Nickel-based composite material, preparation method of nickel-based composite material and application of nickel-based composite material in alkaline electrolyzed water cathode electrode

Abstract

The invention provides a nickel-based composite material, a preparation method of the nickel-based composite material and application of the nickel-based composite material in an alkaline electrolyzed water cathode electrode, and belongs to the technical field of electrolyzed water electrodes. The nickel-based composite material comprises a metallic nickel substrate and a nickel and rhenium-based metal / oxide composite material which is arranged on the metallic nickel substrate and is bonded with the metallic nickel substrate through a metallic bond. The preparation method comprises the steps that a metal nickel substrate is placed in a fused salt precursor to form a fused salt system, under inert atmosphere protection, a reaction is carried out under preset temperature and air pressure, surface modification is carried out on the metal nickel substrate, and the nickel-based composite material is obtained. The nickel-based composite material provided by the invention shows high-efficiency electro-catalysis water decomposition performance and can be applied to an alkaline electrolysis water cathode electrode.

Description

Technical Field

[0001] The present invention belongs to the technical field of water electrolysis electrode materials, and in particular relates to a nickel-based composite material, a preparation method thereof and an application thereof in an alkaline water electrolysis cathode electrode. Background Art

[0002] Hydrogen is primarily obtained through fossil fuel conversion, including methane reforming and coal-to-hydrogen production. These processes, however, are inherently high-emission and highly polluting. Currently, water electrolysis, which utilizes renewable energy sources (wind, solar, and hydropower), is gaining momentum and is expected to become the greenest hydrogen production method. Alkaline water electrolysis is expected to be the first to achieve large-scale hydrogen production. The cathode in alkaline water electrolysis involves the hydrogen evolution reaction, which is directly related to the performance of hydrogen produced by water electrolysis.

[0003] Currently, the predominant cathode surfactant in commercial alkaline water electrolysis is nickel-based nanoparticles. However, their intrinsic catalytic activity is severely limited, resulting in energy consumption that cannot meet increasingly stringent economic targets for water electrolysis. Further improving cathode performance within the non-precious metal category is a current research hotspot in the hydrogen energy materials field.

[0004] Nickel-based composites are currently a hot topic in research. Compared to pure nickel nanomaterials, they offer significant advantages in alkaline water electrolysis. However, the use of non-precious metal components in nickel-based composites remains a significant challenge in achieving the catalytic performance of precious metals. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a nickel-based composite material, a preparation method thereof and an application thereof in a cathode electrode for alkaline water electrolysis.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: In a first aspect, a nickel-based composite material is provided, comprising a metallic nickel substrate and a fluorine ion-doped nickel or rhenium-based metal / oxide composite, wherein the fluorine ion-doped nickel or rhenium-based metal / oxide composite is metallically bonded to the metallic nickel substrate, the nickel or rhenium-based metal / oxide composite material is composed of nickel, nickel oxide, rhenium oxide, or a nickel-rhenium alloy, and fluorine ions are doped in the oxygen sites of the nickel oxide and rhenium oxide, the nickel or rhenium-based metal / oxide composite material has nanogrooves and pores, and the pores are distributed on the surface of the nanogrooves.

[0007] In some embodiments, the nano-grooves have a length in the range of 100-600 nm, a depth in the range of 40-120 nm, a width in the range of 20-60 nm, and a pore diameter in the range of 5-30 nm.

[0008] In a second aspect, a method for preparing a nickel-based composite material is provided, the method comprising the following steps: S1. Placing a metallic nickel substrate in a molten salt precursor to form a molten salt system, wherein the molten salt system is protected by an inert atmosphere; wherein the molten salt precursor contains aluminum, rhenium, and fluorine; S2. The molten salt system reacts at a preset temperature and pressure to modify the surface of the metal nickel substrate to obtain a nickel-based composite material; the surface material of the nickel-based composite material has nano-grooves and pores, and the pores are distributed on the surface of the nano-grooves.

[0009] In some embodiments, the metal nickel substrate is a metal nickel substrate that has been surface cleaned.

