A bimetallic nitride catalyst and its preparation method and application

Abstract

The present 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, with a lateral size of hundreds of nanometers and a thickness of 2-10 nm. Its preparation method is a one-step hydrothermal and tubular furnace calcination to obtain NiCoN. A method for preparing a MgH2-based hydrogen storage material based on NiCoN is disclosed: under argon conditions, NiCoN is mixed with MgH2 and then subjected to forward and reverse ball milling. The obtained NiCoN-based MgH2-based hydrogen storage material is used as a hydrogen storage material. The NiCoN doping amount is 6wt%, the initial dehydrogenation temperature is 160-175°C; the dehydrogenation amount is 4.5-5.0wt% at 285°C; the hydrogen absorption amount is 2.5-2.9wt% at 75°C; the retention rate after 10 cycles is 96-98%; and the activation energy of the dehydrogenation reaction is reduced to 56.5kJ / mol.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogen storage materials for designing new energy materials, and specifically to a bimetallic nitride catalyst, a preparation method and an application thereof. Background Art

[0002] Currently, due to limited fossil fuel resources and severe environmental pollution, the development of clean energy is imperative. Hydrogen energy is considered the most promising alternative energy source due to its abundant production, environmental friendliness, and high calorific value. However, among the 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 thermodynamic stability and improve the kinetics of hydrogen absorption and desorption. 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.

[0003] Magnesium hydride (MgH2) has a high hydrogen storage capacity (7.6wt%) and good reversibility, and is considered to be one of the most promising solid-state hydrogen storage materials. However, its high thermal stability and slow kinetics seriously restrict its use as an on-board energy storage carrier.

[0004] In recent years, researchers have improved the hydrogen storage properties of MgH2 through methods such as doping, nanosizing, composite system construction, and confinement, specifically by lowering the absorption and desorption temperatures and enhancing the kinetics and reversibility of absorption and desorption. It has been reported that while transition metal catalysts such as TiO2, NiCl, and Ni3N can effectively improve the hydrogen storage properties of MgH2, they do not significantly enhance the overall performance. Currently, research focuses on modified carbon materials, transition metals, and their oxides, nitrides, and alloy compounds, all of which are catalytically active additives. Transition metals can effectively weaken the Mg-H bond because hydrogen atoms tend to form covalent bonds with transition metals, while 3d transition metal elements have relatively weak covalent bonds with hydrogen atoms. Therefore, transition metals are considered the primary catalytically active species and are widely used to enhance the hydrogen absorption and desorption properties of MgH2 hydrogen storage systems.

[0005] Currently, transition metal nitrides can effectively improve the hydrogen storage performance of composite materials as catalysts, but many of them are single-metal nitride catalysts. NiCoN has excellent hydrogen storage performance as a catalyst. The unique phase composition and structure of nanoflower-like NiCoN can greatly enhance the ball milling effect and promote the uniform distribution of NiCoN on the MgH2 matrix. The in-situ formation of Mg2Co / Mg2CoH5 and Mg2Ni / Mg2NiH4 can greatly promote hydrogen dissociation and reduce the onset of hydrogen desorption temperature. Therefore, NiCoN as a catalyst can further improve the hydrogen storage performance of composite materials.

[0006] 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 MgH2 hydrogen storage, enabling the Fe nanocatalyst-modified MgH2 to release hydrogen at 182.3°C.

[0007] Similarly, Zhang et al. (Journal of Energy Chemistry, 2020, DOI: 2020.04.104) used ball milling to prepare nickel-based compounds (Ni3C-MgH2, Ni3N-MgH2, NiO-MgH2 and MgH 2- The introduction of Ni2P) into the MgH2 system reduced the hydrogen desorption starting temperature to 160℃, 180℃, 205℃ and 248℃, respectively.

[0008] In summary, each nickel-based compound will improve the performance of MgH2.

[0009] On this basis, Liu et al. (International Journal of Hydrogen Energy, 2020, DOI: https: / / doi.org / 10.1016 / j.ijhydene.2020.04.104) prepared NiFe-LDH composite materials by hydrothermal method, and then reduced them in hydrogen atmosphere to prepare layered Ni3Fe catalyst composite materials, and used the synergistic effect between the two to improve the comprehensive performance of MgH2. Although this technical solution reduces the starting temperature of MgH2 to 205°C through the synergistic effect of Ni and Fe, and uniformly anchors Ni3Fe to rGO through hydrothermal treatment to reduce the starting temperature to 185°C, its performance is far from reaching the theoretical upper limit of the composite material.

