A solid-state magnesium-based hydrogen storage material MgH 2 -CrOOH@CNT and its preparation method

Abstract

The present invention belongs to the technical field of hydrogen storage materials, and relates to a solid-state magnesium-based hydrogen storage material MgH2-CrOOH@CNT and a preparation method thereof. In the present invention, a novel carbon nanotube loaded with CrOOH nanoparticles is used as a catalytic material, and is ball-milled and mixed with MgH2 to prepare the magnesium-based hydrogen storage material MgH2-CrOOH@CNT. The present invention uses a simple process and mild conditions to prepare a high-performance CrOOH@CNT catalyst for catalyzing the hydrogen storage of MgH2. Finally, the hydrogen absorption and desorption temperature of the prepared composite material is greatly reduced compared with that of pure MgH2, achieving the common optimization and improvement of hydrogen absorption and desorption kinetics and the total amount of hydrogen absorption and desorption. At the same time, the effect of hydrogen absorption at room temperature can be achieved, and it has excellent hydrogen storage performance and broad commercial application prospects. Moreover, the preparation process of the present invention has low requirements for equipment and is easy to implement, and can be applied to industrial large-scale production.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydrogen storage materials in the field of hydrogen energy, and mainly relates to a solid-state magnesium-based hydrogen storage material MgH 2 -CrOOH@CNT composite hydrogen storage material and its preparation method. Background Technique

[0002] Energy is the basis for human survival and development. With the gradual depletion of traditional fossil energy and the increasingly deteriorating environment, people's demand for new energy is increasing day by day. Compared with fossil energy, hydrogen energy has many advantages such as cleanness, pollution-free, and renewable. However, how to store hydrogen for transportation and use is a major problem. Solid-state hydrogen storage has a higher volumetric hydrogen storage capacity and better safety compared to gaseous and liquid hydrogen storage. Among them, MgH 2 Solid-state hydrogen storage materials have a high theoretical hydrogen storage capacity, good reversible cycling performance, and magnesium also has the advantages of rich resource storage, low price, and environmental compatibility. However, at the same time, it also has the disadvantages of high thermodynamic stability and kinetic barriers. The working temperature of magnesium hydride for reversible hydrogen storage is close to 400 °C, which hinders its commercial application in on-vehicle hydrogen storage. Based on this, researchers in the field have modified magnesium hydride through alloying, nanosizing, compounding, and doping catalysis.

[0003] Currently, doping with a small amount of catalyst has become the most popular method. The catalyst can promote the dissociation of hydrogen molecules, provide active sites for the nucleation of Mg / MgH 2 , provide H diffusion channels, inhibit particle agglomeration, etc. Therefore, catalysis is an effective method to improve the hydrogen absorption and desorption kinetic performance of MgH 2 . Transition metals (TMs) and related derivative catalysts are the most typical representatives. Since individual nano-catalysts face the problem of agglomeration, transition metal-based catalysts are usually loaded on various carbon materials, such as graphene, carbon spheres, carbon fibers, and carbon nanotubes. Carbon materials can not only disperse the catalyst but also help to ball-mill and disperse the entire hydrogen storage system, preventing the agglomeration of MgH 2 . Currently, common catalyst doping modifications include doping with metals such as nickel and titanium supported on carbon materials. Although the hydrogen storage performance of magnesium-based hydrogen storage materials has been improved to a certain extent, there are still problems such as the hydrogen absorption and desorption temperature being much higher than the practical application temperature, or the hydrogen absorption and desorption reaction efficiency being low at low temperatures. It is still difficult to achieve the effect of room-temperature hydrogen absorption, and the material cost is relatively high and the preparation is relatively troublesome.

[0004] Currently, there is little research on using Cr-containing substances as catalysts for doping hydrogen storage materials in the field. In the existing related reports, the improvement effect on the hydrogen storage performance of hydrogen storage materials is not very ideal. For example, currently there is Cr 2 O 3Applications in magnesium hydride hydrogen storage, however, the hydrogen absorption and desorption temperatures are still greater than 300 °C, and the excessively high hydrogen absorption and desorption temperatures are far from the requirements of actual applications. Therefore, the present invention proposes a novel solid-state magnesium-based hydrogen storage material MgH 2 -CrOOH@CNT and its preparation method. CrOOH@CNT is a novel carbon material supported transition metal-based catalyst, and there are no relevant research reports on the catalytic modification of magnesium-based hydrogen storage materials by CrOOH@CNT. The present invention uses CrOOH@CNT doping to catalyze the Mg / MgH 2 system, enabling magnesium hydride to rapidly desorb hydrogen at 200 °C and absorb 4.8 wt% hydrogen at room temperature (pure magnesium hydride hardly absorbs hydrogen at low temperatures), greatly reducing its initial hydrogen desorption temperature and significantly improving the efficiency of hydrogen absorption and desorption conversion at low temperatures, and being able to achieve the effect of hydrogen absorption at room temperature, developing a high-efficiency hydrogen storage composite material with excellent low-temperature hydrogen storage performance and high hydrogen storage capacity. Summary of the Invention

[0005] The purpose of the present invention is to solve the problems existing in the prior art, such as the high initial hydrogen desorption temperature of MgH 2 and the low efficiency of hydrogen absorption reaction at low temperatures, and to provide a solid-state magnesium-based hydrogen storage material MgH 2 -CrOOH@CNT and its preparation method.