[0010] In some embodiments, the specific steps of the surface cleaning treatment are: placing the metal nickel substrate in an acetone solution for ultrasonic cleaning for 10 to 30 minutes, and then repeatedly cleaning with ethanol to remove the grease layer on the metal surface; placing the metal nickel substrate after the grease layer on the metal surface is removed in a hydrochloric acid solution with a concentration of 1 to 6 mol / L for ultrasonic cleaning for 5 to 25 minutes, and letting it stand for 10 to 30 minutes, and then repeatedly cleaning with distilled water to remove the oxide layer on the metal surface, and drying to obtain the metal nickel substrate after the surface cleaning treatment.

[0011] In some embodiments, the metal nickel substrate is any one of a nickel mesh, nickel foam, and a nickel sheet.

[0012] In some embodiments, the inert atmosphere is any one of nitrogen and argon, or any combination thereof.

[0013] In some embodiments, in the molten salt precursor, the mass percentage of aluminum element is 55% to 75%, the mass percentage of rhenium element is 4% to 16%, and the mass percentage of fluorine element is 2% to 12%.

[0014] In some embodiments, the molten salt precursor is obtained by mixing aluminum chloride, ammonium fluoride, and ammonium perrhenate.

[0015] In some embodiments, the temperature is 70-210° C., the gas pressure is 0.8-12 MPa, and the reaction time is 12-60 h.

[0016] In some embodiments, the surface material of the nickel-based composite material is a fluoride-doped nickel or rhenium-based metal / oxide composite, the fluoride-doped nickel or rhenium-based metal / oxide composite is metallically bonded to the metal nickel substrate, and the nickel or rhenium-based metal / oxide composite material is composed of nickel, nickel oxide, rhenium oxide, and nickel-rhenium alloy, and fluoride ions are doped in the oxygen sites of nickel oxide and rhenium oxide.

[0017] In a third aspect, there is provided a use of the nickel-based composite material or the nickel-based composite material prepared by the above-mentioned preparation method in a cathode electrode for alkaline water electrolysis.

[0018] The above technical solution of the present invention has one or at least some of the following advantages compared to the prior art: (1) The nickel-based composite material of the present invention, its preparation method and its application in the cathode electrode of alkaline water electrolysis, based on the chemical reaction in the molten salt, forms a nickel and rhenium-based metal / oxide composite material on the surface of the base nickel. Compared with pure nickel material, the electrolysis performance of water is significantly improved, especially when the metal nickel base is foamed nickel, the electrolysis performance is higher than that of precious metal materials; (2) The surface material of the nickel-based composite material prepared by the present invention is bonded to the base metal by a metallic bond, and has a strong bonding force, showing good mechanical stability and electrocatalytic durability. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The technical solutions and beneficial effects of the present invention will be made apparent by describing in detail the specific embodiments of the present invention in conjunction with the accompanying drawings.

[0020] Figure 1 This is a flow chart of a method for modifying a cathode electrode of alkaline water electrolysis with low-temperature molten salt according to an embodiment of the present invention; Figure 2 This is a scanning electron microscope image of a local area of the final electrode surface material corresponding to Example 1; Figure 3 1 is the element energy spectrum distribution diagram in the local area of the final electrode surface material corresponding to Example 1; Figure a is the distribution of nickel elements, Figure b is the distribution of rhenium elements, Figure c is the distribution of fluorine elements, and Figure d is the distribution of oxygen elements. DETAILED DESCRIPTION

[0021] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making any creative efforts shall fall within the scope of protection of the present invention.

[0022] This embodiment provides a method for preparing a nickel-based composite material. Figure 1 As shown, the following steps are included: S10. Placing a metallic nickel substrate in a molten salt precursor to form a molten salt system, wherein the molten salt system is protected by an inert atmosphere; wherein the molten salt precursor contains aluminum, rhenium, and fluorine; S20. The molten salt system reacts at a preset temperature and pressure to modify the surface of a metallic nickel substrate, thereby producing a nickel-based composite material. A surface material of the nickel-based composite material has nanogrooves and pores, with the pores distributed across the surface of the nanogrooves. The surface material and the substrate are bonded by a strong metallic bond. The nickel in the surface material originates from the substrate and does not have a strict interface with the nickel within the substrate.

[0023] In some preferred embodiments of the present invention, the metal nickel substrate is a metal nickel substrate that has been surface cleaned.

