TM-Mg2Ni / MgH2 composite hydrogen storage material and preparation method thereof

Abstract

The invention discloses a preparation method of a TM-Mg2Ni / MgH2 composite hydrogen storage material, which comprises the following steps: step S1, fully dissolving and uniformly mixing a front transition metal salt and nickel chloride in deionized water, then adding sodium borohydride, stirring at room temperature, and then collecting a precipitate; s2, sequentially carrying out washing, centrifugation and vacuum drying on the precipitate, then transferring the precipitate into a tubular furnace, and carrying out heat treatment in a flowing Ar / H2 atmosphere at 300-700 DEG C for 8-16 hours; s3, after heat treatment is completed, natural cooling is conducted to the room temperature, then a sample is collected and transferred into a glove box filled with Ar to obtain a TM-Ni precursor, and the TM atom ratio content in the TM-Ni precursor is 1.00-25.00 at.%; step S4, carrying out ball milling on MgH2 and the obtained TM-Ni precursor in an argon atmosphere so as to obtain TM-Mg2Ni / MgH2; compared with the prior art, the catalyst has good hydrogen absorption and desorption performance and hydrogen absorption and desorption cycling stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hydrogen storage materials, in particular to a TM-Mg2Ni / MgH2 composite hydrogen storage material and a preparation method thereof. BACKGROUND

[0002] As a green energy, hydrogen energy has the characteristics of wide source, clean and carbon-free, flexibility and high efficiency, and its mass energy density is three times that of gasoline, which shows great potential in many application fields. In particular, "green hydrogen" produced by electrolysis of water using renewable energy (such as peak-valley electricity, photovoltaic and wind power) can realize seasonal regulation and cross-regional storage of energy, which greatly promotes the efficient use of renewable energy. However, in the whole hydrogen energy industry chain, the efficient and safe storage and transportation of hydrogen gas is still a bottleneck restricting its large-scale application, resulting in the coexistence of overcapacity on the production end and insufficient supply on the application end.

[0003] Among the many hydrogen storage methods, solid-state hydrogen storage materials have attracted widespread attention due to their high hydrogen storage capacity, good safety, and abundant resources. Among them, magnesium-based hydrogen storage materials are considered as one of the most promising solid-state hydrogen storage materials due to their high theoretical hydrogen storage capacity of 7.6 wt.%. However, magnesium-based hydrogen storage materials also have inherent defects: first, their hydride reaction enthalpy change is relatively high (about 75 kJ / mol), resulting in strong thermodynamic stability, high hydrogen absorption and desorption operating temperature, and high energy consumption; second, the kinetic performance is poor, the hydrogen dissociation and diffusion process is slow, and there is a lack of efficient catalytic active sites. At present, introducing a catalyst is one of the effective strategies to construct active sites and improve the kinetic performance of magnesium-based hydrogen storage materials, and how to accurately control the interaction between the catalyst and hydrogen species (H2 / H) is the key to achieving efficient catalysis.

[0004] In recent years, transition metal catalysts have shown great potential in hydrogenation / dehydrogenation reactions. In the magnesium-based hydrogen storage system, Mg2Ni phase has been proven to have good catalytic effect due to its unique "hydrogen pump" effect. However, a single Mg2Ni phase cannot simultaneously optimize the two key steps of hydrogen dissociation and hydrogen atom diffusion, limiting the further improvement of its catalytic performance. Therefore, how to synergistically promote the hydrogen dissociation and hydrogen diffusion processes of magnesium-based hydrogen storage materials is a difficult problem that needs to be solved. SUMMARY

[0005] In view of the deficiencies in the prior art, the purpose of the present application is to provide a TM-Mg2Ni / MgH2 composite hydrogen storage material and a preparation method thereof, to solve the problem of how to synergistically promote the hydrogen dissociation and hydrogen diffusion processes of magnesium-based hydrogen storage materials in the prior art.

[0006] To achieve the above objectives, the first aspect of this invention adopts the following technical solution: a method for preparing a TM-Mg2Ni / MgH2 composite hydrogen storage material, comprising the following steps: Step S1: Dissolve the former transition metal salt and nickel chloride thoroughly in deionized water and mix evenly. Then add sodium borohydride, stir at room temperature, and collect the precipitate. Step S2: The precipitate is washed, centrifuged and vacuum dried in sequence, and then transferred to a tube furnace for heat treatment at 300-700℃ for 8-16 h in a flowing Ar / H2 atmosphere. Step S3: After heat treatment, allow the sample to cool naturally to room temperature. Then, collect the sample and transfer it to a glove box filled with Ar to obtain the TM-Ni precursor. The TM atomic ratio in the TM-Ni precursor is 1.00~25.00 at.% Step S4: Ball mill MgH2 and the obtained TM-Ni precursor under an argon atmosphere to obtain TM-Mg2Ni / MgH2.