[0006] To achieve the above purpose, the technical solutions adopted by the present invention are as follows:

[0007] The present invention provides a preparation method of a solid-state magnesium-based hydrogen storage material MgH 2 -CrOOH@CNT, and the method steps include: mixing and ball-milling the CrOOH@CNT material with MgH 2 to obtain the solid-state magnesium-based hydrogen storage material MgH 2 -CrOOH@CNT, and the CrOOH@CNT material is a carbon nanotube CNT supported CrOOH nanoparticle catalytic material.

[0008] Preferably, the CrOOH@CNT material accounts for 0.1% - 20% of the total mass of the composite material, and more preferably 5% - 15%; the composite material includes the CrOOH@CNT material and MgH 2 .

[0009] Preferably, CrOOH in the CrOOH@CNT material is in the form of nanoparticles and is supported on the carbon nanotube CNT. More preferably, the diameter of the carbon nanotube is about 70 - 90 nm, and the particle size of CrOOH is about 40 - 60 nm.

[0010] Preferably, the CrOOH@CNT material is prepared from a chromium source and carbon nanotubes (CNT) by a hydrothermal method; more preferably, the chromium source is chromium nitrate nonahydrate, and more preferably, the chromium source accounts for 5%-90% of the total mass of the chromium source and CNT, and more preferably 30%-80%.

[0011] More preferably, the specific process for synthesizing the CrOOH@CNT material by the hydrothermal method includes: adding chromium nitrate nonahydrate as the chromium source and carbon nanotubes into water to form a uniform dispersion, carrying out a hydrothermal reaction on the dispersion in a sealed autoclave, and the product after the reaction is CrOOH@CNT nanometer powder, and the product can also be subjected to post-treatment steps such as washing and drying. More preferably, the temperature of the hydrothermal reaction is 200±10°C, and the reaction time is 24±4h. More preferably, the drying temperature is 80°C and the time is 24h.

[0012] More specifically, dissolve 0.1-0.9 g of Cr(NO) 3 ·9H 2 O in 20 ml of deionized water, and then add 0.1-0.9 g of carbon nanotubes to this solution. Ultrasonically disperse the mixture for half an hour, and then magnetically stir for half an hour, and repeat this several times alternately to obtain a uniform dispersion, and then react the mixture in a high-pressure reaction kettle at 200±10°C for 24±4h. After the reaction, the precipitate obtained by filtration or centrifugation is CrOOH@CNT nanometer powder.

[0013] Preferably, the ball milling includes: under a protective atmosphere, the ball-to-material ratio is 40-80:1, ball milling is adopted, the ball milling time is 12-48h, and the revolution speed of the ball mill is not less than 300 rpm, and more preferably it can be 300-500 rpm. More preferably, the protective atmosphere is at least one of argon, helium, nitrogen, and hydrogen. A protective atmosphere such as hydrogen helps to further avoid unnecessary decomposition during the ball milling process; more preferably, the ball milling beads used are stainless steel balls, and the size of the ball milling beads has little effect on the product, but the diameter range of 5-16 mm can be preferably selected.

[0014] The present invention also provides a solid-state magnesium-based hydrogen storage material MgH 2 -CrOOH@CNT prepared by the above preparation method. The hydrogen storage material can quickly absorb and release hydrogen at low temperature and can achieve the effect of hydrogen absorption at room temperature.

[0015] The present invention uses a carbon nanotube CrOOH@CNT material loaded with CrOOH nanoparticles as a catalytic material, and obtains a solid-state magnesium-based hydrogen storage material MgH 2 by mixing and ball milling with MgH 2-CrOOH@CNT can effectively improve the hydrogen storage performance of magnesium-based hydrogen storage materials, achieving the effects of rapid hydrogen absorption and desorption at low temperatures and hydrogen absorption at room temperature. The high-energy ball milling method mechanically mixes powders of different materials in a certain ratio. Nanomaterials can be prepared using high-energy ball milling. High-intensity and long-time grinding can make the powders fully uniform and refined. At the same time, the forced force during the ball milling process will introduce a large amount of strain and defects. By enhancing the surface activity and shortening the diffusion distance, excellent hydrogen storage performance can be obtained. In addition, the high-energy ball milling method can use mechanical energy to induce chemical reactions to produce new active substances different from the original added substances, thereby preparing new materials with excellent hydrogen storage performance.

