Magnesium-based composite material containing NiFeCo-NCNT catalyst and preparation method thereof

Abstract

The invention relates to a magnesium-based composite material containing a NiFeCo-NCNT catalyst and a preparation method of the magnesium-based composite material, and the preparation method comprises the following steps: step 1, adding melamine and anhydrous dextrose into a deionized water solution, and uniformly stirring to obtain a yellow turbid solution; mixing an aqueous solution of metal nitrate, uniformly stirring and heating to obtain dry mixed powder, adding the mixed powder into the yellow turbid solution, stirring and heating again to obtain mixed dry powder, and grinding; 2, the ground mixed dry powder is placed in a high-temperature tube furnace to be subjected to high-temperature hot drying treatment in the argon atmosphere, and a NiFeCo-NCNT catalyst is obtained; 3, magnesium powder and the NiFeCo-NCNT catalyst are subjected to ball milling and then mixed, and a magnesium-based composite material containing the NiFeCo-NCNT catalyst is obtained; and 4, the magnesium-based composite material containing the NiFeCo-NCNT catalyst is subjected to high-temperature treatment. The catalyst has the characteristic of high flexibility, the activity, selectivity and stability of the catalyst are further enhanced through nanocrystallization and compounding strategies, and the application range of the catalyst is widened.

Description

Technical Field

[0001] The invention relates to the technical field of magnesium-based solid-state hydrogen storage materials, and in particular to a magnesium-based composite material containing a NiFeCo-NCNT catalyst and a preparation method thereof. Background Art

[0002] Magnesium-based hydrides have high theoretical capacity (mass density 7.6wt%) and excellent cycle stability. However, the high thermodynamic stability of the Mg-H bond makes the dehydrogenation temperature of MgH2 reach above 400°C, and the corresponding dehydrogenation reaction enthalpy is 75kJ / mol. Hydrogen molecules have difficulty dissociating on the Mg surface, and the diffusion kinetics in the Mg / MgH2 matrix are slow, which makes it difficult to activate magnesium-based hydrogen storage materials and the working temperature is very high, limiting large-scale commercial applications.

[0003] Nano-sizing, alloying and adding catalysts can effectively improve the thermal / kinetic properties of magnesium-based hydrogen storage materials. Nano-sizing methods include mechanical ball milling, physical / chemical vapor deposition, thermal decomposition, etc. Nano-sizing can increase the specific surface area of ​​MgH2, reduce the size of the internal grains of the material, increase the surface energy of the material and reduce the material stress. These conditions can greatly improve the thermodynamic and kinetic properties of MgH2. The alloying method is to reduce the bond energy of metal bonding by mixing magnesium with some metal elements to form an alloy phase, thereby reducing the energy required for adsorption and release of hydrogen.

[0004] Compared with alloying and nano-sizing, catalyst modification is an effective way to improve the hydrogen absorption and desorption performance of the Mg / MgH2 system. The addition of a small amount of catalyst can not only maintain a high hydrogen storage capacity, but also effectively improve its hydrogen storage kinetics and cycle stability.

[0005] At present, the catalysts mainly include transition metal catalysts, carbon material catalysts and metal oxide catalysts. For transition metal catalysts, such as Ti, V, Zr, Nb, etc., catalytic active centers can be introduced into magnesium-based hydrogen storage materials to reduce the activation energy of hydrogen dissociation, thereby optimizing its kinetic properties. For example, Cui et al. (CUI J, et al. Journal of Materials Chemistry A, 2014, 2 (25): 9645-9655.) used ball milling combined with chemical reduction to synthesize a series of core-shell structured Mg-TM (TM = Ti, Nb, V, Co, Mo or Ni) composite materials. Studies have shown that the hydrogen absorption of Mg-Ti samples at 270°C and 2MPa within 5 minutes reaches 5.5wt% (mass fraction, the same below), and the dehydrogenation amount at 275°C within 10 minutes reaches 6.35wt%.

[0006] However, although a single transition metal catalyst can effectively reduce the hydrogen dissociation process, it also increases the activation energy of hydrogen diffusion, resulting in a decrease in catalytic performance. Carbon materials can also be used as catalysts or co-catalysts to promote the hydrogen absorption and desorption process of magnesium-based hydrogen storage materials.

[0007] Zhang Xing et al. (ZHANG X, et al. [J]. Journal of Power Sources, 2018, 398: 183-192.) systematically studied the effect of the coupling of metal oxide TiO2 and porous carbon materials on the hydrogen storage performance of MgH2. The study showed that TiO2 loaded on the porous carbon structure can accelerate the diffusion of hydrogen in bulk MgH2 by increasing the transfer channels and further improve the catalytic activity of TiO2, thereby greatly improving the hydrogen absorption and desorption performance of hydrogen storage materials.

[0008] Although the catalysts reported so far have improved the hydrogen storage performance of MgH2 to varying degrees, they cannot meet the demand for rapid and large-capacity hydrogen absorption and desorption of hydrogen by hydrogen storage materials. Therefore, it is urgent to develop new and efficient magnesium-based hydrogen storage material catalysts and preparation methods, which have important development prospects and practical value. Summary of the invention

[0009] In order to overcome the defects of the above-mentioned prior art, the purpose of the present invention is to provide a magnesium-based composite material containing NiFeCo-NCNT catalyst and a preparation method thereof, wherein the preparation method has the characteristics of high flexibility, and the nano-sizing and composite strategies further enhance the activity, selectivity and stability of the catalyst.

[0010] In order to achieve the above object, the technical solution adopted by the present invention is:

[0011] A magnesium-based composite material containing a NiFeCo-NCNT catalyst consists of nitrogen carbon nanotubes (NCNT) and NiFeCo medium-entropy alloy nanoparticles, wherein the NiFeCo medium-entropy alloy nanoparticles are uniformly and discretely distributed on the inner wall of the NCNT.

