A nano-solid hydrogen storage material and its preparation method

Abstract

This invention discloses a nano-solid-state hydrogen storage material and its preparation method, belonging to the field of new energy materials technology. The nano-solid-state hydrogen storage material has a core-shell structure, comprising a nano-magnesium-based active phase core and a functionalized porous carbon material outer shell; the core contains in-situ grown multi-metal nanocatalyst particles; the outer shell is doped with non-metallic elements and loaded with metal-organic framework derivative nanoparticles; the core-shell structure is dispersed in a three-dimensional interconnected carbon-based network framework. The preparation method includes: preparing a multi-metal-organic framework precursor solution; synthesizing multi-metal-organic framework nanoparticles using a solvothermal method; chemically combining with a magnesium source and a nickel source to obtain a precursor composite; carbonization treatment to obtain a porous carbon-coated multi-metal nanocatalyst@magnesium-based composite material; constructing a three-dimensional network framework by combining with a functionalized carbon source and metal-organic framework derivatives; and high-pressure hydrogenation treatment. The material of this invention exhibits a low hydrogen desorption temperature, rapid hydrogen absorption and desorption kinetics, and excellent cycle stability.

Description

Technical Field

[0001] This invention relates to the field of new energy materials technology, and in particular to a nano-solid hydrogen storage material and its preparation method, especially a magnesium-based nanocomposite hydrogen storage material with a core-shell structure, a multi-level catalytic system and a three-dimensional network framework synergistic enhancement and its preparation method. Background Technology

[0002] Hydrogen energy, as a clean, efficient, and renewable secondary energy source, is considered one of the ultimate energy solutions to the global energy crisis and environmental pollution problems. The large-scale application of hydrogen energy faces three major technological challenges: efficient hydrogen production, safe storage, and convenient utilization. Among these, hydrogen storage is the key technological bottleneck restricting the commercial development of hydrogen energy. Currently, mainstream hydrogen storage technologies include high-pressure gaseous hydrogen storage, cryogenic liquid hydrogen storage, and solid-state hydrogen storage. High-pressure gaseous hydrogen storage (35-70 MPa) suffers from poor safety and low volumetric capacity; cryogenic liquid hydrogen storage (-253℃) faces drawbacks such as high liquefaction energy consumption, large evaporation losses, and stringent requirements for tank insulation.

[0003] Solid-state hydrogen storage technology stores hydrogen in solid materials through physical adsorption or chemical hydride formation. It boasts advantages such as high volumetric hydrogen storage density, good safety, and mild operating conditions, making it one of the most promising hydrogen storage technologies. Among various solid-state hydrogen storage materials, magnesium-based hydrogen storage materials (Mg / MgH2) have become a research hotspot in the field due to their high hydrogen storage capacity (theoretical value 7.6 wt%), abundant resources, low cost, and good reversibility. However, the practical application of magnesium-based hydrogen storage materials faces three core challenges: First, high thermodynamic stability; the hydrogen dissociation enthalpy of MgH2 is as high as 74.7 kJ / molH2, resulting in a hydrogen release temperature typically exceeding 350℃. Second, poor kinetic performance; the slow diffusion rate of hydrogen atoms makes it difficult to meet the requirements of practical applications. Third, insufficient cycle stability; particle agglomeration and pulverization easily occur during long-term hydrogen absorption and desorption, leading to a decrease in hydrogen storage capacity.

[0004] To address the aforementioned issues, researchers both domestically and internationally have conducted extensive research. For example, Chinese patent CN114684784B discloses a solid magnesium-based hydrogen storage material, MgH2-MnV2O6, which uses a hydrothermal method to synthesize nano-flower-shaped MnV2O6 powder as a catalyst and ball-mills it with MgH2, significantly improving the hydrogen absorption and desorption rates. Chinese patent CN121023290B discloses a solid hydrogen storage material and its preparation method, which uses magnesium-based alloy powder, lightweight metal hydrides, nano-carbon materials, composite catalyst powder, and interface modifiers, ball-milled and then vacuum-sintered to achieve high hydrogen storage capacity and good cycle stability. A research team at Lawrence Berkeley National Laboratory in the United States has developed graphene nanoribbon encapsulation technology to stabilize nanocrystalline metal hydrides. Hyundai Motor Company and others have disclosed a hydrogen storage composite material in which metal hydrides are impregnated in a graphene oxide framework with an average pore size of 1-2 nm, achieving hydrogen release at lower temperatures. In addition, studies have used the MOF template method to synthesize Mg2FeH6@MCM-41 composite materials, which improve hydrogen storage performance through the nanoconfinement effect.

[0005] However, existing technologies still have the following shortcomings: First, the catalyst design is simple, mostly single-component or simple composite catalysts, lacking multi-level synergistic catalytic effects; second, nano-magnesium-based materials are prone to agglomeration during preparation and recycling, leading to a decrease in active surface area; third, the microstructure design of materials lacks systematicity and fails to achieve synergistic optimization of thermodynamics, kinetics and stability; fourth, the preparation process is complex and difficult to achieve large-scale production.

[0006] Therefore, developing a novel nanomaterial for hydrogen storage with high hydrogen storage capacity, low operating temperature, rapid hydrogen absorption and desorption kinetics, and excellent cycle stability, and establishing a simple, controllable preparation method suitable for large-scale production, is of great significance for promoting the commercial application of hydrogen energy technology. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a nano-solid hydrogen storage material and its preparation method. This nano-solid hydrogen storage material and its preparation method are characterized by a core-shell structure, a multi-level catalytic system, and a three-dimensional network framework that synergistically enhance the material. This nano-solid hydrogen storage material exhibits low hydrogen desorption temperature, rapid hydrogen absorption and desorption kinetics, and excellent cycle stability.

[0008] The above-mentioned objective of this invention is achieved through the following technical solutions: This invention provides a nano-solid hydrogen storage material having a core-shell structure, comprising a core and an outer shell. The core is a nano-magnesium-based hydrogen storage active phase, and the outer shell is a functionalized porous carbon material layer. The nano-magnesium-based hydrogen storage active phase contains in-situ grown multi-metal nanocatalyst particles. The functionalized porous carbon material layer is doped with non-metallic elements and loaded with metal-organic framework derivative nanoparticles. The core-shell structure is dispersed in a three-dimensional interconnected carbon-based network framework.

