Sulfur-nitrogen doped MXene hydrogen storage material catalyst, hydrogen storage material containing the catalyst and preparation method

Abstract

The present invention relates to a sulfur-nitrogen doped MXene hydrogen storage material catalyst, a hydrogen storage material containing the catalyst and a preparation method thereof, and belongs to the field of hydrogen storage technology. The hydrogen storage material catalyst is sulfur-nitrogen doped Nb2CT x The hydrogen storage catalyst was ball-milled with magnesium hydride to produce a composite hydrogen storage material. This catalyst exhibits excellent catalytic activity in the absorption and desorption processes of magnesium hydride. In hydrogen desorption kinetics testing, the composite hydrogen storage material produced using this catalyst and magnesium hydride released 5.32 wt.% of hydrogen within 5 minutes at 275°C, and absorbed 5.08 wt.% of hydrogen within 2 minutes at 150°C. Furthermore, the initial desorption temperature of this composite hydrogen storage material was 105.48°C lower than that of pure magnesium hydride. The catalyst preparation method is simple, and the raw materials are readily available, making it suitable for scale-up production.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydrogen storage, and relates to a sulfur-nitrogen doped MXene hydrogen storage material catalyst, a hydrogen storage material containing the catalyst, and a preparation method. Background Art

[0002] Hydrogen is considered an extremely attractive energy carrier because it is a large-scale storable, sustainable and renewable energy source. However, the practical application of hydrogen energy still requires breakthroughs in low-cost hydrogen production, fuel cells that efficiently convert hydrogen into electricity, and safe and compact hydrogen storage technologies. The density of hydrogen at room temperature and pressure is only 0.089 kg·m -3 Therefore, safe and tight storage of hydrogen is crucial for the application of hydrogen energy.

[0003] Solid-state hydrogen storage is a method that has been widely researched and developed because it is safer and more compact than other methods (such as storage in high-pressure gas cylinders or insulated tanks). Currently, solid-state hydrogen storage has multiple branches, including metal hydrides, coordinated metal hydrides, amino compounds, and new carbon-based adsorbents. Magnesium-based hydrogen storage materials are a very promising metal-based hydrogen storage material. Their theoretical hydrogen storage capacity can reach 7.6wt.%, which is higher than the light-duty vehicle hydrogen source indicator (5.5wt.%) proposed by the US Department of Energy (DOE). They also have a slow hydrogen desorption platform and good reversibility. At the same time, they are lightweight, abundant in resources, and inexpensive. However, their practical application is greatly limited by their poor hydrogen absorption and desorption kinetics and high hydrogen desorption temperature. Therefore, researchers have improved the performance of magnesium-based hydrogen storage materials to a certain extent by adding catalysts, surface treatment modification, nano-sizing, and preparing composite hydrogen storage materials. However, their desorption temperature is higher than the actual application temperature, and the problem of poor hydrogen absorption and desorption kinetics still exists.

[0004] In recent years, two-dimensional layered MXenes have shown great potential in many fields such as catalysis, sensors, conversion, energy storage, gas adsorption and electronic devices due to their layered structure, relatively large surface area, remarkable chemical durability and high electrical conductivity. n+1 X n T x , where M is a transition metal, such as S C , Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, etc., X is carbon, nitrogen or carbon nitrogen, n = 1, 2, 3, T represents a surface group, such as O 2- , OH - , or F -Some researchers have already used MXenes as catalysts to improve the performance of hydrogen storage materials. By modifying the MXenes themselves, their catalytic performance has been further enhanced. However, despite the excellent capacity of MXenes-based materials (such as Ti2C) (up to 8.5 wt.% according to density functional theory), their slow hydrogen absorption and desorption kinetics still greatly restrict their hydrogen storage applications. Therefore, their potential in hydrogen storage applications still needs to be further explored. Summary of the Invention

[0005] In view of this, one of the objectives of the present invention is to provide a sulfur-nitrogen doped Nb2CT x Hydrogen storage material catalyst; the second purpose is to provide sulfur and nitrogen doped Nb2CT x A method for preparing a hydrogen storage material catalyst; a third purpose is to provide a hydrogen storage material containing the catalyst; a fourth purpose is to provide a method for preparing a hydrogen storage material containing the catalyst.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] 1. A sulfur-nitrogen doped MXene hydrogen storage material catalyst, wherein the hydrogen storage material catalyst is sulfur-nitrogen doped Nb2CT x .

