A nitrogen-doped carbon-coated ternary nanoneedle array material, a preparation method thereof and application thereof in electrolysis of hydrazine hydrate

Abstract

This invention discloses a nitrogen-doped carbon-coated ternary nanoneedle array material, its preparation method, and its application in the electrolysis of hydrazine hydrate, belonging to the field of energy catalysis technology. The material comprises a substrate, a ternary nanoneedle array grown on the substrate surface, and a nitrogen-doped carbon material supported on the ternary nanoneedle array and the substrate surface; the ternary nanoneedles are composed of any three of iron, cobalt, copper, nickel, and manganese. This invention proposes an NC-supported ternary nanoneedle array, where NC and the ternary nanoneedle array synergistically achieve enrichment of active sites and enhancement of intrinsic activity, effectively improving the conductivity of the ternary nanoneedle array. For hydrogen evolution reaction and oxygen evolution reaction, electrons can be rapidly transferred between the catalyst surface and reaction intermediates, thereby accelerating the reaction rate. Simultaneously, this coating structure, by adjusting the adsorption energy, makes it easier for water molecules to be adsorbed and activated on the catalyst surface, thus promoting HzOR catalytic activity.

Description

Technical Field

[0001] This invention belongs to the field of energy catalysis technology, specifically relating to a nitrogen-doped carbon-coated ternary nanoneedle array material, its preparation method, and its application in the electrolysis of hydrazine hydrate. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Hydrogen energy, with its high energy density and clean, pollution-free characteristics, has become an ideal alternative to traditional fossil fuels. Among the many hydrogen production pathways, electrocatalytic water splitting is currently the ideal way to obtain hydrogen energy and alleviate the energy crisis. However, the oxygen evolution reaction (OER) at the anode during water electrolysis is kinetically slow, severely limiting the overall efficiency of hydrogen production. Small-molecule electro-oxidation reactions, such as the hydrazine hydrate electro-oxidation reaction (HzOR), can be coupled more efficiently with the hydrogen evolution reaction (HER) at the cathode, significantly improving hydrogen evolution efficiency. Therefore, developing low-cost, high-efficiency small-molecule electro-oxidation catalysts is of great significance.

[0004] Noble metals and their alloys or compounds are generally considered to be active electrocatalysts for electrocatalytic HzOR. However, the high cost and poor stability of these noble metal-based catalysts limit their application in HzOR. Currently, developing highly abundant and active transition metal oxides, hydroxides, phosphides, and selenides as HzOR electrocatalysts has become a research hotspot. Although various non-noble metal-based catalysts have been developed, and three-dimensional transition metals such as Ni and Co have shown good electrocatalytic activity for HzOR, even surpassing noble metals such as Pt, their application is still hindered by the large overpotentials and slow reaction kinetics of most catalysts, which reduce the maximum current density. Therefore, designing and constructing advanced non-noble metal catalysts remains a key issue that urgently needs to be addressed in advancing the practical application of direct hydrazine fuel cell technology. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a nitrogen-doped carbon-coated ternary nanoneedle array material, its preparation method, and its application in the electrolysis of hydrazine hydrate. The nitrogen-doped carbon-coated ternary nanoneedle array material provided by the present invention achieves enrichment of active sites and enhancement of intrinsic activity, thereby improving the catalytic activity and electrode conductivity of the catalyst.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] In a first aspect, the present invention provides a nitrogen-doped carbon-coated ternary nanoneedle array material, comprising a substrate, a ternary nanoneedle array grown on the surface of the substrate, and a nitrogen-doped carbon material loaded on the ternary nanoneedle array and the surface of the substrate.

[0008] The ternary nanoneedles are composed of any three of the following: iron, cobalt, copper, nickel, and manganese.

[0009] In some specific embodiments of the present invention, the substrate includes, but is not limited to, any one of cobalt foam, nickel foam, copper foam, manganese foam, and iron foam.

[0010] In some specific embodiments of the present invention, the substrate is copper foam, and the ternary nanoneedles are composed of iron, cobalt and copper; preferably, the molar ratio of iron to cobalt in the ternary nanoneedles is 3:7.

[0011] In some specific embodiments of the present invention, the ternary nanoneedles are composed of iron, cobalt, and nickel; more preferably, the molar ratio of iron, cobalt, and nickel in the ternary nanoneedles is 0.7-0.8:1:1. In some specific embodiments of the present invention, the molar ratio of iron, cobalt, and nickel in the ternary nanoneedles is preferably 0.75:1:1.

