Nano magnesium hydride-supporting composite material and its manufacturing method

Abstract

The present invention discloses a method for preparing a composite material carrying nano magnesium hydride, which includes the steps of adding a cationic surfactant to an aqueous dispersion of two-dimensional transition metal carbide to fold the two-dimensional transition metal carbide nanosheets and avoid stacking them again, and then washing and drying the product after drying; placing the dried product in a sealed container, evacuating it to a vacuum, raising it to a high temperature, and maintaining the temperature for a certain period of time, and then injecting high-pressure hydrogen gas into the sealed container and maintaining the temperature for a certain period of time; and finally adding the heat-treated product and dibutyl magnesium to an organic solvent to obtain a mixture, which is subjected to ultrasonic dispersion, and then stirring and heating for 12-48 h under conditions of a hydrogen pressure of 3-6 MPa and a temperature of 180-220°C, centrifuging and drying to obtain a composite material carrying nano magnesium hydride.

Description

[Technical Field]

[0001] The present invention relates to the field of solid state hydrogen storage materials, and in particular to a composite material carrying nano magnesium hydride and a method for producing the same. [Background technology]

[0002] Magnesium-based solid hydrogen storage materials are considered the most promising solid hydrogen storage materials due to their high hydrogen storage density, strong cyclic reversibility, and abundant geological reserves. However, their hydrogen absorption and desorption thermodynamic properties are too stable (the standard enthalpy of formation for the hydrogen absorption and desorption reactions is ±75 kJ / mol). Under normal circumstances, pure magnesium hydride must be heated to above 350°C to achieve hydrogen desorption. Furthermore, their kinetic properties are similarly poor, significantly limiting their practical application. Nanosizing is currently considered one of the most effective strategies for improving the hydrogen storage performance of magnesium-based hydrogen storage materials. Nanosizing magnesium-based hydrogen storage materials directly achieves larger specific surface areas, higher surface energies, and larger grain boundary densities, which provide shorter solid-state diffusion distances, lower diffusion energy barriers, and more diffusion channels for hydrogen atoms in magnesium-based hydrogen storage materials, significantly improving their kinetic properties. Numerous experimental and theoretical studies have shown that nanosizing also reduces the thermodynamic stability of magnesium-based hydrogen storage materials. However, due to their high surface energy, nanoscale particles tend to naturally aggregate and grow, leading to a rapid loss of nanostructure morphology and continuous deterioration of hydrogen storage stability. Confining nanoscale magnesium hydride / magnesium hydride in porous materials effectively inhibits nanoparticle migration, aggregation, and growth, thereby achieving stable hydrogen storage thermal and dynamic properties. Generally, carbon-based porous materials (e.g., porous activated carbon, carbon gel, graphene, and carbon nanotubes) with high specific surface area, strong chemical stability, and light weight have been widely investigated as nanoconfined support materials. However, due to their limited intrinsic catalytic effect on the hydrogen absorption and desorption processes of carbon-to-magnesium materials, their hydrogen absorption and desorption dynamic properties are difficult to achieve. Therefore, additional catalysts are usually required to achieve higher hydrogen absorption and desorption dynamic properties.Furthermore, the loading rate of magnesium hydride (magnesium) in carbon-magnesium hydride composites is usually low. Therefore, the development of support materials that can ensure adequate magnesium hydride / magnesium loading efficiency and provide good catalytic effect is very important for the development of magnesium-based hydrogen storage materials.

[0003] Two-dimensional transition metal carbides (MXenes), as novel two-dimensional materials, have been extensively studied in the fields of energy storage, catalysis, sensors, etc. Their general chemical formula is M n+1 X n T z where M is a transition metal (e.g., Ti, Zr, Hf, V, Nb, Ta, Cr, Sc, etc.), X is C, n is generally 1, 2, or 3, and T z refers to surface chemical groups (e.g., O 2- , O.H. - , F - , NH3, NH4 + Two-dimensional transition metal carbides have the advantages of large specific surface area, chemical stability, and physical stability. Furthermore, they exhibit excellent catalytic effects in the hydrogen absorption and desorption processes of magnesium-based hydrogen storage materials. Therefore, two-dimensional transition metal carbides are considered potential support materials that combine high loading rates and catalytic effects. However, due to the van der Waals forces between two-dimensional transition metal carbide (MXenes) nanosheet layers, severe interlayer stacking is likely to occur, resulting in a large loss of free surface area for anchoring nanomagnesium hydride. Furthermore, the large number of oxygen-containing functional groups on the surface of MXenes causes severe oxidation during the high-temperature hydrogen absorption and desorption processes, resulting in a deterioration of the hydrogen storage capacity and dynamic characteristics of hydrogen absorption and desorption. For these reasons, there have been no reports to date on the use of two-dimensional transition metal carbides as support materials for magnesium-based hydrogen storage materials.

