Ni / VC-MgH2 composite hydrogen storage material and preparation method thereof

Abstract

The invention discloses a Ni / VC-MgH2 composite hydrogen storage material. The Ni / VC-MgH2 composite hydrogen storage material is prepared by mixing and mechanically ball-milling MgH2 and Ni / VC generated by calcining. The Ni / VC raw material is prepared by fully grinding dicyandiamide, nickel nitrate hexahydrate and ammonium metavanadate and then carrying out high-temperature calcination, wherein the doping amount of Ni / VC accounts for 5-10wt% of the total mass of the composite material. The preparation method comprises the following steps: 1) preparing a Ni / VC material; and (2) preparing the Ni / VC-MgH2 composite hydrogen storage material. The Ni / VC-MgH2 composite hydrogen storage material and the preparation method thereof provided by the invention have the following advantages: 1) the dynamic performance of hydrogen absorption and desorption is good; 2) the hydrogen storage capacity is high; and 3) the preparation process is simple and the cost is low.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogen storage materials for new energy materials, and particularly relates to a Ni / VC-MgH2 composite hydrogen storage material and a preparation method thereof. Background Art

[0002] Energy is a major issue for the future social transformation, and traditional fossil energy is limited. Therefore, it is urgent to find new energy for sustainable development. For green and sustainable development, we have developed tidal energy, wind energy, solar energy, etc. to convert the advantages of the natural environment into the energy we need. However, these energies have high requirements for the regional environment. Hydrogen energy has become one of the most popular alternative energies due to its abundant raw material sources, high energy density, green pollution-free, and renewable characteristics. To meet the future development needs, breakthroughs are being sought in the three major difficulties of hydrogen production, storage, and transportation. Among them, how to store hydrogen efficiently and safely has become the most commercially valuable research topic. Hydrogen storage is divided into three methods: liquid hydrogen storage, solid hydrogen storage, and gaseous hydrogen storage. Solid hydrogen storage has the advantages of good stability and relatively high hydrogen storage density compared with other hydrogen storage methods, and is the most likely hydrogen storage method to be commercialized in the future.

[0003] The hydrogen storage capacity of MgH2 is 7.6 wt%, which is currently recognized as the most promising solid hydrogen storage material. However, its use on a large scale is restricted by its slow kinetics and thermodynamically stable characteristics. At present, in order to improve the kinetics and thermodynamic properties of MgH2, researchers have conducted long-term exploration and found that the performance can be improved by means of nanosizing, doping modification, composite systems, etc. Among them, the doping modification method is the most effective way at present. Transition metals or transition metal compounds (Ni, Co, Fe, etc.) are added as catalysts to promote the adsorption and desorption of hydrogen atoms by changing the reaction path and reduce the reaction energy barrier to achieve performance improvement.

[0004] According to the Ni3ZnC prepared by Zhang et al. 0.7 / Ni and carbon nanotube composites, when tested for isothermal dehydrogenation at 673 K with 5 wt% doping of the catalyst, it takes 150 s to achieve a hydrogen release amount of 5.95 wt%, effectively improving the dehydrogenation kinetics. [Zhang B, Xie X, Wang Y, et al. In situ formation of multiple catalysts for enhancing the hydrogen storage of MgH2 by adding porous Ni3ZnC 0.7 / Ni-loaded carbon nanotube microspheres[J].Journal of Magnesium and Alloys,2024,12(3):1227-1238.] Among them, the addition of carbon nanotubes restricts the aggregation and growth of active nanomaterial particles and enhances the activity of Ni. However, the disadvantage of this composite structure is its dependence on physical mixing and the relatively weak interfacial interaction.

