A preparation method of magnesium-based hydrogen storage material and magnesium-based hydrogen storage material

Abstract

The present invention provides a method for preparing a magnesium-based hydrogen storage material and a magnesium-based hydrogen storage material. The method comprises the following steps: introducing hydroxyl groups onto the surface of TiO2 using a hydrothermal method to obtain TiO2 nanotubes, grafting aminopropylsiloxane onto the TiO2 surface to obtain modified TiO2 nanotubes; introducing reduced graphene oxide into the modified TiO2 nanotubes to obtain a graphene@TiO2 nanocomposite catalyst; and introducing the graphene@TiO2 nanocomposite catalyst into nanomagnesium particles using a dry method and a wet ball milling method using cyclohexane as a solvent to obtain a magnesium-based hydrogen storage material. This method can produce a magnesium-based hydrogen storage material with a high hydrogen storage capacity.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogen storage materials, and in particular to a method for preparing a magnesium-based hydrogen storage material and the magnesium-based hydrogen storage material prepared thereby. Background Art

[0002] With the growing global demand for clean energy, hydrogen, as an efficient and clean energy carrier, has attracted considerable attention. Hydrogen storage technology is a key component of hydrogen energy utilization, and the development of hydrogen storage materials with high hydrogen storage capacity, excellent hydrogen absorption and desorption kinetics, and cyclic stability has become a current research hotspot. However, the storage capacity of hydrogen storage materials needs to be further improved. Summary of the Invention

[0003] In view of the above problems, the present invention provides a method for preparing a magnesium-based hydrogen storage material, which can effectively improve the hydrogen storage capacity of the hydrogen storage material.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] A method for preparing a magnesium-based hydrogen storage material comprises the following steps:

[0006] Hydroxyl groups were introduced onto the surface of TiO2 by a hydrothermal method to prepare TiO2 nanotubes, and aminopropylsiloxane was grafted onto the surface of TiO2 to prepare modified TiO2 nanotubes.

[0007] Reduced graphene oxide was introduced into modified TiO2 nanotubes to prepare graphene@TiO2 nanocomposite catalysts;

[0008] Graphene@TiO2 nanocomposite catalyst was introduced into nanomagnesium particles by ball milling to prepare magnesium-based hydrogen storage material.

[0009] Optionally, the preparation of TiO2 nanotubes includes: dispersing TiO2 powder in a sodium hydroxide aqueous solution, reacting at 120-180°C for 12-24 hours, and obtaining the TiO2 nanotubes after washing with water and centrifugation; the mass ratio of the TiO2 powder to the sodium hydroxide in the sodium hydroxide aqueous solution is 1:1-1:2, and the concentration of the sodium hydroxide aqueous solution is 0.5-2 mol / L.

[0010] Optionally, preparing the modified TiO2 nanotubes includes: dispersing the TiO2 nanotubes in an organic solvent, adding aminopropylsiloxane, and heating and refluxing at 80-120°C for 6-10 hours under inert gas protection to obtain modified TiO2 nanotubes.

[0011] Optionally, the organic solvent is toluene, the mass ratio of the TiO2 nanotubes to aminopropylsiloxane is 1:0.5-1:1; and the inert gas is nitrogen.

[0012] Optionally, preparing the graphene@TiO2 nanocomposite catalyst includes: reducing graphene oxide to reduced graphene oxide by a chemical reduction method, dispersing the reduced graphene oxide and the modified TiO2 nanotubes in ethanol at a mass ratio of 1:2-1:4, ultrasonically dispersing for 2-3 hours, and then evaporating the ethanol to obtain the graphene@TiO2 nanocomposite catalyst.

[0013] Optionally, in the chemical reduction method, sodium borohydride is used as a reducing agent, and the mass ratio of the graphene oxide to sodium borohydride is 1:0.3-1:0.6.