[0007] Technical principle: Early transition metals exhibit poor reactivity with magnesium (Mg) and do not react chemically after ball milling with MgH2. Conversely, late transition metals like nickel (Ni) have a good affinity for Mg and can react with MgH2 during ball milling to form new phases such as Mg2Ni. Previous studies have found that the reactivity of the TM-Ni precursor with MgH2 is modulated by its TM / Ni atomic ratio. When the TM content is high (e.g., TM:Ni = 1:1), the precursor is inert and does not react with MgH2. Based on this, this invention uses a nickel-rich TM-Ni alloy (TM atomic percentage 1.00-25.00 at.%) as the precursor. Characterization results such as X-ray diffraction (XRD) and X-ray absorption fine structure (XAFS) confirm that this nickel-rich precursor is successfully converted into a TM-doped Mg2Ni (i.e., TM-Mg2Ni) catalyst during ball milling. This structure forms a dual active site composed of TM and Ni, thereby significantly improving the catalytic efficiency of the composite hydrogen storage material.

[0008] Furthermore, the former transition metal salt includes titanium sulfate, sodium vanadate, sodium chromate, sodium molybdate dihydrate, or sodium tungstate dihydrate.

[0009] Furthermore, in step S1, the ratio of the pre-transition metal salt, nickel chloride, sodium borohydride, and deionized water is 0.06-2.00 mmol: 6.00 mmol: 8.00-9.00 mmol: 20-40 mL.

[0010] Furthermore, the washing process in step S2 specifically includes: First, wash the product three times by centrifugation with deionized water at 5000-10000 rpm, then wash it two to four times by centrifugation with anhydrous ethanol at 5000-10000 rpm, with each centrifugation lasting 5-10 minutes.

[0011] Furthermore, the vacuum drying in step S2 specifically involves vacuum drying at 50-80℃ for 1-16 hours.

[0012] Furthermore, in step S2, the flow rate of the Ar / H2 atmosphere is 100-400 mL / min and its temperature is 600℃, and the H2 content in the Ar / H2 atmosphere is 1-10 vol.%.

[0013] Furthermore, the particle size of the TM-Ni precursor in step S3 is 101~534 nm.

[0014] Furthermore, in step S4, the mass ratio of MgH2 to TM-Ni precursor is 80-95 wt.% : 5-20 wt.%.

[0015] Furthermore, in step S4, the ball-to-material ratio during the ball milling process is 10-100:1, and the ball milling is specifically repeated for 8-24 hours in the order of forward ball milling, one pause, reverse ball milling, and two pauses, with the rotation speed of forward and reverse ball milling being 200-800 rpm.

[0016] The second aspect of the present invention adopts the following technical solution: a TM-Mg2Ni / MgH2 composite hydrogen storage material, which is prepared by the preparation method of the TM-Mg2Ni / MgH2 composite hydrogen storage material described in the first aspect of the present invention.

[0017] Compared with the prior art, the present invention has the following beneficial effects: This invention utilizes a TM-Ni precursor to form a TM-Mg2Ni / MgH2 composite hydrogen storage material, which not only facilitates the adsorption and dissociation of hydrogen molecules but also promotes the diffusion of hydrogen atoms, achieving a good match between the hydrogen dissociation and diffusion processes. The prepared composite hydrogen storage material can release up to 6.55 wt.% hydrogen gas in 15 minutes at 300℃ and up to 6.21 wt.% hydrogen gas in 15 minutes at a lower temperature of 250℃, with an activation energy of 96.13 kJ / mol for the hydrogen release reaction. Furthermore, after 50 hydrogen adsorption / desorption cycles, the composite hydrogen storage material can still maintain a hydrogen storage capacity of over 6.1 wt.%. Attached Figure Description