[0005] Heterojunction catalysts have received extensive attention in recent years due to their unique structures. By adjusting the electronic structure and surface properties through interface engineering, the catalytic performance can be enhanced. For example, the V2O3-TiO2-rGO ternary heterojunction catalyst prepared by Liu et al. achieved a reduction in the initial dehydrogenation temperature of MgH2 to 205 °C, and the dehydrogenation activation energy was reduced by 65.40% compared to pure MgH2. [Liu Z, Ning H, Liu R, et al. Fabrication of V2O3-TiO2-rGO ternary heterojunction composite to enhance the hydrogen storage performance of MgH2[J]. Chemical Engineering Journal,2024,499155877-155877.] This heterojunction catalyst utilizes the synergistic interaction between components within the heterogeneous material, efficiently utilizes the catalytic effect of the catalyst, and promotes the diffusion and transfer of hydrogen atoms. However, the experimental preparation process is complex and the preparation cost is high.

[0006] In summary, the Ni / VC heterojunction catalyst proposed in this patent is further improved based on the above problems. On the basis of effectively reducing the kinetic energy barrier by doping transition metals to achieve a reduction in the reversible hydrogen absorption and desorption temperature of MgH2, the preparation method is simple, and it has high interfacial activity and excellent stability, greatly promoting the diffusion and desorption process of hydrogen atoms. It is of great significance for the future development of the application of heterojunction catalysts in the field of hydrogen storage. Summary of the Invention

[0007] The objective of this invention patent is to provide a Ni / VC-MgH2 hydrogen storage composite material and its preparation method.

[0008] Through research by the inventors, it was found that: when the Ni / VC composite material is prepared into a heterostructure, forming a tight interfacial contact and promoting electron transfer, it can accelerate the formation of H2 molecules and achieve an improvement in the hydrogen absorption and desorption performance of MgH2.

[0009] On this basis, the inventors adjusted the Ni / VC-MgH₂ composite hydrogen storage material provided by the present invention, effectively enhancing the hydrogen absorption and desorption performance of the MgH₂ hydrogen storage material, and achieving the following three technical effects at the same time:

[0010] 1. Lower the initial dehydrogenation temperature during the dehydrogenation process;

[0011] 2. Release more hydrogen during the entire dehydrogenation process by reducing the amount of catalyst added, and the final dehydrogenation amount reaches 6.98 wt%;

[0012] 3. Absorb more hydrogen at low temperature during the entire hydrogen absorption process by reducing the amount of catalyst added, and the hydrogen absorption amount reaches 6.60 wt% at 125 °C finally.

[0013] To achieve the above-mentioned invention purpose, the technical solution adopted by the present invention is as follows:

[0014] A Ni / VC-MgH₂ composite hydrogen storage material is prepared by mechanically ball-milling MgH₂ and Ni / VC. The microscopic morphology of the Ni / VC catalyst is Ni / VC nanoparticles dispersed on carbon nanosheets.

[0015] The addition amount of the Ni / VC accounts for 5-10 wt% of the total mass.

[0016] The preparation method of the Ni / VC-MgH₂ composite hydrogen storage material includes the following steps:

[0017] Step 1) Preparation of the Ni / VC composite material. Weigh dicyandiamide, ammonium metavanadate and nickel nitrate hexahydrate in a certain molar ratio, add dicyandiamide, ammonium metavanadate and nickel nitrate hexahydrate into a mortar, grind and mix evenly, and then carry out high-temperature calcination under a certain atmosphere to obtain Ni / VC;

[0018] Preferably, the molar ratio of dicyandiamide, ammonium metavanadate and nickel nitrate hexahydrate in step 1 is 18:3:1;

[0019] Preferably, the calcination conditions in step 1 are a nitrogen environment, a heating rate of 3-8 °C / min, a calcination temperature of 500-900 °C, and a calcination time of 2-4 h;

[0020] Step 2) Preparation of the Ni / VC-MgH₂ composite hydrogen storage material. Use the Ni / VC composite material obtained in step 1 with a certain mass fraction, and under certain conditions, ball-mill Ni / VC and MgH₂ to obtain the Ni / VC-MgH₂ composite hydrogen storage material.

[0021] Preferably, the mass fraction of Ni / VC in step 2 is that the addition amount accounts for 5-10 wt% of the total mass;

[0022] Preferably, the conditions for ball milling in step 2 are under the protection of argon atmosphere, the ball-to-material ratio is (30 - 90):1, the rotation speed of ball milling is 400 - 550 rpm, and the ball milling time is 10 - 20 h.

