Boron-doped composite catalyst, preparation method and application thereof, oxygen evolution electrode and electrolytic cell

Abstract

The invention relates to the field of anion membrane water electrolysis hydrogen production, and discloses a boron-doped composite catalyst and a preparation method and application thereof, an oxygen evolution electrode and an electrolytic bath, the composite catalyst contains Fe, Ni, B and Co, and the molar ratio of Fe to Ni to B to Co is (0.1-1): (0.2-3): (1-3): 1. The composite catalyst has a two-dimensional layered structure, and boron is doped in a ternary metal compound catalyst of nickel, iron and cobalt, so that the valence state of Ni in an active center is improved, the alternating current resistance is reduced, and the oxidation activity and stability of the composite catalyst are improved.

Description

Technical Field

[0001] This invention relates to the field of hydrogen production by anion exchange membrane electrolysis of water, specifically to boron-doped composite catalysts, their preparation methods and applications, oxygen evolution electrodes, and electrolyzers. Background Technology

[0002] Hydrogen energy, hailed as the "ultimate energy of the 21st century," is a recognized clean energy source. With finite reserves and increasing consumption of non-renewable fossil fuels such as oil, natural gas, and coal, the development and application of hydrogen energy has become a strategic choice. Currently, water electrolysis for hydrogen production is considered one of the most environmentally friendly and promising methods due to its advantages, including requiring water as a raw material and producing high-purity, pollution-free hydrogen.

[0003] Electrolysis of water plays a crucial role in the development of renewable energy technologies. In the hydrogen production reaction, the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) occur at the anode and cathode, respectively. The OER reaction involves a four-electron transfer process, and compared to HER, the reaction pathway is more complex, often resulting in a higher overpotential for water splitting, severely impacting electrolysis efficiency. Electrocatalysts used in the OER reaction must possess both activity and stability at high oxidation potentials. The limited resources of noble metal-based catalysts, such as Ru and Ir, hinder their large-scale application. Ru, in particular, is relatively unstable and tends to dissolve at its oxidation potential, leading to material consumption. Currently, commercially available oxygen evolution catalysts are noble metal Ir-based catalysts, which are expensive and have limited reserves. Therefore, developing efficient and stable non-noble metal oxygen evolution electrode materials is beneficial for the development of water electrolysis technology.

[0004] Among numerous transition metal-based electrocatalysts, LDH-type catalysts represent a class of OER electrocatalysts with potential applications. In LDH-type OER electrocatalysts, metal ions of different valence states form a layered framework. The tunability of the intercalation layers and composition improves the performance of oxygen-catalyst reactions, but its catalytic activity still needs further enhancement. To address this, various modification methods have emerged for LDH-type catalysts, including adjusting the concentration ratio of metal ions, modifying the composition, adding NH4F to adjust the morphology, and adjusting the anion during intercalation. In this work, a boron-doped NiFeCo layered ternary hydroxide (LTH) OER catalyst was synthesized via a hydrothermal method. The introduction of boron increased the valence state of Ni, improved charge conductivity, and promoted the enhancement of catalyst activity. Summary of the Invention

[0005] The purpose of this invention is to further improve the activity of NiFe-based oxygen evolution catalysts and provide a boron-doped composite catalyst, its preparation method and application, and an oxygen evolution electrode. This composite catalyst has excellent charge conductivity and oxygen evolution activity.

[0006] To achieve the above objectives, the first aspect of the present invention provides a boron-doped composite catalyst containing Fe, Ni, B and Co, wherein the molar ratio of Fe, Ni, B and Co is 0.1-1:0.2-3:1-3:1.

[0007] A second aspect of this invention provides a method for preparing a boron-doped composite catalyst, the method comprising: (1) In the presence of a solvent, mix an iron source, a cobalt source, a boron source, an alkaline substance, and a mineralizing agent; (2) The mixture obtained in step (1) is mixed with a nickel-containing metal substrate for hydrothermal crystallization; wherein the amounts of iron source, nickel-containing metal substrate, boron source and cobalt source are such that the molar ratio of Fe, Ni, B and Co in the composite catalyst is 0.1-1:0.2-3:1-3:1.

[0008] A third aspect of the present invention provides a boron-doped composite catalyst prepared by the preparation method described in the second aspect.

[0009] A fourth aspect of the present invention provides an oxygen evolution electrode comprising the boron-doped composite catalyst described in the first or third aspect.

