A method for preparing a three-dimensional composite catalytic electrode for alkaline water electrolysis to produce hydrogen.

Abstract

This invention relates to the field of electrode materials for hydrogen production by water electrolysis, and particularly to a method for preparing a three-dimensional composite catalytic electrode for alkaline water electrolysis. The invention first involves degreasing, sandblasting, micro-nano etching, and electrochemical activation of a nickel-based conductive substrate. Then, using this activated substrate as the working electrode, a three-dimensional porous precursor layer is constructed by three-pulse current electrodeposition in an electrolyte containing multi-metal salts, a composite structure directing agent, and carbon nanotubes. Next, the deposited electrode undergoes programmed temperature heat treatment in a mixed gas flow of protective and oxygen-containing atmospheres. Finally, surface modification is performed through argon-oxygen plasma treatment to introduce oxygen vacancies to optimize active sites, ultimately obtaining a highly active and stable three-dimensional composite catalytic electrode.

Description

Technical Field

[0001] This invention relates to the field of electrode materials technology for hydrogen production by water electrolysis, and specifically to a method for preparing a three-dimensional composite catalytic electrode for hydrogen production by alkaline water electrolysis. Background Technology

[0002] In alkaline water electrolysis for hydrogen production, the oxygen evolution reaction (OER) at the anode is a complex kinetic process involving four electron transfers. Its high energy barrier and slow kinetics make it a core bottleneck restricting the overall energy conversion efficiency of the electrolyzer. Currently, while commercially available noble metal-based OER catalysts (such as RuO2 and IrO2) exhibit excellent catalytic activity, the scarcity and extreme expense of these precious metals significantly increase hydrogen production costs, making it difficult to meet the demands of large-scale industrial green hydrogen production. Therefore, developing low-cost, high-activity non-noble metal-based OER catalysts has become a current research hotspot. Among them, nickel-iron-cobalt (NiFeCo)-based transition metal materials are considered the most promising alternatives to non-noble metal catalysts due to their abundant crustal reserves, low cost, tunable electronic structure, and excellent intrinsic catalytic activity. However, the preparation and practical application of existing NiFeCo-based electrodes still face many unresolved technical limitations.

[0003] Firstly, the adhesion between the catalyst coating and the substrate is insufficient. In traditional electrode fabrication processes, catalysts are often prepared in powder form and then coated onto the substrate surface using polymer binders, or deposited directly onto a smooth substrate surface without sufficient pretreatment. The bonding between the coating and the substrate is often weak, resulting in poor adhesion at industrial-grade high current densities (>500 mA / cm²). 2 Under such conditions, intense gas erosion can easily cause the coating to peel off, leading to a rapid decline in electrode performance and severely shortening the electrode's service life.

[0004] Secondly, the catalyst's structure and mass transfer performance are insufficient. Catalyst layers prepared by traditional constant current / constant voltage electrodeposition methods often have a dense structure and limited specific surface area, resulting in insufficient exposure of active sites. At the same time, the dense structure increases the mass transfer resistance of the electrolyte. Under high current density, the diffusion of reactants and the desorption of product bubbles are restricted, further increasing the reaction overpotential and limiting the performance improvement under high current.

[0005] Third, the regulation of active sites is insufficient. Existing preparation methods struggle to effectively regulate the surface electronic structure of catalysts, resulting in insufficient intrinsic activity of active sites and low electron conduction efficiency. This leads to high overpotentials at high current densities and high energy consumption in hydrogen production. Furthermore, most existing NiFeCo-based catalysts remain stable only at low to medium current densities in the laboratory. During long-term operation at high currents in industrial settings, they are prone to dissolution, reconstruction, and structural collapse of the active phase, failing to meet the service life requirements of thousands of hours for industrial electrolyzers. Summary of the Invention

[0006] To address the shortcomings of existing NiFeCo-based water electrolysis oxygen evolution electrodes, such as weak coating adhesion, insufficient activity, poor stability under high current, and difficulty in scaling up the preparation process, the present invention aims to provide a method for preparing a three-dimensional composite catalytic electrode for alkaline water electrolysis to produce hydrogen, thereby solving various problems in the prior art and achieving low-cost, large-scale preparation of highly active and highly stable industrial-grade water electrolysis electrodes.