[0009] Through the above technical solution, this invention constructs a multi-scale, multi-component synergistic composite hydrogen storage material. Specifically, this structural design brings the following synergistic effects: First, the in-situ grown multi-metal nanocatalyst particles are directly embedded inside and on the surface of the magnesium-based hydrogen storage active phase, ensuring the maximum contact interface and the shortest mass transport distance between the catalyst and the active material, generating a "near-neighbor catalysis" effect, significantly reducing the dissociation energy barrier of hydrogen molecules and the diffusion activation energy of hydrogen atoms. Second, the functionalized porous carbon shell not only effectively suppresses the volume expansion and particle aggregation of the magnesium-based active phase during hydrogen adsorption and desorption cycles through physical confinement, but its doped non-metallic elements (such as N, B, and S) can also regulate the electronic structure of the carbon layer, enhance the interfacial bonding force with the magnesium-based active phase, and generate a "chemical anchoring" effect. At the same time, the metal-organic framework derivative nanoparticles loaded on the shell act as "nanoreactors" and "additional catalytic sites," forming a "dual-zone catalysis" mode with the multi-metal catalyst in the core, further optimizing the hydrogen adsorption-dissociation-diffusion pathway. Finally, the core-shell structural units described above are dispersed within a three-dimensional interconnected carbon-based network framework, constructing a high-speed electronic and thermal conduction network that runs throughout the entire material. This effectively solves the problem of reaction kinetic lag caused by poor thermal conductivity in hydrogen storage materials, achieving a perfect unity of "microscopic confinement" and "macroscopic support." The synergistic effect of the aforementioned multi-level structure enables the material of this invention to achieve significantly superior overall performance compared to existing technologies in terms of thermodynamics, kinetics, and cycle stability.

[0010] According to one embodiment of the present invention, the nano-magnesium-based hydrogen storage active phase is MgH2 or Mg2NiH4, with a particle size of 50-200 nm; the multi-metal nanocatalyst particles are selected from alloys or intermetallic compounds formed by at least two metals selected from Ti, V, Mn, Fe, Co, Ni, Zr, Nb, and Mo, with a particle size of 5-20 nm, and are uniformly distributed in the interior and surface of the nano-magnesium-based hydrogen storage active phase.

[0011] By selecting the aforementioned nanoscale magnesium-based hydrogen storage active phase and controlling its particle size within the range of 50-200 nm, the bulk diffusion distance of hydrogen atoms can be significantly shortened, which is the basis for improving the hydrogen absorption and desorption kinetics of hydrogen storage materials. Based on this, by uniformly distributing multi-metal alloy or intermetallic compound nanoparticles with a particle size of 5-20 nm inside and on the surface of the active phase, an unexpected synergistic catalytic effect is achieved. Compared with single-metal catalysts, multi-metal catalysts can more effectively weaken the strength of the Mg-H bond due to the electronic interactions between different metal atoms (such as d-band center shift and band structure reconstruction). According to density functional theory calculations, the multi-metal catalysts of this invention (such as Ti-V, Ni-Fe-Co, etc.) can reduce the hydrogen dissociation energy of MgH2 from 74.7 kJ / molH2 to 58-65 kJ / molH2, and their catalytic activity is far superior to that of single-metal catalysts (which typically only reduce it to 68-72 kJ / molH2). This synergistic effect at the electronic structure level is not possessed by single-metal or simple physical mixture catalysts and is one of the key innovations of this invention.

[0012] According to one embodiment of the present invention, the functionalized porous carbon material layer is a nitrogen-, boron-, and sulfur-co-doped porous carbon layer with a thickness of 5-30 nm, a specific surface area of ​​500-1500 m² / g, and an average pore size of 2-10 nm; the metal-organic framework derivative nanoparticles are selected from one or more derivatives of ZIF-8, ZIF-67, UiO-66, and MIL-101, and have a particle size of 10-50 nm.

[0013] The aforementioned technical solution further defines the composition and structure of the outer shell, resulting in synergistic effects: First, the nitrogen, boron, and sulfur co-doped porous carbon layer, by introducing heteroatoms with different electronegativity, creates a large number of structural defects and active sites in the carbon framework, significantly enhancing the affinity of the carbon layer for hydrogen molecules and providing more pathways for the rapid dissociation of hydrogen molecules. In particular, the co-doping of N, B, and S produces a "tri-element synergistic" effect: the lone pair electrons of N and the empty orbitals of B can form Lewis acid-base pairs, synergistically activating hydrogen molecules; while the introduction of S further modulates the spin density of the carbon layer, optimizing the adsorption energy of hydrogen atoms. This ternary co-doping effect is far superior to single-element or dual-element doping. Second, additionally loading MOF derivative nanoparticles (such as nitrogen-doped porous carbon derived from ZIF-8, Co@NC derived from ZIF-67, etc.) onto the outer shell forms a secondary structure of "particles attached to the shell". These MOF derivative particles possess high specific surface area and abundant pores, serving as active centers for the adsorption and dissociation of secondary hydrogen molecules. They complement the multi-metal catalyst within the core in both spatial and functional aspects. The core catalyst is responsible for the efficient dissociation of hydrogen molecules and promoting their diffusion into the magnesium-based active phase, while the MOF derivative particles on the outer shell are responsible for pre-enriching and initially activating hydrogen molecules. This "dual-zone synergistic catalysis" mode significantly enhances the overall hydrogen adsorption and desorption kinetics of the material.

[0014] According to one embodiment of the present invention, the three-dimensional interconnected carbon-based network framework is graphene, carbon nanotubes, porous carbon fibers, etc. The present invention also provides one or more three-dimensional network structures formed therefrom.

[0015] The core function of constructing a three-dimensional interconnected network framework using the aforementioned materials is to create macroscopic electron / heat conduction pathways. The hydrogen absorption and desorption processes involve strong exothermic and endothermic reactions, respectively, and the thermal conductivity of the materials directly determines the temperature uniformity and reaction rate of the reaction bed. By uniformly dispersing core-shell structural units within a three-dimensional network composed of highly thermally conductive carbon materials such as graphene and carbon nanotubes, close "point-to-surface" and "point-to-line" contacts are formed, significantly improving the thermal conductivity of the entire composite material. Experimental data show that the three-dimensional network structure of this invention increases the effective thermal conductivity of the material by 3-5 times compared to similar materials without a network structure. This effect, combined with the confinement and catalytic effects at the microscopic level, ensures the material's rapid reaction capability and long-term cycling stability in large-scale applications.

[0016] This invention also provides a method for preparing a nano-solid hydrogen storage material according to the above embodiments, comprising the following steps: Step S1: Prepare a multi-metal organic framework precursor solution; Step S2: Synthesize multimetal-organic framework nanoparticles using a solvothermal method in the presence of a template agent; Step S3: Chemically composite the multimetal-organic framework nanoparticles with magnesium and nickel sources to obtain the precursor complex; Step S4: Carbonize the precursor composite to obtain a porous carbon-coated multimetal nanocatalyst@magnesium-based composite material. Step S5: Combine the material obtained in step S4 with functionalized carbon sources and metal-organic framework derivatives to construct a three-dimensional network framework; Step S6: Perform high-pressure hydrogenation treatment to obtain nano-solid hydrogen storage material.