[0012] In some specific embodiments of the present invention, the ternary nanoneedles are composed of copper, cobalt, and nickel; more preferably, the molar ratio of copper, cobalt, and nickel in the ternary nanoneedles is (0.9-1.1):(0.9-1.1):(0.9-1.1). In some specific embodiments of the present invention, the molar ratio of copper, cobalt, and nickel in the ternary nanoneedles is preferably 1:1:1.

[0013] In some specific embodiments of the present invention, the ternary nanoneedles are composed of iron, cobalt, and manganese; more preferably, the molar ratio of iron, cobalt, and manganese in the ternary nanoneedles is (0.9-1.1):(0.9-1.1):(0.9-1.1). In some specific embodiments of the present invention, the molar ratio of iron, cobalt, and manganese in the ternary nanoneedles is preferably 1:1:1.

[0014] In some specific embodiments of the present invention, the ternary nanoneedles are composed of nickel, cobalt, and manganese; more preferably, the molar ratio of nickel, cobalt, and manganese in the ternary nanoneedles is (0.9-1.1):(0.9-1.1):(0.9-1.1). In some specific embodiments of the present invention, the molar ratio of nickel, cobalt, and manganese in the ternary nanoneedles is preferably 1:1:1.

[0015] The present invention does not impose any special limitation on the structure of the ternary nanoneedles in the nitrogen-doped carbon-coated ternary nanoneedle array material, and can be a structure well known to those skilled in the art, such as a trimetallic alloy.

[0016] In some specific embodiments of the present invention, the size of the ternary nanoneedles is 3-5 μm.

[0017] The present invention does not have any particular limitation on the loading method of nitrogen-doped carbon material in the nitrogen-doped carbon-coated ternary nanoneedle array material, and can be a loading method known to those skilled in the art, such as semi-coating, full-coating, or doping.

[0018] In some specific embodiments of the present invention, the loading method is preferably full coverage.

[0019] A ternary nanoneedle array, formed by three metal dopings, is then coated with nitrogen-doped carbon material. The ternary nanoneedle array and the nitrogen-doped carbon material synergistically enrich active sites and enhance intrinsic activity, effectively improving the conductivity of the ternary nanoneedle array. For the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), electrons can be rapidly transferred between the catalyst surface and reaction intermediates, thereby accelerating the reaction rate. Simultaneously, this coating structure, by modulating the adsorption energy, facilitates the adsorption and activation of water molecules on the catalyst surface, thus promoting the catalytic activity of HzOR.

[0020] A second aspect of the present invention provides a method for preparing the above-mentioned nitrogen-doped carbon-coated ternary nanoneedle array material, comprising:

[0021] Ternary nanoneedles were grown in situ on a substrate using a hydrothermal reaction to obtain a ternary nanoneedle array;

[0022] The ternary nanoneedle array was immersed in an aqueous solution of 2-methylimidazol, then removed, washed, and dried to obtain the ternary nanoneedle-ZIF precursor.

[0023] The ternary nanoneedle-ZIF precursor was pyrolyzed to obtain a nitrogen-doped carbon-coated ternary nanoneedle array material.

[0024] It should be noted that the electrocatalytic performance of the nitrogen-doped carbon-coated ternary nanoneedle array material prepared by the above-described preparation method of this invention is superior to that prepared by other methods. It should be pointed out that those skilled in the art can adjust the order of the preparation process, such as preparing the nitrogen-doped carbon material first and then coating the ternary nanoneedle array. That is, those skilled in the art can make several improvements and modifications to this invention without departing from the principle of this invention, and these improvements and modifications also fall within the protection scope of the claims of this invention.

[0025] In some specific embodiments of the present invention, the substrate is pretreated before use;

[0026] The pretreatment includes the steps of sequentially sonicating in an alcohol solution, water, an acid solution, and water.

[0027] It should be noted that the present invention does not impose any limitation on the ultrasonication time, as long as it is sufficient to remove impurities. For example, when ultrasonicating in an alcohol solution, the ultrasonication time can be 5-10 minutes to fully remove organic matter from the substrate surface. When ultrasonicating in an acid solution, the ultrasonication time can be 5-10 minutes to fully remove the oxide layer from the substrate surface.

[0028] Preferably, the acid includes, but is not limited to, one or more of hydrochloric acid, sulfuric acid, and nitric acid. When sonicating in an acid solution, the acid concentration needs to be controlled to avoid acid etching of the substrate and affecting the experimental results. Therefore, it is preferable to use a low-concentration acid solution for sonication, such as a 1% dilute hydrochloric acid solution.

[0029] In some specific embodiments of the present invention, the substrate includes, but is not limited to, any one of cobalt foam, nickel foam, copper foam, manganese foam, and iron foam.

