Carbon supported nickel-based core-shell catalyst and preparation method

Abstract

The application discloses a carbon-supported nickel-based core-shell catalyst and a preparation method thereof, wherein the core-shell catalyst supported on a carbon carrier comprises an inner core, an intermediate layer coated on the surface of the inner core, and an outer shell layer coated on the surface of the intermediate layer; the inner core comprises a nickel-cobalt alloy, the intermediate layer comprises a nickel-cobalt-molybdenum multi-metal oxide, and the outer shell layer comprises a molybdenum oxide. The application coats a porous molybdenum oxide outer shell layer on the surface of the intermediate layer, which not only does not affect the diffusion of reactants, but also effectively limits the oxidation of nickel into high-valence nickel oxide or hydroxide and limits the particle size of nickel-cobalt particles in the catalyst; during annealing reduction, the intermediate layer is gradually formed between the interface of the inner core and the outer shell layer, compared with single active sites of nano nickel, the intermediate layer provides a large number of reaction sites with high intrinsic activity, and therefore the core-shell structure not only guarantees the stability of the catalyst, but also has high catalytic activity.

Description

Technical Field

[0001] This invention relates to the field of hydrogen production by anion exchange membrane electrolysis of water, specifically to a carbon-supported nickel-based core-shell catalyst and its preparation method. Background Technology

[0002] With the transformation of energy structure and the increasing demand for clean energy, hydrogen production through water electrolysis has attracted widespread attention as an important technological path for achieving efficient conversion of renewable energy. Among various water electrolysis hydrogen production technologies, anion exchange membrane electrolyzers inherit the cost advantages of traditional alkaline electrolyzers while possessing some characteristics of proton exchange membrane electrolyzers in terms of hydrogen purity, energy efficiency, and operational safety. These electrolyzers can operate under relatively mild conditions, thus providing conditions for the application of non-precious metal catalysts in water electrolysis hydrogen production. Nickel-based materials, in particular, have garnered significant attention due to their good hydrogen evolution activity and cost advantages in alkaline environments. Carbon-supported nickel nanoparticle catalysts, with their high active area and excellent conductivity, are considered a promising form of cathode catalyst. However, in actual preparation and operation, existing carbon-supported nickel nanoparticle catalysts still face several challenges, such as insufficient uniformity of nickel metal particle distribution on the carbon support, easy agglomeration, insufficient activity of pure nickel reaction sites, and susceptibility to oxidation under intermittent conditions, leading to a decline in catalytic performance.

[0003] Carbon-supported nano-nickel catalysts are typically obtained by impregnating a nickel precursor salt onto the surface of a carbon support followed by annealing and reduction. During this process, uneven impregnation of the precursor within the support can easily lead to metal agglomeration during annealing and reduction, thereby reducing the effective active area and degrading performance. Simultaneously, nickel readily switches between zero and high valence states under intermittent operation, causing structural changes in the catalyst and resulting in decreased long-term stability.

[0004] To address the aforementioned issues, existing technologies typically improve the adsorption uniformity of metal precursors on the support surface by modifying the carbon support through methods such as acid oxidation and heteroatom doping; or by introducing elements capable of forming strong covalent bonds with nickel, thus alleviating the problems of insufficient catalyst activity and susceptibility to oxidation to some extent. However, these single methods have limited effect on improving the overall structural stability and long-term performance of the catalyst, and the processes are cumbersome, making it difficult to fundamentally solve the key problems of nickel-based catalysts.

[0005] Therefore, there is still an urgent need for a technical solution that can effectively improve the distribution of metal components and enhance the structural and chemical stability of carbon-supported nickel-based catalysts while maintaining their high electrocatalytic activity, so as to meet the comprehensive requirements of anion exchange membrane water electrolysis system for the performance and durability of cathode catalysts. Summary of the Invention

[0006] The purpose of this invention is to solve at least one of the problems of the prior art, to develop a carbon-supported nickel-based catalyst with uniform loading, excellent performance and resistance to the influence of oxidation potential under intermittent operating conditions, and to provide a carbon-supported nickel-based core-shell catalyst and its preparation method.