[0008] Preferably, the nitrogen doping amount accounts for 5-7 wt.% of the total mass of the hydrogen storage catalyst, and the sulfur doping amount accounts for 0.5-1.2 wt.% of the total mass of the hydrogen storage catalyst.

[0009] 2. A method for preparing a sulfur-nitrogen-doped MXene hydrogen storage material catalyst, the preparation method being as follows:

[0010] (1) LiF was dissolved in concentrated hydrochloric acid to obtain an etching solution, and then Nb2AlC was placed in the etching solution, subjected to hydrothermal reaction, centrifuged and washed, and finally vacuum dried to obtain Nb2CT. x ;

[0011] (2) Dissolve thiourea in ethanol and then add the Nb2CT prepared in step (1) x , mixed and dried in vacuum to obtain Nb2CT x and thiourea, and calcining the mixture in a tube furnace under a protective atmosphere.

[0012] Preferably, in step (1), the mass volume ratio of LiF, Nb2AlC and concentrated hydrochloric acid is: 1-1.4:0.8-1.2:10-30, g:g:mL; the hydrothermal reaction is specifically: reacting in a reactor at 100-150°C for 12-36 hours; the centrifugal washing is specifically: centrifuging and washing with deionized water at a speed of 3000-8000 rpm until the mixed system is neutral; the vacuum drying is specifically: vacuum drying at 60-100°C for 8-16 hours.

[0013] Preferably, in step (2), the Nb2CT x , the mass volume ratio of thiourea and ethanol is: 10:10~40:1~2, mg:mg:mL; the vacuum drying is specifically: vacuum drying at 60~100℃ for 8~16h; the calcination is specifically: calcining at 200~600℃ in an argon atmosphere in a tubular furnace for 1~4h.

[0014] 3. A MgH2-sulfur-nitrogen doped Nb2CT x Composite hydrogen storage material, calculated by mass percentage, the composite hydrogen storage material comprises: sulfur-nitrogen doped Nb2CT x 1wt.%~15wt.%, MgH2 85wt.%~99wt.%.

[0015] Preferably, the composite hydrogen storage material comprises, by mass percentage: sulfur-nitrogen doped Nb2CT x 3wt.%~10wt.%, MgH2 90wt.%~97wt.%.

[0016] Preferably, the composite hydrogen storage material comprises, by mass percentage: sulfur-nitrogen doped Nb2CT x 4wt.%~6wt.%, MgH2 94wt.%~96wt.%.

[0017] 4. A MgH2-sulfur-nitrogen doped Nb2CT x The preparation method of the composite hydrogen storage material is as follows: MgH2 and sulfur-nitrogen doped Nb2CT x Under argon atmosphere, ball milling was performed intermittently at a speed of 200-800 rpm in both forward and reverse rotations for 8-24 h at a ball-to-material ratio of 10-60:1.

[0018] Preferably, the forward and reverse intermittent ball milling is specifically: after each 5 to 20 minutes of ball milling, there is a pause of 5 to 30 minutes.