[0017] The design of the above preparation method also reflects the concept of synergistic enhancement. In particular, by combining the "MOF template method" with "chemical composite" and "carbonization treatment," the "in-situ growth" of multi-metal nanocatalysts within the magnesium-based active phase was achieved. This in-situ growth method is fundamentally different from traditional mechanical mixing or impregnation loading methods: in the MOF precursor, multi-metal ions are uniformly distributed at the atomic / molecular level; after carbonization and hydrogenation treatment, these metal ions are reduced in situ to alloy nanoparticles, while organic ligands are transformed into porous carbon, and magnesium and nickel sources form the magnesium-based active phase. This process ensures that a tightly bound "embedded" interface is formed between the catalyst particles and the active phase, rather than simple physical contact, thereby greatly improving the catalyst utilization efficiency and durability. In contrast, traditional ball milling methods (such as those commonly used in D1-D5) are difficult to achieve such uniform distribution and strong bonding; the catalyst is prone to agglomeration and detachment, leading to a rapid decrease in catalytic efficiency with increasing cycle number.

[0018] According to one embodiment of the present invention, the multi-metal organic framework precursor solution in step S1 comprises at least two metal ions and an organic ligand, wherein the metal ions are selected from Ti 4+ V 5+ Mn 2+ Fe 3+ Co 2+ Ni 2+ Zr 4+ 、Nb 5+ Mo 6+ At least two of the organic ligands are selected from terephthalic acid, trimesic acid, and 2-methylimidazole; The template agent mentioned in step S2 is selected from one of polymethyl methacrylate, polystyrene, and silica nanospheres, with a particle size of 100-300 nm; the solvothermal reaction temperature is 100-200℃, and the reaction time is 12-48 hours.

[0019] According to one embodiment of the present invention, the chemical compounding in step S3 is a liquid-phase reduction method or a mechanical ball milling method; the liquid-phase reduction method includes reacting polymetallic organic framework nanoparticles with magnesium salts and nickel salts in the presence of a reducing agent, wherein the reducing agent is selected from sodium borohydride, lithium aluminum hydride, and hydrazine hydrate; the present invention also provides a method for mechanical ball milling, wherein polymetallic organic framework nanoparticles are ball milled with magnesium powder and nickel powder under an inert atmosphere, the ball milling speed is 200-500 rpm, and the ball milling time is 5-20 hours.

[0020] According to one embodiment of the present invention, the carbonization process in step S4 is carried out under an inert atmosphere or a reducing atmosphere, the carbonization temperature is 500-800℃, the heating rate is 1-10℃ / min, and the holding time is 1-5 hours; the inert atmosphere is argon, nitrogen, or one or more of the present invention, and the reducing atmosphere is a hydrogen-argon mixture or ammonia.

[0021] According to one embodiment of the present invention, the functionalized carbon source in step S5 is selected from graphene oxide, carbon nanotubes, porous carbon fibers, and one or more of the present invention. The functionalization includes nitrogen doping, boron doping, sulfur doping, and one or more of the present invention. The metal-organic framework derivative is ZIF-8, ZIF-67, UiO-66, MIL-101, and one or more of the present invention are porous carbon materials obtained by pyrolysis. The composite method is liquid phase self-assembly or electrostatic spray deposition.

[0022] The liquid-phase self-assembly or electrostatic spray deposition method used in step S5, combined with functionalized carbon sources and MOF derivatives, is crucial for constructing the macroscopic structure of "core-shell structural units @ three-dimensional network framework". In particular, the electrostatic spray deposition method can enable charged core-shell structural units to undergo ordered self-assembly with functionalized carbon sources (such as graphene oxide) under the influence of an electric field, forming a more continuous and uniform three-dimensional network structure. The advantage of this method is that it not only achieves physically uniform dispersion but also enhances the interfacial bonding force between units and the network through electrostatic forces, which is essential for maintaining the structural integrity of the material during long-term cycling.

[0023] According to one embodiment of the present invention, the hydrogen pressure of the high-pressure hydrogenation treatment in step S6 is 3-10 MPa, the temperature is 200-400°C, and the time is 2-10 hours.

[0024] This invention also provides the application of the aforementioned nano-solid hydrogen storage material in hydrogen fuel cell vehicles, portable power supplies, and stationary energy storage systems.

[0025] In summary, compared with the prior art, the present invention has at least one of the following beneficial technical effects: Significant optimization of thermodynamic properties: This invention effectively reduces the hydrogen dissociation energy barrier of MgH2 through the synergistic effect of multi-metal nanocatalysts. Specifically, the d-band center of the multi-metal catalyst (such as Ti-V, Ni-Fe-Co, etc.) undergoes strong hybridization with the s orbital of the hydrogen atom, significantly weakening the strength of the Mg-H bond. According to density functional theory calculations, the multi-metal catalyst of this invention can reduce the hydrogen dissociation energy of MgH2 from 74.7 kJ / molH2 to 58-65 kJ / molH2. Correspondingly, the initial hydrogen desorption temperature of the material is reduced from above 350℃ to 180-220℃, and the hydrogen desorption plateau pressure is increased to 0.1-0.5 MPa (300℃), significantly improving the thermodynamic properties of the material.

[0026] Comprehensive Enhancement of Kinetic Performance: The core-shell structure and three-dimensional network framework design of this invention provide multiple channels for the rapid diffusion of hydrogen atoms. On the one hand, the nanoscale magnesium-based active phase (50-200 nm) significantly shortens the diffusion distance of hydrogen atoms; on the other hand, the micropores and mesopores in the porous carbon shell provide abundant adsorption sites and diffusion pathways for hydrogen molecules. More importantly, the in-situ grown multi-metal nanocatalyst (5-20 nm) is uniformly distributed inside and on the surface of the active phase, providing a large number of catalytic active sites and significantly reducing the activation energy for hydrogen molecule dissociation and hydrogen atom diffusion. Experimental results show that the material of this invention can absorb more than 90% of its theoretical capacity within 5 minutes under 200℃ and 3 MPa hydrogen pressure conditions; and can release more than 85% of its theoretical capacity within 15 minutes under 200℃ and 0.1 MPa conditions.

[0027] Significantly enhanced cycling stability: This invention suppresses capacity decay during cycling through multiple synergistic mechanisms. First, the functionalized porous carbon shell acts as a physical barrier, effectively limiting the volume expansion and particle aggregation of the magnesium-based active phase during hydrogen adsorption and desorption. Second, the three-dimensional interconnected carbon-based network framework provides a stable support structure for the active phase, preventing particle detachment and migration. Third, metal-organic framework derivative nanoparticles act as "nanoanchors," forming strong interfacial bonds with the active phase, further enhancing structural stability. Experimental results show that the material of this invention retains 92-96% of its hydrogen storage capacity after 100 hydrogen adsorption and desorption cycles, far superior to existing technologies.

[0028] Significantly improved environmental stability: The functionalized porous carbon shell of this invention exhibits excellent hydrophobicity and chemical inertness, effectively preventing the corrosion of the magnesium-based active phase by oxygen and moisture in the air. Experimental results show that after exposure to air with a relative humidity of 40% for 24 hours, the hydrogen storage capacity of the material of this invention shows no significant loss; after exposure to air with a relative humidity of 60% for 8 hours, the hydrogen storage capacity retention rate is still higher than 85%. This characteristic greatly reduces the operational requirements during material preparation, storage, and application.

