Magnesium-based hydrogen storage material based on core-shell structure, preparation method therefor, and use thereof

Abstract

The present disclosure relates to the technical field of solid-state hydrogen storage materials, and specifically provides a magnesium-based hydrogen storage material based on a core-shell structure, a preparation method therefor, and use thereof. The magnesium-based hydrogen storage material based on a core-shell structure provided by the present disclosure comprises a hydrogenated combustion product of Ni / Fe3O4@MIL and MgH2, wherein Ni / Fe3O4@MIL is a material having a core-shell structure. An inner core of Ni / Fe3O4@MIL comprises Ni-loaded Fe3O4 microspheres, and an outer shell of Ni / Fe3O4@MIL comprises an organic ligand. The magnesium-based hydrogen storage material based on a core-shell structure significantly improves the hydrogen storage performance of magnesium hydride, and can still maintain a high hydrogen absorption capacity at a low temperature.

Description

A magnesium-based hydrogen storage material based on a core-shell structure and a preparation method and application thereof TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of magnesium-based solid-state hydrogen storage materials, in particular to a magnesium-based hydrogen storage material based on a core-shell structure and a preparation method and application thereof. BACKGROUND

[0002] With the emergence of energy crisis and environmental problems, the development of clean and renewable energy has attracted worldwide attention. Hydrogen energy has the advantages of low cost, abundant reserves, recyclability, and high energy content per unit mass (142 MJ / kg), and is considered to be the most promising energy source to replace traditional fossil fuels.

[0003] However, achieving efficient and safe hydrogen storage technology has become a bottleneck for large-scale application of hydrogen energy. Among the existing various solid-state hydrogen storage materials (such as LiAlH4, NaAlH6, NaBH4, etc.), MgH2 is one of the most promising hydrogen storage materials due to its high hydrogen storage capacity (7.6%), excellent reversibility, and low price. However, the high thermodynamic stability and slow kinetics of MgH2 limit its commercial application. Numerous studies have shown that additive doping with a unique structure is the most likely method to achieve practical application of magnesium-based hydrogen storage materials.

[0004] CN108689384A discloses a composite hydrogen storage material, which comprises the following components by weight parts: MgCNi3 10-40 parts by weight; MgH2 60-90 parts by weight. The composite hydrogen storage material has the advantages of low hydrogen release temperature, fast hydrogen release rate, and high hydrogen release amount. However, it is found that the isothermal hydrogen absorption amount is less than 4.0wt% at a lower temperature, such as 100℃, and the hydrogen storage capacity is greatly reduced.

[0005] CN114538378A discloses a composite hydrogen storage material, and the preparation method thereof is as follows: the raw materials magnesium powder and aluminum powder are weighed according to the molar ratio of the designed components, then added to anhydrous organic solvent, ultrasonically dispersed, mixed uniformly, and dried; using the hydrogenation combustion synthesis process, heating to 400-450℃ for 0-2h for activation, then cooling to 330-350℃ for 1-5h for hydrogenation, to obtain a high-purity magnesium-based hydrogen storage material, and the product phase composition is MgH2, Al, and Mg. Although the addition of an appropriate amount of aluminum powder significantly improves the hydrogenation degree of magnesium, the hydrogen storage capacity at a lower temperature still needs to be improved.

[0006] CN111515380A discloses a high-capacity magnesium-based composite hydrogen storage material and a preparation method thereof, and the composite hydrogen storage material has a phase composition of Mg x Al1 00-x-yThe structure and composition of the composite hydrogen storage material are shown as (z wt% Ni@Gn). The main phase of the composite hydrogen storage material is granular MgH2, and the Ni, Al and graphene phases are uniformly distributed around the MgH2 particles. The method uses magnesium powder, aluminum powder, graphene nanosheet, nickel nitrate and other conventional products as raw materials, and is prepared based on hydrogen combustion synthesis and ball milling. The hydrogenation degree of magnesium is high.

[0007] Therefore, it is essential to study a high-capacity composite hydrogen storage material for the field of hydrogen storage.

[0008] DISCLOSURE

[0009] The purpose of the present disclosure includes providing a magnesium-based hydrogen storage material based on a core-shell structure and a preparation method and application thereof. The material significantly improves the hydrogen storage performance of magnesium hydride and can still maintain a high hydrogen absorption capacity at low temperature.

[0010] In order to achieve at least one of the above purposes of the present disclosure, the following technical solutions are adopted:

[0011] In a first aspect, the present disclosure provides a magnesium-based hydrogen storage material based on a core-shell structure, which includes a hydrogenation combustion product of Ni / Fe3O4@MIL and MgH2.

[0012] Preferably, the mass ratio of the hydrogenation combustion product of Ni / Fe3O4@MIL and MgH2 is (1-2):(5-15).

[0013] Preferably, in the Ni / Fe3O4@MIL, the particle size of the core is 350-400 nm.

[0014] Preferably, in the Ni / Fe3O4@MIL, the thickness of the shell is 50-100 nm.

[0015] Preferably, in the core of the Ni / Fe3O4@MIL, the loading amount of Ni is 70-80%.

[0016] Preferably, the organic ligand is trimesic acid.

[0017] Preferably, the organic ligand is trimesic acid.

[0018] In a second aspect, the present disclosure provides a preparation method of the magnesium-based hydrogen storage material based on a core-shell structure according to the first aspect, which includes the following steps:

[0019] (1) mixing the iron salt, the alkaline adjusting agent and the alcohol solvent, and then performing a first hydrothermal reaction to obtain Fe3O4 microspheres;

[0020] (2) mixing the Fe3O4 microspheres, the nickel salt and the alcohol solvent, mixing and stirring with the hydrazine hydrate solution, and then performing a second hydrothermal reaction to obtain the Fe3O4 microspheres loaded with Ni;

[0021] (3) mixing the Fe3O4 microspheres loaded with Ni, the trimesic acid and the solvent, and then performing a third hydrothermal reaction to obtain the Ni / Fe3O4@MIL with a core-shell structure;

[0022] (4) mixing the Ni / Fe3O4@MIL and the metal Mg, and then performing hydrogenation combustion and ball milling to obtain the magnesium-based hydrogen storage material based on the core-shell structure.

[0023] Preferably, in step (1), the mass ratio of the iron salt, the alkali and the alcohol solvent is (3-4):(2-3):(75-80).

[0024] Optionally, in step (1), the iron salt is selected from any one or a combination of at least two of ferric chloride, ferric nitrate, ferric sulfate, ferric acetate or ferric citrate, and is preferably ferric chloride.

[0025] Optionally, in step (1), the alkaline adjusting agent is selected from any one or a combination of at least two of sodium formate, sodium acetate, sodium propionate, potassium formate, potassium acetate, ammonium formate or ammonium acetate, and is preferably sodium acetate.

[0026] Optionally, in steps (1) and (2), the alcohol solvent is independently selected from any one or a combination of at least two of ethylene glycol, propylene glycol, glycerol or diethylene glycol, and is preferably ethylene glycol.

[0027] Preferably, in step (1), the temperature of the first hydrothermal reaction is 423-523 K.

[0028] Preferably, in step (1), the time of the first hydrothermal reaction is 5-10 h.

[0029] Preferably, in step (2), the mass ratio of the Fe3O4 microspheres, the nickel salt, the alcohol solvent and the hydrazine hydrate solution is (0.2-1):(1-2):(50-60):(20-30).