[0019] The beneficial effects of the present invention are: the present invention provides sulfur-nitrogen doped Nb2CT xA hydrogen storage material catalyst, a hydrogen storage material containing the catalyst, and a preparation method thereof. The catalyst is a two-dimensional layered structure particle with a particle length between 5 and 30 μm, a nitrogen doping amount of 5 to 7 wt.%, and a sulfur doping amount of 0.5 to 1.2 wt.%. The catalyst has an excellent catalytic effect on the hydrogen absorption and desorption process of magnesium hydride because the Nb2CT with M2X structure x MXene has a small number of structural layers, so it has a high specific surface area, providing more catalytic active sites, which is conducive to the smooth progress of hydrogen absorption and desorption reactions. In addition, the in-situ generated Nb and NbO2 substances can lengthen the Mg-H bond and promote the rapid release of hydrogen. The doping of S elements mainly plays a role in expanding the Nb2CT x The effect of interlayer spacing, excessive doping will destroy the layered structure and is not conducive to the transmission and transfer of electrons. When the doping amount is 0.5-1.2wt.%, Nb2CT x It can still maintain the layered structure; the doping of N element mainly plays a role in improving Nb2CT x The role of conductivity, since thiourea acts as both S and N sources, the amount of N doping is determined by the S element. The doping of N and S elements further enhances the conductivity of Nb2CT x The multivalent forms of Nb elements (NbO2, Nb-C, Nb) on the surface promote the Mg 2+ The ability to transfer electrons between hydrogen and H- effectively accelerates the dissociation of hydrogen molecules and the breaking of magnesium hydrogen bonds, and has a good catalytic effect on magnesium hydride. The composite hydrogen storage material prepared with this catalyst and magnesium hydride has a particle size between 1 and 15 μm, and sulfur and nitrogen doped Nb2CT x The MgH2 is evenly distributed on the surface of the MgH2 particles, providing evenly distributed active catalytic sites for the subsequent hydrogen absorption and desorption process of the MgH2 particles, allowing MgH2 to quickly and efficiently release and absorb hydrogen through these sites. Therefore, in the hydrogen desorption kinetics test, MgH2 can release 5.32wt.% of hydrogen within 5 minutes at 275℃, and absorb 5.08wt.% of hydrogen within 2 minutes at 150℃. In addition, the initial desorption temperature of the composite hydrogen storage material is 105.48℃ lower than that of pure magnesium hydride, which shows that the sulfur-nitrogen-doped Nb2CT x The catalyst has an excellent catalytic effect on the hydrogen absorption and desorption process of magnesium hydride. The preparation method of the catalyst is simple, and the raw materials are readily available, making it suitable for large-scale production.

[0020] Other advantages, objects, and features of the present invention will be described in part in the following description and, in part, will be apparent to those skilled in the art upon examination of the following description or may be learned from practice of the present invention. The objects and other advantages of the present invention may be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below with reference to the accompanying drawings, in which:

[0022] Figure 1 Nb2CT prepared in Example 1 x SEM images of

[0023] Figure 2 The sulfur-nitrogen doped Nb2CT prepared in Example 1 x SEM images of

[0024] Figure 3 MgH2+5wt.%Nb2CT prepared in Example 5 x SEM image of / SN composite hydrogen storage material;

[0025] Figure 4 MgH2 + y wt.% Nb2CT prepared in Examples 4-6 x TPD curves of ball-milled MgH2 prepared in / SN (y=3, 5, 10) composite hydrogen storage materials and comparative examples;

[0026] Figure 5 MgH2+5wt.%Nb2CT prepared in Example 5 x Hydrogen release curves at 275°C of ball-milled MgH2 prepared from / SN composite hydrogen storage materials and comparative examples;

[0027] Figure 6 MgH2+5wt.%Nb2CT prepared in Example 5 x Hydrogen absorption curves of ball-milled MgH2 at 150 °C prepared from / SN composite hydrogen storage materials and comparative examples;

[0028] Figure 7 MgH2+5wt.%Nb2CT prepared in Example 6 x Nb3d XPS patterns of / SN composite hydrogen storage materials in different states. DETAILED DESCRIPTION