[0010] The fifth aspect of the present invention provides an electrolytic cell, wherein the anode of the electrolytic cell is the oxygen evolution electrode described in the fourth aspect.

[0011] The sixth aspect of the present invention provides the application of the boron-doped composite catalyst described in the first or third aspect in the electrolysis of water to produce hydrogen.

[0012] Through the above technical solution, the present invention can achieve at least the following beneficial effects: (1) The present invention improves the valence state of the active center Ni by doping boron into a ternary metal composite catalyst of nickel, iron and cobalt, thereby reducing AC impedance.

[0013] (2) The present invention improves the activity and stability of the composite catalyst by doping boron into the ternary metal composite catalyst of nickel, iron and cobalt, thereby increasing the valence state of the active center Ni.

[0014] (3) The boron-doped composite catalyst of the present invention reduces the oxidation potential.

[0015] (4) In a preferred embodiment of the present invention, the Ni in the boron-doped composite catalyst is controlled. 3+ The molar ratio of Ni element is used to control the catalyst's activity and stability. Attached Figure Description

[0016] Figure 1 This is a TEM image of the boron-doped composite catalyst prepared in Example 1; Figure 2 This is a Fourier transform diagram of the boron-doped composite catalyst prepared in Example 1; Figure 3 These are the XPS spectra of Ni element in the boron-doped composite catalyst and the undoped catalyst prepared in Example 1; Figure 4 This is a comparison of the LSV polarization curves of the boron-doped composite catalyst and the undoped boron catalyst prepared in Example 1. Figure 5 The images show the AC impedance spectra of the boron-doped composite catalyst prepared in Example 1, the undoped boron catalyst, and the nickel foam on a metal substrate. Detailed Implementation

[0017] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0018] The first aspect of the present invention provides a boron-doped composite catalyst, the composite catalyst containing Fe, Ni, B and Co, wherein the molar ratio of Fe, Ni, B and Co is 0.1-1:0.2-3:1-3:1.

[0019] This invention increases surface defect sites and modulates the electronic structure of the Ni component by doping the catalyst with boron and a ternary metal complex of nickel, iron and cobalt, thereby improving the oxygen evolution catalytic activity of the catalyst.

[0020] In this invention, preferably, the molar ratio of Fe, Ni, B and Co in the composite catalyst is 0.2-0.5:0.4-2:1.2-2.5:1.

[0021] In this invention, preferably, the composite catalyst is used at a current density of 100 mA / cm². 2 The oxygen evolution overpotential can be 180-280mV (e.g., 180mA / cm). 2 182mA / cm 2 184mA / cm 2 186mA / cm 2 188mA / cm 2 190mA / cm 2 192mA / cm 2 194mA / cm 2 196mA / cm 2198mA / cm 2 200mA / cm 2 210mA / cm 2 220mA / cm 2 230mA / cm 2 240mA / cm 2 250mA / cm 2 253mA / cm 2 255mA / cm 2 258mA / cm 2 260mA / cm 2 263mA / cm 2 265mA / cm 2 268mA / cm 2 270mA / cm 2 272mA / cm 2 275mA / cm 2 277mA / cm 2 280mA / cm 2 (The range formed by any two values ​​in the range and the values ​​within that range).

[0022] In this invention, preferably, after the composite catalyst is doped with element B, Ni 3+ The molar percentage of Ni is 50-80%, more preferably 65-75% (for example, it can be any two values ​​formed by 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, and values ​​within that range).

[0023] In this invention, preferably, the surface of the boron-doped composite catalyst has a large number of defects. The existence of defects can be seen by observing the Fourier transform diagram. The boron-doped composite catalyst has obvious lattice dislocations, indicating that its surface has a large number of defect structures.

[0024] In this invention, the AC impedance of the composite catalyst is affected by conditions such as the testing method. According to the testing method and conditions in this application, the AC impedance of the composite catalyst is 40-70mΩ, preferably 45-58mΩ (for example, it can be any two values ​​from 45mΩ, 46mΩ, 47mΩ, 48mΩ, 49mΩ, 50mΩ, 51mΩ, 52mΩ, 53mΩ, 54mΩ, 55mΩ, 56mΩ, 57mΩ, 58mΩ, or any value within that range).

[0025] In this invention, the charge conduction resistance of the composite catalyst is significantly reduced after doping with B.