[0030] Optionally, in step (2), the nickel salt is selected from any one or a combination of at least two of nickel chloride, nickel nitrate, nickel sulfate, nickel acetate or nickel citrate, and is preferably nickel chloride.

[0031] Optionally, in step (2), the content of hydrazine hydrate in the hydrazine hydrate solution is 3-5 wt%.

[0032] Preferably, the hydrazine hydrate solution further comprises 3-5 wt% of an alkaline substance.

[0033] Optionally, the alkaline substance is selected from sodium hydroxide and / or potassium hydroxide.

[0034] Preferably, in step (2), the temperature of the second hydrothermal reaction is 323-393 K.

[0035] Preferably, in step (2), the time of the second hydrothermal reaction is 1-2 h.

[0036] Preferably, in step (3), the mass ratio of the Ni-loaded Fe3O4 microspheres, trimesic acid and solvent is (0.1-0.2):(0.5-1):(40-50).

[0037] Preferably, in step (3), the temperature of the third hydrothermal reaction is 323-423 K.

[0038] Preferably, in step (3), the time of the third hydrothermal reaction is 24-48 h.

[0039] Preferably, in step (4), the mass ratio of the Ni / Fe3O4@MIL and metal Mg is 1:(5-15).

[0040] Preferably, in step (4), during the hydrogenation combustion, the pressure of hydrogen is 3.5-4.0 MPa, the heating rate is 2-5 K / min, the holding temperature is 623-673 K, and the holding time is 30-40 h.

[0041] Preferably, in step (4), during the ball milling, the rotation speed of the ball milling is 300-500 rpm, the ball milling time is 10-20 min, the interval is 5-10 min, and the ball-to-material ratio is (20-40):1.

[0042] In a third aspect, the present disclosure provides a use of the magnesium-based hydrogen storage material based on the core-shell structure according to the first aspect in low-temperature hydrogen storage.

[0043] Compared with the prior art, the present disclosure has the following beneficial effects:

[0044] (1) The present disclosure provides a kind of magnesium-based hydrogen storage material based on core-shell structure, the magnesium-based hydrogen storage material based on core-shell structure includes the hydrogenation combustion product of Ni / Fe3O4@MIL and MgH2;Wherein, the Ni / Fe3O4@MIL is the material with core-shell structure, the inner core of the Ni / Fe3O4@MIL includes Ni loaded Fe3O4 microsphere, the shell of the Ni / Fe3O4@MIL includes trimesic acid.The material significantly improves the hydrogen storage performance of magnesium hydride, can still maintain high hydrogen absorption capacity at low temperature.

[0045] (2) The present disclosure provides a kind of preparation method of the magnesium-based hydrogen storage material based on core-shell structure, the raw material cost used in preparation is low, simple and easy to obtain, the additive is combined with magnesium powder by ball milling composite mode.In the process of hydrogen absorption and release reaction, the unique core-shell structure not only provides more reaction sites, but also prevents particle agglomeration, maintains high catalytic stability, has great advantage in reducing the dehydrogenation temperature of magnesium-based hydrogen storage material. BRIEF DESCRIPTION OF DRAWINGS

[0046] Fig. 1 is the hydrogen absorption curve of the magnesium-based hydrogen storage material based on core-shell structure provided by Example 1 of the present disclosure and the hydrogen storage material provided by Comparative Example 1 at 423K.

[0047] Fig. 2 is the hydrogen absorption curve of the magnesium-based hydrogen storage material based on core-shell structure provided by Example 1 of the present disclosure and the hydrogen storage material provided by Comparative Example 1 at 373K.

[0048] Fig. 3 is the hydrogen absorption curve of the magnesium-based hydrogen storage material based on core-shell structure provided by Example 1 of the present disclosure and the hydrogen storage material provided by Comparative Example 1 at 623K.

[0049] Fig. 4 is the hydrogen absorption curve of the magnesium-based hydrogen storage material based on core-shell structure provided by Example 1 of the present disclosure and the hydrogen storage material provided by Comparative Example 1 at 598K. DETAILED DESCRIPTION

[0050] The embodiments of the present disclosure will be described in detail below with examples, but those skilled in the art will understand that the following examples are only for illustration of the present disclosure, and should not be regarded as limiting the scope of the present disclosure. If no specific conditions are specified in the examples, the conventional conditions or the conditions recommended by the manufacturer are used.

[0051] At present, in order to further improve the hydrogen storage performance of magnesium-based hydrogen storage materials, alloying, adding catalysts, nanocrystallization, surface modification and other methods are often used to improve it. The main catalyst types known to be used include transition metals, transition metal oxides / halides / sulfides / hydrides, intermetallic compounds and / or other non-metallic materials. However, although the existing catalysts can improve the hydrogenation degree of magnesium to some extent, it is found through research that the isothermal hydrogen absorption capacity at low temperature is low, which greatly reduces the hydrogen storage capacity. The high hydrogen storage and release temperature and slow hydrogen absorption and release speed of magnesium-based hydrogen storage materials greatly restrict their practical application.

[0052] The present disclosure provides a magnesium-based hydrogen storage material based on a core-shell structure and a preparation method and application thereof to solve the technical problems existing in the prior art. The material significantly improves the hydrogen storage performance of magnesium hydride and can maintain high hydrogen absorption capacity at low temperature.

[0053] In a first aspect, the present disclosure provides a magnesium-based hydrogen storage material based on a core-shell structure, which comprises a hydrogenation combustion product of Ni / Fe3O4@MIL and MgH2.

[0054] The Ni / Fe3O4@MIL is a material with a core-shell structure, the inner core of the Ni / Fe3O4@MIL comprises Ni-loaded Fe3O4 microspheres, and the outer shell of the Ni / Fe3O4@MIL comprises trimesic acid.

[0055] The magnesium-based hydrogen storage material based on a core-shell structure provided by the present disclosure is a composite magnesium-based hydrogen storage material, which takes MgH2 as the main component and contains a hydrogenation combustion product of Ni / Fe3O4@MIL; the Ni / Fe3O4@MIL is a material with a core-shell structure, the inner core of the Ni / Fe3O4@MIL comprises Ni-loaded Fe3O4 microspheres, and the outer shell of the Ni / Fe3O4@MIL comprises an organic ligand. In the hydrogen absorption and release reaction process, the unique core-shell structure of the Ni / Fe3O4@MIL provides more reaction sites and can also prevent particle agglomeration, thereby maintaining high catalytic stability, significantly improving the hydrogen storage performance of magnesium hydride, and significantly reducing the hydrogen release temperature of the magnesium-based hydrogen storage material.

[0056] Preferably, the mass ratio of the hydrogenation combustion product of the Ni / Fe3O4@MIL and MgH2 is (1-2):(5-15);

[0057] For example, "1-2" can be 1, 1.2, 1.4, 1.6, 1.8, 2, etc.

[0058] For example, "5-15" can be 5, 6, 8, 10, 12, 14, 15, etc.

[0059] Preferably, in the Ni / Fe3O4@MIL, the particle size of the inner core is 350-400 nm, for example, it can be 350 nm, 355 nm, 360 nm, 365 nm, 370 nm, 375 nm, 380 nm, 385 nm, 390 nm, 395 nm, 400 nm, etc.

[0060] Preferably, in the Ni / Fe3O4@MIL, the thickness of the shell is 50-100 nm, for example, it can be 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, etc.

[0061] Preferably, the organic ligand is trimesic acid.

[0062] Preferably, in the inner core of the Ni / Fe3O4@MIL, the loading amount of Ni is 70-80%, for example, it can be 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 90%, etc.

