Preparation method and system of seawater hydrogen production catalyst

Abstract

The invention discloses a seawater hydrogen production catalyst preparation method and system, and belongs to the technical field of seawater hydrogen production. The method comprises the steps of substrate pretreatment, gradient alloy core layer preparation, ternary permeation barrier layer preparation, phase change texturing treatment and electric field assisted surface modification. A nickel-iron-cobalt ternary alloy layer with ordered atomic arrangement is prepared through a gradient magnetic field and ultrasonic synergistic auxiliary electrochemical deposition technology, a ternary permeation barrier layer is prepared according to the sequence of a tungsten layer, a molybdenum layer and a chromium layer by adopting an atomic layer deposition technology, and chloride ion erosion is effectively prevented. The system comprises a substrate pretreatment device, a gradient alloy core layer preparation device, a ternary permeation barrier layer preparation device, a phase change texturing treatment device and an electric field auxiliary surface modification device. The prepared catalyst has the advantages of high catalytic activity, fast reaction kinetics, large active area, low charge transfer resistance and strong anti-corrosion stability, and shows excellent long-term stability in a seawater electrolysis environment.

Description

Technical Field

[0001] This invention relates to the field of seawater hydrogen production technology, specifically to a method and system for preparing a seawater hydrogen production catalyst. Background Technology

[0002] With the global energy structure transformation, hydrogen energy, as a clean, efficient, and renewable secondary energy source, has received widespread attention. Hydrogen possesses advantages such as high energy density, pollution-free combustion products, and diverse sources, and is considered an important component of the future energy system. Water electrolysis for hydrogen production, which uses electricity to drive the decomposition of water into hydrogen and oxygen, boasts advantages such as simple process, high product purity, and compatibility with renewable energy power generation, making it a crucial pathway for large-scale green hydrogen production. However, traditional water electrolysis for hydrogen production primarily relies on freshwater resources as raw materials, which are unevenly distributed globally and increasingly scarce, severely hindering the large-scale application of this technology. Seawater resources constitute the vast majority of the Earth's water resources, are abundant and widely distributed, and direct seawater electrolysis for hydrogen production can effectively address the freshwater shortage problem, holding significant importance for hydrogen supply in coastal areas and islands. If seawater electrolysis for hydrogen production can be industrialized, it will open up new avenues for large-scale hydrogen production and promote the development of the hydrogen economy. However, seawater has a complex composition, containing not only water molecules but also large amounts of inorganic salt ions such as chloride, sodium, magnesium, and calcium ions. The presence of chloride ions, in particular, severely hinders the electrolytic hydrogen production process. Chloride ions are highly corrosive and electrochemically active, easily penetrating the catalyst during electrolysis, reacting with active metals in the catalyst through displacement reactions or forming soluble chlorides, leading to the loss of active components and catalyst structural damage. Furthermore, chloride ions can undergo chlorine evolution at the anode surface, competing with oxygen evolution and reducing oxygen evolution efficiency. The resulting chlorine gas is highly toxic and corrosive, posing a threat to equipment and the environment. Therefore, developing high-performance catalysts that can resist chloride ion corrosion and operate stably in seawater environments for extended periods is a key technological bottleneck for achieving direct seawater electrolysis for hydrogen production.

[0003] Currently, research on catalysts for seawater electrolysis to produce hydrogen mainly focuses on two categories: noble metal-based catalysts and transition metal-based catalysts. Noble metal-based catalysts, such as iridium oxides and ruthenium oxides, possess excellent catalytic activity and stability; however, precious metal resources are scarce and expensive, making it difficult to meet the cost requirements for large-scale industrial applications. Transition metal-based catalysts, such as nickel-based, cobalt-based, and iron-based oxides or hydroxides, have the advantages of abundant resources and low cost, but their stability in seawater environments is poor, and they are easily deactivated by chloride ions. Existing methods for preparing transition metal-based catalysts mainly include impregnation, hydrothermal methods, and sol-gel methods. Catalysts prepared by these methods typically suffer from problems such as uneven dispersion of active components, large particle size, and low specific surface area, resulting in insufficient active site density and limited catalytic activity. Furthermore, catalysts prepared by traditional methods lack effective protective layer design, failing to prevent chloride ions from penetrating into the catalyst interior. During seawater electrolysis, the active metal dissolves and is lost rapidly, leading to a sharp decline in catalytic performance and making it difficult to meet the requirements for long-term stable operation. Existing catalyst preparation methods have limited ability to control the microstructure, making it difficult to achieve precise atomic-level control. While traditional electrochemical deposition methods can prepare metal or alloy coatings on conductive substrates, the reduction and deposition of metal ions during the deposition process are random, resulting in disordered atomic arrangement and numerous grain boundary defects. These defects increase scattering losses during electron transport, reducing the catalyst's conductivity and catalytic efficiency. Furthermore, catalysts prepared by traditional methods are typically dense bulk or thin film structures with small specific surface areas and a limited number of exposed active sites, failing to fully realize the catalyst's potential performance. Although some studies have attempted to construct porous structures using template methods or sacrificial template methods, the pore size distribution is uneven, porosity is difficult to control precisely, and the preparation process is complex and costly, hindering industrial production. The microstructure and surface structure of the catalyst surface have a significant impact on the catalytic reaction. Catalytic reactions mainly occur on the surface and near-surface regions of the catalyst. The coordination environment, electronic structure, and adsorption properties of surface atoms determine the catalyst's adsorption capacity for reactants, the stability of reaction intermediates, and the level of the reaction energy barrier. Catalysts prepared by traditional methods typically have relatively flat surfaces, lack effective surface texturing design, and have low surface active site density, limiting the improvement of catalytic performance. While rough structures can be created on the surface using methods such as acid etching and electrochemical etching, these methods struggle to precisely control surface morphology, potentially causing excessive damage to the catalyst structure and reducing stability. Charge transport is a crucial step in the electrocatalytic process; electrons must travel from the external circuit through the current collector and catalyst to reach the reactive sites, while ions must be transported from the electrolyte to the catalyst surface to participate in the reaction. Any obstruction to charge transport increases polarization loss and reduces energy conversion efficiency.The charge transport efficiency within a catalyst depends on its electronic conductivity and ionic conductivity, both of which are closely related to factors such as the catalyst's composition, structure, and defect density. Existing catalysts suffer from high charge transfer resistance due to numerous grain boundary defects, long electron transport paths, and high contact resistance, resulting in significant ohmic polarization losses under high current density operating conditions, thus limiting their practical application performance.

[0004] Therefore, there is an urgent need to develop a new catalyst preparation method to break through existing technological bottlenecks and promote the industrial application of seawater hydrogen production technology. Summary of the Invention

[0005] To address the problems existing in the background art, the present invention provides a method for preparing a seawater hydrogen production catalyst, comprising the following steps: S1. Substrate Pretreatment: The nickel foam substrate is sequentially cleaned with organic solvents, acid etched, and activated by plasma to obtain an activated substrate. S2. Gradient Alloy Core Layer Preparation: Using the activated substrate as the working electrode, electrochemical deposition is performed in a precursor solution containing nickel, iron, and cobalt salts by applying a gradient-distributed pulsed magnetic field and ultrasound to obtain a NiFeCo ternary alloy layer. The deposited ternary alloy layer is then subjected to cryogenic treatment, directional sublimation, and chemical vapor deposition to form a gradient alloy core layer with a hierarchical porous nanofiber array structure. S3. Ternary Permeation Barrier Layer Preparation: Atomic layer deposition (ALD) was used to deposit W, Mo, and Cr layers sequentially on the surface of the gradient alloy core layer to form a W-Mo-Cr ternary permeation barrier layer; S4, Phase change texturing treatment: The material obtained in S3 was subjected to programmed temperature heat treatment in a mixed atmosphere of hydrogen and argon to form a nanotextured structure on the catalyst surface through alloy phase change; S5, Electric field assisted surface modification: The material obtained in S4 was placed in an electrochemical cell, and a spatially gradient electric field was applied in an alkaline electrolyte to form an ion concentration gradient layer, thus obtaining a seawater hydrogen production catalyst.

[0006] In a preferred embodiment, step S1 includes the following steps: S11. Organic solvent cleaning: The nickel foam substrate is sequentially immersed in acetone, anhydrous ethanol, and deionized water, and ultrasonically cleaned for 10-20 minutes in each solvent to remove surface oil and organic residues. S12. Acid etching: The substrate cleaned in S11 is immersed in a 3-7% (w / w) dilute sulfuric acid solution for 20-40 seconds, then rinsed with deionized water until the pH is neutral to remove the surface oxide layer and inorganic impurities, resulting in a clean substrate. S13. Plasma activation: The substrate treated in S12 is placed in an argon plasma treatment chamber and treated for 8-15 minutes at a radio frequency power of 80-120W and a pressure of 0.08-0.15 Torr to improve the surface activity of the substrate and obtain an activated substrate.

[0007] In a preferred embodiment, the precursor solution of S2 is prepared by dissolving Ni(NO3)2·6H2O (0.10-0.15M), Fe(NO3)3·9H2O (0.03-0.06M), Co(NO3)2·6H2O (0.01-0.03M), and hexamethylenetetramine (0.08-0.12M) in deionized water, and adjusting the pH of the solution to 6.0-7.0 with ammonia water to obtain the precursor solution.

[0008] In a preferred embodiment, the step of applying a gradient-distributed pulsed magnetic field and ultrasound for electrochemical deposition in S2 includes: S21. Magnetic Field Setup: Magnetic field generating devices are installed at different spatial locations within the electrochemical deposition area. The magnetic field strength is sequentially set from the substrate surface to the depth of the solution at 0.3-0.7T, 0.8-1.2T, and 1.3-1.7T to form a gradient magnetic field. The magnetic field pulse frequency is set to 8-60Hz. S22. Ultrasonic Application: Ultrasonic waves are applied to the precursor solution at a frequency of 25-32kHz and a power density of 20-45W / cm². 2 Ultrasonic waves enhance the mass transfer of ions in the solution; S23, pulsed electrodeposition: under the simultaneous action of S21 and S22, electrochemical deposition is performed using an activated substrate as the working electrode, employing a square wave pulsed current with a current density of 4-18 mA / cm². 2 With a duty cycle of 60-80%, a deposition time of 35-55 minutes, and a solution temperature controlled at 40-50℃, a NiFeCo ternary alloy layer with atomically ordered arrangement was deposited on the substrate surface under the synergistic effect of magnetic field orientation and ultrasonic enhanced mass transfer.

[0009] In a preferred embodiment, the steps of freezing, directional sublimation, and chemical vapor reconstruction of the deposited ternary alloy layer in step S2 include: S24. Cryogenic Treatment: The ternary alloy layer obtained by electrochemical deposition is placed in a rapid freezing device and cooled to -150℃ to -200℃ at a freezing rate of 40-60℃ / min, and held for 1.5-2.5 hours to form a template of oriented ice crystals inside the alloy layer; S25. Directional Sublimation: The material frozen in S24 is transferred to a vacuum of 5×10⁻⁶. -4 -2×10 -3In a vacuum chamber of Pa, the temperature is increased from -100℃ to -10℃ at a heating rate of 3-7℃ / h. Ice crystals sublimate directionally under vacuum conditions, forming a directionally arranged pore structure within the alloy layer. S26, Chemical Vapor Reconstruction: The material after S25 sublimation is placed in a tube furnace, and a mixed gas with a volume ratio of Ar to H2 of 3:1 to 5:1 is introduced at a total flow rate of 80-120 ml / min. The furnace is treated at 320-380℃ for 1.5-2.5 hours, during which nanofibers are grown in situ within the pores, forming a hierarchical porous nanofiber array structure with an outer fiber diameter of 40-90 nm, a middle fiber diameter of 130-220 nm, and an inner fiber diameter of 280-550 nm, thus completing the preparation of the gradient alloy core layer.

[0010] In a preferred embodiment, step S3 includes the following steps: S31. Equipment Pretreatment: Heat the reaction chamber of the atomic layer deposition equipment to 220-260℃ and evacuate to a pressure below 1×10⁻⁶. -6 Torr: Purge with nitrogen for 25-35 minutes to remove impurities and moisture from the chamber; S32, W layer deposition: Place the gradient alloy core layer obtained in S2 in the reaction chamber, control the substrate temperature at 190-210℃, introduce WF6 precursor for pulse deposition, pulse for 0.3-0.7 seconds, then purge with nitrogen for 8-12 seconds, followed by H2O pulse for 0.2-0.5 seconds, then purge with nitrogen for 12-18 seconds, repeat the cycle 15-25 times to deposit the W layer on the surface of the gradient alloy core layer; S33, Mo layer deposition: After S32, keep the substrate temperature constant, switch to MoO2Cl2 precursor, heat MoO2Cl2 to 90-110℃ to vaporize it, pulse for 0.8-1.3 seconds, then introduce nitrogen. After purging for 8-12 seconds, a H2O pulse is introduced for 0.4-0.6 seconds, followed by a nitrogen purging for 12-18 seconds. This cycle is repeated 10-20 times to deposit a Mo layer on the W layer surface. S34 and Cr layer deposition: After S33, keeping the substrate temperature constant, switch to the CrO2Cl2 precursor. Heat the CrO2Cl2 to 70-90℃ to vaporize it. A CrO2Cl2 pulse is introduced for 0.6-1.0 seconds, followed by a nitrogen purging for 8-12 seconds, then an H2O pulse is introduced for 0.3-0.5 seconds, followed by a nitrogen purging for 12-18 seconds. This cycle is repeated 8-15 times to deposit a Cr layer on the Mo layer surface, forming a ternary permeation barrier layer with a total thickness of 8-60 nm and an elemental molar ratio of W:Mo:Cr of 3.5:2.8:1.8 to 4.5:3.5:2.5.