[0026] In this invention, preferably, the composite catalyst has a two-dimensional layered structure with an average thickness of 20-60 nm, more preferably 25-55 nm (for example, it can be any two values ​​from 25 nm, 26 nm, 27 nm, 28 nm, 29 nm, 30 nm, 31 nm, 32 nm, 33 nm, 35 nm, 38 nm, 40 nm, 42 nm, 44 nm, 46 nm, 48 nm, 50 nm, 52 nm, 54 nm, 55 nm, forming a range or values ​​within that range).

[0027] A second aspect of this invention provides a method for preparing a boron-doped composite catalyst, the method comprising: (1) In the presence of a solvent, mix an iron source, a cobalt source, a boron source, an alkaline substance, and a mineralizing agent; (2) The mixture obtained in step (1) is mixed with a nickel-containing metal substrate for hydrothermal crystallization; wherein the amounts of iron source, nickel-containing metal substrate, boron source and cobalt source are such that the molar ratio of Fe, Ni, B and Co in the composite catalyst is 0.1-1:0.2-3:1-3:1.

[0028] In this invention, preferably, the amounts of iron source, nickel-containing metal substrate, boron source and cobalt source are such that the molar ratio of Fe, Ni, B and Co in the composite catalyst is 0.2-0.5:0.4-2:1.2-2.5:1.

[0029] It is understood that the statement that "the amount of iron source, nickel-containing metal substrate, boron source and cobalt source is such that the molar ratio of Fe, Ni, B and Co in the composite catalyst is 0.1-1:0.2-3:1-3:1" does not limit the amount of iron source, nickel-containing metal substrate, boron source and cobalt source to be the same as the molar ratio of Fe, Ni, B and Co in the final composite catalyst, but is only used to reflect the molar ratio of Fe, Ni, B and Co in the composite catalyst.

[0030] In this invention, preferably, the molar ratio of the iron source (calculated as iron), the boron source (calculated as boron), and the cobalt source (calculated as cobalt) is 0.2-2: 5-20:1, more preferably 0.5-1: 6-18:1.

[0031] In this invention, preferably, the amount of the nickel-containing metal substrate is sufficient to meet the molar content of Ni in the composite catalyst.

[0032] In this invention, preferably, the iron source can be a substance commonly used in the art to provide iron for composite catalysts, such as at least one of ferric nitrate, ferric sulfate, and ferric chloride.

[0033] In this invention, preferably, the cobalt source can be a substance commonly used in the art to provide cobalt element for composite catalysts, for example, it can be at least one of cobalt nitrate, cobalt sulfate and cobalt chloride.

[0034] In this invention, preferably, the boron source can be a substance commonly used in the art to provide boron for composite catalysts, for example, it can be at least one of boric acid, cobalt borate and nickel borate.

[0035] In this invention, preferably, the nickel-containing metal substrate is a material commonly used in the art to provide nickel for composite catalysts, for example, it can be at least one of nickel substrate, nickel-iron substrate and nickel felt.

[0036] In this invention, preferably, the molar amount of the alkaline substance is 1-5 times the total molar amount of cobalt and iron, more preferably 1.5-3 times (for example, it can be any two multiples formed by 1.5 times, 1.6 times, 1.7 times, 1.8 times, 1.9 times, 2 times, 2.1 times, 2.2 times, 2.3 times, 2.4 times, 2.5 times, 2.6 times, 2.7 times, 2.8 times, 2.9 times, and 3 times, or multiples within that range).

[0037] In this invention, preferably, the molar amount of the mineralizer is 3-10 times the total molar amount of cobalt and iron (for example, it can be any two multiples formed by 3 times, 3.5 times, 4 times, 4.5 times, 5 times, 5.5 times, 6 times, 6.5 times, 7 times, 7.5 times, 8 times, 8.5 times, 9 times, 9.5 times, 10 times, or multiples within that range).

[0038] In this invention, preferably, the alkaline substance can be a substance commonly used in the art to provide alkalinity in the preparation of composite catalysts, for example, it can be urea and / or sodium hydroxide.

[0039] In this invention, preferably, the mineralizing agent can be a commonly used mineralizing agent in the art, for example, ammonium fluoride.