[0004] Therefore, those skilled in the art strive to develop composite materials that support nano-magnesium hydride with two-dimensional transition metal carbides, which combine high magnesium hydride loading capacity and excellent hydrogen absorption and release kinetic properties. Summary of the Invention [Problem to be solved by the invention]

[0005] In view of the above-mentioned shortcomings of the prior art, the technical problem to be solved by the present invention is to provide a composite material of nano-magnesium hydride supported by two-dimensional transition metal carbide, which has excellent properties of high hydrogen storage capacity, fast hydrogen absorption and release dynamics, and strong cycle stability. [Means for solving the problem]

[0006] In order to achieve the above object, the present invention provides a method for producing a composite material carrying nano-magnesium hydride, (1) adding a cationic surfactant to an aqueous dispersion of two-dimensional transition metal carbide to fold and aggregate the two-dimensional transition metal carbide nanosheets, followed by washing and drying; Step (2) of placing the product obtained in step (1) in a sealed container, evacuating the sealed container to a vacuum, then heating the container to 600 to 1000°C and maintaining the temperature for 2 to 5 hours, and then injecting high-pressure hydrogen gas at 1 to 10 MPa into the sealed container and maintaining the temperature for 2 to 5 hours; and (3) adding the product obtained in step (2) and dibutylmagnesium to an organic solvent to obtain a mixture, ultrasonically dispersing the mixture, and then stirring and heating for 12 to 48 hours under conditions of a hydrogen pressure of 3 to 6 MPa and a temperature of 180 to 220°C, centrifuging and drying, and then obtaining a composite material carrying the nano-magnesium hydride.

[0007] Preferably, the hydrogen gas pressure in step (1) is 3 to 4.5 MPa.

[0008] Furthermore, the two-dimensional transition metal carbide in step (1) is Ti3C2T x , Ti2CT x , V2CT x , Mo3C2T x , Nb2CT x , Nb4C3T x , Ta2CT x , V4C3T x One of the following: T x is a surface chemical group, e.g., O 2- , O.H. - , F - , NH3, NH4 + etc.

[0009] Furthermore, the aqueous dispersion of the two-dimensional transition metal carbide is a monolayer dispersion or a few-layer dispersion.

[0010] Furthermore, the cationic surfactant in step (1) is a nitrogen-containing organic amine derivative.

[0011] Preferably, the cationic surfactant is hexadecyltrimethylammonium bromide (CTAB).

[0012] Furthermore, in step (1), the cationic surfactant is first dissolved in deionized water and then added to the aqueous dispersion of the two-dimensional transition metal carbide under stirring conditions. The purpose of adding the cationic surfactant is to fold the two-dimensional transition metal carbide nanosheets dispersed in water and prevent the nanosheets from stacking again, thereby reducing the risk of interlayer stacking during the drying process.

[0013] Preferably, the sealed container in step (2) is a stainless steel sealed container.

[0014] Furthermore, the temperature rise rate in step (2) is 5 to 10°C / min. The purpose of first performing heat treatment at high temperature in step (2) is to remove surfactants and oxygen-containing groups remaining in the two-dimensional transition metal carbide.

[0015] Furthermore, the organic solvent in step (3) includes one or more of cyclohexane, hexane, and heptane.

[0016] Furthermore, the ultrasonic power of the ultrasonic dispersion in step (3) is 200 W, and the ultrasonic dispersion time is 2 hours.

[0017] Furthermore, by adjusting the mass ratio of the dibutylmagnesium and the two-dimensional transition metal carbide, the mass fraction of the magnesium hydride in the composite material is controlled to 20 to 75%.

