A high-efficiency multilayer metal mesh electrode for water electrolysis and its preparation method

Abstract

This invention relates to a high-efficiency multilayer metal mesh electrode for water electrolysis and its preparation method, comprising: preparing at least two layers of metal mesh, wherein the pore size of each layer of metal mesh increases sequentially from the inner layer closest to the diaphragm to the outer layer furthest from the diaphragm; performing surface treatment on each layer of metal mesh to make the hydrophilicity of the inner layer of metal mesh higher than that of the outer layer of metal mesh; sequentially stacking the layers of metal mesh and hot-pressing sintering under vacuum or an inert atmosphere, so that the layers of metal mesh are bonded together as a whole through intermetallic diffusion, thereby obtaining a multilayer metal mesh electrode. This invention, through the structural combination of multilayer metal meshes, creates a gradient difference in mesh count, wire diameter, and hydrophilicity, constructing a directional transport channel for bubbles from the inner to the outer layers. After bubbles are generated in the inner layer, they can migrate sequentially to the outer layer and be carried away by the flow field, effectively avoiding bubble retention and local shading, significantly reducing voltage loss under high current density, and improving electrolysis efficiency.

Description

Technical Field

[0001] This invention relates to the field of electrode technology, specifically to a high-efficiency multilayer metal mesh electrode for water electrolysis and its preparation method. Background Technology

[0002] In energy conversion fields, such as water electrolysis for hydrogen production, the performance of electrode materials is crucial. Metal meshes (such as commercial nickel mesh) are commonly used electrode substrate materials, and their performance largely depends on the microstructure of their surface. Metal wires with micro / nano-scale rough surfaces can significantly increase the specific surface area of ​​the electrode, provide more catalytic active sites, and enhance the adhesion of the catalyst layer, thereby improving the activity and stability of the electrode.

[0003] Currently, surface roughening of metal meshes typically employs monolithic immersion electrochemical etching. This method has significant drawbacks: 1. Uneven processing: The metal mesh has a complex structure. During the overall etching process, the current density is unevenly distributed in different parts of the mesh wire, such as intersections and the middle part, resulting in different etching degrees and making it difficult to obtain a uniform rough surface.

[0004] 2. Inefficient: It requires processing the entire metal mesh, which is time-consuming, energy-intensive, and requires a large volume of etching solution.

[0005] 3. Poor controllability: It is difficult to accurately control the etching process in real time, which can easily lead to over-etching or under-etching in some areas.

[0006] Therefore, there is an urgent need for a new method that can uniformly, efficiently, and controllably roughen the surface of the metal wires that make up the metal mesh. Summary of the Invention

[0007] To address the problems of bubble retention, large voltage loss, easy catalyst layer detachment, and insufficient structural stability in existing alkaline water electrolysis electrodes, the present invention aims to provide a multilayer metal mesh electrode design method with high degassing efficiency. This method achieves directional removal and efficient migration of bubbles through the structural combination and surface control of the multilayer metal mesh, thereby reducing voltage loss, improving reaction stability, and extending electrode lifespan.

[0008] The objective of this invention can be achieved through the following technical solutions: One objective of this invention is to provide a method for preparing a multilayer metal mesh electrode for water electrolysis with high exhaust efficiency, comprising the following steps: (1) Prepare at least two layers of metal mesh, with the aperture of each layer of metal mesh increasing sequentially from the inner layer of metal mesh closest to the diaphragm to the outer layer of metal mesh furthest from the diaphragm; (2) Surface treatment is performed on each layer of metal mesh to make the hydrophilicity of the inner layer of metal mesh higher than that of the outer layer of metal mesh, forming a gradient distribution in which the hydrophilicity decreases from the inner layer to the outer layer. (3) The metal mesh layers processed in step (2) are stacked in order from the inside to the outside, and hot-pressed and sintered in a vacuum or inert atmosphere so that the metal mesh layers are combined into a whole through intermetallic diffusion to obtain the multilayer metal mesh electrode.

[0009] Furthermore, the metal mesh has three layers, namely, an inner metal mesh A, a middle metal mesh B, and an outer metal mesh C, arranged sequentially from the side closest to the diaphragm outwards. The three metal meshes form a continuous gradient from the inside to the outside in terms of pore size and hydrophilicity.

[0010] Furthermore, the inner metal mesh A has a mesh count of 100–500 and a wire diameter of 30–80 μm; the middle metal mesh B has a mesh count of 40–100 and a wire diameter of 80–150 μm; and the outer metal mesh C has a mesh count of 10–30 and a wire diameter of 200–400 μm.