[0011] In a preferred embodiment, step S4 includes the following steps: S41. Loading and Atmosphere Preparation: Place the material obtained in S3 into the quartz boat of the tube furnace, seal the furnace tube, and introduce a mixture of hydrogen and argon gas. The volumetric flow rate ratio of hydrogen to argon is 1:3 to 1:5, the total flow rate is 80-120 ml / min, and the gas purity is ≥99.99%. Purge for 15-25 minutes to remove air from the furnace tube. S42. Programmed Temperature Increase: Increase the temperature from room temperature to 280-320℃ at a rate of 1.5-3.0℃ / min, maintaining a continuous flow of the mixed gas during the heating process. The material temperature rises uniformly; S43, phase transformation heat preservation: heat preservation at 280-320℃ for 3-5 hours, with temperature fluctuation controlled within ±2℃. In the reducing atmosphere, the NiFe alloy undergoes a γ→α phase transformation, and the volume change generated by the phase transformation forms a nano-pit array texture with a depth of 4-25nm on the catalyst surface; S44, cooling: turn off the heating system, keep the mixed gas flow rate constant, and allow the material to cool naturally to room temperature in the reducing atmosphere. The cooling rate is controlled at ≤5℃ / min to complete the phase transformation texturing treatment.

[0012] In a preferred embodiment, step S5 includes the following steps: S51. Electrochemical Cell Assembly: Using the material obtained in S4 as the working electrode, it is assembled into an electrochemical cell along with a platinum sheet counter electrode, an Ag / AgCl reference electrode, and a graphite rod auxiliary electrode. A 0.8-1.2M KOH solution is added as the electrolyte, and the distance between the working electrode and the counter electrode is adjusted to 200-500 μm. S52. Gradient Electric Field Application: A voltage signal is applied to the surface of the working electrode using a programmable power supply. This voltage signal is composed of a DC bias voltage and an AC modulation voltage. The DC bias voltage is 0.2-0.4V, and the AC modulation voltage amplitude is ±0.15-0.25V with a frequency of 0.8-1.5kHz. By adjusting the electrode spacing and voltage, a spatially gradient electric field is formed inside the catalyst. S53. Electric Field Treatment: Under the voltage conditions set in S52, the catalyst is treated for 25-35 minutes. During the treatment, the electrolyte temperature is maintained at 20-30℃, and the stirring speed is 80-120 rpm. Under the action of the gradient electric field, OH- ions are formed inside the catalyst. - A gradient distribution of ion concentration that gradually increases from the surface to the interior; S54, Cleaning and Drying: After treatment, remove the working electrode and rinse it with deionized water 3-5 times, 2-5 minutes each time, to remove residual electrolyte on the surface. Then dry it with nitrogen gas and place it at a temperature of 50-70℃ and a vacuum degree of 5×10 -2 -2×10 -1 The seawater hydrogen production catalyst was obtained by storing it in a drying oven.

[0013] This invention also provides a seawater hydrogen production catalyst preparation system, including a substrate pretreatment device, a gradient alloy core layer preparation device, a ternary permeation barrier layer preparation device, a phase change texturing treatment device, and an electric field-assisted surface modification device. The substrate pretreatment device is used to clean, etch, and activate a nickel foam substrate. It includes an ultrasonic cleaning unit, an acid etching unit, and a plasma activation unit. The ultrasonic cleaning unit is equipped with a cleaning tank and an ultrasonic generator; the acid etching unit is equipped with an etching pool and a solution circulation system; and the plasma activation unit includes a plasma treatment chamber, a radio frequency power supply, and a vacuum pump. The gradient alloy core layer preparation device includes an electrochemical deposition unit and a cryogenic pore-forming unit. The electrochemical deposition unit is equipped with an electrochemical reactor, three sets of electromagnetic coils, a magnetic field controller, an ultrasonic transducer, and a temperature control system. The cryogenic pore-forming unit includes a rapid freezing chamber, a directional sublimation vacuum chamber, and a tubular vapor phase reconstruction furnace. The ternary permeation barrier layer preparation device is an atomic layer deposition device, which includes a reaction chamber, multiple precursor tanks, a gas distribution system, and a vacuum system for sequentially depositing tungsten, molybdenum, and chromium layers. The phase change texturing apparatus includes a tubular furnace, a gas mixing and delivery system, and a temperature programmable controller, used for heat treatment in a mixed atmosphere of hydrogen and argon to form surface nanotextures. The electric field-assisted surface modification apparatus includes an electrochemical cell, a gradient electric field generator, and a position adjustment mechanism. The electrochemical cell is equipped with a working electrode region, a counter electrode region, a reference electrode region, and an auxiliary electrode region. The gradient electric field generator includes a programmable power supply and electric field control circuitry. The entire system is also equipped with a centralized control system for coordinating the operation of each device and achieving automated control. This system can efficiently and stably prepare seawater hydrogen production catalysts with high catalytic activity and strong corrosion resistance.

[0014] The beneficial effects achieved by this invention are as follows: First, this invention employs a gradient magnetic field-assisted electrochemical deposition technique to prepare gradient alloy core layers. During electrodeposition, a three-level gradient magnetic field with increasing intensity is applied from the substrate surface to the depth of the solution. Simultaneously, ultrasonic waves are used to enhance mass transfer, causing the atoms of the nickel-iron-cobalt ternary alloy to align orderly along specific crystal orientations, forming a textured crystal structure. This reduces grain boundary defect density, decreases scattering losses during electron transport, and improves the intrinsic conductivity of the alloy. The Lorentz force generated by the gradient magnetic field on metal ions promotes the exposure of low-index crystal planes. These planes possess superior adsorption energy and lower reaction energy barriers for oxygen evolution reaction intermediates, thereby significantly enhancing the intrinsic activity of the catalyst. A hierarchical porous nanofiber array structure was constructed within a dense ternary alloy layer using cryogenic directional sublimation and chemical vapor deposition techniques. The outer layer of fine fibers, with diameters ranging from 40 nm to 90 nm, provides numerous highly active sites; the middle layer of medium-sized fibers, with diameters ranging from 130 nm to 220 nm, constitutes electron transport channels; and the inner layer of coarse fibers, with diameters ranging from 280 nm to 550 nm, provides structural support. This three-tiered gradient synergy enables the catalyst to achieve a specific surface area of ​​85 m². 2 / g, electrochemically active surface area exceeding 1000 cm² 2 The density of active sites is more than three times higher than that of traditional methods, providing abundant reaction centers for efficient catalytic reactions.

[0015] Secondly, this invention employs atomic layer deposition (ALD) technology to deposit tungsten, molybdenum, and chromium layers sequentially, forming a ternary permeation barrier layer with a total thickness of 8 nm to 60 nm, achieving multiple layers of protection against chloride ion corrosion in seawater. The tungsten layer, as the first barrier, possesses extremely high chemical stability and density, effectively blocking the initial penetration of chloride ions. The molybdenum layer forms stable coordination bonds with chloride ions, further intercepting a small number of chloride ions penetrating the tungsten layer through chemisorption, reducing the migration rate of chloride ions into the inner layers. The chromium layer, as the outermost layer, forms a dense passivation film in the alkaline electrolyte, preventing electrolyte penetration into the interior and maintaining the integrity of the protective layer through a self-healing mechanism. The lattice mismatch and chemical potential gradient formed at the interface of the ternary composite structure further enhance the barrier effect against ion penetration. Compared to the microscopic defects and pinholes present in single-layer barrier layers, the ternary composite barrier layer significantly improves density and integrity through multi-layer synergy. After 1000 hours of constant potential electrolysis in a simulated seawater environment containing 3.5% sodium chloride, the current density retention rate of the catalyst is still as high as 94.5%, the resistance to chloride ion corrosion is significantly enhanced, and the long-term stability is fundamentally improved.

[0016] Third, this invention induces a solid-state phase transition from the gamma phase to the alpha phase in a nickel-iron alloy through programmed temperature heat treatment in a mixed atmosphere of hydrogen and argon. The volume change during this phase transition creates an in-situ nano-pit array texture with a depth of 4 nm to 25 nm on the catalyst surface. The edges and bottoms of these nano-pits generate numerous step and twist sites. These sites have unsaturated atomic coordination, dangling bonds, and localized electronic states, significantly enhancing their adsorption capacity for oxygen evolution reaction intermediates such as hydroxide ions, oxygen atoms, and peroxyhydroxide ions. The nano-pit structure also improves the wettability between the electrolyte and the catalyst surface, promoting rapid replenishment of reactants and timely desorption of product bubbles, reducing the loss of effective reaction area caused by the bubble shielding effect. Compared to catalysts with smooth surfaces, nanotexturing treatment increases the density of effective active sites by more than 30%, reduces the overpotential of oxygen evolution reaction by 20mV to 40mV, decreases the Tafel slope by 10mV / dec to 20mV / dec, significantly accelerates reaction kinetics, and makes the catalytic performance advantage more obvious in the high current density region.

[0017] Fourth, this invention applies a composite voltage signal, consisting of a DC bias voltage and an AC modulation voltage, to the electrochemical cell, creating a spatially gradient electric field within the catalyst. This drives hydroxide ions in the electrolyte to migrate along the electric field direction, establishing an ion concentration gradient layer that gradually increases from the surface to the interior. The lower hydroxide concentration at the surface layer facilitates oxygen evolution and desorption, reducing product inhibition and lowering the overpotential of the oxygen evolution reaction. The higher hydroxide concentration in the inner layer provides sufficient reactants for the catalytic reaction, avoiding performance degradation due to ion mass transfer limitations. The chemical potential difference generated by the concentration gradient promotes ion diffusion from high-concentration to low-concentration regions, and the gradient electric field enhances electron-ion coupling and transport, reducing interfacial charge transfer resistance. This electric field-assisted modification reduces the catalyst's charge transfer resistance by 20% to 30%, significantly improves electron transport efficiency, reduces ohmic polarization loss, and enables the catalyst to maintain efficient and stable operation at higher current densities, meeting the requirements of industrial-scale seawater electrolysis for high-current-density hydrogen production.

[0018] Fifth, this invention constructs a multi-level composite catalyst with a gradient alloy core layer, hierarchical porous nanofiber array, ternary permeation barrier layer, nanotextured surface, and gradient ion distribution layer by combining gradient magnetic field induced deposition, cryogenic directional sublimation pore-forming, chemical vapor phase reconstruction, ternary composite barrier layer deposition, phase change texturing, and gradient electric field modification techniques. 2 The oxygen evolution reaction overpotential is only 250 mV to 270 mV, the Tafel slope is 60 mV / dec to 70 mV / dec, and the electrochemically active surface area exceeds 1000 cm². 2 The charge transfer resistance is as low as 2.8 Ω·cm. 2 After 1000 hours of continuous electrolysis in a simulated seawater environment containing chloride ions, the current density retention rate was greater than 93%, and all five key performance indicators were superior to catalysts prepared by traditional methods. This invention achieves synergistic optimization of catalytic activity, reaction kinetics, active area, charge transport, and long-term stability, breaking through the technical bottlenecks of easy corrosion, low activity, and short lifespan of catalysts in direct seawater electrolysis for hydrogen production. It provides a high-performance, long-life catalytic material solution for the large-scale industrial application of seawater hydrogen production technology, possessing significant scientific value and broad application prospects. Attached Figure Description

[0019] Figure 1 This is a comparison graph of the oxygen evolution reaction overpotential (OER) of Comparative Example 1 and each comparative example.

[0020] Figure 2 This is a comparison chart of the Tafel slopes of Example 1 and each comparative example.

[0021] Figure 3 This is a comparison chart of the current density retention rate of Example 1 and each comparative example after 1000 hours of electrolysis.

[0022] Figure 4 This is a comparison graph of the electrochemically active surface area (ECSA) of Example 1 and each comparative example.

[0023] Figure 5 This is a comparison chart of the charge transfer resistance (Rct) of Example 1 and each comparative example.

[0024] Figure 6 This is a flowchart of the seawater hydrogen production catalyst preparation method of the present invention.

[0025] Figure 7 This is a structural diagram of the seawater hydrogen production catalyst preparation system of the present invention. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. In addition, the forms of the various structures described in the following embodiments are merely illustrative. The present invention is not limited to the structures described in the following embodiments. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Reference Figure 6 This invention provides a method for preparing a seawater hydrogen production catalyst, comprising five main steps: substrate pretreatment, gradient alloy core layer preparation, ternary permeation barrier layer preparation, phase change texturing treatment, and electric field-assisted surface modification. The steps are interconnected to form a complete preparation process.

