Foamed metal composite hydrogen storage material and preparation method thereof

Abstract

The application provides a preparation method of a foamed metal composite hydrogen storage material, and steps of the method comprise the following: mixing vanadium-containing alloy powder, a pore-forming agent and an organic binder, performing heat treatment after die forming to densify the alloy and obtain an inner pressure-bearing framework; depositing a magnesium-titanium nanocomposite layer through a magnetron co-sputtering technique; growing a graphene layer through chemical vapor deposition; immersing the framework with the graphene layer into a solution containing a palladium salt to generate and load palladium nanoparticles in situ on the surface of the graphene to form a surface catalytic layer, thereby obtaining a metal foamed framework; and immersing the metal foamed framework into a solution containing a zirconium salt and an organic ligand to grow a metal organic framework in situ on the surface of the metal foamed framework through a solvothermal reaction, thereby obtaining the foamed metal composite hydrogen storage material. The application improves the mechanical strength, hydrogen storage capacity and kinetic performance of the material, improves the stability of the material in the hydrogen absorption and release cycle, and solves the problems of traditional hydrogen storage materials in mechanical performance, hydrogen storage efficiency, cycle stability and the like.

Description

Technical Field

[0001] This invention relates to the field of foam metal technology, specifically to a foam metal composite hydrogen storage material and its preparation method. Background Technology

[0002] With the continued growth of global energy demand and increasing emphasis on environmental protection, developing clean, efficient, and sustainable energy storage and conversion technologies has become a key task in the scientific research field. Hydrogen energy, as a highly promising clean energy source, is considered an important component of the future energy system because its combustion product is only water, it is pollution-free, and it has high energy density. However, efficient hydrogen storage is one of the key bottlenecks to its widespread application. Traditional hydrogen storage methods, such as high-pressure gaseous hydrogen storage and cryogenic liquid hydrogen storage, each have their own limitations.

[0003] Metal foam composite hydrogen storage materials are advanced materials that combine metal foam structure with hydrogen storage functionality. Metal foam possesses a unique three-dimensional interconnected porous structure, which endows the material with numerous superior properties. On one hand, the porous structure provides a large specific surface area, offering abundant active sites for hydrogen atom adsorption and diffusion, thus improving the material's hydrogen storage capacity. On the other hand, the metal framework itself has high mechanical strength, enabling it to withstand the stress generated by volume changes during hydrogen adsorption and desorption cycles, preventing material pulverization and failure, thereby ensuring the material's cycle stability.

[0004] During hydrogen absorption and desorption cycles, hydrogen storage materials undergo volume expansion and contraction, and these repeated volume changes generate significant stress within the material. Existing foamed metal composite hydrogen storage materials often suffer from insufficient mechanical strength in their metal framework to withstand this stress, leading to phenomena such as pulverization and cracking, severely impacting the material's cycle stability and lifespan. Currently, many foamed metal composite hydrogen storage materials have low hydrogen storage capacities, failing to meet the high energy density requirements of practical applications. Furthermore, their hydrogen absorption and desorption kinetics are poor; the processes require high temperature and pressure conditions, and the reaction rate is slow, significantly increasing the energy consumption and operating costs of the hydrogen storage system. To address these issues, this invention provides a foamed metal composite hydrogen storage material and its preparation method. Summary of the Invention

[0005] The purpose of this invention is to provide a foamed metal composite hydrogen storage material and its preparation method, which improves the material's mechanical strength, hydrogen storage capacity and kinetic performance, and enhances the material's stability in hydrogen absorption and desorption cycles, thus overcoming the shortcomings of traditional hydrogen storage materials in terms of mechanical properties, hydrogen storage efficiency and cycle stability.

[0006] On one hand, the present invention provides a method for preparing a foamed metal composite hydrogen storage material, the steps of which include: S1. Vanadium-containing alloy powder, pore-forming agent and organic binder are mixed and molded to obtain an inner skeleton preform with a three-dimensional interconnected porous structure; S2. The inner skeleton preform is heat-treated to densify the alloy and obtain the inner pressure-bearing skeleton; S3. A magnesium-titanium nanocomposite layer is deposited on the surface of the inner pressure-bearing skeleton using magnetron co-sputtering technology; S4. A graphene layer is grown on the surface of a magnesium-titanium nanocomposite layer by chemical vapor deposition; S5. The skeleton with the graphene layer is immersed in a solution containing palladium salt. The impregnation is assisted by ultrasound and chemical reduction is carried out by a reducing agent. Palladium nanoparticles are generated and loaded in situ on the graphene surface to form a surface catalytic layer, thus obtaining a metal foam skeleton. S6. The metal foam framework is immersed in a solution containing zirconium salt and organic ligand, and a metal-organic framework is grown in situ on its surface by a solvothermal reaction to obtain the foam metal composite hydrogen storage material.