[0011] Furthermore, the inner metal mesh A is made of nickel-molybdenum alloy, with a Ni to Mo mass ratio of 9.5:0.5 to 5.0:3.0; the middle metal mesh B is made of nickel-molybdenum alloy, with a Ni to Mo mass ratio of 7.0:3.0 to 3.0:7.0; and the outer metal mesh C is made of pure nickel or nickel-molybdenum alloy, with a Ni to Mo mass ratio of not less than 9:1.

[0012] Furthermore, the surface treatment of the metal mesh is an electrochemical etching process, the etching solution is a hydrochloric acid solution, the etching intensity of the inner metal mesh is greater than that of the middle metal mesh, and the outer metal mesh is not etched or only surface cleaned.

[0013] Furthermore, the conditions for electrochemical etching of the inner metal mesh A are: hydrochloric acid concentration 0.1–1 M, current density 10–100 mA / cm². 2 The etching time was 100–1000 s; the conditions for electrochemical etching of the intermediate metal mesh B were: hydrochloric acid concentration 0.5–3 M, current density 100–500 mA / cm². 2 The etching time is 10–500 s; the outer metal mesh C is not etched, or is only cleaned by ultrasonic cleaning.

[0014] Furthermore, after electrochemical etching, a nanoscale rough structure is formed on the surface of the inner metal mesh A, a micron-scale rough structure is formed on the surface of the middle metal mesh B, and the outer metal mesh C retains a smooth surface.

[0015] Furthermore, the process parameters for hot pressing sintering in step (3) are: sintering temperature 1000~1250 ℃, compression ratio 10%~30% of the initial total thickness, and holding time 10~60 min.

[0016] The second objective of this invention is to provide a high-efficiency multilayer metal mesh electrode for water electrolysis. This electrode is integrally formed by hot-pressing and sintering at least two layers of metal mesh. From the side closest to the diaphragm outwards, the pore size of each metal mesh layer increases sequentially, and the hydrophilicity of the surface of each metal mesh layer decreases sequentially, forming a pore size gradient and a hydrophilicity gradient from the inside to the outside. The pore size gradient and the hydrophilicity gradient together constitute a channel that guides the directional transport of bubbles from the inner layer to the outer layer.

[0017] Furthermore, the electrode is composed of three layers of metal mesh, which, from the side closest to the diaphragm outwards, are an inner metal mesh A, a middle metal mesh B, and an outer metal mesh C: The inner metal mesh A has a mesh count of 100–500 mesh, a wire diameter of 30–80 μm, and is made of a nickel-molybdenum alloy with a Ni:Mo mass ratio of 9.5:0.5–5.0:3.0, with a nanoscale rough structure on its surface. The middle layer metal mesh B has a mesh count of 40-100 mesh, a wire diameter of 80-150 μm, and is made of a nickel-molybdenum alloy with a Ni:Mo mass ratio of 7.0:3.0 to 3.0:7.0, with a surface rough structure at the micron level. The outer metal mesh C has a mesh count of 10 to 30, a wire diameter of 200 to 400 μm, and is made of pure nickel or a nickel-molybdenum alloy with a Ni:Mo mass ratio of not less than 9:1. The surface is smooth. Among them, the underwater bubble contact angle of the inner metal mesh A is not less than 150°, the underwater bubble contact angle of the middle metal mesh B is between that of the inner metal mesh A and the outer metal mesh C, and the underwater bubble contact angle of the outer metal mesh C is lower than that of the inner metal mesh A.

[0018] Compared with existing single-layer nickel electrodes or coated composite electrodes, the present invention has the following significant advantages: (1) Reasonable structural design and high exhaust efficiency. This invention uses a multi-layer metal mesh structure to create gradient differences in mesh count, wire diameter and hydrophilicity, thus constructing a directional transport channel for bubbles from the inner layer to the outer layer. After being generated in the inner layer, the bubbles can migrate sequentially to the outer layer and be carried away by the flow field, effectively avoiding bubble retention and local shading, significantly reducing voltage loss under high current density and improving electrolysis efficiency.

[0019] (2) The preparation process is simple and the cost is low. This invention does not require complex processes such as electrodeposition, spraying or chemical vapor deposition. Instead, it can be completed by mechanical weaving, electrochemical etching and vacuum hot pressing sintering. The process is short, highly repeatable and suitable for large-scale production.