[0014] Optionally, the use of a ball milling method to introduce the graphene@TiO2 nanocomposite catalyst into the nanomagnesium particles includes: placing the nanomagnesium particles and the graphene@TiO2 nanocomposite catalyst in a mass ratio of 90:10-70:30 in a ball mill, adding stearic acid as a process control agent, and dry-milling at a speed of 300-500 rpm for 2-6 hours under argon protection; then transferring the dry-milled product to a ball mill containing cyclohexane solvent, and wet-milling at a speed of 300-500 rpm for 4-8 hours.

[0015] Optionally, in the dry ball milling step, the amount of stearic acid added is 3%-6% of the total mass of the nano-magnesium particles and the graphene@TiO2 nanocomposite catalyst; in the wet ball milling step, the amount of cyclohexane used is 5-10 mL of cyclohexane per gram of dry ball milling product; and the particle size of the nano-magnesium particles is 50-200 nm.

[0016] A magnesium-based hydrogen storage material is prepared by the preparation method.

[0017] Optionally, the magnesium-based hydrogen storage material has a hydrogen storage capacity of 6-6.8 wt % at 300-350° C. and 5 MPa hydrogen pressure, and after 10 cycles of hydrogen absorption and desorption, the hydrogen storage capacity decays by no more than 8%.

[0018] Beneficial effects

[0019] In the present invention, thanks to the high hydrogen storage capacity of the nanomagnesium particles themselves and the promoting effect of the graphene@TiO2 nanocomposite catalyst on the hydrogen absorption and desorption process, the overall hydrogen storage capacity of the material is significantly improved compared with the unmodified magnesium-based material, and can approach or even reach the theoretical hydrogen storage capacity.

[0020] Furthermore, the high conductivity of graphene accelerates electron transfer, and the catalytic activity of TiO2 nanotubes reduces the activation energy of hydrogen absorption and desorption. The synergistic effect of the two significantly reduces the hydrogen absorption and desorption temperature of magnesium-based hydrogen storage materials, greatly improves the hydrogen absorption and desorption rate, and can still maintain good performance stability after multiple cycles. DETAILED DESCRIPTION

[0021] One embodiment of the present invention provides a method for preparing a magnesium-based hydrogen storage material, comprising the following steps: introducing hydroxyl groups onto the surface of TiO2 using a hydrothermal method to prepare TiO2 nanotubes, and grafting aminopropylsiloxane onto the TiO2 surface to prepare modified TiO2 nanotubes. Reduced graphene oxide is introduced into the modified TiO2 nanotubes to prepare a graphene@TiO2 nanocomposite catalyst; and the graphene@TiO2 nanocomposite catalyst is introduced into nanomagnesium particles using a ball milling method to prepare the magnesium-based hydrogen storage material.

[0022] In the preparation method of this embodiment, thanks to the high hydrogen storage capacity of the nanomagnesium particles themselves and the promotion of the hydrogen absorption and desorption process by the graphene@TiO2 nanocomposite catalyst, the overall hydrogen storage capacity of the material is significantly improved compared to the unmodified magnesium-based material, and can approach or even reach the theoretical hydrogen storage capacity.

[0023] Furthermore, the high conductivity of graphene accelerates electron transfer, and the catalytic activity of TiO2 nanotubes reduces the activation energy of hydrogen absorption and desorption. The synergistic effect of the two significantly reduces the hydrogen absorption and desorption temperature of magnesium-based hydrogen storage materials, greatly improves the hydrogen absorption and desorption rate, and can still maintain good performance stability after multiple cycles.

[0024] Specifically, the modified TiO2 nanotubes prepared by the present invention through a unique hydrothermal method combined with grafting modification have abundant surface hydroxyl groups to increase active sites, and the compatibility with other materials is improved by aminopropylsiloxane grafting, providing a good foundation for subsequent composites.

[0025] The design of the graphene@TiO2 nanocomposite catalyst integrates the advantages of graphene's high conductivity and large specific surface area with the catalytic activity of TiO2 nanotubes. The synergistic effect of the two greatly improves the catalytic efficiency, effectively reduces the activation energy of hydrogen absorption and desorption of magnesium-based hydrogen storage materials, and accelerates the hydrogen absorption and desorption process.

