Vanadium oxide catalyst based on alkali metal enhancement for magnesium-based hydrogen storage material and preparation method

Abstract

The application relates to the hydrogen energy technology field and provides a vanadium oxide catalyzed magnesium-based hydrogen storage material based on alkali metal enhancement and a preparation method. 15 The material is prepared by high-energy ball milling and is composed of spherical MgH2 powder and lamellar XV6O 15 C powder, wherein X is one of alkali metals Li, Na and K. The material has a nanoscale composite structure and can significantly improve the hydrogen storage performance. The preparation method comprises the following steps: 1) preparing XV6O 15 C nano powder through acid etching, alkali metal modification and heat treatment; and 2) mixing the powder with MgH2 under a protective atmosphere and preparing a composite material by high-energy ball milling. The results show that the catalyst improves the hydrogen absorption and release rate of MgH2 and reduces the hydrogen storage temperature to 50 DEG C for hydrogen absorption and 200 DEG C to 225 DEG C for rapid hydrogen release. The application significantly optimizes the hydrogen storage kinetics and temperature performance, provides an effective strategy for the design and application of a new magnesium-based composite hydrogen storage material and is suitable for hydrogen energy industrial application.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen energy technology, specifically relating to an alkali metal-enhanced vanadium oxide catalytic magnesium-based hydrogen storage material and its preparation method. Background Technology

[0002] With the escalating global energy crisis and increasingly severe environmental problems, finding a new and clean energy source has become an urgent need in the global energy sector. Hydrogen, as a zero-carbon fuel, has a high energy density (142 MJ / kg⁻¹). - ¹) and its advantage of producing only water after combustion, hydrogen is considered an ideal alternative to traditional fossil fuels. Not only is hydrogen environmentally friendly and pollution-free, but it can also serve as a storage medium for renewable energy, especially when combined with unstable energy sources such as wind and tidal power to achieve more efficient energy conversion and storage. However, efficient and safe storage of hydrogen remains a major challenge for the industrialization of hydrogen energy.

[0003] Hydrogen storage technologies can be categorized into three main types: solid-state hydrogen storage, cryogenic liquid hydrogen storage, and high-pressure gaseous hydrogen storage. Among these, solid-state hydrogen storage technology has become one of the most promising technologies due to its high hydrogen storage density, good safety, and high recyclability. Currently, solid-state hydrogen storage materials mainly include physical adsorption materials, metal hydrides, and coordination hydrides. Magnesium-based hydrides (MgH2), as a solid-state hydrogen storage material with great potential, is considered one of the most promising hydrogen storage materials due to its high hydrogen storage density (theoretical value of 7.6 wt%) and abundant resource background. However, the slow kinetics and high dehydrogenation temperature of MgH2 in practical applications limit its widespread use. Therefore, improving the hydrogen adsorption and desorption kinetics of MgH2 and reducing its dehydrogenation temperature have become current research hotspots. Summary of the Invention

[0004] In view of this, in order to solve the problems of high hydrogen absorption and desorption temperature and slow kinetics of MgH2, this invention proposes a magnesium-based hydrogen storage material based on alkali metal-enhanced vanadium oxide catalyst and its preparation method.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A magnesium-based hydrogen storage material based on alkali metal-enhanced vanadium oxide catalyst, comprising spherical MgH2 powder and layered XV6O 15 @C powder was prepared by high-energy ball milling, wherein X is one of Li, Na, and K, and MgH2 is uniformly coated with XV6O. 15 @C, forming a nanoscale composite structure.

[0006] Furthermore, the particle size of the spherical MgH2 powder used is less than 50 μm; the lamellar XV6O used... 15@C powder consists of micron-sized flakes with diameters between 50 and 100 μm, each flake composed of numerous nanorods; spherical MgH2 powder and layered XV6O 15 The mass fraction ratio of C powder is 94:6, and the solid magnesium-based hydrogen storage material MgH2-XV6O is formed after ball milling. 15 The average particle size of @C is 100~500 nm, and the surface of each MgH2 particle is coated with XV6O. 15 @C. The nanostructure of the raw material particles facilitates good mixing and coating during ball milling, promoting improved material performance.

[0007] A method for preparing a magnesium-based hydrogen storage material based on alkali metal-enhanced vanadium oxide catalyst, as described above, includes the following steps: (1) Synthesis of XV6O with lamellar structure 15 @C nanomaterial powder; (2) XV6O 15 @C powder and MgH2 powder were mixed and ball-milled to obtain solid magnesium-based hydrogen storage material MgH2-XV6O 15 @C.