[0028] In step S1, substrate pretreatment is performed to obtain a clean and highly active nickel foam (Ni) substrate, providing favorable nucleation sites for subsequent electrochemical deposition. Specifically, step S1 includes three sub-steps: S11 organic solvent cleaning, S12 acid etching, and S13 plasma activation treatment. In step S11, the nickel foam (Ni) substrate is sequentially immersed in acetone, anhydrous ethanol, and deionized water, and ultrasonically cleaned for a certain period of time in each solvent. The microjets and shock waves generated by ultrasonic cavitation effectively remove oil and organic residues from the substrate surface. Acetone, as a highly polar solvent, dissolves most organic oil and grease contaminants; anhydrous ethanol further removes residual polar organic matter; and deionized water rinsing removes solvent residues, ensuring the cleanliness of the substrate surface. The ultrasonic cleaning time is preferably 10 to 20 minutes; too short a time results in insufficient cleaning, while too long a time may cause excessive erosion of the substrate surface.

[0029] In step S12, the cleaned substrate is immersed in a 3% to 7% (w / w) dilute sulfuric acid (H2SO4) solution for 20 to 40 seconds, then rinsed with deionized water until the pH is neutral. The purpose of the dilute sulfuric acid (H2SO4) solution is to remove the oxide layer and inorganic impurities on the substrate surface, exposing a fresh metal surface. Nickel foam (Ni) naturally forms a nickel oxide (NiO) layer in the air, which hinders subsequent electrochemical deposition and reduces the adhesion between the plating layer and the substrate. Dilute sulfuric acid (H2SO4) chemically converts nickel oxide (NiO) into soluble nickel sulfate (NiSO4), thereby removing the oxide layer. The mass fraction of sulfuric acid (H2SO4) and the immersion time need to be strictly controlled. Too low a concentration or too short a time will result in insufficient removal, while too high a concentration or too long a time may over-corrode the substrate, damaging the three-dimensional network structure of the nickel foam (Ni). After immersion, the substrate is immediately rinsed thoroughly with deionized water until the pH returns to neutral to prevent residual acid from continuing to corrode the substrate or affecting subsequent processes.

[0030] In step S13, the treated substrate is placed in an argon (Ar) plasma treatment chamber for plasma activation. The process parameters for plasma treatment include radio frequency power, gas pressure, and treatment time. The radio frequency power is preferably 80W to 120W, the gas pressure is preferably 0.08 Torr to 0.15 Torr, and the treatment time is preferably 8 min to 15 min. Argon (Ar) plasma contains high-energy particles, excited-state atoms, and ions. These active species bombard the substrate surface, further removing residual organic contaminants and simultaneously generating numerous dangling bonds and defect sites, significantly improving surface energy and chemical activity. The plasma-activated substrate has more nucleation sites, which is beneficial for the uniform nucleation and growth of the alloy layer during subsequent electrochemical deposition, thereby improving the density and bonding strength of the coating. Through this series of pretreatment operations, a clean and highly active activated substrate is finally obtained, laying a good foundation for the subsequent preparation of the gradient alloy core layer.

[0031] In step S2, a gradient alloy core layer is prepared by combining gradient magnetic field, ultrasonic-assisted electrochemical deposition, and cryogenic directional sublimation pore-forming technology to construct a gradient alloy core layer with a hierarchical porous nanofiber array structure on the substrate surface. Step S2 first requires the preparation of a precursor solution containing nickel salt, iron salt, cobalt salt, and a complexing agent. Specifically, the preparation method involves dissolving nickel nitrate hexahydrate (Ni(NO3)2·6H2O) at a concentration of 0.10 mol / L to 0.15 mol / L, ferric nitrate nonahydrate (Fe(NO3)3·9H2O) at a concentration of 0.03 mol / L to 0.06 mol / L, cobalt nitrate hexahydrate (Co(NO3)2·6H2O) at a concentration of 0.01 mol / L to 0.03 mol / L, and hexamethylenetetramine at a concentration of 0.08 mol / L to 0.12 mol / L in deionized water. Hexamethylenetetramine acts as both a complexing agent and a pH buffer in solution. It forms complexes with metal ions, reducing their activity and making the deposition process more stable and controllable. Simultaneously, hexamethylenetetramine hydrolyzes slowly in solution, releasing hydroxide ions (OH-). - To maintain the stability of the solution's pH, after preparation, ammonia was used to adjust the pH to 6.0 to 7.0. This pH range ensures that metal ions do not prematurely hydrolyze and precipitate while providing a suitable ionic environment for electrochemical deposition. The concentration ratio of the three metal elements—nickel (Ni), iron (Fe), and cobalt (Co)—was optimized. Nickel (Ni), as the main component, provides catalytic activity and structural stability; the addition of iron (Fe) regulates the electronic structure and enhances intrinsic activity; and cobalt (Co) improves charge transfer kinetics. The synergistic effect of these three elements significantly improves the overall performance of the catalyst.

[0032] In step S21, a gradient-distributed pulsed magnetic field is set. Magnetic field generating devices are placed at different spatial locations in the electrochemical deposition area, with magnetic field strengths sequentially set from the substrate surface to the depth of the solution as 0.3T to 0.7T, 0.8T to 1.2T, and 1.3T to 1.7T, forming a three-level gradient magnetic field. The magnetic field pulse frequency is set to 8Hz to 60Hz. The introduction of the gradient magnetic field is an important technical feature of this invention, as the magnetic field has multiple effects on the electrochemical deposition process. The magnetic field exerts a Lorentz force on metal ions in the solution, altering the ion trajectory and enhancing the mass transfer rate to the electrode surface. The magnetic field also affects the current density distribution on the electrode surface, promoting the uniformity of the deposition layer. More importantly, the gradient magnetic field induces a directional effect on the microstructure of the alloy during deposition, causing alloy atoms to align along specific directions, forming a textured crystal structure. Compared to a constant magnetic field, the pulsed magnetic field has stronger penetration capability and more significant micro-control effect. The selection of the pulse frequency needs to match the time scale of the deposition process; too low a frequency cannot effectively control atomic arrangement, while too high a frequency may cause excessive internal stress in the deposition layer, leading to cracking.

[0033] In step S22, ultrasonic assistance is applied to the precursor solution at a frequency of 25 kHz to 32 kHz and a power density of 20 W / cm². 2 Up to 45W / cm 2 Ultrasonic waves propagate through liquids, generating cavitation, a process characterized by the rapid formation, growth, and collapse of tiny bubbles. The collapse of these bubbles creates instantaneous high-temperature, high-pressure environments and intense microjets in localized areas. These effects significantly enhance the mass transfer rate of ions in the solution, disrupt the diffusion boundary layer on the electrode surface, and allow fresh solution to continuously replenish the electrode surface, ensuring the current efficiency and deposition rate of the deposition process. The shock waves generated by ultrasonic cavitation also exert periodic mechanical impacts on the growing deposition layer, refining grain size and increasing the density of the deposition layer. The selection of ultrasonic frequency and power density requires comprehensive consideration of the intensity of the cavitation effect and the physicochemical properties of the solution. Too low a frequency and power will not produce sufficient cavitation, while too high a frequency and power may lead to excessively rapid temperature increases or excessive mechanical damage.

[0034] In step S23, pulsed electrodeposition is performed under the simultaneous action of a gradient magnetic field and ultrasound, using an activated substrate as the working electrode for electrochemical deposition. A square wave pulsed current mode is employed, which offers better deposition quality control compared to direct current. The characteristic parameters of the pulsed current include current density, duty cycle, and deposition time. The preferred current density is 4 mA / cm². 2 Up to 18 mA / cm 2 The duty cycle is preferably 60% to 80%, and the deposition time is preferably 35 min to 55 min. During pulse deposition, metal ions are reduced and deposited on the cathode surface during the on-time, and the ion concentration near the electrode surface is restored during the off-time. Simultaneously, the deposited atoms have time for surface diffusion and rearrangement, forming a more ordered crystal structure. The duty cycle, i.e., the ratio of the on-time to the total cycle time, directly affects the microstructure and performance of the deposited layer. The solution temperature is controlled between 40℃ and 50℃. Appropriately increasing the temperature improves the ion diffusion rate and electrode reaction kinetics, but excessively high temperatures lead to accelerated solution evaporation and increased side reactions. Under the synergistic effect of gradient magnetic field orientation and ultrasonic-enhanced mass transfer, a nickel-iron-cobalt ternary alloy layer with ordered atomic arrangement and uniform composition distribution is deposited on the substrate surface. In this alloy layer, nickel (Ni), iron (Fe), and cobalt (Co) form a solid solution structure, and the synergistic effect between the elements provides abundant active sites and excellent electronic conductivity for the catalyst.

[0035] The subsequent processing of step S2 includes three sub-steps: step S24 freezing, step S25 directional sublimation, and step S26 chemical vapor phase reconstruction. The purpose of this series of processes is to construct a hierarchical porous nanofiber array structure within the dense alloy layer, significantly increasing the specific surface area and active site density of the catalyst. In step S24, the ternary alloy layer obtained by electrochemical deposition is placed in a rapid freezing device and cooled to -150°C to -200°C at a freezing rate of 40°C / min to 60°C / min, held for 1.5h to 2.5h. During rapid freezing, the adsorbed water and residual solution inside the alloy layer quickly freeze. Due to the rapid cooling rate, the ice crystals do not have time to expand laterally but instead grow directionally along the temperature gradient, forming an oriented ice crystal template. The growth of the ice crystals exerts a compressive effect on the surrounding alloy matrix, creating a micro-stress field within the alloy. The holding time needs to be long enough to ensure sufficient freezing, and the temperature needs to be low enough to prevent recrystallization of the ice crystals before subsequent processing.

[0036] In step S25, the frozen material is transferred to a vacuum of 5 × 10⁻⁶. -4 Pa to 2×10 -3 In a vacuum chamber of Pa, the temperature is increased from -100℃ to -10℃ at a rate of 3℃ / h to 7℃ / h. Under vacuum conditions, ice crystals sublimate directly into a gaseous state without passing through a liquid stage; this process is called freeze-drying or sublimation drying. Because the ice crystals are oriented, sublimation leaves an oriented pore structure within the alloy layer corresponding to the ice crystal morphology. The heating rate needs to be strictly controlled; excessively rapid heating will cause partial melting of the ice crystals, destroying the orientation of the pores, while excessively slow heating will result in excessively long processing times and reduced production efficiency. The choice of vacuum level is also crucial; too low a vacuum will lead to a slow sublimation rate or melting of the ice crystals, while too high a vacuum, although beneficial for sublimation, will increase equipment costs. By controlling the freezing and sublimation conditions, the size, morphology, and orientation of the pores can be precisely controlled, providing a template for the subsequent in-situ growth of nanofibers.

[0037] In step S26, chemical vapor reconstruction is performed. The sublimated material is placed in a tube furnace, and a mixture of argon (Ar) and hydrogen (H2) in a volume ratio of 3:1 to 5:1 is introduced at a total flow rate of 80 mL / min to 120 mL / min. The furnace is treated at 320°C to 380°C for 1.5 h to 2.5 h. Under reducing atmosphere and high temperature conditions, complex physicochemical changes occur inside the alloy layer. Hydrogen (H2), as a reducing gas, reduces oxides on the alloy surface, while hydrogen atoms diffuse into the alloy lattice, causing lattice expansion and structural reorganization. Argon (Ar), as an inert protective gas, prevents the alloy from being oxidized at high temperatures. Inside the pores, driven by surface energy and atomic diffusion, alloy atoms rearrange and aggregate, growing nanofiber structures in situ along the pore walls. The diameter of the nanofibers is affected by various factors, including pore size, processing temperature, atmosphere composition, and processing time. By optimizing process parameters, hierarchical control can be achieved, forming fine fibers with diameters of 40 nm to 90 nm in the outer layer of the alloy layer, medium fibers with diameters of 130 nm to 220 nm in the middle layer, and coarse fibers with diameters of 280 nm to 550 nm in the inner layer, thus constituting a hierarchical porous nanofiber array structure. This hierarchical structure has multiple advantages: fine fibers provide a large number of active sites, medium fibers provide good electron conduction channels, and coarse fibers provide structural support and mechanical strength. The three work synergistically to ensure that the catalyst maintains high activity and stability even at high current densities. After chemical vapor phase reconstruction, a gradient alloy core layer with a hierarchical porous nanofiber array structure is obtained. This core layer provides the catalyst with a high specific surface area, abundant active sites, and excellent charge transport performance.