[0012] Nitrogen carbon nanotubes are coaxial or basically coaxial circular tube structures of carbon nanotubes, which are composed of layers of hexagonally arranged carbon atoms stacked one on top of the other. The diameter of nitrogen carbon nanotubes is 0.45-0.65 microns and the length is 6-15 microns.

[0013] Nitrogen atoms are doped into carbon nanotubes.

[0014] The NiFeCo mesohypermetal alloy nanoparticles have a small nanoscale size of 30-100 nanometers, and the elements are evenly distributed, forming a specific phase structure;

[0015] During the ball milling process, the NiFeCo-NCNT catalyst and magnesium powder are fully physically mixed under the impact and shear force of the ball milling medium, so that the catalyst particles are effectively dispersed and fully combined in the magnesium powder matrix;

[0016] The dosage of NiFeCo-NCNT catalyst and magnesium powder is 1:9.

[0017] A method for preparing a magnesium-based composite material containing a NiFeCo-NCNT catalyst comprises the following steps:

[0018] Step 1: Add melamine and anhydrous glucose to a deionized water solution and stir until a yellow turbid solution is obtained;

[0019] Subsequently, aqueous solutions of metal nitrates of Ni, Fe and Co are mixed, stirred evenly, heated and volatilized to obtain a dry mixed powder, and then the mixed powder is added to the yellow turbid solution, stirred, heated and volatilized again to obtain a mixed dry powder and ground;

[0020] Step 2: placing the ground mixed dry powder in a high temperature tube furnace for high temperature heat drying treatment under an argon atmosphere to obtain a NiFeCo-NCNT catalyst;

[0021] Step 3, ball-milling the magnesium powder and the NiFeCo-NCNT catalyst and mixing them to obtain a magnesium-based composite material containing the NiFeCo-NCNT catalyst;

[0022] Step 4: High temperature treatment of the magnesium-based composite material containing the NiFeCo-NCNT catalyst.

[0023] The step 1 is specifically as follows:

[0024] The magnetic stirrer was set to a speed of 450-550 r / min and stirred until a yellow turbid solution was obtained;

[0025] Subsequently, the aqueous solutions of metal nitrates are mixed, stirred and evenly heated at 50-60° C. to obtain a dry mixed powder, and then the mixed powder is added to the yellow turbid solution, stirred and heated again to obtain a mixed dry powder and ground.

[0026] The molar mass ratio of melamine, anhydrous glucose and metal nitrate is (1-3.0): (1-1.5): (0.8-1). The capacity of deionized water needs to meet the requirement of complete dissolution of melamine and anhydrous glucose, and when dissolving metal salts, the deionized water also needs to completely dissolve each metal salt.

[0027] The metal nitrate is a mixture of Co(NO3)2·6H2O, Ni(NO3)2·6H2O and Fe(NO3)3·9H2O.

[0028] The step 2 is specifically as follows:

[0029] The conditions for high temperature heat drying in a high temperature tube furnace under argon atmosphere are as follows: the heating rate is 3-5℃min -1 , and sintered at 800-900℃ for 2-3h to obtain NiFeCo-NCNT catalyst. The optimal catalytic parameters of the catalyst were explored by adjusting different parameters.

[0030] The step 3 is specifically as follows:

[0031] Two-step ball milling method:

[0032] ① The magnesium powder is subjected to high-energy ball milling (rotation speed is 1000r), and the magnesium powder particles are refined under the high-speed collision and extrusion of the grinding balls to obtain a particle size distribution of 10 to 45μm. This helps to increase the surface area and reaction activity of the magnesium powder.

[0033] ② The magnesium powder and the NiFeCo-NCNT catalyst were mixed and subjected to low-energy ball milling (rotation speed of 350r). The NiFeCo-NCNT catalyst and the magnesium powder were ball milled in a mass ratio of 1:9 to prevent powder agglomeration and make the powders mixed evenly to obtain a magnesium-based composite material containing the NiFeCo-NCNT catalyst.

[0034] The conditions for high temperature treatment in step 4 are:

[0035] The magnesium-based composite material containing the NiFeCo-NCNT catalyst was then treated in a high-temperature and high-pressure reactor;

[0036] The reaction temperature is 250-300° C., 3-4 MPa of hydrogen is applied, and the hydrogenation process is carried out for 450-600 minutes. After hydrogenation, a magnesium-based composite hydrogen storage material containing a NiFeCo-NCNT catalyst is obtained.

[0037] The magnesium-based composite hydrogen storage material containing NiFeCo-NCNT catalyst has the advantages of large hydrogen storage capacity, fast hydrogen absorption and desorption rate, and good cycle stability. It can be used in hydrogen energy storage and transportation, fuel cell hydrogen supply system and other fields.

[0038] Hydrogen absorption and desorption performance test

[0039] The hydrogen storage performance of the magnesium-based composite hydrogen storage material containing NiFeCo-NCNT catalyst was tested using the H-SorbX600 high-temperature and high-pressure gas adsorption instrument. The sample was first treated at 225-400°C. Then, the adsorption and desorption kinetics test was performed, with the adsorption pressure set to 1-6MPa and the temperature condition set to 225-350°C, and the adsorption and desorption time set to 60-120min, to obtain the adsorption and desorption kinetics curve.

[0040] The beneficial effects of the present invention are:

[0041] (1) The multi-component NiFeCo-NCNT catalyst is rapidly prepared by combining the hydrothermal method with the high-temperature sintering technology, which significantly reduces the catalyst preparation cost and promotes the industrial preparation of magnesium-based solid hydrogen storage materials. Moreover, the hydrogen storage material prepared by the present invention has a grain diameter of about 0.6 microns and a length of 6-15 microns, which is beneficial to the hydrogen storage and desorption performance of magnesium-based hydrogen storage materials when combined with the solid-phase diffusion mechanism.

