electrolyte. In a three-electrode test system, a platinum wire is used as the counter electrode, and a mercury / mercuric oxide electrode is used as the reference electrode. The effective area of the working electrode immersed in the electrolyte is 1 cm 2, 1 mol / L potassium hydroxide was selected as the electrolyte for the test system. During the test, linear voltammetry scanning and AC impedance method were used to test the electrochemical data. The scanning rate of linear voltammetry was 5 mV / s, the test potential of AC impedance was 1.53 V (vs. RHE), the AC amplitude was 10 mV, and the frequency range was 10 6 ~10 -1 Hz. The overpotential of each electrode at a current density of 100 mA / cm 2 was obtained. The smaller the value, the faster the charge transfer between the electrode interface and the electrolyte, indicating higher oxygen evolution catalytic activity.

[0105] Anion exchange membrane electrolyzed water system: The electrodes obtained in each example and comparative example were used as self-supported electrodes directly for the cathode and anode gas diffusion layers of the anion exchange membrane (AEM) electrolyzer. The AEM selected was the commercial membrane FAA-3-50. During the test, the electrode clips of the electrochemical workstation were respectively clamped on the anode and cathode of the electrolytic cell, and 1 M KOH solution was circulated at a flow rate of 100 ml / min. The heating device was turned on and the temperature was set at 60 °C. The cell voltage of each sample when reaching a current density of 2.5 A / cm 2 was obtained. It represents the hydrogen production voltage value of a single electrolysis unit when reaching a certain current density. Therefore, the lower the value, the lower the energy consumption at the current density and the higher the economy of the hydrogen production reaction. Among them, the voltage decay value during the operation at a current density of 1 A / cm 2 for 100 h was used to represent the stability of the electrode.

[0106] The test results of the modified electrodes prepared in the above examples and comparative examples are shown in Table 1.

[0107] Table 1

[0108]

[0109]

[0110] It can be analyzed that compared with Example 1, in Example 2, an electrode with binary metal oxide as the active component was prepared, and the electronic interaction between transition metals was strong and the activity was high. In Example 3, an electrode with binary metal oxide as the active component was prepared, and the electronic interaction between transition metals was enhanced. At the same time, it was also proved that the types and quantities of elements of the catalytic active components in the synthesis method of the present invention have universality. In Example 4, an electrode with a nickel mesh as the substrate was prepared, which has excellent performance, proving the universality of the synthesis method of the present invention for the selection of electrode substrates. Example 5 shows that the particle size of the metal single powder affects the dispersion effect of the metal single in the coating.

[0111] Example 6 shows that the intensity of the magnetic field affects the distribution of the component gradient constructed in the coating. Example 7 shows that the intensity of the magnetic field and the angle between the magnetic field and the substrate affect the concentration and uniformity of the metal components on the surface of the nickel substrate, as well as the connection effect between the oxides, thereby affecting the conductivity and structural stability of the coating.

[0112] Example 8 shows that the laser focal distance affects the stability of the nickel felt substrate.

[0113] Example 9 shows that the size of the laser focus and the distance from the substrate affect the powder cladding effect and the coating structure strength.

[0114] Example 10 shows that the mass ratio between the porous metal oxide and the metal nickel and the metal nickel content affect the connection between the metal oxides.

[0115] Example 11 shows that the noble metal ruthenium has high intrinsic activity and excellent water electrolysis performance, and also proves that the method of the present invention is also applicable to the synthesis of noble metal type electrodes.

[0116] Compared with Example 1, there is no magnetic field assistance in Comparative Example 1, so a structure in which the metal and oxide components are gradiently distributed in the coating cannot be formed; Comparative Example 2 uses a conventional calcination method to load active components. Since high-temperature calcination will cause the porous structure to collapse and there is no gradient distribution structure of the metal and oxide components in the coating formed by calcination, the performance is poor and the structure is unstable; Comparative Example 3 uses a conventional coating and sintering method, and the precursor salt solution is directly coated on the electrolytic surface for thermal decomposition. The surface can form an oxide but does not have a porous structure. At the same time, without adding metallic nickel, the bonding force of the coating is poor; In Comparative Example 4, the precursor salt is directly coated and thermally decomposed on the surface of the metal substrate, resulting in the synthesized oxide having no porous structure and a small number of catalytic active sites. Since the oxide does not have a spherical morphology, it will also lead to a decrease in the fluidity of the catalyst powder feeding in the laser cladding process, and the uneven powder output causes the coating thickness and component uniformity to deteriorate.