[0018] Furthermore, a method for producing a composite material carrying nano-magnesium hydride is provided, (1) adding acidified melamine to an aqueous dispersion of two-dimensional transition metal carbide to fold and aggregate the two-dimensional transition metal carbide nanosheets, followed by washing and drying; Step (2) of placing the product obtained in step (1) in a sealed container, evacuating the sealed container to a vacuum, then heating the container to 600 to 1000°C and maintaining the temperature for 2 to 5 hours, and then injecting high-pressure hydrogen gas at 1 to 10 MPa into the sealed container and maintaining the temperature for 2 to 5 hours; and (3) adding the product obtained in step (2) and dibutylmagnesium to an organic solvent to obtain a mixture, ultrasonically dispersing the mixture, and then stirring and heating for 12 to 48 hours under conditions of a hydrogen pressure of 3 to 6 MPa and a temperature of 180 to 220°C, centrifuging and drying, and then obtaining a composite material carrying the nano-magnesium hydride.

[0019] The present invention also provides a composite material supporting nano-magnesium hydride produced by the above method, wherein the nano-magnesium hydride is supported on the surface of a two-dimensional transition metal carbide, and the two-dimensional transition metal carbide nanosheets have folds.

[0020] Furthermore, the mass fraction of the magnesium hydride in the composite material is 20 to 75%.

[0021] The present invention also provides the application of nano-magnesium hydride-supported composite materials in hydrogen storage. [Effects of the Invention]

[0022] The present invention has the following technical effects: 1. Due to the role of van der Waals forces and hydrogen bonds, two-dimensional transition metal carbide nanosheets tend to spontaneously stack, which significantly reduces their specific surface area. However, in this invention, by adding a cationic surfactant, the two-dimensional transition metal carbide nanosheets are folded and aggregated, which effectively suppresses the interlayer stacking phenomenon of the two-dimensional transition metal carbide nanosheets and provides more free surface for fixing the nano-magnesium hydride, thereby increasing the magnesium hydride loading rate of the composite material. 2. Nanoscale magnesium hydride / magnesium hydride has good dynamic properties of hydrogen absorption and hydrogen release, but the nanoparticles tend to aggregate and grow during the continuous hydrogen absorption and hydrogen release process, resulting in continuous deterioration of cycle stability. However, the present invention uses two-dimensional transition metal carbide as a nano-confined carrier material, so that the nanoscale magnesium hydride is uniformly distributed on the surface of the two-dimensional transition metal carbide, and the tendency of magnesium hydride / magnesium particles to aggregate and grow during the hydrogen injection and hydrogen release process is effectively suppressed, thereby maintaining the advantage of nano-sizing. 3. The high chemical and physical stability of the two-dimensional transition metal carbide nanosheets ensures that the composite material has good structural and performance stability during the hydrogen absorption and desorption processes at high temperatures. 4. In the composite material, the two-dimensional transition metal carbide nanosheets and nano-magnesium hydride form nano-catalyst phases (e.g., TiH2) at the ipso position of the interface, which can accelerate the hydrogen absorption and desorption rates of the composite material.

[0023] Therefore, the present invention folds two-dimensional transition metal carbide nanosheets and utilizes the confinement effect of the two-dimensional transition metal carbide on nano-magnesium hydride / magnesium and the ipso-position catalytic effect on the hydrogen absorption and desorption processes of magnesium hydride / magnesium. As a result, such composite materials supporting nano-magnesium hydride on two-dimensional transition metal carbide have advantages such as high hydrogen storage density, rapid hydrogen absorption and desorption dynamic properties, and excellent cycle stability.

[0024] In the following, the concept, specific structure and technical effects of the present invention will be further described in conjunction with the drawings in order to fully understand the objectives, features and effects of the present invention. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is an XRD graph of a composite material of magnesium hydride supported by two-dimensional transition metal carbide according to one preferred embodiment of the present invention. [Figure 2] 1 is a transmission electron micrograph of a composite material of magnesium hydride supported by two-dimensional transition metal carbides according to one preferred embodiment of the present invention. [Figure 3] 1 is a scanning electron microscope view of a composite material of magnesium hydride supported by two-dimensional transition metal carbides according to one preferred embodiment of the present invention. [Figure 4] FIG. 2 is a particle size distribution diagram of nano-magnesium hydride in a composite material in which magnesium hydride is supported by two-dimensional transition metal carbide according to one preferred embodiment of the present invention. [Figure 5] 1 is a programmed temperature controlled dehydrogenation curve of a composite material of magnesium hydride supported by two-dimensional transition metal carbide according to one preferred embodiment of the present invention. [Figure 6] 1 is a hydrogen cycle release curve of a composite material supporting magnesium hydride by two-dimensional transition metal carbide according to one preferred embodiment of the present invention. [Figure 7]1 is a transmission electron micrograph of a composite material of magnesium hydride supported by two-dimensional transition metal carbides according to one preferred embodiment of the present invention. [Figure 8] FIG. 1 shows the particle size distribution of nano-magnesium hydride in a composite material of magnesium hydride supported by two-dimensional transition metal carbide according to one preferred embodiment of the present invention. [Figure 9] 1 is a transmission electron micrograph of a composite material of magnesium hydride supported by two-dimensional transition metal carbides according to one preferred embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0026] In order to make the technical contents clearer and easier to understand, the following describes several preferred embodiments of the present invention with reference to the drawings in the specification. The present invention can be embodied in many different forms of embodiments, and the protection scope of the present invention is not limited to only the embodiments described in the specification.