[0007] The first aspect of the present invention provides a carbon-supported nickel-based core-shell catalyst, wherein the surface of the nickel-cobalt alloy core supported on the carbon support is coated with a nickel, cobalt, and molybdenum multimetal oxide intermediate layer with a thickness of 0.2-0.4 nm, and the surface of the intermediate layer is coated with a molybdenum oxide with a thickness of 0.3-3 nm.

[0008] In some specific embodiments, the atomic ratio of nickel to cobalt in the nickel-based core-shell catalyst is 1:0.05-0.3; preferably, the atomic ratio of nickel to cobalt is 1:0.1-0.2.

[0009] In some specific embodiments, the atomic ratio of nickel to molybdenum in the nickel-based core-shell catalyst is 1:0.1-1.5; preferably, the atomic ratio of nickel to molybdenum is 1:0.2-0.5.

[0010] In some specific embodiments, the atomic ratio of the nickel, cobalt, and molybdenum multimetallic oxide intermediate layer varies with the feed ratio of nickel, cobalt, and molybdenum.

[0011] In some specific embodiments, the average particle size of the nickel-cobalt alloy core is 2-6 nm.

[0012] In some specific embodiments, the average particle size of the nickel-based core-shell catalyst is 3-9 nm.

[0013] In some specific embodiments, the core, intermediate layer, and outer shell account for 10-70% of the total mass of the catalyst.

[0014] A second aspect of this invention provides a method for preparing a carbon-supported nickel-based core-shell catalyst, comprising the following steps:

[0015] S1: Dissolve the nickel and cobalt precursor salts in a high-boiling-point solvent, dissolve the molybdenum precursor salt in ultrapure water, and then mix and stir evenly to obtain solution A;

[0016] S2: After mixing the carbon support with solution A evenly, concentrate the solvent at a constant temperature for 20-40 minutes, then heat up to evaporate the solvent and anneal it under a reducing atmosphere to obtain a carbon-supported nickel-based core-shell catalyst.

[0017] In some specific embodiments, the metal precursor salt in step S1 is one or more of nickel nitrate hexahydrate, nickel chloride hexahydrate, nickel acetate tetrahydrate, cobalt nitrate hexahydrate, cobalt chloride hexahydrate, cobalt acetate tetrahydrate, ammonium molybdate, and ammonium paramolybdate.

[0018] In some specific embodiments, the volume ratio of ultrapure water to high-boiling-point organic solvent in step S1 is (1:9)-(9:1); preferably, the volume ratio is (3:7)-(5:5).

[0019] In some specific embodiments, the high-boiling-point organic solvent in step S1 is one or more of glycerol, 1,4-butanediol, ethylene glycol, N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide.

[0020] In some specific embodiments, the concentration of the metal precursor salt solution in step S1 is 0.01-0.5 mol / L.

[0021] In some specific embodiments, the carbon support in step S2 includes at least one of graphene, carbon black, and carbon nanotubes.

[0022] In some specific embodiments, the isothermal concentration solvent temperature in step S2 is 80 ℃-100 ℃.

[0023] In some specific embodiments, the temperature for evaporating the solvent in step S2 is 100 ℃-120 ℃.

[0024] In some specific embodiments, the reducing atmosphere in step S2 is selected from one or more of argon-hydrogen mixture, nitrogen-hydrogen mixture, and hydrogen.

[0025] In some specific embodiments, the volume ratio of inert gas to hydrogen in the reducing atmosphere in step S2 is 9:1 to 19:1.

[0026] In some specific embodiments, the annealing temperature in step S2 is 350 ℃-500 ℃.

[0027] In some specific embodiments, the annealing process in step S2 lasts for 1-6 hours.

[0028] A third aspect of the present invention is to provide the application of a carbon-supported nickel-based core-shell catalyst in hydrogen production by anion exchange membrane water electrolysis.