[0020] (3) Stable structure and long service life. The three-layer metal mesh provided by the present invention forms an integral metal bond after vacuum hot pressing, without coating interface and bonding layer peeling problems. The electrode structure is stable during long-term operation, and there is no catalyst shedding or performance degradation. It has good industrial durability.

[0021] (4) Highly adjustable and widely adaptable. By adjusting the mesh count, wire diameter and alloy ratio of different layers of metal mesh, this invention can flexibly design hydrophilic gradients and pore structures for different electrolysis systems and working conditions, thereby achieving customized optimization of electrode performance. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of three specifications of metal mesh in the embodiment; Figure 2 These are topographic images of the three specifications of metal mesh after etching in the embodiments; Figure 3 This is a schematic diagram of the multilayer metal mesh synthesized by hot pressing in the embodiment; Figure 4 The underwater bubble contact angles on the surfaces of the three specifications of metal mesh in the embodiment are shown. Figure 5 This is a cross-sectional view (0 ms to 120 ms) of the process of bubbles being discharged along the surface of the three-layer metal mesh in the embodiment. Figure 6 The following are polarization curves of the electrocatalytic oxygen evolution reaction of the multilayer mesh electrode and the ordinary single-layer nickel mesh electrode obtained in the examples; Figure 7 The figures show the chronopotential curves of the multilayer mesh electrode and the ordinary single-layer nickel mesh electrode obtained in the examples. Detailed Implementation

[0023] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0024] The first aspect of this invention relates to a method for preparing a multilayer metal mesh electrode for water electrolysis with high exhaust efficiency, comprising the following steps: (1) Prepare at least two layers of metal mesh, with the aperture of each layer of metal mesh increasing sequentially from the inner layer of metal mesh closest to the diaphragm to the outer layer of metal mesh furthest from the diaphragm; (2) Surface treatment is performed on each layer of metal mesh to make the hydrophilicity of the inner layer of metal mesh higher than that of the outer layer of metal mesh, forming a gradient distribution in which the hydrophilicity decreases from the inner layer to the outer layer. (3) The metal mesh layers processed in step (2) are stacked in order from the inside to the outside, and hot-pressed and sintered in a vacuum or inert atmosphere so that the metal mesh layers are combined into a whole through intermetallic diffusion to obtain the multilayer metal mesh electrode.

[0025] Furthermore, the metal mesh has three layers, namely, an inner metal mesh A, a middle metal mesh B, and an outer metal mesh C, arranged sequentially from the side closest to the diaphragm outwards. The three metal meshes form a continuous gradient from the inside to the outside in terms of pore size and hydrophilicity.

[0026] Furthermore, the inner metal mesh A has a mesh count of 100–500 and a wire diameter of 30–80 μm; the middle metal mesh B has a mesh count of 40–100 and a wire diameter of 80–150 μm; and the outer metal mesh C has a mesh count of 10–30 and a wire diameter of 200–400 μm.

[0027] Furthermore, the inner metal mesh A is made of nickel-molybdenum alloy, with a Ni to Mo mass ratio of 9.5:0.5 to 5.0:3.0; the middle metal mesh B is made of nickel-molybdenum alloy, with a Ni to Mo mass ratio of 7.0:3.0 to 3.0:7.0; and the outer metal mesh C is made of pure nickel or nickel-molybdenum alloy, with a Ni to Mo mass ratio of not less than 9:1.

[0028] Furthermore, the surface treatment of the metal mesh is an electrochemical etching process, the etching solution is a hydrochloric acid solution, the etching intensity of the inner metal mesh is greater than that of the middle metal mesh, and the outer metal mesh is not etched or only surface cleaned.

[0029] Furthermore, the conditions for electrochemical etching of the inner metal mesh A are: hydrochloric acid concentration 0.1–1 M, current density 10–100 mA / cm². 2 The etching time was 100–1000 s; the conditions for electrochemical etching of the intermediate metal mesh B were: hydrochloric acid concentration 0.5–3 M, current density 100–500 mA / cm². 2 The etching time is 10–500 s; the outer metal mesh C is not etched, or is only cleaned by ultrasonic cleaning.

[0030] Furthermore, after electrochemical etching, a nanoscale rough structure is formed on the surface of the inner metal mesh A, a micron-scale rough structure is formed on the surface of the middle metal mesh B, and the outer metal mesh C retains a smooth surface.

