Preparation method and application of phosphate coating modified nickel-iron-based electrolytic seawater hydrogen production catalyst

Abstract

This invention discloses a method for preparing and applying a phosphate-coated nickel-iron-based catalyst for seawater electrolysis to produce hydrogen, belonging to the field of nanocatalysis and clean energy conversion. The invention uses nickel foam as a substrate, immersing it in a nickel-iron mixed solution at room temperature to grow a layered nickel-iron double hydroxide in situ on the support surface. After cleaning and drying, it is sequentially activated using potassium hydroxide and sodium hexametaphosphate solutions, combined with cyclic voltammetric electrochemical activation, to obtain a phosphate-coated nickel-iron-based catalyst. This catalyst is used as the anode in a flowing electrolyzer, paired with a nickel phosphide cathode, to complete the electrocatalytic hydrogen production reaction using alkaline seawater as the electrolyte. This preparation process is mild, simple to operate, uses inexpensive and readily available raw materials, is environmentally friendly, requires no complex equipment, and is suitable for large-scale production. The modified catalyst, in synergy with the flowing electrolyzer system, can efficiently achieve alkaline seawater electrolysis, showing broad application prospects in green hydrogen production and clean energy conversion, and providing technical support for achieving dual-carbon goals.

Description

Technical Field

[0001] This invention belongs to the field of water electrolysis technology, specifically relating to a method for preparing and applying a nickel-iron-based catalyst for hydrogen production by seawater electrolysis modified with a phosphate coating. Background Technology

[0002] With the continued advancement of the "dual carbon" goals, the transition to clean energy, represented by hydrogen energy, has become one of the key paths to achieving low-carbon development, and water electrolysis technology is receiving increasing attention and investment. The water electrolysis process consists of two half-reactions: the oxygen evolution reaction at the anode and the hydrogen evolution reaction at the cathode. The reaction kinetics of both play a decisive role in the overall performance of the electrolyzer. However, limited by the inherently slow kinetics of the reactions themselves, traditional water electrolysis systems often require high overpotentials to drive the reactions, which directly restricts their large-scale application in industrial settings.

[0003] Currently, high-performance water electrolysis catalysts in industry are still mainly based on precious metals. Although these materials exhibit excellent intrinsic activity, their crustal reserves are scarce and their prices are high. Furthermore, they suffer from insufficient stability during long-term operation, which significantly increases the construction and operation costs of water electrolysis systems and limits their large-scale application.

[0004] Meanwhile, most current mainstream water electrolysis technologies rely on freshwater as the electrolyte feedstock. In future large-scale hydrogen production scenarios, the consumption and allocation of freshwater resources will become a new bottleneck. In contrast, seawater accounts for the vast majority of the Earth's total water volume, representing a nearly limitless potential electrolyte resource. Directly utilizing seawater for electrolysis is considered an important direction for solving water resource constraints. However, seawater electrolysis technology still faces many challenges: on the one hand, seawater has a complex composition, especially with high concentrations of chloride ions that easily compete for energy at the anode, causing corrosion and side reactions, severely affecting catalyst life and electrolysis efficiency; on the other hand, in alkaline seawater environments, the activity and stability of catalysts generally decrease significantly, requiring higher operating voltages in actual electrolyzers to achieve the target current density, resulting in a significant increase in energy consumption.

[0005] To address the problems existing in the prior art, this invention proposes a method for preparing and applying a phosphate-coated nickel-iron-based catalyst for hydrogen production by seawater electrolysis. Summary of the Invention

[0006] To address the shortcomings and deficiencies of existing technologies, this invention provides a method for preparing and applying a phosphate-coated nickel-iron-based electrolytic seawater hydrogen production catalyst. This invention aims to solve the problems of existing oxygen evolution catalysts' excessive dependence on freshwater, high overpotential, poor stability, and insensitivity to Cl-. -The technical problem of corrosion. The preparation method provided by this invention is simple, low in cost, and suitable for industrial mass production. A flow electrolytic cell is assembled, and the prepared electrocatalyst is used as the anode to carry out electrocatalytic reactions in alkaline seawater, exhibiting high catalytic efficiency and stability.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing and applying a phosphate-coated nickel-iron-based catalyst for electrolytic seawater hydrogen production, comprising the following steps:

[0008] S1. Pre-treat the nickel foam substrate;

[0009] S2. Take the dried nickel foam carrier and immerse it in a precursor mixture solution prepared by ferric chloride hexahydrate and nickel chloride hexahydrate. After immersion for a period of time, take it out, remove the excess solution on the surface with filter paper, and air dry it naturally at room temperature to obtain the supported NiFe-LDH electrode precursor.