[0029] The present invention has the following advantages and beneficial effects:

[0030] This invention utilizes a two-step solvent evaporation process, adjusting the solvent composition and ratio of a metal salt impregnation solution. The first step involves low-temperature solvent concentration, gradually evaporating low-boiling-point ultrapure water while retaining high-boiling-point organic solvents. Since molybdates are far less soluble in these solvents than in water, they gradually precipitate as the solvent concentrates, providing nucleation sites for subsequent nickel and cobalt salt precipitation. By controlling the volume ratio of ultrapure water to high-boiling-point organic solvent within the range of (3:7)-(5:5), a homogeneous core-shell structure precursor of nickel, cobalt, and molybdenum is initially obtained. The second step involves evaporating the remaining organic solvent. Due to its high boiling point and viscosity, slow evaporation is achieved, allowing the core-shell structure precursor to be uniformly adsorbed onto a carbon support. Compared to other core-shell structure synthesis methods, such as template methods, chemical vapor deposition, and hydrothermal / solvothermal methods, the synthesis method of this invention produces core-shell structures with better uniformity, controllable thickness, simple operation, low cost, and ease of scalability.

[0031] This invention coats the surface of the intermediate layer with a porous molybdenum oxide shell layer, which not only does not affect the diffusion of reactants but also effectively restricts the oxidation of nickel to high-valence nickel oxides or hydroxides, thus limiting the particle size of nickel and cobalt particles in the catalyst. During annealing and reduction, a nickel, cobalt, molybdenum, and oxygen alloy intermediate layer with a thickness of 0.2-0.4 nm is gradually formed between the core and shell layer interfaces. Compared with the single active site of nano-nickel, the intermediate layer provides a large number of reaction sites with high intrinsic activity. Therefore, this core-shell structure ensures both the stability of the catalyst and high catalytic activity. Attached Figure Description

[0032] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0033] Figure 1 The image shows the XRD pattern of the catalyst prepared in Example 1.

[0034] Figure 2 This is a TEM image of the catalyst prepared in Example 1.

[0035] Figure 3 The images show the XRD patterns of the catalysts prepared in Example 1 and Comparative Example 1.

[0036] Figure 4 The image shows a comparison of the LSV curves of the catalysts prepared in Example 1 and Comparative Example 1.

[0037] Figure 5 This is a comparison of the chronopotential curves of the catalysts prepared in Example 1 and Comparative Example 1.

[0038] Figure 6 The images show the XRD patterns of the catalysts prepared in Example 2 and Comparative Example 2.

[0039] Figure 7This is a TEM image of the catalyst prepared in Example 2.

[0040] Figure 8 The image shows a TEM image of the catalyst prepared in Comparative Example 2.

[0041] Figure 9 This is a comparison of the LSV curves of the catalysts prepared in Example 2 and Comparative Example 2. Detailed Implementation

[0042] The technical solution of the present invention will be further illustrated below through specific embodiments.

[0043] Those skilled in the art will understand that the embodiments described are merely illustrative of the invention and should not be construed as limiting the invention.

[0044] Example 1:

[0045] (1) Weigh 1061.72 mg of nickel nitrate hexahydrate and 106.26 mg of cobalt nitrate hexahydrate and dissolve them in 15 mL of 1,4-butanediol; dissolve 214.71 mg of ammonium molybdate in 5 mL of ultrapure water, then mix the two together and stir for 10 min to obtain solution A.

[0046] (2) Weigh 500 mg of carbon black and place it in solution A. After stirring evenly, concentrate the solvent at 100 °C for 30 minutes. Then, raise the temperature to 120 °C at a rate of 5 °C / min. After evaporating the solvent, the precursor B is obtained.

[0047] (3) Precursor B was placed in a tube furnace and heated to 500 °C at a rate of 5 °C / min in an argon-hydrogen mixture of 5 Vol% (hydrogen percentage, the same in the following examples). The mixture was held at 500 °C for 1 h and then naturally cooled to room temperature to obtain a carbon-supported nickel-based core-shell catalyst with a nickel-to-carbon loading of 30%, a surface containing 2 nm thick molybdenum oxide, a nickel-cobalt-molybdenum atomic ratio of 1:0.1:0.3, and an average particle size of 4 nm.