[0042] (2) The transition metal medium-entropy alloy nanoparticles (<50 nm) synthesized in the present invention are encapsulated inside carbon nanotubes and have good dispersibility and abundant active sites, which are beneficial to the diffusion of hydrogen molecules. The transition metal nanoparticles can also greatly improve the overall catalytic efficiency and greatly improve the thermodynamic and kinetic deficiencies of MgH2 solid-state hydrogen storage materials.

[0043] Among them, the medium-entropy alloy nanoparticles encapsulated in carbon nanotubes can significantly reduce the dehydrogenation temperature of MgH2. This is because the high catalytic activity of the nanoparticles promotes the decomposition reaction of MgH2, reducing the energy required for the reaction.

[0044] The addition of catalyst can improve the dehydrogenation kinetics of MgH2, including the dehydrogenation rate and dehydrogenation amount. The nano-scale medium-entropy alloy particles provide more active sites, accelerating the release of hydrogen. At the same time, the channel effect of carbon nanotubes also contributes to the rapid transmission of hydrogen.

[0045] The excellent dispersion properties of carbon materials enable the medium-entropy alloy nanoparticles encapsulated therein to remain stable during the catalytic process and not easily deactivated. This helps to improve the cycle stability of MgH2 hydrogen storage materials, allowing them to maintain a high hydrogen storage capacity after multiple cycles of hydrogen absorption and desorption.

[0046] At the same time, carbon nanotubes themselves have hydrogen storage properties, thereby improving the hydrogen storage capacity of the overall magnesium-based solid hydrogen storage material. Therefore, the NiFeCo-NCNT catalyst developed by the present invention can achieve the synergistic catalytic effect of medium-entropy alloy nanoparticles and carbon nanotubes in the magnesium-based hydrogen storage material, thereby greatly improving its hydrogen storage and desorption performance.

[0047] (3) In terms of hydrogen absorption and desorption performance, the magnesium-based composite hydrogen storage material containing NiFeCo-NCNT catalyst developed by the present invention can rapidly absorb 5.42wt% of hydrogen within 1 minute under the conditions of 275°C and 2MPa, and the maximum hydrogen absorption amount is 6.52wt% (hydrogen storage efficiency is 95%). Rapidly release 2.73wt% of hydrogen within 1 minute, and the maximum hydrogen release amount is 5.32wt% (hydrogen release efficiency is 82%). The hydrogen absorption amount is 5.23wt% under the environment of 250°C, and the hydrogen release amount can reach 2.53wt%. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 Schematic diagram of the NiFeCo-NCNT catalyst structure.

[0049] Figure 2 This is the morphology of NiFeCo-NCNT catalyst.

[0050] Figure 3 XRD results of NiFeCo-NCNT catalyst.

[0051] Figure 4 This is the hydrogen desorption kinetics curve of the magnesium-based composite hydrogen storage material containing NiFeCo-NCNT catalyst.

[0052] Figure 5 This is the hydrogen absorption kinetic curve of the magnesium-based composite hydrogen storage material containing NiFeCo-NCNT catalyst.

[0053] Figure 6 This is the hydrogen desorption kinetics curve of the magnesium-based composite hydrogen storage material containing NiFeCo-NCNT catalyst.

[0054] Figure 7 This is the hydrogen absorption kinetic curve of the magnesium-based composite hydrogen storage material containing NiFeCo-NCNT catalyst.

[0055] Figure 8 This is the hydrogen desorption kinetics curve of the magnesium-based composite hydrogen storage material containing NiFeCo-NCNT catalyst.

[0056] Fig. 9 This is the hydrogen absorption kinetic curve of the magnesium-based composite hydrogen storage material containing NiFeCo-NCNT catalyst.

[0057] Fig.10 This is the hydrogen desorption kinetics curve of the magnesium-based composite hydrogen storage material containing NiFeCo-NCNT catalyst.

[0058] Fig.11 This is the hydrogen absorption kinetic curve of the magnesium-based composite hydrogen storage material containing NiFeCo-NCNT catalyst.

[0059] Fig.12 This is the hydrogen desorption kinetics curve of the magnesium-based composite hydrogen storage material containing NiFeCo-NCNT catalyst.

[0060] Fig.13 This is the hydrogen absorption kinetic curve of the magnesium-based composite hydrogen storage material containing NiFeCo-NCNT catalyst. DETAILED DESCRIPTION

[0061] The present invention will be further described in detail below in conjunction with the accompanying drawings.

[0062] Embodiment 1:

[0063] (1) Raw materials

[0064] The raw materials include melamine, anhydrous glucose, Co(NO3)2·6H2O, Ni(NO3)2·6H2O, Fe(NO3)3·9H2O and deionized water.

[0065] In order to prevent the raw materials from reacting with air, they should be stored in a vacuum glove box.

[0066] The purpose and principle of this step: to prevent the raw materials from reacting with oxygen, moisture or other impurities in the air, thereby maintaining the purity and chemical stability of the raw materials, ensuring the smooth progress of the subsequent synthesis or preparation process and the performance and quality of the final product.

[0067] Melamine and anhydrous glucose: As carbon sources, carbonization reactions may occur at high temperatures to form carbon nanostructures (NCNTs). These carbon nanostructures not only provide carriers for catalysts, but also may enhance the overall performance and stability of the material.

[0068] Deionized water: used as a solvent to dissolve melamine, anhydrous glucose and metal nitrate to form a uniform solution. The use of deionized water can avoid the influence of ions in the solution on the subsequent synthesis process.