[0010] S3. Prepare a potassium hydroxide activation solution containing sodium hexametaphosphate; first, perform cyclic voltammetric pre-activation on the NiFe-LDH electrode obtained in step S2 in the potassium hydroxide solution, and then transfer it to the above-mentioned potassium hydroxide solution containing sodium hexametaphosphate for a second cyclic voltammetric activation to obtain the nickel-iron-based catalyst modified with the phosphate coating, named NiFe-P6O. 18 6- ;

[0011] S4. The nickel-iron-based catalyst with phosphate coating obtained in step S3 is used to electrolyze alkaline seawater in a flow cell. The nickel-iron-based catalyst with phosphate coating is used as the anode of the flow cell, the nickel phosphide catalyst is used as the cathode of the flow cell, and the alkaline seawater solution is used as the electrolyte. The electrocatalytic reaction is carried out at 60°C. The cathode undergoes a hydrogen evolution reaction to produce hydrogen gas, and the anode undergoes an oxygen evolution reaction to produce oxygen gas.

[0012] Based on the above technical solution, the specific operation of the pretreatment of the nickel foam substrate in step S1 is as follows: First, the nickel foam substrate is immersed in 10 mL of hydrochloric acid solution and ultrasonically treated to remove the oxide film on its surface; then, it is ultrasonically cleaned with deionized water to remove residual hydrochloric acid, and then ultrasonically cleaned with 10 mL of acetone to remove organic impurities on the surface; finally, it is ultrasonically rinsed with deionized water and anhydrous ethanol respectively, and the cleaned nickel foam is placed in a vacuum drying oven to dry, thus completing the pretreatment of the nickel foam substrate.

[0013] Based on the above technical solution, the thickness of the nickel foam is 1.6 mm and the area is 2*3 cm. 2 The concentration of the hydrochloric acid mentioned is 3 mol / L. -1The ultrasonic treatment time for hydrochloric acid is 10-15 min, for deionized water it is 5-10 min, for acetone it is 10-15 min, and for ethanol it is 5-10 min.

[0014] Based on the above technical solution, the concentration of ferric chloride hexahydrate in step S2 is 0.5 mol / L. -1 The concentration of nickel chloride hexahydrate is 0.5 mol L. -1 The nickel foam was immersed in the solution for 120 seconds.

[0015] Based on the above technical solution, the potassium hydroxide solution in step S3 is 1 mol / L. -1 The sodium hexametaphosphate solution is 0.05 mol / L. -1 .

[0016] Based on the above technical solution, the range of the two cyclic voltammetry in step S3 is -0.2 to -1 V vs. RHE, and the number of cycles is 50.

[0017] Based on the above technical solution, the area of ​​both the anode and cathode catalysts in S4 is 2 cm². 2 The concentration of potassium hydroxide in the alkaline seawater electrolyte is 1 mol / L. -1 The applied voltage range is 1~2 V.

[0018] Secondly, the present invention provides a nickel-iron-based catalyst modified with a phosphate coating prepared by the above preparation method.

[0019] Thirdly, the present invention provides a method for preparing a nickel-iron-based electrolytic seawater hydrogen production catalyst modified with a phosphate coating according to the above preparation method, and its application.

[0020] Compared with related technologies, the beneficial effects of the present invention are as follows:

[0021] (1) This invention uses a process of room temperature soaking combined with cyclic voltammetric activation to prepare a hexametaphosphate-modified nickel-iron layered double hydroxide catalyst NiFe-P6O 18 6- This catalyst, based on nickel foam, achieves high-efficiency electrocatalytic performance through in-situ growth and surface modification. Its unique layered structure and surface modification can significantly increase the exposure of active sites and greatly reduce the overpotential of the electrocatalytic oxygen evolution reaction, providing a high-efficiency and low-cost anode electrocatalyst for the direct electrolysis of alkaline seawater.

[0022] (2) The NiFe-P6O prepared by this invention 18 6-The catalyst effectively modulates the electronic structure of the nickel-iron active center through hexametaphosphate modification, optimizing the adsorption energy of the catalyst surface for reaction intermediates. At the same time, the surface modification layer can significantly suppress the competitive adsorption and side reactions of chloride ions in alkaline seawater, giving the catalyst excellent chlorine removal effect. This not only improves the reaction selectivity of the catalytic system, but also enhances its corrosion resistance and long-term operational stability in the complex environment of alkaline seawater. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only one embodiment of the present invention. For those skilled in the art, other embodiments can be derived from the provided drawings without creative effort.