[0023] The application of Ni / VC-MgH2 composite hydrogen storage material in the field of hydrogen storage,

[0024] When the doping amount of the catalyst is 5 wt%, the hydrogen release temperature of the system drops to 216 °C, and the hydrogen release amount reaches 7.00 wt%;

[0025] When the doping amount of the catalyst is 7 wt%, the hydrogen release temperature of the system drops to 185 °C, and the hydrogen release amount reaches 6.98 wt%.

[0026] When the doping amount of the catalyst is 10 wt%, the hydrogen release temperature of the system drops to 178 °C, and the hydrogen release amount reaches 6.76 wt%.

[0027] In order to prove the successful preparation of the Ni / VC composite material, X-ray diffraction test was carried out on it, and the results are as Figure 1 shown. The obtained diffraction peaks of Ni appear at 44.49°, 51.84°, and 76.38°, corresponding to the (111), (200), and (220) crystal planes respectively. The diffraction peaks of VC appear at 37.36°, 43.41°, 63.08°, and 79.68°, corresponding to the (111), (200), (220), and (222) crystal planes respectively, indicating the successful preparation of the Ni / VC composite material.

[0028] In order to prove the structural characteristics of the Ni / VC composite material, through transmission electron microscope test, the morphology of the sample prepared by the present invention is the dispersed Ni / VC nanoparticles on the carbon nanosheets.

[0029] In order to prove the influence of the addition amount of the Ni / VC composite material as a catalyst on the hydrogen absorption and desorption performance of MgH2, Ni / VC-MgH2 composite hydrogen storage materials with Ni / VC contents of 5 wt%, 7 wt%, and 10 wt% were prepared respectively, and their temperature-rising dehydrogenation tests were carried out. It was confirmed that the initial hydrogen release temperature of the MgH2 composite material added with Ni / VC is 216 - 178 °C, which is 79 - 117 °C lower than that of pure MgH2, and the total hydrogen release amount reaches 6.76 - 7.00 wt%.

[0030] Therefore, compared with the prior art, the present invention has the following advantages:

[0031] 1. The Ni / VC material prepared by the present invention effectively improves the hydrogen desorption performance of MgH2, has a lower initial hydrogen desorption temperature, and a small amount of catalyst addition results in a high final hydrogen desorption amount. When the doping amount of Ni / VC is 7 wt%, the initial hydrogen desorption temperature drops to 185 °C, and the final hydrogen desorption amount reaches 6.98 wt%. Rapid hydrogen absorption is achieved at 175 °C, and the hydrogen absorption amount within 20 s reaches 5.70 wt%, and its hydrogen absorption and desorption performance has been greatly improved;

[0032] 2. The method used for the Ni / VC composite material prepared by the present invention has the advantages of low cost and simple preparation process. Brief Description of the Drawings

[0033] Figure 1 XRD pattern of the prepared Ni / VC composite material in Specific Embodiment 1 of the present invention;

[0034] Figure 2 TEM image of the prepared Ni / VC composite material in Specific Embodiment 1 of the present invention;

[0035] Figure 3 Dehydrogenation curves of MgH2 composite hydrogen storage materials doped with Ni / VC contents of 5 wt%, 7 wt%, and 10 wt% in Specific Embodiments 1-3 of the present invention;

[0036] Figure 4 Dehydrogenation curves of MgH2 composite hydrogen storage materials doped with 7 wt% Ni, 7 wt% VC, and 7 wt% Ni / VC in Specific Embodiment 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 of the present invention;

[0037] Figure 5 Isothermal dehydrogenation curves of MgH2-7 wt% Ni / VC composite hydrogen storage material at 275 °C, 300 °C, 325 °C, and 350 °C in Specific Embodiment 1 of the present invention;

[0038] Figure 6 Isothermal hydrogen absorption curves of MgH2-7 wt% Ni / VC composite hydrogen storage material at 100 °C, 125 °C, 150 °C, and 175 °C in Specific Embodiment 1 of the present invention.

