CN116786151A - Bimetallic nitride catalyst and preparation method and application thereof - Google Patents

Abstract

The invention discloses a bimetallic nitride catalyst and its preparation method and application. The catalyst uses Ni, Co, and N as catalyst components, and its surface is densely covered with nanoflowers with a diameter of about 3-5 μm. The nanoflowers are stacked on each other. The lateral dimensions are hundreds of nanometers and the thickness is 2‑10nm. The preparation method is one-step hydrothermal and tube furnace calcination to obtain NiCoN. A preparation method of MgH ₂ -based hydrogen storage material based on NiCoN is disclosed: under argon conditions, NiCoN and MgH ₂ are mixed and then subjected to forward and reverse ball milling. . The obtained MgH ₂ -based hydrogen storage material based on NiCoN is used as a hydrogen storage material. The doping amount of NiCoN is 6wt%, and the initial dehydrogenation temperature is 160-175°C; the dehydrogenation amount at 285°C is 4.5-5.0wt%; The hydrogen absorption capacity at 75°C is 2.5-2.9wt%; the retention rate after 10 cycles is 96-98%; the activation energy of the dehydrogenation reaction is reduced to 56.5kJ/mol.

Description

A bimetallic nitride catalyst and its preparation method and application

Technical field

The present invention is in the technical field of designing hydrogen storage materials for new energy materials, and specifically relates to a bimetallic nitride catalyst and its preparation method and application.

Background technique

At present, due to limited fossil fuel resources and serious environmental pollution, the development of clean energy is imperative. Hydrogen energy is considered the most promising alternative energy due to its abundant output, environmental friendliness, and high calorific value. However, among many hydrogen storage materials, magnesium-based materials have obvious advantages in terms of hydrogen storage capacity, cost, and raw material reserves. In order to meet the needs of practical applications, magnesium-based hydrogen storage materials need to reduce the thermodynamic stability and improve the hydrogen absorption and desorption kinetics. Currently, researchers generally use methods such as catalysis, alloying, nanotechnology, and surface modification to improve the performance of magnesium-based hydrogen storage materials. These methods can increase the hydrogenation/dehydrogenation reaction rate and reduce the apparent activation energy of hydrogen absorption and desorption.

Magnesium hydride (MgH ₂ ) has a high hydrogen storage capacity (7.6wt%) and good reversibility, and is considered to be one of the most potential solid-state hydrogen storage materials. However, it has high thermal stability, slow kinetics, and serious problems. Restricting its use as a vehicle energy storage carrier.

In recent years, researchers have improved the hydrogen storage performance of MgH ₂ through doping modification, nanotechnology, composite system construction and confinement, that is, reducing the hydrogen absorption and desorption temperature, improving the hydrogen absorption and desorption kinetics and reversibility. According to reports, Although transition metals as catalysts, such as TiO ₂ , NiC1 and Ni ₃ N, can effectively improve the hydrogen storage performance of MgH ₂ , they have not greatly improved the hydrogen storage performance of MgH ₂ . Currently, there are many studies on They are modified carbon materials, transition metals and their oxides, nitrides, and alloy compounds. These are catalytically active additives. Among them, transition metals can effectively weaken the Mg-H bond because hydrogen atoms tend to interact with transition metals. Covalent bonds are formed, while the covalent bonds between 3d transition metal elements and H atoms are relatively weak. Therefore, transition metals are identified as the main catalytically active substances and are widely used to improve the hydrogen absorption and desorption performance of MgH _hydrogen storage systems.

At present, transition metal nitrides as catalysts can effectively improve the hydrogen storage performance of composite materials, but many single metal nitrides appear as catalysts. NiCoN has good hydrogen storage performance as a catalyst. As a nanoflower-like NiCoN, the unique phase composition and The structure can greatly enhance the ball milling effect and contribute to the uniform distribution of NiCoN on the _MgH2 matrix. The in-situ formed Mg ₂ Co/Mg ₂ CoH ₅ and Mg ₂ Ni/Mg ₂ NiH ₄ can greatly promote hydrogen dissociation and lower the initial hydrogen release temperature. Therefore, NiCoN can be used as a catalyst to further improve the composite material. hydrogen storage performance.