[0027] A method for producing a composite material carrying nano-magnesium hydride, comprising: (1) adding a cationic surfactant to an aqueous dispersion of two-dimensional transition metal carbide to fold and aggregate the two-dimensional transition metal carbide nanosheets, followed by washing and drying; Step (2) of placing the product obtained in step (1) in a sealed container, evacuating the sealed container to a vacuum, then heating the container to 600 to 1000°C and maintaining the temperature for 2 to 5 hours, and then injecting high-pressure hydrogen gas at 1 to 10 MPa into the sealed container and maintaining the temperature for 2 to 5 hours; and (3) adding the product obtained in step (2) and dibutylmagnesium to an organic solvent to obtain a mixture, ultrasonically dispersing the mixture, and then stirring and heating for 12 to 48 hours under conditions of a hydrogen pressure of 3 to 6 MPa and a temperature of 180 to 220°C, centrifuging and drying, and then obtaining a composite material carrying the nano-magnesium hydride.

[0028] In some embodiments, the two-dimensional transition metal carbide described in step (1) is Ti3C2T x, Ti2CT x , V2CT x , Mo3C2T x , Nb2CT x , Nb4C3T x , Ta2CT x and V4C3T x (T x is a surface chemical group, e.g., O 2- , O.H. - , F - , NH3, NH4 + etc.) may be any one of them.

[0029] In some embodiments, the cationic surfactant in step (1) is a nitrogen-containing organic amine derivative, preferably hexadecyltrimethylammonium bromide (CTAB).

[0030] In some embodiments, most preferably, the cationic surfactant in step (1) is first dissolved in deionized water and then added to the aqueous dispersion of the two-dimensional transition metal carbide under stirring conditions.

[0031] In some embodiments, the sealed vessel described in step (2) is a stainless steel sealed vessel.

[0032] In some embodiments, the temperature increase rate during step (2) is 5-10°C / min, and the temperature after the temperature increase may be 600°C, 700°C, 800°C, 900°C, or 1000°C.

[0033] In some embodiments, the organic solvent in step (3) can be cyclohexane, hexane, or heptane, or any mixture thereof.

[0034] In some embodiments, the ultrasonic dispersion power in step (3) is 200 W and the duration is 2 hours.

[0035] In some embodiments, the mass fraction of magnesium hydride in the composite material can be controlled to 20-75% by adjusting the mass ratio of dibutylmagnesium and two-dimensional transition metal carbide.

[0036] Example 1 Fabrication of nano-magnesium hydride supported composite material 60MgH2@Ti-MX1 by two-dimensional transition metal carbides: (1) 5 g of hexadecyltrimethylammonium bromide (CTAB) was dissolved in 100 ml of deionized water. (2) The CTAB solution prepared in step (1) was stirred under stirring conditions to obtain a Ti3C2T x The mixture was added dropwise to 500 ml of aqueous dispersion, and the reaction product was centrifuged three times to wash it. The centrifuged product was freeze-dried for 72 hours. (3) The product obtained in step (2) was placed in a sealed stainless steel container, and the sealed stainless steel container was continuously evacuated to vacuum, and then heated to 800°C at a heating rate of 5°C / min, and held at that temperature for 2 hours. Then, hydrogen gas at 3 MPa was injected, and the temperature was held for 2 hours. Finally, the product was cooled to room temperature in a furnace, and the product was designated as Ti-MX1. (4) 30 mg of Ti-MX1, 3.5 ml of a 0.5 M dibutylmagnesium heptane solution, and 40 ml of cyclohexane were added to a stainless steel high-pressure reactor with a polytetrafluoroethylene inner pot, and then subjected to ultrasonic dispersion for 2 hours, with an ultrasonic power of 200 W. (5) Hydrogen was injected into a stainless steel high-pressure reactor up to 4.5 MPa, heated to 200 °C, and reacted for 12 h under stirring conditions. Finally, the reaction was centrifuged and dried to obtain a composite material, 60MgH2@Ti-MX1, in which nano-magnesium hydride was supported by two-dimensional transition metal carbides with a magnesium hydride loading rate of 60 wt%.

