Magnesium hydride hydrogen storage material based on Fe3O4-coated NiO as well as preparation method and application of magnesium hydride hydrogen storage material

Abstract

The invention provides a magnesium hydride hydrogen storage material based on Fe3O4 (at) NiO as well as a preparation method and application of the magnesium hydride hydrogen storage material. The hydrogen storage material is obtained by compounding Fe3O4 (at) NiO and magnesium hydride, wherein the Fe3O4-coated NiO has a core-shell structure in which a Fe3O4 core is wrapped by a NiO shell layer. In the magnesium hydride hydrogen storage material, under the bivalent characteristic of Fe3O4, the action between Fe3O4 and MgH2, the interaction between NiO and MgH2 and the multi-synergistic effect between Fe and Ni in the core-shell structure of Fe3O4-coated NiO, the magnesium hydride hydrogen storage material based on Fe3O4-coated NiO with excellent hydrogen storage capacity is jointly constructed through electron transfer, active site increase, concerted catalysis and other mechanisms; the hydrogen storage performance of magnesium hydride is remarkably improved, the starting temperature of hydrogen storage is reduced, the hydrogen desorption amount is increased, hydrogen absorption and desorption dynamics are optimized, and technical support is provided for storage of hydrogen energy.

Description

Technical Field

[0001] This invention relates to the field of hydrogen storage materials technology, and more specifically, to a magnesium hydride hydrogen storage material based on Fe3O4@NiO, its preparation method, and its application. Background Technology

[0002] In the pursuit of clean energy solutions, solid-state hydrogen storage technology has attracted widespread attention due to its safety and high hydrogen storage density. Magnesium hydride (MgH2), with its excellent hydrogen storage capacity—up to 7.6 wt% mass hydrogen storage density and 110 kg / m³ volumetric hydrogen storage density—along with its low cost and abundant resources, is considered one of the most promising materials in the field of solid-state hydrogen storage. However, the inherently slow kinetics and high thermodynamic stability threshold of MgH2 severely limit its efficiency and scalability in practical applications. Specifically, the slow dehydrogenation (release) and absorption processes of MgH2 require high-temperature activation, which not only increases energy consumption but also restricts the rapid release and storage of hydrogen, significantly reducing its applicability in dynamic hydrogen storage systems.

[0003] In recent years, the introduction of transition metal-based catalysts has provided new avenues for improving the kinetic and thermodynamic properties of MgH2. For example, existing technologies have successfully synthesized Ni / MnO nanocomposites by hydrogenating two-dimensional layered nickel-manganese double hydroxides. The addition of this catalyst significantly reduced the initial dehydrogenation temperature of the BM-MgH2-Ni / MnO composite to 175.6℃, a decrease of 84℃ compared to the starting temperature of pure MgH2. Furthermore, at 250℃, the dehydrogenation amount reached 6.2wt% within 60 minutes, while at a low temperature of 150℃, 5.5wt% hydrogen could be absorbed in just 10 minutes. In existing technologies, a novel hydrangea-shaped NiO@NiMoO4 composite catalyst, combined with magnesium hydride, reduced the initial dehydrogenation temperature of MgH2 + 10wt% NiO@NiMoO4 to 190℃, a decrease of 170℃ compared to pure MgH2, and enabled hydrogen absorption to begin at an extremely low temperature of 40℃. Although the above-mentioned hydrogen storage materials have acceptable effects, they still have problems such as poor thermodynamic stability, obvious agglomeration during hydrogen absorption and desorption, and low hydrogen storage capacity.

[0004] In summary, while some progress has been made in catalytic materials for improving the hydrogen storage performance of magnesium hydride, significant technological gaps and challenges remain in reducing the initial dehydrogenation temperature, increasing the hydrogen storage rate, and enhancing the cycling stability of hydrogen storage materials. Therefore, developing a highly efficient and stable hydrogen storage material to further improve its hydrogen storage performance, enhance its hydrogen absorption and desorption rates at low temperatures and its stability during multiple cycles, and further reduce its preparation cost has become crucial for promoting the large-scale application and commercialization of hydrogen energy. Summary of the Invention

[0005] The main objective of this invention is to provide a magnesium hydride hydrogen storage material based on Fe3O4@NiO, its preparation method, and its application, in order to solve the problems of poor hydrogen storage performance and cycle stability of existing hydrogen storage materials, as well as the complex preparation process and high cost of hydrogen storage materials. The aim is to further improve the hydrogen storage performance of hydrogen storage materials, increase the hydrogen absorption and desorption rate of hydrogen storage materials at low temperatures and the stability of hydrogen storage materials in multiple cycles, and further reduce the preparation cost of hydrogen storage materials.

[0006] This application provides a magnesium hydride hydrogen storage material based on Fe3O4@NiO, which is obtained by combining Fe3O4@NiO and magnesium hydride; wherein, Fe3O4@NiO has a core-shell structure in which a NiO shell surrounds a Fe3O4 core.

[0007] Furthermore, the weight content of Fe3O4@NiO in the hydrogen storage material is 2.5~12.5%; preferably, the weight content of Fe3O4@NiO in the hydrogen storage material is 5~12.5%.

[0008] Further, in Fe3O4@NiO, the molar ratio of Fe to Ni is 1:(0.79~1.33); preferably, the molar ratio of Fe to Ni in Fe3O4@NiO is 1:(0.9~1.2); preferably, the particle size of Fe3O4@NiO is 100~200nm; preferably, the hydrogen storage material is obtained by ball milling Fe3O4@NiO and magnesium hydride; preferably, the particle size of the magnesium hydride hydrogen storage material based on Fe3O4@NiO is 200~300nm.