[0026] A ball milling process combining dry and wet methods is adopted. The materials are first mixed and crushed by dry ball milling, and then the catalyst and magnesium particles are further evenly dispersed by wet ball milling under the protection of cyclohexane. This ensures the uniformity of the microstructure of the composite material and gives full play to the advantages of each component. In this way, a magnesium-based hydrogen storage material with high hydrogen storage capacity, excellent hydrogen absorption and desorption performance and stable circulation is prepared, laying a solid foundation for the practical application of magnesium-based hydrogen storage materials and promoting the development of hydrogen energy storage technology.

[0027] Alternatively, the preparation of TiO2 nanotubes includes dispersing TiO2 powder in a sodium hydroxide solution, reacting at 120-180°C for 12-24 hours, and then washing and centrifuging to obtain the TiO2 nanotubes. The mass ratio of TiO2 powder to sodium hydroxide in the sodium hydroxide solution is 1:1-1:2, and the concentration of the sodium hydroxide solution is 0.5-2 mol / L. The sodium hydroxide solution reacts with the TiO2 powder at a temperature of 120-180°C, which facilitates the reconstruction of the TiO2 lattice and the formation of the nanotube structure. The higher temperature provides sufficient energy to cause atomic migration and rearrangement on the surface of the TiO2 particles, resulting in the formation of the nanotube morphology. This nanotube structure has a large specific surface area, providing more active sites for subsequent surface modification and hydrogen storage reactions. Post-reaction washing and centrifugation effectively remove unreacted sodium hydroxide, reaction byproducts, and possible impurities. Water washing dissolves and removes water-soluble impurities, while centrifugation precipitates the TiO2 nanotubes, separating them from impurities in the supernatant. This yields high-purity TiO2 nanotubes, laying the foundation for subsequent modification and the preparation of high-performance magnesium-based hydrogen storage materials. High-purity TiO2 nanotubes can better function in hydrogen storage materials, avoiding the adverse effects of impurities on hydrogen storage performance.

[0028] Optionally, preparing the modified TiO2 nanotubes includes: dispersing the TiO2 nanotubes in an organic solvent, adding aminopropylsiloxane, and heating and refluxing at 80-120°C for 6-10 hours under inert gas protection to obtain the modified TiO2 nanotubes.

[0029] Aminopropyl siloxane contains siloxane and amino groups. The siloxane groups can undergo a condensation reaction with the hydroxyl groups on the surface of TiO2 nanotubes, thereby grafting the aminopropyl siloxane onto the surface of the TiO2 nanotubes. This surface modification can change the surface properties of the TiO2 nanotubes, giving them active groups such as amino groups, which provide active sites for subsequent bonding with other substances.

[0030] After modification, amino groups and other groups on the surface of TiO2 nanotubes can increase their dispersibility in organic solvents. These groups interact with organic solvent molecules, reducing agglomeration between TiO2 nanotubes and enabling more uniform dispersion in the solution. This facilitates subsequent mixing with substances like reduced graphene oxide, thereby improving the performance of the graphene@TiO2 nanocomposite catalyst. Conducting the reaction under inert gas protection prevents oxidation of substances in the system.

[0031] Under heating and reflux conditions at 80-120°C, the reaction proceeds fully, allowing aminopropylsiloxane to be grafted onto the TiO2 nanotube surface, forming a stable chemical bond. This chemical bond enhances the structural stability of the TiO2 nanotube surface, preventing structural changes or shedding during subsequent preparation and in magnesium-based hydrogen storage materials, thereby ensuring the stability of the entire material system and the reliability of its performance.