[0038] In step S3, a ternary permeation barrier layer is prepared. The function of this layer is to prevent chloride ions (Cl-) from entering the seawater. - Sodium ions (Na⁺) and sodium ions (Na⁺) permeate into the alloy core layer, while preventing metal ions in the alloy from migrating and dissolving outwards, thus significantly improving the catalyst's corrosion resistance and long-term stability in seawater environments. The ternary permeation barrier layer is prepared using atomic layer deposition (ALD), a thin film growth technique based on surface self-limiting reactions, achieving atomic-level thickness control and excellent conformability, enabling uniform deposition even on complex three-dimensional porous surfaces. Step S3 includes four sub-steps: step S31 equipment pretreatment, step S32 tungsten layer deposition, step S33 molybdenum layer deposition, and step S34 chromium layer deposition. In step S31, equipment pretreatment is performed by heating the reaction chamber of the ALD equipment to 220°C to 260°C and evacuating it to a pressure below 1 × 10⁻⁶. -6Torr, nitrogen (N2) is introduced for purging for 25 to 35 minutes. The purpose of equipment pretreatment is to remove impurity gases and moisture from the reaction chamber, creating a clean reaction environment for subsequent atomic layer deposition. Preheating of the chamber temperature accelerates the desorption of impurities, vacuum evacuation removes impurities, and nitrogen (N2) purging further replaces residual impurities. Moisture is the most significant source of contamination during atomic layer deposition because water molecules react non-selectively with the precursor, leading to a decrease in film quality. Therefore, the moisture content in the chamber must be reduced to an extremely low level. In step S32, a tungsten layer is deposited by placing the gradient alloy core layer in the reaction chamber, with the substrate temperature controlled between 190°C and 210°C. Tungsten hexafluoride (WF6) is used as the precursor for tungsten layer deposition, and water (H2O) is used as the reactant. The atomic layer deposition (ALD) process employs alternating pulsed inlet and purging. First, a tungsten hexafluoride (WF6) precursor is pulsed for 0.3 to 0.7 seconds. Precursor molecules chemically adsorb onto the substrate surface, forming a monolayer or sub-monolayer. Then, nitrogen (N2) is purged for 8 to 12 seconds to remove excess precursor and reaction byproducts from the gas phase. Next, water (H2O) is pulsed for 0.2 to 0.5 seconds, and water molecules react with the adsorbed precursor, completing the deposition of one atomic layer. Nitrogen (N2) is then purged again for 12 to 18 seconds to remove reaction products. This process is called one ALD cycle. The cycle is repeated 15 to 25 times to deposit a tungsten layer on the surface of the gradient alloy core. Tungsten (W) possesses a high melting point, high hardness, and excellent corrosion resistance, effectively preventing chloride ions (Cl-) from forming the first barrier layer. - The reaction of tungsten hexafluoride (WF6) with water (H2O) produces tungsten oxide (WO3) and hydrogen fluoride (HF), which is then carried away as a byproduct by nitrogen (N2) purging. Substrate temperature, precursor pulse time, and purging time are key parameters affecting deposition quality and need to be optimized based on specific reaction kinetics. In step S33, a molybdenum layer is deposited. After the tungsten layer deposition is complete, the substrate temperature is kept constant, and the precursor is switched to molybdenum dioxygenate (MoO2Cl2). Molybdenum dioxygenate (MoO2Cl2) is solid at room temperature and needs to be heated to 90°C to 110°C to vaporize. The deposition process also employs alternating pulsed gas introduction and purging. Molybdenum dichloride (MoO2Cl2) is introduced via a pulse for 0.8 to 1.3 seconds, followed by nitrogen (N2) purging for 8 to 12 seconds. Then, water (H2O) is introduced via a pulse for 0.4 to 0.6 seconds, followed by nitrogen (N2) purging for 12 to 18 seconds. This cycle is repeated 10 to 20 times to deposit a molybdenum layer on the tungsten surface. Molybdenum (Mo) also exhibits excellent corrosion resistance, and its electronic structure allows it to react with chloride ions (Cl-). - This forms stable coordination bonds, further enhancing the attraction to chloride ions (Cl). -The tungsten-molybdenum bilayer structure forms a denser and more effective barrier layer through synergistic effects at the interface. In step S34, a chromium layer is deposited. After the molybdenum layer is deposited, the substrate temperature is kept constant, and the precursor chromium dichloride (CrO2Cl2) is switched to. CrO2Cl2 also needs to be heated to 70°C to 90°C to vaporize. During the deposition process, CrO2Cl2 is pulsed for 0.6 to 1.0 seconds, followed by nitrogen (N2) purging for 8 to 12 seconds, then water (H2O) is pulsed for 0.3 to 0.5 seconds, followed by nitrogen (N2) purging for 12 to 18 seconds. This cycle is repeated 8 to 15 times to deposit a chromium layer on the molybdenum layer surface. Chromium (Cr), as the outermost layer of the barrier layer, has the ability to form a dense passivation film in an alkaline environment, which effectively prevents the electrolyte from penetrating into the interior. By controlling the number of deposition cycles of the three elements, the thickness ratio of each layer can be precisely controlled, ultimately forming a ternary permeation barrier layer with a total thickness of 8 nm to 60 nm and an elemental molar ratio of tungsten (W):molybdenum (Mo):chromium (Cr) of 3.5:2.8:1.8 to 4.5:3.5:2.5. This structural design, which deposits the tungsten layer first, then the molybdenum layer, and then the chromium layer, fully utilizes the individual characteristics of the three elements and their synergistic effects to construct a gradient protection system, significantly improving the catalyst's resistance to seawater corrosion.

[0039] In step S4, a phase transformation texturing treatment is performed. This step controls the phase transformation process of the alloy to form a nanoscale textured structure on the catalyst surface, further improving the electrochemical activity of the catalyst. Step S4 includes four sub-steps: step S41, furnace loading and atmosphere preparation; step S42, programmed temperature rise; step S43, phase transformation holding; and step S44, cooling. In step S41, the material after the ternary permeation barrier layer is prepared is placed in a quartz boat of a tube furnace. The furnace tube is sealed, and a mixture of hydrogen (H2) and argon (Ar) gas is introduced. The volume flow ratio of hydrogen (H2) to argon (Ar) is 1:3 to 1:5, the total flow rate is 80 mL / min to 120 mL / min, and the gas purity is ≥99.99%. The furnace tube is purged for 15 min to 25 min to remove air. The high gas purity requirement is because oxygen (O2) and moisture (H2O) can affect the subsequent phase transformation process and the formation of surface structures. The purging time needs to be long enough to ensure that the air in the furnace tube is completely replaced. In step S42, a programmed temperature rise is performed, increasing the temperature from room temperature to 280°C to 320°C at a rate of 1.5°C / min to 3.0°C / min. During this rise, a mixed gas is continuously introduced to ensure a uniform temperature increase. Controlling the heating rate is crucial for the phase transformation process; excessively rapid heating leads to uneven temperature distribution within the material, causing stress concentration and even cracking, while excessively slow heating prolongs the process time and reduces efficiency. During the heating process, hydrogen (H2) begins to reduce the ternary permeation barrier layer and the alloy core layer, removing surface oxides. Simultaneously, hydrogen atoms gradually diffuse into the alloy lattice. In step S43, a phase transformation holding period is performed at 280°C to 320°C for 3 to 5 hours, with temperature fluctuations controlled within ±2°C. Under these temperature range and reducing atmosphere conditions, the nickel-iron alloy undergoes a transformation from a face-centered cubic gamma phase (γ phase) to a body-centered cubic alpha phase (α phase). This phase transformation is a solid-state phase transformation, accompanied by changes in crystal structure and volume. Because the cell volume of the new phase differs from that of the parent phase, volume mismatch occurs at grain and phase boundaries during the phase transition, leading to localized stress concentration. At the surface, this stress release occurs through the rearrangement and migration of surface atoms, ultimately forming a nano-pit array texture with a depth of 4 nm to 25 nm on the catalyst surface. These nano-pits increase surface roughness and specific surface area, providing more edge and step sites, which typically exhibit higher catalytic activity. The holding time needs to be sufficiently long to ensure the phase transition proceeds fully, and temperature fluctuations must be strictly controlled to guarantee the uniformity and repeatability of the phase transition process. Cooling is performed in step S44 by shutting off the heating system, maintaining a constant mixed gas flow rate, and allowing the material to cool naturally to room temperature in a reducing atmosphere at a cooling rate ≤5 °C / min. Slow cooling aims to prevent excessive thermal stress that could cause material cracking or barrier layer peeling. Cooling in a reducing atmosphere prevents surface oxidation and preserves the nano-texture structure formed during the phase transition.Phase change texturing treatment forms an ordered array of nano-pits on the catalyst surface. This surface morphology not only increases the density of active sites but also improves the contact between the electrolyte and the catalyst surface, promoting timely desorption of bubbles and thus enhancing the electrochemical performance of the catalyst.

[0040] In step S5, electric field-assisted surface modification is performed. This step involves applying a spatially gradient electric field to form an ion concentration gradient layer inside the catalyst, further optimizing the catalyst's microstructure and surface properties. Step S5 includes four sub-steps: step S51, electrochemical cell assembly; step S52, gradient electric field application; step S53, electric field treatment; and step S54, cleaning and drying. In step S51, the phase-change textured material is used as the working electrode and assembled into an electrochemical cell along with a platinum sheet counter electrode, a silver chloride reference electrode, and a graphite rod auxiliary electrode. A potassium hydroxide (KOH) solution with a concentration of 0.8 mol / L to 1.2 mol / L is added as the electrolyte, and the distance between the working electrode and the counter electrode is adjusted to 200 µm to 500 µm. The platinum sheet, as the counter electrode, exhibits excellent conductivity and chemical stability; the silver chloride (AgCl) reference electrode provides a stable reference potential; and the graphite rod auxiliary electrode is used to assist in current distribution. The concentration of potassium hydroxide (KOH) solution needs to be selected to balance the conductivity of the electrolyte and the hydroxide ion concentration (OH-). - The concentration of the electrolyte is crucial; too low a concentration leads to high electrolyte resistance, while too high a concentration may cause side reactions. Precise control of the electrode spacing is essential for forming a gradient electric field. Too large a spacing results in insufficient electric field strength, while too small a spacing may lead to electrode short circuits or excessive current density. In step S52, a gradient electric field is applied by applying a voltage signal to the working electrode surface via a programmable power supply. This voltage signal is composed of a DC bias voltage and an AC modulation voltage. The DC bias voltage is 0.2V to 0.4V, and the AC modulation voltage amplitude is ±0.15V to ±0.25V, with a frequency of 0.8kHz to 1.5kHz. The DC bias voltage establishes a constant electric field on the catalyst surface, driving ions in the electrolyte to migrate into the catalyst. The AC modulation voltage, superimposed on the DC bias voltage, generates a periodically changing electric field. This alternating electric field enhances the ion migration rate while preventing continuous electrochemical reactions on the electrode surface that could alter the surface structure. By adjusting the electrode spacing and voltage parameters, a spatially gradient electric field is formed inside the catalyst, meaning the electric field strength gradually decreases from the catalyst surface inwards. In step S53, electric field treatment is performed under the set voltage conditions for 25 to 35 minutes, maintaining the electrolyte temperature at 20°C to 30°C and the stirring speed at 80 to 120 r / min during the treatment. Under the influence of the gradient electric field, hydroxide ions (OH-) in the electrolyte... -Driven by the electric field, ions migrate into the interior of the catalyst. Due to the gradient distribution of the electric field strength, the migration rate and depth of the ions also exhibit gradient changes, ultimately forming hydroxide ions (OH-) inside the catalyst. - The electrolyte exhibits a gradient distribution of ion concentration that gradually increases from the surface to the interior. This ion concentration gradient layer plays a crucial role; the low hydroxyl concentration at the surface facilitates the evolution and desorption of oxygen (O2), while the high hydroxyl concentration in the inner layer provides sufficient reactants for the catalytic reaction. Simultaneously, the chemical potential difference generated by the concentration gradient promotes the transport of ions and electrons. Controlling the electrolyte temperature is essential to maintain the stability of the electrolyte properties. Excessive temperature accelerates water evaporation and changes in electrolyte concentration, while excessively low temperature reduces ion migration rates. Appropriate stirring maintains the uniformity of the electrolyte composition and prevents excessively large local concentration differences. In step S54, cleaning and drying are performed. After the electric field treatment is completed, the working electrode is removed and rinsed 3 to 5 times with deionized water, each rinse lasting 2 to 5 minutes, to remove residual electrolyte from the surface. If residual electrolyte is not completely removed, it will continue to react with the catalyst during subsequent storage, affecting the catalyst's performance and stability. The surface moisture is dried with nitrogen (N2), and then the electrode is placed at a temperature of 50°C to 70°C and a vacuum of 5 × 10⁻⁶. -2 Pa to 2×10 -1 The catalyst is stored in a drying oven at a pressure of Pa. Vacuum drying thoroughly removes moisture from the catalyst pores, preventing oxidation or corrosion caused by moisture. Simultaneously, the vacuum environment isolates the catalyst from air, protecting its stability during storage. Thus, the preparation of the seawater hydrogen production catalyst is complete.