[0030] In some specific embodiments of the present invention, the hydrothermal reaction includes: preparing a solution containing iron ions, cobalt ions, copper ions, nickel ions and / or manganese ions, then adding urea and ammonium fluoride, adding a substrate, and heating at 110-130°C for 5-7 hours to obtain a ternary nanoneedle array.

[0031] Preferably, a solution containing iron ions and cobalt ions is prepared, and then urea and ammonium fluoride are added. After adding a copper foam substrate, the solution is heated at 110-130°C for 5-7 hours to obtain a ternary nanoneedle array. The ratio of metal ions, urea and ammonium fluoride is 1-1.5 mmol: 280-320 mg: 90-95 mg.

[0032] Preferably, the total metal content in the solution is 1-1.5 mmol, the urea concentration is 13-17 mg / mL, and the ammonium fluoride concentration is 4-5 mg / mL. The addition of urea and ammonium fluoride can promote the hydrothermal reaction, regulate the stability of the reaction, and facilitate the formation of a ternary nanoneedle array.

[0033] In some specific embodiments of the present invention, the volume ratio of alcohol to water in the 2-methylimidazol aqueous solution is 0.9-1.1:0.9-1.1, preferably 1:1, and the concentration of 2-methylimidazol is 0.08-0.12 g / mL.

[0034] In some specific embodiments of the present invention, the ratio of the amount of the ternary nanoneedle array to the 2-methylimidazol aqueous solution is such that one ternary nanoneedle array is placed in 20-40 mL of 2-methylimidazol aqueous solution; the size of the ternary nanoneedle array is 1×(3-4) cm.

[0035] In some specific embodiments of the present invention, the pyrolysis conditions are as follows: heating to 400-500°C at a heating rate of 4-6°C / min, and holding at that temperature for 1.5-2.5 hours. Preferably, heating to 450°C at a heating rate of 5°C / min, and holding at that temperature for 2 hours.

[0036] A third aspect of the present invention provides the application of the nitrogen-doped carbon-coated ternary nanoneedle array material described above or the nitrogen-doped carbon-coated ternary nanoneedle array material prepared by the above preparation method as a catalyst in the electrolysis of hydrazine hydrate.

[0037] The present invention discloses a method for electrolyzing hydrazine hydrate, characterized in that the above-mentioned nitrogen-doped carbon-coated ternary nanoneedle array material or the nitrogen-doped carbon-coated ternary nanoneedle array material prepared by the above-mentioned preparation method is used as an electrocatalyst.

[0038] The beneficial effects of this invention are as follows:

[0039] This invention provides a nitrogen-doped carbon-coated ternary nanoneedle array material, which can be used as a catalyst for the electrocatalytic hydrazine electrooxidation reaction (HzOR). The nitrogen-doped carbon (NC) support, derived from the zeolite imidazolium ester (ZIF) framework, is a highly conductive porous support that not only ensures rapid charge transfer and reduces nitrogen accumulation but also achieves high exposure of the anchored nanocatalyst. This invention proposes an NC-supported ternary nanoneedle array, where the NC and the ternary nanoneedle array synergistically enrich active sites and enhance intrinsic activity, effectively improving the conductivity of the ternary nanoneedle array. For the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), electrons can be rapidly transferred between the catalyst surface and reaction intermediates, thereby accelerating the reaction rate. Simultaneously, this coating structure, by regulating the adsorption energy, makes it easier for water molecules to adsorb and activate on the catalyst surface, thus promoting the catalytic activity of HzOR.

[0040] The nitrogen-doped carbon-coated ternary nanoneedle array material provided by this invention possesses abundant active sites. These sites can effectively adsorb and activate reactant molecules during the electrolysis of hydrazine hydrate, significantly reducing the onset potential of the hydrazine hydrate oxidation reaction (HzOR). Verification has shown that compared to uncoated nanosheet arrays, its onset potential can be reduced by 50-100 mV, making the reaction easier to initiate. Attached Figure Description

[0041] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0042] Figure 1The XRD patterns of FeCoCu-LDH (A), FeCoCu-ZIF (B), and FeCoCu-NC (C) prepared in Example 1 of this invention are shown.