[0063] In a second aspect, the present disclosure provides a preparation method of the magnesium-based hydrogen storage material based on core-shell structure according to the first aspect, and the preparation method comprises the following steps:

[0064] (1) After mixing the iron salt, the alkaline adjusting agent and the alcohol solvent, a first hydrothermal reaction is performed to obtain Fe3O4 microspheres;

[0065] (2) After mixing the Fe3O4 microspheres, the nickel salt and the alcohol solvent, and mixing and stirring with the hydrazine hydrate solution, a second hydrothermal reaction is performed to obtain Ni-loaded Fe3O4 microspheres;

[0066] (3) After mixing the Ni-loaded Fe3O4 microspheres, the trimesic acid and the solvent, a third hydrothermal reaction is performed to obtain the Ni / Fe3O4@MIL with core-shell structure;

[0067] (4) After mixing the Ni / Fe3O4@MIL and the metal Mg, and through hydrogenation combustion and ball milling, the magnesium-based hydrogen storage material based on core-shell structure is obtained.

[0068] The present disclosure provides a preparation method of a magnesium-based hydrogen storage material, which comprises the following steps: first, preparing a core-shell structure of Ni / Fe3O4@MIL, wherein the core is a Fe3O4 microsphere loaded with Ni, and the shell is a trimesic acid; and then, making the Ni / Fe3O4@MIL and magnesium powder co-hydrogenate and ball mill to obtain the magnesium-based hydrogen storage material based on the core-shell structure. The raw materials used in the preparation method are low in cost and easy to obtain, and the combination of the Ni / Fe3O4@MIL and the magnesium powder is realized through co-hydrogenation and ball milling, which can provide more reaction sites and prevent particle agglomeration, thereby maintaining high catalytic stability.

[0069] In one preferred embodiment of the present disclosure, in step (1), the mass ratio of the iron salt, the base and the alcohol solvent is (3-4):(2-3):(75-80).

[0070] For example, “3-4” can be 3, 3.2, 3.4, 3.6, 3.8, 4, etc.

[0071] For example, “2-3” can be 2, 2.2, 2.4, 2.6, 2.8, 3, etc.

[0072] For example, “75-80” can be 75, 76, 77, 78, 79, 80, etc.

[0073] In one preferred embodiment of the present disclosure, in step (1), the iron salt is selected from any one or a combination of at least two of ferric chloride, ferric nitrate, ferric sulfate, ferric acetate or ferric citrate, and is preferably ferric chloride.

[0074] In one preferred embodiment of the present disclosure, in step (1), the base regulator is selected from any one or a combination of at least two of sodium formate, sodium acetate, sodium propionate, potassium formate, potassium acetate, ammonium formate or ammonium acetate, and is preferably sodium acetate.

[0075] In one preferred embodiment of the present disclosure, in steps (1) and (2), the alcohol solvent is independently selected from any one or a combination of at least two of ethylene glycol, propylene glycol, glycerol or diethylene glycol, and is preferably ethylene glycol.

[0076] In one optional embodiment of the present disclosure, in step (1), the mixing of the iron salt, the base regulator and the alcohol solvent specifically comprises the following steps: first, dissolving the iron salt in the alcohol solvent, then adding the base regulator, and stirring to obtain a uniform solution.

[0077] In an alternative embodiment of the present disclosure, in step (1), the stirring speed is 300-600 rpm, for example, 300 rpm, 350 rpm, 400 rpm, 450 rpm, 500 rpm, 550 rpm, 600 rpm, etc., and the stirring time is 20-45 min, for example, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, etc.

[0078] In a preferred embodiment of the present disclosure, in step (1), the temperature of the first hydrothermal reaction is 423-523 K, for example, 423 K, 433 K, 443 K, 453 K, 463 K, 473 K, 483 K, 493 K, 503 K, 513 K, 523 K, etc.

[0079] In a preferred embodiment of the present disclosure, in step (1), the time of the first hydrothermal reaction is 5-10 h, for example, 5 h, 5.5 h, 6 h, 6.5 h, 7 h, 7.5 h, 8 h, 8.5 h, 9 h, 9.5 h, 10 h, etc.

[0080] In an alternative embodiment of the present disclosure, in step (1), the first hydrothermal reaction is carried out in a stainless steel reactor with polytetrafluoroethylene.

[0081] In an alternative embodiment of the present disclosure, in step (1), after the first hydrothermal reaction, a post-treatment step is further included: after the first hydrothermal reaction is completed, the reaction solution is cooled to room temperature, the solid powder is collected, first washed by centrifugation with water, then washed by centrifugation with anhydrous ethanol, the solid is collected and dried to obtain Fe3O4 microspheres.

[0082] In an alternative embodiment of the present disclosure, in step (1), the first centrifugal washing speed is 2000-3000 rpm, for example, 2000 rpm, 2200 rpm, 2400 rpm, 2600 rpm, 2800 rpm, 3000 rpm, etc., the first centrifugal washing is at least 2 times, for example, 2 times, 3 times, 4 times, 5 times, etc., and the water usage is 50-80 times the mass of the solid powder, for example, 50 times, 55 times, 60 times, 65 times, 70 times, 75 times, 80 times, etc.

[0083] In a preferred embodiment of the present disclosure, in step (2), the mass ratio of the Fe3O4 microspheres, nickel salt, alcohol solvent, and hydrazine hydrate solution is (0.2-1):(1-2):(50-60):(20-30).

[0084] For example, "0.2-1" can be 0.2, 0.4, 0.5, 0.6, 0.7, 0.8, 1, etc.

[0085] For example, "1-2" can be 1, 1.2, 1.4, 1.6, 1.8, 2, etc.

[0086] For example, "50-60" can be 50, 52, 54, 56, 58, 60, etc.

[0087] For example, "20-30" can be 20, 22, 24, 26, 28, 30, etc.

[0088] In one preferred embodiment of the present disclosure, in step (2), the nickel salt is selected from any one or a combination of at least two of nickel chloride, nickel nitrate, nickel sulfate, nickel acetate or nickel citrate, preferably nickel chloride.

[0089] In one optional embodiment of the present disclosure, in step (2), the mixing of the Fe3O4 microspheres, the nickel salt and the alcohol solvent specifically comprises the following steps: dissolving the Fe3O4 microspheres in the alcohol solvent and performing a first ultrasonic treatment, then adding the nickel salt and performing a second ultrasonic treatment to obtain a mixed solution.

[0090] In one optional embodiment of the present disclosure, in step (2), the power of the first ultrasonic treatment is 600-900 W, for example, can be 600 W, 650 W, 700 W, 750 W, 800 W, 850 W, 900 W, etc.; the time of the first ultrasonic treatment is 1-3 h, for example, can be 1 h, 1.2 h, 1.4 h, 1.6 h, 1.8 h, 2 h, 2.2 h, 2.4 h, 2.6 h, 2.8 h, 3 h, etc.

[0091] In one optional embodiment of the present disclosure, in step (2), the power of the second ultrasonic treatment is 600-900 W, for example, can be 600 W, 650 W, 700 W, 750 W, 800 W, 850 W, 900 W, etc.; the time of the second ultrasonic treatment is 1-2 h, for example, can be 1 h, 1.2 h, 1.4 h, 1.6 h, 1.8 h, 2 h, etc.