[0040] In this invention, preferably, the conditions for hydrothermal crystallization include: the hydrothermal crystallization temperature can be 90-180℃, more preferably 110-150℃ (for example, it can be any two values ​​formed by 110℃, 115℃, 120℃, 125℃, 130℃, 135℃, 140℃, 145℃, 150℃, or any value within that range); the hydrothermal crystallization time can be 8-20h, more preferably 10-15h (for example, it can be any two values ​​formed by 10h, 10.5h, 11h, 11.5h, 12h, 12.5h, 13h, 13.5h, 14h, 14.5h, 15h, or any value within that range).

[0041] In this invention, preferably, in step (1), the solvent is not particularly limited and can be a commonly used solvent in the art for dissolving and mixing iron, boron and cobalt sources, such as water. The amount of solvent is not particularly limited, as long as it can fully mix the iron, boron and cobalt sources.

[0042] In a preferred embodiment of the present invention, the method further includes: in step (1), the mixed liquid is subjected to ultrasonic treatment, and there is no particular limitation on the ultrasonic conditions, for example, it can be 10-60 min.

[0043] In a preferred embodiment of the present invention, the method further includes: in step (2), after hydrothermal crystallization is completed, the surface of the obtained product is rinsed with deionized water.

[0044] A third aspect of the present invention provides a boron-doped composite catalyst prepared by the preparation method described in the second aspect.

[0045] A fourth aspect of the present invention provides an oxygen evolution electrode comprising the boron-doped composite catalyst described in the first or third aspect.

[0046] In this invention, the oxygen evolution electrode can be prepared using methods commonly used in the art, and the substances added during the preparation process are also commonly used in the art for preparing oxygen evolution electrodes.

[0047] The fifth aspect of the present invention provides an electrolytic cell, wherein the anode of the electrolytic cell is the oxygen evolution electrode described in the fourth aspect.

[0048] The sixth aspect of the present invention provides the application of the boron-doped composite catalyst described in the first or third aspect in the electrolysis of water to produce hydrogen.

[0049] The present invention will be described in detail below through examples. In the following examples, the valence state of Ni before and after doping with B was determined by X-ray photoelectron spectroscopy (XPS); the layer thickness of the boron-doped composite catalyst was determined by transmission electron microscopy (TEM); the atomic molar ratio of B, Ni, Fe, and Co was determined by TEM energy dispersive spectroscopy (EDS); the oxygen evolution overpotential was determined by LSV linear scanning voltammetry; the perfluorosulfonic acid polymer (Nafion) was a commercially available product from Innoca, under the brand name Nafion 117; and the nickel foam substrate was a commercially available product from Innoca.

[0050] Example 1 (1) Weigh 0.5 mmol of Fe(NO3)3·9H2O, 0.5 mmol of cobalt nitrate, 2.7 mmol of urea (CO(NH)2), 6 mmol of H3BO3, and 10 mmol of NH4F, mix with 30 ml of deionized water, and sonicate for 30 min.

[0051] (2) Prepare a precursor solution from the solution obtained in step (1) and transfer it to a 50ml hydrothermal reactor. Place the nickel foam substrate (length × width × thickness 1cm × 2.5cm × 1mm, nickel content 99.5wt%) into the precursor solution and perform hydrothermal crystallization at 120℃ for 12h. Rinse the surface of the obtained product with deionized water.

[0052] TEM image of boron-doped composite catalyst as follows Figure 1 As shown in the figure, the catalyst is a two-dimensional nanostructure with a thickness of approximately 45 nm. Its EDS (Energy Dispersive X-ray Spectroscopy) results indicate that the molar ratio of B:Fe:Ni:Co is 6:1:5:3.

[0053] Figure 2 The Fourier transform diagram of the boron-doped composite catalyst shows that the catalyst has obvious lattice dislocations, indicating that its surface has a large number of defect structures.

[0054] Figure 3 XPS spectra of Ni in boron-doped composite catalysts and undoped catalysts are shown, comparing the Ni content before and after boron doping. 3+ The proportion has increased, and according to peak fitting, it accounts for approximately 68% of the total Ni molar ratio.

[0055] A three-electrode system was constructed using a catalyst-coated nickel foam (0.5 cm × 1 cm) as the working electrode, a graphite rod as the counter electrode, a standard hydrogen electrode as the reference electrode, and 1 M KOH solution as the electrolyte. The catalyst was activated and stabilized using cyclic voltammetry, and its OER performance was evaluated using linear sweep voltammetry.