[0029] Controllability and scalability of the preparation process: This invention employs a metal-organic framework template method combined with chemical composite technology to achieve in-situ growth and uniform distribution of multi-metal nanocatalysts, avoiding the problems of uneven catalyst distribution and material structure damage that are easily caused by traditional ball milling methods. Simultaneously, through processes such as liquid-phase self-assembly and high-pressure hydrogenation, the precise construction of the core-shell structure and three-dimensional network framework is achieved. The entire preparation process is characterized by mild conditions, controllable processes, and good reproducibility, making it suitable for industrial production.

[0030] In addition, the present invention also brings the following unexpected technical effects: First, a "catalysis-confinement-conduction" coupling effect is generated between the multi-metal catalyst and the functionalized carbon shell. Specifically, the highly efficient catalytic effect of the multi-metal catalyst enables the hydrogen absorption and desorption reactions to proceed rapidly at relatively low temperatures, while the functionalized carbon shell not only prevents the migration and aggregation of the catalyst and active phase through physical confinement, but its excellent thermal conductivity also allows for the timely transfer of reaction heat (endothermic or exothermic during hydrogen absorption) away, avoiding the negative impact of local overheating or overcooling on reaction kinetics. This coupling effect of "highly efficient reaction + rapid heat conduction" results in the material of this invention exhibiting performance far exceeding the expectations of static testing under dynamic operating conditions (such as the frequent charging and discharging processes of on-board hydrogen storage systems).

[0031] Second, the non-metallic elements (N, B, S) doped in the outer shell and the multi-metallic catalyst in the core form an "electronic complementarity" effect. X-ray photoelectron spectroscopy (XPS) analysis shows that there are strong electronic interactions between the N, B, and S atoms in the outer shell and the metal atoms such as Mg, Ti, and V in the core, leading to changes in the electron density of the metal atoms, thereby further optimizing their adsorption and activation capabilities for hydrogen molecules. This remote electronic modulation effect across the core-shell interface is something that those skilled in the art would find difficult to foresee with existing technology.

[0032] Third, the loading of MOF derivative nanoparticles onto the carbon shell, together with the three-dimensional network framework, constructs a hierarchical porous structure. Specifically, the MOF derivatives provide micropores (<2 nm), the carbon shell provides mesopores (2-10 nm), and the three-dimensional network framework provides macropores (>50 nm). This hierarchical structure of micropores-mesopores-macropores provides multi-level transport channels for hydrogen molecules from macroscopic to microscopic scales, enabling rapid "highway-like" transport of hydrogen. The synergistic effect of this hierarchical porous structure makes the hydrogen adsorption and desorption kinetics of the material far superior to materials with only a single-scale pore structure. Attached Figure Description

[0033] Figure 1 This is a flowchart of the preparation method of the present invention. Detailed Implementation

[0034] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0035] In the description of this application, it should be noted that the terms "upper," "lower," "inner," "outer," "top / bottom," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application 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, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0036] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installed," "equipped with," "sleeved / connected," "connected," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0037] Example 1 Reference Figure 1 This embodiment provides a nano-solid hydrogen storage material and its preparation method, the specific steps of which are as follows: Step S1: Preparation of multi-metal-organic framework precursor solution Weigh 0.5 mmol of titanium tetrachloride (TiCl4) and 0.5 mmol of vanadium chloride (VCl3) and dissolve them in 20 mL of N,N-dimethylformamide (DMF). Stir magnetically for 30 minutes until completely dissolved. Weigh 2.0 mmol of terephthalic acid (H2BDC) and dissolve it in 20 mL of DMF. Stir for 30 minutes. Combine the two solutions and continue stirring for 1 hour to obtain a Ti-containing solution. 4+ and V 3+ Multimetallic organic framework precursor solution.

[0038] Step S2: Synthesis of polymetallic organic framework nanoparticles via solvothermal method Add 0.5 g of polystyrene template agent with a particle size of 150 nm to the precursor solution obtained in step S1, and disperse by ultrasonication for 30 minutes. Transfer the mixture to a 100 mL high-pressure reactor lined with polytetrafluoroethylene, seal it, and place it in an oven to react at 150 °C for 24 hours. After the reaction is complete, allow it to cool naturally to room temperature, centrifuge to obtain the solid product, wash it three times with DMF and anhydrous ethanol, and dry it in a vacuum drying oven at 60 °C for 12 hours to obtain multi-metal-organic framework nanoparticles (Ti-V-MOF).

[0039] Step S3: Chemical synthesis to prepare precursor complex Chemical composite formation was performed using a liquid-phase reduction method. 0.5 g of Ti-V-MOF nanoparticles obtained in step S2 were dispersed in 100 mL of anhydrous ethanol and ultrasonically dispersed for 30 minutes. 1.0 g of magnesium chloride (MgCl2) and 0.2 g of nickel chloride (NiCl2) were added, and the mixture was stirred for 2 hours to allow for complete adsorption of metal ions. 50 mL of a 0.5 M sodium borohydride (NaBH4) ethanol solution was prepared and slowly added dropwise to the above mixture. The reaction was carried out at room temperature for 6 hours under nitrogen protection. After the reaction was complete, the mixture was centrifuged, washed three times with anhydrous ethanol, and dried in a vacuum oven at 60 °C for 12 hours to obtain the precursor composite.

[0040] Step S4: Carbonization treatment The precursor composite obtained in step S3 was placed in a tube furnace and carbonized under an argon atmosphere. The temperature was increased to 600℃ at a rate of 5℃ / min, held for 3 hours, and then allowed to cool naturally to room temperature. During carbonization, the organic ligands in the MOF were converted into porous carbon, while metal ions were reduced to metal nanoparticles, resulting in a porous carbon-coated Ti-V alloy nanocatalyst@magnesium-based composite material. X-ray diffraction and transmission electron microscopy analysis revealed that the material has a core-shell structure, with a core of Mg / Mg₂Ni phase with a particle size of approximately 80-120 nm, and a shell of nitrogen-doped porous carbon layer with a thickness of approximately 10-20 nm. The Ti-V alloy nanocatalyst particles, with a size of approximately 8-15 nm, were uniformly distributed within the core.

[0041] Step S5: Construct the 3D network skeleton (1) Preparation of functionalized carbon source: 0.1 g of graphene oxide was dispersed in 50 mL of deionized water and sonicated for 1 hour to obtain a uniform dispersion. 0.5 g of urea (nitrogen source), 0.1 g of boric acid (boron source) and 0.1 g of thiourea (sulfur source) were added, stirred and dissolved, and then transferred to a hydrothermal reactor and reacted at 180 °C for 12 hours. The reaction product was centrifuged, washed and freeze-dried to obtain nitrogen, boron and sulfur co-doped reduced graphene oxide (N,B,S-rGO).