[0092] In one preferred embodiment of the present disclosure, in step (2), the content of the hydrazine hydrate in the hydrazine hydrate solution is 3-5 wt%, for example, can be 3 wt%, 3.2 wt%, 3.4 wt%, 3.6 wt%, 3.8 wt%, 4 wt%, 4.2 wt%, 4.4 wt%, 4.6 wt%, 4.8 wt%, 5 wt%, etc.

[0093] In one preferred embodiment of the present disclosure, the hydrazine hydrate solution further comprises a basic substance.

[0094] In one preferred embodiment of the present disclosure, the content of the basic substance in the aqueous hydrazine solution is 3-5 wt%, for example, it can be 3 wt%, 3.2 wt%, 3.4 wt%, 3.6 wt%, 3.8 wt%, 4 wt%, 4.2 wt%, 4.4 wt%, 4.6 wt%, 4.8 wt%, 5 wt%, etc.

[0095] In one preferred embodiment of the present disclosure, the basic substance is selected from sodium hydroxide and / or potassium hydroxide.

[0096] In one optional embodiment of the present disclosure, in step (2), the addition of the aqueous hydrazine solution is carried out under the condition of non-magnetic stirring of the above mixture, and an agitator can be used for stirring.

[0097] In one optional embodiment of the present disclosure, in step (2), during the addition of the aqueous hydrazine solution, the stirring speed is 300-600 rpm, for example, it can be 300 rpm, 350 rpm, 400 rpm, 450 rpm, 500 rpm, 550 rpm, 600 rpm, etc., and the stirring time is 10-20 min, for example, it can be 10 min, 12 min, 14 min, 16 min, 18 min, 20 min, etc.

[0098] In one preferred embodiment of the present disclosure, in step (2), the temperature of the second hydrothermal reaction is 323-393 K, for example, it can be 323 K, 333 K, 343 K, 353 K, 363 K, 373 K, 383 K, 393 K, etc.

[0099] In one preferred embodiment of the present disclosure, in step (2), the time of the second hydrothermal reaction is 1-2 h, for example, it can be 1 h, 1.2 h, 1.4 h, 1.6 h, 1.8 h, 2 h, etc.

[0100] In one optional embodiment of the present disclosure, in step (2), the second hydrothermal reaction is carried out in a high-pressure reaction kettle.

[0101] In one optional embodiment of the present disclosure, in step (2), after the second hydrothermal reaction, a post-processing step is further included: the obtained product is washed by using water and ethanol under the action of a magnet, the precipitate after washing is collected by using a refrigerated vacuum drying means, and the residual solvent of the freeze-dried product is removed to obtain the Ni-loaded Fe3O4 microspheres.

[0102] In one preferred embodiment of the present disclosure, in step (3), the mass ratio of the Ni-loaded Fe3O4 microspheres, trimesic acid and solvent is (0.1-0.2):(0.5-1):(40-50).

[0103] wherein, for example, "0.1-0.2" can be 0.1, 0.12, 0.14, 0.16, 0.18, 0.2, etc.

[0104] wherein, for example, "0.5-1" can be 0.5, 0.6, 0.7, 0.8, 0.9, 1, etc.

[0105] wherein, for example, "40-50" can be 40, 42, 44, 46, 48, 50, etc.

[0106] In one preferred embodiment of the present disclosure, in step (3), the solvent is DMF.

[0107] In one optional embodiment of the present disclosure, in step (3), the mixing of the Ni-loaded Fe3O4 microspheres, the trimesic acid and the solvent specifically comprises the following steps: dissolving the Ni-loaded Fe3O4 microspheres and the trimesic acid in the solvent, and then ultrasonic treatment to obtain a uniformly dispersed solution.

[0108] In one optional embodiment of the present disclosure, in step (3), the ultrasonic treatment is performed at a power of 600-900 W, for example, 600 W, 650 W, 700 W, 750 W, 800 W, 850 W, 900 W, etc., and for a time of 1-2 h, for example, 1 h, 1.2 h, 1.4 h, 1.6 h, 1.8 h, 2 h, etc.

[0109] In one preferred embodiment of the present disclosure, in step (3), the third hydrothermal reaction is performed at a temperature of 323-423 K, for example, 323 K, 333 K, 343 K, 353 K, 363 K, 373 K, 383 K, 393 K, 403 K, 413 K, 423 K, etc.

[0110] In one preferred embodiment of the present disclosure, in step (3), the third hydrothermal reaction is performed for a time of 24-48 h, for example, 24 h, 26 h, 28 h, 30 h, 32 h, 34 h, 36 h, 38 h, 40 h, 42 h, 44 h, 46 h, 48 h, etc.

[0111] In one optional embodiment of the present disclosure, in step (3), the third hydrothermal reaction is performed in a high-pressure reaction kettle.

[0112] In one optional embodiment of the present disclosure, in step (3), after the third hydrothermal reaction, a post-treatment step is further included: after the third hydrothermal reaction is completed, the reaction liquid is cooled to room temperature, the solid powder is collected, first washed by centrifugation with water, then washed by centrifugation with anhydrous ethanol, the solid is collected and dried to obtain the Ni / Fe3O4@MIL.

[0113] In an optional embodiment of the present disclosure, in step (3), the power of the first ultrasonic treatment is 600-900 W, for example, it can be 600 W, 650 W, 700 W, 750 W, 800 W, 850 W, 900 W, etc.; the time of the first ultrasonic treatment is 1-3 h, for example, it can be 1 h, 1.2 h, 1.4 h, 1.6 h, 1.8 h, 2 h, 2.2 h, 2.4 h, 2.6 h, 2.8 h, 3 h, etc.

[0114] In an optional embodiment of the present disclosure, in step (3), the power of the second ultrasonic treatment is 600-900 W, for example, it can be 600 W, 650 W, 700 W, 750 W, 800 W, 850 W, 900 W, etc.; the time of the second ultrasonic treatment is 1-2 h, for example, it can be 1 h, 1.2 h, 1.4 h, 1.6 h, 1.8 h, 2 h, etc.

[0115] In a preferred embodiment of the present disclosure, in step (4), the mass ratio of the Ni / Fe3O4@MIL and the metal Mg is 1:(5-15), for example, it can be 1:5, 1:5.5, 1:6, 1:6.5, 1:7, 1:7.5, 1:8, 1:8.5, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, etc.

[0116] In a preferred embodiment of the present disclosure, in step (4), in the process of hydrogenation combustion, the pressure of hydrogen is 3.5-4.0 MPa, for example, it can be 3.5 MPa, 3.6 MPa, 3.7 MPa, 3.8 MPa, 3.9 MPa, 4.0 MPa, etc.; the heating rate is 2-5 K / min, for example, it can be 2 K / min, 2.5 K / min, 3 K / min, 3.5 K / min, 4 K / min, 4.5 K / min, 5 K / min, etc.; the temperature of the heat preservation is 623-673 K, for example, it can be 623 K, 633 K, 643 K, 653 K, 663 K, 673 K, etc.; the time of the heat preservation is 30-40 h, for example, it can be 30 h, 32 h, 34 h, 36 h, 38 h, 40 h, etc.

[0117] In one preferred embodiment of the present disclosure, in step (4), the rotation speed of the ball milling is 300-500 rpm, for example, it can be 300 rpm, 350 rpm, 400 rpm, 450 rpm, 500 rpm, etc., the ball milling time is 10-20 min, for example, it can be 10 min, 12 min, 14 min, 16 min, 18 min, 20 min, etc., the interval is 5-10 min, for example, it can be 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, etc., the ball-to-material ratio is (20-40):1, for example, it can be 20:1, 22:1, 25:1, 28:1, 30:1, 32:1, 34:1, 35:1, 36:1, 40:1, etc.