[0039] Figure 7 Isothermal dehydrogenation curves of MgH2 hydrogen storage material at 300 °C, 325 °C, and 350 °C in Specific Comparative Example 1 of the present invention;

[0040] Figure 8 Isothermal hydrogen absorption curves of MgH2 hydrogen storage material at 200 °C, 250 °C, and 300 °C in Specific Comparative Example 1 of the present invention. Detailed Description of the Invention

[0041] The present invention will be further described in detail with reference to the accompanying drawings of the specification through embodiments, but it is not a limitation of the present invention.

[0042] Example 1

[0043] A preparation method of a Ni / VC-MgH2 composite hydrogen storage material includes the following steps:

[0044] Step 1) Preparation of Ni / VC composite material: With the molar ratio of dicyandiamide, ammonium metavanadate and nickel nitrate hexahydrate being 18:3:1, put them into a mortar and grind and mix evenly. Then, heat the obtained mixed sample to 900°C at a heating rate of 5°C / min under a nitrogen atmosphere, and the calcination time is 3h, thus obtaining the Ni / VC composite material;

[0045] Step 2) Preparation of Ni / VC-MgH2 composite hydrogen storage material: Weigh 0.035g of the Ni / VC obtained in Step 1 and 0.465g of MgH2, and carry out ball milling under the conditions of an argon protective atmosphere, a ball-to-material ratio of 80:1, a ball milling speed of 450rpm, and a ball milling time of 15h, thus obtaining a MgH2 composite hydrogen storage material with a Ni / VC doping amount of 7wt%.

[0046] To prove the successful preparation of the Ni / VC composite material, the results are as Figure 1 shown. Diffraction peaks of Ni appear at 44.49°, 51.84°, and 76.38° in the obtained spectrum, corresponding to the (111), (200), and (220) crystal planes respectively. Diffraction peaks of VC appear at 37.36°, 43.41°, 63.08°, and 79.68°, corresponding to the (111), (200), (220), and (222) crystal planes respectively, indicating the successful preparation of the Ni / VC composite material.

[0047] To prove the structural characteristics of Ni / VC, through transmission electron microscope testing, the results are as Figure 2 shown. The structure of the material prepared in the present invention is dispersed Ni / VC nanoparticles on carbon nanosheets.

[0048] Perform a temperature-rising dehydrogenation test on the obtained MgH2 composite hydrogen storage material with a Ni / VC content of 7wt%. The test method is as follows: Weigh an appropriate amount of the sample (60 - 150mg), and heat it to 400°C at a heating rate of 3°C / min, and the hydrogen release amount is 6.98wt%.

[0049] Perform an isothermal dehydrogenation test on the obtained MgH2 hydrogen storage material with a Ni / VC content of 7wt%. As Figure 5 shown, first evacuate it to 0.001Bar, wait until it is heated to the target temperature, and after constant temperature and stabilization, open the sample valve to obtain the maximum hydrogen release amount within 2500s.

[0050] After heating to 275 °C and stabilizing at a constant temperature, the sample valve was opened, and the maximum hydrogen release amount within 2500 s was 6.78 wt%, and the hydrogen release amount reached 6.00 wt% within 620 s;

[0051] After heating to 300 °C and stabilizing at a constant temperature, the sample valve was opened, and the maximum hydrogen release amount within 2500 s was

[0052] 6.8 wt%, and the hydrogen release amount reached 6.64 wt% within 350 s;

[0053] After heating to 325 °C and stabilizing at a constant temperature, the sample valve was opened, and the maximum hydrogen release amount within 2500 s was 6.90 wt%, and the hydrogen release amount reached 6.70 wt% within 160 s;

[0054] After heating to 350 °C and stabilizing at a constant temperature, the sample valve was opened, and the maximum hydrogen release amount within 2500 s was 6.92 wt%, and the hydrogen release amount reached 6.81 wt% within 150 s.

[0055] The obtained MgH₂ hydrogen storage material with a Ni / VC content of 7 wt% was subjected to an isothermal hydrogen absorption test. As Figure 6 shown, the initial hydrogen pressure was 30 Bar. After heating to the target temperature and stabilizing at a constant temperature, the sample valve was opened to obtain the isothermal maximum hydrogen absorption amount within 1700 s.