[0048] Example 2:

[0049] (1) Weigh 867.84 mg of nickel chloride hexahydrate and 43.43 mg of cobalt chloride hexahydrate and dissolve them in 18 mL of glycerol; dissolve 322.28 mg of ammonium molybdate in 6 mL of ultrapure water, then mix the two together and stir for 15 min to obtain solution A.

[0050] (2) Weigh 500 mg of carbon black and place it in solution A. After stirring evenly, concentrate the solvent at 80 °C for 30 minutes. Then, raise the temperature to 100 °C at a rate of 5 °C / min. After evaporating the solvent, the precursor B is obtained.

[0051] (3) Precursor B was placed in a tube furnace and heated to 400 °C at a rate of 5 °C / min in a 10 Vol% argon-hydrogen mixture. The temperature was maintained at 400 °C for 2 h and then naturally cooled to room temperature to obtain a carbon-supported nickel-based core-shell catalyst with a nickel-to-carbon loading of 30%, a surface containing 2 nm thick molybdenum oxide, a nickel-cobalt-molybdenum atomic ratio of 1:0.05:0.5, and an average particle size of 4 nm.

[0052] Example 3:

[0053] (1) Weigh 529.99 mg nickel acetate tetrahydrate and 106.09 mg cobalt acetate tetrahydrate and dissolve them in 10 mL ethylene glycol; dissolve 166.98 mg ammonium molybdate in 4 mL ultrapure water, then mix the two together and stir for 10 min to obtain solution A.

[0054] (2) Weigh 500 mg of carbon nanotubes and place them in solution A. After stirring evenly, concentrate the solvent at 90 °C for 30 minutes. Then, raise the temperature to 110 °C at a rate of 5 °C / min. After evaporating the solvent, the precursor B is obtained.

[0055] (3) Precursor B was placed in a tube furnace and heated to 450 °C at a rate of 10 °C / min in a 5 Vol% argon-hydrogen mixture. The temperature was maintained at 450 °C for 1 h and then naturally cooled to room temperature to obtain a carbon-supported nickel-based core-shell catalyst with a nickel-to-carbon loading of 20%, a surface containing 1.2 nm thick molybdenum oxide, a nickel-cobalt-molybdenum atomic ratio of 1:0.2:0.4, and an average particle size of 5 nm.

[0056] Example 4:

[0057] (1) Weigh 529.99 mg nickel acetate tetrahydrate and 92.97 mg cobalt nitrate hexahydrate and dissolve them in 15 mL dimethyl sulfoxide; dissolve 37.59 mg ammonium molybdate in 10 mL ultrapure water, mix the two evenly and stir for 5 min to obtain solution A.

[0058] (2) Weigh 500 mg of carbon black and place it in solution A. After stirring evenly, concentrate the solvent at 100 °C for 30 minutes. Then, raise the temperature to 120 °C at a rate of 5 °C / min. After evaporating the solvent, the precursor B is obtained.

[0059] (3) Precursor B was placed in a tube furnace and heated to 380 °C at a rate of 5 °C / min in a nitrogen-hydrogen mixture of 5 Vol%. The temperature was maintained at 380 °C for 3 h and then naturally cooled to room temperature to obtain a carbon-supported nickel-based core-shell catalyst with a nickel loading of 20% on carbon, a surface containing 0.3 nm thick molybdenum oxide, a nickel-cobalt-molybdenum atomic ratio of 1:0.15:0.1, and an average particle size of 3 nm.

[0060] Example 5:

[0061] (1) Weigh 1651.56 mg of nickel nitrate hexahydrate and 108.11 mg of cobalt chloride hexahydrate and dissolve them in 30 mL of 1,4-butanediol; dissolve 601.64 mg of ammonium molybdate in 15 mL of ultrapure water, mix the two together and stir for 15 min to obtain solution A.

[0062] (2) Weigh 500 mg of carbon black and place it in solution A. After stirring evenly, concentrate the solvent at 110 °C for 30 minutes. Then, raise the temperature to 120 °C at a rate of 5 °C / min. After evaporating the solvent, the precursor B is obtained.