[0009] According to another aspect of the present invention, a method for preparing the above-mentioned Fe3O4@NiO-based magnesium hydride hydrogen storage material is also provided. The method for preparing the Fe3O4@NiO-based magnesium hydride hydrogen storage material includes the following steps: dissolving a soluble iron salt in a first solvent, adding a stabilizer thereto, and heating to carry out a first reaction; the resulting first reaction slurry is subjected to a first separation and a first drying to obtain Fe3O4 nanoparticles; dispersing the Fe3O4 nanoparticles in a second solvent, adding a soluble nickel salt thereto, and heating to carry out a second reaction; the resulting second reaction slurry is subjected to a second separation and a second drying to obtain a Fe3O4@NiO precursor; calcining the Fe3O4@NiO precursor to obtain Fe3O4@NiO material; and mixing and ball milling the Fe3O4@NiO material with magnesium hydride to obtain the Fe3O4@NiO-based magnesium hydride hydrogen storage material.

[0010] Furthermore, the temperature of the first reaction is 170~220℃ and the time is 8~12h; preferably, the temperature of the second reaction is 140~280℃ and the time is 4~8h.

[0011] Further, the weight ratio of soluble iron salt to stabilizer is (1~2):(5~6); preferably, the stabilizer is an organic acid sodium salt, more preferably sodium acetate and / or sodium citrate; preferably, sodium acetate and sodium citrate are combined as stabilizers; more preferably, the weight ratio of sodium acetate and sodium citrate is (4~5):1.

[0012] Further, the molar ratio of Fe element in Fe3O4 nanoparticles to Ni element in soluble nickel salt is 1:(0.79~1.33); preferably, the concentration of soluble iron salt in the first solvent is 0.084~0.085 mol / L; preferably, the concentration of soluble nickel salt in the second solvent is 0.09~0.11 mol / L; preferably, the first solvent is an alcohol solvent, more preferably ethylene glycol; preferably, the second solvent is an alcohol solvent, more preferably ethylene glycol.

[0013] Furthermore, the calcination is carried out under a protective atmosphere; preferably, the protective atmosphere is argon; preferably, the calcination temperature is 320~380℃ and the time is 1~4h.

[0014] Further, the weight ratio of Fe3O4@NiO material to magnesium hydride is (5~12.5):(95~87.5); preferably, the ball milling is carried out in a hydrogen atmosphere; preferably, during the ball milling process, the ball-to-material weight ratio is (30~50):1; the ball milling speed is 300~600 rpm; the ball milling time is 10~20 h; preferably, the particle size of the magnesium hydride hydrogen storage material based on Fe3O4@NiO is 200~300 nm.

[0015] According to a third aspect of the present invention, an application of the above-mentioned Fe3O4@NiO-based magnesium hydride hydrogen storage material is also provided, wherein the Fe3O4@NiO-based magnesium hydride hydrogen storage material is used in the field of hydrogen storage.

[0016] This application provides a magnesium hydride hydrogen storage material based on Fe3O4@NiO, which is obtained by compositing Fe3O4@NiO and magnesium hydride. The Fe3O4@NiO material has a core-shell structure with a NiO shell encapsulating a Fe3O4 core. In this magnesium hydride hydrogen storage material, through the dual-valence characteristics of Fe3O4, the interaction between Fe3O4 and MgH2, the interaction between NiO and MgH2, and the multiple synergistic effects between Fe and Ni in the core-shell structure of Fe3O4@NiO, a magnesium hydride hydrogen storage material based on Fe3O4@NiO with excellent hydrogen storage capacity is constructed through mechanisms such as electron transfer, increased active sites, and synergistic catalysis. This significantly improves the hydrogen storage performance of magnesium hydride, lowers the start-up temperature of hydrogen storage, increases the hydrogen release rate, optimizes the hydrogen absorption and desorption kinetics, and constructs a highly efficient and stable hydrogen storage system, promoting the development of solid-state hydrogen storage technology in the new energy field. Attached Figure Description

[0017] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0018] Figure 1 The X-ray diffraction patterns of Fe3O4 nanoparticles and Fe3O4@NiO prepared according to Example 1 of the present invention are shown.

[0019] Figure 2 SEM images of Fe3O4 nanoparticles prepared according to Example 1 of the present invention are shown.

[0020] Figure 3 The SEM image of Fe3O4@NiO prepared according to Example 1 of the present invention is shown;

[0021] Figure 4 The TEM image of Fe3O4@NiO prepared according to Example 1 of the present invention is shown;

[0022] Figure 5 The temperature-programmed hydrogen release diagrams of the hydrogen storage materials prepared according to Examples 1, 4, 5, 6, 7 and Comparative Example 1 are shown.

[0023] Figure 6 The temperature-programmed hydrogen release diagrams of the hydrogen storage materials prepared according to Example 1 and Comparative Example 2 of the present invention are shown.

[0024] Figure 7 Isothermal hydrogen release diagrams of hydrogen storage materials prepared according to Example 1 and Comparative Example 1 of the present invention are shown at different temperatures.

[0025] Figure 8 The isothermal hydrogen absorption diagrams of the magnesium hydride hydrogen storage material based on Fe3O4@NiO prepared according to Example 1 of the present invention are shown at different temperatures.

[0026] Figure 9 The isothermal desorption / adsorption cycle curve of the magnesium hydride hydrogen storage material based on Fe3O4@NiO prepared according to Example 1 of the present invention is shown. Detailed Implementation

[0027] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0028] As described in the background section, while some progress has been made in catalytic materials for improving the hydrogen storage performance of magnesium hydride, significant technological gaps and challenges remain in reducing the initial dehydrogenation temperature, increasing the hydrogen storage rate, and enhancing the cycling stability of hydrogen storage materials. Developing a highly efficient and stable hydrogen storage material to further improve its hydrogen storage performance, enhance its hydrogen absorption and desorption rates at low temperatures and its stability during multiple cycles, and further reduce its preparation cost has become an urgent problem to be solved.