[0024] In some preferred embodiments of the present invention, step S10 is specifically as follows: S11: placing a metal nickel substrate in an acetone solution for ultrasonic cleaning for 10 to 30 minutes, and then repeatedly cleaning with ethanol to remove the grease layer on the metal surface. The ultrasonic cleaning time is preferably 10 minutes, 15 minutes, 20 minutes, 25 minutes or 30 minutes. The metal nickel substrate is preferably any one of a nickel mesh, nickel foam or nickel sheet; S12: placing the metal nickel substrate after removing the grease layer on the metal surface in a hydrochloric acid solution with a concentration of 1 to 6 mol / L and ultrasonically treating it for 5 to 25 minutes, and letting it stand for 10 to 30 minutes. Then, repeatedly washing it with distilled water to remove the oxide layer on the metal surface, and drying it to obtain a metal nickel substrate after surface cleaning. Preferably, the concentration of the hydrochloric acid solution is 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L or 6 mol / L. The ultrasonic time is preferably 5 minutes, 10 minutes, 15 minutes, 20 minutes or 25 minutes, and the standing time is preferably 10 minutes, 15 minutes, 20 minutes, 25 minutes or 30 minutes.

[0025] S13: placing the metal nickel substrate after surface cleaning in a molten salt precursor, and the two form a molten salt system, and the molten salt system is protected by an inert atmosphere.

[0026] The molten salt precursor is a mixture of aluminum chloride, ammonium fluoride, and ammonium perrhenate. The melting point of the mixture is affected by the proportion of the components. Preferably, in the molten salt precursor, the mass percentage of the aluminum element is 55% to 75%, preferably 55%, 60%, 70% or 75%, the mass percentage of the rhenium element is 4% to 16%, preferably 4%, 8%, 12% or 16%, and the mass percentage of the fluorine element is 2% to 12%, preferably 2%, 6%, 9% or 12%. The inert atmosphere is any one of nitrogen and argon, or any combination thereof.

[0027] In some preferred embodiments of the present invention, step S20 is specifically as follows: S21 heats the molten salt system to 70-210°C. Those skilled in the art can set different temperatures according to the different component ratios of the molten salt, such as 70°C, 120°C, 170°C or 210°C, and at the same time adjust the air pressure of the molten salt system to 0.8-12MPa, preferably 0.8MPa, 2.8MPa, 8.5MPa or 12MPa, maintain the temperature and air pressure for 12-60h, preferably 12h, 28h, 48h or 60h, and perform modification treatment on the metal nickel substrate after surface cleaning.

[0028] S22 rinses the metal nickel substrate modified with molten salt with distilled water and dries it to obtain a nickel-based composite material (final electrode). The surface material of the final electrode is a fluorine ion-doped nickel and rhenium-based metal / oxide composite material, whose components include nickel, nickel oxide, rhenium oxide, and nickel-rhenium alloy. Fluorine ions are doped in the oxygen sites of nickel oxide and rhenium oxide. The fluorine ion-doped nickel and rhenium-based metal / oxide composite material is bonded to the metal nickel substrate with a metal bond. The surface material of the final electrode exhibits nano-grooves and pores, and the pores are distributed on the surface of the gullies, wherein the length of the gullies is in the range of 100~600nm, the depth is in the range of 40~120nm, the width is in the range of 20~60nm, and the pore diameter is in the range of 5~30nm.

[0029] An embodiment of the present invention also provides a nickel-based composite material, comprising a metal nickel substrate and a nickel and rhenium-based metal / oxide composite material arranged on the metal nickel substrate and bonded to the metal nickel substrate by metal bonds. The nickel and rhenium-based metal / oxide composite material is composed of nickel, nickel oxide, rhenium oxide, and nickel-rhenium alloy, and fluorine ions are doped in the oxygen sites of the nickel oxide and rhenium oxide. The nickel and rhenium-based metal / oxide composite material has nano-grooves and pores, and the pores are distributed on the surface of the nano-grooves.

[0030] An embodiment of the present invention also provides an application of a nickel-based composite material in a cathode electrode for alkaline water electrolysis.

[0031] The present invention will be further described below by means of specific embodiments; Example 1 The method for preparing an electrode using nickel mesh as a metal nickel substrate is as follows: S11 Place a 40-mesh plain nickel mesh in an acetone solution and ultrasonically clean it for 20 minutes, then repeatedly clean it with ethanol to remove the grease layer on the metal surface.