[0037] The XRD graph of the composite material 60MgH2@Ti-MX supporting nano-magnesium hydride using the two-dimensional transition metal carbide prepared in this example is shown in Figure 1. From Figure 1, it can be seen that the phase of the composite material is mainly composed of magnesium hydride and Ti-MX.

[0038] The transmission electron microscope image is shown in Figure 2, the scanning electron microscope image is shown in Figure 3, and the particle size distribution is shown in Figure 4. From Figures 2 to 4, it can be seen that the two-dimensional transition metal carbide nanosheets are folded, and the nano-magnesium hydride is uniformly distributed on the surface of the two-dimensional transition metal carbide without any obvious aggregation phenomenon, and the average particle size of the magnesium hydride is 15 nm.

[0039] Hydrogen storage performance measurement of the composite material 60MgH2@Ti-MX1, in which nano-magnesium hydride is supported by two-dimensional transition metal carbide prepared in this example: Figure 5 shows the programmed temperature desorption (TPD) curves, which show that the initial hydrogen release temperature of the 60MgH2@Ti-MX1 composite is 140 °C and the hydrogen storage capacity is 4.2 wt% H2. Figure 6 shows the hydrogen cycling / desorption curve of 60MgH2@Ti-MX1 at 200 °C. From Figure 6, it can be seen that the 60MgH2@Ti-MX1 composite has excellent hydrogen cycling absorption and desorption stability.

[0040] Example 2 Fabrication of nano-magnesium hydride supported composite material 35MgH2@Ti-MX2 by two-dimensional transition metal carbides: (1) 5 g of hexadecyltrimethylammonium bromide (CTAB) was dissolved in 100 ml of deionized water. (2) The CTAB solution prepared in step (1) was stirred under stirring conditions to obtain a Ti3C2T x The mixture was added dropwise to 500 ml of aqueous dispersion, and the reaction product was centrifuged three times to wash it. The centrifuged product was freeze-dried for 72 hours. (3) The product obtained in step (2) was placed in a sealed stainless steel container, and the sealed stainless steel container was continuously evacuated to vacuum, and then heated to 600°C at a heating rate of 5°C / min and held at that temperature for 5 hours. Then, 3 MPa hydrogen gas was injected, and the temperature was held for 5 hours. Finally, the product was cooled to room temperature in a furnace, and the product was designated as Ti-MX2. (4) 30 mg of Ti-MX2, 1.3 ml of a 0.5 M dibutylmagnesium heptane solution, and 40 ml of cyclohexane were added to a stainless steel high-pressure reactor with a polytetrafluoroethylene inner pot, and then subjected to ultrasonic dispersion for 2 hours, with an ultrasonic power of 200 W. (5) Hydrogen was injected into a stainless steel high-pressure reactor up to 3 MPa, heated to 180 °C, and reacted for 24 h under stirring conditions. Finally, the reaction was centrifuged and dried to obtain a composite material, 35MgH2@Ti-MX2, in which nano-magnesium hydride was supported by two-dimensional transition metal carbides with a magnesium hydride loading rate of 35 wt%.

[0041] The transmission electron microscope image of the composite material 35MgH2@Ti-MX2 supporting nano-magnesium hydride using the two-dimensional transition metal carbide produced in this example is shown in Figure 7, and the particle size distribution is shown in Figure 8. From Figures 7 and 8, it can be seen that the two-dimensional transition metal carbide nanosheets are folded, and the nano-magnesium hydride in 35MgH2@Ti-MX2 is uniformly distributed on the surface of the two-dimensional transition metal carbide, with an average particle size of approximately 8 nm.