[0029] To address the aforementioned issues, this application provides a magnesium hydride hydrogen storage material based on Fe3O4@NiO, which is a composite of Fe3O4@NiO and magnesium hydride. The Fe3O4@NiO material possesses a core-shell structure with a NiO shell encapsulating a Fe3O4 core. This application improves the hydrogen storage performance of magnesium hydride (MgH2) by introducing Fe3O4@NiO with this core-shell structure as a catalyst. In this Fe3O4@NiO material, Fe3O4 acts as the core, while NiO forms the encapsulation layer. This unique core-shell structure design has a significant and beneficial impact on the performance of the hydrogen storage material. Using a hydrogen storage material with the above composition and structure in the field of hydrogen storage technology can not only effectively reduce the dehydrogenation temperature of the hydrogen storage material, but also effectively improve its kinetic performance in the dehydrogenation and hydrogen absorption processes, as well as its hydrogen storage capacity, and further enhance its cycle stability. The reasons for these effects may include the following aspects:

[0030] Firstly, Fe3O4 in hydrogen storage materials is a magnetic oxide possessing both Fe(II) and Fe(III) valence states. On one hand, the presence of dual-valence Fe promotes electron transfer within the hydrogen storage material: the d-electron energy level of Fe varies between Fe(II) and Fe(III), providing the driving force for electron transfer between Fe3O4 and MgH2. This allows the electronic state of Fe ions in Fe3O4 to form effective electronic interactions with the Mg−H bonds in MgH2, promoting electron redistribution between Mg and H, reducing the bond energy of the Mg−H bonds, and facilitating hydrogen dissociation and recombination. This, in turn, lowers the start-up temperature of the hydrogen storage material during hydrogen absorption and desorption, and increases the hydrogen release rate. On the other hand, when Fe3O4 comes into contact with MgH2, due to the strong reducing properties of MgH2, it recombines with Fe3O4, causing some of the Fe(II) and Fe(III) ions in Fe3O4 to be reduced to zero-valent Fe. Zero-valent Fe acts as an active site, further enhancing the dissociation, diffusion, and transfer of hydrogen molecules during subsequent hydrogen storage. Furthermore, the presence of zero-valent Fe active sites effectively prevents Mg grain coarsening, promoting MgH2 dehydrogenation and Mg hydrogen absorption. Simultaneously, the multivalent environment of Fe ions further ensures the continuity and diversity of electron transfer, facilitating the initiation of the dehydrogenation reaction of MgH2 at lower temperatures. In summary, the multivalent characteristics of Fe provide diverse pathways for hydrogenation reactions. This diversity helps optimize the reaction pathways of MgH2 during hydrogen absorption and desorption, thereby reducing energy barriers in the reaction and making the hydrogen absorption and release process smoother.

[0031] Secondly, in the process of hydrogen absorption and desorption, the NiO in the NiO shell encapsulating the Fe3O4 core of the magnesium hydride hydrogen storage material provided in this application reacts chemically with MgH2 to form Mg2NiH4. After dehydrogenation, Mg2Ni is generated. The phase transition between Mg2Ni and Mg2NiH4 during the absorption and dehydrogenation process acts as a "hydrogen pump," thereby providing more transport channels for the rapid storage and release of hydrogen. In addition, the Ni-H bond interaction in Mg2NiH4 is significantly stronger than the Mg-H bond, which facilitates the diffusion of hydrogen atoms on the surface of MgH2 particles. This, in turn, helps to better reduce the potential barrier for hydrogen atom bonding on the particle surface, thereby improving the absorption and desorption kinetics of hydrogen.

[0032] Thirdly, the core-shell structure of Fe3O4@NiO creates an optimized catalytic environment through the synergistic effect of Fe and Ni. This environment simultaneously accelerates the hydrogenation and dehydrogenation processes of MgH2, lowers the activation energy, and allows hydrogen absorption and release to occur at lower temperatures, thus improving the material's hydrogen storage capacity and cycle stability. Furthermore, the spatial isolation provided by the NiO shell prevents the aggregation of Fe3O4 particles, maintaining the high dispersibility of Fe3O4@NiO and increasing the effective contact area between Fe3O4@NiO and MgH2. Simultaneously, the Mg2Ni and Mg2NiH4 formed by the chemical reaction between NiO and MgH2 provide new pathways for hydrogen molecule diffusion, shortening the diffusion distance of hydrogen molecules in MgH2 and significantly improving hydrogen storage efficiency.

[0033] In summary, the hydrogen storage material provided in this application is a composite of Fe3O4@NiO and magnesium hydride; wherein Fe3O4@NiO has a core-shell structure with a NiO shell encapsulating a Fe3O4 core. In the aforementioned magnesium hydride hydrogen storage material, through the dual-valence characteristics of Fe3O4, the interaction between Fe3O4 and MgH2, the interaction between NiO and MgH2, and the multiple synergistic effects between Fe and Ni in the core-shell structure of Fe3O4@NiO, a magnesium hydride hydrogen storage material based on Fe3O4@NiO with excellent hydrogen storage capacity is jointly constructed through mechanisms such as electron transfer, increased active sites, and synergistic catalysis. This significantly improves the hydrogen storage performance of magnesium hydride, reduces the start-up temperature of hydrogen storage, increases the hydrogen release capacity, optimizes the hydrogen absorption and desorption kinetics, and constructs an efficient and stable hydrogen storage system, promoting the development of solid-state hydrogen storage technology in the new energy field.

[0034] In a preferred embodiment, the weight content of Fe3O4@NiO in the hydrogen storage material is 2.5~12.5%. As described above, in the Fe3O4@NiO-based magnesium hydride hydrogen storage material provided in this application, the dual-valence state characteristics of Fe3O4, the interaction between Fe3O4 and MgH2, the interaction between NiO and MgH2, and the synergistic effect between Fe and Ni in the core-shell structure of Fe3O4@NiO, through mechanisms such as electron transfer, increased active sites, and synergistic catalysis, significantly improve the performance of magnesium hydride in the field of hydrogen storage, reduce the start-up temperature, increase the hydrogen release capacity, and optimize the hydrogen absorption and desorption kinetics. Controlling the weight content of Fe3O4@NiO in the hydrogen storage material within the above range can better exert the above effects, thereby giving the hydrogen storage material better hydrogen storage performance. Preferably, the weight content of Fe3O4@NiO in the hydrogen storage material is 5~12.5%; controlling the weight content of Fe3O4@NiO in the hydrogen storage material within the above range further enhances the above effects and improves the kinetic performance of hydrogen storage and release. More preferably, the weight content of Fe3O4@NiO in the hydrogen storage material is 7.5~12.5%. By controlling the weight content of Fe3O4@NiO in the hydrogen storage material within the above-mentioned preferred range, the overall performance of the hydrogen storage material can be further improved.