[0069] Co(NO3)2·6H2O, Ni(NO3)2·6H2O, Fe(NO3)3·9H2O: Provide Ni, Fe, and Co elements, which are reduced to metal nanoparticles during the subsequent heat treatment process to form medium-entropy alloy nanoparticles (NiFeCo). These metal nanoparticles act as catalysts to accelerate specific chemical reactions, such as the adsorption and desorption of hydrogen, thereby improving the performance of hydrogen storage materials.

[0070] Magnesium powder: It is the main component of magnesium-based composite hydrogen storage materials and has the advantages of light weight and high hydrogen storage density. The composite of magnesium powder and NiFeCo-NCNT catalyst can further improve the hydrogen storage performance and cycle stability of the material. (2) Preparation of precursor liquid

[0071] Add appropriate amount of melamine and anhydrous glucose to the deionized water solution, set the speed of the magnetic stirrer to 450r / min (this speed is suitable for the specific mixing requirements of the experiment, and can achieve efficient stirring and mixing while avoiding excessive shearing of the material), and stir until uniform to obtain a yellow turbid solution. Then, mix the aqueous solution of metal nitrates, stir and heat evenly to 60°C (60°C is a moderate temperature, which can not only promote the dissolution and uniform mixing of nitrates, but also avoid excessive temperature causing nitrate decomposition or other undesirable chemical reactions), to obtain a dry mixed powder, which is then added to the yellow turbid solution, stirred and heated again to obtain a mixed dry powder and ground. The molar mass ratio of Co(NO3)2·6H2O, Ni(NO3)2·6H2O, and Fe(NO3)3·9H2O is 1:1:1. (The main purpose of changing the molar mass ratio is to optimize the performance of the finally synthesized NiFeCo-NCNT catalyst and magnesium-based composite hydrogen storage material by adjusting the relative content of these metal nitrates.)

[0072] The molar mass ratio of melamine, anhydrous glucose and metal nitrate is 1:1:0.8 (the best catalytic effect and hydrogen storage capacity are achieved by precisely controlling the ratio of each component); the capacity of deionized water needs to meet the requirement of complete dissolution of melamine and anhydrous glucose, and when dissolving metal salts, the deionized water also needs to completely dissolve each metal salt.

[0073] The purpose and principle of this step is to prepare a precursor powder containing uniformly distributed Ni, Fe, Co elements and a carbon source by dissolving, mixing, drying and grinding chemical substances (melamine, anhydrous glucose and metal nitrate) in specific proportions, which provides a basis for the subsequent synthesis or preparation of magnesium-based composite hydrogen storage materials containing NiFeCo-NCNT catalysts.

[0074] (3) Synthesis of NiFeCo-NCNT catalyst

[0075] The mixture powder obtained in step (2) was placed in a high-temperature tube furnace for high-temperature heat drying in an argon atmosphere at a heating rate of 3°C min -1 , (In order to ensure that the material is heated evenly, to avoid thermal stress concentration and uneven distribution of components caused by too fast a temperature rise, and thus to optimize the structure and performance of the catalyst.) Sintering at 800°C for 3h resulted in a carbon nanotube-medium entropy alloy nanoparticle composite material (NiFeCo-NCNT). (The high temperature of 800°C and the sintering time of 3 hours can ensure that the organic matter is fully carbonized to form carbon nanotubes, while the metal nitrate is reduced to medium entropy alloy nanoparticles, and the two are well combined, thus obtaining a composite material with excellent performance.)

[0076] The purpose and principle of this step: The NiFeCo-NCNT catalyst is synthesized by high-temperature thermal drying treatment. The principle is to use high temperature in an argon atmosphere to carbonize the organic matter in the mixed powder to form carbon nanotubes, and at the same time reduce the metal nitrate to medium-entropy alloy nanoparticles, thereby obtaining a carbon nanotube-medium-entropy alloy nanoparticle composite material (NiFeCo-NCNT).

[0077] (4) Synthesis of magnesium-based composites containing NiFeCo-NCNT catalyst

[0078] Two-step ball milling method: ① High-energy ball milling (rotation speed of 1000r) of magnesium powder (1000r high speed can provide enough energy to effectively refine magnesium powder particles under the high-speed collision and extrusion of grinding balls, thereby obtaining a smaller particle size distribution and a higher surface area, which helps to improve the reactivity of magnesium powder). Magnesium powder particles are refined under the high-speed collision and extrusion of grinding balls to obtain a smaller particle size distribution. This helps to increase the surface area and reactivity of magnesium powder. ② Mix magnesium powder and catalyst for low-energy ball milling (rotation speed of 350r) (350r low speed helps to reduce excessive collision and crushing between powder particles, while ensuring that the catalyst and magnesium powder can be evenly mixed, effectively preventing powder agglomeration and improving the overall performance and uniformity of the material.), ball milling NiFeCo-NCNT catalyst and magnesium powder to prevent powder agglomeration and make the powders mixed evenly, and obtain a magnesium-based composite material containing NiFeCo-NCNT catalyst.

[0079] The purpose and principle of this step: The magnesium powder is refined by a two-step ball milling method and uniformly mixed with the NiFeCo-NCNT catalyst to improve the surface area, reaction activity and dispersion uniformity of the magnesium-based composite material, thereby obtaining a magnesium-based composite material containing the NiFeCo-NCNT catalyst.

[0080] (5) Synthesis of magnesium-based composite hydrogen storage materials containing NiFeCo-NCNT catalyst

[0081] The magnesium-based composite material containing the NiFeCo-NCNT catalyst was subsequently treated in a high-temperature and high-pressure reactor at a reaction temperature of 300°C and 4 MPa of hydrogen was applied to perform a hydrogenation process for 600 minutes (the reaction temperature of 300°C, 4 MPa of hydrogen and 600 minutes of hydrogenation process were selected to promote the full reaction of the magnesium-based composite material with hydrogen under suitable conditions, thereby improving the hydrogenation efficiency and hydrogen storage performance.), and a magnesium-based composite hydrogen storage material containing the NiFeCo-NCNT catalyst was obtained after hydrogenation.