[0056] After heating to 100 °C and stabilizing at a constant temperature, the sample valve was opened, and the maximum hydrogen absorption amount within 1700 s was 6.00 wt%;

[0057] After heating to 125 °C and stabilizing at a constant temperature, the sample valve was opened, and the maximum hydrogen absorption amount within 1700 s was 6.60 wt%, and the hydrogen absorption amount reached 5.09 wt% within 400 s;

[0058] After heating to 150 °C and stabilizing at a constant temperature, the sample valve was opened, and the maximum hydrogen absorption amount within 1700 s was 6.82 wt%, and the hydrogen absorption amount reached 6.06 wt% within 400 s;

[0059] After heating to 175 °C and stabilizing at a constant temperature, the sample valve was opened, and the maximum hydrogen absorption amount within 1700 s was 6.92 wt%, and the hydrogen absorption amount reached 5.70 wt% within 20 s.

[0060] To prove the influence of Ni / VC as a catalyst on the hydrogen absorption and desorption performance of MgH₂, a MgH₂ hydrogen storage material with a Ni / VC content of 0 wt% was prepared through Comparative Example 1.

[0061] Comparative Example 1

[0062] A preparation method of a MgH2 hydrogen storage material without adding Ni / VC content, that is, a MgH2 hydrogen storage material with a Ni / VC content of 0 wt%, the steps not specifically described are the same as those in Example 1. The difference lies in that in step 2, no Ni / VC is added, that is, only 0.5 g of MgH2 is weighed.

[0063] The obtained MgH2 hydrogen storage material with a Ni / VC content of 0 wt% was subjected to a temperature-rising dehydrogenation test. The test method was the same as that in Example 1, and the test results are as Figure 3 shown. Its initial hydrogen release temperature was 295 °C, and the hydrogen release amount was 7.42 wt% when the temperature was raised to 400 °C.

[0064] The obtained MgH2 hydrogen storage material with a Ni / VC content of 0 wt% was subjected to an isothermal dehydrogenation test. As Figure 7 shown, it was first evacuated to 0.001 Bar. After the temperature was raised to the target temperature and stabilized at a constant temperature, the sample valve was opened to obtain the maximum hydrogen release amount within 3500 s.

[0065] When the temperature was raised to 300 °C and stabilized at a constant temperature, the sample valve was opened, and the maximum hydrogen release amount within 3500 s was 6.94 wt%, and the hydrogen release amount within 2000 s was 6.55 wt%;

[0066] When the temperature was raised to 325 °C and stabilized at a constant temperature, the sample valve was opened, and the maximum hydrogen release amount within 3500 s was 7.13 wt%, and the hydrogen release amount within 900 s was 6.48 wt%;

[0067] When the temperature was raised to 350 °C and stabilized at a constant temperature, the sample valve was opened, and the maximum hydrogen release amount within 3500 s was 7.32 wt%, and the hydrogen release amount within 400 s was 6.91 wt%.

[0068] The obtained MgH2 hydrogen storage material with a Ni / VC content of 0 wt% was subjected to an isothermal hydrogen absorption test. As Figure 8 shown, the initial hydrogen pressure was 30 Bar. After the temperature was raised to the target temperature and stabilized at a constant temperature, the sample valve was opened to obtain the maximum isothermal hydrogen absorption amount within 2500 s.

[0069] When the temperature was raised to 200 °C and stabilized at a constant temperature, the sample valve was opened, and the maximum hydrogen absorption amount within 2500 s was 4.83 wt%;

[0070] When the temperature was raised to 250 °C and stabilized at a constant temperature, the sample valve was opened, and the maximum hydrogen absorption amount within 2500 s was 7.03 wt%, and the hydrogen absorption amount within 700 s was 5.43 wt%;

[0071] When the temperature was raised to 300 °C and stabilized at a constant temperature, the sample valve was opened, and the maximum hydrogen absorption amount within 2500 s was 7.33 wt%, and the hydrogen absorption amount within 200 s was 6.36 wt%.