[0008] Furthermore, in step (1) XV6O 15 The synthesis method of @C powder includes the following steps: V2C MXene was prepared by etching V2AlC MAX with a mixed acid of HCl and HF: 30 ml of HF and 20 ml of HCl were added sequentially to a polytetrafluoroethylene liner to prepare the mixed acid; 2 g of V2AlC MAX was slowly added to the acid mixture under ice bath conditions, and the mixture was stirred at 55 °C for 2 days; after etching, the mixture was centrifuged at 6000 rpm for 5 min; the precipitate was washed with water and centrifuged at 12000 rpm for 5 min three times until the pH reached (6~7) to obtain a black precipitate; To obtain few-layer V2C MXene, 25 ml of 5% TBAOH solution was added to the black precipitate, and the mixture was stirred at room temperature for 24 h. Then, it was centrifuged at 10,000 rpm for 5 min. The precipitate was washed twice with ethanol until the pH was neutral. Subsequently, 150 ml of deionized water was added to the precipitate, and the mixture was shaken to obtain a black mixture. The black mixture was sonicated for 1 h under argon protection and an ice bath. Then, the liquid was centrifuged at 3500 rpm for 30 min, and the supernatant was freeze-dried for 48 h to obtain few-layer V2C MXene. 90 mg of V2C MXene was added to 38 ml of deionized water and sonicated for 20 min under ice bath conditions to uniformly disperse V2C MXene in the deionized water. 5 ml of hydrazine hydrate and 5 ml of 2.5 M XOH solution were added sequentially to the dispersion. The mixture was then stirred in a water bath at 80 °C for 6 h at 500 rpm. The resulting solution was then centrifuged at 5000 rpm for 5 min, and the precipitate was washed three times with deionized water at 5000 rpm for 5 min each time until the black powder was neutral. The precipitate was then freeze-dried for 48 h to obtain X-ion modified V2C MXene. The X-ion modified V2C MXene was transferred to a tube furnace and in a CO2 atmosphere at 5 °C·min. -1 The temperature was increased to 400℃ at a heating rate and held for 15 h, with a gas flow rate of 250 sccm. The final powder obtained was XV6O. 15 Micrometer sheets composed of C nanorods.

[0009] Furthermore, in step (2), XV6O 15 The ball milling method for C powder and MgH2 powder is as follows: Under a protective atmosphere, stainless steel balls are used for milling. MgH2 and XV6O... 15 The mass fraction ratio of @C is 94:6, the ball-to-material ratio is 40:1, the ball mill speed is 400 rpm, and the effective ball milling time is 12 h.

[0010] Furthermore, during the ball milling process, a method of running for 10 minutes and then stopping for 10 minutes is adopted to avoid overheating during the ball milling process.

[0011] The beneficial effects of this invention are as follows: 1. This invention proposes a magnesium-based hydrogen storage material based on vanadium oxide catalysis enhanced by alkali metals. The catalytic performance of vanadium oxide is not only related to the oxidation state of vanadium but also influenced by its crystal structure and surface active sites. In this process, the incorporation of alkali metals can effectively regulate the oxidation state of vanadium and its catalytic performance. Alkali metal ions (Li...) + Na + K + It possesses a strong electron donation capability, which can effectively alter the electron density of vanadium oxides, enabling them to exert a more significant catalytic effect in hydrogenation / dehydrogenation reactions. By regulating the oxidation state and catalytic properties of vanadium, the hydrogen storage performance of MgH2 can be significantly improved.

[0012] 2. High-energy ball milling involves mixing powders of different materials and grinding them for an extended period to form nanoscale particles. This enhances the surface activity of the materials, shortens the diffusion path of hydrogen atoms, and thus improves hydrogen storage performance. Simultaneously, high-energy ball milling can also stimulate chemical reactions and utilize mechanical energy to induce structural transformations in the raw materials, generating composites with new activities, thereby further improving their hydrogen storage performance. This invention utilizes high-energy ball milling to incorporate a single-crystal alkali metal-reinforced vanadium oxide catalyst into MgH2, and to... 2+ / V 3+ The introduction of alkali metal ions into the interface excites V 2+ / V 3+ Catalytic activity at the interface. Studies have found that XV6O 15 @C nanorods were in-situ reduced to generate XVO2, VO, V2O3, and C, significantly improving the hydrogen absorption and desorption rates of MgH2. This resulted in a composite hydrogen storage material with excellent low-temperature hydrogen storage performance, achieving hydrogen absorption at low temperatures (50°C) and rapid hydrogen desorption kinetics at lower desorption temperatures (e.g., 200, 225°C). Simultaneously, both hydrogen absorption kinetics and total hydrogen absorption and desorption were optimized and improved. This provides an effective strategy for the design of novel magnesium-based composite hydrogen storage materials.