[0042] (2) Preparation of metal-organic framework derivatives: 0.5g of ZIF-8 nanoparticles were placed in a tube furnace and heated to 800℃ at 5℃ / min under an argon atmosphere. The temperature was maintained for 2 hours to perform carbonization treatment, and ZIF-8-derived porous carbon nanoparticles (ZIF-8-C) with a particle size of about 30-50nm were obtained.

[0043] (3) Liquid-phase self-assembly composite: 0.2 g of the material obtained in step S4 and 0.1 g of N,B,S-rGO were dispersed in 50 mL of anhydrous ethanol and ultrasonically dispersed for 1 hour. 0.05 g of ZIF-8-C was added and ultrasonication was continued for 30 minutes. The mixture was stirred and the solvent was evaporated at 60 °C to obtain the composite product.

[0044] Step S6: High-pressure hydrogenation treatment The composite product obtained in step S5 was placed in a high-pressure reactor, evacuated, and then filled with high-purity hydrogen to a pressure of 5 MPa. The temperature was raised to 300°C and held for 6 hours for hydrogenation. After hydrogenation, the product was allowed to cool naturally to room temperature and then removed under argon protection to obtain the nano-solid hydrogen storage material.

[0045] The nano-solid hydrogen storage material prepared in this embodiment, observed by transmission electron microscopy (TEM), exhibits a clear core-shell structure, with a magnesium-based active phase in the core and a carbon material layer in the outer shell. High-resolution transmission electron microscopy (HRTEM) images show that the carbon shell has a distinct layered structure with a thickness of approximately 15 nm, and nano-catalyst particles with clearly defined lattice fringes are distributed within the core, with interplanar spacing matching the characteristic crystal faces of Ti-V alloys.

[0046] X-ray diffraction (XRD) analysis showed that the main phases of the material were MgH2 and Mg2NiH4, with diffraction peaks of Ti-V alloy also present, and no other impurity phases. Nitrogen adsorption-desorption tests showed that the material had a specific surface area of ​​785 m² / g, and the pore size was mainly distributed in the range of 2-5 nm and 10-30 nm, exhibiting a typical mesoporous-macroporous hierarchical pore structure.

[0047] Temperature-programmed desorption (TPD) testing showed that the initial hydrogen release temperature of the material was 185℃, and the peak hydrogen release temperature was 245℃, which is much lower than the hydrogen release temperature of pure MgH2 (>350℃). Under conditions of 200℃ and 3MPa hydrogen pressure, the material achieved a hydrogen absorption capacity of 5.8wt% within 5 minutes and 6.2wt% within 10 minutes (more than 90% of the theoretical capacity); under conditions of 200℃ and 0.1MPa, the material achieved a hydrogen release capacity of 5.1wt% within 10 minutes and 5.6wt% within 15 minutes. Cyclic stability testing showed that after 100 hydrogen absorption and desorption cycles, the material retained 94.2% of its hydrogen storage capacity, demonstrating excellent cycle stability.

[0048] Further characterization of the materials prepared in this embodiment revealed that their synergistic mechanism is manifested in the following aspects: 1. Catalytic Synergy: X-ray photoelectron spectroscopy (XPS) analysis revealed that the binding energies of Ti2p and V2p in the Ti-V alloy nanocatalyst shifted compared to the standard values ​​for pure metals, indicating electron transfer between Ti and V, resulting in an optimized d-band electronic structure. This electronic structure lowers the activation barrier for hydrogen molecule dissociation to 0.35 eV, significantly lower than the 1.2 eV of pure MgH2.

[0049] 2. Structural Synergy: Using focused ion beam scanning electron microscopy (FIB-SEM) three-dimensional reconstruction technology, it was observed that core-shell structured particles are uniformly anchored on a three-dimensional network framework composed of N,B,S-rGO, forming an integrated "particle-network" conductive and thermally conductive structure. Thermal conductivity tests show that the thermal conductivity of this composite material is as high as 15 W / (m·K), which is 15 times that of pure MgH2 (approximately 1 W / (m·K)).

[0050] 3. Interface Synergy: Electron Energy Loss Spectroscopy (EELS) line scan analysis revealed a significant interdiffusion region between the N, B, and S elements in the carbon shell and the Mg element in the core, forming a transition layer of approximately 2-3 nm. This "chemically interlocked" structure is key to the material's excellent cycle stability, effectively buffering the volume change stress during hydrogen absorption and desorption and preventing interface delamination.

[0051] Example 2 The difference between this embodiment and Example 1 is that a different metal combination is used in step S1. Specifically, 0.3 mmol of nickel chloride (NiCl2) and 0.7 mmol of cobalt chloride (CoCl2) are weighed and dissolved in DMF, and 2-methylimidazole (2.0 mmol) is used as the organic ligand. The remaining steps are the same as in Example 1.

[0052] Characterization revealed that the multi-metal catalyst in the material prepared in this embodiment is a Ni-Co alloy with a particle size of approximately 6-12 nm, uniformly distributed in the magnesium-based active phase. The initial hydrogen release temperature of the material is 195°C, and the hydrogen absorption capacity is 6.0 wt% within 10 minutes at 200°C and 3 MPa hydrogen pressure. After 100 cycles, the capacity retention rate is 93.5%.

[0053] In this embodiment, the synergistic catalytic mechanism of the Ni-Co alloy catalyst differs from that of the Ti-V alloy in Example 1. Both Ni and Co are ferromagnetic metals, and the coupling of their d-band electronic structures produces a stronger spin polarization effect, which is beneficial to the breaking of σ bonds in hydrogen molecules, thus exhibiting excellent catalytic activity.

[0054] Example 3 The difference between this embodiment and Embodiment 1 is that mechanical ball milling is used for chemical compounding in step S3. Specifically, 0.5g of Ti-V-MOF nanoparticles, 1.0g of magnesium powder, and 0.2g of nickel powder are placed in a ball mill jar and ball milled at 400rpm for 10 hours under argon protection. The remaining steps are the same as in Embodiment 1.

[0055] Characterization showed that the material prepared in this embodiment has a core-shell structure similar to that of Example 1, with slightly larger (10-20 nm) and uniformly distributed multi-metal catalyst particles. The initial hydrogen release temperature of the material was 188 °C, and the hydrogen absorption capacity was 5.9 wt% within 10 minutes at 200 °C and 3 MPa hydrogen pressure. After 100 cycles, the capacity retention rate was 92.8%.

[0056] This embodiment demonstrates that mechanical ball milling is also applicable to the preparation process of this invention. Through the mechanical energy and local thermal effect provided by high-energy ball milling, it can also promote the effective composite of MOF nanoparticles with magnesium and nickel sources, providing flexibility in process selection for industrial production.

[0057] Example 4 The difference between this embodiment and Embodiment 1 is that electrostatic spray deposition is used for composite deposition in step S5. Specifically, 0.2g of the material obtained in step S4 is dispersed in ethanol, and 0.1g of N,B,S-rGO and 0.05g of ZIF-8-C are added. After ultrasonic dispersion, the mixture is used as the spray solution. The spray voltage is set to 15kV, the receiving distance to 10cm, and the feed rate to 1mL / h. The composite product is collected on aluminum foil. The remaining steps are the same as in Embodiment 1.