[0010] Therefore, controlling the structure of the material through reasonable preparation methods to obtain flower-like materials with thinner layers is an effective way to improve the performance of the material.

[0011] The above work reports the use of nickel-based compounds and transition metal Ni and Fe-based doping into MgH2 for modification or synergistic catalysis to improve the hydrogen storage performance of MgH2. However, the hydrogen storage performance of MgH2 hydrogen storage materials still does not meet practical needs and needs further improvement. Therefore, the following issues need to be addressed:

[0012] 1. The catalyst does not have good catalytic performance:

[0013] 2. The elements contained in the catalyst do not have the characteristics of enhancing the absorption and dissociation of hydrogen;

[0014] 3. The catalyst has catalytic performance but no special morphology. The special morphology of the catalyst affects the hydrogen storage performance of MgH2; Summary of the Invention

[0015] The purpose of the present invention is to provide a bimetallic nitride catalyst and a preparation method and application thereof.

[0016] Based on the applicant's work and the research and analysis of the above technical solutions, the following conclusion can be drawn: the current research on the preparation method of Ni3N composite materials is still unable to achieve a significant improvement in the performance of MgH2.

[0017] Therefore, the present invention addresses the technical problems existing in the prior art and adopts a method with other preparation conditions to achieve the following invention objectives:

[0018] 1. NiCoN bimetallic nanoflowers were obtained through hydrothermal and calcination techniques. Then, we doped the prepared NiCoN into MgH2 by grinding, which effectively improved the hydrogen absorption and desorption properties of MgH2;

[0019] 2. Prepare catalytic MgH2 composite materials by grinding MgH2 and 6 wt% of catalyst together using a planetary ball mill under Ar atmosphere;

[0020] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is:

[0021] The 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; and NiCoN bimetallic nanoflowers are obtained through a simple one-step hydrothermal and calcination technology.

[0022] The NiCoN is a nano-flower-shaped catalyst synthesized by hydrothermal and tubular furnace calcination, and its microscopic morphology is a sheet-shaped flower-like, which greatly enhances the ball milling effect and helps to uniformly distribute NiCoN on the MgH2 matrix;

[0023] The base materials of the catalyst are nickel nitrate hexahydrate, cobalt sulfate heptahydrate, urea and ammonium fluoride.

[0024] The preparation method of the bimetallic nitride NiCoN catalyst comprises the following steps:

[0025] Step 1) Preparation of NiCoN: Add a certain amount of Ni(NO3)2·6H2O and CoSO4·7H2O to deionized water and stir evenly. Then, add NHF4 and urea dropwise to the above mixture in sequence and continue stirring. After complete dissolution, transfer the solution to an autoclave and keep it warm for a period of time. After cooling naturally to room temperature, collect the hydrothermal sample sediment and wash it several times with deionized water. Collect the precipitate after centrifugation and then vacuum dry it 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.

[0026] In the step 1, Ni(NO3)2·6H2O (1mmol), CoSO4·7H2O (1mmol), H2O (30mL), NHF4 (5mmol), and urea (10mmol) are added. The stirring condition of the step 1 is stirring for 30 minutes. The order of drug addition in the step 1 is to slowly add the drugs in sequence. The hydrothermal reaction condition of the step 1 is to keep warm at 100°C for 8 hours. The washing and drying conditions of the step 1 are washing with deionized water and centrifuging for 6 times at a centrifugal speed of 9000r / min and a centrifugal time of 5 minutes, and drying at 65°C for 10 hours. The calcination condition of the step 1 is calcination at 500°C for 2 hours.

[0027] Step 2) Preparation of NiCoN catalyst-doped magnesium hydride hydrogen storage material: NiCoN and magnesium hydride obtained in step 1 are mixed in a certain mass ratio and ball milled under certain conditions to obtain NiCoN-doped magnesium hydride hydrogen storage material.