[0118] In a third aspect, the present disclosure provides an application of the magnesium-based hydrogen storage material based on core-shell structure in low-temperature hydrogen storage according to the first aspect.

[0119] The raw materials used for preparing the magnesium-based hydrogen storage material based on core-shell structure according to the present disclosure are low in cost and easy to obtain, and the combination of the additive and the magnesium powder is through a ball milling compounding method. In the hydrogen absorption and desorption reaction process, the unique core-shell structure not only provides more reaction sites, but also prevents particle agglomeration and maintains high catalytic stability, which has great advantages in reducing the hydrogen desorption temperature of the magnesium-based hydrogen storage material.

[0120] In order to help more clearly understand the content of the present disclosure, the specific embodiments are described in detail as follows. However, these embodiments are only exemplary and do not constitute any limitation on the scope of the present disclosure.

[0121] Example 1

[0122] The present embodiment provides a magnesium-based hydrogen storage material based on core-shell structure, which is prepared by the following steps:

[0123] S1, Preparation of Fe3O4 microspheres

[0124] 3.46 g of FeCl3·6H2O was dissolved in 70 mL of ethylene glycol, then 2.66 g of anhydrous sodium acetate was added to the above solution, and the solution was stirred at a rotation speed of 600 rpm by a magnetic stirrer for 0.5 h to form a uniform yellow solution; then the solution was poured into a 100 mL stainless steel reaction kettle lined with polytetrafluoroethylene, and transferred to a blast drying oven, and the reaction temperature was set to 473 K and the reaction time was 8 h. After the reaction was completed, the reaction kettle was taken out of the drying oven and naturally cooled to room temperature. After pouring out the liquid, it was first washed with water for centrifugation three times, and then washed with anhydrous ethanol for centrifugation three times. After completion, the product was dried in a vacuum drying oven at a temperature of 333 K. Finally, a black powder was obtained, which was Fe3O4 microspheres.

[0125] S2, Preparation of Fe3O4 microspheres loaded with Ni

[0126] Take 50 mL of ethylene glycol, add 0.45 g of Fe3O4 microspheres to dissolve it, ultrasonic at 900 W for 3 h, then add 1.19 g of NiCl2·6H2O, ultrasonic at 900 W for 2 h to make it completely dissolved; then under the condition of non-magnetic stirring (stirring paddle), add 25 mL of aqueous hydrazine solution (the content of aqueous hydrazine is 3 wt%, containing 1 g of NaOH) to the above solution, and stir vigorously at a speed of 600 rpm for 10 min; the obtained mixed solution is transferred to a 100 mL high-pressure reactor, and the temperature is set to 393 K in a blast drying oven for 1 h. The obtained product is washed with water and ethanol, and the precipitate after washing is collected by freeze-drying method. The residual solvent of the freeze-dried product is removed, and the final product is a black solid powder, which is Fe3O4 microspheres loaded with Ni.

[0127] S3, Preparation of Ni / Fe3O4@MIL with core-shell structure

[0128] Take 0.16 g of Fe3O4 microspheres loaded with Ni and 0.8 g of H3BTC and dissolve them in 50 mL of DMF, ultrasonic at 900 W for 1 h to form a uniformly dispersed solution, then transfer the solution to a 100 mL high-pressure reactor, set the hydrothermal reaction temperature to 423 K, and put it into a blast drying oven for hydrothermal reaction for 24 h. After the reaction time reaches, take out the reactor from the drying oven and cool it to room temperature naturally. The obtained product solution is first washed with water by centrifugation for three times, then washed with anhydrous ethanol by centrifugation for three times, and finally freeze-dried by a vacuum freeze-drying machine to obtain the target product, which is Ni / Fe3O4@MIL with core-shell structure.

[0129] S4, Preparation of MgH2-Ni / Fe3O4@MIL composite hydrogen storage material

[0130] According to the mass ratio of 9:1, take the metal Mg powder and the Ni / Fe3O4@MIL with core-shell structure, and after hydrogenation combustion and high-energy ball milling, obtain the MgH2-Ni / Fe3O4@MIL composite hydrogen storage material.

[0131] In the process of hydrogenation combustion, the pressure of hydrogen is 4.0 MPa, the heating rate is 2 K / min, the holding temperature is 673 K, and the holding time is 40 h. In the process of ball milling, the rotation speed of ball milling is 500 rpm, the ball milling time is 15 min, the interval is 5 min, and the ball-to-material ratio is 30:1.

[0132] Example 2

[0133] The embodiment provides a magnesium-based hydrogen storage material based on a core-shell structure, and the magnesium-based hydrogen storage material based on the core-shell structure is prepared through the following steps.

[0134] S1, preparation of Fe3O4 microspheres

[0135] 3.0g of FeCl3·6H2O is dissolved in 80mL of ethylene glycol, then 2.0g of anhydrous sodium acetate is added to the solution, and the solution is stirred at a speed of 500rpm by using a magnetic stirrer for 0.6h to form a uniform yellow solution; then the solution is poured into a 100mL stainless steel reaction kettle lined with polytetrafluoroethylene, and the reaction kettle is transferred to a blast drying oven, the reaction temperature is set to 463K, and the reaction time is set to 9h; after the reaction is completed, the reaction kettle is taken out of the drying oven and naturally cooled to room temperature; after the liquid is poured out, the product is washed by centrifugation with water three times and then washed by centrifugation with anhydrous ethanol three times; after the washing is completed, the product is dried by using a vacuum drying oven, the temperature is 343K, and finally a black powder, namely the Fe3O4 microspheres, is obtained.

[0136] S2, preparation of Ni-loaded Fe3O4 microspheres

[0137] 60mL of ethylene glycol is taken, 0.8g of Fe3O4 microspheres is added to dissolve the Fe3O4 microspheres, the solution is ultrasonically treated at a power of 800W for 3.5h, then 1.5g of NiCl2·6H2O is added and ultrasonically treated at a power of 800W for 1.5h to completely dissolve the NiCl2·6H2O; then 30mL of a water-containing hydrazine solution (the content of the water-containing hydrazine is 4wt%, and 1g of NaOH is contained) is added to the solution under the condition that a non-magnetic (stirring paddle) is not stirred, and the solution is stirred at a speed of 500rpm for 15min; the obtained mixed solution is transferred into a 100mL high-pressure reaction kettle, the temperature is set to 403K in a blast drying oven, and the reaction is performed for 40min; the obtained product is washed by using water and ethanol and magnetically adsorbed, the precipitate after washing is collected by using a refrigerated vacuum drying device, the residual solvent of the freeze-dried product is removed, and finally a black solid powder, namely the Ni-loaded Fe3O4 microspheres, is obtained.

[0138] S3, preparation of Ni / Fe3O4@MIL with a core-shell structure

[0139] 0.1g of the Ni-loaded Fe3O4 microspheres and 0.5g of H3BTC are dissolved in 60mL of DMF, the solution is ultrasonically treated at a power of 800W for 2h to form a uniformly dispersed solution, then the solution is transferred into a 100mL high-pressure reaction kettle, the hydrothermal reaction temperature is set to 433K, the kettle is put into a blast drying oven, and the hydrothermal reaction is performed for 18h; after the reaction time reaches, the reaction kettle is taken out of the drying oven and naturally cooled to room temperature; the obtained product solution is washed by centrifugation with water three times and then washed by centrifugation with anhydrous ethanol three times; after the washing is completed, the product is freeze-dried by using a vacuum freeze-drying machine, and finally the target product, namely the Ni / Fe3O4@MIL with a core-shell structure, is obtained.