[0035] In a preferred embodiment, the molar ratio of Fe to Ni in Fe3O4@NiO is 1:(0.79~1.33). In the core-shell structure of Fe3O4@NiO, the synergistic effect of Fe and Ni creates a catalytic environment that accelerates the hydrogenation and dehydrogenation processes of MgH2, improving the material's hydrogen storage capacity and cycle stability. The Mg2Ni and Mg2NiH4 formed by the chemical reaction between NiO and MgH2 shorten the diffusion distance of hydrogen molecules in MgH2, significantly increasing the reaction rate and hydrogen storage efficiency. Controlling the molar ratio of Fe to Ni in Fe3O4@NiO within the above range allows for better utilization of these effects, thereby further improving the overall performance of the hydrogen storage material. Preferably, the molar ratio of Fe to Ni in Fe3O4@NiO is 1:(0.9~1.2). Controlling the molar ratio of Fe to Ni in Fe3O4@NiO within the above range further enhances these effects. Preferably, the particle size of Fe3O4@NiO is 100~200 nm. Controlling the particle size of Fe3O4@NiO within the aforementioned range when combining Fe3O4@NiO and magnesium hydride improves the performance of the resulting Fe3O4@NiO-based magnesium hydride hydrogen storage material. Preferably, the hydrogen storage material is obtained by ball milling Fe3O4@NiO and magnesium hydride; preferably, the particle size of the Fe3O4@NiO-based magnesium hydride hydrogen storage material is 200-300 nm. Using ball milling to thoroughly mix Fe3O4@NiO and magnesium hydride is not only simple and easy to implement, but also better leverages the synergistic effect of Fe3O4@NiO and magnesium hydride in the hydrogen storage material, thereby improving its performance. Controlling the particle size of the hydrogen storage material within the aforementioned range further enhances its performance.

[0036] According to another aspect of the present invention, a method for preparing the above-mentioned magnesium hydride hydrogen storage material based on Fe3O4@NiO is also provided. The preparation method includes the following steps: dissolving a soluble iron salt in a first solvent, adding a stabilizer thereto, and heating to carry out a first reaction; the resulting first reaction slurry is subjected to a first separation and a first drying to obtain Fe3O4 nanoparticles; dispersing the Fe3O4 nanoparticles in a second solvent, adding a soluble nickel salt thereto, and heating to carry out a second reaction; the resulting second reaction slurry is subjected to a second separation and a second drying to obtain a Fe3O4@NiO precursor; calcining the Fe3O4@NiO precursor to obtain Fe3O4@NiO material; and mixing and ball milling the Fe3O4@NiO material with magnesium hydride to obtain the magnesium hydride hydrogen storage material based on Fe3O4@NiO. In the above preparation method, Fe3O4 nanoparticles are first synthesized using a thermal reaction method. Then, the Fe3O4 nanoparticles are further thermally reacted with a soluble nickel salt to generate a Fe3O4@NiO precursor, namely Fe3O4@Ni(OH)2. The Fe3O4@NiO precursor is then further calcined to obtain Fe3O4@NiO material. Finally, the Fe3O4@NiO material is mixed with magnesium hydride and ball-milled to obtain a magnesium hydride hydrogen storage material based on Fe3O4@NiO.

[0037] The above preparation method employs common chemical treatments such as thermal reaction and calcination, avoiding the use of high-energy-consuming conditions such as high temperature and high pressure, thus reducing energy consumption. Simultaneously, the subsequent calcination process is carried out at a relatively low temperature, further reducing the overall energy consumption of the preparation process. The entire process is easy to control and operate, requiring no complex equipment or extreme conditions, which significantly reduces preparation costs and improves production efficiency and repeatability.

[0038] In a preferred embodiment, the temperature of the first reaction is 170-220°C, and the time is 8-12 hours; preferably, the temperature of the second reaction is 140-280°C, and the time is 4-8 hours. The first reaction process is to form Fe3O4 nanoparticles from soluble iron salts; the second reaction process is to form Fe3O4@NiO precursor (Fe3O4@Ni(OH)2) from soluble nickel salts and Fe3O4 nanoparticles. Controlling the temperature and time of the first and second reactions within the above ranges allows the reactions to proceed more fully.

[0039] In a preferred embodiment, the weight ratio of the soluble iron salt to the stabilizer is (1~2):(5~6). The addition of the stabilizer can improve the particle size and uniformity of the generated Fe3O4 nanoparticles, thereby improving the performance of the generated Fe3O4@NiO-based magnesium hydride hydrogen storage material. Controlling the weight ratio of the soluble iron salt to the stabilizer within the above range can control the particle size of the formed Fe3O4 nanoparticles to be smaller and more uniform. The stabilizer is an organic acid sodium salt, more preferably sodium acetate and / or sodium citrate; preferably, sodium acetate and sodium citrate are combined as stabilizers; more preferably, the weight ratio of sodium acetate and sodium citrate is (4~5):1. Using the above two stabilizers in combination and controlling their weight ratio within the above range can exert the synergistic effect of the two stabilizers, thereby further improving the hydrogen storage performance of the prepared hydrogen storage material.

[0040] In a preferred embodiment, the molar ratio of Fe in the Fe3O4 nanoparticles to Ni in the soluble nickel salt is 1:(0.79~1.33). Controlling the molar ratio of Fe in the Fe3O4 nanoparticles to Ni in the soluble nickel salt within the above range allows the formed Fe3O4@NiO material to better exert the synergistic effect of nickel oxide and Fe3O4, thereby further improving the hydrogen storage performance of the prepared hydrogen storage material. Preferably, the concentration of the soluble iron salt in the first solvent is 0.084~0.085 mol / L; preferably, the concentration of the soluble nickel salt in the second solvent is 0.09~0.11 mol / L; preferably, the first solvent is an alcohol solvent, more preferably ethylene glycol; preferably, the second solvent is an alcohol solvent, more preferably ethylene glycol. By selecting the above solvents as the first and second solvents and controlling the parameters in the hydrogen storage material preparation process within the above ranges, the performance of the prepared hydrogen storage material is better.