[0043] Figure 2 SEM images of FeCoCu-LDH (A) and FeCoCu-NC (B) prepared in Example 1 of this invention;

[0044] Figure 3 These are electrochemical performance test graphs of the materials prepared in Examples 1-6 and Comparative Example 1 of this invention;

[0045] Figure 4 The graphs show the electrochemical performance test results of the materials prepared in Comparative Examples 2-8 of this invention. Detailed Implementation

[0046] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0047] Example 1

[0048] A method for preparing a nitrogen-doped carbon-coated ternary nanoneedle array material FeCoCu-NC includes the following steps:

[0049] Pretreatment of copper foam: Place copper foam (1×3.7cm) in a beaker, add ethanol, and sonicate for 5 minutes to remove organic matter from the surface of the copper foam. Sonicate with distilled water for one minute. Then sonicate with 1% dilute hydrochloric acid solution for 5 minutes to remove the oxide layer on the surface. Finally, sonicate and wash three times with deionized water.

[0050] Hydrothermal Synthesis of FeCoCu-LDH: 0.39 mmol of Fe(NO3)3·9H2O and 0.91 mmol of Co(NO3)2·6H2O, with a total metal content of 1.3 mmol, were weighed and dissolved in 20 mL of deionized water. The solution was stirred at room temperature to form solution A. 300 mg of urea and 93 mg of ammonium fluoride were then added to solution A and stirred at room temperature to form solution B. Copper foam was placed in a 50 mL high-pressure reactor lined with polytetrafluoroethylene (PTFE). Solution B was then transferred to the liner and sealed. The reactor was heated at 120 °C for 6 hours and then cooled to room temperature to obtain catalyst-loaded copper foam. The catalyst-loaded copper foam was washed three times with deionized water and ethanol and then vacuum-dried at 40 °C for 12 hours to obtain a uniform ternary FeCoCu nanosheet array.

[0051] Preparation of FeCoCu-ZIF: 15 mL of ethanol and water were measured and stirred at room temperature to form a mixed solution. 3.28 g of 2-methylimidazole was dissolved in the mixed solution of ethanol and water. A ternary FeCoCu nanosheet array (1×3.7 cm) was placed in 30 mL of the 2-methylimidazole ethanol-water mixed solution and left to stand for 3 h. After standing, it was taken out and washed three times with methanol. It was then vacuum dried at 40 °C for 12 h to obtain the ternary nanoneedle-ZIF precursor (abbreviated as FeCoCu-ZIF).

[0052] Preparation of FeCoCu-NC: The ternary nanoneedle-ZIF precursor FeCoCu-ZIF was heated to 450℃ in a tube furnace at a heating rate of 5℃ / min and held for 2h. After natural cooling to room temperature, the final product, nitrogen-doped carbon-coated ternary nanoneedle array material (referred to as FeCoCu-NC), was obtained.

[0053] Example 2

[0054] A method for preparing a nitrogen-doped carbon-coated ternary alloy material FeCoNi-NC includes the following steps:

[0055] Synthesis of nitrogen-doped carbon material support: 4.88 g of phenol and 1.04 g of 20% (v / v) NaOH solution were placed in a reactor and stirred until homogeneous. Then, 8.4 g of 37% (v / v) formaldehyde solution was added, and the reaction was carried out at 70 °C for 1 h. After the reaction mixture cooled to room temperature, the pH was adjusted to approximately 7.0-7.5 using 0.6 mol / L HCl solution. The mixture was then rotary evaporated for 2 h, and 15 g of anhydrous ethanol solution was added to obtain a 20 wt% phenolic resin ethanol solution, which was refrigerated for later use. Anhydrous ethanol and deionized water were added to the reactor at a mass ratio of 3:2. At a reaction temperature of 50 °C, 10 g of the above phenolic resin ethanol solution was added, followed by 2 g of dicyandiamide, and stirred until completely dissolved. 200 μL of concentrated nitric acid was added to the above solution to adjust the pH to acidic, and the mixture was stirred at 50 °C and 400 r / min for 0.5 h. The stirred solution was placed in an oven at 50°C for 6 hours, and then reacted at 100°C for 24 hours. After the sample cooled, it was placed in a tube furnace. Nitrogen gas was first introduced into the tube furnace at room temperature for 30 minutes, and then the temperature was increased to 800°C at a rate of 3°C / min and calcined at 800°C for 5 hours to obtain a nitrogen-doped carbon material support, which was ready for use.

[0056] Synthesis of nitrogen-doped carbon-coated FeCoNi alloy catalyst: 1.0 g of nitrogen-doped carbon material support was vacuum dried at 110 °C for 12 h to ensure complete dehydration, and then cooled for later use. 0.33 g of cobalt nitrate, 0.33 g of nickel nitrate, and 0.33 g of ferric nitrate were completely dissolved in 2 mL of water by ultrasonication to prepare an impregnation solution. The impregnation solution was then ultrasonically vibrated onto the surface of the dehydrated nitrogen-doped carbon material support, and then dried in a vacuum drying oven at 100 °C for 5 h. After drying, the mixture was cooled to room temperature, ground into powder, and calcined in a tube furnace under nitrogen atmosphere at a rate of 3 °C / min to 800 °C for 6 h. After cooling, the nitrogen-doped carbon-coated ternary alloy material FeCoNi-NC was finally obtained.