[0063] (3) Precursor B was placed in a tube furnace and heated to 450 °C at a rate of 3 °C / min in a 10 Vol% nitrogen-hydrogen mixture. The temperature was maintained at 450 °C for 2 h and then naturally cooled to room temperature to obtain a carbon-supported nickel-based core-shell catalyst with a nickel-to-carbon loading of 40%, a surface containing 2.3 nm thick molybdenum oxide, a nickel-cobalt-molybdenum atomic ratio of 1:0.15:0.6, and an average particle size of 7 nm.

[0064] Example 6:

[0065] (1) Weigh 706.66 mg of nickel acetate tetrahydrate and 212.18 mg of cobalt acetate tetrahydrate and dissolve them in 18 mL of glycerol; dissolve 835.02 mg of ammonium molybdate in 18 mL of ultrapure water, then mix the two together and stir for 5 min to obtain solution A.

[0066] (2) Weigh 500 mg of carbon black and place it in solution A. After stirring evenly, concentrate the solvent at 80 °C for 30 minutes. Then, raise the temperature to 100 °C at a rate of 5 °C / min. After evaporating the solvent, the precursor B is obtained.

[0067] (3) Precursor B was placed in a tube furnace and heated to 350 °C at a rate of 5 °C / min in a 5 Vol% nitrogen-hydrogen mixture. The temperature was maintained at 350 °C for 6 h and then naturally cooled to room temperature to obtain a carbon-supported nickel-based core-shell catalyst with a nickel-to-carbon loading of 25%, a surface containing 3 nm thick molybdenum oxide, a nickel-cobalt-molybdenum atomic ratio of 1:0.3:1.5, and an average particle size of 5 nm.

[0068] Example 7:

[0069] (1) Weigh 1656.93 mg of nickel chloride hexahydrate and 162.29 mg of cobalt nitrate hexahydrate and dissolve them in 20 mL of N,N-dimethylformamide; dissolve 123.06 mg of ammonium molybdate in 8 mL of ultrapure water, then mix the two together and stir for 10 min to obtain solution A.

[0070] (2) Weigh 500 mg of carbon nanotubes and place them in solution A. After stirring evenly, concentrate the solvent at 90 °C for 30 minutes. Then, raise the temperature to 120 °C at a rate of 5 °C / min. After evaporating the solvent, the precursor B is obtained.

[0071] (3) Precursor B was placed in a tube furnace and heated to 500 °C at a rate of 10 °C / min in a 10 Vol% argon-hydrogen mixture. The temperature was maintained at 500 °C for 2 h and then naturally cooled to room temperature to obtain a carbon-supported nickel-based core-shell catalyst with a nickel-to-carbon loading of 45%, a surface containing 0.4 nm thick molybdenum oxide, a nickel-cobalt-molybdenum atomic ratio of 1:0.08:0.1, and an average particle size of 4 nm.

[0072] Example 8:

[0073] (1) Weigh 2024.96 mg of nickel chloride hexahydrate and 506.71 mg of cobalt chloride hexahydrate and dissolve them in 40 mL of ethylene glycol; dissolve 500.95 mg of ammonium molybdate in 20 mL of ultrapure water, then mix the two together and stir for 20 min to obtain solution A.

[0074] (2) Weigh 500 mg of carbon black and place it in solution A. After stirring evenly, concentrate the solvent at 110 °C for 30 minutes. Then, raise the temperature to 120 °C at a rate of 5 °C / min. After evaporating the solvent, the precursor B is obtained.

[0075] (3) Precursor B was placed in a tube furnace and heated to 450 °C at a rate of 5 °C / min in a 5 Vol% argon-hydrogen mixture. The temperature was maintained at 450 °C for 3 h and then naturally cooled to room temperature to obtain a carbon-supported nickel-based core-shell catalyst with a nickel-to-carbon loading of 50%, a surface containing 1.2 nm thick molybdenum oxide, a nickel-cobalt-molybdenum atomic ratio of 1:0.25:0.1, and an average particle size of 5 nm.