[0018] Figure 1 The graph shows the test results of the cyclic hydrogen absorption and desorption performance of the composite hydrogen storage material prepared in Example 9 at 280°C. Figure 2 The EXAFS spectral and structural fitting results are for the Mo K-edge composite hydrogen storage material prepared in Example 9; Figure 3 The image shows the XRD patterns of the composite hydrogen storage material prepared in Example 9 before and after 50 cycles. Detailed Implementation

[0019] The present invention will be further described in detail below through specific embodiments: Example 1: Preparation of Mg2Ni (9wt.%) / MgH2 S1. First, dissolve 6.0 mmol of nickel chloride in 20 mL of deionized water and stir magnetically. Then, dissolve 8.0 mmol of sodium borohydride in 20 mL of deionized water, and use a dropper to add the prepared sodium borohydride solution to the prepared nickel chloride solution. Continue stirring at room temperature for 30 min.

[0020] S2. First, wash twice with deionized water at 5000 rpm, then wash three times with anhydrous ethanol at 5000 rpm, each time for 5 min. Then, vacuum dry at 50℃ for 8 h. Transfer the dried precipitate to a tube furnace, and introduce an Ar / H2 mixture with a H2 content of 1 vol.% into the tube furnace at a flow rate of 100 ml / min. Then, heat-treat at 400℃ for 1 h. After naturally cooling to room temperature, collect the sample and transfer it to a glove box filled with Ar to obtain the Ni precursor. The particle size of the Ni precursor is 469 nm.

[0021] S3. In a vacuum glove box, MgH2 and Ni precursor are weighed and mixed at a mass ratio of 91:9, with a total mass of 4g. The mixture is then poured into a ball mill jar and milled under an argon atmosphere of 0.2MPa at a ball-to-material ratio of 10:1. The mill is run at 200rpm, first clockwise for 8 minutes, then intermittently for 8 minutes, then counterclockwise for 8 minutes, then intermittently for 8 minutes, for a total effective milling time of 8 hours, to obtain the composite hydrogen storage material Mg2Ni (9wt.%) / MgH2. The steel balls in the ball mill jar consist of 40g of small stainless steel balls with a diameter of 5mm, 20g of medium stainless steel balls with a diameter of 8mm, and 20g of large stainless steel balls with a diameter of 10mm.

[0022] Example 2: Preparation of Ti-Mg2Ni(5wt.%) / MgH2 S1. First, dissolve 6.0 mmol of nickel chloride and 0.06 mmol of a pre-transition metal salt (titanium sulfate) in 20 mL of deionized water and stir magnetically. Then, dissolve 8.0 mmol of sodium borohydride in 20 mL of deionized water, and use a dropper to add the prepared sodium borohydride solution to the prepared pre-transition metal salt and nickel chloride solution. Continue stirring at room temperature for 30 min.

[0023] S2. First, wash twice with deionized water at 5000 rpm, then wash three times with anhydrous ethanol at 5000 rpm, each time for 5 min. Then, vacuum dry at 50℃ for 8 h. Transfer the dried precipitate to a tube furnace, and introduce a 1 vol.% Ar / H2 mixture into the furnace at a flow rate of 100 ml / min. Heat treat at 400℃ for 1 h. After natural cooling to room temperature, collect the sample and transfer it to a glove box filled with Ar to obtain the Ti-Ni precursor. The particle size of the Ti-Ni precursor is 534 nm.

[0024] S3. In a vacuum glove box, MgH2 and Ti-Ni precursor are weighed and mixed at a mass ratio of 95:5, with a total mass of 4g. The mixture is then poured into a ball mill jar and milled at a ball-to-material ratio of 10:1 under an argon atmosphere of 0.2MPa. The mill is run at 200rpm, first for 8 minutes in the forward direction with an 8-minute interval, then in the reverse direction for 8 minutes with an 8-minute interval, for a total effective milling time of 8 hours, to obtain the composite hydrogen storage material (Ti-Mg2Ni (5wt.%) / MgH2). The ball mill jar contains 40g of small stainless steel balls with a diameter of 5mm, 20g of medium stainless steel balls with a diameter of 8mm, and 20g of large stainless steel balls with a diameter of 10mm.

[0025] Example 3: Preparation of Ti-Mg2Ni (20wt.%) / MgH2 S1. First, dissolve 6.0 mmol of nickel chloride and 2.00 mmol of a pre-transition metal salt (titanium sulfate) in 40 mL of deionized water and stir magnetically. Then, dissolve 9.0 mmol of sodium borohydride in 40 mL of deionized water and add the prepared sodium borohydride solution dropwise into the prepared pre-transition metal salt and nickel chloride solution using a dropper. Continue stirring at room temperature for 30 min.