[0140] S4, Preparation of MgH2-Ni / Fe3O4@MIL composite hydrogen storage material

[0141] Metal Mg powder and the core-shell structure Ni / Fe3O4@MIL are mixed in a mass ratio of 9:1, and after hydrogenation combustion and high-energy ball milling, MgH2-Ni / Fe3O4@MIL composite hydrogen storage material is obtained;

[0142] In the process of hydrogenation combustion, the pressure of hydrogen is 3.5 MPa, the heating rate is 3 K / min, the holding temperature is 648 K, and the holding time is 30 h; in the process of ball milling, the rotation speed of ball milling is 300 rpm, the ball milling time is 10 min, the interval is 8 min, and the ball-to-material ratio is 20:1.

[0143] Example 3

[0144] The embodiment provides a magnesium-based hydrogen storage material based on a core-shell structure, which is prepared by the following steps:

[0145] S1, Preparation of Fe3O4 microspheres

[0146] Dissolve 4.0 g of FeCl3·6H2O in 60 mL of ethylene glycol, then add 3.0 g of anhydrous sodium acetate to the above solution, stir at a rotation speed of 400 rpm with a magnetic stirrer for 20 min to form a uniform yellow solution; then pour the solution into a 100 mL stainless steel reaction kettle lined with polytetrafluoroethylene, transfer it to a forced air drying oven, set the reaction temperature to 483 K, and the reaction time to 7 h. After the reaction is completed, remove the reaction kettle from the drying oven and cool it to room temperature naturally. After pouring out the liquid, first wash it with water three times by centrifugation, then wash it with anhydrous ethanol three times by centrifugation, and finally dry the product in a vacuum drying oven at a temperature of 323 K. Finally, a black powder is obtained, which is Fe3O4 microspheres.

[0147] S2, Preparation of Ni-loaded Fe3O4 microspheres

[0148] Take 40 mL of ethylene glycol, add 1.0 g of Fe3O4 microspheres to dissolve it, ultrasonic at 700 W for 2.5 h, then add 1.5 g of NiCl2·6H2O, ultrasonic at 700 W for 1.5 h to make it completely dissolved; then under the condition of non-magnetic stirring (stirring paddle), 20 mL of aqueous hydrazine solution (aqueous hydrazine content is 5wt%, containing 1 g of NaOH) is added to the above solution, and after stirring at 400 rpm for 5 min; the obtained mixed solution is transferred to a 100 mL high-pressure reactor, and the temperature is set to 383 K in the air drying oven for 1.5 h. The obtained product is washed with water and ethanol, and the precipitate after washing is collected by freeze-drying method. The residual solvent of the freeze-dried product is removed, and the final product is a black solid powder, which is Ni-loaded Fe3O4 microspheres.

[0149] S3, Preparation of Ni / Fe3O4@MIL with core-shell structure

[0150] Take 0.2 g of Ni-loaded Fe3O4 microspheres and 1.0 g of H3BTC and dissolve them in 40 mL of DMF, ultrasonic at 700 W for 40 min to form a uniformly dispersed solution, then transfer the solution to a 100 mL high-pressure reactor, set the hydrothermal reaction temperature to 413 K, and put it into the air drying oven for hydrothermal reaction for 30 h. After the reaction time reaches, take the reactor out of the drying oven and cool it to room temperature naturally. The obtained product solution is first washed with water by centrifugation three times, then washed with anhydrous ethanol by centrifugation three times, and finally freeze-dried by vacuum freeze-drying machine to obtain the target product, which is Ni / Fe3O4@MIL with core-shell structure.

[0151] S4, Preparation of MgH2-Ni / Fe3O4@MIL composite hydrogen storage material

[0152] Metallic Mg powder and the Ni / Fe3O4@MIL with core-shell structure are mixed in a mass ratio of 9:1, and after hydrogenation combustion and high-energy ball milling, MgH2-Ni / Fe3O4@MIL composite hydrogen storage material is obtained.

[0153] In the process of hydrogenation combustion, the pressure of hydrogen is 3.8 MPa, the heating rate is 5 K / min, the holding temperature is 623 K, and the holding time is 35 h. In the process of ball milling, the rotation speed of ball milling is 400 rpm, the ball milling time is 20 min, the interval is 10 min, and the ball-to-material ratio is 40:1.

[0154] Example 4

[0155] The embodiment provides a magnesium-based hydrogen storage material based on a core-shell structure, which is different from the embodiment 1 only in that the metal Mg powder and the core-shell structure Ni / Fe3O4@MIL are mixed in S4 according to a mass ratio of 12:1, and other steps are completely consistent with the embodiment 1.

[0156] Embodiment 5

[0157] The embodiment provides a magnesium-based hydrogen storage material based on a core-shell structure, which is different from the embodiment 1 only in that the metal Mg powder and the core-shell structure Ni / Fe3O4@MIL are mixed in S4 according to a mass ratio of 6:1, and other steps are completely consistent with the embodiment 1.

[0158] Comparative example 1

[0159] The comparative example provides a MgH2 hydrogen storage material, which is prepared by the following steps: after hydrogenation combustion and high-energy ball milling of metal Mg powder, the MgH2 hydrogen storage material is obtained;

[0160] In the hydrogenation combustion process, the pressure of hydrogen is 4.0 MPa, the heating rate is 2 K / min, the holding temperature is 673 K, and the holding time is 40 h; in the ball milling process, the rotation speed of ball milling is 500 rpm, the ball milling time is 15 min, the interval is 15 min, and the ball-to-material ratio is 30:1.

[0161] Comparative example 2

[0162] The comparative example provides a hydrogen storage material, which is prepared by the following steps:

[0163] S1, preparation of Fe3O4 microspheres

[0164] 3.46g of FeCl3·6H2O is dissolved in 70mL of ethylene glycol, then 2.66g of anhydrous sodium acetate is added to the above solution, and the solution is stirred at a rotation speed of 600rpm by using a magnetic stirrer for 0.5h to form a uniform yellow solution; then the solution is poured into a 100mL stainless steel reaction kettle lined with polytetrafluoroethylene, and is transferred to a blast drying oven, and the reaction temperature is set to 473K and the reaction time is set to 8h; after the reaction is completed, the reaction kettle is taken out from the drying oven and naturally cooled to room temperature, and then the liquid is poured out and washed with water for three times by using a centrifugal machine, and then washed with anhydrous ethanol for three times by using a centrifugal machine, and after completion, the product is dried by using a vacuum drying oven, and the temperature is 333K; finally, a black powder is obtained, which is Fe3O4 microspheres.

[0165] S2, preparation of a composite hydrogen storage material

[0166] The metal Mg powder and the Fe3O4 microspheres are mixed in a mass ratio of 9:1, and after hydrogenation combustion and high-energy ball milling, a composite hydrogen storage material is obtained.

[0167] In the hydrogenation combustion process, the pressure of hydrogen is 4.0 MPa, the heating rate is 2 K / min, the holding temperature is 673 K, and the holding time is 40 h; in the ball milling process, the ball milling speed is 500 rpm, the ball milling time is 15 min, the interval is 15 min, and the ball-to-material ratio is 30:1.