[0031] Furthermore, the process parameters for hot pressing sintering in step (3) are: sintering temperature 1000~1250 ℃, compression ratio 10%~30% of the initial total thickness, and holding time 10~60 min.

[0032] The second objective of this invention is to provide a high-efficiency multilayer metal mesh electrode for water electrolysis. This electrode is integrally formed by hot-pressing and sintering at least two layers of metal mesh. From the side closest to the diaphragm outwards, the pore size of each metal mesh layer increases sequentially, and the hydrophilicity of the surface of each metal mesh layer decreases sequentially, forming a pore size gradient and a hydrophilicity gradient from the inside to the outside. The pore size gradient and the hydrophilicity gradient together constitute a channel that guides the directional transport of bubbles from the inner layer to the outer layer.

[0033] Furthermore, the electrode is composed of three layers of metal mesh, which, from the side closest to the diaphragm outwards, are an inner metal mesh A, a middle metal mesh B, and an outer metal mesh C: The inner metal mesh A has a mesh count of 100–500 mesh, a wire diameter of 30–80 μm, and is made of a nickel-molybdenum alloy with a Ni:Mo mass ratio of 9.5:0.5–5.0:3.0, with a nanoscale rough structure on its surface. The middle layer metal mesh B has a mesh count of 40-100 mesh, a wire diameter of 80-150 μm, and is made of a nickel-molybdenum alloy with a Ni:Mo mass ratio of 7.0:3.0 to 3.0:7.0, with a surface rough structure at the micron level. The outer metal mesh C has a mesh count of 10 to 30, a wire diameter of 200 to 400 μm, and is made of pure nickel or a nickel-molybdenum alloy with a Ni:Mo mass ratio of not less than 9:1. The surface is smooth. Among them, the underwater bubble contact angle of the inner metal mesh A is not less than 150°, the underwater bubble contact angle of the middle metal mesh B is between that of the inner metal mesh A and the outer metal mesh C, and the underwater bubble contact angle of the outer metal mesh C is lower than that of the inner metal mesh A.

[0034] Example This embodiment provides a method for preparing a multilayer metal mesh electrode for water electrolysis with high exhaust efficiency. The multilayer metal mesh electrode is a multilayer gradient nickel-molybdenum alloy mesh electrode, and the preparation method includes the following steps: (1) Preparation of nickel-molybdenum alloy wire and metal mesh weaving Nickel and molybdenum were weighed out in mass ratios of Ni:Mo = 5:5, Ni:Mo = 7:3, and Ni:Mo = 9:1, respectively, to prepare alloy raw materials with three different compositions. These raw materials were then melted into alloy ingots using a vacuum melting process, followed by multiple drawing processes to produce nickel-molybdenum alloy wires with diameters of 50 μm, 120 μm, and 300 μm, respectively.

[0035] Using mechanical weaving equipment, the above three specifications of alloy wires are woven into the following three types of metal mesh, with the side closer to the diaphragm designated as the inner metal mesh and the side farther from the diaphragm designated as the outer metal mesh: Inner metal mesh A: Made of Ni:Mo=5:5 alloy wire, wire diameter 50 μm, weave count 200 mesh, mesh size 77 μm; Middle layer metal mesh B: Made of Ni:Mo=7:3 alloy wire, wire diameter 120 μm, weave count 60 mesh, mesh size 300μm; Outer metal mesh C: Made of Ni:Mo = 9:1 alloy wire, with a wire diameter of 300 μm, a weave count of 20 meshes, and a mesh size of 1000 μm.

[0036] like Figure 1 As shown, the resulting three-layer metal mesh exhibits a gradient transition from dense to loose in structure from the inside out, with the wire diameter and pore size increasing layer by layer, forming multi-level gas diffusion and liquid permeation channels.

[0037] (2) Surface electrochemical etching modification Using hydrochloric acid solution as the etching electrolyte and employing a constant current mode, electrochemical etching was performed on the inner metal mesh A and the middle metal mesh B, respectively; the outer metal mesh C underwent only ultrasonic cleaning and degreasing, without any etching treatment. The specific etching parameters for each layer are as follows: Inner metal mesh A: Etching solution concentration 0.5 M HCl, current density 50 mA / cm² 2 The etching time was 400 s; after etching, a nanoscale uneven structure was formed on the surface, and the hydrophilicity and electrochemical activity were significantly improved. Intermediate metal mesh B: Etching solution concentration 0.5 M HCl, current density 200 mA / cm² 2 The etching time is 200 s; after etching, the surface has a micron-level rough structure and moderate hydrophilicity. Outer metal mesh C: No etching process is performed, the surface remains smooth, and the hydrophilicity is relatively low.