[0028] The mass fraction of NiCoN is 2-8 wt %; the ball milling conditions are: argon as the protective atmosphere, a ball-to-material ratio of 40:1, a ball milling speed of 400-450 r / min, and a ball milling time of 10 h.

[0029] The catalyst obtained by the present invention is a bimetallic nitride NiCoN. The beneficial technical effects are shown by testing:

[0030] Scanning electron microscopy testing of the bimetallic nitride NiCoN reveals that the catalyst is in the form of sheet-like nanoflowers.

[0031] Thermogravimetric (TG) detection 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%.

[0032] Pressure-composition-temperature (PCT) testing of the bimetallic nitride NiCoN catalyst showed that during isothermal dehydrogenation, the system could completely dehydrogenate at 330°C, with the amount of hydrogen released reaching 6.2-6.6 wt% within 15 minutes. During isothermal hydrogen absorption, the system could still absorb 5.2-5.8 wt% of hydrogen within 50 minutes even at conditions as low as 150°C.

[0033] Therefore, the bimetallic nitride NiCoN catalyst of the present invention has the following advantages over the prior art:

[0034] 1) The in situ formed Mg2Co / Mg2Ni and Mg2CoH5 / Mg2NiH4 act as induced phases, which can absorb and desorb hydrogen before the Mg / MgH2 system due to their lower hydrogenation and dehydrogenation temperatures, so they can be regarded as “hydrogen pumps” in the composites.

[0035] 2) The initial hydrogen desorption 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.

[0036] Therefore, compared with the prior art, the present invention has better hydrogen storage performance and material stability, and has broad application prospects in the field of hydrogen storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is the XRD pattern of the NiCoN catalyst material prepared in Example 1;

[0038] Figure 2 This is a scanning electron microscope image of the NiCoN catalyst material prepared in Example 1;

[0039] Figure 3 TG curves of the NiCoN-MgH2 composite material prepared in Example 1 with different doping amounts.

[0040] Figure 4 This is a test diagram of the isothermal hydrogen desorption performance of the NiCoN-MgH2 composite material prepared in Example 1 at different temperatures;

[0041] Figure 5 This is a test diagram of the isothermal hydrogen absorption performance of the NiCoN-MgH2 composite material prepared in Example 1 at different temperatures;

[0042] Figure 6This is a test diagram of the isothermal hydrogen release performance of ball-milled MgH2 prepared in Example 1 without adding a catalyst at different temperatures;

[0043] Figure 7 This is a test diagram of the isothermal hydrogen release performance of ball-milled MgH2 prepared in Example 1 without adding a catalyst at different temperatures;

[0044] Figure 8 DSC curves and Kissinger curves of the NiCoN-MgH2 composite material prepared in Example 1 at different heating rates;

[0045] Figure 9 The DSC curves and Kissinger curves of the ball-milled MgH2 without catalyst prepared in Example 1 at different heating rates;

[0046] Figure 10 The ball milling and hydrogen absorption / desorption XRD patterns of the NiCoN-MgH2 composite material prepared in Example 1;

[0047] Figure 11 This is a bar chart of the hydrogen desorption cycle life of the NiCoN-MgH2 composite material prepared in Example 1; DETAILED DESCRIPTION

[0048] The present invention is further described in detail through embodiments and in conjunction with the accompanying drawings, but the present invention is not limited thereto.

[0049] Example 1

[0050] This embodiment provides a method for preparing a bimetallic nitride NiCoN catalyst, the preparation method comprising the following steps:

[0051] Step 1, preparation of NiCoN precursor: First, dissolve Ni(NO3)2·6H2O (1 mmol) and CoSO47H2O (1 mmol) in 30 mL of deionized water with magnetic stirring. Then, add NHF4 (5 mmol) and 10 mmol of urea to the above solution in sequence. Continue stirring until completely dissolved, then transfer the solution to a 100 mL autoclave and keep it warm. After cooling naturally to room temperature, collect the hydrothermal sample sediment;

[0052] Step 2) Wash several times with deionized water, collect the precipitate after centrifugation, and then dry it in a vacuum oven overnight. The urea and dried powder are then transferred to a tube furnace and calcined under a flowing air stream. After cooling naturally to room temperature, the sample is collected and transferred to an Ar-filled glove box for further use.