[0056] Electrochemical testing was conducted using a Shanghai Chenhua 760E electrochemical workstation. Before testing, N2 was bubbled through the electrolyte for approximately 30 minutes to saturate it. Subsequently, the three-electrode testing system was assembled, with the voltage range set at 0-1.2V (vs. RHE). CV scans were performed for 20 cycles at scan rates of 100mV / s and 50mV / s to ensure complete sample activation and exposure of active sites. LSV testing was then conducted at 1.2-1.8V. AC impedance spectroscopy was used to assess the material's resistance, allowing for the analysis and comparison of the kinetic activity between different materials. Testing conditions: a 10mV perturbation near the test voltage, with a frequency range of 1Hz-100kHz.

[0057] LSV test results for the sample and the undoped boron catalyst are as follows: Figure 4 As shown, at a current density of 100 mA / cm² 2 At this time, the oxygen evolution overpotential was 278 mV, significantly better than the oxygen evolution performance of the undoped NiFeCo-LTH catalyst. The AC impedance spectra of the sample, the undoped catalyst, and the metal-based nickel foam are shown below. Figure 5 As shown, the charge conduction resistance decreases after doping with B, to approximately 50 mΩ.

[0058] Example 2 A boron-doped composite catalyst was prepared according to the method in Example 1, except that 9 mmol of H3BO3 was added. The catalyst thickness was approximately 55 nm, and the molar ratio of B:Fe:Ni:Co was 7:1:5:3. 3+ It accounts for approximately 70% of the total Ni molar ratio. Current density: 100 mA / cm². 2 At that time, the oxygen evolution overpotential is 270mV. The AC impedance is approximately 45mΩ.

[0059] Example 3 A boron-doped composite catalyst was prepared according to the method in Example 1, except that the hydrothermal crystallization temperature was 150°C. The catalyst thickness was approximately 50 nm, and Ni... 3+ The molar ratio of B to Fe is approximately 65% ​​of the total Ni. The molar ratio of B to Fe is 5.8:1:5:3. The current density is 100 mA / cm². 2 At that time, the oxygen evolution overpotential is 280mV. The AC impedance is approximately 53mΩ.

[0060] Example 4 The boron-doped composite catalyst was prepared according to the method in Example 1, except that the hydrothermal crystallization temperature was 100°C in step (3). The catalyst thickness was approximately 25 nm, and the molar ratio of B:Fe:Ni:Co was 5:1:5:3. 3+ The molar percentage of total Ni is approximately 55%. Current density: 100 mA / cm². 2 At that time, the oxygen evolution overpotential is 290mV. The AC impedance is approximately 55mΩ.

[0061] Example 5 A boron-doped composite catalyst was prepared according to the method in Example 1, except that the amounts of cobalt nitrate and iron nitrate added were changed to 1 mmol each. The catalyst thickness was approximately 35 nm, and the molar ratio of B:Fe:Ni:Co was 6:1:5:3. 3+ It accounts for approximately 68% of the total Ni molar ratio. Current density: 100 mA / cm². 2 At that time, the oxygen evolution overpotential is 275mV. The AC impedance is approximately 57mΩ.

[0062] Example 6 A boron-doped composite catalyst was prepared according to the method in Example 1, except that the amount of urea added was changed to 1.5 mmol. The catalyst thickness was approximately 35 nm, and the molar ratio of B:Fe:Ni:Co was 6:2:2:4. 3+ It accounts for approximately 75% of the total Ni molar ratio. Current density: 100 mA / cm². 2 At that time, the oxygen evolution overpotential is 275mV. The AC impedance is approximately 47mΩ.

[0063] Example 7 A boron-doped composite catalyst was prepared according to the method in Example 1, except that the amount of urea added was changed to 5 mmol. The catalyst thickness was approximately 45 nm, and the molar ratio of B:Fe:Ni:Co was 6:2:7:5. 3+ The molar percentage of total Ni is approximately 56%. Current density: 100 mA / cm². 2 At that time, the oxygen evolution overpotential is 295mV. The AC impedance is approximately 60mΩ.

[0064] Comparative Example 1 A boron-doped composite catalyst was prepared according to the method of Example 1, except that in step (2), the amount of H3BO3 added was 0. The catalyst thickness was approximately 20 nm, and Ni... 3+ The molar proportion of Ni in the total Ni is approximately 40%. Current density: 100 mA / cm² 2 At that time, the oxygen evolution overpotential is 350mV. The AC impedance is approximately 75mΩ.