[0057] Post-processing: The prepared nitrogen-doped carbon-coated ternary nanoneedle array material FeCoNi-NC was ground to a particle size of 100 nm, then added to a 0.1 mol / L nitric acid solution, stirred at 60 °C for 6 h, filtered, washed with deionized water until neutral, and dried in a vacuum oven at 70 °C for storage.

[0058] Example 3

[0059] A method for preparing a nitrogen-doped carbon-coated ternary alloy material CuCoNi-NC includes the following steps:

[0060] Synthesis of ZIF precursor: 0.25 mmol copper nitrate, 0.25 mmol cobalt nitrate and 0.25 mmol nickel nitrate were dissolved in 50 mL methanol and stirred until a mixed solution was formed.

[0061] To prepare a dimethylimidazole methanol solution: Dissolve 2 mmol of dimethylimidazole in 40 mL of methanol and stir until completely dissolved.

[0062] Mixed reaction: The two solutions were mixed and stirred at room temperature for 4 hours, then centrifuged, the precipitate was washed three times with methanol, and dried at 80°C overnight to obtain the CuCoNi-ZIF precursor.

[0063] Carbonization treatment: The obtained CuCoNi-ZIF precursor was ground into powder. The powder was placed in a tube furnace and heated to 800℃ at a heating rate of 5℃ / min under a nitrogen atmosphere, and calcined at this temperature for 4 hours. After calcination, it was naturally cooled to room temperature to obtain nitrogen-doped carbon-coated ternary alloy material (CuCoNi-NC for short).

[0064] Post-treatment: The prepared CuCoNi-NC material was soaked in an appropriate amount of dilute acid (0.1 mol / L hydrochloric acid) for 2 hours to remove any impurities that may exist on the surface. Then it was washed with deionized water until neutral and dried at 80°C.

[0065] Example 4

[0066] A method for preparing a nitrogen-doped carbon-coated ternary alloy material FeCoMn-NC includes the following steps:

[0067] Preparation of precursor solutions: Metal salt solutions: Weigh 0.25 mmol ferric nitrate, 0.25 mmol cobalt nitrate, and 0.25 mmol manganese nitrate, respectively, and dissolve them in 50 mL of methanol. Stir until homogeneous to form a mixed metal salt solution. Weigh 2 mmol of dimethylimidazole and dissolve it in 40 mL of methanol. Stir until completely dissolved. Mix the two solutions and stir at room temperature for 2-4 hours to form a homogeneous precursor solution.

[0068] Precipitation and washing: The precursor solution was allowed to stand at room temperature to allow the metal salt and organic ligand to react fully and form a precipitate. The precipitate was separated by centrifugation at 10,000 rpm for 15 minutes. The precipitate was washed with methanol three times to remove surface impurities.

[0069] Drying and grinding: The washed precipitate was dried overnight at 80°C to obtain a dried precursor powder. The dried precursor powder was then ground into a fine powder with a particle size of 100 nm for subsequent carbonization treatment.

[0070] Carbonization treatment: The ground precursor powder was placed in a tube furnace and heated to 800°C at a heating rate of 5°C / min under a nitrogen atmosphere, and calcined at this temperature for 4 hours. After calcination, it was naturally cooled to room temperature to obtain FeCoMn-NC material.

[0071] Post-treatment: The prepared FeCoMn-NC material was soaked in an appropriate amount of dilute acid (0.1mol / L hydrochloric acid) for 2 hours to remove any impurities that may exist on the surface. Then it was washed with deionized water until neutral and dried at 80℃.

[0072] Example 5

[0073] A method for preparing a nitrogen-doped carbon-coated ternary nanoneedle array material FeCoMn-NC includes the following steps:

[0074] Pretreatment of manganese foam: Place manganese foam (1×3.7cm) in a beaker, add ethanol, and sonicate for 5 minutes to remove organic matter from the surface of the manganese foam. Sonicate with distilled water for one minute, then sonicate with 1% dilute hydrochloric acid solution for 5 minutes to remove the oxide layer. Finally, wash three times with deionized water using ultrasound to complete the pretreatment. Then dry in a vacuum drying oven at 60℃ for 12 hours.