[0024] Figure 1 A flowchart illustrating the method for electrolyzing alkaline seawater using a phosphate-coated nickel-iron-based catalyst provided by this invention.

[0025] Figure 2 The NiFe-P6O prepared in Example 1 of this invention 18 6- Scanning electron microscope images;

[0026] Figure 3 These are the FT-IR spectra of Example 1 and Comparative Example 1 before electrolysis of alkaline seawater in this invention;

[0027] Figure 4 These are the Raman spectra of Example 1 and Comparative Example 1 of the present invention before electrolysis of alkaline seawater;

[0028] Figure 5 Impedance test diagrams for the three-electrode system in Embodiment 1 and Comparative Examples 1-5 of the present invention;

[0029] Figure 6 These are LSV test diagrams for the three-electrode systems of Embodiment 1 and Comparative Examples 1-5 of the present invention;

[0030] Figure 7 These are the Raman spectra of Example 1 and Comparative Example 1 after electrolysis of alkaline seawater.

[0031] Figure 8 In Embodiment 1 of the present invention, 1 A cm in a flow cell -1 Continuous electrolysis diagram at current density;

[0032] Figure 9 These are flow cell LSV test diagrams for Embodiment 1 and Comparative Example 1 of the present invention in alkaline seawater.

[0033] Figure 10 These are the XPS spectra of alkaline seawater after electrolysis in Example 1 and Comparative Example 1 of the present invention; Detailed Implementation

[0034] The present invention will be further described below with reference to the accompanying drawings and examples:

[0035] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0036] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0037] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0038] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0039] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0040] A method for preparing and applying a phosphate-coated nickel-iron-based catalyst for hydrogen production by seawater electrolysis, characterized in that the preparation method includes the following steps:

[0041] S1. Pre-treat the nickel foam substrate;

[0042] S2. Immerse the dried nickel foam in a 30 ml mixed solution of ferric chloride hexahydrate and nickel chloride hexahydrate. After a short time, remove it, use filter paper to absorb the excess solution on the surface, and air dry it at room temperature to obtain NiFe-LDH grown on the nickel foam.

[0043] S3. Prepare a potassium hydroxide activation solution containing sodium hexametaphosphate; first, perform cyclic voltammetric pre-activation on the NiFe-LDH electrode obtained in step S2 in the potassium hydroxide solution, and then transfer it to the above-mentioned potassium hydroxide solution containing sodium hexametaphosphate for a second cyclic voltammetric activation to obtain the nickel-iron-based catalyst modified with the phosphate coating, named NiFe-P6O. 18 6- .

[0044] S4. The nickel-iron-based catalyst with phosphate coating obtained in step S3 is used to electrolyze alkaline seawater in a flow cell. The nickel-iron-based catalyst with phosphate coating is used as the anode of the flow cell, the nickel phosphide catalyst is used as the cathode of the flow cell, and the alkaline seawater solution is used as the electrolyte. The electrocatalytic reaction is carried out at 60°C. The cathode undergoes a hydrogen evolution reaction to produce hydrogen gas, and the anode undergoes an oxygen evolution reaction to produce oxygen gas.

[0045] Based on the above technical solution, the specific operation of the pretreatment of the nickel foam substrate in step S1 is as follows: first, the nickel foam substrate is soaked in hydrochloric acid and ultrasonically treated to remove the oxide film on its surface; then, the nickel foam substrate is ultrasonically treated in deionized water to remove residual hydrochloric acid, then ultrasonically treated with ethanol, and then vacuum dried to complete the pretreatment of the nickel foam substrate.

[0046] Based on the above technical solution, the nickel foam has a thickness of 1.6 mm and an area of ​​2*3 cm. 2 The concentration of the hydrochloric acid is 3 mol / L. -1 The concentration of the hydrochloric acid is 3 mol / L. -1 The ultrasonic treatment time for hydrochloric acid is 10-15 min, the ultrasonic treatment time for deionized water is 10-15 min, and the ultrasonic treatment time for ethanol is 10-15 min.

[0047] Based on the above technical solution, the concentration of ferric chloride hexahydrate in step S2 is 0.5 mol / L. -1 The concentration of nickel chloride hexahydrate is 0.5 mol L. -1 The nickel foam was immersed in the solution for 120 seconds.

[0048] Based on the above technical solution, the potassium hydroxide solution in step S3 is 1 mol / L. -1 The sodium hexametaphosphate solution is 0.05 mol / L. -1 .