[0058] Characterization revealed that the core-shell structured particles in the material prepared in this embodiment were uniformly dispersed in a three-dimensional carbon network, resulting in a more continuous network structure and better conductivity. The initial hydrogen release temperature of the material was 182°C, and the hydrogen absorption capacity was 6.1 wt% within 10 minutes at 200°C and 3 MPa hydrogen pressure. After 100 cycles, the capacity retention rate was 95.1%.

[0059] In this embodiment, the electrostatic spray deposition method, compared to the liquid-phase self-assembly method, can more precisely control the distribution of core-shell structural units in the three-dimensional network, avoiding local agglomeration caused by solvent evaporation, resulting in a more uniform and continuous network structure. Electrochemical impedance spectroscopy (EIS) tests show that the charge transfer resistance of the material in this embodiment is only 60% of that of the material in Example 1, confirming a superior electronic conduction path. This is the main reason why the cycling stability of the material in this embodiment (95.1%) is better than that of Example 1 (94.2%).

[0060] Example 5 The difference between this embodiment and Embodiment 1 is that carbon nanotubes (CNTs) are used instead of graphene oxide as the functionalized carbon source in step S5. Specifically, 0.1g of carboxylated carbon nanotubes are dispersed in 50mL of deionized water, and 0.5g of urea, 0.1g of boric acid, and 0.1g of thiourea are added. The mixture is then subjected to hydrothermal treatment to obtain N,B,S-CNTs. The remaining steps are the same as in Embodiment 1.

[0061] Characterization revealed that in the material prepared in this embodiment, carbon nanotubes form a three-dimensional network framework, with core-shell structured particles attached to the surface of the carbon nanotubes. The initial hydrogen release temperature of the material was 190°C, and the hydrogen absorption capacity was 5.8 wt% within 10 minutes at 200°C and 3 MPa hydrogen pressure. After 100 cycles, the capacity retention rate was 92.5%.

[0062] This embodiment demonstrates that carbon nanotubes, as a one-dimensional high thermal conductivity carbon material, can also construct an effective three-dimensional network framework. Although its specific surface area (approximately 200-300 m² / g) is lower than that of graphene oxide (>500 m² / g), its unique one-dimensional structure is beneficial for constructing long-range conductive networks and forming "point-line" contacts, which not only ensure electron / thermal conduction but also play a role in dispersion and support.

[0063] Example 6 The difference between this embodiment and Embodiment 1 is that the hydrogenation treatment in step S6 is carried out at a temperature of 250°C, a pressure of 4 MPa, and a time of 8 hours. The remaining steps are the same as in Embodiment 1.

[0064] Characterization revealed that the magnesium-based active phase in the material prepared in this embodiment is mainly MgH2 phase, with a slightly small grain size (50-80 nm). The initial hydrogen release temperature of the material is 178 °C, and the hydrogen absorption capacity is 6.2 wt% within 10 minutes at 200 °C and 3 MPa hydrogen pressure. After 100 cycles, the capacity retention rate is 94.5%.

[0065] This embodiment demonstrates that the initial grain size of the magnesium-based active phase can be controlled by optimizing the hydrogenation treatment conditions (especially by reducing the temperature). Smaller grain sizes (50-80 nm) provide more grain boundaries and defect sites, which are themselves rapid diffusion channels for hydrogen atoms, thus further reducing the initial hydrogen desorption temperature to 178 °C. This demonstrates the important role of nanoscale technology and grain boundary engineering in this invention.

[0066] Example 7 The difference between this embodiment and Embodiment 1 is that in step S2, the template agent is silica nanospheres (particle size 200 nm), and in step S4, the template agent is removed by etching with hydrofluoric acid after carbonization. The remaining steps are the same as in Embodiment 1.

[0067] Characterization revealed that the material prepared in this embodiment possesses a larger specific surface area (950 m² / g) and a more abundant pore structure. The initial hydrogen expulsion temperature of the material is 175 °C, and the hydrogen absorption capacity is 6.3 wt% within 10 minutes at 200 °C and 3 MPa hydrogen pressure. After 100 cycles, the capacity retention rate is 95.8%.

[0068] In this embodiment, by introducing an additional template etching step, more macroporous structures (>50 nm) were introduced into the shell and three-dimensional network, forming a more developed hierarchical pore structure of "micropore-mesopore-macropore". This hierarchical pore structure endows the material with a higher specific surface area and porosity, providing more adsorption sites and fast transport channels for hydrogen, thus achieving the best hydrogen adsorption capacity (6.3 wt%) and cycle stability (95.8%) in this series of embodiments. This result fully demonstrates the necessity and synergistic effect of the hierarchical pore structure design.

[0069] Example 8 The difference between this embodiment and Embodiment 1 is that three metal ions are used in step S1: 0.3 mmol titanium tetrachloride, 0.3 mmol vanadium chloride, and 0.4 mmol ferric chloride (FeCl3) are weighed. The remaining steps are the same as in Embodiment 1.

[0070] Characterization revealed that the multi-metal catalyst in the material prepared in this embodiment is a Ti-V-Fe ternary alloy with a particle size of approximately 5-12 nm. The initial hydrogen release temperature of the material is 168 °C, and the hydrogen absorption capacity is 6.3 wt% within 10 minutes at 200 °C and 3 MPa hydrogen pressure. After 100 cycles, the capacity retention rate is 94.8%.

[0071] In this embodiment, the Ti-V-Fe ternary alloy catalyst exhibited the best catalytic activity (initial hydrogen desorption temperature as low as 168°C). Theoretical calculations show that the alloy phase formed by Ti, V, and Fe metal atoms at the nanoscale has a further optimized adjustment of the d-band center position compared to the binary alloy, achieving a near-perfect energy level match with the s orbitals of hydrogen atoms, thereby maximally weakening the Mg-H bond. This result clearly demonstrates the unexpected technical effect of "ternary synergy" over "binary synergy" in multi-metal catalyst design.

[0072] Example 9 The difference between this embodiment and Example 1 is that the metal-organic framework derivative used in step S5 is a ZIF-67 derivative (Co@NC). Specifically, 0.5g of ZIF-67 nanoparticles are carbonized at 800°C for 2 hours to obtain Co@NC. The remaining steps are the same as in Example 1.

[0073] Characterization revealed that in the material prepared in this embodiment, ZIF-67-derived Co@NC nanoparticles were uniformly loaded within a carbon framework, providing additional catalytic active sites. The initial hydrogen desorption temperature of the material was 172°C, and the hydrogen absorption capacity was 6.1 wt% within 10 minutes at 200°C and 3 MPa hydrogen pressure. After 100 cycles, the capacity retention rate was 94.0%.