[0041] To achieve the above-described method for preparing a seawater hydrogen production catalyst, this invention also provides a system for preparing a seawater hydrogen production catalyst. (Refer to...) Figure 7The device includes: a substrate pretreatment apparatus comprising an ultrasonic cleaning unit, an acid etching unit, and a plasma activation unit connected in sequence; the ultrasonic cleaning unit is equipped with a cleaning tank containing organic solvent and deionized water, and an ultrasonic generator; the acid etching unit is equipped with an etching pool containing dilute sulfuric acid solution; and the plasma activation unit includes a plasma treatment chamber, a radio frequency power supply, and a vacuum pump; and a gradient alloy core layer preparation apparatus comprising an electrochemical deposition unit and a cryogenic pore-forming unit; the electrochemical deposition unit includes an electrochemical reactor, three sets of electromagnetic coils arranged in layers along the height direction, a magnetic field controller, an ultrasonic transducer, and a temperature... The electrochemical reactor includes a working electrode support, a counter electrode, and a reference electrode. Three sets of electromagnetic coils correspond to the bottom, middle, and top regions of the reactor, respectively, to generate a gradient magnetic field. A magnetic field controller is electrically connected to the three sets of electromagnetic coils to independently control the magnetic field strength and pulse frequency of each set. An ultrasonic transducer is installed at the bottom of the reactor to emit ultrasonic waves into the solution. The cryogenic pore-forming unit includes a rapid freezing chamber, a directional sublimation vacuum chamber, and a tubular vapor phase reconstruction furnace. The rapid freezing chamber is equipped with a liquid nitrogen circulation system. The sublimation vacuum chamber is equipped with a vacuum pump and a heating system, and the tubular vapor phase reconstruction furnace is equipped with a mixed gas input system. The ternary permeation barrier layer preparation device, an atomic layer deposition apparatus, includes a reaction chamber, sequentially arranged W precursor tanks, Mo precursor tanks, and Cr precursor tanks, a gas distribution system, and a vacuum system. A substrate heating stage is installed within the reaction chamber. The gas distribution system includes a carrier gas pipeline, a purge gas pipeline, and a precursor delivery pipeline. The precursor delivery pipeline connects to the three precursor tanks and the reaction chamber respectively. The phase change texturing treatment device includes a tubular furnace, a gas mixing and delivery system, and a temperature program. The controller includes a tubular furnace with a heating zone and a quartz furnace tube. The gas mixing and delivery system includes a hydrogen flow meter, an argon flow meter, and a mixer. The output end of the mixer is connected to the gas inlet of the quartz furnace tube. The electric field-assisted surface modification device includes an electrochemical cell, a gradient electric field generator, and a position adjustment mechanism. The electrochemical cell has a working electrode area, a counter electrode area, a reference electrode area, and an auxiliary electrode area. The position adjustment mechanism is used to adjust the distance between the working electrode and the counter electrode. The gradient electric field generator includes a programmable power supply and an electric field control circuit. The programmable power supply is electrically connected to the working electrode and the counter electrode.In the electrochemical deposition unit, the bottom, middle, and top electromagnetic coils of the three sets of electromagnetic coils are respectively connected to the first, second, and third magnetic field power supplies, and the three output terminals of the magnetic field controller are respectively connected to the control terminals of the three magnetic field power supplies; in the cryogenic well-forming unit, the rapid freezing chamber includes an insulated chamber and a liquid nitrogen spraying system, the liquid nitrogen spraying system includes a liquid nitrogen storage tank, a delivery pipeline, and multiple evenly distributed nozzles, the nozzles being positioned above the sample holder; the directional sublimation vacuum chamber includes a cavity, a vacuum pump assembly, and a heating plate positioned at the bottom, the exhaust port of the vacuum pump assembly being connected to the cavity; the tubular vapor phase reconstruction furnace is equipped with a quartz furnace tube and heating elements, and the output terminal of the mixed gas input system is... The inlet of the quartz furnace tube is connected; in the ternary permeation barrier layer preparation device, the W precursor tank is equipped with a temperature controller, and the Mo and Cr precursor tanks are equipped with heaters; in the gas distribution system, the carrier gas pipeline and the purge gas pipeline are connected to a nitrogen source and are equipped with a mass flow controller; the three branches of the precursor delivery pipeline are respectively connected to three precursor tanks, and each of the three branches is equipped with a pneumatic valve; the three branches converge and connect to the inlet of the reaction chamber; the atomic layer deposition equipment also includes an ALD control system, the output of which is connected to the control terminals of each pneumatic valve, mass flow controller, temperature controller, and vacuum system, and the input of which is connected to a temperature sensor and a pressure sensor. The signal output terminal of the force sensor is connected; in the phase change texturing treatment device, the input terminals of the hydrogen flow meter and argon flow meter of the gas mixing and conveying system are respectively connected to the hydrogen source and argon source, and the output terminals of the two flow meters are connected to the input terminal of the gas mixer; the output terminal of the temperature program controller is connected to the heating element of the tube furnace, and the input terminal of the temperature program controller is connected to the temperature sensor set in the heating zone; in the electric field assisted surface modification device, the position adjustment mechanism includes a guide rail fixed on the electrochemical cell and a movable working electrode clamp mounted on the guide rail; the positive output terminal of the programmable power supply of the gradient electric field generator is connected to the counter electrode, and the negative output terminal is connected to the working electrode; the electric field control circuit is connected to the programmable power supply for... The system controls the superposition of DC bias voltage and AC modulation voltage output signals. The electrochemical cell is also equipped with a solution circulation system and a temperature control system. The solution circulation system includes a circulation pump and a flow regulating valve. The input and output terminals of the circulation pump are connected to the bottom and top of the electrochemical cell, respectively. The temperature control system includes a constant-temperature water bath and a heat exchanger, which is located inside the electrochemical cell. A centralized control system is also included. Multiple output terminals of the centralized control system are connected to the controller signals of the substrate pretreatment device, the gradient alloy core layer preparation device, the ternary permeation barrier layer preparation device, the phase change texturing treatment device, and the electric field-assisted surface modification device, respectively. Multiple input terminals of the centralized control system are connected to the sensor signals of each device.

[0042] Example 1 provides a specific application case of seawater hydrogen production catalyst preparation. A high-performance catalyst for seawater electrolysis hydrogen production is prepared using the complete process described in this invention. In step S1, substrate pretreatment is performed, using a nickel foam substrate with a pore density of 110 ppi, a thickness of 1.5 mm, and an area of ​​2 cm × 2 cm as the raw material. In step S11, the nickel foam substrate is sequentially immersed in acetone, anhydrous ethanol, and deionized water for organic solvent cleaning. The ultrasonic cleaning time in each solvent is 15 minutes, the ultrasonic frequency is 40 kHz, and the ultrasonic power is 200 W. During the cleaning process, acetone effectively dissolves oily contaminants on the substrate surface, anhydrous ethanol removes residual polar organic matter, and the final rinse with deionized water ensures that the substrate surface cleanliness reaches analytical purity. In step S12, the cleaned substrate is immersed in a 5% (w / w) dilute sulfuric acid solution for 30 seconds, with the solution temperature maintained at 25°C. After immersion, it is immediately removed and rinsed with deionized water until the pH value reaches 7.0. The acid etching process removed an approximately 2-micrometer-thick oxide layer from the substrate surface, exposing a fresh nickel metal surface. The surface roughness increased from Ra=0.8μm before treatment to Ra=1.2μm. In step S13, the treated substrate was placed in an argon plasma treatment chamber for plasma activation. The radio frequency power was set to 100W, the gas pressure to 0.12 Torr, the treatment time to 12 minutes, and the argon flow rate to 50 ml / min. After plasma treatment, the contact angle of the substrate surface decreased from 85 degrees before treatment to 15 degrees, indicating a significant improvement in surface activity and the acquisition of an activated substrate.

[0043] In step S2, the gradient alloy core layer is prepared. First, a precursor solution is prepared. 35.6 g of Ni(NO3)2·6H2O, 18.2 g of Fe(NO3)3·9H2O, 5.8 g of Co(NO3)2·6H2O, and 13.8 g of hexamethylenetetramine are weighed and dissolved in 1000 ml of deionized water. The pH of the solution is adjusted to 6.5 with ammonia to obtain the precursor solution, wherein the concentrations of nickel salt (0.12 M), iron salt (0.045 M), cobalt salt (0.02 M), and hexamethylenetetramine (0.10 M) are... In step S21, a gradient-distributed pulsed magnetic field is set. In the electrochemical deposition region, from the substrate surface to the depth of the solution, the magnetic field strengths of three sets of electromagnetic coils are sequentially set to 0.5 T, 1.0 T, and 1.5 T. The magnetic field pulse frequency is set to 30 Hz, and the pulse duty cycle is 50%. In step S22, a frequency of 28 kHz and a power density of 30 W / cm² are applied to the precursor solution. 2 The ultrasonic transducer is located at the bottom of the electrochemical reactor, and the ultrasonic energy is evenly distributed throughout the reaction area. In step S23, pulsed electrodeposition is performed using an activated substrate as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode, employing a square wave pulsed current with a current density of 10 mA / cm².2 The pulse frequency was 1 kHz, the duty cycle was 70%, the deposition time was 45 minutes, and the solution temperature was controlled at 45℃. During the electrodeposition process, under the synergistic effect of the gradient magnetic field and ultrasound, nickel, iron, and cobalt ions migrated directionally and deposited on the substrate surface, forming a NiFeCo ternary alloy layer with ordered atomic arrangement and uniform composition. The thickness of the deposited layer was approximately 15 micrometers, and the elemental atomic ratio Ni:Fe:Co was approximately 65:25:10.

[0044] In step S24, a freezing process is performed. The ternary alloy layer obtained by electrochemical deposition is placed in a rapid freezing device, and a liquid nitrogen spray system cools the sample to -175°C at a freezing rate of 50°C / min, maintaining this temperature for 2 hours. During freezing, the water adsorbed on the surface of the alloy layer and the liquid in the pores rapidly solidify to form ice crystals. These ice crystals grow directionally along the temperature gradient, forming a regularly arranged ice crystal template. In step S25, directional sublimation is performed, and the frozen material is transferred to a vacuum of 1×10⁻⁶. -3 In a vacuum chamber, the heating plate at the bottom of the chamber heats the material from -100°C to -10°C at a rate of 5°C / h, with the sublimation process lasting approximately 18 hours. Under vacuum conditions, ice crystals directly sublimate into water vapor and are removed by the vacuum pump, leaving a directionally arranged pore structure within the alloy layer. The pore diameter ranges from 50 nm to 500 nm, and the porosity is approximately 65%. In step S26, chemical vapor reconstruction is performed. The sublimated material is placed in a tube furnace, and a mixed gas of Ar and H2 with a volume ratio of 4:1 is introduced at a total flow rate of 100 ml / min. The furnace temperature is raised to 350°C, and the treatment lasts for 2 hours. Under a reducing atmosphere, the oxides on the alloy surface are reduced, and nanofibers grow in situ within the pores. The outer fiber diameter is 60 nm, the middle fiber diameter is 175 nm, and the inner fiber diameter is 380 nm, forming a gradient alloy core layer with a hierarchical porous nanofiber array structure and a specific surface area of ​​85 m². 2 / g.

[0045] In step S3, a ternary permeation barrier layer is prepared by sequentially depositing W, Mo, and Cr layers using atomic layer deposition (ALD). In step S31, the reaction chamber of the ALD apparatus is heated to 240°C and evacuated to a pressure of 1 × 10⁻⁶. -6In step S32, a W layer is deposited by purging with high-purity nitrogen for 30 minutes to reduce the oxygen content in the chamber to below 1 ppm and the moisture content to below 0.5 ppm. The gradient alloy core layer is placed in the reaction chamber, and the substrate temperature is controlled at 200°C. A WF6 precursor is introduced for pulse deposition. After a WF6 pulse duration of 0.5 seconds, nitrogen is purged for 10 seconds, followed by an H2O pulse duration of 0.3 seconds, and then nitrogen is purged for 15 seconds. This cycle is repeated 20 times to deposit a W layer with a thickness of approximately 4 nm. In step S33, a Mo layer is deposited while maintaining the substrate temperature at 200°C. The MoO2Cl2 precursor is switched to MoO2Cl2, which is heated to 100°C to vaporize. After a MoO2Cl2 pulse duration of 1.0 second, nitrogen is purged for 10 seconds, followed by an H2O pulse duration of 0.5 seconds, and then nitrogen is purged for 15 seconds. This cycle is repeated 15 times to deposit a Mo layer with a thickness of approximately 3 nm. In step S34, a Cr layer is deposited while maintaining the substrate temperature at 200°C. The CrO2Cl2 precursor is then switched to CrO2Cl2, which is heated to 80°C to vaporize. A CrO2Cl2 pulse is introduced for 0.8 seconds, followed by nitrogen purging for 10 seconds. Then, an H2O pulse is introduced for 0.4 seconds, followed by nitrogen purging for 15 seconds. This cycle is repeated 12 times to deposit a Cr layer with a thickness of approximately 2 nm. The total thickness of the ternary permeation barrier layer is 9 nm, with an elemental molar ratio of W:Mo:Cr of 4.0:3.0:2.0. This dense and continuous barrier layer effectively blocks the permeation of chloride ions into the alloy core layer.