[0007] Further, in step S1, the vanadium-containing alloy powder comprises the following chemical composition by mass percentage: V 84.0-86.0 wt.%, Ti 9.0-10.5 wt.%, Cr 4.5-5.5 wt.%, with the balance being unavoidable impurities, and its average particle size is 15-45 μm; the pore-forming agent is ammonium bicarbonate particles with an average particle size of 150-250 μm; and the amount of the pore-forming agent added is 20%-40% of the weight of the vanadium-containing alloy powder.

[0008] Further, in step S1, the organic binder is a mixture of polyvinyl alcohol aqueous solution and glycerin; wherein the amount of solid polyvinyl alcohol added is 1.5%-3.0% of the weight of the vanadium alloy powder, and the amount of glycerin added is 5%-10% of the weight of solid polyvinyl alcohol; the molding pressure is 200-300 MPa.

[0009] Further, in step S2, the heat treatment includes: first, heating to 180-250℃ at a rate of 1-5℃ / min and holding for 0.5-1.5 hours to allow the organic binder to initially decompose; then heating to 350-450℃ at a rate of 3-8℃ / min and holding for 1-3 hours to allow the pore-forming agent to completely decompose and form an open-cell structure; finally, continuing to heat to 1050-1150℃ and holding for 1-3 hours to complete the solid-state sintering and densification of the alloy.

[0010] Furthermore, in step S3, the magnetron co-sputtering is performed in an ultra-high vacuum environment, using magnesium and titanium targets for co-sputtering, with a substrate temperature of 100-200℃ during deposition and a total deposition thickness of 300-500nm.

[0011] Further, in step S4, the conditions for the chemical vapor deposition growth of the graphene layer are: temperature 900-1000℃, methane to hydrogen volume ratio of 3-5:1, pressure 50-150Pa, and time 20-40 minutes.

[0012] Further, in step S5, the palladium salt-containing solution is an aqueous or alcoholic solution of palladium chloropalladium or palladium nitrate, with a concentration of 3-5 mM; the reducing agent is ascorbic acid, sodium borohydride, or hydrazine hydrate; the reduction reaction is carried out at room temperature to 80°C for 2-4 hours.

[0013] Further, in step S6, the zirconium salt in the solution containing zirconium salt and organic ligand is zirconium tetrachloride with a concentration of 0.08-0.12 mol / L; the organic ligand is 2-aminoterephthalic acid with a concentration of 0.08-0.12 mol / L; and the solvent is N,N-dimethylformamide, containing formic acid as a modifier.

[0014] Further, in step S6, the solvothermal reaction is carried out at 80-90°C for 20-28 hours, and after the reaction, the sample is washed and activated under vacuum at 100-130°C to obtain a metal-organic framework with a thickness of 90-120 nm.

[0015] On the other hand, the present invention also provides a foamed metal composite hydrogen storage material, which is prepared using the aforementioned preparation method.

[0016] The beneficial effects of this invention are as follows: (1) This invention innovatively designs a five-layer gradient system consisting of an inner V-Ti-Cr alloy pressure-bearing framework, a magnesium-titanium hydrogen diffusion layer, a graphene conductive carrier layer, a palladium nanoparticle catalytic layer, and an amino-functionalized MOF protective / adsorption layer. From a synergistic perspective, each layer is not isolated but interconnected and interacts with each other to jointly perform the overall function. Among them, the inner V-Ti-Cr alloy pressure-bearing framework provides mechanical support for the entire material, ensuring that the material can withstand volumetric strain without pulverizing and failing during hydrogen absorption and desorption cycles, thus providing a basic guarantee for the stable existence and function of other functional layers. The magnesium-titanium hydrogen diffusion layer, as a hydrogen diffusion promoting layer and an interface buffer layer, promotes the diffusion of hydrogen atoms into the bulk alloy on the one hand, and buffers the stress between different layers on the other hand, making the bonding between the layers tighter and avoiding problems such as interlayer separation caused by stress concentration, thus ensuring the integrity of the overall structure. The graphene conductive support layer, with its high specific surface area and high conductivity, provides an ideal dispersion substrate for palladium nanoparticles, enabling uniform distribution and increasing the number of catalytic active sites. Its excellent conductivity also facilitates rapid electron transport, promoting the catalytic reaction. The palladium nanoparticle catalytic layer, acting as the reaction initiator for efficient hydrogen storage in the entire material, catalyzes the dissociation of hydrogen molecules, lowering the hydrogen absorption energy barrier and enabling effective hydrogen absorption under mild conditions—a crucial step in the hydrogen storage reaction. The outermost amino-functionalized MOF protective / adsorption layer not only provides additional physical adsorption hydrogen storage capacity but also acts as a protective layer, effectively isolating palladium nanoparticles from the external environment, preventing oxidation, migration, and aggregation, and maintaining long-term cycling stability. Through this ordered gradient design, the various layers achieve complementary functional advantages and synergistic effects, collectively enhancing the material's hydrogen storage performance.