[0041] In a preferred embodiment, calcination is carried out under a protective gas atmosphere; preferably, the protective gas is argon; preferably, the calcination temperature is 320~380℃, and the time is 1~4h. Controlling the parameters during the calcination process within the above range can improve the shell structure of the Fe3O4@NiO material, thereby further improving the performance of the prepared hydrogen storage material.

[0042] In a preferred embodiment, the weight ratio of Fe3O4@NiO material to magnesium hydride is (5~12.5):(87.5~95). Controlling the weight ratio of Fe3O4@NiO material to magnesium hydride within this range during the preparation of the hydrogen storage material results in better start-up temperature, hydrogen absorption / desorption kinetics, hydrogen storage efficiency, and stability of the prepared hydrogen storage material. Preferably, ball milling is performed under a hydrogen atmosphere; preferably, the ball-to-material weight ratio during ball milling is (30~50):1; the ball milling speed is 300~600 rpm; the ball milling time is 10~20 h; preferably, the particle size of the Fe3O4@NiO-based magnesium hydride hydrogen storage material is 200~300 nm. Controlling the ball milling parameters and the particle size of the prepared Fe3O4@NiO-based magnesium hydride hydrogen storage material within the above ranges further improves the performance of the hydrogen storage material.

[0043] According to a third aspect of the present invention, an application of the above-mentioned Fe3O4@NiO-based magnesium hydride hydrogen storage material is also provided, wherein the Fe3O4@NiO-based magnesium hydride hydrogen storage material is used in the field of hydrogen storage.

[0044] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0045] Example 1

[0046] 2.3 g of ferric chloride hexahydrate was dissolved in 100 mL of ethylene glycol. Then, 6 g of sodium acetate and 1.3 g of sodium citrate were added to the mixture and stirred until homogeneous. The mixture was then heated at 200 °C for 10 h to obtain a slurry containing solids. The slurry was centrifuged, washed, and vacuum dried to obtain Fe3O4 nanoparticles. The SEM image of the prepared Fe3O4 nanoparticles is shown below. Figure 2 As shown, by Figure 2 It can be seen that the Fe3O4 nanoparticles obtained above have a small spherical morphology and uniform particle size, with a particle size range of 80~250nm.

[0047] 0.3 g of the Fe3O4 nanoparticles obtained above were dispersed in 60 mL of ethanol, and then 100 mL of ethylene glycol was added and sonicated for 1 h. Then, 4 mmol of nickel nitrate hexahydrate was added and sonicated for 1 h. The mixture was heated at 160 °C for 6 h to obtain a slurry containing solids. This slurry was centrifuged, washed, and vacuum dried to obtain Fe3O4@Ni(OH)2 material. The Fe3O4@Ni(OH)2 material was then placed in a tube furnace and calcined at 350 °C for 2 h under an argon atmosphere to obtain Fe3O4@NiO material. The Fe3O4@NiO material prepared above was tested, and the results are shown in the figure. Figure 1 , Figure 3 and Figure 4.in, Figure 1 The image shows the X-ray diffraction pattern of Fe3O4@NiO. As can be seen from the image, Fe3O4 and NiO diffraction peaks coexist in the Fe3O4@NiO material. Figure 3 Here is a SEM image of Fe3O4@NiO. Figure 4 The TEM image is of Fe3O4@NiO. Figure 3 and Figure 4 It can be seen that Fe3O4@NiO has a core-shell structure in which the Fe3O4 core is wrapped by a NiO shell.

[0048] By ball milling Fe3O4@NiO material and magnesium hydride material at a ball-to-material weight ratio of 40:1 and a ball milling speed of 450 r / min for 15 h, a magnesium hydride hydrogen storage material based on Fe3O4@NiO can be obtained. The weight content of Fe3O4@NiO in this hydrogen storage material is 7.5%.

[0049] The hydrogen storage materials were subjected to a programmed temperature rise hydrogen release test, and the results are shown in the figure. Figure 5 .Depend on Figure 5 It can be seen that the initial hydrogen release temperature of the above-mentioned hydrogen storage material is 209℃, and the final hydrogen release amount is 6.86wt% when the target hydrogen release temperature is 400℃.

[0050] Example 2

[0051] 2.3 g of ferric chloride hexahydrate was dissolved in 100 mL of ethylene glycol. Then, 4.6 g of sodium acetate and 1.1 g of sodium citrate were added to the mixture and stirred until homogeneous. The mixture was then heated at 170 °C for 12 h to obtain a slurry containing solids. The slurry was centrifuged, washed, and vacuum dried to obtain Fe3O4 nanoparticles. The SEM image of the prepared Fe3O4 nanoparticles is shown below. Figure 2 As shown, by Figure 2 It can be seen that the Fe3O4 nanoparticles obtained above have a small spherical morphology and uniform particle size, with a particle size range of 80~250nm.

[0052] 0.3g of the Fe3O4 nanoparticles obtained above were dispersed in 60mL of ethanol, and then 100mL of ethylene glycol was added and sonicated for 1h. Then 4mmol of nickel nitrate hexahydrate was added and sonicated for 1h. The mixture was heated at 140℃ for 8h to obtain a slurry containing solids. The slurry was centrifuged, washed and vacuum dried to obtain Fe3O4@Ni(OH)2 material. The Fe3O4@Ni(OH)2 material was placed in a tube furnace and calcined at 320℃ for 4h under an argon atmosphere to obtain Fe3O4@NiO material.

[0053] By ball milling Fe3O4@NiO material and magnesium hydride material at a ball-to-material weight ratio of 50:1 and a ball milling speed of 300 r / min for 20 h, a magnesium hydride hydrogen storage material based on Fe3O4@NiO can be obtained. The weight content of Fe3O4@NiO in this hydrogen storage material is 7.5%.