Prior Art Zhang et al. (International Journal of Hydrogen Energy, 2017, DOI: 10.1016/j.ijhydene.2017.07.220) synthesized Fe nanocatalysts and demonstrated excellent bifunctional catalytic activity for MgH _hydrogen storage, enabling _MgH2 modified by Fe nanocatalyst can start to release hydrogen at 182.3°C.

Similarly, Zhang et al. (Journal of Energy Chemistry, 2020, DOI: 2020.04.104) used ball milling method of nickel-based compounds (Ni ₃ C-MgH ₂ , Ni ₃ N-MgH ₂ , NiO-MgH ₂ and MgH _2- Ni ₂ P) The introduction of MgH ₂ system reduces the hydrogen desorption starting temperature to 160°C, 180°C, 205°C and 248°C respectively.

To sum up, every nickel-based compound will improve the performance of MgH ₂ .

On this basis, Liu et al. (International Journal of Hydrogen Energy, 2020, DOI: https://doi.org/10.1016/j.ijhydene.2020.04.104) used a hydrothermal method to prepare NiFe-LDH composite materials, and then After reduction in a hydrogen atmosphere, a layered Ni ₃ Fe catalyst composite material was prepared, and the synergistic effect between the two was used to improve the overall performance of MgH ₂ . Although this technical solution reduces the starting temperature of MgH ₂ to 205°C through the synergistic effect of Ni and Fe, and evenly anchors Ni ₃ Fe in rGO through hydrothermal heating to reduce the starting temperature to 185°C, its performance Far from reaching the theoretical upper limit of composite materials.

Therefore, controlling the structure of the material through reasonable preparation methods to obtain thinner flower-like materials is an effective way to improve material performance.

The above work reports used nickel-based compounds and transition metal Ni and Fe bases to dope MgH ₂ for modification or collaborative catalysis to improve the hydrogen storage performance of MgH ₂ . However, the hydrogen storage properties of MgH ₂ and hydrogen storage materials have not yet been improved. To meet actual needs, further improvement is needed. Therefore, the problems that still need to be solved are:

1. The catalyst does not have good catalytic performance:

2. The elements contained in the catalyst do not have the characteristics of enhancing the absorption and dissociation of hydrogen;

3. The catalyst has catalytic performance, but does not have a special morphology. The special morphology of the catalyst affects the hydrogen storage performance of MgH ₂ ;

Contents of the invention

The object of the present invention is to provide a bimetallic nitride catalyst and its preparation method and application.

Based on the applicant's work and the research and analysis of the above technical solutions, the following conclusion can be drawn: Current research on the preparation method of Ni ₃ N composite materials still cannot achieve a substantial improvement in the performance of MgH ₂ .

Therefore, the present invention aims at the technical problems existing in the prior art and adopts methods with other preparation conditions to achieve the following invention objectives:

1. NiCoN bimetallic nanoflowers were obtained through hydrothermal and calcination technology. Then we doped the prepared NiCoN into MgH ₂ by grinding, which will effectively improve the hydrogen absorption and release performance of MgH ₂ ;

2. Prepare the catalytic MgH ₂ composite material, and grind the MgH ₂ together with 6wt% catalyst through a planetary ball mill under an Ar atmosphere;

In order to achieve the above-mentioned object of the invention, the technical solutions adopted by the present invention are:

Bimetallic nitride NiCoN is used as a catalyst, which is characterized by: a simple preparation process, with Ni, Co, and N as the main components of the catalyst; NiCoN bimetallic nanoflowers are obtained through a simple one-step hydrothermal and calcination technology.