[0032] S12: The nickel mesh after the grease layer on the metal surface is removed is placed in a hydrochloric acid solution with a concentration of 4 mol / L and ultrasonicated for 15 minutes, and then allowed to stand for 20 minutes. It is then repeatedly washed with distilled water to remove the oxide layer on the metal surface. After drying, the nickel mesh after surface cleaning is obtained.

[0033] S21 places the metal nickel substrate after surface cleaning treatment in a molten salt precursor, and the two form a molten salt system. The molten salt system is protected by a nitrogen atmosphere. The molten salt precursor is composed of three components: aluminum chloride, ammonium fluoride, and ammonium perrhenate, wherein the mass percentage of aluminum element is 55%, the mass percentage of rhenium element is 8%, and the mass percentage of fluorine element is 12%.

[0034] S22 raises the temperature of the molten salt system to 170° C., and adjusts the gas pressure of the molten salt system to 2.8 MPa. The temperature and gas pressure are maintained for 12 hours to modify the metal nickel substrate after the surface cleaning treatment.

[0035] S23 rinses the metal nickel substrate modified with molten salt with distilled water and dries to obtain the final electrode, wherein the surface material of the final electrode is a fluoride-doped nickel and rhenium-based metal / oxide composite material, whose components include nickel, nickel oxide, rhenium oxide, and nickel-rhenium alloy, and fluorine ions are doped in the oxygen sites of nickel oxide and rhenium oxide. The composite material is bonded to the metal nickel substrate with a metal bond, and the surface material of the final electrode exhibits nano-grooves and pores, and the pores are distributed on the surface of the gullies, wherein the gully length is 100~600nm, the depth is 40~120nm, the width is 20~60nm, and the pore diameter is 5~30nm. Figure 2 The corresponding scanning electron microscope images of the local area of the final electrode surface material are shown. Figure 3 The corresponding element energy spectrum distribution diagram in the local area of the final electrode surface material is displayed.

[0036] Example 2 The method for preparing an electrode using nickel foam as a metal nickel substrate is as follows: S11 The nickel foam was placed in an acetone solution for ultrasonic cleaning for 30 min, and then repeatedly cleaned with ethanol to remove the grease layer on the metal surface.

[0037] S12: The nickel foam after removing the grease layer on the metal surface is placed in a hydrochloric acid solution with a concentration of 6 mol / L and ultrasonicated for 5 minutes, and then allowed to stand for 30 minutes, and then repeatedly washed with distilled water to remove the oxide layer on the metal surface. After drying, the nickel foam after the surface cleaning treatment is obtained.

[0038] S21 places the metal nickel substrate after surface cleaning treatment in a molten salt precursor, and the two form a molten salt system. The molten salt system is protected by an argon atmosphere. The molten salt precursor is composed of three components: aluminum chloride, ammonium fluoride, and ammonium perrhenate, wherein the mass percentage of aluminum element is 75%, the mass percentage of rhenium element is 4%, and the mass percentage of fluorine element is 2%.

[0039] S22 raises the temperature of the molten salt system to 120° C., and adjusts the gas pressure of the molten salt system to 12 MPa. The temperature and gas pressure are maintained for 28 hours, and the metal nickel substrate after the surface cleaning treatment is modified.

[0040] S23 rinses the metal nickel substrate modified with molten salt with distilled water and dries to obtain the final electrode, wherein the surface material of the electrode finally obtained is a nickel and rhenium-based metal / oxide composite material doped with fluorine ions, and its components include nickel, nickel oxide, rhenium oxide, and nickel-rhenium alloy. Fluorine ions are doped in the oxygen sites of nickel oxide and rhenium oxide, and the composite material is bonded to the metal nickel substrate with a metal bond. The surface material of the electrode finally obtained exhibits nano-grooves and pores, and the pores are distributed on the surface of the grooves, wherein the length of the grooves is in the range of 100~600nm, the depth is in the range of 40~120nm, the width is in the range of 20~60nm, and the pore diameter is in the range of 5~30nm.

[0041] Example 3 The method for preparing an electrode using a nickel sheet as a metal nickel substrate is as follows: S11 Place the nickel sheet in an acetone solution and ultrasonically clean it for 10 minutes, then repeatedly clean it with ethanol to remove the grease layer on the metal surface.