[0017] (2) This invention constructs a catalytic-hydrogen storage synergistic mechanism, with a palladium nanoparticle catalytic layer as the core, and each layer working synergistically around it to improve hydrogen storage efficiency. The palladium nanoparticle catalytic layer catalyzes the dissociation of hydrogen molecules into hydrogen atoms, which is the key initial step in the hydrogen storage reaction. After dissociation, hydrogen atoms need to diffuse rapidly into the hydrogen storage material for storage. At this point, the magnesium-titanium hydrogen diffusion layer plays an important role, providing a rapid channel for hydrogen atom diffusion, promoting the diffusion of hydrogen atoms into the bulk alloy, and enabling hydrogen atoms to smoothly enter the inner V-Ti-Cr alloy pressure-bearing framework for storage. Simultaneously, the high conductivity of the graphene conductive carrier layer ensures rapid electron transport between layers, providing the necessary electronic environment for the catalytic reaction and hydrogen atom diffusion, accelerating the entire hydrogen storage process. The amino-functionalized MOF protection / adsorption layer, while providing additional physical adsorption hydrogen storage capacity, may also have a certain impact on the adsorption and diffusion of hydrogen atoms due to its special structure, further optimizing the hydrogen storage process. Each layer, surrounding the palladium nanoparticle catalytic layer, achieves efficient hydrogen storage through the synergy of the catalytic reaction and the hydrogen storage process.

[0018] (3) This invention has achieved synergistic optimization in structural and compositional design, improving the overall performance of the material in multiple aspects. In terms of structure, a multi-layered gradient structure is adopted, with each layer designed specifically according to its functional requirements. For example, the porous structure of the inner alloy skeleton facilitates hydrogen atom storage and diffusion, while the layered structure of the graphene layer provides high specific surface area and good conductivity. In terms of composition, the inner V-Ti-Cr alloy achieves good mechanical and hydrogen storage performance through a reasonable element ratio. The ratio of magnesium to titanium in the magnesium-titanium nanocomposite layer is optimized to effectively promote hydrogen diffusion and ensure good bonding with adjacent layers. The graphene layer is grown through chemical vapor deposition, ensuring its quality. Palladium nanoparticles are loaded onto the graphene surface using ultrasonic-assisted impregnation and chemical reduction methods, achieving uniform distribution. The amino-functionalized MOF layer achieves specific structure and properties through the selection of specific zirconium salts, organic ligands, and modulators. The synergistic optimization of structure and composition significantly improves the material's mechanical strength, hydrogen storage capacity, kinetic performance, and cycle stability, achieving optimization of the material's overall performance. Detailed Implementation