[0072] From the comparison between Example 1 and Comparative Example 1, it can be seen that as a catalyst, Ni / VC reduces the initial dehydrogenation temperature of MgH2 from 295 °C to 185 °C. Under the same dehydrogenation conditions, in Example 1, the hydrogen release amount at 350 °C within 150 s is 6.80 wt%, while in Comparative Example 1, the hydrogen release amount within 150 s is 2.11 wt%. Under the same hydrogen absorption conditions, in Example 1, the hydrogen absorption amount within 20 s at 175 °C is 5.70 wt%, while in Comparative Example 1, the hydrogen absorption amount within 20 s at 200 °C is 0.18 wt%. Therefore, the addition of the Ni / VC catalyst greatly improves the performance of the MgH2 hydrogen storage material.

[0073] To prove the effect of Ni on the dehydrogenation performance of MgH2, a Ni-doped MgH2 composite hydrogen storage material was prepared through Comparative Example 2.

[0074] Comparative Example 2

[0075] A method for preparing a MgH2 composite hydrogen storage material with an added Ni content, that is, a method for preparing a MgH2 composite hydrogen storage material with a Ni content of 7 wt%. The steps not specifically described are the same as those in Example 1. The difference lies in that in Step 1, the molar ratio of dicyandiamide to nickel nitrate hexahydrate is 18:1; in Step 2, Ni / VC is not added, that is, only 0.035 g of Ni and 0.465 g of MgH2 are weighed.

[0076] The obtained MgH2 composite hydrogen storage material with a Ni content of 7 wt% was subjected to a temperature-rising dehydrogenation test. The test method was the same as that in Example 1, and the test results are as Figure 4 shown. Its initial dehydrogenation temperature is 193 °C, and the hydrogen release amount is 6.90 wt% when the temperature is raised to 400 °C.

[0077] From the comparison between Example 1 and Comparative Example 2, it can be seen that the initial dehydrogenation temperature of the MgH2 composite hydrogen storage material doped with Ni / VC is reduced from 193 °C to 185 °C.

[0078] To prove the effect of VC as a catalyst on the hydrogen absorption and dehydrogenation performance of MgH2, a MgH2 composite hydrogen storage material with a VC content of 7 wt% was prepared through Comparative Example 3.

[0079] Comparative Example 3

[0080] A method for preparing a MgH2 composite hydrogen storage material with an added VC content, that is, a method for preparing a MgH2 composite hydrogen storage material with a VC content of 7 wt%. The steps not specifically described are the same as those in Example 1. The difference lies in that in Step 1, the molar ratio of dicyandiamide to ammonium metavanadate is 6:1; in Step 2, VC is added, that is, only 0.035 g of VC and 0.465 g of MgH2 are weighed.

[0081] The obtained MgH₂ composite hydrogen storage material with a VC content of 7 wt% was subjected to a temperature-rising dehydrogenation test. The test method was the same as that in Example 1, and the test results were as follows: Figure 4 As shown, its initial dehydrogenation temperature was 202 °C, and the hydrogen release amount was 6.83 wt% when the temperature was raised to 400 °C.

[0082] To obtain the optimal doping amount of Ni / VC in the MgH₂ hydrogen storage material, Ni / VC-MgH₂ composite hydrogen storage materials with Ni / VC contents of 5 and 10 wt% were prepared through Examples 2 and 3 respectively.

[0083] Example 2

[0084] A preparation method of a Ni / VC-MgH₂ composite hydrogen storage material (with a Ni / VC content of 5 wt%). The steps not specifically described were the same as those in Example 1. The difference was that in Step 2, the addition amount of Ni / VC was 5 wt%. In a glove box under an argon atmosphere, 0.025 g of Ni / VC and 0.475 g of MgH₂ were weighed respectively.

[0085] The obtained MgH₂ composite hydrogen storage material with a Ni / VC content of 5 wt% was subjected to a temperature-rising dehydrogenation test. The test method was the same as that in Example 1, and the test results were as follows: Figure 3 As shown, its initial dehydrogenation temperature was 216 °C, and the hydrogen release amount was 7.00 wt% when the temperature was raised to 400 °C.