[0007] To achieve the above objectives, the present invention employs the following technical solution:

[0008] A method for preparing a three-dimensional composite catalytic electrode for alkaline water electrolysis to produce hydrogen includes the following steps:

[0009] S1. Substrate pretreatment: The nickel-based conductive substrate is sequentially subjected to degreasing cleaning, sandblasting roughening, micro-nano etching and electrochemical activation to obtain an activated substrate; the micro-nano etching is performed in a buffered fluorine-containing ion etching solution of 0.2-0.5 mol / L for 10-60 minutes to form a micron-scale pit structure with a diameter of 5-20 micrometers on the substrate surface.

[0010] S2. Pulse Electrodeposition Precursor Layer: Using the activated substrate as the working electrode, the substrate is placed in an electrolyte containing a multi-metal salt, a composite structure directing agent, and a carbon nanotube dispersion. Electrodeposition is performed using a three-pulse current to form a three-dimensional porous precursor layer on the substrate surface. The multi-metal salt includes nickel salt, iron salt, and cobalt salt, with a molar ratio of nickel, iron, and cobalt of (3-5):1:(0.2-0.5). The composite structure directing agent is a mixture of ammonium citrate and tartaric acid in a mass ratio of 2:1. The concentration of the carbon nanotube dispersion is 0.5-1.5 mg / mL, and the diameter of the carbon nanotubes is 10-20 nm.

[0011] S3. In-situ controlled oxidation heat treatment: The substrate with the precursor layer deposited is subjected to programmed temperature rise heat treatment in a mixed atmosphere of protective atmosphere and oxygen-containing atmosphere to obtain the heat-treated electrode; wherein the final heat treatment temperature is 300-450℃, and the volume fraction of oxygen in the oxygen-containing atmosphere section is 1%-10%;

[0012] S4. Plasma surface modification: The heat-treated electrode is placed in an argon-oxygen plasma for 5-15 minutes with a plasma power of 100-200W to further introduce oxygen vacancies and optimize the catalytic active sites, thus obtaining the three-dimensional composite catalytic electrode.

[0013] Furthermore, the sandblasting roughening meets the following conditions: the sandblasting pressure is 0.2-0.4 MPa, the sandblasting abrasive is selected from at least one of white fused alumina and brown fused alumina, and the average particle size of the abrasive is 60-100 mesh; the surface roughness of the nickel-based conductive substrate after sandblasting is 2-5 μm.

[0014] Further, in step S1, the electrochemical activation is carried out in a sulfuric acid solution with a concentration of 0.5-1.5 mol / L, at an A / cm² intensity of 10-50 mA. 2 The anodic current density is processed for 30-180 seconds.

[0015] Further, in step S2, the electrolyte contains nickel ions at a concentration of 0.05-0.2 mol / L, iron ions at a concentration of 0.01-0.05 mol / L, and cobalt ions at a concentration of 0.002-0.025 mol / L.

[0016] Further, in step S2, the parameters of the three-pulse current are: peak current density J_high is -20 to -50 mA / cm². 2 The pulse duration t_on is 0.05-0.2 seconds; the peak current density J_mid is -10 to -20 mA / cm². 2 The pulse time t_mid is 0.1-0.3 seconds; the low peak current density J_low is -2 to -10 mA / cm². 2 The pulse time t_off is 0.1-0.5 seconds.

[0017] Furthermore, in step S2, the total charge amount of electrodeposition is 5-20 C / cm².

[0018] Further, in step S3, the programmed heating heat treatment specifically involves: first, heating to 250°C at 2-5°C / min under an argon atmosphere and holding for 30 minutes to remove organic matter; then switching to a mixture of argon and oxygen and continuing to heat to the target temperature (300-450°C) at the same rate, holding for 60-120 minutes, and then cooling with the furnace.

[0019] Furthermore, in step S4, the volume ratio of argon to oxygen in the argon-oxygen plasma is 9:1.

[0020] This invention also provides a three-dimensional composite catalytic electrode prepared by the above method, wherein the electrode surface has an inter-crosslinked three-dimensional nanosheet network structure, the nanosheet thickness is 5-15 nm, and the specific surface area of ​​the electrode is 80-120 m². 2 / g, in a 1.0 mol / L KOH solution, reaches 100 mA / cm. 2 The required oxygen evolution overpotential for the current density is 220-240 mV; and the electrode operates at 500 mA / cm².2 After 300 hours of continuous operation at high current density, the potential decay is less than 2%.