[0117] From the above, it can be seen that the present invention constructs a gradient distributed mixed coating of metal elements and metal oxides on the surface of the electrode substrate. The synergistic effect of metal oxides and metal elements not only effectively solves the problems of insufficient pore structure and poor coating stability of traditional oxide electrodes, but also significantly improves the catalytic performance and service life of the electrode.

[0118] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A modified electrode, characterized in that, It includes an electrode substrate and a mixed coating distributed on the surface of the electrode substrate. The mixed coating includes elemental metal and metal oxide. Among them, in the direction away from the electrode substrate, in the mixed coating, the weight percentage content of the metal oxide increases, and the weight percentage content of the elemental metal decreases. The elemental metal includes one or more of nickel, cobalt, and zinc.

2. The modified electrode according to claim 1, wherein in the mixed coating, the weight ratio of the elemental metal to the metal oxide is (1-10):10; and / or in the direction away from the electrode substrate, in the mixed coating, the weight percentage content of the metal oxide increases from 25-50% to 50-75%, and the weight percentage content of the elemental metal decreases from 50-75% to 25-50%.

3. The modified electrode according to claim 2, wherein in the direction away from the electrode substrate, in the mixed coating, the mass concentration growth rate of the metal oxide is 1-5% / μm.

4. The modified electrode according to claim 2, wherein in the direction away from the electrode substrate, in the mixed coating, the mass concentration reduction rate of the elemental metal is 1-5% / μm.

5. The modified electrode according to claim 1 or 2, wherein the metal oxide includes oxides of one or more of titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, ruthenium, rhodium, palladium, osmium, iridium, and platinum; and / or the electrode substrate includes one of nickel felt, nickel foam, and nickel mesh.

6. The modified electrode according to claim 5, wherein the porosity of the electrode substrate is 25-75%.

7. The modified electrode according to claim 1 or 2, wherein the thickness of the mixed coating is 10-200μm; and / or the porosity of the mixed coating is 25-75%.

8. The preparation method of the modified electrode according to any one of claims 1 to 7, characterized in that, The modified electrode includes an electrode substrate and a mixed coating on the surface of the electrode substrate. The mixed coating includes elemental metal and metal oxide. Among them, in the direction away from the electrode substrate, in the mixed coating, the weight percentage content of the metal oxide increases, and the weight percentage content of the elemental metal decreases. The elemental metal includes one or more of nickel, cobalt, and zinc. The preparation method includes the following steps: Step S1: Mix the raw materials of the metal oxide, then carry out a hydrothermal reaction to obtain a metal compound, and then carry out calcination to obtain the metal oxide. Step S2: Mix the metal oxide and the elemental metal and carry out ball milling to obtain a metal mixture. Step S3: In the presence of a magnetic field, send a laser beam, and use the magnetic field-assisted laser cladding method to melt the metal mixture and then deposit it on the surface of the electrode substrate to obtain the modified electrode.

9. The preparation method according to claim 8, wherein In the step S1, the raw materials of the metal oxide include metal precursor salts, complexing agents, precipitants, surfactants, and solvents; and / or the temperature of the hydrothermal reaction is 120-180°C, and the time is 2-24h; and / or The step S1 further comprises the steps of washing, filtering and first drying the metal compound; and / or, The calcination temperature is 300-500° C., the calcination time is 2-4 hours, and the atmosphere is one or more of air, oxygen and nitrogen.