[0026] S2. First, wash twice with deionized water at 10,000 rpm, then wash three times with anhydrous ethanol at 10,000 rpm, each time for 10 min. Then, vacuum dry at 80℃ for 16 h. Transfer the dried precipitate to a tube furnace, and introduce a 10 vol.% Ar / H2 mixture into the furnace at a flow rate of 400 ml / min. Then, heat-treat at 700℃ for 1 h. After natural cooling to room temperature, collect the sample and transfer it to a glove box filled with Ar to obtain the Ti-Ni precursor. The particle size of the Ti-Ni precursor is 465 nm.

[0027] S3. In a vacuum glove box, MgH2 and Ti-Ni precursor are weighed and mixed at a mass ratio of 80:20, with a total mass of 4g. The mixture is then poured into a ball mill jar and milled at a ball-to-material ratio of 10:1 under an argon atmosphere of 0.2MPa. The mill is run at 800rpm, first clockwise for 12 minutes, then intermittently for 12 minutes, then counterclockwise for 12 minutes, then intermittently for 10 minutes. The effective milling time is 12 hours, yielding a composite hydrogen storage material (Ti-Mg2Ni (20wt.%) / MgH2). The ball mill jar contains 40g of small stainless steel balls (5mm diameter), 20g of medium stainless steel balls (8mm diameter), and 20g of large stainless steel balls (10mm diameter).

[0028] Example 4: Preparation of Ti-Mg2Ni (9wt.%) / MgH2 S1. First, dissolve 6 mmol of nickel chloride and 0.66 mmol of a pre-transition metal salt (titanium sulfate) in 30 mL of deionized water and stir magnetically. Then, dissolve 8 mmol of sodium borohydride in 20 mL of deionized water and add the prepared sodium borohydride solution dropwise into the prepared pre-transition metal salt and nickel chloride solution using a dropper. Continue stirring at room temperature for 30 min.

[0029] S2. First, wash the sample three times with deionized water at 10,000 rpm, then wash it three times with anhydrous ethanol at 10,000 rpm, each time for 10 min. Then, dry the sample under vacuum at 60℃ for 12 h. Transfer the dried precipitate to a tube furnace, and introduce a 5 vol.% Ar / H2 mixture into the furnace at a flow rate of 300 ml / min. Then, heat-treat the sample at 500℃ for 12 h. After naturally cooling to room temperature, collect the sample and transfer it to a glove box filled with Ar to obtain the Ti-Ni precursor. The particle size of the Ti-Ni precursor is 420 nm.

[0030] S3. In a vacuum glove box, MgH2 and Ti-Ni precursor are weighed and mixed at a mass ratio of 91:9, with a total mass of 4g. The mixture is then poured into a ball mill jar and milled at a ball-to-material ratio of 10:1 under an argon atmosphere of 0.2MPa. The mill is run at 800rpm, first for 10 minutes in the forward direction with a 10-minute interval, then in the reverse direction with a 10-minute interval, for a total effective milling time of 24 hours, to obtain the composite hydrogen storage material (Ti-Mg2Ni (9wt.%) / MgH2). The ball mill jar contains 40g of small stainless steel balls with a diameter of 5mm, 20g of medium stainless steel balls with a diameter of 8mm, and 20g of large stainless steel balls with a diameter of 10mm.

[0031] Example 5: Preparation of Zr-Mg2Ni (9wt.%) / MgH2 S1. First, dissolve 6 mmol of nickel chloride and 0.66 mmol of a pre-transition metal salt (zirconium sulfate) in 30 mL of deionized water and stir magnetically. Then, dissolve 8 mmol of sodium borohydride in 20 mL of deionized water and add the prepared sodium borohydride solution dropwise into the prepared pre-transition metal salt and nickel chloride solution using a dropper. Continue stirring at room temperature for 30 min.

[0032] S2. First, wash the sample three times with deionized water at 10,000 rpm, then wash it three times with anhydrous ethanol at 10,000 rpm, each time for 10 min. Then, dry the sample under vacuum at 60℃ for 12 h. Transfer the dried precipitate to a tube furnace, and introduce a 5 vol.% Ar / H2 mixture into the furnace at a flow rate of 300 ml / min. Then, heat-treat the sample at 500℃ for 12 h. After naturally cooling to room temperature, collect the sample and transfer it to a glove box filled with Ar to obtain the Zr-Ni precursor. The particle size of the Zr-Ni precursor is 437 nm.