[0049] Based on the above technical solution, the range of the two cyclic voltammetry cycles in step S3 is -0.2 to -1 V vs. the number of RHE cycles is 50.

[0050] Based on the above technical solution, the area of ​​both the anode and cathode catalysts in S4 is 2 cm². 2 The concentration of potassium hydroxide in the alkaline seawater electrolyte is 1 mol / L. -1 The applied voltage range is 1~2 V.

[0051] Secondly, the present invention provides a nickel-iron-based catalyst modified with a phosphate coating prepared by the above preparation method.

[0052] Thirdly, the present invention provides a method for preparing a nickel-iron-based electrolytic seawater hydrogen production catalyst modified with a phosphate coating according to the above preparation method, and its application.

[0053] Example 1

[0054] S1. Pretreatment of nickel foam substrate: Select a substrate with a thickness of 1.6 mm and an effective area of ​​2*3 cm. 2 Nickel foam (NF) was used as the substrate material, and it was first placed in a solution with a concentration of 3 mol / L. -1 The surface oxide layer was removed by ultrasonic cleaning in hydrochloric acid solution for 15 min; then it was ultrasonically rinsed with ultrapure water for 10 min to completely remove residual acid; then it was ultrasonically treated with anhydrous ethanol for 10 min to remove surface organic impurities; finally, the cleaned nickel foam was placed in a vacuum drying oven at 60℃ and vacuum dried for 6 h to obtain a clean nickel foam substrate.

[0055] S2. Immerse the dried nickel foam in 30 ml of 0.5 mol / L solution. -1 Ferric chloride hexahydrate and 0.5 mol L -1 After 120 seconds in a mixed solution of nickel chloride hexahydrate, the sample was removed, excess solution on the surface was absorbed with filter paper, and the sample was allowed to air dry at room temperature to obtain NiFe-LDH grown on nickel foam.

[0056] S3. Prepare a potassium hydroxide activation solution containing sodium hexametaphosphate; first, perform cyclic voltammetric pre-activation on the NiFe-LDH electrode obtained in step S2 in the potassium hydroxide solution, and then transfer it to the above-mentioned potassium hydroxide solution containing sodium hexametaphosphate for a second cyclic voltammetric activation to obtain the nickel-iron-based catalyst modified with the phosphate coating, named NiFe-P6O. 18 6- .

[0057] S4. The nickel-iron-based catalyst with phosphate coating obtained in step S3 is used to electrolyze alkaline seawater in a flow cell. The nickel-iron-based catalyst with phosphate coating is used as the anode of the flow cell, the nickel phosphide catalyst is used as the cathode of the flow cell, and the alkaline seawater solution is used as the electrolyte. The electrocatalytic reaction is carried out at 60°C. The cathode undergoes a hydrogen evolution reaction to produce hydrogen gas, and the anode undergoes an oxygen evolution reaction to produce oxygen gas.

[0058] Comparative Example 1

[0059] The method in this embodiment is the same as that in embodiment 1, with the same parts omitted. The difference from embodiment 1 is that in this embodiment, step S3 is to add NiFe-LDH to the potassium hydroxide solution for cyclic voltammetry pre-activation, and the catalyst is named NiFe-LDH.

[0060] Comparative Example 2

[0061] The difference between this embodiment and Comparative Example 1 is that in step S3, a potassium hydroxide activation solution containing trisodium phosphate is prepared and subjected to a second cyclic voltammetric activation. The catalyst is named NiFe-PO4. 3- .

[0062] Comparative Example 3

[0063] The difference between this embodiment and Comparative Example 1 is that in step S3, a potassium hydroxide activation solution containing sodium pyrophosphate is prepared and subjected to a second cyclic voltammetric activation. The catalyst is named NiFe-P2O7. 4- .

[0064] Comparative Example 4

[0065] The difference between this embodiment and Comparative Example 1 is that in step S3, a potassium hydroxide activation solution containing sodium trimetaphosphate is prepared and subjected to a second cyclic voltammetric activation. The catalyst is named NiFe-P3O9. 3- .

[0066] Comparative Example 5

[0067] The difference between this embodiment and Comparative Example 1 is that in step S3, a potassium hydroxide activation solution containing sodium tripolyphosphate is prepared and subjected to a second cyclic voltammetric activation. The catalyst is named NiFe-P3O. 10 5- .