[0082] The purpose and principle of this step: Through a high-temperature and high-pressure hydrogenation process, the magnesium-based composite material containing the NiFeCo-NCNT catalyst absorbs hydrogen to form a stable metal hydride, thereby improving its hydrogen storage performance.

[0083] (6) Hydrogen absorption and desorption performance test

[0084] The hydrogen storage performance of magnesium-based solid hydrogen storage materials containing NiFeCo-NCNT catalysts was tested using H-SorbX600 high-temperature and high-pressure gas adsorption instrument. The samples were first treated at 300°C. Then, the adsorption and desorption kinetics test was performed. The adsorption pressure was set to 2MPa and the temperature conditions were 275°C, 250°C and 225°C. The adsorption and desorption time was set to 60min, and the adsorption and desorption kinetics curve was obtained (pre-treating the sample at 300°C ensures that the material is in a stable state, while the adsorption pressure of 2MPa and different temperature conditions (275°C, 250°C, 225°C) and the adsorption and desorption time of 60min are used to evaluate the hydrogen storage kinetics of the material under different conditions.), see Figure 3-4 .

[0085] The obtained magnesium-based composite hydrogen storage material containing NiFeCo-NCNT catalyst can rapidly absorb 5.14wt% hydrogen within 1 minute at 275°C, with a maximum hydrogen absorption of 5.78wt%, and rapidly release 1.78wt% hydrogen within 1 minute, with a maximum hydrogen release of 3.82wt%.

[0086] Purpose and principle of this step: Use H-SorbX600 high temperature and high pressure gas adsorption instrument to test the hydrogen storage performance of magnesium-based solid hydrogen storage materials containing NiFeCo-NCNT catalysts, and evaluate its hydrogen absorption and desorption kinetics and hydrogen storage capacity by simulating the adsorption and desorption process under different temperature and pressure conditions.

[0087] Example 2

[0088] (1) Raw materials

[0089] The raw materials include melamine, anhydrous glucose, Co(NO3)2·6H2O, Ni(NO3)2·6H2O, Fe(NO3)3·9H2O and deionized water.

[0090] In order to prevent the raw materials from reacting with air, they should be stored in a vacuum glove box.

[0091] (2) Preparation of precursor solution

[0092] Add appropriate amount of melamine and anhydrous glucose to the deionized water solution, set the speed of the magnetic stirrer to 450r / min and stir until uniform to obtain a yellow turbid solution. Then, mix the aqueous solution of metal nitrates, stir and heat evenly at 60°C to obtain a dry mixed powder, which is then added to the yellow turbid solution and stirred and heated again to obtain a mixed dry powder and grind. The molar mass ratio of Co(NO3)2·6H2O, Ni(NO3)2·6H2O, and Fe(NO3)3·9H2O is 2:1:1. The molar mass ratio of melamine, anhydrous glucose and metal nitrate is 1:1:0.8; the capacity of deionized water needs to meet the requirement of complete dissolution of melamine and anhydrous glucose, and when dissolving metal salts, deionized water also needs to completely dissolve each metal salt.

[0093] (3) Synthesis of NiFeCo-NCNT catalyst

[0094] The mixture powder obtained in step (2) was placed in a high-temperature tube furnace for high-temperature heat drying in an argon atmosphere at a heating rate of 3°C min -1 , and sintered at 800 °C for 3 h to obtain a carbon nanotube-medium entropy alloy nanoparticle composite material (NiFeCo-NCNT).

[0095] (4) Synthesis of magnesium-based composites containing NiFeCo-NCNT catalyst

[0096] Two-step ball milling method: ① The magnesium powder is subjected to high-energy ball milling (rotation speed is 1000r). The magnesium powder particles are refined under the high-speed collision and extrusion of the grinding balls to obtain a smaller particle size distribution. This helps to increase the surface area and reaction activity of the magnesium powder. ② The magnesium powder is mixed with the catalyst and low-energy ball milling is performed (rotation speed is 350r). The NiFeCo-NCNT catalyst and magnesium powder are ball milled to prevent powder agglomeration and make the powders evenly mixed to obtain a magnesium-based composite material containing the NiFeCo-NCNT catalyst.

[0097] (5) Synthesis of magnesium-based composite hydrogen storage materials containing NiFeCo-NCNT catalyst

[0098] The magnesium-based composite material containing the NiFeCo-NCNT catalyst was subsequently treated in a high-temperature and high-pressure reactor at a reaction temperature of 300°C, with 4MPa of hydrogen applied, and a hydrogenation process was performed for 600 minutes. After hydrogenation, a magnesium-based composite hydrogen storage material containing the NiFeCo-NCNT catalyst was obtained.

[0099] (6) Hydrogen absorption and desorption performance test

[0100] The hydrogen storage performance of magnesium-based solid hydrogen storage materials containing NiFeCo-NCNT catalysts was tested using H-SorbX600 high-temperature and high-pressure gas adsorption instrument. The samples were first treated at 300°C. Then, the adsorption and desorption kinetics test was performed. The adsorption pressure was set to 2MPa and the temperature conditions were 275°C, 250°C and 225°C. The adsorption and desorption time was set to 60min. The adsorption and desorption kinetics curves were obtained, as shown in Figure 2. Figure 5-6 .