[0054] Example 3

[0055] 2.3 g of ferric chloride hexahydrate was dissolved in 100 mL of ethylene glycol. Then, 11 g of sodium acetate and 2.8 g of sodium citrate were added to the mixture and stirred until homogeneous. The mixture was then heated at 220 °C for 8 h to obtain a slurry containing solids. The slurry was centrifuged, washed, and vacuum dried to obtain Fe3O4 nanoparticles. The SEM image of the prepared Fe3O4 nanoparticles is shown below. Figure 2 As shown, by Figure 2 It can be seen that the Fe3O4 nanoparticles obtained above have a small spherical morphology and uniform particle size, with a particle size range of 80~250nm.

[0056] 0.3g of the Fe3O4 nanoparticles obtained above were dispersed in 60mL of ethanol, and then 100mL of ethylene glycol was added and sonicated for 1h. Then 4mmol of nickel nitrate hexahydrate was added and sonicated for 1h. The mixture was heated at 280℃ for 4h to obtain a slurry containing solids. The slurry was centrifuged, washed and vacuum dried to obtain Fe3O4@Ni(OH)2 material. The Fe3O4@Ni(OH)2 material was placed in a tube furnace and calcined at 380℃ for 1h under an argon atmosphere to obtain Fe3O4@NiO material.

[0057] By ball milling Fe3O4@NiO material and magnesium hydride material at a ball-to-material weight ratio of 30:1 and a ball milling speed of 600 r / min for 10 h, a magnesium hydride hydrogen storage material based on Fe3O4@NiO can be obtained. The weight content of Fe3O4@NiO in this hydrogen storage material is 7.5%.

[0058] Example 4

[0059] The difference between Example 4 and Example 1 is that the weight content of Fe3O4@NiO in the prepared hydrogen storage material is 2.5%.

[0060] The hydrogen storage materials were subjected to a programmed temperature rise hydrogen release test, and the results are shown in the figure. Figure 5 .Depend on Figure 5 It can be seen that the initial hydrogen release temperature of the above-mentioned hydrogen storage material is 219℃, and the final hydrogen release amount is 7.19wt% when the target hydrogen release temperature is 400℃.

[0061] Example 5

[0062] The difference between Example 5 and Example 1 is that the weight content of Fe3O4@NiO in the prepared hydrogen storage material is 5%.

[0063] The hydrogen storage materials were subjected to a programmed temperature rise hydrogen release test, and the results are shown in the figure. Figure 5 .Depend on Figure 5 It can be seen that the initial hydrogen release temperature of the above-mentioned hydrogen storage material is 216.4℃, and the final hydrogen release amount is 7.03wt% when the target hydrogen release temperature is 400℃.

[0064] Example 6

[0065] The difference between Example 6 and Example 1 is that the weight content of Fe3O4@NiO in the prepared hydrogen storage material is 10%.

[0066] The hydrogen storage materials were subjected to a programmed temperature rise hydrogen release test, and the results are shown in the figure. Figure 5 .Depend on Figure 5 It can be seen that the initial hydrogen release temperature of the above-mentioned hydrogen storage material is 206.7℃, and the final hydrogen release amount is 6.61wt% when the target hydrogen release temperature is 400℃.

[0067] Example 7

[0068] The difference between Example 7 and Example 1 is that the weight content of Fe3O4@NiO in the prepared hydrogen storage material is 12.5%.

[0069] The hydrogen storage materials were subjected to a programmed temperature rise hydrogen release test, and the results are shown in the figure. Figure 5 .Depend on Figure 5 It can be seen that the initial hydrogen release temperature of the above-mentioned hydrogen storage material is 205.2℃, and the final hydrogen release amount is 6.52wt% when the target hydrogen release temperature is 400℃.

[0070] Example 8

[0071] The difference between Example 8 and Example 1 is that in the Fe3O4@NiO magnesium hydride hydrogen storage material, the molar ratio of Fe to Ni in Fe3O4@NiO is 1:0.79.

[0072] Example 9

[0073] The difference between Example 9 and Example 1 is that in the Fe3O4@NiO magnesium hydride hydrogen storage material, the molar ratio of Fe to Ni in Fe3O4@NiO is 1:1.33.

[0074] Example 10

[0075] The difference between Example 10 and Example 1 is that in the Fe3O4@NiO magnesium hydride hydrogen storage material, the molar ratio of Fe to Ni in Fe3O4@NiO is 1:1.2.

[0076] Example 11

[0077] The difference between Example 11 and Example 1 is that the weight content of Fe3O4@NiO in the prepared hydrogen storage material is 15%.

[0078] Example 12

[0079] The difference between Example 12 and Example 1 is that the weight content of Fe3O4@NiO in the prepared hydrogen storage material is 1.5%.

[0080] Comparative Example 1

[0081] In Comparative Example 1, only magnesium hydride was used for the programmed temperature rise hydrogen release test; the results are shown in [Figure Number]. Figure 5 .

[0082] Depend on Figure 5 It can be seen that the initial hydrogen release temperature of the above-mentioned hydrogen storage material is 324.2℃, and the final hydrogen release amount is 7.427wt% when the target hydrogen release temperature is 400℃.

[0083] Comparative Example 2

[0084] The Fe3O4 nanoparticles from Example 1 were ball-milled and mixed with magnesium hydride to prepare a hydrogen storage material in which the weight content of Fe3O4 was 7.5%.

[0085] The initial hydrogen release temperature of the above-mentioned hydrogen storage material is 253.3℃, ​​and the final hydrogen release amount is 6.617wt% when the target hydrogen release temperature is 400℃.

[0086] Comparative Example 3

[0087] The difference between Comparative Example 3 and Example 1 is that in the magnesium hydride hydrogen storage material, Fe3O4 and NiO are ball-milled composites, not a core-shell structure. Specifically:

[0088] 2.3 g of ferric chloride hexahydrate was dissolved in 100 mL of ethylene glycol. Then, 6 g of sodium acetate and 1.3 g of sodium citrate were added to the mixed solution and stirred until homogeneous. The mixture was then heated at 200 °C for 10 h to obtain a slurry containing solids. The slurry was then centrifuged, washed, and vacuum dried to obtain Fe3O4 nanoparticles.