[0021] The beneficial effects of this invention are:

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. This invention designs a composite substrate pretreatment process. Through a multi-step process of "degreasing, sandblasting roughening, micro-nano etching, and electrochemical activation", a multi-level rough structure of micro-nano composite is constructed on the surface of the nickel substrate. This not only significantly increases the specific surface area of ​​the substrate, but also significantly enhances the mechanical bonding and chemical bonding between the subsequent deposited coating and the substrate. This fundamentally solves the problem of coating detachment under high current conditions and greatly improves the long-term operational stability of the electrode.

[0024] 2. This invention innovatively employs a three-pulse electrodeposition process, combined with a composite structure directing agent of ammonium citrate and tartaric acid, and the doping of carbon nanotubes, to grow an in-situ cross-linked three-dimensional nanosheet network structure on the substrate surface. This three-dimensional porous structure not only significantly increases the overall specific surface area of ​​the electrode and fully exposes the internal catalytic active sites, but also constructs continuous electrolyte mass transfer channels and electron transport channels, effectively reducing mass transfer resistance and ohmic loss under high current, and ensuring reaction kinetics under high current.

[0025] 3. This invention employs an in-situ controllable oxidation heat treatment process. By precisely controlling the oxygen content in the mixed atmosphere and the programmed temperature rise process, the controlled oxidation of the precursor is achieved. This ensures that the metal precursor is fully converted into a highly active oxide / hydroxide phase, while avoiding the decrease in conductivity caused by excessive oxidation in a pure air atmosphere. At the same time, it enhances the electronic synergistic effect among the three metals Ni, Fe, and Co, further improving the intrinsic catalytic activity.

[0026] 4. Finally, this invention employs argon-oxygen plasma surface modification. By utilizing the bombardment effect of high-energy plasma, abundant oxygen vacancy defects are introduced into the catalyst surface, effectively regulating the electronic structure of active sites, enhancing the catalyst's adsorption capacity for OER reaction intermediates, further reducing the reaction energy barrier, and significantly improving the catalytic activity of the electrode.

[0027] 5. The three-dimensional composite catalytic electrode prepared by this invention possesses both extremely high catalytic activity and excellent long-term stability. In 1.0M KOH solution, it requires only 220-240mV of oxygen evolution overpotential to reach a current density of 100mA / cm², which is far superior to traditional nickel-iron-based electrodes. Simultaneously, at an industrial-grade high current density of 500mA / cm², the potential decay is less than 2% after 300 hours of continuous operation, meeting the long-term operational requirements for industrial water electrolysis to produce hydrogen. Furthermore, the preparation process of this invention is simple, with all steps involving conventional wet and thermal treatment processes, resulting in low cost and ease of large-scale mass production, thus possessing extremely high industrial application value. Attached Figure Description

[0028] Figure 1 This is a schematic flowchart of the preparation method of the three-dimensional composite catalytic electrode of the present invention.

[0029] Figure 2 This is a picture of the nickel-based conductive substrate before processing.

[0030] Figure 3 This is a picture of the finished product after treatment with a three-dimensional composite catalytic electrode used for alkaline water electrolysis to produce hydrogen.

[0031] Figure 4 This is a low-magnification scanning electron microscope (SEM) image of the catalytic layer on the surface of the three-dimensional composite catalytic electrode prepared in Example 1.

[0032] Figure 5 This is a high-magnification SEM image of the catalytic layer on the surface of the three-dimensional composite catalytic electrode prepared in Example 1. Detailed Implementation

[0033] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0034] Example 1

[0035] The preparation method of the three-dimensional composite catalytic electrode for alkaline water electrolysis to produce hydrogen in this embodiment includes the following steps:

[0036] S1. Substrate Pretreatment: A 1.5mm thick nickel foam was selected as the nickel-based conductive substrate. First, the substrate was ultrasonically cleaned in acetone solution for 10 minutes to remove surface oil, followed by rinsing with deionized water. Next, sandblasting roughening was performed using white corundum as the abrasive, with an average particle size of 80 mesh and a sandblasting pressure controlled at 0.3 MPa. The surface roughness of the substrate after this treatment was 3.5 μm. Then, micro-nano etching was performed, placing the substrate in a 0.3 mol / L buffered fluorine-containing ion etching solution at room temperature for 30 minutes, forming micron-sized pit structures with an average diameter of 12 μm on the substrate surface. Finally, electrochemical activation was performed, using the etched substrate as the working electrode, placed in a 1.0 mol / L sulfuric acid solution at 30 mA / cm². 2 The anodic current density was applied for 90 seconds to obtain an activated matrix.