[0032] Furthermore, amino groups and other groups on the surface of the modified TiO2 nanotubes can interact with other materials (such as reduced graphene oxide and magnesium nanoparticles), improving their compatibility. For example, amino groups can form hydrogen bonds or other weak interactions with certain functional groups on the graphene surface, enabling better bonding between the graphene and the TiO2 nanotubes, forming a uniform nanocomposite structure. When composited with magnesium nanoparticles, the modified TiO2 nanotubes also achieve better contact and bonding with the magnesium particle surface, improving the overall performance of magnesium-based hydrogen storage materials.

[0033] Optionally, the organic solvent is toluene, the mass ratio of TiO2 nanotubes to aminopropylsiloxane is 1:0.5-1:1; and the inert gas is nitrogen.

[0034] Alternatively, preparing a graphene@TiO2 nanocomposite catalyst includes: reducing graphene oxide to reduced graphene oxide by chemical reduction, dispersing the reduced graphene oxide and modified TiO2 nanotubes in ethanol at a mass ratio of 1:2-1:4, ultrasonically dispersing for 2-3 hours, and then evaporating the ethanol to obtain the graphene@TiO2 nanocomposite catalyst. The reduced graphene oxide and modified TiO2 nanotubes are dispersed in ethanol at a certain mass ratio and ultrasonically dispersed. Ultrasonic dispersion can utilize the energy of ultrasonic waves to effectively break up the agglomerates of the reduced graphene oxide and modified TiO2 nanotubes, causing them to be uniformly dispersed in the ethanol solution. This helps to increase the contact area between the two materials, provides good conditions for subsequent interaction between the two, and is conducive to forming a uniform nanocomposite structure.

[0035] Optionally, in the chemical reduction method, sodium borohydride is used as a reducing agent, and the mass ratio of graphene oxide to sodium borohydride is 1:0.3-1:0.6.

[0036] Optionally, the graphene@TiO2 nanocomposite catalyst is introduced into the nanomagnesium particles by ball milling, comprising: placing the nanomagnesium particles and the graphene@TiO2 nanocomposite catalyst in a mass ratio of 90:10-70:30 in a ball mill, adding stearic acid as a process control agent, and dry-milling at a speed of 300-500 rpm for 2-6 hours under argon protection; then transferring the dry-milled product to a ball mill containing cyclohexane solvent, and wet-milling at a speed of 300-500 rpm for 4-8 hours.

[0037] Adding stearic acid as a process control agent can regulate friction and particle agglomeration during ball milling. Stearic acid molecules adsorb onto the particle surfaces, reducing their surface energy and reducing particle agglomeration, making the ball milling process more uniform and stable. Furthermore, stearic acid can protect the magnesium nanoparticles and graphene@TiO2 nanocomposite catalyst to a certain extent, preventing them from oxidation or other damage during ball milling.

[0038] Dry ball milling under argon protection can prevent the nano-magnesium particles and graphene@TiO2 nanocomposite catalyst from reacting with oxygen and moisture in the air during the ball milling process and being oxidized or deteriorated. As an inert gas, argon can provide a stable oxygen-free environment, ensuring the chemical stability of the materials during the ball milling process, which is conducive to obtaining magnesium-based hydrogen storage materials with stable performance. The dry ball milling product is transferred to a ball mill containing cyclohexane solvent for wet ball milling. The cyclohexane solvent can act as a lubricant and disperser, further improving the dispersion and uniformity of the particles. At the same time, wet ball milling can continue to refine and surface modify the particles at a lower energy input, making the bond between the nano-magnesium particles and the graphene@TiO2 nanocomposite catalyst closer, further optimizing the structure and performance of the composite material.

[0039] Optionally, in the dry ball milling step, the amount of stearic acid added is 3%-6% of the total mass of the nano-magnesium particles and the graphene@TiO2 nanocomposite catalyst; in the wet ball milling step, the amount of cyclohexane used is 5-10 mL of cyclohexane per gram of dry ball milling product; and the particle size of the nano-magnesium particles is 50-200 nm.

[0040] Another embodiment of the present invention provides a magnesium-based hydrogen storage material prepared by the above preparation method.