[0042] Example 3 Fabrication of nano-magnesium hydride supported composite material 60MgH2@Ti-MX3 by two-dimensional transition metal carbides: (1) 1.5 g of acidified melamine was dissolved in 200 ml of deionized water. (2) The melamine solution prepared in step (1) was stirred under stirring conditions to give a concentration of 2 mg / ml of Ti3C2T x The mixture was added dropwise to 500 ml of aqueous dispersion, and the reaction product was centrifuged three times to wash it. The centrifuged product was freeze-dried for 72 hours. (3) The product obtained in step (2) was placed in a sealed stainless steel container, and the sealed stainless steel container was continuously evacuated to vacuum, and then heated to 1000°C at a heating rate of 10°C / min and held at that temperature for 3 h. Then, hydrogen gas was injected at 4.5 MPa, and the temperature was held for 2 h. Finally, the product was cooled to room temperature in a furnace, and the product was designated as Ti-MX3. (4) 30 mg of Ti-MX3, 3.5 ml of a 0.5 M dibutylmagnesium heptane solution, and 40 ml of cyclohexane were added to a stainless steel high-pressure reactor with a polytetrafluoroethylene inner pot, and probe ultrasonic dispersion was carried out for 2 hours, with an ultrasonic power of 200 W. (5) Hydrogen was injected into a stainless steel high-pressure reactor up to 6 MPa, heated to 220 °C, and reacted for 12 h under stirring conditions. Finally, the mixture was centrifuged and dried to obtain a composite material, 60MgH2@Ti-MX3, in which nano-magnesium hydride was supported by two-dimensional transition metal carbides with a magnesium hydride loading rate of 60 wt%.

[0043] The transmission electron microscope image of the composite material 60MgH2@Ti-MX3, which supports nano-magnesium hydride using the two-dimensional transition metal carbide prepared in this example, is shown in Figure 9. Figure 9 shows that the two-dimensional transition metal carbide nanosheets are folded, and the nano-magnesium hydride in 60MgH2@Ti-MX3 is uniformly distributed on the surface of the two-dimensional transition metal carbide, with an average particle size of approximately 17 nm.

[0044] The above is a detailed description of the preferred specific embodiments of the present invention. It should be understood that those skilled in the art can make many modifications and changes according to the concept of the present invention without any creative work. Therefore, any technical means that those skilled in the art can obtain according to the concept of the present invention through logical analysis, reasoning, or limited experiments based on the prior art should fall within the scope of protection determined by the claims. The inventions described in the original claims of this application are set forth below. [1] A method for producing a composite material supporting nano-magnesium hydride, comprising: step (1) adding a cationic surfactant to an aqueous dispersion of two-dimensional transition metal carbide to fold two-dimensional transition metal carbide nanosheets, followed by washing and drying; step (2) placing the product obtained in step (1) into a sealed container, evacuating the sealed container to a vacuum, then heating the container to 600-1000°C and maintaining the temperature for 2-5 hours, and then injecting hydrogen gas at 1-10 MPa into the sealed container and maintaining the temperature for 2-5 hours; and step (3) adding the product obtained in step (2) and dibutylmagnesium to an organic solvent to obtain a mixture, ultrasonically dispersing the mixture, stirring and heating for 12-48 hours under conditions of a hydrogen pressure of 3-6 MPa and a temperature of 180-220°C, centrifuging, drying, and then obtaining the composite material supporting nano-magnesium hydride. [2] The two-dimensional transition metal carbide in step (1) is Ti 3 C 2 T x , Ti 2 CT x 、V 2 CT x , Mo 3 C 2 Tx , Nb 2 CT x , Nb 4 C 3 T x , Ta 2 CT x and V 4 C 3 T x [1] A method for producing a composite material carrying nano-magnesium hydride, characterized in that the nano-magnesium hydride is any one of the following: [3] The method for producing a composite material supporting nano-magnesium hydride according to [1], wherein the cationic surfactant is a nitrogen-containing organic amine derivative. [4] The method for producing a composite material supporting nano-magnesium hydride according to [3], wherein the nitrogen-containing organic amine derivative is hexadecyltrimethylammonium bromide. [5] The method for producing a composite material supporting nano-magnesium hydride according to [1], characterized in that in step (1), the cationic surfactant is first dissolved in deionized water and then added to the aqueous dispersion of the two-dimensional transition metal carbide under stirring conditions. [6] The method for producing a composite material carrying nano-magnesium hydride according to [1], characterized in that the temperature rise rate during step (2) is 5 to 10°C / min. [7] The method for producing a composite material supporting nano-magnesium hydride according to [1], characterized in that the organic solvent in step (3) includes one or more of cyclohexane, hexane, and heptane. [8] A method for producing a composite material supporting nano-magnesium hydride, comprising: step (1) adding acidified melamine to an aqueous dispersion of two-dimensional transition metal carbide to fold two-dimensional transition metal carbide nanosheets, followed by washing and drying; step (2) placing the product obtained in step (1) into a sealed container, evacuating the sealed container to a vacuum, heating the container to 600-1000°C and maintaining the temperature for 2-5 hours, and then injecting hydrogen gas at 1-10 MPa into the sealed container and maintaining the temperature for 2-5 hours; and step (3) adding the product obtained in step (2) and dibutylmagnesium to an organic solvent to obtain a mixture, ultrasonically dispersing the mixture, stirring and heating under conditions of a hydrogen pressure of 3-6 MPa and a temperature of 180-220°C for 12-48 hours, centrifuging and drying, and thereby obtaining the composite material supporting nano-magnesium hydride. [9] A composite material carrying nano-magnesium hydride produced by the method according to any one of [1] to [8], wherein the nano-magnesium hydride is carried on the surface of a two-dimensional transition metal carbide, and the nanosheets of the two-dimensional transition metal carbide are folded.