[0037] S2. Pulse Electrodeposition Precursor Layer: The electrodeposition electrolyte was prepared, containing: 0.1 mol / L nickel sulfate (Ni source), 0.025 mol / L ferrous sulfate (Fe source), and 0.01 mol / L cobalt sulfate (Co source), i.e., a molar ratio of nickel, iron, and cobalt of 4:1:0.4; a composite structure directing agent: 10 g / L ammonium citrate and 5 g / L tartaric acid, with a mass ratio of 2:1; and a carbon nanotube dispersion with a concentration of 1.0 mg / mL, using carbon nanotubes with a diameter of 15 nm. Using the activated substrate obtained in step S1 as the working electrode, a platinum sheet as the counter electrode, and an Ag / AgCl saturated potassium chloride electrode as the reference electrode, electrodeposition was performed using a three-pulse current: the peak current density J_high was -30 mA / cm². 2 The pulse duration t_on is 0.1 seconds; the peak current density J_mid is -15 mA / cm². 2 The pulse time t_mid is 0.2 seconds; the low peak current density J_low is -5 mA / cm. 2 The pulse time t_off is 0.3 seconds; the total charge amount of electrodeposition is controlled to be 10 C / cm. 2 After electrodeposition, a precursor layer with a three-dimensional porous structure is formed on the substrate surface.

[0038] S3. In-situ controlled oxidation heat treatment: The substrate with the precursor layer deposited is placed in a tubular heat treatment furnace. First, pure argon is introduced as a protective atmosphere, and the temperature is increased to 250°C at a heating rate of 3°C / min and held for 30 minutes to remove organic impurities in the precursor layer. Then, the atmosphere is switched to a mixed atmosphere of argon and oxygen, with the oxygen volume fraction being 5%, and the temperature is increased to 400°C at a heating rate of 3°C / min and held for 90 minutes. After the holding is completed, the substrate is cooled to room temperature with the furnace to obtain the heat-treated electrode.

[0039] S4. Plasma surface modification: The heat-treated electrode is placed in a plasma treatment device, and a mixture of argon and oxygen with a volume ratio of 9:1 is introduced. The plasma power is controlled at 150W and the treatment time is 10 minutes. Oxygen vacancies are introduced on the electrode surface by plasma bombardment to optimize the catalytic active sites and finally obtain the three-dimensional composite catalytic electrode.

[0040] The microstructure of the three-dimensional composite catalytic electrode prepared in this embodiment was characterized using scanning electron microscopy, and the results are as follows: Figure 4-5 As shown, the catalyst layer on the electrode surface exhibits a three-dimensional flower-like hierarchical porous structure formed by cross-linking of two-dimensional nanosheets. The nanosheets are 5-15 nm thick, and the flower-like clusters are 3-5 μm in diameter. The clusters overlap to form a continuous conductive network and mass transfer channels. BET testing revealed that the specific surface area of ​​the electrode is 10² m². 2 / g.

[0041] The electrode prepared in this embodiment was subjected to performance testing: electrochemical tests were performed in a standard three-electrode system in a 1.0 mol / L KOH solution. The results showed that the electrode achieved 100 mA / cm². 2 The oxygen evolution overpotential at the current density is 230 mV; the specific surface area of ​​the electrode, obtained by BET testing, is 102 m². 2 / g; at 500 mA / cm 2 Under high current density, constant current stability was tested. After running continuously for 300 hours, the electrode potential only decreased by 1.5%, demonstrating excellent long-term stability.