Among them, the NiCoN is a nanoflower-shaped catalyst synthesized through hydrothermal and tube furnace calcination. The microscopic morphology is flake-shaped flower-like, which greatly enhances the ball milling effect and contributes to the uniform distribution of NiCoN on the MgH ₂ matrix;

The base materials of the catalyst are nickel nitrate hexahydrate, cobalt sulfate heptahydrate, urea and ammonium fluoride.

The preparation method of bimetallic nitride NiCoN catalyst includes the following steps:

Step 1) Preparation of NiCoN, add a certain amount of Ni(NO ₃ ) ₂ ·6H ₂ O and CoSO ₄ ·7H ₂ O into deionized water, stir evenly, and then drop NHF ₄ and urea into the above mixture in sequence. Stir continuously. After complete dissolution, transfer the solution to an autoclave and keep it warm for a period of time. After natural cooling to room temperature, the hydrothermal sample sediments were collected and washed several times with deionized water, and the precipitates after centrifugation were collected and then dried by vacuum overnight. The dried powder is then transferred to a tube furnace and calcined for a period of time under a flowing argon gas flow to obtain NiCoN;

In the step 1, Ni(NO ₃ ) ₂ ·6H ₂ O (1mmol), CoSO ₄ ·7H ₂ O (1mmol), H ₂ O (30mL), NHF ₄ (5mmol), and urea (10mmol) are used. The stirring conditions of step 1 are stirring for 30 minutes, the drug dripping sequence conditions of step 1 are slow dripping in sequence, the hydrothermal reaction conditions of step 1 are 100°C for 8 hours, and the washing and drying conditions of step 1 are to Wash and centrifuge 6 times with ionized water, the centrifugal speed is 9000r/min, the centrifugation time is 5min, and dried at 65°C for 10h. The calcination condition in step 1 is calcination at 500°C for 2h.

Step 2) Preparation of NiCoN catalyst-doped magnesium hydride hydrogen storage material. Mix the NiCoN and magnesium hydride obtained in step 1 at a certain mass ratio, and conduct ball milling under certain conditions to obtain a NiCoN-doped magnesium hydride storage material. Hydrogen materials.

The mass fraction of NiCoN is 2-8wt%; the ball milling conditions are: argon gas is used as a protective atmosphere, the ball-to-material ratio is 40:1, the ball milling speed is 400-450r/min, and the ball milling time is 10h.

The catalyst obtained by the present invention is bimetallic nitride NiCoN. The beneficial technical effects can be seen through testing:

After testing the bimetallic nitride NiCoN with a scanning electron microscope, it can be seen that the catalyst is in the form of sheet-shaped nanoflowers.

Thermogravimetry (TG) testing of the bimetallic nitride NiCoN catalyst shows that when the doping amount of the catalyst is 6wt%, the initial release temperature of the system drops to 164-185°C, and the hydrogen release amount reaches 6.1-6.9wt%.

The pressure-composition-temperature (PCT) test of the bimetallic nitride NiCoN catalyst shows that: when hydrogen is released isothermally, the system can completely release hydrogen at 330°C, and the hydrogen release amount reaches 6.2-6.6wt% within 15 minutes: when hydrogen is absorbed isothermally, Even under conditions as low as 150°C, the system can still absorb 5.2-5.8wt% hydrogen within 50 minutes.

Therefore, the bimetallic nitride NiCoN catalyst of the present invention has the following advantages over the existing technology:

1) Mg ₂ Co/Mg ₂ Ni and Mg ₂ CoH ₅ /Mg ₂ NiH ₄ formed in situ serve as induction phases, which have lower hydrogenation and dehydrogenation temperatures and can be absorbed before the Mg/MgH ₂ system and desorb hydrogen, so they can be considered as "hydrogen pumps" in composite materials.

2) The initial hydrogen release temperature of the NiCoN catalyst synthesized by the method of the present invention after ball milling with _MgH2 is 164°C, which is higher than the value reported in the above literature.