[0074] In this embodiment, the ZIF-67-derived Co@NC not only provides a porous carbon structure, but its internal Co nanoparticles are also a highly efficient hydrogen storage catalyst. Therefore, the material's shell simultaneously possesses the physical confinement and chemical anchoring effects provided by N,B,S-rGO, as well as the additional catalytic effect provided by Co@NC. This "one shell, multiple functions" design further enhances the material's overall performance, with an initial hydrogen desorption temperature superior to that of Example 1 (185°C) and Example 5 (190°C), demonstrating the synergistic advantages of the multifunctional shell.

[0075] Example 10 The difference between this embodiment and Embodiment 1 is that the solvothermal reaction temperature in step S2 is 120°C and the reaction time is 48 hours. The remaining steps are the same as in Embodiment 1.

[0076] Characterization revealed that the Ti-V-MOF nanoparticles prepared in this embodiment exhibited more uniform size (approximately 100 nm) and a more regular core-shell structure after carbonization. The initial hydrogen release temperature of the material was 183 °C, and the hydrogen absorption capacity was 6.0 wt% within 10 minutes at 200 °C and 3 MPa hydrogen pressure. After 100 cycles, the capacity retention rate was 93.5%.

[0077] This embodiment demonstrates that by adjusting the solvothermal reaction conditions, the size and uniformity of the MOF template can be precisely controlled, thereby achieving regulation of the size and morphology of the final core-shell structural units. A more regular core-shell structure facilitates more uniform catalytic distribution and more effective physical confinement, thus ensuring the stable performance of the material.

[0078] Comparative Example 1 The difference between this comparative example and Example 1 is that MOF synthesis in steps S1 and S2 is not performed. Instead, TiCl4 and VCl3 are directly ball-milled and compounded with magnesium powder and nickel powder in step S3. The remaining steps are the same as in Example 1.

[0079] Characterization revealed that the Ti-V catalyst in the material prepared in this comparative example was unevenly distributed, exhibiting significant agglomeration and an incomplete core-shell structure. The initial hydrogen release temperature of the material was 245℃, and the hydrogen absorption capacity was only 3.2 wt% within 30 minutes at 200℃ and 3 MPa hydrogen pressure. After 100 cycles, the capacity retention rate was 72.5%.

[0080] Comparative Example 2 The difference between this comparative example and Example 1 is that carbonization is not performed in step S4, while the remaining steps are the same as in Example 1.

[0081] Characterization revealed that the material prepared in this comparative example lacked a carbon shell protection, and the magnesium-based active phase underwent severe agglomeration during hydrogenation. The initial hydrogen release temperature of the material was 268℃, and the hydrogen absorption capacity was 2.8 wt% within 30 minutes at 200℃ and 3 MPa hydrogen pressure. After 100 cycles, the capacity retention rate was 58.3%.

[0082] Comparative Example 3 The difference between this comparative example and Example 1 is that a three-dimensional network skeleton is not constructed in step S5, that is, N,B,S-rGO and ZIF-8-C are not added. The remaining steps are the same as in Example 1.

[0083] Characterization revealed that the material prepared in this comparative example consisted of dispersed particles without three-dimensional network support. The initial hydrogen release temperature of the material was 195℃, and the hydrogen absorption capacity was 4.8 wt% within 10 minutes at 200℃ and 3 MPa hydrogen pressure. After 100 cycles, the capacity retention rate was 78.6%.

[0084] Comparative Example 4 The difference between this comparative example and Example 1 is that a single metal ion (TiCl4 only) is used in step S1, while the other steps are the same as in Example 1.

[0085] Characterization revealed that the catalyst in the material prepared in this comparative example was TiO2 nanoparticles, with no alloy phase formation. The initial hydrogen desorption temperature of the material was 212℃, and the hydrogen absorption capacity was 4.5 wt% within 10 minutes at 200℃ and 3 MPa hydrogen pressure. After 100 cycles, the capacity retention rate was 82.3%.

[0086] Comparative Example 5 The difference between this comparative example and Example 1 is that the carbon source is not doped in step S5; graphene oxide is used directly. The remaining steps are the same as in Example 1.

[0087] Characterization revealed that the carbon shell of the material prepared in this comparative example was free of heteroatom doping and exhibited strong surface chemical inertness. The initial hydrogen release temperature of the material was 198℃, and the hydrogen absorption capacity was 5.2 wt% within 10 minutes at 200℃ and 3 MPa hydrogen pressure. After 100 cycles, the capacity retention rate was 85.7%.

[0088] The results of Comparative Examples 1-5 further validate the necessity and synergy of the various technical features of this invention. Comparative Example 1 (without MOF template) and Comparative Example 4 (single metal catalyst) jointly demonstrate that "in-situ grown multi-metal nanocatalysts" are key to obtaining excellent catalytic effects. Comparative Example 2 (without carbon shell) demonstrates the importance of the carbon shell in preventing aggregation and maintaining the nanostructure. Comparative Example 3 (without three-dimensional network) demonstrates the crucial role of the three-dimensional network in improving the hydrogen adsorption / desorption rate (especially the hydrogen adsorption capacity, which decreased from 6.2 wt% in Example 1 to 4.8 wt%) and cycle stability. Comparative Example 5 (without functionalized doping) demonstrates the value of non-metallic element doping in optimizing interfacial bonding and improving stability.

[0089] Performance Comparison The properties of the materials prepared in Examples 1-10 and Comparative Examples 1-5 were compared, and the results are shown in Table 1.

[0090] Table 1 Comparison of properties of different materials

[0091] As shown in Table 1, the nano-solid hydrogen storage materials prepared in Examples 1-10 of this invention are significantly superior to the comparative materials in terms of initial hydrogen release temperature, hydrogen absorption kinetics, and cycle stability. Among them, Example 8, using a Ti-V-Fe ternary alloy catalyst, achieved the best initial hydrogen release temperature (168°C), while Example 7, using a template agent-assisted preparation, achieved the highest hydrogen absorption capacity (6.3 wt%) and the best cycle stability (95.8%).

[0092] The technical effect of this invention stems from the synergistic effect of multi-scale structural design: Atomic / molecular scale: There is an electronic synergistic effect between different metal atoms in the multi-metal nanocatalyst, which modulates the d-band center position of the catalyst and optimizes the interaction energy with hydrogen molecules, thereby reducing the hydrogen dissociation energy barrier.

[0093] Nanoscale: In the core-shell structure, the nano-magnesium-based active phase shortens the diffusion distance of hydrogen atoms, while the porous carbon shell provides a fast transport channel for hydrogen molecules and acts as a physical barrier to prevent the aggregation of the active phase.

[0094] Submicron / micron scale: The three-dimensional interconnected carbon-based network framework constructs an efficient electron / thermal conduction network, which is beneficial for heat transfer and electron transfer during hydrogen adsorption and desorption, while providing stable mechanical support for the active phase.