[0013] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0014] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein: Figure 1 To prepare NaV6O 15 X-ray diffraction (XRD) pattern and XPS spectrum of the @C catalyst.

[0015] Figure 2 NaV6O 15 SEM, TEM, HRTEM, SAED and EDS images of @C nanorods.

[0016] Figure 3 MgH2-V2O5@C and MgH2-NaV6O 15 Isothermal dehydrogenation / hydrogen absorption kinetics curves for @C.

[0017] Figure 4 It is MgH2-NaV6O 15 Isothermal dehydrogenation / hydrogen absorption kinetics curves for @C.

[0018] Figure 5 At 300 °C, MgH2-NaV6O 15 @C's cyclic dynamics curve.

[0019] Figure 6 It is MgH2-NaV6O 15 XRD patterns and XPS spectra of the @C composite hydrogen storage material in the ball-milled, dehydrogenated, and hydrogen-absorbed states.

[0020] Figure 7 MgH2-V2O5@C and MgH2-NaV6O 15 The graph shows the change in the cyclic hydrogen storage capacity of @C. Detailed Implementation

[0021] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0022] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0023] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0024] A magnesium-based hydrogen storage material based on alkali metal-enhanced vanadium oxide catalyst, comprising spherical MgH2 powder and layered XV6O 15@C powder is prepared by high-energy ball milling, wherein X can be one of Li, Na, and K, and MgH2 is uniformly coated with XV6O. 15 @C, forming a nanoscale composite structure.

[0025] In this embodiment, Na is used as an example. The particle size of the spherical MgH2 powder used is less than 50 μm; the lamellar NaV6O used... 15 @C powder consists of micron-sized flakes with diameters between 50 and 100 μm, each flake composed of numerous nanorods; spherical MgH2 powder and layered NaV6O 15 The mass fraction ratio of C powder is 94:6, and the solid magnesium-based hydrogen storage material MgH2-NaV6O is formed after ball milling. 15 The average particle size of @C is 100~500 nm, and the surface of each MgH2 particle is coated with NaV6O. 15 @C. The specific preparation method of this material is as follows: (1) Preparation of NaV6O 15 @C powder V2C MXene was prepared by etching V2AlC MAX with a mixed acid of HCl and HF: 30 ml of HF and 20 ml of HCl were sequentially added to a polytetrafluoroethylene liner to prepare the mixed acid. Then, 2 g of V2AlC MAX was slowly added to the acid mixture under ice bath conditions, and the mixture was stirred at 55 °C for 2 days. After etching, the mixture was centrifuged at 6000 rpm for 5 min. Subsequently, the precipitate was washed with water and centrifuged three times at 12000 rpm for 5 min until the pH reached (6-7), yielding a black precipitate. To obtain a few-layer V2C MXene, 25 ml of 5% TBAOH solution was added to the precipitate, and the mixture was stirred at room temperature for 24 h. Then, it was centrifuged at 10000 rpm for 5 min, and the resulting precipitate was washed twice with ethanol until the pH was neutral. Subsequently, 150 ml of deionized water was added to the precipitate, and the mixture was shaken to obtain a black mixture. The mixture was sonicated for 1 h under argon protection and an ice bath. The liquid was then centrifuged at 3500 rpm for 30 min. The supernatant was freeze-dried for 48 h to obtain a few-layer V2C MXene.

[0026] NaV6O 15Preparation of @C nanorods: 90 mg of V2C MXene was added to 38 ml of deionized water and sonicated for 20 min under ice bath conditions to uniformly disperse V2C MXene in the deionized water. 5 ml of hydrazine hydrate and 5 ml of 2.5 M NaOH solution were added sequentially to the dispersion. The mixture was then stirred in a water bath at 80 °C for 6 h at 500 rpm. The resulting solution was then centrifuged at 5000 rpm for 5 min. The precipitate was washed three times with deionized water at 5000 rpm for 5 min each time until the black powder was neutral. The precipitate was then freeze-dried for 48 h to obtain Na-modified V2C MXene. The Na-modified V2C was transferred to a tube furnace and in a CO2 atmosphere at 5 °C·min. -1 The temperature was increased to 400 °C and held for 15 h at a heating rate of 250 sccm. The final powder obtained was NaV6O. 15 Micrometer sheets composed of C nanorods.