[0075] Synthesis of NiCoMn-LDH: 0.25 mmol nickel nitrate, 0.25 mmol cobalt nitrate, and 0.25 mmol manganese nitrate were dissolved in 50 mL of deionized water and stirred until homogeneous to form a mixed salt solution. A certain amount of sodium hydroxide was weighed and a 0.25 mol / L alkaline solution was prepared. Under continuous stirring, the mixed salt solution and alkaline solution were simultaneously added dropwise to a reaction vessel containing pretreated manganese foam, controlling the adding rate to maintain the pH of the solution at 10 ± 0.1. After the addition was complete, stirring was continued for 3 h. The reaction mixture was transferred to a hydrothermal reactor and crystallized at 100 °C for 6-8 h. After the reaction was completed, the mixture was naturally cooled to room temperature, washed several times by centrifugation with deionized water and ethanol, and dried overnight at 60-80 °C to obtain the NiCoMn-LDH / manganese foam composite.

[0076] Synthesis of NiCoMn-ZIF: 2 mmol of dimethylimidazole was weighed and dissolved in 40 mL of methanol. The solution was stirred until completely dissolved to obtain a dimethylimidazole methanol solution. The NiCoMn-LDH / foamed manganese complex obtained above was added to another methanol solution containing 0.25 mmol of nickel nitrate, 0.25 mmol of cobalt nitrate, and 0.25 mmol of manganese nitrate, and the mixture was ultrasonically dispersed. The dimethylimidazole methanol solution was slowly added dropwise to the solution containing the NiCoMn-LDH / foamed manganese complex, and the mixture was stirred at room temperature for 24 hours. The mixture was then centrifuged, the precipitate was washed three times with methanol, and dried overnight at 80 °C to obtain the NiCoMn-ZIF / foamed manganese complex.

[0077] Carbonization treatment: The NiCoMn-ZIF / manganese foam composite was placed in a tube furnace and heated to 800℃ at a heating rate of 5℃ / min under a nitrogen atmosphere, and calcined at this temperature for 4 hours. After calcination, it was naturally cooled to room temperature to obtain NiCoMn-NC.

[0078] Post-treatment: The prepared NiCoMn-NC was soaked in an appropriate amount of dilute acid (0.1 mol / L hydrochloric acid) for 2 hours to remove any impurities that may exist on the surface. Then it was washed with deionized water until neutral and dried at 80°C.

[0079] Example 6

[0080] A method for preparing a nitrogen-doped carbon-coated ternary alloy material FeCoCu-NC differs from Example 3 in that nickel nitrate is replaced with iron nitrate, while the remaining steps are the same as in Example 3.

[0081] Comparative Example 1

[0082] A method for preparing nitrogen-doped carbon-coated elemental iron material Fe-NC includes the following steps:

[0083] Weigh out 2.42g of ferric nitrate Fe(NO3)3·9H2O as the iron source. Weigh out 3.0g of melamine as both the nitrogen and carbon source. Weigh out 1.5g of glucose as an additional carbon source.

[0084] Dissolve the weighed ferric nitrate in 50 mL of deionized water and stir at 300 rpm for 15 min on a magnetic stirrer until completely dissolved, forming a transparent solution. Add melamine to the ferric nitrate solution and stir at 500 rpm for 30 min to ensure thorough mixing. Add glucose to the mixture and continue stirring for 30 min to ensure uniform dispersion of the three substances, forming a homogeneous solution. Transfer the resulting solution to an evaporating dish and evaporate the solvent continuously by stirring in an 80°C water bath until a viscous gel-like substance is formed, maintaining a stirring speed of 200 rpm throughout the process. Transfer the gel-like substance to an oven and dry at 100°C for 12 hours to obtain a dried precursor powder.

[0085] The precursor powder was transferred to a ceramic boat and placed in the isothermal zone of a tube furnace. High-purity nitrogen gas was introduced into the tube furnace at a flow rate of 50 mL / min, and the furnace was heated to 900 °C at a heating rate of 5 °C / min, and maintained at this temperature for 3 hours to allow the precursor to undergo complete pyrolysis. After the reaction was completed, the power to the tube furnace was turned off, and the sample was allowed to cool naturally to room temperature under a nitrogen atmosphere to obtain black Fe-NC material.

[0086] Comparative Example 2

[0087] A method for preparing a nitrogen-doped carbon-coated cobalt elemental material Co-NC differs from Comparative Example 1 in that the iron source is replaced with a cobalt source - cobalt nitrate Co(NO3)2·6H2O.

[0088] Comparative Example 3

[0089] A method for preparing a nitrogen-doped carbon-coated cobalt elemental material Co-NC differs from Comparative Example 1 in that the iron source is replaced with a copper source - copper nitrate Cu(NO3)2.