[10] The composite material supporting nano-magnesium hydride according to [9], characterized in that the mass fraction of the magnesium hydride in the composite material is 20 to 75%.

[11] The application of nano-magnesium hydride supported composite materials [9] or

[10] in hydrogen storage.

Claims

1. A method for producing a composite material supporting nano-magnesium hydride, comprising: step (1) of adding a cationic surfactant to an aqueous dispersion of two-dimensional transition metal carbide to fold two-dimensional transition metal carbide nanosheets, followed by washing and drying; step (2) of placing the product obtained in step (1) into a sealed container, evacuating the sealed container to a vacuum, then heating the container to 600-1000°C and maintaining the temperature for 2-5 hours, then injecting hydrogen gas at 1-10 MPa into the sealed container and maintaining the temperature for 2-5 hours; and step (3) of adding the product obtained in step (2) and dibutylmagnesium to an organic solvent to obtain a mixture, ultrasonically dispersing the mixture, stirring and heating for 12-48 hours under conditions of a hydrogen pressure of 3-6 MPa and a temperature of 180-220°C, centrifuging and drying, and then obtaining the composite material supporting nano-magnesium hydride.

2. The two-dimensional transition metal carbide in the step (1) is Ti ３ C ２ T ｘ , Ti ２ CT ｘ , V ２ CT ｘ , Mo ３ C ２ T ｘ , Nb ２ CT ｘ , Nb ４ C ３ T ｘ , Ta ２ CT ｘ and V ４ C ３ T ｘ 2. The method for producing a composite material carrying nano-magnesium hydride according to claim 1, characterized in that the nano-magnesium hydride is any one of the following:

3. 2. The method for producing a composite material carrying nano-magnesium hydride according to claim 1, wherein the cationic surfactant is a nitrogen-containing organic amine derivative.

4. 4. The method for producing a composite material carrying nano-magnesium hydride according to claim 3, wherein the nitrogen-containing organic amine derivative is hexadecyltrimethylammonium bromide.

5. The method for producing a composite material supporting nano-magnesium hydride according to claim 1, characterized in that in step (1), the cationic surfactant is first dissolved in deionized water and then added to the aqueous dispersion of the two-dimensional transition metal carbide under stirring conditions.

6. The temperature increase rate during step (2) is 5 to 10°C / min, or 2. The method for producing a composite material carrying nano-magnesium hydride according to claim 1, wherein the organic solvent in step (3) comprises one or more of cyclohexane, hexane, and heptane.

7. A method for producing a composite material supporting nano-magnesium hydride, comprising: step (1) of adding melamine to an aqueous dispersion of two-dimensional transition metal carbide to fold two-dimensional transition metal carbide nanosheets, followed by washing and drying; step (2) of placing the product obtained in step (1) into a sealed container, evacuating the sealed container to a vacuum, then heating the container to 600-1000°C and maintaining the temperature for 2-5 hours, and then injecting hydrogen gas at 1-10 MPa into the sealed container and maintaining the temperature for 2-5 hours; and step (3) of adding the product obtained in step (2) and dibutylmagnesium to an organic solvent to obtain a mixture, ultrasonically dispersing the mixture, stirring and heating for 12-48 hours under conditions of a hydrogen pressure of 3-6 MPa and a temperature of 180-220°C, centrifuging and drying, and then obtaining the composite material supporting nano-magnesium hydride.

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