[0019] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Example 1 This embodiment provides a method for preparing a foamed metal composite hydrogen storage material, the steps of which include: S1. The selected vanadium-containing alloy powder has the following chemical composition: V 85.0 wt.%, Ti 9.8 wt.%, Cr 5.0 wt.%, with the balance being unavoidable impurities; the average particle size of the powder is 30 μm. Weigh 1000g of the above alloy powder and dry mix with 300g of ammonium bicarbonate particles with an average particle size of 200μm for 45 minutes; under stirring at 100rpm, slowly spray a PVA aqueous solution containing 25g of polyvinyl alcohol solid (total 500g) into the mixed powder, and simultaneously add 2.5g of glycerol, and knead until the material is uniformly moist and agglomerated to obtain a mixture; put the mixture into a cylindrical hard alloy mold with an inner diameter of 50mm, press it unidirectionally under a pressure of 250 MPa and hold the pressure for 1.5 minutes to form an inner skeleton preform with a three-dimensional interconnected porous structure; S2. Under an argon atmosphere, the temperature is increased to 200℃ at a rate of 3℃ / min and held for 30 minutes to allow the PVA binder to initially decompose. The temperature is then increased to 400℃ at a rate of 5℃ / min and held for 1 hour. During this stage, ammonium bicarbonate completely decomposes into gas and escapes. At the same time, PVA is completely decomposed. The heating rate must be strictly controlled to prevent rapid gas release from causing cracking of the billet. Subsequently, the temperature is increased to 1100℃ at a rate of 8℃ / min and held for 2 hours. After cooling in the furnace, the billet is removed to obtain the inner pressure-bearing skeleton. S3. Cut the sintered inner pressure-bearing skeleton into samples with a diameter of 28 mm and a thickness of 10 mm, and place them in acetone and anhydrous ethanol for ultrasonic cleaning for 15 minutes each to remove surface contaminants; then dry them in a vacuum oven at 110℃ for 1.5 hours. The cleaned and dried sample was loaded into the sample stage of the magnetron sputtering equipment, and a vacuum of 4 × 10⁻⁶ was drawn. -4 Pa; High-purity argon gas is introduced to the working pressure of 0.8 Pa; Magnesium and titanium targets are co-sputtered, and the sputtering rate ratio of magnesium to titanium is adjusted to 3:1 (atomic ratio). The substrate temperature during deposition is controlled at 150℃, and the total deposition time is 90 minutes. A magnesium-titanium nanocomposite layer with a total thickness of about 400 nm is deposited on the entire surface of the inner pressure-bearing skeleton. S4. The sample with the deposited magnesium-titanium nanocomposite layer was transferred into a chemical vapor deposition (CVD) device; after being evacuated to 5 Pa, argon gas was introduced to atmospheric pressure, and the temperature was increased to 950 °C at 25 °C / min and stabilized for 15 minutes in a mixed atmosphere of pure hydrogen (flow rate 15 sccm) and argon (flow rate 180 sccm); then a reaction gas was introduced, in which the flow rate ratio of methane to hydrogen was 4:1, the reaction chamber pressure was maintained at 100 Pa, and the growth time was 35 minutes, resulting in the growth of a continuous graphene layer on the surface of the magnesium-titanium nanocomposite layer; S5. Immerse the sample with the graphene layer in 100 mL of a 4.0 mM chloropalladium acid / ethanol (volume ratio 1:1) mixed solution and soak for 25 minutes under ultrasonic assistance at 45 kHz and 80 W. Then, slowly add an equal volume of 0.1 M ascorbic acid aqueous solution to the solution and gently stir the reaction in a 70 °C water bath for 3 hours to reduce palladium ions to palladium nanoparticles in situ on the graphene surface. After the reaction is complete, take out the sample, wash it three times with deionized water, and dry it in a vacuum oven at 80 °C to form a catalytically active surface catalytic layer, thus obtaining a metal foam framework. S6. Dissolve 2.33 g of zirconium tetrachloride in 100 mL of N,N-dimethylformamide (DMF) to obtain a 0.1 mol / L solution; dissolve 1.81 g of 2-aminoterephthalic acid in 100 mL of DMF to obtain a 0.1 mol / L solution; mix the two solutions in equal volumes, add 1 mL of formic acid as a modifier, and sonicate to obtain a uniform growth solution; The metal foam framework was immersed in the above growth solution and sealed in a 100 mL stainless steel reactor lined with polytetrafluoroethylene. The reaction was carried out at 85°C for 24 hours. After the reaction, the sample was naturally cooled to room temperature, removed, and washed three times with fresh DMF for 8 hours each time to remove unreacted raw materials. Subsequently, it was activated at 120°C and 10 Pa for 12 hours to grow a UiO-66-NH2 metal-organic framework with a thickness of about 100 nm on the surface and in the pores of the framework, and finally the foam metal composite hydrogen storage material was obtained.