[0101] The obtained magnesium-based composite hydrogen storage material containing NiFeCo-NCNT catalyst can quickly absorb 5.78wt% of hydrogen in 1 minute at 275°C, with a maximum hydrogen absorption of 6.23wt%. It can quickly release 2.94wt% of hydrogen in 1 minute, with a maximum hydrogen release of 5.02wt%. The hydrogen release can reach 2.78wt% in 250°C.

[0102] Example 3

[0103] (1) Raw materials

[0104] The raw materials include melamine, anhydrous glucose, Co(NO3)2·6H2O, Ni(NO3)2·6H2O, Fe(NO3)3·9H2O and deionized water.

[0105] In order to prevent the raw materials from reacting with air, they should be stored in a vacuum glove box.

[0106] (2) Preparation of precursor solution

[0107] Add appropriate amount of melamine and anhydrous glucose to the deionized water solution, set the speed of the magnetic stirrer to 450r / min and stir until uniform to obtain a yellow turbid solution. Then, mix the aqueous solution of metal nitrates, stir and heat evenly at 60°C to obtain a dry mixed powder, which is then added to the yellow turbid solution and stirred and heated again to obtain a mixed dry powder and grind. The molar mass ratio of Co(NO3)2·6H2O, Ni(NO3)2·6H2O, and Fe(NO3)3·9H2O is 1:2:1. The molar mass ratio of melamine, anhydrous glucose and metal nitrate is 1:1:0.8; the capacity of deionized water needs to meet the requirement of complete dissolution of melamine and anhydrous glucose, and when dissolving metal salts, deionized water also needs to completely dissolve each metal salt.

[0108] (3) Synthesis of NiFeCo-NCNT catalyst

[0109] The mixture powder obtained in step (2) was placed in a high-temperature tube furnace for high-temperature heat drying in an argon atmosphere at a heating rate of 3°C min -1, and sintered at 800 °C for 3 h to obtain a carbon nanotube-medium entropy alloy nanoparticle composite material (NiFeCo-NCNT).

[0110] (4) Synthesis of magnesium-based composites containing NiFeCo-NCNT catalyst

[0111] Two-step ball milling method: ① The magnesium powder is subjected to high-energy ball milling (rotation speed is 1000r). The magnesium powder particles are refined under the high-speed collision and extrusion of the grinding balls to obtain a smaller particle size distribution. This helps to increase the surface area and reaction activity of the magnesium powder. ② The magnesium powder is mixed with the catalyst and low-energy ball milling is performed (rotation speed is 350r). The NiFeCo-NCNT catalyst and magnesium powder are ball milled to prevent powder agglomeration and make the powders evenly mixed to obtain a magnesium-based composite material containing the NiFeCo-NCNT catalyst.

[0112] (5) Synthesis of magnesium-based composite hydrogen storage materials containing NiFeCo-NCNT catalyst

[0113] The magnesium-based composite material containing the NiFeCo-NCNT catalyst was subsequently treated in a high-temperature and high-pressure reactor at a reaction temperature of 300°C, with 4MPa of hydrogen applied, and a hydrogenation process was performed for 600 minutes. After hydrogenation, a magnesium-based composite hydrogen storage material containing the NiFeCo-NCNT catalyst was obtained.

[0114] (6) Hydrogen absorption and desorption performance test

[0115] The hydrogen storage performance of magnesium-based solid hydrogen storage materials containing NiFeCo-NCNT catalysts was tested using H-SorbX600 high-temperature and high-pressure gas adsorption instrument. The samples were first treated at 300°C. Then, the adsorption and desorption kinetics test was performed. The adsorption pressure was set to 2MPa and the temperature conditions were 275°C, 250°C and 225°C. The adsorption and desorption time was set to 60min. The adsorption and desorption kinetics curves were obtained. Figure 7-8 .

[0116] The obtained magnesium-based composite hydrogen storage material containing NiFeCo-NCNT catalyst can quickly absorb 5.42wt% of hydrogen in 1 minute at 275°C, with a maximum hydrogen absorption of 6.52wt%. It can quickly release 2.73wt% of hydrogen in 1 minute, with a maximum hydrogen release of 5.32wt%. The hydrogen release can reach 2.53wt% at 250°C.

[0117] Example 4

[0118] (1) Raw materials

[0119] The raw materials include melamine, anhydrous glucose, Co(NO3)2·6H2O, Ni(NO3)2·6H2O, Fe(NO3)3·9H2O and deionized water.

[0120] In order to prevent the raw materials from reacting with air, they should be stored in a vacuum glove box.

[0121] (2) Preparation of precursor solution

[0122] Add appropriate amount of melamine and anhydrous glucose to the deionized water solution, set the speed of the magnetic stirrer to 450r / min and stir until uniform to obtain a yellow turbid solution. Then, mix the aqueous solution of metal nitrates, stir and heat evenly at 60°C to obtain a dry mixed powder, which is then added to the yellow turbid solution and stirred and heated again to obtain a mixed dry powder and grind. The molar mass ratio of Co(NO3)2·6H2O, Ni(NO3)2·6H2O, and Fe(NO3)3·9H2O is 1:1:2. The molar mass ratio of melamine, anhydrous glucose and metal nitrate is 1:1:0.8; the capacity of deionized water needs to meet the requirement of complete dissolution of melamine and anhydrous glucose, and the deionized water also needs to completely dissolve each metal salt when dissolving the metal salt.

[0123] (3) Synthesis of NiFeCo-NCNT catalyst

[0124] The mixture powder obtained in step (2) was placed in a high-temperature tube furnace for high-temperature heat drying in an argon atmosphere at a heating rate of 3°C min -1 , and sintered at 800 °C for 3 h to obtain a carbon nanotube-medium entropy alloy nanoparticle composite material (NiFeCo-NCNT).