[0076] Example 9:

[0077] (1) Weigh 1413.24 mg nickel acetate tetrahydrate and 395.71 mg cobalt acetate tetrahydrate and dissolve them in 30 mL N,N-dimethylacetamide; dissolve 222.44 mg ammonium molybdate in 21 mL ultrapure water, mix the two evenly and stir for 10 min to obtain solution A.

[0078] (2) Weigh 500 mg of carbon black and place it in solution A. After stirring evenly, concentrate the solvent at 100 °C for 30 minutes. Then, raise the temperature to 110 °C at a rate of 5 °C / min. After evaporating the solvent, the precursor B is obtained.

[0079] (3) Precursor B was placed in a tube furnace and heated to 400 °C at a rate of 2 °C / min in a 5 Vol% argon-hydrogen mixture. The temperature was maintained at 400 °C for 5 h and then naturally cooled to room temperature to obtain a carbon-supported nickel-based core-shell catalyst with a nickel-to-carbon loading of 40%, a surface containing 0.6 nm thick molybdenum oxide, a nickel-cobalt-molybdenum atomic ratio of 1:0.28:0.2, and an average particle size of 4 nm.

[0080] Example 10:

[0081] (1) Weigh 235.55 mg nickel acetate tetrahydrate and 82.64 mg cobalt nitrate hexahydrate and dissolve them in 10 mL glycerol; dissolve 116.97 mg ammonium molybdate in 5 mL ultrapure water, then mix the two together and stir for 5 min to obtain solution A.

[0082] (2) Weigh 500 mg of carbon black and place it in solution A. After stirring evenly, concentrate the solvent at 90 °C for 30 minutes. Then, raise the temperature to 120 °C at a rate of 5 °C / min. After evaporating the solvent, the precursor B is obtained.

[0083] (3) Precursor B was placed in a tube furnace and heated to 350 °C at a rate of 5 °C / min in a 10 Vol% argon-hydrogen mixture. The temperature was maintained at 350 °C for 6 h and then naturally cooled to room temperature to obtain a carbon-supported nickel-based core-shell catalyst with a nickel-to-carbon loading of 10%, a surface containing 0.3 nm thick molybdenum oxide, a nickel-cobalt-molybdenum atomic ratio of 1:0.3:0.7, and an average particle size of 2 nm.

[0084] Comparative Example 1:

[0085] The difference between this comparative example and Example 1 is that no cobalt salt or molybdate is added.

[0086] Comparative Example 2:

[0087] The difference between this comparative example and Example 2 is that no organic solvent is used; the metal precursor salt is directly dissolved in 20 mL of ultrapure water.

[0088] Comparative Example 3:

[0089] The difference between this comparative example and Example 1 is that molybdate is not added.

[0090] Comparative Example 4:

[0091] The difference between this comparative example and Example 1 is that the solvent was changed to 15 mL of 1,4-butanediol and 1 mL of ultrapure water.

[0092] Comparative Example 5:

[0093] The difference between this comparative example and Example 1 is that the solvent was changed to 1 mL of 1,4-butanediol and 15 mL of ultrapure water.

[0094] Comparative Example 6:

[0095] The difference between this comparative example and Example 1 is that the amount of cobalt salt added is increased, so that the nickel-cobalt atomic ratio is 1:1.

[0096] Comparative Example 7:

[0097] The difference between this comparative example and Example 1 is that the amount of molybdenum salt added is increased, so that the nickel-molybdenum atomic ratio is 1:2.

[0098] Comparative Example 8:

[0099] The difference between this comparative example and Example 1 is that the solvent is directly evaporated in one step.

[0100] Solvent volume ratios for all examples and comparative examples, the number of well-coated core-shell structures observed by transmission electron microscopy (TEM), and the corresponding 10 mA / cm² values. 2 The results of overpotential and Tafel slope are shown in Table 1. When the volume ratio of ultrapure water to high-boiling organic solvent is controlled within the range of (3:7) to (5:5), the core-shell structure has a better coating effect and its performance is better than that of catalysts without a core-shell structure.