Therefore, compared with the existing technology, the present invention has better hydrogen storage performance and material stability performance, and has broad application prospects in the field of hydrogen storage.

Picture description:

Figure 1 is an XRD pattern of the NiCoN catalyst material prepared in Example 1;

Figure 2 is a scanning electron microscope image of the NiCoN catalyst material prepared in Example 1;

Figure 3 shows the TG curves of different doping amounts of the NiCoN-MgH ₂ composite material prepared in Example 1.

Figure 4 is a test chart of the isothermal hydrogen release performance at different temperatures of the NiCoN- _MgH composite prepared in Example 1;

Figure 5 is a test chart of the isothermal hydrogen absorption performance at different temperatures of the NiCoN- _MgH composite prepared in Example 1;

Figure 6 is a test chart of the isothermal hydrogen release performance at different temperatures of the ball-milled MgH prepared in Example ₁ without incorporating a catalyst;

Figure 7 is a test chart of the isothermal hydrogen release performance at different temperatures of the ball-milled MgH prepared in Example ₁ without incorporating a catalyst;

Figure 8 shows the DSC curves and Kissinger curves of different heating rates of the NiCoN-MgH ₂ composite material prepared in Example 1;

Figure 9 shows the DSC curves and Kissinger curves of ball-milled MgH ₂ prepared in Example 1 at different heating rates without incorporating a catalyst;

Figure 10 is the XRD pattern of ball milling and hydrogen absorption/desorption of the NiCoN-MgH ₂ composite prepared in Example 1;

Figure 11 is a histogram of the hydrogen release cycle life of the NiCoN- _MgH composite material prepared in Example 1;

Detailed ways

The present invention will be further described in detail through examples and in conjunction with the description and drawings, but the present invention is not limited thereto.

Example 1

This embodiment provides a method for preparing a bimetallic nitride NiCoN catalyst. The preparation method includes the following steps:

Step 1. Preparation of NiCoN precursor. First, dissolve Ni(NO ₃ ) ₂ ·6H ₂ O (1mmol) and CoSO ₄ 7H ₂ O (1mmol) in 30 mL deionized water and stir magnetically. Then NHF ₄ (5mmol) and 10mmol urea were added to the above solution in sequence. Continue stirring until complete dissolution, transfer the solution to a 100 mL autoclave and keep warm. After natural cooling to room temperature, the hydrothermal sample sediments were collected;

Step 2) Wash several times with deionized water, collect the precipitate after centrifugation, and then dry it in a vacuum drying oven overnight. The urea and dried powder are then transferred to a tube furnace and calcined under flowing air flow. After natural cooling to room temperature, the samples were collected and transferred to an Ar-filled glove box for further use.

The conditions for the hydrothermal reaction and tubular furnace calcination in the present invention, without special instructions, are to maintain the hydrothermal temperature at 100°C for 8 hours, and the tubular furnace calcination to maintain the temperature at 500°C for 2 hours;

The conditions of stirring, centrifugation, and washing in the present invention, without special instructions, are all stirring for 30 minutes, centrifugation speed of 9000 r/min, centrifugation time of 5 minutes, and centrifugation times of 6 times for centrifugal washing;

The drying conditions of the present invention, without special instructions, are all dried under the conditions of a drying temperature of 60°C and a drying time of 10 hours;

In order to prove that NiCoN was successfully prepared in step 1, XRD test was performed. The test results are shown in Figure 1. The diffraction peak of NiCoN agrees well with the standard peak crystal plane of NiCoN. The test results show that NiCoN was successfully synthesized with high purity and high crystallinity.

In order to prove the microstructure of the NiCoN precursor obtained in step 1, SEM testing was performed. The test results are shown in Figure 2. After SEM testing, it was found that the microstructure of NiCoN is in the form of sheet-shaped nanoflowers.