[0089] After mixing the above Fe3O4 nanoparticles and NiO nanoparticles at a mass ratio of 1:1, magnesium hydride is added and ball milled for 15 hours at a ball milling speed of 450 r / min with a ball-to-material weight ratio of 40:1. This yields a magnesium hydride hydrogen storage material based on Fe3O4-NiO, in which the weight content of Fe3O4-NiO is 7.5%.

[0090] The initial hydrogen release temperature of the above-mentioned hydrogen storage material is 227.3℃, and the final hydrogen release amount is 6.10wt% when the target hydrogen release temperature is 400℃.

[0091] The relevant test results of the hydrogen storage materials prepared in the above embodiments and comparative examples are summarized in Table 1. Regarding the test methods used for the data in the table, further explanation is needed here:

[0092] The initial hydrogen release temperature was tested by performing a TPD (temperature programmed dehydrogenation) test at a heating rate of 2℃ / min.

[0093] The test method for the final hydrogen release amount at the target hydrogen release temperature of 400℃ is as follows: the hydrogen release amount at 400℃ is tested by TPD at a heating rate of 2℃ / min.

[0094] The capacity retention test method after 70 cycles of hydrogen absorption and desorption is as follows: 300℃, 30 bar (hydrogen absorption test); 300℃, 0.01 bar (hydrogen desorption test).

[0095] Table 1

[0096]

[0097] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0098] The hydrogen storage materials in Examples 1 to 12 are the magnesium hydride hydrogen storage materials based on Fe3O4@NiO proposed in this application. These materials are obtained by combining Fe3O4@NiO and magnesium hydride; wherein, Fe3O4@NiO has a core-shell structure with a NiO shell encapsulating a Fe3O4 core. According to the results in Table 1, the above-mentioned hydrogen storage materials exhibit a low hydrogen storage start-up temperature, high hydrogen desorption capacity, and stability. After 70 cycles of hydrogen absorption and desorption, the capacity retention rate remains above 90%, even reaching above 95%, indicating that the hydrogen storage material proposed in this application can effectively improve the hydrogen storage performance of magnesium hydride hydrogen storage materials. In particular, controlling the parameters in the Fe3O4@NiO-based magnesium hydride hydrogen storage material within the preferred range results in even better hydrogen storage performance.

[0099] In Comparative Example 1, using only magnesium hydride as the hydrogen storage material resulted in a high initial hydrogen release temperature and poor hydrogen storage stability. After 70 cycles of hydrogen absorption and desorption, the capacity retention rate was only about 70%, making multiple cycles difficult. In Comparative Example 2, a mixture of Fe3O4 nanoparticles and magnesium hydride was used as the hydrogen storage material. Its initial hydrogen release temperature, hydrogen release capacity, and hydrogen storage cycle stability showed significant differences compared to the Fe3O4@NiO-based magnesium hydride hydrogen storage material in this application. In Comparative Example 3, a mixture of Fe3O4 nanoparticles, NiO, and magnesium hydride was used as the hydrogen storage material. However, the Fe3O4-NiO mixture was not a shell structure but a simple composite. Consequently, the initial hydrogen release temperature, hydrogen release capacity, and hydrogen storage cycle stability of this hydrogen storage material also showed significant differences compared to the Fe3O4@NiO-based magnesium hydride hydrogen storage material in this application.

[0100] also, Figure 5 The following diagrams illustrate the temperature-programmed hydrogen release curves of the hydrogen storage materials prepared according to Examples 1, 4, 5, 6, 7, and Comparative Example 1. Analysis of the curves shows that in Comparative Example 1, using only magnesium hydride as the hydrogen storage material, hydrogen release begins at 324.2°C. After complete hydrogen release at 400°C, the dehydrogenation amount is 7.42 wt%, indicating a relatively high initial hydrogen release temperature. In Examples 1, 4, 5, 6, and 7, the proposed material, a composite of Fe3O4@NiO with a core-shell structure of NiO encapsulating a Fe3O4 core, and magnesium hydride, is used as the hydrogen storage material. The initial hydrogen release temperature of the corresponding hydrogen storage materials is significantly reduced while still maintaining a good dehydrogenation amount. In particular, the initial hydrogen release temperature of the hydrogen storage material in Example 1 is 115°C lower than that in Comparative Example 1.

[0101] Figure 6 The diagram shows the temperature-programmed hydrogen dehydrogenation curves of the hydrogen storage materials prepared according to Example 1 and Comparative Example 2 of the present invention. The curves show that the initial dehydrogenation temperature of the hydrogen storage material in Comparative Example 2 is 253.3°C, while the initial dehydrogenation temperature of the hydrogen storage material in Example 1 is significantly lower than that in Comparative Example 1, and the hydrogen storage capacity is also increased to a certain extent. This comparison more intuitively demonstrates that the hydrogen storage material of this application has excellent hydrogen storage performance.

[0102] Figure 7The isothermal hydrogen desorption diagrams of the hydrogen storage materials prepared according to Example 1 and Comparative Example 1 at different temperatures are shown. The diagrams show that at 325°C, the hydrogen storage material of Example 1 achieves a dehydrogenation rate of 6.2 wt% within 5 minutes, while the hydrogen storage material of Comparative Example 1 only achieves 0.14 wt% at the same temperature and time. This demonstrates that even at higher temperatures, the hydrogen storage material of Comparative Example 1 still exhibits a significant difference in dehydrogenation efficiency compared to the hydrogen storage material of this application. Furthermore, hydrogen desorption performance tests were conducted on the hydrogen storage material of Example 1 at lower temperatures of 275°C and 300°C. The corresponding hydrogen desorption efficiencies still show a clear advantage over the hydrogen storage material of Comparative Example 1 at 325°C. Therefore, the magnesium hydride hydrogen storage material based on Fe3O4@NiO proposed in this application not only has a lower initial dehydrogenation temperature but also a faster dehydrogenation kinetic rate.