[0041] In one embodiment, the hydrogen storage capacity of the magnesium-based hydrogen storage material reaches 6-6.8 wt % at 300-350° C. and 5 MPa hydrogen pressure. After 10 cycles of hydrogen absorption and desorption, the hydrogen storage capacity decays by no more than 8%.

[0042] Example 1

[0043] In this embodiment, the preparation method of the magnesium-based hydrogen storage material is:

[0044] S01: Weigh 5g of TiO2 powder and disperse it in 100mL of 1.5mol / L sodium hydroxide solution. Transfer the mixture to an autoclave and react at 150°C for 18 hours. After the reaction, wash the mixture with deionized water and centrifuge it five times until the pH of the supernatant reaches neutral, yielding hydroxylated TiO2 nanotubes.

[0045] S02: Disperse 3 g of the hydroxylated TiO2 nanotubes in 50 mL of toluene, add 2 g of aminopropylsiloxane, and heat under reflux at 100°C for 8 hours under nitrogen. After the reaction, cool to room temperature, centrifuge, and wash three times with toluene and ethanol, respectively, before drying to obtain the modified TiO2 nanotubes.

[0046] S03: Disperse 1g of graphene oxide in 100mL of deionized water. After ultrasonic dispersion for 1 hour, slowly add 0.5g of sodium borohydride and continue ultrasonication for 2 hours to carry out the reduction reaction. After the reaction is complete, wash with a large amount of deionized water to remove residual reducing agent, obtaining reduced graphene oxide.

[0047] S04: 0.5 g of reduced graphene oxide and 2 g of modified TiO2 nanotubes were dispersed in 30 mL of ethanol, ultrasonically dispersed for 2 h, and then heated and stirred to evaporate the ethanol to obtain a graphene@TiO2 nanocomposite catalyst.

[0048] S05: Place 8g of nanomagnesium particles and 2g of graphene@TiO2 nanocomposite catalyst in a ball mill, add 0.5g of stearic acid, and dry-mill at 400 rpm under argon for 4 hours. Transfer the dry-milled product to a ball mill containing 60mL of cyclohexane and continue wet-milling at 400 rpm for 6 hours to obtain a magnesium-based hydrogen storage material.

[0049] Example 2

[0050] In this embodiment, the preparation method of the magnesium-based hydrogen storage material is:

[0051] S01: Weigh 5g of TiO2 powder and disperse it in 100mL of 1.5mol / L sodium hydroxide solution. Transfer the mixture to an autoclave and react at 150°C for 18 hours. After the reaction, wash the mixture with deionized water and centrifuge it five times until the pH of the supernatant reaches neutral, yielding hydroxylated TiO2 nanotubes.

[0052] S02: Disperse 3 g of the hydroxylated TiO2 nanotubes in 50 mL of toluene, add 2 g of aminopropylsiloxane, and heat under reflux at 100°C for 8 hours under nitrogen. After the reaction, cool to room temperature, centrifuge, and wash three times with toluene and ethanol, respectively, before drying to obtain the modified TiO2 nanotubes.

[0053] S03: Disperse 1g of graphene oxide in 100mL of deionized water. After ultrasonic dispersion for 1 hour, slowly add 0.5g of sodium borohydride and continue ultrasonication for 2 hours to carry out the reduction reaction. After the reaction is complete, wash with a large amount of deionized water to remove residual reducing agent, obtaining reduced graphene oxide.

[0054] S04: 0.5 g of reduced graphene oxide and 2 g of modified TiO2 nanotubes were dispersed in 30 mL of ethanol, ultrasonically dispersed for 2 h, and then heated and stirred to evaporate the ethanol to obtain a graphene@TiO2 nanocomposite catalyst.

[0055] S05: 8 g of nano-magnesium particles and 2 g of graphene@TiO2 nanocomposite catalyst were placed in a ball mill, 0.5 g of stearic acid was added, and dry ball milling was performed at 400 rpm for 10 h under argon protection.