A method for preparing MgH ₂ -based hydrogen storage materials based on NiCoN, that is, the application of nanoflower-shaped NiCoN as a catalyst for MgH ₂ hydrogen storage materials. The specific preparation method is as follows: the entire process is under argon gas conditions, with the NiCoN addition amount being 6wt%. After mixing NiCoN and MgH ₂ , perform high-energy ball milling under the conditions of a ball-to-material ratio of 40:1, a ball milling speed of 400 rpm, and a total ball milling time of 10 hours. The high-energy ball milling method is forward and reverse ball milling, and the single ball milling time is The grinding time was 12 minutes, and the ball milling interval was 6 minutes, thereby obtaining a MgH ₂ -based hydrogen storage material with an added amount of NiCoN of 6 wt%, which was named MgH ₂ -6NiCoN.

In order to prove the hydrogen storage performance of MgH ₂ -6NiCoN composite, TG test and PCT test were performed.

In order to prove the initial hydrogen release temperature and hydrogen release amount of the MgH ₂ -6NiCoN composite material, a TG test was conducted on the hydrogen storage material. The test results are shown in Figure 3. The initial hydrogen release temperature of the hydrogen storage material doped with the catalyst The hydrogen release amount at 164°C is 6.12wt%. As the doping amount increases, the hydrogen release amount of the material shows a decreasing pattern.

In order to prove the hydrogen absorption and release capabilities of MgH ₂ -6NiCoN composite materials at different temperatures, PCT tests were conducted on the hydrogen storage materials, as shown in Figure 4-7. It can be seen from the figure that MgH ₂ -6NiCoN has excellent low-temperature hydrogen storage Performance, it can absorb a certain amount of hydrogen in a short period of time. At 150℃, it can quickly absorb 5.52wt% hydrogen in 30min. At the same time, it can also release 4.98wt% hydrogen in 30min at a lower dehydrogenation temperature of 285℃. , when it reaches 300℃, it can basically achieve complete hydrogen release within 30 minutes.

In order to prove the catalytic mechanism of MgH ₂ -6NiCoN composite materials, XRD tests were conducted on the hydrogen storage materials after ball milling and hydrogen absorption and release, as shown in Figure 10. It can be seen from the figure that NiCoN still exists after MgH ₂ -6NiCoN ball milling. NiCoN decomposes to produce Mg, Mg2Ni, and Mg2Co when hydrogen is released once, and MgH2, Mg2Ni4, and Mg2CoH5 are produced by absorbing hydrogen again.

In order to prove the stability of the catalytically active material of the MgH ₂ -6NiCoN composite material, the cycle performance of the hydrogen storage material was tested. The specific test method is: use PCT to test the cycle performance at 310°C. The hydrogen pressure of hydrogenation is 2Mpa. The test analysis results are shown in Figure 11. After 10 cycles, the actual hydrogen capacity of MgH ₂ -6NiCoN remains at 5.85wt%. Compared with the first cycle capacity, it is equivalent to a capacity retention rate of 96.3%, indicating that MgH _2-6NiCoN exhibits stable dehydrogenation and has good cycle stability.

The above TG test and PCT test results can prove that NiCoN as a catalyst can significantly reduce the initial hydrogen release temperature of MgH ₂ and effectively catalyze the hydrogen absorption and release reaction of MgH ₂ to improve the hydrogen absorption and release capacity.

In order to study the influence of NiCoN as a catalyst on the activation energy of MgH ₂ and further reveal the catalytic mechanism of NiCoN, the XRD patterns of dehydrogenated and rehydrogenated MgH ₂ -6NiCoN were measured. In a glove box filled with argon, weigh NiCoN powder with a mass fraction of 6wt% and mix it with _MgH2 . Then place the powder into a stainless steel ball mill tank, and weigh the stainless steel grinding balls according to the ball-to-material ratio of 40:1 and leave them in the ball mill tank. Take out the ball mill tank containing the powder and stainless steel balls from the glove box, and use forward and reverse rotation in a ball mill with a rotation speed of 400 rpm for 10 hours, 12 minutes each time, and a 6-minute pause to obtain the hydrogen storage material. After completion, put the stainless steel ball milling jar into the glove box, take out the ball-milled powder, and then conduct relevant tests.