[0103] Figure 8 The figure shows isothermal hydrogen absorption diagrams of the magnesium hydride hydrogen storage material based on Fe3O4@NiO prepared according to Example 1 of the present invention at different temperatures. As can be seen from the figure, the magnesium hydride hydrogen storage material based on Fe3O4@NiO in Example 1 can achieve hydrogen absorption at both low and high temperatures. In particular, the hydrogen storage material after complete hydrogen release at 175°C can absorb 5.56 wt% of hydrogen in 1 minute, indicating that its hydrogen absorption kinetics are good.

[0104] Figure 9 The isothermal desorption / adsorption cycle curve of the magnesium hydride hydrogen storage material based on Fe3O4@NiO prepared according to Example 1 of the present invention is shown, with a cycle temperature of 300℃. The curve shows that the catalyst retains its capacity well after 70 cycles of hydrogen adsorption and desorption, indicating good cycle stability.

[0105] In summary, this invention provides a magnesium hydride hydrogen storage material based on Fe3O4@NiO. Through the dual-valence characteristics of Fe3O4, the interaction between Fe3O4 and MgH2, the interaction between NiO and MgH2, and the multiple synergistic effects between Fe and Ni in the core-shell structure of Fe3O4@NiO, a magnesium hydride hydrogen storage material with excellent hydrogen storage capacity is constructed via mechanisms such as electron transfer, increased active sites, and synergistic catalysis. This significantly improves the hydrogen storage performance of magnesium hydride, reduces the start-up temperature of hydrogen storage, increases the hydrogen release rate, and optimizes the hydrogen absorption and desorption kinetics, providing technical support for hydrogen energy storage.

[0106] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A magnesium hydride hydrogen storage material based on Fe3O4@NiO, characterized in that, The hydrogen storage material is obtained by combining Fe3O4@NiO and magnesium hydride; The Fe3O4@NiO has a core-shell structure in which a NiO shell encapsulates a Fe3O4 core.

2. The magnesium hydride hydrogen storage material based on Fe3O4@NiO according to claim 1, characterized in that, The weight content of Fe3O4@NiO in the hydrogen storage material is 2.5~12.5%; Preferably, the weight content of Fe3O4@NiO in the hydrogen storage material is 5~12.5%.

3. The magnesium hydride hydrogen storage material based on Fe3O4@NiO according to claim 1 or 2, characterized in that, In the Fe3O4@NiO, the molar ratio of Fe to Ni is 1:(0.79~1.33). Preferably, in the Fe3O4@NiO, the molar ratio of Fe to Ni is 1:(0.9~1.2). Preferably, the particle size of the Fe3O4@NiO is 100~200nm; Preferably, the hydrogen storage material is obtained by ball milling the Fe3O4@NiO and the magnesium hydride; Preferably, the particle size of the Fe3O4@NiO-based magnesium hydride hydrogen storage material is 200~300nm.

4. A method for preparing a magnesium hydride hydrogen storage material based on Fe3O4@NiO according to any one of claims 1 to 3, characterized in that, The preparation method of the Fe3O4@NiO magnesium hydride hydrogen storage material includes the following steps: Soluble iron salts are dissolved in a first solvent, a stabilizer is added, and the mixture is heated to carry out a first reaction. The resulting first reaction slurry is then subjected to a first separation and a first drying process to obtain Fe3O4 nanoparticles. The Fe3O4 nanoparticles were dispersed in a second solvent, and a soluble nickel salt was added to it. The mixture was then heated to carry out a second reaction. The resulting second reaction slurry was subjected to a second separation and a second drying process to obtain the Fe3O4@NiO precursor. The Fe3O4@NiO precursor was then calcined to obtain the Fe3O4@NiO material. The Fe3O4@NiO material and magnesium hydride were mixed and ball-milled to obtain the Fe3O4@NiO-based magnesium hydride hydrogen storage material.

5. The method for preparing magnesium hydride hydrogen storage material based on Fe3O4@NiO according to claim 4, characterized in that, The temperature of the first reaction is 170~220℃, and the time is 8~12h; Preferably, the temperature of the second reaction is 140~280℃ and the time is 4~8h.

6. The method for preparing magnesium hydride hydrogen storage material based on Fe3O4@NiO according to claim 4, characterized in that, The weight ratio of the soluble iron salt to the stabilizer is (1~2):(5~6). Preferably, the stabilizer is a sodium salt of an organic acid, more preferably sodium acetate and / or sodium citrate; Preferably, the sodium acetate and sodium citrate are combined as a stabilizer; more preferably, the weight ratio of sodium acetate to sodium citrate is (4~5):

1.

7. The method for preparing magnesium hydride hydrogen storage material based on Fe3O4@NiO according to claim 4 or 5, characterized in that, The molar ratio of Fe in the Fe3O4 nanoparticles to Ni in the soluble nickel salt is 1:(0.79~1.33). Preferably, the concentration of the soluble iron salt in the first solvent is 0.084~0.085 mol / L; preferably, the concentration of the soluble nickel salt in the second solvent is 0.09~0.11 mol / L. Preferably, the first solvent is an alcohol solvent, more preferably ethylene glycol; Preferably, the second solvent is an alcohol solvent, more preferably ethylene glycol.

8. The method for preparing magnesium hydride hydrogen storage material based on Fe3O4@NiO according to claim 4 or 5, characterized in that, The calcination is carried out under a protective atmosphere; Preferably, the protective gas is argon; Preferably, the calcination temperature is 320~380℃ and the time is 1~4h.

9. The method for preparing magnesium hydride hydrogen storage material based on Fe3O4@NiO according to any one of claims 4 to 8, characterized in that, The weight ratio of the Fe3O4@NiO material to the magnesium hydride is (5~12.5):(95~87.5). Preferably, the ball milling is carried out under a hydrogen atmosphere; Preferably, in the ball milling process, the ball-to-material weight ratio is (30~50):1; the ball milling speed is 300~600 rpm; and the ball milling time is 10~20 h. Preferably, the particle size of the Fe3O4@NiO-based magnesium hydride hydrogen storage material is 200~300nm.

10. The application of the Fe3O4@NiO-based magnesium hydride hydrogen storage material according to any one of claims 1 to 3, characterized in that, The Fe3O4@NiO-based magnesium hydride hydrogen storage material is used in the field of hydrogen storage.

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