[0090] Comparative Example 4

[0091] A method for preparing a nitrogen-doped carbon-coated binary nanosheet material FeCo-NC differs from Example 1 in that copper foam is replaced with cobalt foam, while the remaining steps are completely consistent with Example 1.

[0092] Comparative Example 5

[0093] A method for preparing a nitrogen-doped carbon-coated binary nanosheet material FeCu-NC differs from Example 1 in that: cobalt nitrate is not added, and 1.3 mmol of Fe(NO3)3·9H2O is added; the remaining steps are completely consistent with those of Example 1.

[0094] Comparative Example 6

[0095] A method for preparing a nitrogen-doped carbon-coated binary nanosheet material CoCu-NC differs from Example 1 in that: ferric nitrate is not added, and 1.3 mmol of Co(NO3)3·6H2O is added; the remaining steps are completely consistent with those of Example 1.

[0096] Comparative Example 7

[0097] A method for preparing a nitrogen-doped carbon-coated quaternary nanosheet material FeCoCuNi-NC differs from Example 1 in that: 0.39 mmol of Fe(NO3)3·9H2O, 0.39 mmol of Co(NO3)2·6H2O, and 0.52 mmol of nickel nitrate are weighed and dissolved in 20 mL of deionized water, stirred evenly at room temperature to form solution A. The remaining steps are completely consistent with those in Example 1.

[0098] Comparative Example 8

[0099] A method for preparing a nitrogen-doped carbon-coated quaternary nanosheet material FeCoCuMn-NC differs from Example 1 in that: 0.39 mmol of Fe(NO3)3·9H2O, 0.39 mmol of Co(NO3)2·6H2O, and 0.52 mmol of manganese nitrate are weighed and dissolved in 20 mL of deionized water, stirred evenly at room temperature to form solution A. The remaining steps are completely consistent with those in Example 1.

[0100] Performance verification

[0101] 1. Structural characterization

[0102] Figure 1 The XRD patterns of FeCoCu-LDH (A), FeCoCu-ZIF (B), and FeCoCu-NC (C) prepared in Example 1 are shown.

[0103] exist Figure 1In (A), by comparing the diffraction peak positions in the FeCoCu-LDH spectrum with standard cards (Cu and LDH related standard cards), the peak positions in the spectrum match the characteristic peak positions in the LDH standard cards, indicating that FeCoCu-LDH possesses crystal structure features similar to standard LDH. The relative intensity of the peaks is close to the relative intensity of the corresponding crystal planes in the LDH standard structure, further supporting that FeCoCu-LDH has LDH structural features. Combining the above peak position and intensity analysis, it can be inferred that FeCoCu-LDH has a layered structure of layered double hydroxides, that is, a layered structure composed of positively charged metal hydroxide layers and interlayer anions interacting through electrostatic interactions and hydrogen bonds.

[0104] exist Figure 1 In (B), the diffraction peak positions of the FeCoCu-ZIF sample are compared with those of the ZIF67 standard card. The diffraction peaks at a specific 2θ angle match the characteristic peak positions of the ZIF67 standard card, indicating that FeCoCu-ZIF possesses crystal structure characteristics similar to ZIF67. The relative intensities of each diffraction peak in the FeCoCu-ZIF spectrum are similar to the relative intensity distribution of the corresponding crystal planes in the ZIF67 standard structure, further supporting its ZIF structural characteristics. Combining the above analysis, the characteristic peak positions and relative intensities are consistent with ZIF67, suggesting that FeCoCu-ZIF has a structure similar to ZIF67, namely, a metal-organic framework material with a three-dimensional porous network structure formed by coordination bonds between metal ions (Fe, Co, Cu) and imidazolium ester ligands.

[0105] exist Figure 1 In (C), FeCoCu-NC is compared with the Cu 85-1326 standard card. The diffraction peaks at a specific 2θ angle match the characteristic peak positions of Cu in the standard card, indicating the presence of Cu-related crystal structure features in the sample. The XRD patterns show peaks consistent with the characteristic peaks of metals (Fe, Co, Cu) and their compounds or carbon materials. Combined with information about its preparation process, it can be inferred that its shape is a ternary nanoneedle array encapsulated within a nitrogen-doped carbon framework.

[0106] Figure 2 TEM (A) and SEM (B) images of FeCoCu-LDH prepared in Example 1 of this invention.