[0033] S3. In a vacuum glove box, MgH2 and Zr-Ni precursor are weighed and mixed at a mass ratio of 91:9, with a total mass of 4g. The mixture is then poured into a ball mill jar and milled at a ball-to-material ratio of 10:1 under an argon atmosphere of 0.2MPa. The mill is run at 800rpm, first clockwise for 10 minutes, then intermittently for 10 minutes, then counterclockwise for 10 minutes, then intermittently for 10 minutes. The effective milling time is 24 hours, yielding a composite hydrogen storage material (Zr-Mg2Ni(9wt.%) / MgH2). The ball mill jar contains 40g of small stainless steel balls (5mm diameter), 20g of medium stainless steel balls (8mm diameter), and 20g of large stainless steel balls (10mm diameter).

[0034] Example 6: Preparation of V-Mg2Ni (9wt.%) / MgH2 S1. First, dissolve 6 mmol of nickel chloride and 0.66 mmol of a pre-transition metal salt (sodium vanadate) in 30 mL of deionized water and stir magnetically. Then, dissolve 8 mmol of sodium borohydride in 20 mL of deionized water and add the prepared sodium borohydride solution dropwise into the prepared pre-transition metal salt and nickel chloride solution using a dropper. Continue stirring at room temperature for 30 min.

[0035] S2. First, wash the sample three times with deionized water at 10,000 rpm, then wash it three times with anhydrous ethanol at 10,000 rpm, each time for 10 min. Then, dry the sample under vacuum at 60℃ for 12 h. Transfer the dried precipitate to a tube furnace, and introduce a 5 vol.% Ar / H2 mixture into the furnace at a flow rate of 300 ml / min. Then, heat-treat the sample at 500℃ for 12 h. After naturally cooling to room temperature, collect the sample and transfer it to a glove box filled with Ar to obtain the V-Ni precursor. The particle size of the V-Ni precursor is 429 nm.

[0036] S3. In a vacuum glove box, MgH2 and V-Ni precursor are weighed and mixed at a mass ratio of 91:9, with a total mass of 4g. The mixture is then poured into a ball mill jar and milled at a ball-to-material ratio of 10:1 under an argon atmosphere of 0.2MPa. The mill is run at 800rpm, first for 10 minutes in the forward direction with a 10-minute interval, then in the reverse direction with a 10-minute interval, for a total effective milling time of 24 hours, to obtain the composite hydrogen storage material (V-Mg2Ni(9wt.%) / MgH2). The ball mill jar contains 40g of small stainless steel balls (5mm diameter), 20g of medium stainless steel balls (8mm diameter), and 20g of large stainless steel balls (10mm diameter).

[0037] Example 7: Preparation of Cr-Mg2Ni (9wt.%) / MgH2 S1. First, dissolve 6 mmol of nickel chloride and 0.66 mmol of a pre-transition metal salt (sodium chromate) in 30 mL of deionized water and stir magnetically. Then, dissolve 8 mmol of sodium borohydride in 20 mL of deionized water and add the prepared sodium borohydride solution dropwise into the prepared pre-transition metal salt and nickel chloride solution using a dropper. Continue stirring at room temperature for 30 min.

[0038] S2. First, wash the sample three times with deionized water at 10,000 rpm, then wash it three times with anhydrous ethanol at 10,000 rpm, each time for 10 min. Then, dry the sample under vacuum at 60℃ for 12 h. Transfer the dried precipitate to a tube furnace, and introduce a 5 vol.% Ar / H2 mixture into the furnace at a flow rate of 300 ml / min. Then, heat-treat the sample at 500℃ for 12 h. After naturally cooling to room temperature, collect the sample and transfer it to a glove box filled with Ar to obtain the Cr-Ni precursor. The particle size of the Cr-Ni precursor is 356 nm.

[0039] S3. In a vacuum glove box, MgH2 and Cr-Ni precursor are weighed and mixed at a mass ratio of 91:9, with a total mass of 4g. The mixture is then poured into a ball mill jar and milled at a ball-to-material ratio of 10:1 under an argon atmosphere of 0.2MPa. The mill is run at 800rpm, first for 10 minutes in the forward direction with a 10-minute interval, then in the reverse direction with a 10-minute interval, for a total effective milling time of 24 hours, to obtain the composite hydrogen storage material (Cr-Mg2Ni(9wt.%) / MgH2). The steel balls in the ball mill jar consist of 40g of small stainless steel balls with a diameter of 5mm, 20g of medium stainless steel balls with a diameter of 8mm, and 20g of large stainless steel balls with a diameter of 10mm.