[0101] The catalysts prepared in Example 1 and Comparative Example 1, and Example 2 and Comparative Example 2 were subjected to X-ray diffraction (XRD) and transmission electron microscopy (TEM) tests. The test results are as follows:

[0102] Figure 1 The image shows the XRD pattern of the catalyst prepared in Example 1. As can be seen from the image, the sample has diffraction peaks characteristic of the face-centered cubic (FCC) structure of nickel and amorphous molybdenum oxide.

[0103] Figure 2 The image shows a TEM image of the catalyst prepared in Example 1. As can be seen from the image, the sample surface has a molybdenum oxide layer of about 2 nm.

[0104] Figure 3 The XRD patterns of the catalysts prepared in Example 1 and Comparative Example 1 show that the average particle size of pure nickel in Comparative Example 1 is larger than that in Example 1, indicating that the molybdenum oxide layer has a significant limiting effect on the particle size of nano-nickel cobalt.

[0105] Figure 6 The XRD patterns of the catalysts prepared in Example 2 and Comparative Example 2 show that the average particle size of Comparative Example 2, which did not use a high-boiling-point organic solvent, is larger than that of Example 2.

[0106] Figure 7The image shows a TEM image of the catalyst prepared in Example 2, which shows that the nickel-cobalt particles are uniformly dispersed on the support.

[0107] Figure 8 The image shows a TEM image of the catalyst prepared in Comparative Example 2. Since Comparative Example 2 did not use a high-boiling-point organic solvent, the nickel-cobalt nanoparticles partially agglomerated on the carbon support, and the core-shell structure was barely observable.

[0108] The catalysts of Example 1 and Comparative Example 1, and Example 2 and Comparative Example 2 were tested for their hydrogen evolution reaction (HER) catalytic activity under a three-electrode test system. The specific test conditions are as follows:

[0109] 1. The working electrode is a glassy carbon electrode, the counter electrode is a graphite electrode, and the reference electrode is an Hg / HgO electrode.

[0110] 2. The test environment was a nitrogen-saturated 1 mol / L KOH solution, the scan potential range was -1.5 to -0.8 V, the scan rate was 5 mV / s, and the working electrode rotation speed was 1600 rpm.

[0111] 3. The catalyst slurry composition includes 2 mg of catalyst, 790 μL of isopropanol, 200 μL of ultrapure water, and 10 μL of Nafion solution. All components are placed in a 2 mL glass vial and sonicated for 30 min until the slurry is homogeneous.

[0112] 4. Take 10 μL of catalyst slurry and drop it onto the glassy carbon electrode in two batches. After drying under an infrared lamp, perform HER activity testing.

[0113] The catalysts in Example 1 and Comparative Example 1 were subjected to intermittent operation simulation tests under a three-electrode test system. The specific test conditions are as follows:

[0114] 1. The working electrode is a catalyst sprayed on carbon paper, the counter electrode is a graphite electrode, and the reference electrode is a mercury / mercury oxide electrode.

[0115] 2. The test environment was a nitrogen-saturated 1 mol / L KOH solution. The test technique used was the chronopotential method, with a constant starting pressure of 100 mA / cm². 2 The current density is operated for 1 hour, followed by a 1-hour shutdown. One start-up and one stop constitutes one set of simulation tests, which are repeated ten times.

[0116] Comparison of LSV curves of the catalyst prepared in Example 1 and Comparative Example 1 ( Figure 4 As can be seen, Example 1 has a capacity of 10 mA / cm². 2 The overpotential of -119 mV is less than that of Comparative Example 1 (-181 mV), indicating that the HER catalytic activity of the catalyst in Example 1 is superior to that of the pure nickel catalyst.

[0117] The chronopotential curves of Example 1 and Comparative Example 1 ( Figure 5 As can be seen, the performance of the catalyst in Example 1 did not decline significantly after 10 start-stop cycles, indicating that the molybdenum oxide layer has a significant effect on reducing the oxidation state fluctuation of nickel.

[0118] A comparison of the LSV curves of the catalyst prepared in Example 2 and Comparative Example 2 (Figure 2) Figure 9 As can be seen, Example 2 has a capacity of 10 mA / cm². 2 The overpotential of -138 mV is less than that of Comparative Example 2 (-192 mV), indicating that the HER catalytic activity of the catalyst synthesized with a mixed solvent in Example 2 is superior to that of the catalyst synthesized with ultrapure water in Comparative Example 2.