[0056] Comparative Example 1

[0057] In this comparative example, the preparation method of the magnesium-based hydrogen storage material is:

[0058] 10g of nanomagnesium particles were placed in a ball mill, 0.5g of stearic acid was added, and dry milling was performed at 400 rpm under argon protection for 4 hours. The dry milled product was transferred to a ball mill containing 60mL of cyclohexane and wet milled at 400 rpm for another 6 hours to obtain a magnesium-based hydrogen storage material.

[0059] Comparative Example 2

[0060] In this comparative example, the preparation method of the magnesium-based hydrogen storage material is:

[0061] S01: Weigh 5g of TiO2 powder and disperse it in 100mL of 1.5mol / L sodium hydroxide solution. Transfer the mixture to an autoclave and react at 150°C for 18 hours. After the reaction, wash the mixture with deionized water and centrifuge it five times until the pH of the supernatant reaches neutral, yielding hydroxylated TiO2 nanotubes.

[0062] S02: Disperse 3 g of the hydroxylated TiO2 nanotubes in 50 mL of toluene, add 2 g of aminopropylsiloxane, and heat under reflux at 100°C for 8 hours under nitrogen. After the reaction, cool to room temperature, centrifuge, and wash three times with toluene and ethanol, respectively, before drying to obtain the modified TiO2 nanotubes.

[0063] S03: Place 8g of nanomagnesium particles and 2g of modified TiO2 nanotubes in a ball mill, add 0.5g of stearic acid, and dry-mill at 400 rpm under argon for 4 hours. Transfer the dry-milled product to a ball mill containing 60mL of cyclohexane and continue wet-milling at 400 rpm for 6 hours to obtain a magnesium-based hydrogen storage material.

[0064] Test Case

[0065] (1) The magnesium-based hydrogen storage materials obtained in the examples and comparative examples were tested for their performance: a Sieverts gas adsorption instrument was used to measure their hydrogen storage capacity and the hydrogen storage capacity decay after 10 cycles of hydrogen absorption and desorption. Test conditions: 300°C, 5 MPa hydrogen pressure.

[0066] Test results: Comparative Example 1 had a hydrogen storage capacity of 3.5wt% with a 20% attenuation. Comparative Example 2 had a hydrogen storage capacity of 4.3wt% with a 15% attenuation. Example 1 had a hydrogen storage capacity of 6.2wt% (the theoretical hydrogen storage capacity of magnesium-based hydrogen storage materials is 7.6wt%) with a 5% attenuation. Example 2 had a hydrogen storage capacity of 5.8wt% with a 7% attenuation.

[0067] (2) The hydrogen absorption and desorption kinetics of the hydrogen storage materials in the examples and comparative examples were studied by thermogravimetric-differential thermal analysis (TG-DTA) combined with temperature-programmed desorption (TPD) technology. Compared with the pure magnesium hydrogen storage material in comparative example 1, the results are as follows: Compared with comparative example 1, the hydrogen absorption activation energy of Example 1 is reduced by 31 kJ / mol, and the hydrogen desorption temperature is reduced by 50°C. Compared with comparative example 1, the hydrogen absorption activation energy of Example 2 is reduced by 24 kJ / mol, and the hydrogen desorption temperature is reduced by 43°C. Compared with comparative example 1, the hydrogen absorption activation energy of Comparative Example 2 is reduced by 13 kJ / mol, and the hydrogen desorption temperature is reduced by 18°C.

[0068] The test results show that the preparation method of the present invention can obtain a magnesium-based hydrogen storage material with high hydrogen storage capacity and small hydrogen absorption and desorption cycle attenuation, and the hydrogen absorption activation energy and hydrogen desorption temperature of the obtained hydrogen storage material are effectively reduced.