[0021] Example 2 This embodiment provides a method for preparing a foamed metal composite hydrogen storage material, the steps of which include: S1. The selected vanadium-containing alloy powder has the following chemical composition: V 84.0 wt.%, Ti 9.0 wt.%, Cr 4.5 wt.%, with the balance being unavoidable impurities; the average particle size of the powder is 15 μm. Weigh 1000g of the above alloy powder and dry mix with 200g of ammonium bicarbonate particles with an average particle size of 150μm for 45 minutes; under stirring, slowly spray a PVA aqueous solution containing 15g of polyvinyl alcohol solid (total 500g) into the mixed powder, and simultaneously add 0.75g of glycerol, and mix evenly to obtain a mixture; put the mixture into a cylindrical hard alloy mold with an inner diameter of 50 mm, press it unidirectionally under a pressure of 200MPa and hold the pressure for 1.5 minutes to form an inner skeleton preform; S2. Under an argon atmosphere, the temperature is increased to 180°C at a rate of 1°C / min and held for 30 minutes; then increased to 350°C at a rate of 3°C / min and held for 1 hour; then increased to 1050°C at a rate of 8°C / min and held for 1 hour. After cooling in the furnace, the inner pressure-bearing skeleton is obtained. S3. Cut the sintered inner pressure-bearing skeleton into samples with a diameter of 28 mm and a thickness of 10 mm, and place them in acetone and anhydrous ethanol for ultrasonic cleaning for 15 minutes each to remove surface contaminants; then dry them in a vacuum oven at 110℃ for 1.5 hours. The cleaned and dried sample was loaded into the sample stage of the magnetron sputtering equipment, and a vacuum of 4 × 10⁻⁶ was drawn. -4Pa; High-purity argon gas is introduced to the working pressure of 0.8 Pa; Magnesium and titanium targets are co-sputtered, and the sputtering rate ratio of magnesium to titanium is adjusted to 3:1 (atomic ratio). The substrate temperature during deposition is controlled at 100℃, and the total deposition time is 90 minutes. A magnesium-titanium nanocomposite layer with a total thickness of about 300 nm is deposited on the entire surface of the inner pressure-bearing skeleton. S4. The sample with the deposited magnesium-titanium nanocomposite layer was transferred into a chemical vapor deposition (CVD) device; after being evacuated to 5 Pa, argon gas was introduced to atmospheric pressure, and the temperature was increased to 900 °C at 25 °C / min and stabilized for 15 minutes in a mixed atmosphere of pure hydrogen (flow rate 15 sccm) and argon (flow rate 180 sccm); then a reaction gas was introduced, in which the flow rate ratio of methane to hydrogen was 3:1, the reaction chamber pressure was maintained at 50 Pa, and the growth time was 20 minutes, so that a continuous graphene layer was grown on the surface of the magnesium-titanium nanocomposite layer; S5. Immerse the sample with the graphene layer in 100 mL of a 3.0 mM chloropalladium acid / ethanol (volume ratio 1:1) mixed solution and soak for 25 minutes under ultrasonic assistance at 45 kHz and 80 W. Then, slowly add an equal volume of 0.1 M ascorbic acid aqueous solution to the solution and react at room temperature for 3 hours to reduce palladium ions to palladium nanoparticles in situ on the graphene surface. After the reaction is complete, take out the sample, wash it three times with deionized water, and dry it in a vacuum oven at 80 °C to form a catalytically active surface catalytic layer, thus obtaining a metal foam framework. S6. Prepare a DMF mixed solution containing 0.08 mol / L zirconium tetrachloride and 0.08 mol / L 2-aminoterephthalic acid (containing 1 vol% formic acid), and ultrasonically stir to obtain 100 mL of growth solution; immerse the framework in the solution and place it in a reaction vessel, and react at 80 °C for 20 hours; after the reaction, allow it to cool naturally to room temperature, remove the sample, and wash it three times with fresh DMF for 8 hours each time to remove unreacted raw materials; then activate it at 100 °C and 10 Pa for 12 hours to grow a UiO-66-NH2 metal-organic framework with a thickness of about 90 nm on the surface and in the pores of the framework, and finally obtain the foam metal composite hydrogen storage material.