[0042] S12: The nickel sheet after the grease layer on the metal surface is removed is placed in a hydrochloric acid solution with a concentration of 1 mol / L and ultrasonicated for 25 minutes, and then allowed to stand for 10 minutes. The nickel sheet is then repeatedly washed with distilled water to remove the oxide layer on the metal surface. After drying, the nickel sheet with a clean surface is obtained.

[0043] S21 places the metal nickel substrate after surface cleaning treatment in a molten salt precursor, and the two form a molten salt system. The molten salt system is protected by an argon atmosphere. The molten salt precursor is composed of three components: aluminum chloride, ammonium fluoride, and ammonium perrhenate, wherein the mass percentage of aluminum element is 70%, the mass percentage of rhenium element is 16%, and the mass percentage of fluorine element is 6%.

[0044] S22 raises the temperature of the molten salt system to 70° C., and adjusts the gas pressure of the molten salt system to 0.8 MPa. The temperature and gas pressure are maintained for 60 hours to modify the metal nickel substrate after the surface cleaning treatment.

[0045] S23 rinses the metal nickel substrate modified with molten salt with distilled water and dries to obtain the final electrode, wherein the final electrode surface material is a fluorine ion-doped nickel and rhenium-based metal / oxide composite material, whose components include nickel, nickel oxide, rhenium oxide, and nickel-rhenium alloy, and fluorine ions are doped in the oxygen sites of nickel oxide and rhenium oxide. The composite material is bonded to the metal nickel substrate with a metal bond, and the final electrode surface material exhibits nano-grooves and pores, and the pores are distributed on the gully surface, wherein the gully length is 100~600nm, the depth is 40~120nm, the width is 20~60nm, and the pore diameter is 5~30nm.

[0046] Example 4 The method for preparing an electrode using nickel foam as a metal nickel substrate is as follows: S11 Place the nickel foam in an acetone solution for ultrasonic cleaning for 25 minutes, and then repeatedly clean it with ethanol to remove the grease layer on the metal surface.

[0047] S12: The nickel foam after removing the grease layer on the metal surface is placed in a hydrochloric acid solution with a concentration of 3 mol / L and ultrasonicated for 10 minutes, and then allowed to stand for 25 minutes, and then repeatedly washed with distilled water to remove the oxide layer on the metal surface. After drying, the nickel foam after the surface cleaning treatment is obtained.

[0048] S21 places the metal nickel substrate after surface cleaning treatment in a molten salt precursor, and the two form a molten salt system. The molten salt system is protected by an argon atmosphere. The molten salt precursor is composed of three components: aluminum chloride, ammonium fluoride, and ammonium perrhenate, wherein the mass percentage of aluminum element is 60%, the mass percentage of rhenium element is 12%, and the mass percentage of fluorine element is 9%.

[0049] S22 raises the temperature of the molten salt system to 210° C., and adjusts the gas pressure of the molten salt system to 8.5 MPa. The temperature and gas pressure are maintained for 48 hours to modify the metal nickel substrate after the surface cleaning treatment.

[0050] S23 rinses the metal nickel substrate modified with molten salt with distilled water and dries to obtain the final electrode, wherein the final electrode surface material is a fluorine ion-doped nickel and rhenium-based metal / oxide composite material, whose components include nickel, nickel oxide, rhenium oxide, and nickel-rhenium alloy, and fluorine ions are doped in the oxygen sites of nickel oxide and rhenium oxide. The composite material is bonded to the metal nickel substrate with a metal bond, and the final electrode surface material exhibits nano-grooves and pores, and the pores are distributed on the gully surface, wherein the gully length is 100~600nm, the depth is 40~120nm, the width is 20~60nm, and the pore diameter is 5~30nm.

[0051] Comparative Example 1: This comparative example 1 directly uses 40 mesh plain nickel mesh as the electrode: A 40-mesh plain nickel mesh is ultrasonically cleaned in an acetone solution for 20 minutes, and then repeatedly cleaned with ethanol to remove the grease layer on the surface of the nickel mesh; S12: the nickel mesh after the surface grease layer is removed is placed in a 4 mol / L hydrochloric acid solution for ultrasonic cleaning for 15 minutes, and allowed to stand for 20 minutes, and then repeatedly cleaned with distilled water to remove the oxide layer on the metal surface, and dried to obtain a clean nickel mesh.