[0119] The above description is only a preferred embodiment of the present invention, and therefore cannot be used to limit the scope of the present invention. All equivalent changes and modifications made in accordance with the scope of the patent and the contents of the specification of the present invention should still fall within the scope of the present invention.

[0120] Table 1. Solvent ratios, coating conditions, and performance parameters for each embodiment and comparative example.

[0121]

[0122] The above description is merely a preferred embodiment of the present invention, and therefore should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made in accordance with the scope of the patent and the contents of the specification should still fall within the scope of the present invention.

Claims

1. A carbon-supported nickel-based core-shell catalyst, characterized in that, The core-shell catalyst supported on a carbon support includes a core, an intermediate layer covering the surface of the core, and an outer shell layer covering the surface of the intermediate layer; wherein the core comprises a nickel-cobalt alloy, the intermediate layer comprises a nickel, cobalt, and molybdenum polymetallic oxide, and the outer shell layer comprises a molybdenum oxide.

2. The carbon-supported nickel-based core-shell catalyst according to claim 1, characterized in that, The nickel-based core-shell catalyst has an atomic ratio of nickel to cobalt of 1:0.05-0.3 and an atomic ratio of nickel to molybdenum of 1:0.1-1.

5.

3. The carbon-supported nickel-based core-shell catalyst according to claim 1, characterized in that, The molybdenum in the molybdenum oxide outer shell has one or more valence states from +4 to +6, and is in a porous amorphous state.

4. The carbon-supported nickel-based core-shell catalyst according to claim 1, characterized in that, The average thickness of the nickel, cobalt, molybdenum, and oxygen intermediate layer is 0.2-0.4 nm; the average particle size of the nickel-cobalt alloy core is 2-6 nm; and the average thickness of the molybdenum oxide outer shell layer is 0.3-3 nm.

5. The carbon-supported nickel-based core-shell catalyst according to claim 1, characterized in that, The core, intermediate layer, and outer shell layer account for 10-70% of the total mass of the catalyst.

6. The application of the carbon-supported nickel-based core-shell catalyst as described in any one of claims 1 to 5 in anion exchange membrane water electrolysis for hydrogen production.

7. A method for preparing a carbon-supported nickel-based core-shell catalyst as described in any one of claims 1 to 5, characterized in that, Includes the following steps: S1: Dissolve the nickel and cobalt precursor salts in a high-boiling-point solvent, dissolve the molybdenum precursor salt in ultrapure water, and then mix and stir evenly to obtain solution A; S2: After mixing the carbon support with solution A evenly, concentrate the solvent at a constant temperature of 80-100℃ for 20-40 minutes, then heat up to evaporate the solvent and anneal it under a reducing atmosphere to obtain a carbon-supported nickel-based core-shell catalyst.

8. The method for preparing the carbon-supported nickel-based core-shell catalyst according to claim 7, characterized in that, In step S1, the volume ratio of ultrapure water to high-boiling-point organic solvent is (1:9)-(9:1); preferably, the volume ratio is (3:7)-(5:5).

9. The method for preparing the carbon-supported nickel-based core-shell catalyst according to claim 7, characterized in that, In step S1, the metal precursor is one or more of nickel nitrate hexahydrate, nickel chloride hexahydrate, nickel acetate tetrahydrate, cobalt nitrate hexahydrate, cobalt chloride hexahydrate, cobalt acetate tetrahydrate, ammonium molybdate, and ammonium paramolybdate; the high-boiling-point organic solvent is one or more of glycerol, 1,4-butanediol, ethylene glycol, N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide.

10. The method for preparing the carbon-supported nickel-based core-shell catalyst according to claim 7, characterized in that, In step S2, during the heating and drying process, the heating rate is 1-5℃ / min, and the temperature is raised to 100-120℃; the annealing process involves heating to 350-500℃ at a rate of 1-10℃ / min, holding for 1-6 hours, and then naturally cooling to room temperature.

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