In order to prove the influence of NiCoN on the hydrogen storage performance of MgH ₂ , Comparative Examples 1 and 2 are provided. Comparative Example 1 uses MgH ₂ -6NiCoN and MgH ₂ as hydrogen storage materials to compare hydrogen absorption and release at different temperatures. Comparative Example 2 uses MgH ₂ -6NiCoN and MgH ₂ are used as hydrogen storage materials to compare the activation energies; at the same time, in order to prove the catalytic mechanism of NiCoN, Comparative Example 2 is provided to reveal the NiCoN catalysis by comparing the peak positions in the XRD patterns of the hydrogen absorption and release of the composite materials. mechanism.

Comparative example 1

A method for preparing MgH ₂ -6NiCoN composite material. The steps not specifically described are the same as those in Example 1. The composite material MgH ₂ -6NiCoN and ball-milled MgH ₂ are subjected to PCT testing.

The PCT test results of MgH ₂ -6NiCoN and ball-milled MgH ₂ are shown in Figure 4-7. The MgH ₂ -6NiCoN composite desorbs 4.96wt% hydrogen in 30 minutes at 285°C and absorbs 5.52wt% hydrogen in 30 minutes at 150°C. Compared with ball-milled MgH _2, hydrogen release is 0.93wt% within 30 minutes at 300°C and hydrogen absorption is 1.56wt% within 30min at 250°C.

Comparative example 2

A method for preparing MgH ₂ -6NiCoN composite material. The steps not specifically described are the same as those in Example 1. The composite material MgH ₂ -6NiCoN and ball-milled MgH ₂ are subjected to DSC testing.

The DSC test results of MgH ₂ -6NiCoN and MgH ₂ are shown in Figure 8-9. The activation energy of MgH2-6NiCoN composite material is reduced by 71kJ/mol compared with ball milled MgH ₂ .

Comparative example 3

A method for preparing MgH ₂ -6NiCoN. The unspecified steps are the same as those in Example 1. The ball-milled sample and the ball-milled sample that absorbs and releases hydrogen are prepared in a glove box, and then taken out for XRD testing.

The XRD test results of MgH2-6NiCoN are shown in Figure 9. In the XRD pattern of dehydrogenated _MgH2-6NiCoN , it is worth noting that the diffraction peaks of _Mg2Co and _Mg2Ni were detected, which indicates that _MgH2 is in the dehydrogenation process. It reacts with Co and Ni to form Mg ₂ Co and Mg ₂ Ni. Compared with the ground MgH ₂ -6NiCoN, the rehydrogenated MgH ₂ -6NiCoN not only contains MgH ₂ but also Mg ₂ CoH ₅ and Mg ₂ NiH ₄ , proving It is proved that the Mg ₂ Co and Mg ₂ Ni formed in situ can absorb hydrogen to generate the corresponding hydride. It can be speculated that the reversible phase change of Mg ₂ Co/Mg ₂ CoH ₅ and Mg ₂ Ni/Mg ₂ NiH ₄ acts as a "hydrogen pump" function, thus reducing the reaction activation energy and promoting the absorption and dissociation of hydrogen.

Combining the results of Example 1, Comparative Examples 1, 2 and 3, it can be seen that there is a synergistic catalytic effect between Mg ₂ Ni and Mg ₂ Co formed in situ, and NiCoN has a significant effect on the de/hydrogenation kinetics of MgH ₂ /Mg. Reinforcement effect, the hydrogen release amount of MgH ₂ -6NiCoN composite at 285°C for 30 minutes is 4.96wt%, and it absorbs 4.83wt% of H ₂ within 10 minutes at 150°C. The activation energy is reduced by 71kJ/mol compared to ball-milled _MgH2 . In-situ The formed Mg ₂ Co and Mg ₂ Ni appear in the first dehydrogenation process and are further converted into Mg ₂ CoH ₅ and Mg ₂ NiH ₄ after rehydrogenation, Mg ₂ Co/Mg ₂ CoH ₅ and Mg ₂ Ni/ The reversible phase transition of _Mg2NiH4 accelerates the dissociation and recombination of hydrogen, thus explaining the excellent hydrogen absorption/desorption kinetics _of the composites.