[0042] Example 2

[0043] The preparation method of the three-dimensional composite catalytic electrode for alkaline water electrolysis to produce hydrogen in this embodiment differs from that in Example 1 in that all process parameters are taken as the lower limit of the range defined by this invention, and specifically includes the following steps:

[0044] S1. Substrate Pretreatment: A 1.5 mm thick nickel foam was selected as the nickel-based conductive substrate. First, the substrate was ultrasonically cleaned in acetone solution for 10 minutes to remove surface oil, and then rinsed with deionized water. Next, sandblasting roughening was performed using white corundum as the abrasive with an average particle size of 60 mesh and a sandblasting pressure of 0.2 MPa. After treatment, the surface roughness of the substrate was 2 μm. Then, micro-nano etching was performed. The substrate was placed in a 0.2 mol / L buffered fluorine-containing ion etching solution and treated at room temperature for 10 minutes to form a micron-scale pit structure with an average diameter of 5 μm on the substrate surface. Finally, electrochemical activation was performed. The etched substrate was used as the working electrode and placed in a 0.5 mol / L sulfuric acid solution. It was treated with an anodic current density of 10 mA / cm² for 30 seconds to obtain an activated substrate.

[0045] S2. Pulse electrodeposition precursor layer: Prepare the electrodeposition electrolyte, which includes: nickel sulfate (Ni source) 0.05 mol / L, ferrous sulfate (Fe source) 0.01 mol / L, and cobalt sulfate (Co source) 0.002 mol / L, i.e., the molar ratio of nickel, iron, and cobalt is 3:1:0.2; composite structure directing agent: ammonium citrate 10 g / L and tartaric acid 5 g / L, with a mass ratio of 2:1; carbon nanotube dispersion with a concentration of 0.5 mg / mL, and the diameter of the carbon nanotubes used is 10 nm. Using the activated substrate obtained in step S1 as the working electrode, a platinum sheet as the counter electrode, and an Ag / AgCl saturated potassium chloride electrode as the reference electrode, electrodeposition was performed using a three-pulse current: high peak current density J_high was -20 mA / cm², pulse time t_on was 0.05 seconds; medium peak current density J_mid was -10 mA / cm², pulse time t_mid was 0.1 seconds; and low peak current density J_low was -2 mA / cm², pulse time t_off was 0.1 seconds. The total charge of electrodeposition was controlled to be 5 C / cm². After electrodeposition, a three-dimensional porous precursor layer was formed on the substrate surface.

[0046] S3. In-situ controlled oxidation heat treatment: The substrate with the precursor layer deposited is placed in a tubular heat treatment furnace. First, pure argon is introduced as a protective atmosphere, and the temperature is increased to 250°C at a heating rate of 2°C / min and held for 30 minutes to remove organic impurities in the precursor layer. Then, the atmosphere is switched to a mixed atmosphere of argon and oxygen, with the oxygen volume fraction being 1%, and the temperature is increased to 300°C at a rate of 2°C / min and held for 60 minutes. After the holding is completed, the furnace is cooled to room temperature to obtain the heat-treated electrode.

[0047] S4. Plasma surface modification: The heat-treated electrode is placed in a plasma treatment device, and a mixture of argon and oxygen with a volume ratio of 9:1 is introduced. The plasma power is controlled at 100W and the treatment time is 5 minutes. Oxygen vacancies are introduced by plasma bombarding the electrode surface to optimize the catalytic active sites, and finally the three-dimensional composite catalytic electrode is obtained.

[0048] The microstructure of the three-dimensional composite catalytic electrode prepared in this embodiment was characterized by scanning electron microscopy. The results showed that the catalytic layer on the electrode surface exhibited a three-dimensional flower-like hierarchical porous structure formed by cross-linking of two-dimensional nanosheets. The thickness of the nanosheets was 5-12 nm, and the diameter of the flower-like clusters was 2-4 μm. The clusters overlapped with each other to form a continuous conductive network and mass transfer channels. The specific surface area of ​​the electrode was 81 m² / g as determined by BET testing.

[0049] The electrode prepared in this embodiment was subjected to performance testing: electrochemical testing was performed in a standard three-electrode system in a 1.0 mol / L KOH solution. The results showed that the oxygen evolution overpotential of the electrode at a current density of 100 mA / cm² was 238 mV. Constant current stability testing was performed at a high current density of 500 mA / cm². After continuous operation for 300 hours, the electrode potential only decreased by 1.8%, which meets the requirements for industrial use.