[0040] Example 8: Preparation of W-Mg2Ni (9wt.%) / MgH2 S1. First, dissolve 6 mmol of nickel chloride and 0.66 mmol of a pre-transition metal salt (sodium tungstate dihydrate) in 30 mL of deionized water and stir magnetically. Then, dissolve 8 mmol of sodium borohydride in 20 mL of deionized water and add the prepared sodium borohydride solution dropwise into the prepared pre-transition metal salt and nickel chloride solution using a dropper. Continue stirring at room temperature for 30 min.

[0041] S2. First, wash the sample three times with deionized water at 10,000 rpm, then wash it three times with anhydrous ethanol at 10,000 rpm, each time for 10 min. Then, dry the sample under vacuum at 60℃ for 12 h. Transfer the dried precipitate to a tube furnace, and introduce a 5 vol.% Ar / H2 mixture into the furnace at a flow rate of 300 ml / min. Then, heat-treat the sample at 500℃ for 12 h. After naturally cooling to room temperature, collect the sample and transfer it to a glove box filled with Ar to obtain the W-Ni precursor. The particle size of the W-Ni precursor is 378 nm.

[0042] S3. In a vacuum glove box, MgH2 and W-Ni precursor are weighed and mixed at a mass ratio of 91:9, with a total mass of 4g. The mixture is then poured into a ball mill jar and milled at a ball-to-material ratio of 10:1 under an argon atmosphere of 0.2MPa. The mill is run at 800rpm, first for 10 minutes in the forward direction with a 10-minute interval, then in the reverse direction with a 10-minute interval, for a total effective milling time of 24 hours, to obtain the composite hydrogen storage material (W-Mg2Ni(9wt.%) / MgH2). The ball mill jar contains 40g of small stainless steel balls (5mm diameter), 20g of medium stainless steel balls (8mm diameter), and 20g of large stainless steel balls (10mm diameter).

[0043] Example 9: Preparation of Mo-Mg2Ni (9wt.%) / MgH2 S1. First, dissolve 6 mmol of nickel chloride and 0.66 mmol of a pre-transition metal salt (sodium molybdate dihydrate) in 30 mL of deionized water and stir magnetically. Then, dissolve 8 mmol of sodium borohydride in 20 mL of deionized water and add the prepared sodium borohydride solution dropwise into the prepared pre-transition metal salt and nickel chloride solution using a dropper. Continue stirring at room temperature for 30 min.

[0044] S2. First, wash the sample three times with deionized water at 10,000 rpm, then wash it three times with anhydrous ethanol at 10,000 rpm, each time for 10 min. Then, dry the sample under vacuum at 60℃ for 12 h. Transfer the dried precipitate to a tube furnace, and introduce a 5 vol.% Ar / H2 mixture into the furnace at a flow rate of 300 ml / min. Then, heat-treat the sample at 500℃ for 12 h. After naturally cooling to room temperature, collect the sample and transfer it to a glove box filled with Ar to obtain the Mo-Ni precursor. The particle size of the Mo-Ni precursor is 168 nm.

[0045] S3. In a vacuum glove box, MgH2 and Mo-Ni precursor are weighed and mixed at a mass ratio of 91:9, with a total mass of 4g. The mixture is then poured into a ball mill jar and milled at a ball-to-material ratio of 10:1 under an argon atmosphere of 0.2MPa. The mill is run at 800rpm, first for 10 minutes in the forward direction with a 10-minute interval, then in the reverse direction with a 10-minute interval, for a total effective milling time of 24 hours, to obtain the composite hydrogen storage material (Mo-Mg2Ni(9wt.%) / MgH2). The steel balls in the ball mill jar consist of 40g of small stainless steel balls with a diameter of 5mm, 20g of medium stainless steel balls with a diameter of 8mm, and 20g of large stainless steel balls with a diameter of 10mm.