[0029] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0030] Example 1

[0031] Preparation of sulfur-nitrogen doped Nb2CT x

[0032] (1) 1 g of LiF was dissolved in 20 mL of 12 mol / L concentrated hydrochloric acid to obtain an etching solution. 1 g of Nb2AlC was then placed in the etching solution and reacted in a 100 mL autoclave at 125 °C for 24 h. The mixture was then centrifuged and washed with deionized water at 5000 rpm until the mixture was neutral. Finally, the mixture was vacuum dried at 60 °C for 12 h to obtain Nb2CT. x ;

[0033] (2) Dissolve 1200 mg of thiourea in 50 mL of ethanol and stir in a 60 °C water bath until the thiourea dissolves. Then add 300 mg of Nb2CT prepared in step (1). x After stirring for 1 h, the mixture was dried under vacuum at 80 ° C for 12 h to obtain Nb2CT x The mixture was placed in a tube furnace under an argon atmosphere and calcined at 400 ° C for 3 h to obtain sulfur-nitrogen doped Nb2CT x , wherein the S doping amount is 0.69wt.%, and the N doping amount is 6.39wt.%.

[0034] The Nb2CT prepared were observed by scanning electron microscopy. x and sulfur-nitrogen-doped Nb2CT x To characterize, Figure 1 Nb2CT x From the SEM image, we can see that Nb2CT x It is a typical two-dimensional layered structure particle with a particle length between 5-30μm. Figure 2 Sulfur-nitrogen doped Nb2CT x From the SEM image, we can see that after sulfur and nitrogen doping, Nb2CT x It still maintains a two-dimensional layered structure with a high specific surface area, thus providing more catalytic active sites. Table 1 shows the sulfur-nitrogen doped Nb2CT under scanning electron microscopy. x The mass ratio of each element in .

[0035] Table 1 Sulfur and nitrogen doped Nb2CT in Example 1 x The mass ratio of each element in

[0036] C N S Nb 25.72wt.% 6.39wt.% 0.69wt.% 67.2wt.%

[0037] Example 2

[0038] Preparation of sulfur-nitrogen doped Nb2CT x

[0039] (1) 1 g of LiF was dissolved in 30 mL of 12 mol / L concentrated hydrochloric acid to obtain an etching solution. 1.2 g of Nb2AlC was then placed in the etching solution and reacted in a 100 mL autoclave at 100 °C for 36 h. The mixture was then centrifuged and washed with deionized water at 3000 rpm until the mixture was neutral. Finally, the mixture was vacuum dried at 80 °C for 16 h to obtain Nb2CT. x ;

[0040] (2) Dissolve 300 mg of thiourea in 30 mL of ethanol and stir in a 60 °C water bath until the thiourea dissolves. Then add 300 mg of Nb2CT prepared in step (1). x After stirring for 1 h, the mixture was dried under vacuum at 60 ° C for 16 h to obtain Nb2CT x The mixture was placed in a tube furnace under an argon atmosphere and calcined at 600 ° C for 1 h to obtain sulfur-nitrogen doped Nb2CT x , wherein the S doping amount is 0.58wt.%, and the N doping amount is 5.64wt.%.

[0041] Example 3

[0042] Preparation of sulfur-nitrogen doped Nb2CT x

[0043] (1) 1.4 g of LiF was dissolved in 10 mL of 12 mol / L concentrated hydrochloric acid to obtain an etching solution. 0.8 g of Nb2AlC was then placed in the etching solution and reacted in a 100 mL autoclave at 150 °C for 12 h. The mixture was then centrifuged and washed with deionized water at 8000 rpm until the mixture was neutral. Finally, the mixture was vacuum dried at 100 °C for 8 h to obtain Nb2CT. x ;

[0044] (2) Dissolve 750 mg of thiourea in 60 mL of ethanol and stir in a 60 °C water bath until the thiourea dissolves. Then add 300 mg of Nb2CT prepared in step (1). x After stirring for 1 hour, the mixture was dried under vacuum at 100 °C for 8 hours to obtain Nb2CT x The mixture was placed in a tube furnace under an argon atmosphere and calcined at 200 ° C for 4 h to obtain sulfur-nitrogen doped Nb2CT x , wherein the S doping amount is 0.76wt.%, and the N doping amount is 6.67wt.%.