Claims (6)

1. A bimetallic nitride catalyst characterized by: the catalyst comprises elements of Ni, co and N, and is in a nano flower shape.

2. A method for preparing a bimetallic nitride catalyst, the method comprising the steps of:

step 1), ni (NO) ₃ ) ₂ ·6H ₂ O and CoSO ₄ ·7H ₂ O is dissolved in deionized water, magnetically stirred, and then NHF is stirred ₄ And urea are added into the solution in sequence, stirring is continued, after complete dissolution, the solution is transferred into an autoclave for heat preservation for a period of time, after natural cooling to room temperature,collecting a hot sample deposit;

and 2) washing the precipitate with deionized water for several times, collecting the precipitate after centrifugation, then drying in vacuum overnight, sequentially transferring urea and the dried precipitate into a tube furnace, calcining for a period of time under flowing argon gas flow, naturally cooling to room temperature, collecting a sample, and transferring the sample into a glove box filled with Ar, thereby obtaining the bimetallic nitride catalyst NiCoN.

3. The method for preparing a bimetallic nitride catalyst according to claim 2, wherein: in the step 1), ni (NO) ₃ ) ₂ ·6H ₂ O1mmol、CoSO ₄ 7H ₂ O is 1mmol, H ₂ O is 30mL, NHF ₄ 5mmol of urea and 10mmol of urea, wherein the magnetic stirring time is 30-60min, and the Ni (NO ₃ ) ₂ ·6H ₂ O、CoSO ₄ ·7H ₂ O、NHF ₄ And urea is slowly dripped in sequence, and the temperature is kept in the autoclave for 8 hours at 100 ℃;

in the step 2), the washing condition is that deionized water is used for washing and centrifuging for 6-8 times, the centrifugal speed is 8000-9000 rpm, the centrifugal time is 5-10min, the drying condition is that the drying is carried out at 60-100 ℃ for 10h, and the calcining condition is that the calcining is carried out at 450 ℃ for 2-3h under argon.

4. Use of a hydrogen storage material doped with magnesium hydride using a bimetallic nitride catalyst as claimed in claim 1 as a hydrogen storage means, characterized in that: mixing the bimetallic nitride catalyst and magnesium hydride in a certain mass ratio, and performing ball milling under a certain condition to obtain a hydrogen storage material doped with the magnesium hydride by the NiCoN catalyst;

when the doped amount of the catalyst is 2-8wt%, the initial hydrogen release temperature of the system is reduced to 164-185 ℃, the hydrogen release amount reaches 6.1-6.5wt%, the system can completely release hydrogen at 330 ℃ during isothermal hydrogen release, the hydrogen release amount reaches 6.3-6.6wt% within 15min, and the hydrogen can be absorbed by the system within 5.2-5.8wt% even under the condition of low temperature of 150 ℃ during isothermal hydrogen absorption within 50 min.

5. The use of a hydrogen storage material doped with magnesium hydride as claimed in claim 4 as a hydrogen storage field, characterized in that: the ball milling condition is that argon is used as protective atmosphere, the ball-material ratio is 40:1, the ball milling rotating speed is 400-450r/min, and the ball milling time is 10-12h.

6. The use of a hydrogen storage material doped with magnesium hydride as claimed in claim 4 as a hydrogen storage field, characterized in that: after recycling, the sample shows good hydrogen storage reversibility and stable circularity, and after 10 times of circulation, the retention rate of the actual hydrogen capacity is 96% of the primary circulation capacity.