[0052] Comparative Example 2: Comparative Example 2 directly uses nickel foam as the electrode: The nickel foam is placed in an acetone solution for ultrasonic cleaning for 30 minutes, and then repeatedly cleaned with ethanol to remove the grease layer on the surface of the nickel foam; S12: the nickel foam after the grease layer on the surface is placed in a hydrochloric acid solution with a concentration of 6 mol / L for ultrasonic cleaning for 5 minutes, and allowed to stand for 30 minutes, and then repeatedly cleaned with distilled water to remove the oxide layer on the metal surface, and dried to obtain a clean nickel foam.

[0053] Comparative Example 3: This comparative example 3 directly uses nickel sheets as electrodes: The nickel sheet is ultrasonically cleaned in an acetone solution for 10 minutes, and then repeatedly cleaned with ethanol to remove the grease layer on the surface of the nickel sheet; S12 The nickel sheet after the grease layer is removed is placed in a hydrochloric acid solution with a concentration of 1 mol / L and ultrasonically cleaned for 25 minutes, and allowed to stand for 10 minutes, and then repeatedly cleaned with distilled water to remove the oxide layer on the metal surface, and dried to obtain a clean nickel sheet.

[0054] Comparative Example 4: In Comparative Example 4, nickel foam was used as the nickel metal substrate and coated with a noble metal catalyst to prepare an electrode: S11 Place the nickel foam in an acetone solution for ultrasonic cleaning for 25 minutes, and then repeatedly clean it with ethanol to remove the grease layer on the metal surface.

[0055] S12: The nickel foam after removing the grease layer on the metal surface is placed in a hydrochloric acid solution with a concentration of 3 mol / L and ultrasonicated for 10 minutes, and then allowed to stand for 25 minutes, and then repeatedly washed with distilled water to remove the oxide layer on the metal surface. After drying, the nickel foam after the surface cleaning treatment is obtained.

[0056] S21: The nickel foam after surface cleaning was placed as the substrate. 8 mg of Pt / C catalyst was evenly dispersed in 50 μL of isopropanol to form a slurry. Then 7.7 μL was added dropwise to the surface of the cleaned nickel foam. The catalyst loading was 4.9 mg cm −2 .

[0057] S22 After the slurry naturally dries to form a thin film, 2 μL of diluted Nafion solution (0.3 wt%) is added to its surface to protect the film. After final drying, a Pt / C electrode for comparative example is obtained.

[0058] Comparative Example 5 The method for preparing an electrode using nickel foam as a metal nickel substrate is as follows: S11 Place the nickel foam in an acetone solution for ultrasonic cleaning for 25 minutes, and then repeatedly clean it with ethanol to remove the grease layer on the metal surface.

[0059] S12: The nickel foam after removing the grease layer on the metal surface is placed in a hydrochloric acid solution with a concentration of 3 mol / L and ultrasonicated for 10 minutes, and then allowed to stand for 25 minutes, and then repeatedly washed with distilled water to remove the oxide layer on the metal surface. After drying, the nickel foam after the surface cleaning treatment is obtained.

[0060] S21 places the metal nickel substrate after surface cleaning treatment in a molten salt precursor, and the two form a molten salt system. The molten salt system is protected by an argon atmosphere. Compared with the molten salt precursor in Example 4, only the ammonium perrhenate component is removed from the molten salt precursor, and the remaining two components, aluminum chloride and ammonium fluoride, do not change in mass and proportion.

[0061] S22 raises the temperature of the molten salt system to 210° C., and adjusts the gas pressure of the molten salt system to 8.5 MPa. The temperature and gas pressure are maintained for 48 hours to modify the metal nickel substrate after the surface cleaning treatment.

[0062] S23 rinses the metal nickel substrate modified with molten salt with distilled water and dries to obtain the final electrode, wherein the surface material of the electrode finally obtained is a nickel-based metal / fluoride composite material doped with fluoride ions, and its components include nickel and nickel fluoride. The composite material is bonded to the metal nickel substrate with a metal bond, and the surface material of the electrode finally obtained exhibits nano-grooves and pores, and the pores are distributed on the surface of the grooves, wherein the groove length is 100~600nm, the depth is 40~120nm, the width is 20~60nm, and the pore diameter is 5~30nm.