[0046] Example 10: Preparation of Mo-Mg2Ni (12wt.%) / MgH2 S1. First, dissolve 6 mmol of nickel chloride and 2.0 mmol of a pre-transition metal salt (sodium molybdate dihydrate) in 30 mL of deionized water and stir magnetically. Then, dissolve 8 mmol of sodium borohydride in 20 mL of deionized water and add the prepared sodium borohydride solution dropwise into the prepared pre-transition metal salt and nickel chloride solution using a dropper. Continue stirring at room temperature for 30 min.

[0047] S2. First, wash the sample three times with deionized water at 10,000 rpm, then wash it three times with anhydrous ethanol at 10,000 rpm, each time for 10 min. Then, dry the sample under vacuum at 60℃ for 12 h. Transfer the dried precipitate to a tube furnace, and introduce a 5 vol.% Ar / H2 mixture into the furnace at a flow rate of 300 ml / min. Then, heat-treat the sample at 500℃ for 12 h. After naturally cooling to room temperature, collect the sample and transfer it to a glove box filled with Ar to obtain the Mo-Ni precursor. The particle size of the Mo-Ni precursor is 101 nm.

[0048] S3. In a vacuum glove box, MgH2 and Mo-Ni precursor are weighed and mixed at a mass ratio of 88:12, with a total mass of 4g. The mixture is then poured into a ball mill jar and milled at a ball-to-material ratio of 10:1 under an argon atmosphere of 0.2MPa. The mill is run at 800rpm, first for 10 minutes in the forward direction with a 10-minute interval, then in the reverse direction with a 10-minute interval, for a total effective milling time of 24 hours, to obtain the composite hydrogen storage material (Mo-Mg2Ni(12wt.%) / MgH2). The ball mill jar contains 40g of small stainless steel balls with a diameter of 5mm, 20g of medium stainless steel balls with a diameter of 8mm, and 20g of large stainless steel balls with a diameter of 10mm.

[0049] 1. Hydrogen absorption and desorption performance The hydrogen desorption performance of the composite hydrogen storage materials prepared in Examples 1-10 was tested using a high-pressure gas adsorption-desorption apparatus at 250-300℃. The results are shown in Table 1.

[0050] Table 1

[0051] 2. Hydrogen absorption / desorption cycle stability test The composite hydrogen storage material prepared in Example 9 was tested using a pressure gas adsorption-desorption apparatus to determine its hydrogen adsorption-desorption cycle stability at 280°C. The results are shown in Table 2 and... Figure 1 As shown.

[0052]

[0053] Table 2 From Table 2 and Figure 1 It can be seen from this: a. Regarding hydrogen absorption performance High initial performance: It exhibits excellent kinetics upon first hydrogen absorption, absorbing 6.0 wt.% within 1 minute and reaching a saturation capacity of 6.5 wt.% within 15 minutes.

[0054] Cyclic stability: There was a slight decrease in capacity at the 10th and 30th cycles (which is common in the early cycles of hydrogen storage materials and may be related to surface passivation or particle remodeling), but there was no sustained decline.

[0055] Capacity recovery and enhancement: By the 50th cycle, the hydrogen absorption capacity at all time points recovered to or even exceeded the level of the first cycle. This indicates that the material has excellent structural reversibility and that continuous "self-activation" may have occurred during cycling, such as further exposure of catalyst sites, interface optimization, or particle refinement, thereby making the hydrogen diffusion channels smoother.

[0056] b. Regarding hydrogen release performance A significant "self-activation" effect was observed: the initial hydrogen release rate was relatively slow (3.4 wt.%) in the first 5 minutes. However, the hydrogen release kinetics improved dramatically with each cycle. By the 50th cycle, the hydrogen release rate in 5 minutes reached an astonishing 5.97 wt.%, a 76% increase compared to the initial release! This directly demonstrates that the dual active sites of TM-Mg2Ni are continuously activated and optimized during cycling.

[0057] Reversible capacity: Starting from the 10th cycle, the hydrogen release capacity at 10 minutes and 15 minutes stabilized at over 6.1 wt.%.

[0058] Capacity retention: Based on 15 minutes, the capacity at the 50th cycle was 6.30 wt.%, which is 96% of the capacity at the first cycle (6.55 wt.%). Considering the possibility of an irreversible phase during the first hydrogen release, the actual reversible capacity retention is close to 100%.

[0059] Performance surpasses initial performance: In fact, in the 50th cycle, 6.24 wt.% of hydrogen was released within 10 minutes, which is more efficient and faster than the performance in the first cycle of 15 minutes.