[0027] (2) Preparation of doped NaV6O 15 @C MgH2 hydrogen storage material In a glove box filled with argon gas, a certain mass fraction of NaV6O was weighed out. 15 @C powder, and mixed with MgH2, wherein MgH2 and NaV6O 15 The mass fraction ratio of @C was 94:6. The powder was then placed in a 250 ml stainless steel ball mill jar with a ball-to-powder ratio of 40:1. It was ball-milled for 12 hours at 400 rpm in a high-energy ball mill, with a 10-minute interval between milling cycles. This yielded the composite hydrogen storage material. After milling, the stainless steel ball mill jar was placed in a glove box, and the milled powder was removed for relevant tests.

[0028] The prepared solid magnesium-based hydrogen storage material MgH2-NaV6O 15 The test was performed using @C, and the results are as follows: Figure 1 To prepare NaV6O 15 X-ray diffraction (XRD) pattern and XPS spectrum of the @C catalyst. The XRD pattern shows that the product reacts with NaV6O 15 The results were in good agreement (PDF#77-0146), with all diffraction peaks matching the PDF standard card well, and no characteristic peaks of impurities were observed, indicating that the prepared product had high purity.

[0029] Figure 2 NaV6O 15SEM, TEM, HRTEM, SAED, and EDS images of @C nanorods. The SEM images show the calcined NaV6O... 15 The @C sample exhibits a sheet-like structure similar to V2C MXene, with sheet diameters ranging from 50 to 100 μm. Magnified SEM images reveal that the micron-sized sheets are composed of numerous nanorods. TEM measurements show that the nanorods have a diameter of 100 nm and a length of 1.5 μm. HRTEM images show lattice fringes distributed along the nanorod growth direction, with an interplanar spacing of 0.950 nm, corresponding to NaV6O. 15 (100) face. NaV6O 15 The SAED diffraction pattern of @C exhibits typical single-crystal characteristics. The EDS spectrum indicates that NaV6O 15 @C shows that Na, V, and O are uniformly distributed in the sample. These results demonstrate that high-purity single-crystal NaV6O was successfully prepared by calcining Na-ion-modified V2C MXene in a CO2 atmosphere. 15 @C nanorod catalyst.

[0030] Figure 3 MgH2-V2O5@C and MgH2-NaV6O 15 Isothermal dehydrogenation / hydrogen absorption kinetics curves of @C. Experimental results show that NaV6O 15 @C exhibits superior catalytic efficiency for the hydrogen absorption / desorption process of Mg / MgH2 compared to V2O5@C. At 200 °C, MgH2-NaV6O 15 @C can release 5.0 wt.% H2 within 72 min; in the same time, MgH2-V2O5@C can only release 2.98 wt.% H2 at 200 ℃, and its hydrogen release is only a fraction of that of MgH2-NaV6O. 15 @C 60%. Meanwhile, at a lower temperature of 175 ℃, MgH2-NaV6O 15 @C can release 1.80 wt.% H2 within 170 min; in contrast, MgH2-V2O5@C can only release 0.90 wt.% H2 in the same time at 180 °C. The incorporation of Na nearly doubles the hydrogen dehydrogenation rate of the material under mesophilic conditions. Simultaneously, Na enhances the catalytic efficiency of vanadium oxide catalysts for Mg hydrogen absorption. These results indicate that Na incorporation activates the catalytic performance of vanadium oxides, especially for MgH2 dehydrogenation under mesophilic conditions (i.e., 150-200 °C), where MgH2-NaV6O5@C... 15 @C exhibits the most significant advantages. The lower the temperature, the more pronounced the improvement of hydrogen desorption kinetics by Na on the material. Simultaneously, the incorporation of Na further enhances the hydrogen absorption performance of Mg at low temperatures.