[0063] Comparative Example 6 The method for preparing an electrode using nickel foam as a metal nickel substrate is as follows: S11 Place the nickel foam in an acetone solution for ultrasonic cleaning for 25 minutes, and then repeatedly clean it with ethanol to remove the grease layer on the metal surface.

[0064] S12: The nickel foam after removing the grease layer on the metal surface is placed in a hydrochloric acid solution with a concentration of 3 mol / L and ultrasonicated for 10 minutes, and then allowed to stand for 25 minutes, and then repeatedly washed with distilled water to remove the oxide layer on the metal surface. After drying, the nickel foam after the surface cleaning treatment is obtained.

[0065] S21 places the metal nickel substrate after surface cleaning treatment in a molten salt precursor, and the two form a molten salt system. The molten salt system is protected by an argon atmosphere. The molten salt precursor is composed of three components: aluminum chloride, ammonium fluoride, and ammonium perrhenate, wherein the mass percentage of aluminum element is 50%, the mass percentage of rhenium element is 20%, and the mass percentage of fluorine element is 15%.

[0066] S22 raises the temperature of the molten salt system to 210° C., and adjusts the gas pressure of the molten salt system to 8.5 MPa. The temperature and gas pressure are maintained for 48 hours to modify the metal nickel substrate after the surface cleaning treatment.

[0067] S23 rinses the metal nickel substrate modified with molten salt with distilled water and dries to obtain the final electrode, wherein the final electrode surface material is a fluorine ion-doped nickel and rhenium-based metal / oxide composite material, whose components include nickel, nickel oxide, rhenium oxide, and nickel-rhenium alloy, and fluorine ions are doped in the oxygen sites of nickel oxide and rhenium oxide. The composite material is bonded to the metal nickel substrate with a metal bond, and the final electrode surface material exhibits nano-grooves and pores, and the pores are distributed on the gully surface, wherein the gully length is 100~600nm, the depth is 40~120nm, the width is 20~60nm, and the pore diameter is 5~30nm.

[0068] Analysis of electrode catalytic performance: The electrodes obtained in Examples 1 to 4 and Comparative Examples 1 to 6 were tested for hydrogen evolution in alkaline water electrolysis using a linear voltammetric sweep test method. The test used a three-electrode system, with the electrodes obtained in each Example and Comparative Example as the working electrode, mercury / mercuric oxide as the reference electrode, and a graphite sheet as the auxiliary electrode. The electrolyte used was 1 mol / L potassium hydroxide, the scan rate was 5 mV / s, and the scan range was -0.8 volts to -1.75 volts. The hydrogen evolution electrocatalytic performance was tested on an electrochemical workstation (CHI760E, Shanghai Chenhua Instrument Co., Ltd.), and the test results correspond to Table 1.

[0069] Table 1 Overpotential of hydrogen evolution reaction at different test electrodes at a certain current density Test electrocatalyst preparation source Overpotential at a current density of 300 mA / cm² (unit: volts, relative to the reversible hydrogen electrode) Potential increase after 80 hours of continuous hydrogen evolution reaction at a current density of 500 mA / cm² (unit: millivolts, relative to the reversible hydrogen electrode) Example 1 0.581 75 Example 2 0.496 63 Example 3 0.703 93 Example 4 0.221 32 Comparative Example 1 1.022 234 Comparative Example 2 0.932 208 Comparative Example 3 1.271 222 Comparative Example 4 0.362 496 Comparative Example 5 0.622 326 Comparative Example 6 0.608 236 According to the data in Table 1, it can be seen that the hydrogen evolution reaction performance of the electrodes obtained by using different metal nickel substrates for the preparation of the relevant embodiments is significantly improved compared with the comparative electrodes based on the original metal substrate. In particular, the electrode prepared using nickel foam has an overpotential of only 0.221 volts at a current density of 300 milliamperes per square centimeter, which is 1.05 volts lower than that of the pure nickel foam electrode, and 0.141 volt lower than that of the electrode prepared by only surface cleaning and precious metal coating. At the same time, the overpotential of the electrode prepared using nickel foam after 80 hours of continuous hydrogen evolution reaction at a high current density is only 32 millivolts. In addition, by comparing Example 4 with Comparative Example 5, under the premise of removing the ammonium perrhenate molten salt precursor component, the surface material of the final electrode also undergoes significant changes, especially no oxide is generated in the surface material, and the electrode performance drops sharply. By comparing Example 4 with Comparative Example 6, when the ratio of the three components of the molten salt precursor aluminum chloride, ammonium fluoride, and ammonium perrhenate is inappropriately changed, the final electrode performance will also drop significantly.