[0046] Phase transformation texturing is performed in step S4. In step S41, the material obtained in S3 is placed in a quartz boat of a tube furnace, the furnace tube is sealed, and a mixed gas with a hydrogen and argon volume flow ratio of 1:4 is introduced at a total flow rate of 100 ml / min with a gas purity of 99.999%. The furnace tube is purged for 20 minutes to remove air, reducing the oxygen content to below 10 ppm. In step S42, the temperature is increased from room temperature to 300°C at a heating rate of 2.0°C / min, lasting approximately 2.3 hours, with the mixed gas continuously introduced during the heating process. In step S43, the temperature is held at 300°C for 4 hours, with temperature fluctuations controlled within ±1.5°C. During the holding process, under the action of a reducing atmosphere, the NiFe alloy undergoes a γ→α phase transformation. The volume shrinkage generated by the phase transformation forms a uniformly distributed nano-pit array texture on the catalyst surface, with a pit depth of 12 nm and a pit density of approximately 8 × 10⁻⁶. 9 pcs / cm 2 The presence of pits increases the effective active area of ​​the catalyst. In step S44, the heating system is turned off, the mixed gas flow rate is kept constant, and the material is allowed to cool naturally to room temperature in a reducing atmosphere at a cooling rate of approximately 3°C / min for approximately 1.7 hours.

[0047] In step S5, electric field-assisted surface modification is performed. In step S51, the material obtained in S4 is cut into 1.5cm × 1.5cm pieces as the working electrode, and placed in an electrochemical cell along with a platinum sheet counter electrode (3cm × 3cm), an Ag / AgCl reference electrode, and a graphite rod auxiliary electrode (15mm in diameter). 500ml of 1.0M KOH solution is added as the electrolyte, and the distance between the working electrode and the counter electrode is adjusted to 350μm. In step S52, a voltage signal is applied to the surface of the working electrode using a programmable power supply. This voltage signal is composed of a DC bias voltage of 0.3V and an AC modulation voltage, with an amplitude of ±0.20V and a frequency of 1.2kHz. The applied gradient electric field intensity is distributed from the catalyst surface to the interior, with a surface electric field intensity of approximately 1.5 × 10⁻⁶. 6 V / m, internal electric field strength is approximately 8×10 5 V / m. In step S53, the electrolyte is treated for 30 minutes under the set voltage conditions, maintaining the electrolyte temperature at 25°C and the stirring speed at 100 rpm during the process. Under the action of the gradient electric field, the OH- in the electrolyte... - Ions migrate along the direction of the electric field and form a concentration gradient inside the catalyst, OH - The ion concentration gradually increases from 0.8 M at the surface to 1.2 M at the interior; this gradient ion distribution improves the charge transport characteristics of the catalyst. In step S54, after treatment, the working electrode is removed, rinsed four times with deionized water for three minutes each time to remove residual electrolyte from the surface, then dried with high-purity nitrogen gas, and placed at 60°C and a vacuum of 1×10⁻⁶. -1 The seawater hydrogen production catalyst was obtained by storing it in a drying oven for 24 hours.

[0048] Comparative Example 1 differs from Example 1 primarily in that, during the gradient alloy core layer preparation process in step S2, a gradient-distributed pulsed magnetic field is not applied; only ultrasonic-assisted electrochemical deposition is applied. The other steps are the same as in Example 1. Specifically, in step S21, no gradient magnetic field is set, and no magnetic field is applied to the electrochemical deposition region. In step S22, a frequency of 28 kHz and a power density of 30 W / cm² are still applied in the precursor solution. 2 The ultrasonic waves. In step S23, the same pulse electrodeposition parameters are used, with a current density of 10 mA / cm². 2The pulse frequency was 1 kHz, the duty cycle was 70%, the deposition time was 45 minutes, and the solution temperature was controlled at 45°C. Due to the lack of magnetic field orientation, the atomic arrangement of the deposited NiFeCo ternary alloy layer was less ordered, the grain orientation was random, and there were more grain boundary defects. The alloy layer thickness was approximately 14 micrometers, and the elemental atomic ratio Ni:Fe:Co was approximately 64:26:10, which was basically the same as in Example 1, but the density of the alloy layer was slightly lower, and a small number of micropores were present. The subsequent freezing treatment, directional sublimation, chemical vapor phase reconstruction, ternary permeation barrier layer preparation, phase change texturing treatment, and electric field-assisted surface modification steps were all exactly the same as in Example 1, using the same process parameters.

[0049] Comparative Example 2 differs from Example 1 primarily in that, in step S3, during the preparation of the ternary permeation barrier layer, only a single Cr layer is deposited, without depositing W and Mo layers. Other steps are identical to Example 1. Specifically, after equipment pretreatment in step S31, the Cr layer deposition step is performed directly. During Cr layer deposition, the substrate temperature is controlled at 200°C. A CrO2Cl2 precursor is used, heated to 80°C to vaporize it. A CrO2Cl2 pulse is introduced for 0.8 seconds, followed by nitrogen purging for 10 seconds, then an H2O pulse for 0.4 seconds, followed by nitrogen purging for 15 seconds. To obtain a total thickness similar to Example 1, the number of cycles is increased to 45, resulting in a single Cr barrier layer with a thickness of approximately 9 nm. Because only a single Cr barrier layer is used, although the thickness is similar, its density and barrier performance are inferior to the ternary composite barrier layer, and the chloride ion permeability is higher. Subsequent phase change texturing and electric field-assisted surface modification steps are identical to those in Example 1.

[0050] Comparative Example 3 differs from Example 1 primarily in that, in step S4, during the phase transformation texturing process, programmed heating and phase transformation heat preservation are not performed; instead, atmospheric treatment is conducted directly at room temperature. Other steps are the same as in Example 1. Specifically, in step S41, after placing the material obtained in S3 into a quartz boat in a tube furnace, no heating is performed. Instead, a mixed gas with a hydrogen and argon volume flow rate ratio of 1:4, a total flow rate of 100 ml / min, and a gas purity of 99.999%, is introduced at room temperature (25°C) for 4 hours. Due to the low temperature, the phase transformation temperature of the NiFe alloy is not reached, the alloy does not undergo a γ→α phase transformation, and a nano-pit array texture does not form on the catalyst surface. The surface remains relatively smooth, and the effective active area is relatively small. The subsequent electric field-assisted surface modification steps are exactly the same as in Example 1.

[0051] Comparative Example 4 differs from Example 1 primarily in that, during the electric field-assisted surface modification process in step S5, only a fixed DC voltage is applied, without superimposed AC modulation voltage, thus preventing the formation of a spatially gradient electric field. The other steps are the same as in Example 1. Specifically, in step S52, a fixed DC bias voltage of 0.3V is applied to the working electrode surface using a programmable power supply, without superimposed AC modulation voltage. In step S53, the treatment is carried out for 30 minutes under a fixed DC voltage, maintaining the electrolyte temperature at 25°C and the stirring speed at 100 rpm during the process.

[0052] Comparative Example 5: This comparative example uses the traditional impregnation-calcination method to prepare a seawater hydrogen production catalyst, without employing the multi-stage synergistic processing technology described in this invention. The specific process is as follows: A nickel foam substrate (pore density 110 ppi, thickness 1.5 mm, area 2 cm × 2 cm) is cleaned with anhydrous ethanol and deionized water, then immersed in a mixed solution containing 0.12 M Ni(NO3)2·6H2O, 0.045 M Fe(NO3)3·9H2O, and 0.02 M Co(NO3)2·6H2O for 30 minutes. After immersion, it is dried in an oven at 80 °C for 2 hours, then calcined in air at a heating rate of 5 °C / min to 350 °C, held at that temperature for 3 hours, and naturally cooled to room temperature to obtain a catalyst supported on NiFeCo oxides.

[0053] Comparative experiments were designed and conducted to test the electrochemical performance indicators of each catalyst sample.

[0054] Experiment 1: Oxygen Evolution Reaction Overpotential Test; The oxygen evolution reaction overpotential of the catalyst was tested using linear sweep voltammetry (LSV). The experimental setup employed a CHI660E electrochemical workstation with a three-electrode system, using the catalyst under test as the working electrode, and a platinum sheet (4 cm²) as the electrode. 2 The electrode used was the counter electrode, and Ag / AgCl (saturated KCl) was the reference electrode. The electrolyte was a mixed solution of 1 wt% KOH and 3.5 wt% NaCl, simulating the actual seawater electrolysis environment. The test temperature was 25℃, controlled by a constant temperature water bath. Before the test, high-purity argon gas was purged into the electrolyte for 30 minutes to remove dissolved oxygen. The linear sweep voltammetry test had a scan rate of 5 mV / s and a scan potential range of 1.0 V to 1.8 V (vs RHE). The current-potential curve was recorded during the scan. Based on the curve, the current density was determined to be 10 mA / cm². 2 The potential value corresponding to the time step is used. The difference between this potential value and the theoretical oxygen evolution potential (1.23V vs RHE) is the overpotential of the oxygen evolution reaction. Each sample is tested three times, and the average value is taken as the final result.

[0055] Experiment 2: Tafel slope tests were performed on each catalyst sample to evaluate its electrocatalytic reaction kinetics. The experimental setup and electrolyte were the same as in Experiment 1. Based on the current-potential curves obtained from linear sweep voltammetry, the curve segment with overpotential ranging from 50mV to 200mV was selected. A Tafel plot was drawn with overpotential η as the abscissa and the logarithm of current density log(j) as the ordinate. A linear fit was performed on the curve according to the Tafel equation η = a + b·log(j), and the slope of the fitted line was the Tafel slope b. The magnitude of the Tafel slope reflects the kinetics of the electrocatalytic reaction; the smaller the slope, the faster the reaction kinetics and the better the catalytic performance. Each sample was tested three times, and the average value was taken as the final result.

[0056] Experiment 3: Long-term stability test; Constant potential electrolysis tests were performed on each catalyst sample to evaluate its long-term stability in a seawater environment. The experimental setup and electrolyte were the same as in Experiment 1. The working electrode potential was kept constant at 1.6V (vsRHE), corresponding to an initial current density of approximately 50 mA / cm². 2 Approximately 1000 hours of continuous electrolysis were performed, with current density values ​​recorded every 50 hours, and a curve showing the change in current density over time was plotted. The electrolyte temperature was maintained at 25°C during the test, and evaporated water was periodically replenished to maintain a constant electrolyte volume. Stability was expressed as the current density retention rate, calculated using the formula: Current density retention rate = (Current density after 1000 hours / Initial current density) × 100%. A higher current density retention rate indicates better catalyst stability and stronger resistance to chloride ion corrosion. Each sample underwent two parallel tests, and the average value was taken as the final result.

[0057] Experiment 4: Electrochemical Active Surface Area (ECSA) Measurement; The electrochemical active surface area (ECSA) of each catalyst sample was measured to assess the number of active sites. The experimental setup used a CHI660E electrochemical workstation with a three-electrode system and 1 MkOH solution as the electrolyte. Cyclic voltammetry was used within the non-Radar range (0.90 V to 1.00 V vs RHE) at scan rates of 10, 20, 40, 60, 80, and 100 mV / s. Cyclic voltammetry curves were recorded at different scan rates. The average anodic and cathodic current densities were read at 0.95 V as the capacitance current density corresponding to that scan rate. A graph was plotted with scan rate on the x-axis and capacitance current density on the y-axis. Linear fitting was performed on the data points, and the slope of the fitted line is the double-layer capacitance Cdl. Electrochemical active surface area (ECSA) = Cdl / Cs, where Cs is the specific capacitance per unit true surface area. For metal oxide catalysts in alkaline solution, Cs is taken as 0.040 mF / cm². 2 Each sample was tested three times, and the average value was taken as the final result.

[0058] Experiment 5: Charge Transfer Resistance Test; The experimental setup used a CHI660E electrochemical workstation with a three-electrode system. The electrolyte was a mixed solution of 1 MkOH and 3.5 wt% NaCl. The test potential was set at the onset potential of the oxygen evolution reaction (approximately 1.50 V vs RHE), with an AC amplitude of 5 mV and a frequency range of 100 kHz to 0.01 Hz. Ten data points were collected at each frequency. The impedance data obtained were represented by a Nyquist plot. The arcs in the high-frequency region corresponded to the solution resistance and double-layer capacitance, while the arcs in the mid-frequency region corresponded to the charge transfer resistance and electrochemical reaction capacitance. An equivalent circuit model was used to fit the impedance data. The equivalent circuit is Rs, where Rs is the solution resistance, Cdl is the double-layer capacitance, Rct is the charge transfer resistance, Cp is the electrochemical reaction capacitance, and W is the Warburg diffusion impedance. The parameters of each component were obtained through fitting. The charge transfer resistance Rct reflects the ease of electron transport within the catalyst; the smaller the Rct, the faster the electron transport and the better the catalytic performance. Each sample was tested three times, and the average value was taken as the final result.