[0168] Comparative Example 3

[0169] The present comparative example provides a hydrogen storage material prepared by the following steps:

[0170] S1, Preparation of Fe3O4 microspheres

[0171] Dissolve 3.46 g of FeCl3·6H2O in 70 mL of ethylene glycol, then add 2.66 g of anhydrous sodium acetate to the above solution, and stir at a speed of 600 rpm with a magnetic stirrer for 0.5 h to form a uniform yellow solution; then pour the solution into a 100 mL stainless steel reaction kettle lined with polytetrafluoroethylene, and transfer it to a forced air drying oven, set the reaction temperature to 473 K, and the reaction time to 8 h; after the reaction is completed, remove the reaction kettle from the drying oven and cool it to room temperature naturally, pour out the liquid, then wash it with water three times by centrifugation, and then wash it with anhydrous ethanol three times by centrifugation, and finally dry the product in a vacuum drying oven at a temperature of 333 K, and finally obtain a black powder, which is Fe3O4 microspheres.

[0172] S2, Preparation of Fe3O4 microspheres loaded with Ni

[0173] Dissolve 50 mL of ethylene glycol, add 0.45 g of Fe3O4 microspheres, and ultrasonicate for 3 h at a power of 900 W, then add 1.19 g of NiCl2·6H2O, and ultrasonicate for another 2 h at a power of 900 W to completely dissolve it; then add 25 mL of aqueous hydrazine solution (the content of aqueous hydrazine is 3 wt%, and it contains 1 g of NaOH) to the above solution under the condition of non-magnetic (stirring paddle) stirring, and stir vigorously at a speed of 600 rpm for 10 min; then transfer the obtained mixed solution into a 100 mL high-pressure reaction kettle, and set the temperature to 393 K in a forced air drying oven for 1 h, and finally obtain a black solid powder, which is Fe3O4 microspheres loaded with Ni, after washing the product with water and ethanol, and collecting the precipitate after washing by freeze-drying, and removing the residual solvent of the freeze-dried product.

[0174] S3, Preparation of a composite hydrogen storage material

[0175] The metal Mg powder and the Ni-loaded Fe3O4 microspheres are mixed in a mass ratio of 9:1, and after hydrogenation combustion and high-energy ball milling, a composite hydrogen storage material is obtained.

[0176] In the hydrogenation combustion process, the pressure of hydrogen is 4.0 MPa, the heating rate is 2 K / min, the holding temperature is 673 K, and the holding time is 40 h; in the ball milling process, the ball milling speed is 500 rpm, the ball milling time is 15 min, the interval is 15 min, and the ball-to-material ratio is 30:1.

[0177] Comparative Example 4

[0178] This comparative example provides a magnesium-based hydrogen storage material based on a core-shell structure, which is prepared by the following steps:

[0179] S1, Preparation of Fe3O4 microspheres

[0180] Take 3.46 g of FeCl3·6H2O and dissolve it in 70 mL of ethylene glycol, then add 2.66 g of anhydrous sodium acetate to the above solution, stir it with a magnetic stirrer at a speed of 600 rpm for 0.5 h to form a uniform yellow solution; then pour the solution into a 100 mL stainless steel reaction kettle lined with polytetrafluoroethylene, and transfer it to a forced air drying oven, set the reaction temperature to 473 K, and the reaction time to 8 h. After the reaction is completed, remove the reaction kettle from the drying oven and cool it to room temperature naturally. Pour out the liquid and first wash it with water three times by centrifugation, then wash it with anhydrous ethanol three times by centrifugation. After completion, dry the product in a vacuum drying oven at a temperature of 333 K. Finally, a black powder is obtained, which is Fe3O4 microspheres.

[0181] S2, Preparation of Fe3O4@MIL core-shell structure

[0182] Take 0.16 g of Fe3O4 microspheres and 0.8 g of H3BTC and dissolve them in 50 mL of DMF, and ultrasonicate them for 1 h at a power of 900 W to form a uniformly dispersed solution. Then transfer the solution to a 100 mL high-pressure reaction kettle, set the hydrothermal reaction temperature to 423 K, and place it in a forced air drying oven for hydrothermal reaction for 24 h. After the reaction time is reached, remove the reaction kettle from the drying oven and cool it to room temperature naturally. The obtained product solution is first washed with water three times by centrifugation, then washed with anhydrous ethanol three times by centrifugation. After completion, freeze-dry the product using a vacuum freeze-drying machine to obtain the target product, which is a core-shell structure of Fe3O4@MIL core-shell structure.

[0183] S3, Preparation of MgH2-Fe3O4@MIL composite hydrogen storage material

[0184] The metal Mg powder and the Fe3O4@MIL of the core-shell structure are mixed according to a mass ratio of 9:1, and the MgH2-Fe3O4@MIL composite hydrogen storage material is obtained after hydrogenation combustion and high-energy ball milling.

[0185] In the hydrogenation combustion process, the pressure of hydrogen is 4.0 MPa, the heating rate is 2 K / min, the holding temperature is 673 K, and the holding time is 40 h; in the ball milling process, the rotation speed of ball milling is 500 rpm, the ball milling time is 15 min, the interval is 15 min, and the ball-to-material ratio is 30:1.

[0186] Comparative Example 5

[0187] The present comparative example provides a composite hydrogen storage material prepared by the following steps:

[0188] S1, preparation of Fe3O4 microspheres

[0189] 3.46 g of FeCl3·6H2O is dissolved in 70 mL of ethylene glycol, then 2.66 g of anhydrous sodium acetate is added to the above solution, and stirred at a rotation speed of 600 rpm with a magnetic stirrer for 0.5 h to form a uniform yellow solution; then the solution is poured into a 100 mL stainless steel reaction kettle lined with polytetrafluoroethylene, and transferred to a blast drying oven, and the reaction temperature is set to 473 K and the reaction time is 8 h; after the reaction is completed, the reaction kettle is taken out from the drying oven and naturally cooled to room temperature, and then washed with water three times by centrifugation, and then washed with anhydrous ethanol three times by centrifugation, and then dried in a vacuum drying oven at a temperature of 333 K, and finally a black powder is obtained, which is Fe3O4 microspheres.

[0190] S2, preparation of mixed powder

[0191] Fe3O4 microspheres, metal Ni powder and H3BTC are mixed in a mass ratio of 5:4:2, stirred at a rotation speed of 400 rpm for 30 min, and a mixed powder is obtained.

[0192] S3, preparation of composite hydrogen storage material

[0193] The metal Mg powder and the mixed powder are mixed according to a mass ratio of 9:1, and the composite hydrogen storage material is obtained after hydrogenation combustion and high-energy ball milling;

[0194] In the hydrogenation combustion process, the pressure of hydrogen is 4.0 MPa, the heating rate is 2 K / min, the holding temperature is 673 K, and the holding time is 40 h; in the ball milling process, the rotation speed of ball milling is 500 rpm, the ball milling time is 15 min, the interval is 15 min, and the ball-to-material ratio is 30:1.