[0068] Figure 1 This is a flowchart of the method for producing hydrogen from alkaline seawater using a phosphate-coated nickel-iron-based catalyst provided by the present invention. This apparatus uses the NiFe-P6O catalyst prepared in Example 1. 18 6- The catalyst is used as the anode, and nickel phosphide is used as the cathode of the flow cell. The effective reaction area of ​​both the anode and cathode catalysts is 2 cm², and the anode and cathode chambers are separated by an anion exchange membrane. The electrolytes for both the anode and cathode of the flow cell are alkaline seawater.

[0069] Figure 2 The NiFe-P6O prepared in Example 1 of this invention 18 6-The scanning electron microscope images show that it exhibits a uniform nanosheet morphology with more lateral dimensions and abundant metal active sites, which is conducive to the binding of water molecules and improves electrocatalytic performance.

[0070] Figure 3 NiFe-P6O 18 6- FT-IR spectra compared to NiFe-LDH before electrolysis of alkaline seawater. Compared to NiFe-LDH, NiFe-P6O... 18 6- In 1000~1200 cm -1 The presence of characteristic absorption peaks for P=O and OPO bonds at the site indicates that hexametaphosphate has been successfully modified and the chemical environment of the active center has been regulated.

[0071] Figure 4 These are the Raman spectra of Example 1 and Comparative Example 1 before electrolysis of alkaline seawater. The results show that, compared with NiFe-LDH, NiFe-P6O 18 6- The sample was at 1064 cm. -1 A new characteristic peak appeared, which is attributed to the stretching vibration of the PO bond. These results indicate that hexametaphosphate modification did not disrupt the original layered structure of NiFe-LDH, and the introduction of PO bonds further improved the structural stability of the material, proving that the NiFe-P6O prepared in this invention... 18 6- The catalyst exhibits excellent structural durability in alkaline seawater electrolysis environments.

[0072] Figure 5 These are impedance test graphs of alkaline seawater in a three-electrode system for Embodiment 1 and Comparative Examples 1-5 of the present invention. Figure 5 It can be seen that the impedance of Example 1 is smaller, which means that its interfacial electron transfer rate is faster and more conducive to the reaction.

[0073] Figure 6 The figures show the linear sweep voltammetry curves of the catalysts obtained in Example 1 and Comparative Examples 1-5 of this invention in alkaline seawater under a three-electrode system. As can be seen from the figures, compared to the unmodified and other phosphate-modified control samples, the NiFe-P6O prepared in Example 1 of this invention... 18 6- The catalyst exhibits a lower overpotential at the same current density and can achieve a higher current density at the same applied potential, indicating that hexametaphosphate modification can significantly improve the electrocatalytic activity of the catalyst, reduce the reaction kinetic barrier, and endow the material with better catalytic performance.

[0074] Figure 7The images show the Raman spectra of NiFe-P6O after electrolysis of alkaline seawater in Example 1 and Comparative Example 1 of this invention. The results indicate that after the reaction, NiFe-P6O... 18 6- The characteristic peaks of Ni-O and PO are still clearly retained, while the characteristic peak intensity of NiFe-LDH is significantly reduced, indicating that hexametaphosphate modification significantly improves the structural stability of the catalyst.

[0075] Figure 8 In Embodiment 1 of the present invention, 1 A cm in a flow cell -1 The continuous electrolysis plot at the specified current density showed that it could be continuously electrolyzed in alkaline seawater for 500 h without significant degradation, proving that the NiFe-P6O prepared in Example 1... 18 6- Stability and corrosion resistance as a catalyst for the electrolysis of alkaline seawater.

[0076] Figure 9 The figures show the overall alkaline seawater decomposition performance curves when Example 1 and Comparative Example 1 are assembled into an electrolytic cell. As can be seen from the figure, NiFe-P6O... 18 6- The cell voltage of the system at the same current density is significantly lower than that of the NiFe-LDH system, indicating that the catalyst modified with hexametaphosphate can effectively reduce the energy consumption of the overall alkaline seawater decomposition and improve the electrolysis efficiency.

[0077] Figure 10 These are the XPS spectra of alkaline seawater after electrolysis in Example 1 and Comparative Example 1 of this invention. The results show that the chlorine content on the surface of the NiFe-LDH sample is as high as 8.28%, while that of the NiFe-P6O sample is much higher. 18 6- The chlorine content of the sample was only 1.13%, significantly lower than that of the comparative sample. This indicates that the hexametaphosphate modification layer effectively inhibited the adsorption of chloride ions on the catalyst surface, reduced competitive side reactions, and demonstrated its excellent resistance to chlorine corrosion and selectivity for the oxygen evolution reaction.