10. The preparation method according to claim 9, characterized in that: The metal precursor salt includes one or more of metal chlorides, nitrates, sulfates, acetates and acetylacetonates; the metal includes one or more of titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, ruthenium, rhodium, palladium, osmium, iridium and platinum; and the concentration of the metal precursor salt is 0.01 to 1 mol / L.

11. The preparation method according to claim 9, characterized in that: The complexing agent includes one or more of potassium citrate, potassium sodium tartrate, diethanolamine, sodium tripolyphosphate, sodium alginate and sodium gluconate, and the molar ratio of the complexing agent to the metal precursor salt is (0.1-10):

1.

12. The preparation method according to claim 9, characterized in that: The precipitant includes one or more of sodium carbonate, potassium carbonate, sodium oxalate, potassium oxalate, sodium bicarbonate, potassium bicarbonate, sodium hydroxide and potassium hydroxide, and the molar ratio of the precipitant to the metal precursor salt is (0.1-10):

1.

13. The preparation method according to claim 9, characterized in that: The surfactant includes one or more of polyvinyl alcohol, hexadecyltrimethylammonium bromide, polyethyleneimine, polyvinyl alcohol ether, sodium octenylbenzenesulfonate, polyglutamic acid, chitosan and sodium dodecyl sulfate, and the molar ratio of the surfactant to the metal precursor salt is (0.1-10):

1.

14. The preparation method according to claim 9, characterized in that: The solvent includes one or more of water, ethanol and ether.

15. The preparation method according to claim 9, characterized in that: The metal compound was washed four times with water, ethanol, acetone and water in sequence.

16. The preparation method according to claim 9, characterized in that: The first drying is performed by air drying or vacuum drying, the drying temperature is 60 to 100° C., and the time is 1 to 12 hours.

17. The preparation method according to claim 8 or 9, characterized in that, In the step S2, The particle size of the metal element is 100 to 500 mesh; and / or, the weight ratio of the metal element to the metal oxide is (0.01 to 1):1; and / or, The ball milling speed is 150-500 rpm, and the time is 0.5-10 h; and / or, The step S2 further includes adding a dispersant during the ball milling process and performing a second drying step on the mixture.

18. The preparation method according to claim 17, characterized in that: The ball milling is performed using zircon beads with a diameter of 10 to 30 mm as ball milling beads.

19. The preparation method according to claim 17, characterized in that: Calculated by weight percentage, the added amount of the dispersant is 10-50% of the metal element, and the dispersant includes one or more of ethanol, pentane and acetone.

20. The preparation method according to claim 17, characterized in that: The second drying is hot air drying, with a temperature of 25 to 60 °C and a time of 0.5 to 24 h.

21. The preparation method according to claim 8 or 9, characterized in that, In the step S3, the intensity of the magnetic field is 0.001 to 0.1 T; and / or, the included angle between the direction of the magnetic field and the perpendicular direction of the surface of the electrode substrate is ≤ 10°; and / or, the magnetic field is applied from the side of the electrode substrate away from the mixed coating.

22. The preparation method according to claim 21, wherein the magnetic field is derived from an electromagnet or a permanent magnet.

23. The preparation method according to claim 8 or 9, characterized in that, In the step S3, the focal diameter of the laser beam is 100 to 500 μm, and the distance between the nozzle for emitting the laser beam and the side of the electrode substrate close to the mixed coating is 10 to 30 mm; and / or, the atmosphere for emitting the laser beam includes one or more of argon, helium, and carbon dioxide, and the gas flow rate is 5 to 20 L / min; and / or, the laser power is 1000 to 2500 W, and the cladding rate of the metal oxide and / or the metal element is 0.1 to 0.25 m / min; and / or, the metal mixture is fed into the reaction system through an inert gas, and the inert gas includes argon and / or helium, and the gas flow rate is 1 to 5 L / min; and / or, the feeding rate of the metal mixture is 0.03 to 0.1 g / mm; and / or, the heat input in the laser cladding method is 400 to 600 J / mm.

24. Application of the modified electrode according to any one of claims 1 to 7 in the field of electrolytic water.

Images