[0125] (4) Synthesis of magnesium-based composites containing NiFeCo-NCNT catalyst

[0126] Two-step ball milling method: ① The magnesium powder is subjected to high-energy ball milling (rotation speed is 1000r). The magnesium powder particles are refined under the high-speed collision and extrusion of the grinding balls to obtain a smaller particle size distribution. This helps to increase the surface area and reaction activity of the magnesium powder. ② The magnesium powder is mixed with the catalyst and low-energy ball milling is performed (rotation speed is 350r). The NiFeCo-NCNT catalyst and magnesium powder are ball milled to prevent powder agglomeration and make the powders evenly mixed to obtain a magnesium-based composite material containing the NiFeCo-NCNT catalyst.

[0127] (5) Synthesis of magnesium-based composite hydrogen storage materials containing NiFeCo-NCNT catalyst

[0128] The magnesium-based composite material containing the NiFeCo-NCNT catalyst was subsequently treated in a high-temperature and high-pressure reactor at a reaction temperature of 300°C, with 4MPa of hydrogen applied, and a hydrogenation process was performed for 600 minutes. After hydrogenation, a magnesium-based composite hydrogen storage material containing the NiFeCo-NCNT catalyst was obtained.

[0129] (6) Hydrogen absorption and desorption performance test

[0130] The hydrogen storage performance of magnesium-based solid hydrogen storage materials containing NiFeCo-NCNT catalysts was tested using H-SorbX600 high-temperature and high-pressure gas adsorption instrument. The samples were first treated at 300°C. Then, the adsorption and desorption kinetics test was performed. The adsorption pressure was set to 2MPa and the temperature conditions were 275°C, 250°C and 225°C. The adsorption and desorption time was set to 60min. The adsorption and desorption kinetics curves were obtained, as shown in Figure 2. Figure 9-10 .

[0131] The obtained magnesium-based composite hydrogen storage material containing NiFeCo-NCNT catalyst can rapidly absorb 5.53wt% of hydrogen within 1 minute at 275°C, with a maximum hydrogen absorption of 5.68wt%, and rapidly release 1.52wt% of hydrogen within 1 minute, with a maximum hydrogen release of 3.56wt%.

[0132] Example 5

[0133] (1) Raw materials

[0134] The raw materials include melamine, anhydrous glucose, Co(NO3)2·6H2O, Ni(NO3)2·6H2O, Fe(NO3)3·9H2O and deionized water.

[0135] In order to prevent the raw materials from reacting with air, they should be stored in a vacuum glove box.

[0136] (2) Preparation of precursor solution

[0137] Add appropriate amount of melamine and anhydrous glucose to the deionized water solution, set the speed of the magnetic stirrer to 450r / min and stir until uniform to obtain a yellow turbid solution. Then, mix the aqueous solution of metal nitrates, stir and heat evenly at 60°C to obtain a dry mixed powder, which is then added to the yellow turbid solution and stirred and heated again to obtain a mixed dry powder and grind. The molar mass ratio of Co(NO3)2·6H2O, Ni(NO3)2·6H2O, and Fe(NO3)3·9H2O is 2:2:1. The molar mass ratio of melamine, anhydrous glucose and metal nitrate is 1:1:0.8; the capacity of deionized water needs to meet the requirement of complete dissolution of melamine and anhydrous glucose, and when dissolving metal salts, deionized water also needs to completely dissolve each metal salt.

[0138] (3) Synthesis of NiFeCo-NCNT catalyst

[0139] The mixture powder obtained in step (2) was placed in a high-temperature tube furnace for high-temperature heat drying in an argon atmosphere at a heating rate of 3°C min -1 , and sintered at 800 °C for 3 h to obtain a carbon nanotube-medium entropy alloy nanoparticle composite material (NiFeCo-NCNT).

[0140] (4) Synthesis of magnesium-based composites containing NiFeCo-NCNT catalyst

[0141] Two-step ball milling method: ① The magnesium powder is subjected to high-energy ball milling (rotation speed is 1000r). The magnesium powder particles are refined under the high-speed collision and extrusion of the grinding balls to obtain a smaller particle size distribution. This helps to increase the surface area and reaction activity of the magnesium powder. ② The magnesium powder is mixed with the catalyst and low-energy ball milling is performed (rotation speed is 350r). The NiFeCo-NCNT catalyst and magnesium powder are ball milled to prevent powder agglomeration and make the powders evenly mixed to obtain a magnesium-based composite material containing the NiFeCo-NCNT catalyst.

[0142] (5) Synthesis of magnesium-based composite hydrogen storage materials containing NiFeCo-NCNT catalyst

[0143] The magnesium-based composite material containing the NiFeCo-NCNT catalyst was subsequently treated in a high-temperature and high-pressure reactor at a reaction temperature of 300°C, with 4MPa of hydrogen applied, and a hydrogenation process was performed for 600 minutes. After hydrogenation, a magnesium-based composite hydrogen storage material containing the NiFeCo-NCNT catalyst was obtained.

[0144] (6) Hydrogen absorption and desorption performance test

[0145] The hydrogen storage performance of magnesium-based solid hydrogen storage materials containing NiFeCo-NCNT catalysts was tested using H-SorbX600 high-temperature and high-pressure gas adsorption instrument. The samples were first treated at 300°C. Then, the adsorption and desorption kinetics test was performed. The adsorption pressure was set to 2MPa and the temperature conditions were 275°C, 250°C and 225°C. The adsorption and desorption time was set to 60min. The adsorption and desorption kinetics curves were obtained, as shown in Figure 2. Figure 11-12 .

[0146] The obtained magnesium-based composite hydrogen storage material containing NiFeCo-NCNT catalyst can quickly absorb 5.14wt% of hydrogen within 1 minute at 275°C, with a maximum hydrogen absorption of 5.32wt%. It can quickly release 2.32wt% of hydrogen within 1 minute, with a maximum hydrogen release of 3.94wt%. The hydrogen release can reach 2.56wt% at 250°C.