[0022] Example 3 This embodiment provides a method for preparing a foamed metal composite hydrogen storage material, the steps of which include: S1. The selected vanadium-containing alloy powder has the following chemical composition: V 86.0 wt.%, Ti 10.5 wt.%, Cr 5.5 wt.%, with the balance being unavoidable impurities; the average particle size of the powder is 45 μm. Weigh 1000g of the above alloy powder and dry mix with 400g of ammonium bicarbonate particles with an average particle size of 250μm for 45 minutes; under stirring, slowly spray a PVA aqueous solution containing 30g of polyvinyl alcohol solid (total 500g) into the mixed powder, and simultaneously add 3.0g of glycerin, and mix evenly to obtain a mixture; put the mixture into a cylindrical hard alloy mold with an inner diameter of 50mm, press it unidirectionally under a pressure of 300MPa and hold the pressure for 1.5 minutes to form an inner skeleton preform; S2. Under an argon atmosphere, the temperature is increased to 250°C at a rate of 5°C / min and held for 1.5 hours; then the temperature is increased to 450°C at a rate of 8°C / min and held for 3 hours; then the temperature is increased to 1150°C at a rate of 8°C / min and held for 3 hours. After cooling in the furnace, the inner pressure-bearing skeleton is obtained. S3. Cut the sintered inner pressure-bearing skeleton into samples with a diameter of 28 mm and a thickness of 10 mm, and place them in acetone and anhydrous ethanol for ultrasonic cleaning for 15 minutes each to remove surface contaminants; then dry them in a vacuum oven at 110℃ for 1.5 hours. The cleaned and dried sample was loaded into the sample stage of the magnetron sputtering equipment, and a vacuum of 4 × 10⁻⁶ was drawn. -4 Pa; High-purity argon gas is introduced to the working pressure of 0.8 Pa; Magnesium and titanium targets are co-sputtered, and the sputtering rate ratio of magnesium to titanium is adjusted to 3:1 (atomic ratio). The substrate temperature during deposition is controlled at 200℃, and the total deposition time is 90 minutes. A magnesium-titanium nanocomposite layer with a total thickness of about 500 nm is deposited on the entire surface of the inner pressure-bearing skeleton. S4. The sample with the deposited magnesium-titanium nanocomposite layer was transferred into a chemical vapor deposition (CVD) device; after being evacuated to 5 Pa, argon gas was introduced to atmospheric pressure, and the temperature was increased to 1000 °C at 25 °C / min and stabilized for 15 minutes in a mixed atmosphere of pure hydrogen (flow rate 15 sccm) and argon (flow rate 180 sccm); then a reaction gas was introduced, in which the flow rate ratio of methane to hydrogen was 4:1, the reaction chamber pressure was maintained at 150 Pa, and the growth time was 40 minutes, so that a continuous graphene layer was grown on the surface of the magnesium-titanium nanocomposite layer; S5. Immerse the sample with the graphene layer in 100 mL of a 5.0 mM chloropalladium acid / ethanol (volume ratio 1:1) mixed solution and soak for 25 minutes under ultrasonic assistance at 45 kHz and 80 W. Then, slowly add an equal volume of 0.1 M hydrazine hydrate aqueous solution to the solution and gently stir in an 80 °C water bath for 4 hours to reduce palladium ions to palladium nanoparticles in situ on the graphene surface. After the reaction is complete, take out the sample, wash it three times with deionized water, and dry it in a vacuum oven at 80 °C to obtain a metal foam framework. S6. Prepare a DMF mixed solution containing 0.12 mol / L zirconium tetrachloride and 0.12 mol / L 2-aminoterephthalic acid (containing 1 vol% formic acid), and ultrasonically stir to obtain 100 mL of growth solution; immerse the framework in the solution and place it in a reaction vessel, and react at 90 °C for 28 hours; after the reaction, allow it to cool naturally to room temperature, remove the sample, and wash it three times with fresh DMF for 8 hours each time to remove unreacted raw materials; then activate it at 130 °C and 10 Pa for 12 hours to grow a UiO-66-NH2 metal-organic framework with a thickness of about 120 nm in situ on the surface and pores of the framework, and finally obtain the foam metal composite hydrogen storage material.

[0023] Comparative Example 1 Comparative Example 1 skips step S3 (magnetron co-sputtering), and directly performs CVD growth of graphene on the cleaned inner pressure-bearing skeleton (S4), with the rest being the same as in Example 1.

[0024] Comparative Example 2 Comparative Example 2 skips step S4 (CVD growth of graphene), that is, after depositing the Mg-Ti layer (S3), step S5 (loading Pd nanoparticles) is performed directly on the surface of the Mg-Ti layer, and the rest is the same as in Example 1.

[0025] Comparative Example 3 Comparative Example 3 skips step S5 (ultrasound-assisted impregnation and reduction of loaded Pd), that is, after growing the graphene layer (S4), it directly performs step S6 (growing MOF), and the rest is the same as in Example 1.

[0026] Comparative Example 4 Comparative Example 4 skips step S6 (solvent-thermal growth of MOF), that is, stops after obtaining the Pd-loaded graphene / Mg-Ti / foam alloy skeleton in step S5, and the rest is the same as in Example 1.

[0027] Comparative Example 5 In Comparative Example 5, the vanadium-containing alloy powder in step S1 was replaced with pure vanadium powder, and the rest was the same as in Example 1.

[0028] Comparative Example 6 In Comparative Example 6, the pore-forming agent ammonium bicarbonate in step S1 was replaced with an equal mass (300g) of urea particles (average particle size 200μm), and the rest was the same as in Example 1.

[0029] Comparative Example 7 Comparative Example 7 replaced the organic ligand 2-aminoterephthalic acid in step S6 with terephthalic acid, with other conditions remaining unchanged, and was otherwise the same as in Example 1.

[0030] Comparative Example 8 Comparative Example 8, after completing step S4 (growing graphene), first performs step S6 (growing MOF), and then performs step S5 (impregnation and reduction of Pd) on the skeleton with MOF coating. The rest is the same as in Example 1.