[0107] exist Figure 2 In (A), FeCoCu-LDH is a ternary nanoneedle array structure. Figure 2 In (B), FeCoCu-NC exhibits nanoscale needle-like or rod-like structures that interweave to form a network-like morphology. Figure 1As can be seen, the ternary nanoneedle array is encapsulated within a nitrogen-doped carbon framework, and the FeCoCu-NC as a whole also exhibits a ternary nanoneedle shape. FeCoCu-NC is an iron-cobalt-copper-nitrogen-doped carbon material. This needle-like / rod-like interwoven structure is beneficial for increasing the specific surface area of ​​the material, which has a positive impact on applications such as electrocatalysis.

[0108] 2. Electrochemical performance testing:

[0109] Using a CHI660 electrochemical workstation in a 1M KOH + 0.1M hydrazine hydrate electrolyte, a three-electrode system was constructed, with the materials obtained in the examples and comparative examples as the working electrode, a platinum sheet as the counter electrode, and an Hg / HgO electrode as the reference electrode. The voltage range of the cyclic voltammetry was -0.3 to 1.8 V vs. RHE, the scan rate was 100 mV / s, and the LSV was measured after 10 cycles.

[0110] Figure 3 The figures show the electrochemical performance test results of the materials prepared in Examples 1-6 and Comparative Example 1 of this invention. Under the same potential, Example 1 exhibits the highest current density and the best catalytic performance, while Comparative Example 1 shows the lowest current density and the worst catalytic performance.

[0111] Figure 4 The figures show the electrochemical performance test results of the materials prepared in Comparative Examples 2-8 of this invention. The electrochemical performance of the materials prepared in Comparative Examples 2-8 is significantly lower than that of the materials in the Examples. Therefore, it can be concluded that only the materials obtained within the scope of this invention possess excellent electrochemical performance.

[0112] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a nitrogen-doped carbon-coated ternary nanoneedle array material, characterized in that, include: Ternary nanoneedles were grown in situ on a substrate using a hydrothermal reaction to obtain a ternary nanoneedle array; The ternary nanoneedle array was immersed in an aqueous solution of 2-methylimidazol, then removed, washed, and dried to obtain the ternary nanoneedle-ZIF precursor. The ternary nanoneedle-ZIF precursor was pyrolyzed to obtain a nitrogen-doped carbon-coated ternary nanoneedle array material. The substrate is pretreated before use; the pretreatment includes sequentially sonicating in an alcohol solution, water, an acid solution, and water. The substrate is copper foam; The hydrothermal reaction includes: preparing a solution containing iron ions and cobalt ions, then adding urea and ammonium fluoride, adding the substrate, and heating at 110-130℃ for 5-7 h to obtain a ternary nanoneedle array; The molar ratio of iron to cobalt in the ternary nanoneedles is 3:

7.

2. The preparation method according to claim 1, characterized in that, The ratio of metal ions, urea, and ammonium fluoride is 1-1.5 mmol: 280-320 mg: 90-95 mg.

3. The preparation method according to claim 1, characterized in that, The volume ratio of alcohol to water in the 2-methylimidazol aqueous solution is 0.9-1.1:0.9-1.1, and the concentration of 2-methylimidazol is 0.08-0.12 g / mL. The ratio of the ternary nanoneedle array to the 2-methylimidazol aqueous solution is such that one ternary nanoneedle array is placed in 20-40 mL of 2-methylimidazol aqueous solution; the size of the ternary nanoneedle array is 1×(3-4) cm.

4. The preparation method according to claim 1, characterized in that, The pyrolysis conditions are as follows: heating to 400-500℃ at a heating rate of 4-6℃ / min and holding at that temperature for 1.5-2.5 h.

5. A nitrogen-doped carbon-coated ternary nanoneedle array material prepared by the preparation method according to any one of claims 1-4, characterized in that, It includes a substrate, a ternary nanoneedle array grown on the surface of the substrate, and a nitrogen-doped carbon material loaded on the ternary nanoneedle array and the surface of the substrate; The substrate is copper foam, and the ternary nanoneedles are composed of iron, cobalt, and copper.

6. The nitrogen-doped carbon-coated ternary nanoneedle array material as described in claim 5, characterized in that, The ternary nanoneedles have a size of 3-5 μm.

7. The application of a nitrogen-doped carbon-coated ternary nanoneedle array material prepared by the preparation method according to any one of claims 1-4, or the nitrogen-doped carbon-coated ternary nanoneedle array material according to any one of claims 5-6, as a catalyst in the electrolysis of hydrazine hydrate.

8. A method for electrolyzing hydrazine hydrate, characterized in that, The nitrogen-doped carbon-coated ternary nanoneedle array material prepared by the preparation method according to any one of claims 1-4 or the nitrogen-doped carbon-coated ternary nanoneedle array material according to any one of claims 5-6 is used as an electrocatalyst.

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