[0060] Summary: The TM-Mg2Ni / MgH2 composite hydrogen storage material prepared in this invention has the following characteristics: ① Ultra-long cycle life: After 50 cycles, the performance does not degrade and some indicators even increase, proving the extreme stability of the material structure and the success of the design.

[0061] ② Unique kinetic optimization: In particular, the continuous improvement in hydrogen desorption kinetics indicates that the synergistic effect of the TM-Mg2Ni dual active sites is becoming stronger during cycling, effectively reducing the energy barrier for hydrogen diffusion and dissociation.

[0062] ③ Huge potential for practical applications: This "the more you use it, the better it gets" characteristic, along with its high capacity and rapid hydrogen release performance, greatly enhances the application value of this material in practical hydrogen storage systems (such as fuel cell hydrogen sources). The system does not need to worry about frequent material replacements due to short cycle life and can even operate for a long time in an optimized and more stable state.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing a TM-Mg2Ni / MgH2 composite hydrogen storage material, characterized in that, Includes the following steps: Step S1: Dissolve the former transition metal salt and nickel chloride thoroughly in deionized water and mix evenly. Then add sodium borohydride, stir at room temperature, and collect the precipitate. Step S2: The precipitate is washed, centrifuged and vacuum dried in sequence, and then transferred to a tube furnace for heat treatment at 300-700℃ for 8-16 h in a flowing Ar / H2 atmosphere. Step S3: After heat treatment, allow the sample to cool naturally to room temperature. Then, collect the sample and transfer it to a glove box filled with Ar to obtain the TM-Ni precursor. The TM atomic ratio in the TM-Ni precursor is 1.00~25.00 at.% Step S4: Ball mill MgH2 and the obtained TM-Ni precursor under an argon atmosphere to obtain TM-Mg2Ni / MgH2.

2. The preparation method of a TM-Mg2Ni / MgH2 composite hydrogen storage material according to claim 1, characterized in that, The former transition metal salts include titanium sulfate, sodium vanadate, sodium chromate, sodium molybdate dihydrate, or sodium tungstate dihydrate.

3. A method for preparing a TM-Mg2Ni / MgH2 composite hydrogen storage material according to claim 1 or 2, characterized in that, The ratio of the pre-transition metal salt, nickel chloride, sodium borohydride, and deionized water in step S1 is 0.06-2.00 mmol: 6.00 mmol: 8.00-9.00 mmol: 20-40 mL.

4. The preparation method of a TM-Mg2Ni / MgH2 composite hydrogen storage material according to claim 1, characterized in that, The washing process in step S2 specifically involves: First, wash the product by centrifuging it three times with deionized water at a speed of 5000-10000 rpm, and then wash it two to four times with anhydrous ethanol at a speed of 5000-10000 rpm, with each centrifugation time being 5-10 min.

5. The preparation method of a TM-Mg2Ni / MgH2 composite hydrogen storage material according to claim 1, characterized in that, The vacuum drying in step S2 specifically involves vacuum drying at 50-80℃ for 1-16 hours.

6. The preparation method of a TM-Mg2Ni / MgH2 composite hydrogen storage material according to claim 1, characterized in that, In step S2, the flow rate of the Ar / H2 atmosphere is 100-400 mL / min and its temperature is 600℃, and the H2 content in the Ar / H2 atmosphere is 1-10 vol.%.

7. The preparation method of a TM-Mg2Ni / MgH2 composite hydrogen storage material according to claim 1, characterized in that, The particle size of the TM-Ni precursor in step S3 is 101~534 nm.

8. A method for preparing a TM-Mg2Ni / MgH2 composite hydrogen storage material according to claim 1, characterized in that, The mass ratio of MgH2 to TM-Ni precursor in step S4 is 80-95 wt.% : 5-20 wt.%.

9. A method for preparing a TM-Mg2Ni / MgH2 composite hydrogen storage material according to claim 1 or 8, characterized in that, In step S4, the ball-to-material ratio during the ball milling process is 10-100:1, and the ball milling is specifically repeated for 8-24 hours in the order of forward ball milling, one pause, reverse ball milling, and two pauses. The rotation speed of the forward and reverse ball milling is 200-800 rpm.

10. A TM-Mg2Ni / MgH2 composite hydrogen storage material, characterized in that, The TM-Mg2Ni / MgH2 composite hydrogen storage material is prepared by any one of the preparation methods of claims 1-9.

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