[0195] Test Example

[0196] Test sample: magnesium-based hydrogen storage material based on core-shell structure provided by Examples 1-5, hydrogen storage material provided by Comparative Examples 1-5;

[0197] Test method:

[0198] (1) Hydrogen absorption test: the hydrogen absorption amount of each sample at different times was tested at 423 K and 373 K, respectively, and the hydrogen absorption curve of the hydrogen storage material provided by Example 1 and Comparative Example 1 was plotted;

[0199] (2) Hydrogen desorption test: the hydrogen desorption amount of each sample at different times was tested at 623 K and 598 K, respectively, and the hydrogen desorption curve of the hydrogen storage material provided by Example 1 and Comparative Example 1 was plotted;

[0200] The specific test results are shown in Tables 1-4 and Figures 1-4:

[0201] Table 1

[0202] Table 2

[0203] Table 3

[0204] Table 4

[0205] As shown in Tables 1-4, the hydrogen absorption amount of the magnesium-based hydrogen storage material based on core-shell structure provided by the present disclosure can reach 5.420 wt% or more at 423 K, and 4.167 wt% or more at 373 K; and the hydrogen desorption amount of the magnesium-based hydrogen storage material based on core-shell structure provided by the present disclosure can reach 5.022 wt% or more at 623 K, and 3.498 wt% or more at 598 K. Therefore, it is illustrated that in the hydrogen absorption and desorption reaction process, the unique core-shell structure of Ni / Fe3O4@MIL not only provides more reaction sites, but also prevents particle agglomeration, maintains high catalytic stability, and has great advantages in reducing the hydrogen desorption temperature of magnesium-based hydrogen storage materials. Industrial applicability

[0206] The magnesium-based hydrogen storage material based on core-shell structure and the preparation method thereof provided by the present disclosure are not limited by the types and compositions of raw materials, have low raw material cost, are simple and easy to obtain, have a simple process flow, and the method is suitable for large-scale industrialization. The prepared magnesium-based hydrogen storage material has excellent hydrogen storage performance and can still maintain high hydrogen absorption capacity at low temperature. The magnesium-based hydrogen storage material based on core-shell structure is applied in low-temperature hydrogen storage.

Claims

1. A magnesium-based hydrogen storage material based on a core-shell structure, characterized in that, The core-shell structure-based magnesium-based hydrogen storage material includes the hydrogenation combustion products of Ni / Fe3O4@MIL and MgH2; The Ni / Fe3O4@MIL is a material with a core-shell structure. The core of the Ni / Fe3O4@MIL includes Ni-supported Fe3O4 microspheres, and the shell of the Ni / Fe3O4@MIL includes organic ligands.

2. The magnesium-based hydrogen storage material based on a core-shell structure according to claim 1, characterized in that, The mass ratio of the hydrogenation combustion products of Ni / Fe3O4@MIL to MgH2 is (1-2):(5-15).

3. The magnesium-based hydrogen storage material based on a core-shell structure according to claim 1 or 2, characterized in that, In the Ni / Fe3O4@MIL, the particle size of the core is 350-400 nm; the thickness of the outer shell is 50-100 nm.

4. The magnesium-based hydrogen storage material based on a core-shell structure according to claim 1 or 2, characterized in that, The organic ligand is pyromellitic acid.

5. A method for preparing a magnesium-based hydrogen storage material with a core-shell structure according to any one of claims 1 to 4, characterized in that, The preparation method includes the following steps: (1) After mixing iron salt, alkaline regulator and alcohol solvent, a first hydrothermal reaction was carried out to obtain Fe3O4 microspheres; (2) After mixing Fe3O4 microspheres, nickel salt and alcohol solvent, it is mixed with hydrazine hydrate solution and stirred, and then a second hydrothermal reaction is carried out to obtain Ni-supported Fe3O4 microspheres. (3) After mixing Ni-supported Fe3O4 microspheres, pyromellitic acid and solvent, a third hydrothermal reaction was carried out to obtain Ni / Fe3O4@MIL with a core-shell structure; (4) Ni / Fe3O4@MIL and metallic Mg are mixed, and after hydrogenation combustion and ball milling, the magnesium-based hydrogen storage material based on the core-shell structure is obtained.

6. The method for preparing magnesium-based hydrogen storage material with a core-shell structure according to claim 5, characterized in that, In step (1), the mass ratio of the iron salt, alkali and alcohol solvent is (3-4):(2-3):(75-80).

7. The method for preparing magnesium-based hydrogen storage material with a core-shell structure according to claim 5 or 6, characterized in that, In step (1), the iron salt is selected from any one or a combination of at least two of ferric chloride, ferric nitrate, ferric sulfate, ferric acetate, or ferric citrate.

8. The method for preparing magnesium-based hydrogen storage materials with a core-shell structure according to claim 5 or 6, characterized in that, In step (1), the alkalinity regulator is selected from any one or a combination of at least two of sodium formate, sodium acetate, sodium propionate, potassium formate, potassium acetate, ammonium formate or ammonium acetate.

9. The method for preparing magnesium-based hydrogen storage materials with a core-shell structure according to claim 5 or 6, characterized in that, In steps (1) and (2), each alcohol solvent is independently selected from any one or a combination of at least two of ethylene glycol, propylene glycol, glycerol or diethylene glycol.

10. The method for preparing magnesium-based hydrogen storage material with a core-shell structure according to claim 5, characterized in that, In step (1), the temperature of the first hydrothermal reaction is 423-523K, and the time of the first hydrothermal reaction is 5-10h.

11. The method for preparing magnesium-based hydrogen storage material with a core-shell structure according to claim 5, characterized in that, In step (2), the mass ratio of Fe3O4 microspheres, nickel salt, alcohol solvent, and hydrated hydrazine solution is (0.2-1):(1-2):(50-60):(20-30).

12. The method for preparing magnesium-based hydrogen storage materials with a core-shell structure according to claim 5 or 11, characterized in that, In step (2), the nickel salt is selected from any one or a combination of at least two of nickel chloride, nickel nitrate, nickel sulfate, nickel acetate or nickel citrate.

13. The method for preparing magnesium-based hydrogen storage materials with a core-shell structure according to claim 5 or 11, characterized in that, In step (2), the content of hydrazine hydrate in the hydrated hydrazine solution is 3-5 wt%.

14. The method for preparing magnesium-based hydrogen storage material with a core-shell structure according to claim 13, characterized in that, The hydrated hydrazine solution also includes 3-5 wt% alkaline substances; The alkaline substance is selected from sodium hydroxide and / or potassium hydroxide.

15. The method for preparing magnesium-based hydrogen storage material with a core-shell structure according to claim 5, characterized in that, In step (2), the temperature of the second hydrothermal reaction is 323-393 K, and the time of the second hydrothermal reaction is 24-48 h.

16. The method for preparing magnesium-based hydrogen storage material with a core-shell structure according to claim 5, characterized in that, In step (3), the mass ratio of the Ni-supported Fe3O4 microspheres, pyromellitic acid, and solvent is (0.1-0.2):(0.5-1):(40-50).

17. The method for preparing magnesium-based hydrogen storage material with a core-shell structure according to claim 5, characterized in that, In step (3), the temperature of the third hydrothermal reaction is 323-423 K, and the time of the third hydrothermal reaction is 24-48 h.

18. The method for preparing magnesium-based hydrogen storage material with a core-shell structure according to claim 5, characterized in that, In step (4), the mass ratio of Ni / Fe3O4@MIL to metallic Mg is 1:(5-15).

19. The method for preparing magnesium-based hydrogen storage material with a core-shell structure according to claim 5, characterized in that, In step (4), during the hydrogenation combustion process, the hydrogen pressure is 3.5-4.0 MPa, the heating rate is 2-5 K / min, the holding temperature is 623-673 K, and the holding time is 30-40 h. In step (4), during the ball milling process, the ball milling speed is 300-500 rpm, the ball milling time is 10-20 min, the interval is 5-10 min, and the ball-to-material ratio is (20-40):

1.

20. The application of a magnesium-based hydrogen storage material with a core-shell structure according to any one of claims 1 to 4 in cryogenic hydrogen storage.

Images