[0059] The experimental results are as follows: Figures 1-6 As shown, through Figures 1-6 It can be seen that the seawater hydrogen production catalyst prepared in Example 1 is significantly superior to the comparative examples in key performance indicators such as oxygen evolution reaction overpotential, Tafel slope, long-term stability, electrochemical active surface area, and charge transfer resistance, as detailed below: from Figure 1 It can be seen that the oxygen evolution reaction overpotential of Example 1 is 258 mV, significantly lower than all comparative examples. Comparative Example 1 (without gradient magnetic field) has an overpotential of 285 mV, Comparative Example 2 (single-layer barrier layer) has an overpotential of 312 mV, Comparative Example 3 (without phase change texture) has an overpotential of 298 mV, and Comparative Example 4 (without gradient electric field) has an overpotential as high as 365 mV, while Comparative Example 5, using the conventional impregnation-calcination method, has an overpotential as high as 365 mV. This indicates that Example 1 has the best catalytic activity, requiring the lowest driving voltage and achieving the highest energy conversion efficiency at the same current density. The gradient magnetic field-induced electrochemical deposition technology results in an ordered atomic arrangement of the NiFeCo ternary alloy layer, reducing grain boundary defects and lowering scattering losses during electron transport. The ternary permeation barrier layer is deposited layer by layer in the W-Mo-Cr sequence, forming a gradient protective system that effectively prevents chloride ions from penetrating into the active layer, maintaining the integrity of the active sites. Phase change texturing creates an array of nano-pits on the surface, increasing edge and step sites. The coordination unsaturation of these sites results in a lower reaction energy barrier. OH groups formed by electric field-assisted surface modification... - An ion concentration gradient layer maintains a low OH concentration on the catalyst surface. -The concentration of O2 is favorable for O2 precipitation and desorption, reducing the product inhibition effect and thus lowering the overpotential. From an electrochemical perspective, the reduction in overpotential stems from the decrease in activation energy and the increase in charge transfer rate. This invention achieves optimization in both aspects through multi-scale structural regulation and synergy.

[0060] from Figure 2 It can be seen that the Tafel slope of Example 1 is 64 mV / decade, the lowest among all samples. The comparative examples are, in descending order: Comparative Example 1: 78 mV / decade; Comparative Example 4: 72 mV / decade; Comparative Example 3: 85 mV / decade; Comparative Example 2: 92 mV / decade; and Comparative Example 5: 118 mV / decade. The Tafel slope is a key parameter for evaluating the kinetics of electrocatalytic reactions. A smaller slope means a steeper increase in current density with increasing overpotential, indicating faster reaction kinetics and a more significant performance advantage of the catalyst in the high current density region. The Lorentz force generated by the gradient magnetic field on metal ions during deposition promotes the ordered arrangement of atoms along specific crystal planes, forming a crystal structure with exposed low-index crystal planes. These crystal planes have higher intrinsic catalytic activity. The hierarchical porous nanofiber array structure was formed through cryo-directional sublimation and vapor-phase reconstruction techniques. The outer 60 nm fine fibers provide a large number of highly active sites, the middle 175 nm medium-sized fibers act as electron transport channels to shorten the charge transport distance, and the inner 380 nm coarse fibers provide structural support. These three elements synergistically reduce the charge transfer resistance. From a reaction kinetics perspective, the Tafel slope is closely related to the reaction mechanism and rate-determining step. A lower Tafel slope indicates that the oxygen evolution reaction follows a more favorable four-electron transfer pathway, which was achieved by controlling the electronic structure and surface chemical state of the catalyst.

[0061] from Figure 3It can be seen that Example 1 maintained a current density retention rate of 94.5% after 1000 hours of constant potential electrolysis, exceeding the target value of 93% and significantly outperforming all comparative examples. Comparative Example 4 maintained 90.3%, Comparative Example 1 88.2%, Comparative Example 3 85.6%, Comparative Example 2 only 76.8%, and Comparative Example 5 had the worst stability, with a retention rate of only 62.4%. Long-term stability is a decisive indicator for evaluating the practical potential of a catalyst, and maintaining high current density output capability in the harsh corrosive environment of seawater electrolysis is particularly crucial. This demonstrates the scientific validity and effectiveness of the W-Mo-Cr ternary permeation barrier layer design of this invention. Comparative Example 2 used a single-layer Cr barrier layer. Although Cr can form a passivation film in an alkaline environment, the single-layer structure lacks density and has microscopic defects and pinholes. Chloride ions can penetrate into the active layer through these channels and undergo a displacement reaction with the NiFeCo alloy, leading to the dissolution and loss of the active metal. The ternary composite barrier layer used in Example 1, with the W layer as the first barrier having extremely high chemical stability, and the Mo layer reacting with Cl... - Stable coordination bonds are formed for further interception, and the Cr layer forms a dense passivation film on the outermost layer to prevent electrolyte penetration. The three layers synergistically construct a gradient and multi-layered protection system. From the perspective of corrosion electrochemistry, the barrier layer's mechanism of action includes reducing ion migration rate, increasing ion penetration barrier, and reducing corrosion current density. The lattice mismatch and chemical potential gradient formed at the interface of the ternary composite structure further enhance the barrier effect. Although the surface nano-pits formed by phase change texturing increase surface roughness, due to the complete protection of the barrier layer, the risk of corrosion is not increased. On the contrary, the specific activity of the catalyst is improved by increasing the density of active sites, thus delaying the performance degradation caused by the loss of active sites.

[0062] from Figure 4 It can be seen that the electrochemically active surface area of ​​Example 1 reaches 1070 cm². 2 This is significantly higher than all comparative examples. Comparative example 4 is 960 cm. 2 Comparative Example 1 is 890cm 2 Comparative Example 3 is 845cm 2 Comparative Example 2 is 780cm 2 The smallest of the five comparative examples is only 563cm. 2Electrochemical active surface area is a direct indicator of the number of active sites on a catalyst. A larger active surface area means more reactive centers, enabling more catalytic reactions to occur simultaneously and improving overall catalytic efficiency. The hierarchical porous nanofiber array structure creates numerous directional channels within the dense alloy layer through cryogenic directional sublimation technology. The chemical vapor deposition process grows nanofibers in situ within these channels, forming a three-tiered gradient distribution: an outer layer of 40-90 nm, a middle layer of 130-220 nm, and an inner layer of 280-550 nm. This hierarchical structure significantly increases the specific surface area of ​​the catalyst, reaching 85 m² / g. Phase transformation texturing utilizes the gamma-to-alpha phase transformation that occurs in NiFe alloys at 280-320℃. The accompanying volume change generates a nano-pit array with a depth of 4-25 nm on the surface, achieving a pit density of 8 × 10⁻⁶. 9 Each square centimeter of these pits provides additional step and twisting sites at their edges and bottoms. Comparative Example 3, due to the omission of the phase transition texturing step, maintains a relatively smooth surface. Although it still possesses a nanofiber structure, the lack of nano-pits significantly reduces the active surface area. From a surface chemistry perspective, nanoscale surface roughening not only increases the geometric surface area but, more importantly, generates a large number of coordinated unsaturated atoms with dangling bonds and localized electronic states. This results in stronger adsorption capacity for reaction intermediates, lowers the reaction activation energy, and enhances catalytic activity.

[0063] from Figure 5 It can be seen that the charge transfer resistance of Example 1 is only 2.8 Ω·cm. 2 The value was the lowest among all samples. Comparative Example 4 had a value of 3.6 Ω·cm. 2 Comparative Example 1 has a strength of 4.5 Ω·cm. 2 Comparative Example 3 has a strength of 5.1 Ω·cm. 2 Comparative Example 2 has a strength of 6.2 Ω·cm. 2 Comparative example 5 has a strength as high as 9.8 Ω·cm. 2 Charge transfer resistance is a key parameter for evaluating the efficiency of electron transport within the catalyst and at the electrode-electrolyte interface. Lower resistance indicates faster electron transport, less ohmic polarization loss, and allows the catalyst to maintain high efficiency at higher current densities. Gradient magnetic field-assisted electrochemical deposition arranges the atoms of the NiFeCo ternary alloy in an ordered manner, reducing grain boundary scattering and lowering intrinsic resistance. The doping of Fe and Co modulates the electronic structure of Ni; the hybridization of Fe's 3d orbitals with Ni's 3d orbitals enhances electron delocalization, and the introduction of Co optimizes the density of states near the Fermi level, improving electronic conductivity. The hierarchical porous nanofiber array, with its medium and coarse fibers, forms a three-dimensional electron transport network, allowing electrons to quickly reach surface active sites from the current collector via multiple paths, shortening transport distances and reducing contact resistance. Electric field-assisted surface modification generates OH groups within the catalyst.- An ion concentration gradient layer, gradually increasing from 0.8 mol / L at the surface to 1.2 mol / L at the interior, creates a chemical potential difference that promotes ion diffusion. Simultaneously, the gradient electric field enhances electron-ion coupling transport and reduces interfacial charge transfer resistance. Comparative Example 4, with only a fixed DC voltage applied and no gradient electric field formed, exhibits a more uniform ion distribution but lacks the driving force of chemical potential, resulting in a slightly higher charge transfer resistance than Example 1. From a solid-state physics perspective, the charge transfer process involves multiple steps, including electron tunneling, interfacial double-layer charging and discharging, and Faraday reactions. This invention systematically reduces energy losses in each step by optimizing the crystal structure, electronic density of states, and ion concentration distribution.

[0064] comprehensive Figures 1 to 5 Experimental results demonstrate that this invention successfully prepared a multi-level composite seawater hydrogen production catalyst with a hierarchical porous nanofiber array structure, a dense ternary permeation barrier layer, a nanotextured surface, and a gradient ion distribution layer through the organic combination of gradient magnetic field-induced electrochemical deposition, cryogenic directional sublimation pore-forming, chemical vapor phase reconstruction, ternary composite barrier layer atomic layer deposition, phase change texturing heat treatment, and gradient electric field-assisted surface modification. This catalyst achieves comprehensive breakthroughs in five key performance dimensions: oxygen evolution reaction overpotential, reaction kinetics, long-term stability, active surface area, and charge transport efficiency, providing a reliable catalytic material solution for the industrial application of direct seawater electrolysis hydrogen production technology.

[0065] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a seawater hydrogen production catalyst, characterized in that, Includes the following steps: S1. Substrate pretreatment: The nickel foam substrate is sequentially cleaned with organic solvent, acid etched and plasma activated to obtain an activated substrate; S2. Gradient alloy core layer preparation: Using an activated substrate as the working electrode, electrochemical deposition is performed in a precursor solution containing nickel salt, iron salt and cobalt salt by applying a gradient-distributed pulsed magnetic field and ultrasound to obtain a NiFeCo ternary alloy layer. The deposited ternary alloy layer was subjected to freeze treatment, directional sublimation and chemical vapor reconstruction to form a gradient alloy core layer with a hierarchical porous nanofiber array structure. S3. Preparation of ternary permeation barrier layer: Using atomic layer deposition technology, W-Mo-Cr ternary permeation barrier layer is formed by depositing W layer, Mo layer and Cr layer sequentially on the surface of gradient alloy core layer. S4. Phase transformation texturing treatment: The material obtained in S3 is subjected to programmed temperature rise heat treatment in a mixed atmosphere of hydrogen and argon to form a nano-textured structure on the catalyst surface by utilizing alloy phase transformation. S5. Electric field-assisted surface modification: The material obtained in S4 is placed in an electrochemical cell, and a spatially gradient electric field is applied in an alkaline electrolyte to form an ion concentration gradient layer, thus obtaining a seawater hydrogen production catalyst.

2. The method for preparing a seawater hydrogen production catalyst according to claim 1, characterized in that, S1 includes the following steps: S11. Organic solvent cleaning: Place the nickel foam substrate in acetone, anhydrous ethanol and deionized water in sequence, and ultrasonically clean it for 10-20 minutes in each solvent to remove surface oil and organic residues. S12, acid etching: Immerse the substrate cleaned by S11 in a 3-7% dilute sulfuric acid solution for 20-40 seconds, then take it out and rinse it with deionized water until the pH is neutral to remove the surface oxide layer and inorganic impurities, and obtain a clean substrate. S13, Plasma Activation: The substrate treated in S12 is placed in an argon plasma treatment chamber and treated for 8-15 minutes under the conditions of radio frequency power of 80-120W and gas pressure of 0.08-0.15 Torr to improve the surface activity of the substrate and obtain an activated substrate.

3. The method for preparing a seawater hydrogen production catalyst according to claim 1, characterized in that, The precursor solution of S2 is prepared by dissolving Ni(NO3)2·6H2O (0.10-0.15M), Fe(NO3)3·9H2O (0.03-0.06M), Co(NO3)2·6H2O (0.01-0.03M), and hexamethylenetetramine (0.08-0.12M) in deionized water, and adjusting the pH of the solution to 6.0-7.0 with ammonia water to obtain the precursor solution.

4. The method for preparing a seawater hydrogen production catalyst according to claim 1, characterized in that, The steps of applying a gradient-distributed pulsed magnetic field and ultrasound for electrochemical deposition in S2 include: S21. Magnetic field setting: Magnetic field generating devices are set at different spatial locations in the electrochemical deposition area. The magnetic field strength is set sequentially from the substrate surface to the depth of the solution to 0.3-0.7T, 0.8-1.2T and 1.3-1.7T to form a gradient magnetic field. The magnetic field pulse frequency is set to 8-60Hz. S22. Ultrasonic application: Apply ultrasound at a frequency of 25-32 kHz and a power density of 20-45 W / cm² to the precursor solution. 2 Ultrasonic waves enhance the mass transfer of ions in the solution. S23, Pulse Electrodeposition: Under the conditions of simultaneous action of S21 and S22, electrochemical deposition is performed using an activated substrate as the working electrode, employing a square wave pulsed current with a current density of 4-18 mA / cm². 2 With a duty cycle of 60-80%, a deposition time of 35-55 minutes, and a solution temperature controlled at 40-50℃, a NiFeCo ternary alloy layer with atomically ordered arrangement was deposited on the substrate surface under the synergistic effect of magnetic field orientation and ultrasonic enhanced mass transfer.