[0045] Example 4

[0046] Preparation of MgH2-3wt.% sulfur and nitrogen doped Nb2CT x Composite hydrogen storage material (MgH2+3wt.%Nb2CT x / SN composite hydrogen storage material)

[0047] MgH2 and the sulfur-nitrogen doped Nb2CT prepared in Example 1 were mixed in a vacuum glove box. x Weigh and mix in a mass ratio of 97:3, with a total mass of 1 g, then pour the mixture into a ball mill jar with a ball-to-material ratio of 20:1 between the mixture and 304 stainless steel balls. Fill the ball mill jar with 0.2 MPa argon and install it on a high-energy ball mill. Run it forward at 400 rpm for 10 minutes, rest for 10 minutes, then reverse for 10 minutes, rest for 10 minutes. The effective ball milling time is 10 hours.

[0048] Example 5

[0049] Preparation of MgH2-5wt.% sulfur and nitrogen doped Nb2CT x Composite hydrogen storage material (MgH2+5wt.%Nb2CT x / SN composite hydrogen storage material)

[0050] The difference from Example 4 is that MgH2 and the sulfur-nitrogen doped Nb2CT prepared in Example 1 are added. x MgH2+5wt.%Nb2CT was prepared by weighing and mixing them in a mass ratio of 95:5 with a total mass of 1g. x / SN composite hydrogen storage material.

[0051] The MgH2+5wt.%Nb2CT prepared in Example 5 was observed by scanning electron microscopy. x / SN composite hydrogen storage materials were characterized. Figure 3 MgH2+5wt.%Nb2CT x The SEM image of the MgH / SN composite hydrogen storage material shows that its average particle size is 1 to 15 μm, which is significantly smaller than that of the original magnesium hydride (30 to 50 μm). The reduction in particle size is beneficial to improving the hydrogen absorption and desorption kinetics of magnesium hydride. The reason is that when the magnesium hydride particle size is greatly reduced, its specific surface area also increases. The increase in specific surface area increases the reactivity of the particles, making the release and absorption of hydrogen easier. In addition, the reduction in particle size also shortens the diffusion path of hydrogen atoms from the interior to the surface of the particle or from the surface to the interior, thereby accelerating the release and absorption of hydrogen.

[0052] Example 6

[0053] Preparation of MgH2-10wt.% sulfur and nitrogen doped Nb2CT x Composite hydrogen storage material (MgH2+10wt.%Nb2CT x / SN composite hydrogen storage material)

[0054] The difference from Example 4 is that MgH2 and the sulfur-nitrogen doped Nb2CT prepared in Example 1 are added.x MgH2+10wt.%Nb2CT was prepared by weighing and mixing them in a mass ratio of 90:10 with a total mass of 1g. x / SN composite hydrogen storage material.

[0055] Comparative Example

[0056] Preparation of ball-milled MgH2

[0057] In a vacuum glove box, pour 1g of MgH2 into a ball mill jar with a ball-to-material ratio of MgH2 to 304 stainless steel balls of 20:1. Fill the ball mill jar with 0.2Mpa argon and install it on a high-energy ball mill. Run it forward at 400rpm for 10min, rest for 10min, then reverse for 10min, rest for 10min. The effective ball milling time is 10h.