[0053] The conditions for the hydrothermal reaction and tubular furnace calcination of the present invention, unless otherwise specified, are: the hydrothermal temperature is 100° C. and the temperature is kept at 8 h; the tubular furnace calcination is 500° C. and the temperature is kept at 2 h;

[0054] The stirring, centrifugation and washing conditions of the present invention, unless otherwise specified, are stirring for 30 min, centrifuging at a speed of 9000 r / min, centrifuging for 5 min, and centrifuging 6 times for centrifugation washing;

[0055] The drying conditions of the present invention, unless otherwise specified, are all carried out at a drying temperature of 60°C and a drying time of 10 hours;

[0056] In order to prove that NiCoN was successfully prepared in step 1, XRD test was performed. The test results are as follows Figure 1 As shown in the figure, the diffraction peak of NiCoN is in good agreement with the standard peak crystal plane of NiCoN. The test results show that NiCoN was successfully synthesized with high purity and high crystallinity.

[0057] In order to verify the microstructure of the NiCoN precursor obtained in step 1, SEM test was performed. The test results are shown in Figure 2. Figure 2 As shown in the figure, SEM test shows that the microstructure of NiCoN is a sheet-shaped nanoflower.

[0058] A method for preparing a NiCoN-based MgH2-based hydrogen storage material, namely, using nanoflower-shaped NiCoN as a catalyst for the MgH2 hydrogen storage material. The specific preparation method comprises: mixing NiCoN and MgH2 under argon conditions with a NiCoN addition amount of 6wt%, and then performing high-energy ball milling at a ball-to-material ratio of 40:1, a ball milling speed of 400rpm, and a total ball milling time of 10h. The high-energy ball milling method is a forward and reverse ball milling method, with a single ball milling time of 12min and a ball milling interval of 6min, thereby obtaining a MgH2-based hydrogen storage material with a NiCoN addition amount of 6wt%, which is named MgH2-6NiCoN.

[0059] In order to demonstrate the hydrogen storage performance of MgH2-6NiCoN composite material, TG test and PCT test were carried out.

[0060] In order to prove the starting dehydrogenation temperature and dehydrogenation amount of the MgH2-6NiCoN composite material, the hydrogen storage material was tested by TG. The test results are as follows: Figure 3 As shown, the initial hydrogen desorption temperature of the hydrogen storage material doped with the catalyst is 164° C. and the hydrogen desorption amount is 6.12 wt %. The hydrogen desorption amount of the material shows a decreasing pattern as the doping amount increases.

[0061] In order to prove the hydrogen absorption and desorption ability of MgH2-6NiCoN composite materials at different temperatures, PCT tests were carried out on the hydrogen storage materials, such as Figure 4-7 As shown in the figure, it can be seen that MgH2-6NiCoN has excellent low-temperature hydrogen storage performance and can absorb a certain amount of hydrogen in a relatively short time. At 150°C, it can quickly absorb 5.52wt% of hydrogen in 30 minutes. At the same time, at a lower dehydrogenation temperature of 285°C, it can also release 4.98wt% of hydrogen within 30 minutes. When it reaches 300°C, it can basically achieve complete hydrogen release within 30 minutes.

[0062] In order to prove the catalytic mechanism of MgH2-6NiCoN composite material, XRD test was carried out on the hydrogen storage material after ball milling and hydrogen absorption and desorption, such as Figure 10 As shown in the figure, it can be seen that NiCoN still exists after ball milling of MgH2-6NiCoN. When hydrogen is released for the first time, NiCoN decomposes to produce Mg, Mg2Ni, and Mg2Co, and then produces MgH2, Mg2Ni4, and Mg2CoH5 after hydrogen absorption again.

[0063] In order to prove the stability of the catalytic active material of the MgH2-6NiCoN composite material, the cycle performance of the hydrogen storage material was tested. The specific test method is: the cycle performance test was carried out at 310 ° C using PCT, and the hydrogen pressure of hydrogenation was 2 MPa. The test analysis results are as follows: Figure 11 As shown, after 10 cycles, the actual hydrogen capacity of MgH2-6NiCoN remains at 5.85wt%, which is equivalent to a capacity retention rate of 96.3% compared with the first cycle capacity, indicating that MgH2-6NiCoN exhibits stable dehydrogenation and has good cycle stability.