[0038] like Figure 2 As shown, after the above-mentioned graded etching process, the three-layer metal mesh forms a continuous hydrophilic gradient distribution from the inside to the outside.

[0039] (3) Vacuum hot pressing sintering assembly The inner metal mesh A, middle metal mesh B, and outer metal mesh C, after the above treatment, are stacked sequentially and placed in a vacuum hot press furnace for sintering. The sintering parameters are: sintering temperature: 1200 ℃; holding time: 30 min; unidirectional compression ratio: 10% of the total thickness; sintering atmosphere: vacuum, pressure not exceeding 10. -3 Pa. For example, Figure 3 As shown, after sintering, the three metal meshes form a metallurgical bond through metal atom diffusion, resulting in a tight interlayer bond with no delamination or obvious interfaces. The resulting multilayer gradient electrode has an overall thickness of approximately 1.8 mm and exhibits good mechanical strength and electrical conductivity.

[0040] (4) Performance characterization and testing 1) Hydrophilicity and air-repellency test The hydrophilicity of the three-layer metal mesh was characterized using an underwater bubble contact angle test. The test results are as follows: Figure 4 As shown: the contact angle of the underwater bubble in the inner metal mesh A is 155.25°, exhibiting the strongest hydrophilicity and gas-repellency; the contact angle of the middle metal mesh B is 146.75°, possessing moderate hydrophilicity and gas-repellency; and the contact angle of the outer metal mesh C is 138.65°, exhibiting relatively weak hydrophilicity. These results indicate that the hydrophilicity of the three metal meshes shows a clear gradient distribution from the inside to the outside, consistent with the expected design.

[0041] 2) Simulation of bubble transport behavior The bubble removal process within the electrode fabricated in this embodiment was numerically simulated using fluid dynamics simulation software. For example... Figure 5 As shown, simulation results indicate that after bubbles are generated on the surface of the inner metal mesh A, they are driven by the surface energy gradient between the three layers of materials to gradually migrate directionally towards the outer metal mesh C, and are carried away by the electrolyte flow field in the outer layer, forming a continuous and directional bubble transport path. This structure can effectively reduce the residence time of bubbles on the electrode surface and improve the gas-liquid separation efficiency.

[0042] 3) Performance verification of water electrolysis The multilayer gradient electrode prepared in this embodiment was used as the cathode, and alkaline water electrolysis tests were conducted in a 30 wt% KOH aqueous solution, with comparisons made to a conventional single-layer nickel mesh electrode of the same size. Figure 6-7 As shown, the test results indicate that at a current density of 300 mA / cm², 2 Under these conditions, the operating voltage of the electrode in this embodiment is about 200 mV lower than that of a conventional single-layer nickel mesh electrode; after continuous constant current operation for 3000 h, the operating voltage does not increase significantly. These results indicate that the multilayer gradient structure electrode fabricated in this embodiment can effectively reduce the ohmic voltage drop loss caused by bubble accumulation and has excellent long-term operational stability.

[0043] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing a high-efficiency multilayer metal mesh electrode for water electrolysis, characterized in that, Includes the following steps: (1) Prepare at least two layers of metal mesh, with the aperture of each layer of metal mesh increasing sequentially from the inner layer of metal mesh closest to the diaphragm to the outer layer of metal mesh furthest from the diaphragm; (2) Surface treatment is performed on each layer of metal mesh to make the hydrophilicity of the inner layer of metal mesh higher than that of the outer layer of metal mesh, forming a gradient distribution in which the hydrophilicity decreases from the inner layer to the outer layer. (3) The metal mesh layers processed in step (2) are stacked in order from the inside to the outside, and hot-pressed and sintered in a vacuum or inert atmosphere so that the metal mesh layers are combined into a whole through intermetallic diffusion to obtain the multilayer metal mesh electrode.

2. The method for preparing a high-exhaust-efficiency multilayer metal mesh electrode for water electrolysis according to claim 1, characterized in that, The metal mesh has three layers, namely, inner metal mesh A, middle metal mesh B and outer metal mesh C from the side closest to the diaphragm outwards. The three metal meshes form a continuous gradient from the inside to the outside in terms of pore size and hydrophilicity.