[0031] Experimental Example: The performance of the foamed metal composite hydrogen storage materials prepared in Examples 1-3 and Comparative Examples 1-8 was investigated. The prepared foamed metal composite hydrogen storage materials were tested as follows: Mechanical strength testing: Quasi-static compression testing was conducted using a WDW-100 microcomputer-controlled electronic universal testing machine. First, the material was wire-cut and ground into standard cylindrical specimens of Φ10 mm × 10 mm. Then, these specimens were precisely mounted on the compression fixture of the testing machine with a spherical self-centering seat to eliminate eccentric loading. The test was set to displacement control mode, with a constant loading rate of 0.05 mm / min. Load and displacement data were continuously collected until the engineering strain reached 60%. Finally, based on the recorded load-displacement curves, the compressive yield strength of the material (determined using the 0.2% plastic strain offset method) and the average stress in the compression plateau region were calculated. Reversible hydrogen storage capacity: Using the H2PCT-1153 3-channel fully automated hydrogen storage material performance testing system, 0.5g of sample was loaded into the sample tube, the system was evacuated to a high vacuum, and vacuum degassed at 300℃ for 2 hours. Then, high-purity hydrogen gas (3MPa) was introduced to perform several hydrogen absorption and desorption cycles until the performance was stable; the mass hydrogen storage density (wt.%) at 25℃ and 3MPa. Cyclic stability test: The sample was subjected to at least 100 hydrogen absorption and desorption cycles at 60℃, hydrogen absorption pressure of 3MPa and hydrogen release pressure of 0.1MPa in a fully automated hydrogen storage material performance testing system. After every 10 cycles, a complete PCT test was performed, and the decay of hydrogen storage capacity was recorded. After the cycle was completed, the reversible hydrogen storage capacity retention rate was calculated.

[0032] The test results are shown in Table 1 below: Table 1 Based on the aforementioned data, Comparative Example 1 demonstrates that the magnesium-titanium nanocomposite layer is an indispensable hydrogen diffusion promoting layer and interface buffer layer. Its absence leads to poor graphene quality and weak bonding with the substrate, severely hindering the diffusion of hydrogen atoms into the bulk alloy, resulting in a decrease in hydrogen storage capacity of over 60% and a significant deterioration in kinetic performance.

[0033] Comparative Example 2 demonstrates the crucial role of the graphene layer as a support for high specific surface area and high conductivity. Its absence causes Pd nanoparticles to lose their ideal dispersion substrate, resulting in severe aggregation on the Mg-Ti layer, leading to a sharp reduction in the number of catalytic active sites and a simultaneous and significant decrease in hydrogen storage capacity and cycle stability.

[0034] Comparative Example 3 directly demonstrates that the palladium nanoparticle catalytic layer is the reaction initiator for efficient hydrogen storage in the entire material. Without Pd catalysis to dissociate hydrogen molecules, the hydrogen absorption reaction barrier of the material is extremely high, and it is almost impossible to effectively absorb hydrogen under mild conditions (25℃, 3MPa), verifying the core position of the catalytic-hydrogen storage synergistic mechanism.

[0035] Comparative Example 4 demonstrates that the outermost UiO-66-NH2MOF layer has a dual function: firstly, it provides additional physical adsorption hydrogen storage capacity; secondly, it acts as a protective layer, effectively isolating Pd nanoparticles from the external environment and preventing their oxidation, migration, and aggregation, which is crucial for maintaining long-term cycling stability. Its absence leads to a sharp decline in stability.

[0036] Comparative Example 5 demonstrates the absolute advantage of the V-Ti-Cr ternary alloy skeleton of the present invention over pure vanadium in terms of mechanical strength. The yield strength of the pure vanadium skeleton is less than 60% of that of Example 1, and it rapidly pulverizes under volumetric strain during hydrogen absorption and desorption cycles, leading to complete material failure, highlighting the necessity of a high-strength, pressure-bearing skeleton design.

[0037] Comparative Example 6 demonstrates the superiority of using ammonium bicarbonate as a pore-forming agent. Its decomposition temperature matches well with that of the binder, enabling the formation of a uniform, interconnected three-dimensional porous structure. In contrast, urea decomposes at a high temperature and at asynchronous rates, resulting in a poor pore structure that fundamentally affects the uniformity and overall performance of all subsequent coatings.

[0038] Comparative Example 7 demonstrates the superiority of amino-functionalized MOFs. The introduction of amino groups not only modulates the electronic structure of the MOF and enhances its interaction with the inner Pd / graphene layers, but may also provide additional weak chemisorption sites. Using ordinary UiO-66 resulted in a noticeable decrease in the overall performance of the material, especially its hydrogen storage performance at low temperatures and pressures.

[0039] Comparative Example 8 demonstrates the scientific validity of the gradient structural sequence (alloy / Mg-Ti / graphene / Pd / MOF) of this invention. Loading Pd outside the MOF disrupts the optimal hydrogen escape path (Pd→graphene→Mg-Ti→alloy), significantly reducing the catalytic efficiency of Pd and making it more prone to deactivation. This, in turn, confirms that the correct structural sequence is crucial for maximizing the synergistic function of each layer.