[0064] The above TG test and PCT test results show that NiCoN as a catalyst can significantly reduce the initial hydrogen desorption temperature of MgH2 and effectively catalyze the hydrogen absorption and desorption reaction of MgH2, thereby improving the hydrogen absorption and desorption capacity.

[0065] To investigate the effect of NiCoN as a catalyst on the activation energy of MgH2 and further elucidate its catalytic mechanism, XRD patterns of dehydrogenated and rehydrogenated MgH2-6NiCoN were measured. In an argon-filled glove box, 6 wt% NiCoN powder was weighed and mixed with MgH2. The powder was then placed in a stainless steel ball mill, and stainless steel grinding balls were weighed and placed in the mill at a ball-to-material ratio of 40:1. The mill, containing the powder and stainless steel balls, was sealed and removed from the glove box. The hydrogen storage material was obtained by ball milling at 400 rpm, rotating forward and reverse for 10 hours, with 12-minute intervals and 6-minute rests. The stainless steel ball mill was then placed back into the glove box, where the milled powder was removed for testing.

[0066] In order to demonstrate the effect of NiCoN on the hydrogen storage performance of MgH2, Comparative Examples 1 and 2 are provided. In Comparative Example 1, MgH2-6NiCoN and MgH2 are used as hydrogen storage materials to compare hydrogen absorption and desorption at different temperatures, and in Comparative Example 2, MgH2-6NiCoN and MgH2 are used as hydrogen storage materials to compare activation energies. At the same time, in order to demonstrate the catalytic mechanism of NiCoN, Comparative Example 2 is provided to reveal the catalytic mechanism of NiCoN by comparing the peak positions in the XRD patterns of hydrogen absorption and desorption of the composite materials.

[0067] Comparative Example 1

[0068] A method for preparing a MgH2-6NiCoN composite material, wherein the steps not specifically described are the same as those in Example 1, and the composite material MgH2-6NiCoN and ball-milled MgH2 are subjected to PCT testing.

[0069] The PCT test results of MgH2-6NiCoN and ball-milled MgH2 are as follows Figure 4-7 As shown, the MgH2-6NiCoN composite material releases 4.96wt% of hydrogen at 285℃ in 30min and absorbs 5.52wt% of hydrogen at 150℃ in 30min, compared with the ball-milled MgH2 which releases 0.93wt% of hydrogen at 300℃ in 30min and absorbs 1.56wt% of hydrogen at 250℃ in 30min.

[0070] Comparative Example 2

[0071] A method for preparing a MgH2-6NiCoN composite material, wherein the steps not specifically described are the same as those in Example 1, and the composite material MgH2-6NiCoN and ball-milled MgH2 are subjected to DSC testing.

[0072] The DSC test results of MgH2-6NiCoN and MgH2 are as follows Figure 8-9 As shown in Figure 3, the activation energy of the MgH2-6NiCoN composite material is reduced by 71 kJ / mol compared with that of ball-milled MgH2.

[0073] Comparative Example 3

[0074] A method for preparing MgH2-6NiCoN, wherein the steps not specifically described are the same as those in Example 1, wherein the ball-milled sample and the sample subjected to hydrogen absorption and desorption after ball milling are prepared in a glove box and then taken out for XRD testing.

[0075] The XRD test results of MgH2-6NiCoN are as follows Figure 9As shown 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 reacts with Co and Ni to form Mg2Co and Mg2Ni during the dehydrogenation process. Compared with the ground MgH2-6NiCoN, the rehydrogenated MgH2-6NiCoN contains not only MgH2 but also Mg2CoH5 and Mg2NiH4, which proves that the in-situ formed Mg2Co and Mg2Ni can absorb hydrogen to form corresponding hydrides. It can be inferred that the reversible phase transition of Mg2Co / Mg2CoH5 and Mg2Ni / Mg2NiH4 plays the role of "hydrogen pump", thereby reducing the reaction activation energy and promoting the absorption and dissociation of hydrogen.