[0058] In the glove box, 200 mg of the composite hydrogen storage materials (MgH2+y wt.% Nb2CT x / SN (y = 3, 5, 10)) and the ball-milled MgH2 prepared in the comparative example were placed in a special sample tube of a high-pressure gas adsorption-desorption instrument, and then loaded into the instrument for TPD testing. The results are shown in FIG. Figure 4 As shown in the figure, it can be seen that as sulfur and nitrogen doped Nb2CT x The initial hydrogen release temperature of MgH2 decreases to varying degrees with the increase of catalyst addition amount. The composite hydrogen storage materials (MgH2+y wt.% Nb2CT x / SN (y = 3, 5, 10)) were 248.05 ° C, 212.58 ° C and 209.91 ° ​​C, respectively, which were 70.01 ° C, 105.48 ° C and 108.15 ° C lower than those of the ball-milled MgH2 prepared in the comparative example. x / SN composite hydrogen storage material exhibits the best catalytic effect: on the one hand, compared with MgH2+3wt.%Nb2CT x / SN composite hydrogen storage material, its initial dehydrogenation temperature dropped by 35.47℃; on the other hand, compared with MgH2+10wt.%Nb2CT x / SN composite hydrogen storage material, although the initial hydrogen desorption temperature is not much different (2.67℃), its hydrogen desorption amount is larger and the hydrogen desorption rate is faster.

[0059] MgH2+5wt.%Nb2CT prepared in Example 5 x The ball-milled MgH2 prepared in the SN / SN composite hydrogen storage material and the comparative example was tested for hydrogen release performance at 275°C and hydrogen absorption performance at 150°C. The results are shown in Figure 2. Figure 5 and Figure 6 As shown in Table 2. Among them, Figure 5 The hydrogen release curves of two hydrogen storage materials at 275°C are shown in Figure 2. Figure 6 The hydrogen release curves of the two hydrogen storage materials at 150°C are shown in Figure 2. Figure 5 It can be seen that ball milling MgH2 can only release about 0.03wt.% hydrogen in 5 minutes, and MgH2+5wt.%Nb2CT x The / SN composite hydrogen storage material can release 5.31wt.% hydrogen in 5 minutes, which is nearly 177 times the amount of hydrogen released by ball-milled MgH2, indicating that sulfur-nitrogen doped Nb2CT x The addition of hydrogen storage catalyst can significantly increase the hydrogen release rate of magnesium hydride. Figure 6 It can be seen that after hydrogen release, MgH2+5wt.%Nb2CT x The / SN composite hydrogen storage material can absorb about 5.08wt.% of hydrogen in 120s at 150℃, while ball-milled MgH2 can only absorb 3.51wt.% of hydrogen under the same conditions, and can only absorb 4.15wt.% of hydrogen in 20 minutes. The above results show that sulfur-nitrogen doped Nb2CT x The addition of catalyst can promote the dissociation and recombination of hydrogen molecules, making MgH2 have a fast hydrogen absorption and desorption rate.

[0060] Table 2MgH2+5wt.%Nb2CT x / SN composite hydrogen storage material and ball-milled MgH2 hydrogen absorption and desorption performance test data

[0061]

[0062] MgH2+5wt.%Nb2CT prepared in Example 5 x The Nb 3d spectrum of the / SN composite hydrogen storage material in different states was analyzed. Figure 7 As shown by Figure 7 It can be seen that the phase compositions of the ball-milled state, dehydrogenation state, hydrogen absorption state and cyclic dehydrogenation state are Nb, Nb-C and Nb oxides, among which the ball-milled state is Nb2O5, while the other three states are NbO2, indicating that after dehydrogenation, the high-valent Nb2O5 is reduced to the low-valent NbO2 and the subsequent hydrogen absorption and dehydrogenation cycles remain unchanged. In general, the phase compositions during the hydrogen absorption and dehydrogenation cycle are Nb, Nb-C and NbO2, among which the presence of Nb-C indicates that sulfur-nitrogen doped Nb2CT x The catalyst still maintains a stable two-dimensional layered structure during the hydrogen absorption and desorption process of MgH2, providing a large number of active catalytic sites for MgH2, which is conducive to the hydrogen absorption and desorption reaction; at the same time, the in-situ generated Nb and NbO2 substances can lengthen the Mg-H bond and promote the rapid release of hydrogen; in addition, the doping of N and S elements can further enhance the Nb2CTx The multivalent forms of Nb elements (NbO2, Nb-C, Nb) on the surface promote the Mg 2+ With H - The ability of electron transfer between the two species can effectively accelerate the dissociation of hydrogen molecules and the breaking of magnesium-hydrogen bonds.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions, which should all be included in the scope of the claims of the present invention.