[0070] The above technical solution of the present invention has one or at least some of the following advantages compared to the prior art: (1) The nickel-based composite material of the present invention, its preparation method and its application in the cathode electrode of alkaline water electrolysis, based on the chemical reaction in the molten salt, forms a nickel and rhenium-based metal / oxide composite material on the surface of the base nickel. Compared with pure nickel material, the electrolysis performance of water is significantly improved, especially when the metal nickel base is foamed nickel, the electrolysis performance is higher than that of precious metal materials; (2) The present invention provides a method for modifying a cathode electrode of alkaline water electrolysis with low-temperature molten salt and an electrode prepared therefrom. The surface material of the prepared electrode is bonded to the base metal by a metal bond, and exhibits good mechanical stability and electrocatalytic durability.

[0071] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A nickel-based composite material, characterized in that: The nickel-based composite material includes a metallic nickel substrate and a fluorine ion-doped nickel and rhenium-based metal / oxide composite. The fluorine ion-doped nickel and rhenium-based metal / oxide composite is bonded to the metallic nickel substrate by a metallic bond. The nickel and rhenium-based metal / oxide composite material is composed of nickel, nickel oxide, rhenium oxide, and a nickel-rhenium alloy, and fluorine ions are doped in the oxygen sites of the nickel oxide and rhenium oxide. The nickel and rhenium-based metal / oxide composite material has nano-grooves and pores, and the pores are distributed on the surface of the nano-grooves.

2. The nickel-based composite material according to claim 1, characterized in that The length of the nano-grooves is in the range of 100-600 nm, the depth is in the range of 40-120 nm, the width is in the range of 20-60 nm, and the aperture of the holes is in the range of 5-30 nm.

3. A method for preparing a nickel-based composite material, characterized in that: The preparation method comprises the following steps: S1. placing a metallic nickel substrate in a molten salt precursor to form a molten salt system, wherein the molten salt system is protected by an inert atmosphere; Wherein, the molten salt precursor contains aluminum, rhenium and fluorine; S2. The molten salt system reacts at a preset temperature and pressure to modify the surface of the metal nickel substrate to obtain a nickel-based composite material; The surface material of the nickel-based composite material has nano-grooves and holes, and the holes are distributed on the surface of the nano-grooves.

4. The preparation method according to claim 3, characterized in that The metal nickel substrate is any one of nickel mesh, nickel foam and nickel sheet.

5. The preparation method according to claim 3, characterized in that The inert atmosphere is any one of nitrogen and argon or any combination thereof.

6. The preparation method according to claim 3, characterized in that In the molten salt precursor, the mass percentage of aluminum element is 55% to 75%, the mass percentage of rhenium element is 4% to 16%, and the mass percentage of fluorine element is 2% to 12%.

7. The preparation method according to claim 3, characterized in that The molten salt precursor is obtained by mixing aluminum chloride, ammonium fluoride and ammonium perrhenate.

8. The preparation method according to claim 6, characterized in that The temperature is 70-210° C., the gas pressure is 0.8-12 MPa, and the reaction time is 12-60 hours.

9. The preparation method according to claim 3, characterized in that The surface material of the nickel-based composite material is a fluorine ion-doped nickel and rhenium-based metal / oxide composite. The fluorine ion-doped nickel and rhenium-based metal / oxide composite is bonded to the metal nickel substrate by a metallic bond. The nickel and rhenium-based metal / oxide composite material is composed of nickel, nickel oxide, rhenium oxide, and nickel-rhenium alloy, and fluorine ions are doped in the oxygen sites of nickel oxide and rhenium oxide.

10. Use of the nickel-based composite material according to claim 1 or 2 or the nickel-based composite material prepared by the preparation method according to any one of claims 3 to 9 in a cathode electrode for alkaline water electrolysis.

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