[0050] Example 3

[0051] The preparation method of the three-dimensional composite catalytic electrode for alkaline water electrolysis to produce hydrogen in this embodiment differs from that in Example 1 in that all process parameters are taken at the upper limit of the range defined by this invention, and specifically includes the following steps:

[0052] S1. Substrate Pretreatment: A 1.5mm thick nickel foam was selected as the nickel-based conductive substrate. First, the substrate was ultrasonically cleaned in acetone solution for 10 minutes to remove surface oil, followed by rinsing with deionized water. Next, sandblasting roughening was performed using white corundum as the abrasive with an average particle size of 100 mesh and a sandblasting pressure controlled at 0.4 MPa. The surface roughness of the substrate after treatment was 5 μm. Then, micro-nano etching was performed, placing the substrate in a 0.5 mol / L buffered fluorine-containing ion etching solution at room temperature for 60 minutes, forming micron-sized pit structures with an average diameter of 20 μm on the substrate surface. Finally, electrochemical activation was performed, using the etched substrate as the working electrode, placed in a 1.5 mol / L sulfuric acid solution at 50 mA / cm². 2 The anodic current density was applied for 180 seconds to obtain an activated matrix.

[0053] S2. Pulse electrodeposition precursor layer: Prepare the electrodeposition electrolyte, which includes: nickel sulfate (Ni source) 0.2 mol / L, ferrous sulfate (Fe source) 0.05 mol / L, and cobalt sulfate (Co source) 0.025 mol / L, i.e., the molar ratio of nickel, iron, and cobalt is 5:1:0.5; composite structure directing agent: ammonium citrate 10 g / L and tartaric acid 5 g / L, with a mass ratio of 2:1; carbon nanotube dispersion with a concentration of 1.5 mg / mL, and the diameter of the carbon nanotubes used is 20 nm. Using the activated substrate obtained in step S1 as the working electrode, a platinum sheet as the counter electrode, and an Ag / AgCl saturated potassium chloride electrode as the reference electrode, electrodeposition was performed using a three-pulse current: high peak current density J_high was -50 mA / cm², pulse time t_on was 0.2 seconds; medium peak current density J_mid was -20 mA / cm², pulse time t_mid was 0.3 seconds; and low peak current density J_low was -10 mA / cm², pulse time t_off was 0.5 seconds. The total charge of electrodeposition was controlled to be 20 C / cm². After electrodeposition, a three-dimensional porous precursor layer was formed on the substrate surface.

[0054] S3. In-situ controlled oxidation heat treatment: The substrate with the precursor layer deposited is placed in a tubular heat treatment furnace. First, pure argon is introduced as a protective atmosphere, and the temperature is increased to 250°C at a heating rate of 5°C / min and held for 30 minutes to remove organic impurities in the precursor layer. Then, the atmosphere is switched to a mixed atmosphere of argon and oxygen, with an oxygen volume fraction of 10%, and the temperature is increased to 450°C at a heating rate of 5°C / min and held for 120 minutes. After the holding is completed, the furnace is cooled to room temperature to obtain the heat-treated electrode.

[0055] S4. Plasma surface modification: The heat-treated electrode is placed in a plasma treatment device, and a mixture of argon and oxygen with a volume ratio of 9:1 is introduced. The plasma power is controlled at 200W and the treatment time is 15 minutes. Oxygen vacancies are introduced on the electrode surface by plasma bombardment to optimize the catalytic active sites and finally obtain the three-dimensional composite catalytic electrode.

[0056] The microstructure of the three-dimensional composite catalytic electrode prepared in this embodiment was characterized by scanning electron microscopy. The results showed that the catalytic layer on the electrode surface exhibited a dense three-dimensional flower-like hierarchical porous structure formed by cross-linking of two-dimensional nanosheets. The thickness of the nanosheets was 8-15 nm, and the diameter of the flower-like clusters was 4-6 μm. The clusters overlapped with each other to form a denser continuous conductive network and mass transfer channels. The specific surface area of ​​the electrode was 118 m² / g as determined by BET testing.

[0057] The performance of the electrode prepared in this embodiment was tested: electrochemical tests were performed in a standard three-electrode system in a 1.0 mol / L KOH solution. The results showed that the oxygen evolution overpotential of the electrode at a current density of 100 mA / cm² was 222 mV. The constant current stability test was performed at a high current density of 500 mA / cm². After running continuously for 300 hours, the electrode potential only decreased by 1.2%, indicating excellent catalytic activity and stability.