Claims

1. A MgH2-sulfur-nitrogen doped Nb2CT x A composite hydrogen storage material, characterized in that The composite hydrogen storage material comprises, by mass percentage, sulfur-nitrogen doped Nb2CT x 1wt.%~15wt.%, MgH2 85wt.%~99wt.%; the nitrogen doping amount accounts for the sulfur and nitrogen doped Nb2CT x 5~7wt.% of the total mass of the sulfur doping amount accounts for the sulfur-nitrogen doped Nb2CT x 0.5~1.2wt.% of the total mass.

2. The MgH2-sulfur-nitrogen doped Nb2CT according to claim 1 x A composite hydrogen storage material, characterized in that The composite hydrogen storage material comprises, by mass percentage, sulfur-nitrogen doped Nb2CT x 3wt.%~10wt.%, MgH2 90wt.%~97wt.%.

3. The MgH2-sulfur-nitrogen doped Nb2CT according to claim 1 x A composite hydrogen storage material, characterized in that The composite hydrogen storage material comprises, by mass percentage, sulfur-nitrogen doped Nb2CT x 4wt.%~6wt.%, MgH2 94wt.%~96wt.%.

4. The MgH2-sulfur-nitrogen doped Nb2CT according to any one of claims 1 to 3 x A composite hydrogen storage material, characterized in that The sulfur-nitrogen doped Nb2CT x The preparation method is as follows: (1) LiF is dissolved in concentrated hydrochloric acid to obtain an etching solution, and then Nb2AlC is placed in the etching solution. After hydrothermal reaction, centrifugal washing is performed, and finally vacuum drying is performed to obtain Nb2CT. x ; (2) Dissolve thiourea in ethanol and then add Nb2CT prepared in step (1) x , mixed and dried in vacuum to obtain Nb2CT x and thiourea, and calcining the mixture in a tube furnace under a protective atmosphere.

5. The MgH2-sulfur-nitrogen doped Nb2CT according to claim 4 x A composite hydrogen storage material, characterized in that In step (1), the mass volume ratio of LiF, Nb2AlC and concentrated hydrochloric acid is: 1~1.4:0.8~1.2:10~30, g:g:mL; the hydrothermal reaction is specifically: reacting in a reactor at 100~150°C for 12~36 hours; the centrifugal washing is specifically: centrifuging and washing with deionized water at a speed of 3000~8000 rpm until the mixed system is neutral; the vacuum drying is specifically: vacuum drying at 60~100°C for 8~16 hours.

6. The MgH2-sulfur-nitrogen doped Nb2CT according to claim 4 x Composite hydrogen storage material, step (2), the Nb2CT x , the mass volume ratio of thiourea and ethanol is: 10:10~40:1~2, mg:mg:mL; the vacuum drying is specifically: vacuum drying at 60~100℃ for 8~16h; the calcination is specifically: calcining at 200~600℃ in an argon atmosphere in a tubular furnace for 1~4h.

7. The MgH2-sulfur-nitrogen doped Nb2CT according to claim 1 x The method for preparing a composite hydrogen storage material is characterized in that: The preparation method is as follows: MgH2 and sulfur and nitrogen doped Nb2CT x Under argon atmosphere, ball milling was performed intermittently at a ball-to-material ratio of 10-60:1 and a speed of 200-800 rpm in both forward and reverse directions for 8-24 h.

8. The preparation method according to claim 7, wherein The intermittent ball milling in the forward and reverse directions is specifically as follows: after each ball milling for 5 to 20 minutes, pause for 5 to 30 minutes.

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