[0031] Figure 4 It is MgH2-NaV6O 15 The isothermal dehydrogenation / hydrogen absorption kinetics curves of MgH2-NaV6O at @C show that... 15 Both @C can achieve rapid hydrogen release. For example, at 325 °C, MgH2-NaV6O 15 @C can achieve a hydrogen release of 6.20 wt.% within 1.5 min. At 300 °C, MgH2-NaV6O 15 @C can release 6.00 wt.% H2 within 3.5 min. At even lower temperatures, MgH2-NaV6O 15 @C also exhibits good hydrogen desorption kinetics. At 275 ℃, 250 ℃, 225 ℃, 200 ℃ and 175 ℃, MgH2-NaV6O 15 @C released 5.79 wt.%, 5.43 wt.%, 5.17 wt.%, 5.00 wt.%, and 1.80 wt.% H2 at 8.5 min, 19 min, 20 min, 70 min, and 170 min, respectively. The completely dehydrogenated MgH2-NaV6O 15 @C achieves high hydrogen storage capacity and absorption rate at 125 °C, absorbing 5.76 wt.% and 5.90 wt.% H2 within 3 min and 6 min, respectively. At temperatures of 100 °C, 75 °C, 50 °C, and 25 °C, the dehydrogenated MgH2-NaV6O... 15 @C absorbed 4.85 wt.%, 4.76 wt.%, 4.10 wt.%, and 3.05 wt.% H2 within 8.5 min, 24 min, 31.5 min, and 55.4 min, respectively.

[0032] Figure 5 At 300 °C, MgH2-NaV6O 15 The cycling kinetics curve of @C is shown. In the first cycle, the fully dehydrogenated sample absorbed 5.93 wt.% H2. During the cycling process, the aggregation and poisoning effects of Mg / MgH2 caused the hydrogen storage capacity of the material to decrease rapidly in the first seven cycles. After seven cycles, MgH2-NaV6O 15 The hydrogen storage capacity of @C decreased from 5.93 wt.% to 5.49 wt.%, accounting for 92.6% of the maximum hydrogen storage capacity. After the 7th cycle, the hydrogen storage capacity of Mg was activated, and its hydrogen storage capacity was positively correlated with the number of cycles. The hydrogen storage capacity began to stabilize after the 51st hydrogen adsorption / desorption cycle. After 100 hydrogen adsorption / desorption cycles, MgH2-NaV6O... 15@C has a hydrogen storage capacity of 6.04 wt.%, with a hydrogen storage capacity retention rate of 101.9%. Test results show that NaV6O 15 @C catalysts exhibit high catalytic activity and stability.

[0033] Figure 6 It is MgH2-NaV6O 15 XRD and XPS spectra of the ball-milled, dehydrogenated, and hydrogen-absorbed NaV6O composite hydrogen storage material. 15 Following the incorporation of carbon (@C) into MgH2, in-situ reduction occurred, generating NaVO2, VO, V2O3, and C. C, acting as a grinding aid, contributes to the uniform distribution of the catalytic phase within the Mg / MgH2. The catalytic interface composed of NaVO2, VO, and V2O3 significantly improves the hydrogen storage kinetics of Mg / MgH2. Compared to the VO / V2O3 interface, the incorporation of Na ions increases the conductivity at the interface and provides a large number of free electrons, effectively promoting electron transfer during the dehydrogenation process of MgH2. Simultaneously, the presence of the catalytic interface provides numerous sites for Mg nucleation and growth, lowering the reaction energy barrier for the Mg / MgH2 absorption / dehydrogenation process.

[0034] Figure 7 MgH2-V2O5@C and MgH2-NaV6O 15 The graph shows the cycling hydrogen storage capacity variation of @C. The results indicate that Na incorporation significantly improves the cycling stability of the material. Compared to MgH2-V2O5@C, MgH2-NaV6O 15 @C exhibits significant advantages in cyclic hydrogen storage performance. It can be seen that the cyclic capacity changes in both systems show a trend of first decreasing and then increasing; the incorporation of Na effectively shortens the hydrogen storage capacity decay and activation cycle of the material. For example, the cycle period for hydrogen storage capacity decay is reduced from 46 cycles to 7 cycles; MgH2-NaV6O 15 After experiencing capacity decay, MgH2-V2O5@C rapidly stabilizes after the 51st cycle. However, after 100 cycles, the hydrogen storage capacity of MgH2-V2O5@C continues to increase. Simultaneously, the presence of Na significantly enhances the hydrogen storage capacity of the material. After 100 cycles, the hydrogen storage capacity of MgH2-V2O5@C and MgH2-NaV6O... 15 The hydrogen storage capacities of @C are 4.71 wt.% and 6.03 wt.%, respectively; during cycling, the minimum hydrogen storage capacities of the materials are 4.27 wt.% and 5.49 wt.%, respectively.