[0095] Interface effect: Heteroatoms (N, B, S) in the functionalized carbon shell form strong interfacial interactions with the magnesium-based active phase, reducing the interfacial energy and enhancing structural stability. Metal-organic framework derivative nanoparticles, acting as "nanoanchors," further enhance the interfacial bonding between the active phase and the carbon skeleton.

[0096] The synergistic effect of the aforementioned multi-scale structure enables the material of this invention to achieve comprehensive improvements in thermodynamics, kinetics, and stability, with overall performance significantly superior to existing technologies.

[0097] The nano-solid hydrogen storage material of this invention has a mature preparation process, conventional equipment, and readily available raw materials, making it suitable for large-scale production. The material can be widely used in on-board hydrogen storage systems for hydrogen fuel cell vehicles, portable power supplies, distributed power generation systems, hydrogen energy storage power stations, and other fields, showing promising market prospects and economic benefits.

[0098] The implementation principle of this invention is as follows: This invention discloses a nano-solid hydrogen storage material and its preparation method, belonging to the field of new energy materials technology. The nano-solid hydrogen storage material has a core-shell structure, comprising a nano-magnesium-based active phase core and a functionalized porous carbon material outer shell; the core contains in-situ grown multi-metal nanocatalyst particles; the outer shell is doped with non-metallic elements and loaded with metal-organic framework derivative nanoparticles; the core-shell structure is dispersed in a three-dimensional interconnected carbon-based network framework. The preparation method includes: preparing a multi-metal-organic framework precursor solution; synthesizing multi-metal-organic framework nanoparticles by a solvothermal method; chemically combining with a magnesium source and a nickel source to obtain a precursor composite; carbonization treatment to obtain a porous carbon-coated multi-metal nanocatalyst@magnesium-based composite material; constructing a three-dimensional network framework by combining with a functionalized carbon source and metal-organic framework derivatives; and high-pressure hydrogenation treatment. The material of this invention exhibits low hydrogen desorption temperature, rapid hydrogen absorption and desorption kinetics, and excellent cycle stability.

[0099] The embodiments described herein are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape, and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A nano-solid-state hydrogen storage material, characterized in that, The material has a core-shell structure, including a core and an outer shell. The core is a nano-magnesium-based hydrogen storage active phase, and the outer shell is a functionalized porous carbon material layer. The nano-magnesium-based hydrogen storage active phase contains in-situ grown multi-metal nanocatalyst particles. The functionalized porous carbon material layer is doped with non-metallic elements and loaded with metal-organic framework derivative nanoparticles. The core-shell structure is dispersed in a three-dimensional interconnected carbon-based network framework.

2. The nano-solid hydrogen storage material according to claim 1, characterized in that, The nano-magnesium-based hydrogen storage active phase is MgH2 or Mg2NiH4, with a particle size of 50-200 nm; the multi-metal nanocatalyst particles are selected from alloys or intermetallic compounds formed by at least two metals selected from Ti, V, Mn, Fe, Co, Ni, Zr, Nb, and Mo, with a particle size of 5-20 nm, and are uniformly distributed inside and on the surface of the nano-magnesium-based hydrogen storage active phase.

3. The nano-solid-state hydrogen storage material according to claim 1, characterized in that, The functionalized porous carbon material layer is a nitrogen, boron, and sulfur co-doped porous carbon layer with a thickness of 5-30 nm, a specific surface area of ​​500-1500 m² / g, and an average pore size of 2-10 nm; the metal-organic framework derivative nanoparticles are selected from one or more derivatives of ZIF-8, ZIF-67, UiO-66, and MIL-101, and have a particle size of 10-50 nm.

4. The nano-solid hydrogen storage material according to claim 1, characterized in that, The three-dimensional interconnected carbon-based network framework is a three-dimensional network structure formed by one or more of graphene, carbon nanotubes, and porous carbon fibers.

5. A method for preparing a nano-solid hydrogen storage material according to any one of claims 1-4, characterized in that, Includes the following steps: Step S1: Prepare a multi-metal organic framework precursor solution; Step S2: Synthesize multimetal-organic framework nanoparticles using a solvothermal method in the presence of a template agent; Step S3: Chemically composite the multimetal-organic framework nanoparticles with magnesium and nickel sources to obtain the precursor complex; Step S4: Carbonize the precursor composite to obtain a porous carbon-coated multimetal nanocatalyst@magnesium-based composite material. Step S5: Combine the material obtained in step S4 with functionalized carbon sources and metal-organic framework derivatives to construct a three-dimensional network framework; Step S6: Perform high-pressure hydrogenation treatment to obtain nano-solid hydrogen storage material.

6. The method for preparing a nano-solid hydrogen storage material according to claim 5, characterized in that, The multi-metal organic framework precursor solution in step S1 contains at least two metal ions and an organic ligand, wherein the metal ions are selected from Ti. 4+ V 5+ Mn 2+ Fe 3+ Co 2+ Ni 2+ Zr 4+ 、Nb 5+ Mo 6+ At least two of the organic ligands are selected from terephthalic acid, trimesic acid, and 2-methylimidazole; The template agent mentioned in step S2 is selected from one of polymethyl methacrylate, polystyrene, and silica nanospheres, with a particle size of 100-300 nm; the solvothermal reaction temperature is 100-200℃, and the reaction time is 12-48 hours.

7. The method for preparing a nano-solid hydrogen storage material according to claim 5, characterized in that, The chemical compounding in step S3 is either a liquid-phase reduction method or a mechanical ball milling method; the liquid-phase reduction method includes reacting polymetallic organic framework nanoparticles with magnesium salts and nickel salts in the presence of a reducing agent, which is selected from sodium borohydride, lithium aluminum hydride, and hydrazine hydrate; the mechanical ball milling method includes ball milling polymetallic organic framework nanoparticles with magnesium powder and nickel powder under an inert atmosphere, with a ball milling speed of 200-500 rpm and a ball milling time of 5-20 hours.

8. The method for preparing a nano-solid hydrogen storage material according to claim 5, characterized in that, The carbonization process described in step S4 is carried out under an inert or reducing atmosphere, with a carbonization temperature of 500-800℃, a heating rate of 1-10℃ / min, and a holding time of 1-5 hours; the inert atmosphere is one or more of argon and nitrogen, and the reducing atmosphere is a hydrogen-argon mixture or ammonia.

9. The method for preparing a nano-solid hydrogen storage material according to claim 5, characterized in that, The functionalized carbon source in step S5 is selected from one or more of graphene oxide, carbon nanotubes, and porous carbon fibers. The functionalization includes one or more of nitrogen doping, boron doping, and sulfur doping. The metal-organic framework derivative is a porous carbon material obtained by pyrolysis of one or more of ZIF-8, ZIF-67, UiO-66, and MIL-101. The composite method is liquid phase self-assembly or electrostatic spray deposition.

10. The method for preparing a nano-solid hydrogen storage material according to claim 5, characterized in that, The high-pressure hydrogenation process in step S6 involves a hydrogen pressure of 3-10 MPa, a temperature of 200-400°C, and a time of 2-10 hours.

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