[0058] Comparative Example 1

[0059] Nickel-iron-cobalt electrodes were prepared using a traditional constant current electrodeposition method as a comparative example. The specific steps were as follows: the substrate underwent only acetone degreasing treatment, without sandblasting, etching, or activation steps; electrodeposition was performed using a conventional constant current with a current density of -15 mA / cm². 2 The remaining electrolyte components are the same as in Example 1; the heat treatment is performed at 400°C in an air atmosphere, without plasma modification.

[0060] Performance test results: The electrode achieved 100 mA / cm 2 The oxygen evolution overpotential at the current density is 285mV, which is much higher than the overpotential in the embodiment of the present invention; at 500mA / cm 2 Stability tests were conducted, and after only 100 hours of operation, the potential decay reached 6.2%, which is far worse than the long-term stability of the embodiments of the present invention, fully demonstrating the significant advantages of the composite pretreatment, three-pulse electrodeposition and plasma modification process of the present invention.

[0061] Comparative Example 2

[0062] The difference between this comparative example and Example 1 is that the substrate pretreatment only involves degreasing and sandblasting roughening, without micro-nano etching and electrochemical activation steps. The remaining steps and parameters are the same as in Example 1.

[0063] Performance test results: The electrode achieved 100 mA / cm 2 The oxygen evolution overpotential at the current density is 268 mV; the specific surface area is 65 m². 2 / g; 500mA / cm 2 After 300 hours of operation, the potential decayed by 4.8%. This result indicates that without micro-nano etching and electrochemical activation, a multi-level rough structure cannot be formed on the substrate surface, resulting in insufficient adhesion between the coating and the substrate and inadequate exposure of active sites. This leads to a significant decrease in catalytic activity and stability, demonstrating the necessity of the composite pretreatment process of this invention.

[0064] Comparative Example 3

[0065] The difference between this comparative example and Example 1 is that the electrodeposition was performed using conventional constant current electrodeposition (current density -15 mA / cm²). 2The three-pulse electrodeposition process was not used, and no composite structure directing agent or carbon nanotubes were added to the electrolyte. All other steps and parameters were the same as in Example 1.

[0066] Performance test results: The electrode achieved 100 mA / cm 2 The oxygen evolution overpotential at the current density is 272 mV; the specific surface area is 58 m². 2 / g; 500mA / cm 2 After 300 hours of operation, the potential decayed by 5.1%. This result indicates that traditional constant current electrodeposition cannot form three-dimensional porous structures and lacks the synergistic effect of structure guiding agents and carbon nanotubes, resulting in insufficient exposure of active sites and low mass transfer efficiency. This further demonstrates the advantages of the three-pulse electrodeposition process and composite additives of this invention.

[0067] Comparative Example 4

[0068] The difference between this comparative example and Example 1 is that the heat treatment uses a pure air atmosphere (100% oxygen volume fraction) and does not use in-situ controlled oxidation heat treatment (mixed atmosphere). The remaining steps and parameters are the same as in Example 1.

[0069] Performance test results: The electrode achieved 100 mA / cm 2 The oxygen evolution overpotential at the current density is 262 mV; the specific surface area is 72 m². 2 / g; 500mA / cm 2 After 300 hours of operation, the potential decayed by 4.3%. This result indicates that heat treatment in a pure air atmosphere leads to excessive oxidation of the active phase, reducing electrode conductivity and destroying the integrity of the three-dimensional structure, thus proving the rationality of the in-situ controllable oxidation heat treatment process of this invention.

[0070] Comparative Example 5

[0071] The difference between this comparative example and Example 1 is that the argon-oxygen plasma surface modification step is not performed; all other steps and parameters are the same as in Example 1.

[0072] Performance test results: The electrode achieved 100 mA / cm 2 The oxygen evolution overpotential at the current density is 255 mV; the specific surface area is 98 m². 2 / g; 500mA / cm 2 After 300 hours of operation, the potential decayed by 3.2%. This result indicates that without plasma modification, sufficient oxygen vacancies cannot be introduced, the electronic structure of active sites cannot be optimized, and the catalytic activity and stability cannot reach their optimal levels, demonstrating the importance of the plasma surface modification step in this invention.