5. The method for preparing a seawater hydrogen production catalyst according to claim 1, characterized in that, The steps in S2 for freezing, directional sublimation, and chemical vapor reconstruction of the deposited ternary alloy layer include: S24. Freezing treatment: The ternary alloy layer obtained by electrochemical deposition is placed in a rapid freezing device and cooled to -150°C to -200°C at a freezing rate of 40-60°C / min, and held for 1.5-2.5 hours to form an oriented ice crystal template inside the alloy layer. S25, Directional Sublimation: Transferring the material frozen in S24 to a vacuum of 5×10⁻⁶. -4 -2×10 -3 In a vacuum chamber of Pa, the temperature is increased from -100℃ to -10℃ at a heating rate of 3-7℃ / h. Ice crystals sublimate directionally under vacuum conditions, forming a directionally arranged channel structure in the alloy layer. S26. Chemical vapor phase reconstruction: The sublimated material from S25 is placed in a tube furnace, and a mixed gas with a volume ratio of Ar to H2 of 3:1 to 5:1 is introduced at a total flow rate of 80-120 ml / min. The material is treated at 320-380℃ for 1.5-2.5 hours to grow nanofibers in situ within the pores, forming a hierarchical porous nanofiber array structure with an outer fiber diameter of 40-90 nm, a middle fiber diameter of 130-220 nm, and an inner fiber diameter of 280-550 nm, thus completing the preparation of the gradient alloy core layer.

6. The method for preparing a seawater hydrogen production catalyst according to claim 1, characterized in that, S3 includes the following steps: S31. Equipment Pretreatment: Heat the reaction chamber of the atomic layer deposition equipment to 220-260℃ and evacuate to a pressure below 1×10⁻⁶. -6 Torr, purge with nitrogen for 25-35 minutes to remove impurities and moisture from the chamber; S32, W layer deposition: The gradient alloy core layer obtained by S2 is placed in the reaction chamber, the substrate temperature is controlled at 190-210℃, and WF6 precursor is introduced for pulse deposition. After the WF6 pulse time is 0.3-0.7 seconds, nitrogen gas is purged for 8-12 seconds, then H2O pulse is introduced for 0.2-0.5 seconds, followed by nitrogen gas purging for 12-18 seconds. The cycle is repeated 15-25 times to deposit the W layer on the surface of the gradient alloy core layer. S33, Mo layer deposition: After S32 is completed, keep the substrate temperature constant and switch to MoO2Cl2 precursor. Heat MoO2Cl2 to 90-110℃ to vaporize it. Pulse MoO2Cl2 for 0.8-1.3 seconds, then purge with nitrogen for 8-12 seconds. Then pulse H2O for 0.4-0.6 seconds, then purge with nitrogen for 12-18 seconds. Repeat the cycle 10-20 times to deposit a Mo layer on the W layer surface. S34, Cr layer deposition: After S33, keep the substrate temperature constant and switch to CrO2Cl2 precursor. Heat CrO2Cl2 to 70-90℃ to vaporize it. Pulse CrO2Cl2 for 0.6-1.0 seconds, then purge with nitrogen for 8-12 seconds. Then pulse H2O for 0.3-0.5 seconds, then purge with nitrogen for 12-18 seconds. Repeat the cycle 8-15 times to deposit a Cr layer on the Mo layer surface, forming a ternary permeation barrier layer with a total thickness of 8-60 nm and an elemental molar ratio of W:Mo:Cr of 3.5:2.8:1.8 to 4.5:3.5:2.

5.

7. The method for preparing a seawater hydrogen production catalyst according to claim 1, characterized in that, S4 includes the following steps: S41. Loading and Atmosphere Preparation: Place the material obtained in S3 into the quartz boat of the tube furnace, seal the furnace tube, and introduce a mixture of hydrogen and argon gas. The volume flow ratio of hydrogen to argon is 1:3 to 1:5, the total flow rate is 80-120 ml / min, and the gas purity is ≥99.99%. Purge for 15-25 minutes to remove air from the furnace tube. S42. Programmed heating: The temperature is increased from room temperature to 280-320℃ at a heating rate of 1.5-3.0℃ / min. During the heating process, the mixed gas is continuously introduced to ensure that the material temperature rises uniformly. S43. Phase transformation heat preservation: Keep at 280-320℃ for 3-5 hours, with temperature fluctuation controlled within ±2℃. In a reducing atmosphere, the NiFe alloy undergoes a γ→α phase transformation. The volume change generated by the phase transformation forms a nano-pit array texture with a depth of 4-25nm on the catalyst surface. S44. Cooling: Turn off the heating system, keep the mixed gas flow rate constant, and allow the material to cool naturally to room temperature in a reducing atmosphere. The cooling rate is controlled at ≤5℃ / min to complete the phase change texturing treatment.

8. The method for preparing a seawater hydrogen production catalyst according to claim 1, characterized in that, S5 includes the following steps: S51. Electrochemical cell assembly: The material obtained in S4 is used as the working electrode, and together with the platinum sheet counter electrode, Ag / AgCl reference electrode, and graphite rod auxiliary electrode, it is put into the electrochemical cell. A KOH solution with a concentration of 0.8-1.2M is added as the electrolyte, and the distance between the working electrode and the counter electrode is adjusted to 200-500μm. S52. Gradient electric field application: A voltage signal is applied to the surface of the working electrode through a programmable power supply. This voltage signal is composed of a DC bias voltage and an AC modulation voltage. The DC bias voltage is 0.2-0.4V, and the AC modulation voltage amplitude is ±0.15-0.25V with a frequency of 0.8-1.5kHz. By adjusting the electrode spacing and voltage, a spatially gradient electric field is formed inside the catalyst. S53. Electric Field Treatment: Treat for 25-35 minutes under the voltage conditions set in S52. During the treatment, maintain the electrolyte temperature at 20-30℃ and the stirring speed at 80-120 rpm. Under the action of the gradient electric field, OH- ions are formed inside the catalyst. - A gradient distribution of ion concentration that gradually increases from the surface to the interior; S54. Cleaning and Drying: After treatment, remove the working electrode and rinse it with deionized water 3-5 times, 2-5 minutes each time, to remove residual electrolyte on the surface. Then dry it with nitrogen gas and place it at a temperature of 50-70℃ and a vacuum degree of 5×10⁻⁶. -2 -2×10 -1 The seawater hydrogen production catalyst was obtained by storing it in a drying oven.

9. A seawater hydrogen production catalyst preparation system for implementing the method according to any one of claims 1-8, characterized in that, include: The substrate pretreatment device includes an ultrasonic cleaning unit, an acid etching unit, and a plasma activation unit connected in sequence. The ultrasonic cleaning unit is equipped with a cleaning tank containing organic solvent and deionized water and an ultrasonic generator. The acid etching unit is equipped with an etching pool containing dilute sulfuric acid solution. The plasma activation unit includes a plasma treatment chamber, a radio frequency power supply, and a vacuum pump. A gradient alloy core layer preparation apparatus includes an electrochemical deposition unit and a cryogenic pore-forming unit. The electrochemical deposition unit includes an electrochemical reactor, three sets of electromagnetic coils arranged in layers along the height direction, a magnetic field controller, an ultrasonic transducer, and a temperature control system. The electrochemical reactor is equipped with a working electrode support, a counter electrode, and a reference electrode. The three sets of electromagnetic coils correspond to the bottom, middle, and top regions of the electrochemical reactor, respectively, and are used to generate a gradient magnetic field. The magnetic field controller is electrically connected to the three sets of electromagnetic coils and is used to independently control the magnetic field strength and pulse frequency of each set of electromagnetic coils. The ultrasonic transducer is installed at the bottom of the electrochemical reactor and is used to emit ultrasonic waves into the solution. The cryogenic pore-forming unit includes a rapid freezing chamber, a directional sublimation vacuum chamber, and a tubular vapor phase reconstruction furnace. The rapid freezing chamber is equipped with a liquid nitrogen circulation system, the directional sublimation vacuum chamber is equipped with a vacuum pump and a heating system, and the tubular vapor phase reconstruction furnace is equipped with a mixed gas input system. The ternary permeation barrier layer preparation apparatus is an atomic layer deposition device, comprising a reaction chamber, a W precursor tank, a Mo precursor tank, and a Cr precursor tank arranged sequentially, a gas distribution system, and a vacuum system. A substrate heating stage is provided in the reaction chamber. The gas distribution system includes a carrier gas pipeline, a purge gas pipeline, and a precursor delivery pipeline. The precursor delivery pipeline is connected to the three precursor tanks and the reaction chamber respectively. A phase change texturing treatment apparatus includes a tubular furnace, a gas mixing and conveying system, and a temperature program controller. The tubular furnace is equipped with a heating zone and a quartz furnace tube. The gas mixing and conveying system includes a hydrogen flow meter, an argon flow meter, and a gas mixer. The output end of the gas mixer is connected to the gas inlet of the quartz furnace tube. An electric field-assisted surface modification device includes an electrochemical cell, a gradient electric field generator, and a position adjustment mechanism. The electrochemical cell is provided with a working electrode region, a counter electrode region, a reference electrode region, and an auxiliary electrode region. The position adjustment mechanism is used to adjust the distance between the working electrode and the counter electrode. The gradient electric field generator includes a programmable power supply and an electric field control circuit. The programmable power supply is electrically connected to the working electrode and the counter electrode.

10. The seawater hydrogen production catalyst preparation system according to claim 9, characterized in that, In the electrochemical deposition unit, the bottom, middle, and top electromagnetic coils of the three sets of electromagnetic coils are respectively connected to the first, second, and third magnetic field power supplies, and the three output terminals of the magnetic field controller are respectively connected to the control terminals of the three magnetic field power supplies; in the cryogenic well-forming unit, the rapid freezing chamber includes an insulated chamber and a liquid nitrogen spraying system, the liquid nitrogen spraying system includes a liquid nitrogen storage tank, a delivery pipeline, and multiple evenly distributed nozzles, the nozzles being positioned above the sample holder; the directional sublimation vacuum chamber includes a cavity, a vacuum pump assembly, and a heating plate positioned at the bottom, the exhaust port of the vacuum pump assembly being connected to the cavity; The tubular vapor phase reconstruction furnace is equipped with a quartz furnace tube and heating elements. The output end of the mixed gas input system is connected to the gas inlet of the quartz furnace tube. In the ternary permeation barrier layer preparation device, the W precursor tank is equipped with a temperature controller, and the Mo and Cr precursor tanks are equipped with heaters. In the gas distribution system, the carrier gas pipeline and the purge gas pipeline are connected to a nitrogen source and are equipped with a mass flow controller. The three branches of the precursor delivery pipeline are respectively connected to three precursor tanks, and each of the three branches is equipped with a pneumatic valve. The three branches converge and are connected to the gas inlet of the reaction chamber. The atomic layer deposition equipment also includes an ALD control system. The output end of the ALD control system is connected to the control ends of each pneumatic valve, mass flow controller, temperature controller, and vacuum system. The input end of the ALD control system is connected to the signal output ends of the temperature sensor and pressure sensor. In the phase change texturing treatment device, the input terminals of the hydrogen flow meter and argon flow meter of the gas mixing and conveying system are connected to the hydrogen source and argon source, respectively, and the output terminals of the two flow meters are connected to the input terminal of the gas mixer; the output terminal of the temperature program controller is connected to the heating element of the tube furnace, and the input terminal of the temperature program controller is connected to the temperature sensor installed in the heating zone; in the electric field assisted surface modification device, the position adjustment mechanism includes a guide rail fixed on the electrochemical cell and a movable working electrode clamp installed on the guide rail; the positive output terminal of the programmable power supply of the gradient electric field generator is connected to the counter electrode, and the negative output terminal is connected to the working electrode; the electric field control circuit is connected to the programmable power supply and is used to control the superposition signal of the output DC bias voltage and AC modulation voltage; the electrochemical cell is also equipped with a solution circulation system and a temperature control system; the solution circulation system includes a circulation pump and a flow regulating valve; the input terminal and output terminal of the circulation pump are connected to the bottom and top of the electrochemical cell, respectively; the temperature control system includes a constant temperature water bath and a heat exchanger; the heat exchanger is installed inside the electrochemical cell; It also includes a centralized control system, the multiple output terminals of which are respectively connected to the controller signals of the substrate pretreatment device, the gradient alloy core layer preparation device, the ternary permeation barrier layer preparation device, the phase change texturing treatment device, and the electric field assisted surface modification device, and the multiple input terminals of the centralized control system are respectively connected to the sensor signals of each device.

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