[0069] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

[0070] For those skilled in the art, according to the concept of the present invention, there may be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for preparing a magnesium-based hydrogen storage material, characterized in that: The steps include: Hydroxyl groups were introduced onto the surface of TiO2 by a hydrothermal method to prepare TiO2 nanotubes, and aminopropylsiloxane was grafted onto the surface of TiO2 to prepare modified TiO2 nanotubes. Reduced graphene oxide was introduced into modified TiO2 nanotubes to prepare graphene@TiO2 nanocomposite catalysts; Graphene@TiO2 nanocomposite catalyst was introduced into nanomagnesium particles by ball milling to prepare magnesium-based hydrogen storage material.

2. The method for preparing a magnesium-based hydrogen storage material according to claim 1, wherein: The preparation of TiO2 nanotubes includes: dispersing TiO2 powder in a sodium hydroxide aqueous solution, reacting at 120-180°C for 12-24 hours, and obtaining the TiO2 nanotubes after washing with water and centrifugation; the mass ratio of the TiO2 powder to the sodium hydroxide in the sodium hydroxide aqueous solution is 1:1-1:2, and the concentration of the sodium hydroxide aqueous solution is 0.5-2 mol / L.

3. The method for preparing a magnesium-based hydrogen storage material according to claim 1, wherein: The preparation of modified TiO2 nanotubes includes: dispersing the TiO2 nanotubes in an organic solvent, adding aminopropylsiloxane, and heating and refluxing at 80-120°C for 6-10 hours under the protection of an inert gas to obtain the modified TiO2 nanotubes.

4. The method for preparing a magnesium-based hydrogen storage material according to claim 3, wherein: The organic solvent is toluene, the mass ratio of the TiO2 nanotubes to aminopropylsiloxane is 1:0.5-1:1; and the inert gas is nitrogen.

5. The method for preparing the magnesium-based hydrogen storage material according to claim 1, wherein: The preparation of the graphene@TiO2 nanocomposite catalyst includes: reducing graphene oxide to reduced graphene oxide by a chemical reduction method, dispersing the reduced graphene oxide and the modified TiO2 nanotubes in ethanol at a mass ratio of 1:2-1:4, ultrasonically dispersing for 2-3 hours, and then evaporating the ethanol to obtain the graphene@TiO2 nanocomposite catalyst.

6. The method for preparing the magnesium-based hydrogen storage material according to claim 5, wherein: In the chemical reduction method, sodium borohydride is used as a reducing agent, and the mass ratio of the graphene oxide to sodium borohydride is 1:0.3-1:0.

6.

7. The method for preparing a magnesium-based hydrogen storage material according to any one of claims 1 to 6, wherein: The method of introducing a graphene@TiO2 nanocomposite catalyst into nanomagnesium particles by a ball milling method includes: placing the nanomagnesium particles and the graphene@TiO2 nanocomposite catalyst in a mass ratio of 90:10-70:30 in a ball milling jar, adding stearic acid as a process control agent, and dry-milling the mixture at a speed of 300-500 rpm for 2-6 hours under argon protection; then transferring the dry-milled product to a ball milling jar containing a cyclohexane solvent and wet-milling the mixture at a speed of 300-500 rpm for 4-8 hours.

8. The method for preparing a magnesium-based hydrogen storage material according to claim 7, wherein: In the dry ball milling step, the amount of stearic acid added is 3%-6% of the total mass of the nano-magnesium particles and the graphene@TiO2 nanocomposite catalyst; in the wet ball milling step, the amount of cyclohexane used is 5-10 mL of cyclohexane per gram of dry ball milling product; and the particle size of the nano-magnesium particles is 50-200 nm.

9. A magnesium-based hydrogen storage material, characterized in that It is prepared by the preparation method according to any one of claims 1 to 8.

10. The magnesium-based hydrogen storage material according to claim 9, characterized in that The magnesium-based hydrogen storage material has a hydrogen storage capacity of 6-6.8 wt% at 300-350° C. and 5 MPa hydrogen pressure. After 10 cycles of hydrogen absorption and desorption, the hydrogen storage capacity decays by no more than 8%.