[0086] Example 3

[0087] A preparation method of a Ni / VC-MgH₂ composite hydrogen storage material (with a Ni / VC content of 10 wt%). The steps not specifically described were the same as those in Example 1. The difference was that in Step 2, the addition amount of Ni / VC was 10 wt%. In a glove box under an argon atmosphere, 0.050 g of Ni / VC and 0.450 g of MgH₂ were weighed respectively.

[0088] The obtained MgH₂ composite hydrogen storage material with a Ni / VC content of 10 wt% was subjected to a temperature-rising dehydrogenation test. The test method was the same as that in Example 1, and the test results were as follows: Figure 3 As shown, its initial dehydrogenation temperature was 178 °C, and the hydrogen release amount was 6.76 wt% when the temperature was raised to 400 °C.

[0089] Therefore, the MgH₂ composite hydrogen storage material with a Ni / VC content of 7 wt% had the best comprehensive hydrogen release performance. The test results were as follows: Figure 3 As shown, its initial dehydrogenation temperature was 185 °C, which was 110 °C lower than that of MgH₂, and the hydrogen release amount was 6.98 wt% when the temperature was raised to 400 °C.

[0090] The above are only embodiments of the present invention, and common general technical solutions and / or characteristics in the solutions are not described in detail again. It should be noted that for those skilled in the art, without departing from the technical solutions of the present invention, several modifications and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the implementation effect of the present invention and the practicability of the patent. The protection scope required by this application shall be subject to the content of its claims, and the specific implementation manners and the like recorded in the specification can be used to interpret the content of the claims.

Claims

1. A Ni / VC-MgH2 composite hydrogen storage material, characterized in that: The product is prepared by mechanically milling MgH2 and Ni / VC in a planetary ball mill with a ball-to-material ratio of (30-90):

1. The milling is carried out for 10-20 hours under the protection of an argon atmosphere. The Ni / VC is prepared by fully grinding dicyandiamide, ammonium metavanadate and nickel nitrate hexahydrate and then calcining them at a high temperature under a nitrogen atmosphere.

2. The Ni / VC-MgH2 composite hydrogen storage material according to claim 1, characterized in that: The addition amount of Ni / VC accounts for 5-10wt% of the total mass.

3. The method for preparing the Ni / VC-MgH2 composite hydrogen storage material according to claim 1, comprising the following steps: Step 1) Preparation of Ni / VC composite material: Dicyandiamide, ammonium metavanadate and nickel nitrate hexahydrate are weighed in a certain molar ratio, mixed and ground, and then calcined at a high temperature under certain conditions to obtain Ni / VC; Step 2) Preparation of Ni / VC-MgH2 composite hydrogen storage material: The Ni / VC composite material obtained in step 1 is subjected to ball milling with Ni / VC and MgH2 under certain conditions to obtain a Ni / VC-MgH2 composite hydrogen storage material.

4. The preparation method according to claim 3, characterized in that: The molar ratio of step 1 is dicyandiamide:ammonium metavanadate:nickel nitrate hexahydrate=18:3:1, the molar weight of dicyandiamide is 18 mmol, the molar weight of ammonium metavanadate is 3 mmol, and the molar weight of nickel nitrate hexahydrate is 1 mmol.

5. The preparation method according to claim 3, characterized in that: The grinding time in step 1 is 10-30 minutes, the calcination environment is a nitrogen atmosphere, and the calcination temperature is 500-900°C.

6. The preparation method according to claim 3, characterized in that: The mass fraction of the Ni / VC composite material in step 2 is 5-10wt% of the total mass; the ball milling conditions are: argon as the protective atmosphere, a ball-to-material ratio of (30-90):1, a ball milling speed of 400-550rpm, and a ball milling time of 10-20h.

7. Use of the Ni / VC-MgH2 composite hydrogen storage material according to claim 1 in the field of hydrogen storage, characterized in that: When the catalyst doping amount is 7 wt %, the initial hydrogen desorption temperature of the system drops to 185° C., and the hydrogen desorption amount reaches 6.98 wt %.

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