[0078] The present invention has been described above by way of example, but the present invention is not limited to the specific embodiments described above. Any modifications or variations made based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing a nickel-iron-based electrolytic seawater hydrogen production catalyst modified with a phosphate coating, characterized in that, The preparation method includes the following steps: S1. Pre-treat the nickel foam substrate; S2. Take the dried nickel foam carrier and immerse it in a precursor mixture solution prepared from ferric chloride hexahydrate and nickel chloride hexahydrate. After immersion for a period of time, take it out, remove the excess solution from the surface with filter paper, and air dry it naturally at room temperature to obtain the supported NiFe-LDH electrode precursor. S3. Prepare a potassium hydroxide activation solution containing sodium hexametaphosphate; first, perform cyclic voltammetric pre-activation on the NiFe-LDH electrode obtained in step S2 in the potassium hydroxide solution, and then transfer it to the above-mentioned potassium hydroxide solution containing sodium hexametaphosphate for a second cyclic voltammetric activation to obtain the nickel-iron-based catalyst modified with the phosphate coating, named NiFe-P6O. 18 6- . S4. The nickel-iron-based catalyst with phosphate coating obtained in step S3 is used to electrolyze alkaline seawater in a flow cell. The nickel-iron-based catalyst with phosphate coating is used as the anode of the flow cell, the nickel phosphide catalyst is used as the cathode of the flow cell, and the alkaline seawater solution is used as the electrolyte. The electrocatalytic reaction is carried out at 60°C. The cathode undergoes a hydrogen evolution reaction to produce hydrogen gas, and the anode undergoes an oxygen evolution reaction to produce oxygen gas.

2. The method for preparing a phosphate-coated nickel-iron based catalyst for hydrogen production by seawater electrolysis according to claim 1, characterized in that, The specific pretreatment operation of the nickel foam substrate in step S1 is as follows: First, the nickel foam substrate is immersed in 10 mL of hydrochloric acid solution and ultrasonically treated to remove the oxide film on its surface; then, it is ultrasonically cleaned with deionized water to remove residual hydrochloric acid, and then ultrasonically cleaned with 10 mL of acetone to remove organic impurities on the surface; finally, it is ultrasonically rinsed with deionized water and anhydrous ethanol respectively, and the cleaned nickel foam is placed in a vacuum drying oven to dry, thus completing the pretreatment of the nickel foam substrate.

3. The method for preparing a phosphate-coated nickel-iron based catalyst for hydrogen production by seawater electrolysis according to claim 2, characterized in that, The nickel foam has a thickness of 1.6 mm and an area of ​​2*3 cm. 2 The concentration of the hydrochloric acid mentioned is 3 mol / L. -1 The ultrasonic treatment time for hydrochloric acid is 10-15 min, for deionized water it is 5-10 min, for acetone it is 10-15 min, and for ethanol it is 5-10 min.

4. The method for preparing a phosphate-coated nickel-iron based catalyst for hydrogen production by seawater electrolysis according to claim 1, characterized in that, The concentration of ferric chloride hexahydrate mentioned in step S2 is 0.5 mol / L. -1 The concentration of nickel chloride hexahydrate is 0.5 mol L. -1 The nickel foam was immersed in the solution for 120 seconds.

5. The method for preparing a phosphate-coated nickel-iron based catalyst for hydrogen production by seawater electrolysis according to claim 1, characterized in that, The potassium hydroxide solution mentioned in step S3 is 1 mol / L. -1 The sodium hexametaphosphate solution is 0.05 mol / L. -1 .

6. The method for preparing a phosphate-coated nickel-iron based catalyst for hydrogen production by seawater electrolysis according to claim 1, characterized in that, The range of the two cyclic voltammetry measurements in step S3 is -0.2 to -1 V vs. RHE, and the number of cycles is 50.

7. The method for preparing a phosphate-coated nickel-iron based catalyst for hydrogen production by seawater electrolysis according to claim 1, characterized in that, The area of ​​both the anode and cathode catalysts mentioned in step S4 is 2 cm². 2 The concentration of potassium hydroxide in the alkaline seawater electrolyte is 1 mol / L. -1 The applied voltage range is 1~2 V.

8. A nickel-iron-based catalyst modified with a phosphate coating, prepared by the preparation method according to any one of claims 1-7.

9. The preparation method and application of the phosphate-coated nickel-iron-based electrolytic seawater hydrogen production catalyst prepared by the preparation method according to any one of claims 1-7.

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