[0035] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A magnesium-based hydrogen storage material based on alkali metal-reinforced vanadium oxide catalyst, characterized in that: The material consists of spherical MgH2 powder and layered XV6O. 15 @C powder was prepared by high-energy ball milling, wherein X is one of Li, Na, and K, and MgH2 is uniformly coated with XV6O. 15 @C, forming a nanoscale composite structure; The spherical MgH2 powder used has a particle size of less than 50 μm; the lamellar XV6O used 15 @C powder consists of micron-sized flakes with diameters between 50 and 100 μm, each flake composed of numerous nanorods; spherical MgH2 powder and layered XV6O 15 The mass fraction ratio of C powder is 94:6, and the solid magnesium-based hydrogen storage material MgH2-XV6O is formed after ball milling. 15 The average particle size of @C is 100~500 nm, and the surface of each MgH2 particle is coated with XV6O. 15 @C; Among them, XV6O 15 The synthesis method of @C powder includes the following steps: V2C MXene was prepared by etching V2AlC MAX with a mixed acid of HCl and HF: 30 ml of HF and 20 ml of HCl were added sequentially to a polytetrafluoroethylene liner to prepare the mixed acid; 2 g of V2AlC MAX was slowly added to the acid mixture under ice bath conditions, and the mixture was stirred at 55 °C for 2 days; after etching, the mixture was centrifuged at 6000 rpm for 5 min; the precipitate was washed with water and centrifuged at 12000 rpm for 5 min three times until the pH reached 6-7 to obtain a black precipitate; To obtain few-layer V2C MXene, 25 ml of 5% TBAOH solution was added to the black precipitate, and the mixture was stirred at room temperature for 24 h. Then, it was centrifuged at 10,000 rpm for 5 min. The precipitate was washed twice with ethanol until the pH was neutral. Subsequently, 150 ml of deionized water was added to the precipitate, and the mixture was shaken to obtain a black mixture. The black mixture was sonicated for 1 h under argon protection and an ice bath. Then, the liquid was centrifuged at 3500 rpm for 30 min, and the supernatant was freeze-dried for 48 h to obtain few-layer V2C MXene. 90 mg of V2C MXene was added to 38 ml of deionized water and sonicated in an ice bath for 20 min to uniformly disperse V2C MXene in the deionized water. 5 ml of hydrazine hydrate and 5 ml of 2.5 M XOH solution were added sequentially to the dispersion. The mixture was then stirred in a water bath at 80 °C for 6 h at 500 rpm. The resulting solution was then centrifuged at 5000 rpm for 5 min. The precipitate was washed three times with deionized water at 5000 rpm for 5 min each time until the black powder was neutral. The precipitate was then freeze-dried for 48 h to obtain X-ion modified V2C MXene. The X-ion modified V2C MXene was transferred to a tube furnace and in a CO2 atmosphere at 5 °C·min. -1 The temperature was increased to 400 °C and held for 15 h at a heating rate of 250 sccm. The final powder obtained was XV6O. 15 Micrometer sheets composed of C nanorods.

2. A method for preparing a magnesium-based hydrogen storage material based on alkali metal-reinforced vanadium oxide catalyst as described in claim 1, characterized in that, Includes the following steps: (1) Synthesis of XV6O with lamellar structure 15 @C nanomaterial powder; (2) XV6O 15 @C powder and MgH2 powder were mixed and ball-milled to obtain solid magnesium-based hydrogen storage material MgH2-XV6O 15 @C.

3. The method for preparing magnesium-based hydrogen storage materials based on alkali metal-reinforced vanadium oxide catalysts according to claim 2, characterized in that, In step (2), XV6O 15 The ball milling method for C powder and MgH2 powder is as follows: Under a protective atmosphere, stainless steel balls are used for milling. MgH2 and XV6O... 15 The mass fraction ratio of @C is 94:6, the ball-to-material ratio is 40:1, the ball mill speed is 400 rpm, and the effective ball milling time is 12 h.

4. The method for preparing magnesium-based hydrogen storage materials based on alkali metal-reinforced vanadium oxide catalysts according to claim 3, characterized in that: During the ball milling process, a method of running for 10 minutes and then stopping for 10 minutes is adopted to avoid overheating during the ball milling process.

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