[0076] Combined with the results of Example 1, Comparative Examples 1, 2 and 3, it can be seen that there is a synergistic catalytic effect between the in-situ formed Mg2Ni and Mg2Co, NiCoN has a significant enhancing effect on the dehydrogenation / desorption kinetics of MgH2 / Mg, the MgH2-6NiCoN composite material releases 4.96 wt% of hydrogen in 30 minutes at 285°C, absorbs 4.83 wt% of H2 within 10 minutes at 150°C, and the activation energy is reduced by 71 kJ / mol compared with ball-milled MgH2. The in-situ formed Mg2Co and Mg2Ni appear in the first dehydrogenation process and are further converted into Mg2CoH5 and Mg2NiH4 after rehydrogenation. The reversible phase transition of Mg2Co / Mg2CoH5 and Mg2Ni / Mg2NiH4 accelerates the dissociation and recombination of hydrogen, thus explaining the excellent hydrogen absorption / desorption kinetics of the composite material.

Claims

1. A bimetallic nitride catalyst doped magnesium hydride hydrogen storage material for use in the field of hydrogen storage, characterized in that: The bimetallic nitride catalyst and magnesium hydride are mixed in a certain mass ratio, and ball milled under certain conditions to obtain a NiCoN catalyst-doped magnesium hydride hydrogen storage material; When the doping amount of the catalyst is 2-8 wt%, the initial hydrogen desorption temperature of the system drops to 164-185°C, and the hydrogen desorption amount reaches 6.1-6.5 wt%. During isothermal hydrogen desorption, the system can completely desorb hydrogen at 330°C, and the hydrogen desorption amount reaches 6.3-6.6 wt% within 15 minutes. During isothermal hydrogen absorption, the system can still absorb 5.2-5.8 wt% of hydrogen within 50 minutes even at a temperature as low as 150°C. The catalyst comprises elements Ni, Co and N, and is in the shape of nanoflowers.

2. The use of the bimetallic nitride catalyst doped magnesium hydride hydrogen storage material according to claim 1 as a hydrogen storage material, characterized in that: The ball milling conditions are as follows: argon as the protective atmosphere, a ball-to-material ratio of 40:1, a ball milling speed of 400-450 r / min, and a ball milling time of 10-12 h.

3. The use of the bimetallic nitride catalyst doped magnesium hydride hydrogen storage material according to claim 1 as a hydrogen storage material, characterized in that: After cyclic use, the sample showed good hydrogen storage reversibility and stable cyclability. After 10 cycles, the actual hydrogen capacity retention rate was equivalent to 96% of the first cycle capacity.

4. The use of the bimetallic nitride catalyst doped magnesium hydride hydrogen storage material according to claim 1 as a hydrogen storage material, characterized in that: The preparation method of the bimetallic nitride catalyst comprises the following steps: Step 1) Ni(NO3)2·6H2O and CoSO4·7H2O were dissolved in deionized water and magnetically stirred. Then, ammonium fluoride and urea were added to the above solution in sequence and stirred continuously. After complete dissolution, the solution was transferred to an autoclave and kept warm for a period of time. After cooling naturally to room temperature, the hydrothermal sample sediment was collected. Step 2), washing the precipitate several times with deionized water, collecting the precipitate after centrifugation, and then vacuum drying overnight, then transferring the urea and the dried precipitate into a tube furnace in sequence, calcining them under a flowing argon gas flow for a period of time, and naturally cooling to room temperature. After that, the sample was collected and transferred to a glove box filled with Ar, thereby obtaining the bimetallic nitride catalyst NiCoN.

5. The use of the bimetallic nitride catalyst doped magnesium hydride hydrogen storage material according to claim 4 as a hydrogen storage material, characterized in that: In the step 1), Ni(NO3)2·6H2O is 1 mmol, CoSO4·7H2O is 1 mmol, H2O is 30 mL, ammonium fluoride is 5 mmol, and urea is 10 mmol. The magnetic stirring time is between 30 and 60 minutes. The Ni(NO3)2·6H2O, CoSO4·7H2O, NH4F, and urea are added dropwise in sequence and slowly. The autoclave is kept at 100°C for 8 hours. In the step 2), the washing conditions are washing with deionized water and centrifuging 6-8 times, the centrifugal speed is 8000-9000 rpm, and the centrifugal time is 5-10 min. The drying conditions are drying at 60-100° C. for 10 h. The calcination conditions are calcining at 450° C. under argon for 2-3 h.

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