[0147] like Figure 1 As shown, it is a schematic diagram of the NiFeCo-NCNT catalyst structure. From the figure, it can be intuitively shown that the catalyst is composed of metal nanoparticles uniformly embedded in nitrogen-doped carbon nanotubes, and the medium-entropy alloy nanoparticles are uniformly distributed in the nitrogen-carbon nanotubes, forming an efficient catalyst system.

[0148] like Figure 2 As shown, it is the morphology of NiFeCo-NCNT catalyst, from which its mutually entangled linear structure can be clearly seen. The diameter of nitrogen carbon nanotubes is about 0.6 microns and the length is 6-15 microns.

[0149] like Fig.13 The figure shows the XRD results of NiFeCo-NCNT catalyst, which accurately depicts its crystal structure and phase composition characteristics, mainly consisting of two phases: NiFeCo solid solution and C.

Claims

1. A magnesium-based composite material containing a NiFeCo-NCNT catalyst, characterized in that: The invention comprises magnesium powder, nitrogen carbon nanotube (NCNT) and NiFeCo medium entropy alloy nanoparticles, wherein the NiFeCo medium entropy alloy nanoparticles are evenly and discretely distributed on the inner wall of NCNT.

2. A magnesium-based composite material containing a NiFeCo-NCNT catalyst according to claim 1, characterized in that: Nitrogen carbon nanotubes are coaxial or basically coaxial circular tube structures of carbon nanotubes, which are composed of layers of hexagonally arranged carbon atoms stacked one on top of the other. The diameter of nitrogen carbon nanotubes is 0.45-0.65 microns and the length is 6-15 microns. Nitrogen atoms are doped into carbon nanotubes.

3. A magnesium-based composite material containing a NiFeCo-NCNT catalyst according to claim 1, characterized in that: The size of NiFeCo mesenterometallic nanoparticles is 30-100 nanometers, and the elements are evenly distributed, forming a specific phase structure; During the ball milling process, the NiFeCo-NCNT catalyst and magnesium powder are fully physically mixed under the impact and shear force of the ball milling medium, so that the catalyst particles are effectively dispersed and fully combined in the magnesium powder matrix; The dosage of NiFeCo-NCNT catalyst and magnesium powder is 1:

9.

4. A method for preparing a magnesium-based composite material containing a NiFeCo-NCNT catalyst, characterized in that: The steps include: Step 1: Add melamine and anhydrous glucose to a deionized water solution and stir until a yellow turbid solution is obtained; Subsequently, aqueous solutions of metal nitrates of Ni, Fe and Co are mixed, stirred evenly, heated and volatilized to obtain a dry mixed powder, and then the mixed powder is added to the yellow turbid solution, stirred, heated and volatilized again to obtain a mixed dry powder and ground; Step 2: placing the ground mixed dry powder in a high temperature tube furnace for high temperature heat drying treatment under an argon atmosphere to obtain a NiFeCo-NCNT catalyst; Step 3, ball-milling the magnesium powder and the NiFeCo-NCNT catalyst and mixing them to obtain a magnesium-based composite material containing the NiFeCo-NCNT catalyst; Step 4: High temperature treatment of the magnesium-based composite material containing the NiFeCo-NCNT catalyst.

5. The method for preparing a magnesium-based composite material containing a NiFeCo-NCNT catalyst according to claim 4, characterized in that: The step 1 is specifically as follows: Set the speed of the magnetic stirrer to 450-550 r / min; Mix the aqueous solutions of metal nitrates, stir evenly and heat to 50-60°C.

6. The method for preparing a magnesium-based composite material containing a NiFeCo-NCNT catalyst according to claim 4, characterized in that: The molar mass ratio of melamine, anhydrous glucose and metal nitrate is (1-3.0): (1-1.5): (0.8-1); The metal nitrate is a mixture of Co(NO3)2·6H2O, Ni(NO3)2·6H2O and Fe(NO3)3·9H2O.

7. The method for preparing a magnesium-based composite material containing a NiFeCo-NCNT catalyst according to claim 4, characterized in that: The step 2 is specifically as follows: The conditions for high temperature heat drying in a high temperature tube furnace under argon atmosphere are as follows: the heating rate is 3-5℃min -1 , and sintered at 800-900°C for 2-3h to obtain NiFeCo-NCNT catalyst.

8. The method for preparing a magnesium-based composite material containing a NiFeCo-NCNT catalyst according to claim 4, characterized in that: The step 3 is specifically as follows: ① High-energy ball milling of magnesium powder to obtain a particle size distribution of 10 to 45 μm; ② The magnesium powder and the NiFeCo-NCNT catalyst were mixed and subjected to low-energy ball milling. The NiFeCo-NCNT catalyst and the magnesium powder were ball milled in a mass ratio of 1:

9.

9. The method for preparing a magnesium-based composite material containing a NiFeCo-NCNT catalyst according to claim 8, characterized in that: The conditions for high temperature treatment in step 4 are: The magnesium-based composite material containing the NiFeCo-NCNT catalyst was then treated in a high-temperature and high-pressure reactor; The reaction temperature is 250-300° C., 3-4 MPa of hydrogen is applied, and the hydrogenation process is carried out for 450-600 minutes. After hydrogenation, a magnesium-based composite hydrogen storage material containing a NiFeCo-NCNT catalyst is obtained.

10. Use of the magnesium-based composite material containing NiFeCo-NCNT catalyst according to any one of claims 1 to 9, characterized in that: Magnesium-based composite hydrogen storage materials containing NiFeCo-NCNT catalysts are used in hydrogen energy storage and transportation, and fuel cell hydrogen supply systems.

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