[0065] Comparative Example 2 A boron-doped composite catalyst was prepared according to the method of Example 1, except that in step (1), the amount of cobalt nitrate added was 0, and the amount of Fe(NO3)3·9H2O added was 0.75 mmol. The catalyst thickness was approximately 35 nm, and Ni... 3+ The molar percentage of total Ni is approximately 55%. Current density: 100 mA / cm². 2 At that time, the oxygen evolution overpotential is 385mV. The AC impedance is approximately 95mΩ.

[0066] Comparative Example 3 The boron-doped composite catalyst was prepared according to the method of Example 1, except that in step (2), the amount of H3BO3 added was 1 mmol.

[0067] The catalyst has a two-dimensional nanostructure with a thickness of approximately 25 nm; the molar ratio of B:Fe:Ni:Co is 2:1:5:3; Ni 3+ The molar ratio of Ni to total Ni is approximately 50%; at a current density of 100 mA / cm² 2 At that time, the oxygen evolution overpotential was 315mV; the AC impedance was approximately 65mΩ.

[0068] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A boron-doped composite catalyst, characterized in that, The composite catalyst contains Fe, Ni, B and Co, and the molar ratio of Fe, Ni, B and Co is 0.1-1:0.2-3:1-3:

1.

2. The composite catalyst according to claim 1, wherein, In the composite catalyst, the molar ratio of Fe, Ni, B and Co is 0.2-0.5:0.4-2:1.2-2.5:

1.

3. The composite catalyst according to claim 1 or 2, wherein, After doping with B, the composite catalyst contains Ni 3+ The molar proportion of Ni is 50-80%; And / or, the composite catalyst is used at a current density of 100 mA / cm². 2 The oxygen evolution overpotential is 180-280mV. And / or, the average thickness of the composite catalyst is 20-60 nm, preferably 25-55 nm.

4. A method for preparing a boron-doped composite catalyst, characterized in that, The method includes: (1) In the presence of a solvent, mix an iron source, a cobalt source, a boron source, an alkaline substance, and a mineralizing agent; (2) The mixture obtained in step (1) is mixed with a nickel-containing metal substrate for hydrothermal crystallization; wherein the amounts of iron source, nickel-containing metal substrate, boron source and cobalt source are such that the molar ratio of Fe, Ni, B and Co in the composite catalyst is 0.1-1:0.2-3:1-3:

1.

5. The preparation method according to claim 4, wherein, The amount of iron source, nickel-containing metal substrate, boron source and cobalt source used makes the molar ratio of Fe, Ni, B and Co in the composite catalyst 0.2-0.5:0.4-2:1.2-2.5:

1.

6. The preparation method according to claim 4 or 5, wherein, The iron source is selected from at least one of ferric nitrate, ferric sulfate, and ferric chloride; And / or, the cobalt source is selected from at least one of cobalt nitrate, cobalt sulfate, and cobalt chloride; And / or, the boron source is selected from at least one of boric acid, cobalt borate, and nickel borate; And / or, the nickel-containing metal substrate is selected from at least one of nickel substrate, nickel-iron substrate and nickel felt.

7. The preparation method according to claim 4 or 5, wherein, The molar amount of the alkaline substance is 1-5 times the total molar amount of cobalt and iron, preferably 1.5-3 times. And / or, the molar amount of the mineralizing agent is 3-10 times the total molar amount of cobalt and iron; And / or, the alkaline substance is selected from urea and / or sodium hydroxide; And / or, the mineralizing agent is selected from ammonium fluoride.

8. The preparation method according to claim 4 or 5, wherein, The conditions for hydrothermal crystallization include: a hydrothermal crystallization temperature of 90-180℃, preferably 110-150℃; and a hydrothermal crystallization time of 8-24h, preferably 10-15h.

9. The boron-doped composite catalyst prepared by the method according to any one of claims 4-8.

10. An oxygen evolution electrode, characterized in that, The oxygen evolution electrode comprises the boron-doped composite catalyst as described in any one of claims 1-3 or 9.

11. An electrolytic cell, characterized in that, The anode of the electrolytic cell is the oxygen evolution electrode as described in claim 10.

12. The application of the boron-doped composite catalyst according to any one of claims 1-3 or 9 in hydrogen production by water electrolysis.

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