[0040] This invention achieves complementary advantages and synergistic effects among the functional units through a gradient design of five layers: an inner V-Ti-Cr alloy pressure-bearing skeleton, a magnesium-titanium hydrogen diffusion layer, a graphene conductive carrier layer, a palladium nanoparticle catalytic layer, and an amino-functionalized MOF protective / adsorption layer.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described in the present invention; those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention; and all technical solutions and improvements that do not depart from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing a foamed metal composite hydrogen storage material, characterized in that the steps include... include: S1. Vanadium-containing alloy powder, pore-forming agent and organic binder are mixed and molded to obtain an inner skeleton preform with a three-dimensional interconnected porous structure; S2. The inner skeleton preform is heat-treated to densify the alloy and obtain the inner pressure-bearing skeleton; S3. A magnesium-titanium nanocomposite layer is deposited on the surface of the inner pressure-bearing skeleton using magnetron co-sputtering technology; S4. A graphene layer is grown on the surface of a magnesium-titanium nanocomposite layer by chemical vapor deposition; S5. The skeleton with the graphene layer is immersed in a solution containing palladium salt. The impregnation is assisted by ultrasound and chemical reduction is carried out by a reducing agent. Palladium nanoparticles are generated and loaded in situ on the graphene surface to form a surface catalytic layer, thus obtaining a metal foam skeleton. S6. The metal foam framework is immersed in a solution containing zirconium salt and organic ligand, and a metal-organic framework is grown in situ on its surface by a solvothermal reaction to obtain the foam metal composite hydrogen storage material.

2. The method for preparing a foamed metal composite hydrogen storage material according to claim 1, characterized in that, In step S1, the vanadium-containing alloy powder comprises the following chemical composition by mass percentage: V 84.0-86.0 wt.%, Ti 9.0-10.5 wt.%, Cr 4.5-5.5 wt.%, with the balance being unavoidable impurities, and its average particle size is 15-45 μm; the pore-forming agent is ammonium bicarbonate particles with an average particle size of 150-250 μm; the amount of the pore-forming agent added is 20%-40% of the weight of the vanadium-containing alloy powder.

3. The method for preparing a foamed metal composite hydrogen storage material according to claim 1, characterized in that, In step S1, the organic binder is a mixture of polyvinyl alcohol aqueous solution and glycerin; wherein the amount of solid polyvinyl alcohol added is 1.5%-3.0% of the weight of the vanadium alloy powder, and the amount of glycerin added is 5%-10% of the weight of solid polyvinyl alcohol; the molding pressure is 200-300 MPa.

4. The method for preparing a foamed metal composite hydrogen storage material according to claim 1, characterized in that, In step S2, the heat treatment includes: under argon protection, first heating to 180-250℃ at a rate of 1-5℃ / min and holding at that temperature for 0.5-1.5 hours, then heating to 350-450℃ at a rate of 3-8℃ / min and holding at that temperature for 1-3 hours, and finally heating to 1050-1150℃ and holding at that temperature for 1-3 hours.

5. The method for preparing a foamed metal composite hydrogen storage material according to claim 1, characterized in that, In step S3, the magnetron co-sputtering is performed in an ultra-high vacuum environment, using magnesium and titanium targets for co-sputtering. The substrate temperature during deposition is 100-200℃, and the total deposition thickness is 300-500nm.

6. The method for preparing a foamed metal composite hydrogen storage material according to claim 1, characterized in that, In step S4, the conditions for the chemical vapor deposition growth of the graphene layer are: temperature 900-1000℃, methane to hydrogen volume ratio of 3-5:1, pressure 50-150Pa, and time 20-40 minutes.

7. The method for preparing a foamed metal composite hydrogen storage material according to claim 1, characterized in that, In step S5, the palladium salt-containing solution is an aqueous or alcoholic solution of palladium chloropalladium or palladium nitrate, with a concentration of 3-5 mM; the reducing agent is ascorbic acid, sodium borohydride, or hydrazine hydrate; the reduction reaction is carried out at room temperature to 80°C for 2-4 hours.

8. The method for preparing a foamed metal composite hydrogen storage material according to claim 1, characterized in that, In step S6, the zirconium salt is zirconium tetrachloride with a concentration of 0.08-0.12 mol / L; the organic ligand is 2-aminoterephthalic acid with a concentration of 0.08-0.12 mol / L; and the solvent is N,N-dimethylformamide, containing formic acid as a modifier.

9. The method for preparing a foamed metal composite hydrogen storage material according to claim 1, characterized in that, In step S6, the solvothermal reaction is carried out at 80-90°C for 20-28 hours. After the reaction, the sample is washed and activated under vacuum at 100-130°C to obtain a metal-organic framework with a thickness of 90-120 nm.

10. A foamed metal composite hydrogen storage material, characterized in that, It is prepared using the preparation method according to any one of claims 1-9.

Images