3. The method for preparing a high-exhaust-efficiency multilayer metal mesh electrode for water electrolysis according to claim 2, characterized in that, The inner metal mesh A has a mesh count of 100–500 and a wire diameter of 30–80 μm; The mesh count of the middle layer metal mesh B is 40–100 mesh, and the wire diameter is 80–150 μm; The outer metal mesh C has a mesh count of 10–30 and a wire diameter of 200–400 μm.

4. The method for preparing a high-exhaust-efficiency multilayer metal mesh electrode for water electrolysis according to claim 2, characterized in that, The inner metal mesh A is made of nickel-molybdenum alloy, with a Ni to Mo mass ratio of 9.5:0.5 to 5.0:3.

0. The material of the middle layer metal mesh B is a nickel-molybdenum alloy, with a Ni to Mo mass ratio of 7.0:3.0 to 3.0:7.

0. The outer metal mesh C is made of pure nickel or a nickel-molybdenum alloy, with a Ni to Mo mass ratio of not less than 9:

1.

5. The method for preparing a high-exhaust-efficiency multilayer metal mesh electrode for water electrolysis according to claim 2, characterized in that, The surface treatment of the metal mesh is electrochemical etching, and the etching solution is hydrochloric acid solution. The etching intensity of the inner metal mesh is greater than that of the middle metal mesh, and the outer metal mesh is not etched or only surface cleaned.

6. The method for preparing a high-exhaust-efficiency multilayer metal mesh electrode for water electrolysis according to claim 5, characterized in that, The conditions for electrochemical etching of the inner metal mesh A are: hydrochloric acid concentration 0.1–1 M, current density 10–100 mA / cm². 2 Etching time: 100–1000 s; The conditions for electrochemical etching of the intermediate metal mesh B are: hydrochloric acid concentration 0.5–3 M, current density 100–500 mA / cm². 2 Etching time: 10–500 s; The outer metal mesh C is not etched, or is only cleaned by ultrasonic cleaning.

7. The method for preparing a high-exhaust-efficiency multilayer metal mesh electrode for water electrolysis according to claim 5, characterized in that, After electrochemical etching, a nanoscale rough structure is formed on the surface of the inner metal mesh A, a micrometer-scale rough structure is formed on the surface of the middle metal mesh B, and the outer metal mesh C retains a smooth surface.

8. The method for preparing a high-exhaust-efficiency multilayer metal mesh electrode for water electrolysis according to claim 1, characterized in that, The process parameters for hot pressing sintering in step (3) are: sintering temperature 1000~1250 ℃, compression ratio 10%~30% of the initial total thickness, and holding time 10~60 min.

9. A multilayer metal mesh electrode for water electrolysis with high exhaust efficiency, characterized in that, The electrode is integrally formed by hot pressing and sintering at least two layers of metal mesh. From the side closest to the diaphragm outwards, the pore size of each metal mesh layer increases sequentially, and the hydrophilicity of the surface of each metal mesh layer decreases sequentially, forming a pore size gradient and a hydrophilicity gradient from the inside to the outside. The pore size gradient and the hydrophilicity gradient together constitute a channel that guides the directional transport of bubbles from the inner layer to the outer layer.

10. The multilayer metal mesh electrode according to claim 9, characterized in that, The electrode consists of three layers of metal mesh, which, from the side closest to the diaphragm outwards, are the inner metal mesh A, the middle metal mesh B, and the outer metal mesh C: The inner metal mesh A has a mesh count of 100–500 mesh, a wire diameter of 30–80 μm, and is made of a nickel-molybdenum alloy with a Ni:Mo mass ratio of 9.5:0.5–5.0:3.0, with a nanoscale rough structure on its surface. The middle layer metal mesh B has a mesh count of 40-100 mesh, a wire diameter of 80-150 μm, and is made of a nickel-molybdenum alloy with a Ni:Mo mass ratio of 7.0:3.0 to 3.0:7.0, with a surface rough structure at the micron level. The outer metal mesh C has a mesh count of 10 to 30, a wire diameter of 200 to 400 μm, and is made of pure nickel or a nickel-molybdenum alloy with a Ni:Mo mass ratio of not less than 9:

1. The surface is smooth. Among them, the underwater bubble contact angle of the inner metal mesh A is not less than 150°, the underwater bubble contact angle of the middle metal mesh B is between that of the inner metal mesh A and the outer metal mesh C, and the underwater bubble contact angle of the outer metal mesh C is lower than that of the inner metal mesh A.

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