[0073] The above description is merely an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A method for preparing a three-dimensional composite catalytic electrode for alkaline water electrolysis to produce hydrogen, characterized in that, Includes the following steps: S1. Substrate pretreatment: The nickel-based conductive substrate is sequentially subjected to degreasing cleaning, sandblasting roughening, micro-nano etching and electrochemical activation to obtain an activated substrate; S2. Pulse electrodeposition precursor layer: Using the activated substrate as the working electrode, the substrate is placed in an electrolyte containing multi-metal salts, composite structure guiding agents and carbon nanotube dispersions, and electrodeposition is performed using a three-pulse current to form a three-dimensional porous precursor layer on the substrate surface. S3. In-situ controlled oxidation heat treatment: The substrate with the precursor layer deposited is subjected to programmed temperature rise heat treatment in a mixed atmosphere of protective atmosphere and oxygen-containing atmosphere to obtain the heat-treated electrode; wherein the final heat treatment temperature is 300-450℃, and the volume fraction of oxygen in the oxygen-containing atmosphere section is 1%-10%; S4. Plasma surface modification: The heat-treated electrode is placed in an argon-oxygen plasma for 5-15 minutes with a plasma power of 100-200W to further introduce oxygen vacancies and optimize the catalytic active sites, thus obtaining the three-dimensional composite catalytic electrode.

2. The preparation method according to claim 1, characterized in that, In step S1, the conditions to be met for the sandblasting roughening are as follows: the sandblasting pressure is 0.2-0.4 MPa, the sandblasting abrasive is selected from at least one of white corundum and brown corundum, and the average particle size of the abrasive is 60-100 mesh; the surface roughness of the nickel-based conductive substrate after sandblasting is 2-5 μm; the micro-nano etching is performed by treating the substrate in a buffered fluorine-containing ion etching solution of 0.2-0.5 mol / L for 10-60 minutes to form a micron-scale pit structure with a diameter of 5-20 micrometers on the substrate surface.

3. The preparation method according to claim 2, characterized in that, The electrochemical activation is performed in a sulfuric acid solution with a concentration of 0.5-1.5 mol / L, at an A / cm² intensity of 10-50 mA. 2 The anodic current density is processed for 30-180 seconds.

4. The preparation method according to claim 1, characterized in that, In step S2, the multi-metal salt includes nickel salt, iron salt and cobalt salt, and the molar ratio of nickel, iron and cobalt is (3-5):1:(0.2-0.5); the composite structure directing agent is a compound of ammonium citrate and tartaric acid, with a mass ratio of 2:1; the concentration of the carbon nanotube dispersion is 0.5-1.5 mg / mL, and the diameter of the carbon nanotubes is 10-20 nm.

5. The preparation method according to claim 4, characterized in that, In step S2, the electrolyte contains nickel ions at a concentration of 0.05-0.2 mol / L, iron ions at a concentration of 0.01-0.05 mol / L, and cobalt ions at a concentration of 0.002-0.025 mol / L.

6. The preparation method according to claim 5, characterized in that, In step S2, the parameters of the three-pulse current are: peak current density J_high is -20 to -50 mA / cm². 2 The pulse duration t_on is 0.05-0.2 seconds; the peak current density J_mid is -10 to -20 mA / cm². 2 The pulse time t_mid is 0.1-0.3 seconds; the low peak current density J_low is -2 to -10 mA / cm². 2 The pulse time t_off is 0.1-0.5 seconds.

7. The preparation method according to claim 6, characterized in that, In step S2, the total charge of the electrodeposition is 5-20 C / cm. 2 .

8. The preparation method according to claim 1, characterized in that, In step S3, the programmed temperature rise heat treatment specifically involves: first, heating to 250°C at 2-5°C / min under an argon atmosphere and holding for 30 minutes to remove organic matter; then switching to a mixture of argon and oxygen and continuing to heat to the target temperature at the same rate, holding for 60-120 minutes, and then cooling with the furnace; the target temperature is 300-450°C.

9. The preparation method according to claim 1, characterized in that, In step S4, the volume ratio of argon to oxygen in the argon-oxygen plasma is 9:

1.

10. A three-dimensional composite catalytic electrode, prepared by the method according to any one of claims 1-9, characterized in that, The electrode surface has an inter-crosslinked three-dimensional nanosheet network structure, with nanosheet thickness of 5-15 nm and a specific surface area of ​​80-120 m². 2 / g.

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