[0016] The CrOOH@CNT involved in the present invention is a novel carbon material-supported transition metal-based catalyst, and there is currently no relevant research report on the catalytic modification of magnesium-based hydrogen storage materials by CrOOH@CNT. Therefore, the present invention uses CrOOH@CNT to dope and catalyze the Mg / MgH 2 system, realizing that magnesium hydride can rapidly release hydrogen at 200 °C and absorb 4.8 wt% hydrogen at room temperature (pure magnesium hydride hardly absorbs hydrogen at low temperatures), greatly reducing its initial hydrogen release temperature and significantly improving the efficiency of hydrogen absorption and desorption conversion at low temperatures, and developing a high-efficiency hydrogen storage composite material with excellent low-temperature hydrogen storage performance and high hydrogen storage capacity.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] (1) A new catalyst suitable for hydrogen storage materials is proposed, and the processes for preparing hydrogen storage materials, catalysts, and corresponding composite materials are simple and convenient for synthesis;

[0019] (2) The preparation process has low requirements for equipment, is easy to implement, and can be applied to industrial large-scale production;

[0020] (3) The obtained composite material has excellent hydrogen storage performance, especially hydrogen absorption and desorption performance, has a high reversible hydrogen capacity, and can achieve the effect of hydrogen absorption at room temperature, with broad commercial application prospects. Description of the Drawings

[0021] Figure 1 XRD pattern of the prepared CrOOH@CNT catalyst;

[0022] Figure 2 SEM image of the prepared CrOOH@CNT catalyst;

[0023] Figure 3 MgH doped with different contents of CrOOH@CNT 2 Hydrogen desorption curve of the hydrogen storage material with temperature;

[0024] Figure 4 MgH of CrOOH@CNT synthesized by doping different ratios of chromium nitrate and CNT 2 Hydrogen desorption curve with temperature of the hydrogen storage material;

[0025] Figure 5 For MgH 2 Isothermal hydrogen desorption curve at 250 °C of MgH + 10% CrOOH@CNT;

[0026] Figure 6 For MgH 2 Hydrogen absorption curves of MgH + 10% CrOOH@CNT at different temperatures;

[0027] Figure 7 For MgH 2 Room temperature hydrogen absorption curve of MgH + 10% CrOOH@CNT;

[0028] Figure 8 SEM image of the magnesium-based hydrogen storage material prepared in Example 2;

[0029] Figure 9 For MgH of Test Example 5 2 Hydrogen desorption curve with temperature of the hydrogen storage material;

[0030] Figure 10 Hydrogen desorption curve with temperature of the hydrogen storage material of Test Example 7. Specific implementation mode

[0031] For ease of understanding, the technical solutions and implementation modes of the present invention will be further clearly, completely, and in detail described below through specific embodiments and in combination with the accompanying drawings. It should be noted that the embodiments described in the present invention are implemented on the premise of the technical solutions of the present invention, and detailed implementation modes and specific operation processes are given, but they are only a part of the embodiments of the present invention, rather than all embodiments. The specific implementation modes described are only for explaining and interpreting the present invention and do not limit the present invention. Based on the embodiments in the present invention, all other implementation modes obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0032] Unless otherwise specified, the experimental methods used in the following embodiments are all conventional methods or those with little impact on the results. The materials, reagents, etc. used in the embodiments can be obtained from commercial channels unless otherwise specified.

[0033] Example 1 Preparation of CrOOH@CNT materials with different ratios of chromium nitrate and CNT

[0034] 0.3, 0.5, 0.6, and 0.8 g of Cr(NO) were separately taken 3 ·9H 2O is dissolved in 20 ml of deionized water, and then 0.7, 0.5, 0.4, and 0.2 g of carbon nanotubes CNT are added to the solution. Among them, Cr(NO) 3 ·9H 2 O and the mass ratio of CNT are 3:7, 5:5, 6:4, and 8:2. The mixed solution is ultrasonically dispersed for half an hour, and then magnetically stirred for half an hour, and this is alternated 3 - 4 times. Then, the mixed solution is reacted in a high-pressure reactor at 200 °C for 24 h. After the reaction, it is filtered and dried to obtain the CrOOH@CNT nanometer powder catalyst, and the particle size of CrOOH is about 40 - 60 nm.

[0035] Figure 1 XRD pattern of the CrOOH@CNT catalyst prepared with the ratio of chromium nitrate to CNT being 5:5. Figure 2 SEM image of the prepared CrOOH@CNT catalyst. It can be seen that a small amount of dispersed CrOOH nanoparticles are loaded on the intertwined carbon nanotubes.

[0036] Example 2 MgH 2 Preparation of magnesium-based hydrogen storage materials with CrOOH@CNT materials prepared with different ratios of chromium nitrate and CNT

[0037] Using the CrOOH@CNT materials with different ratios (chromium nitrate:CNT = 3:7, 5:5, 6:4, 8:2) prepared in Example 1, 0.2 g of CrOOH@CNT and 1.8 g of MgH 2 are put into a ball-milling tank. MgH 2 is in the form of massive particles, and the size has basically no effect on the reaction. The size in this example is about 0.5 - 1 μm; then about 80 g of stainless steel balls are added for ball-milling and mixing. The ball-milling time is 24 h, the rotation speed is 500 rpm, and 40 bar of hydrogen or argon is filled into the ball-milling tank. After ball-milling, the magnesium-based hydrogen storage material is obtained. Figure 8 Scanning image of the obtained magnesium-based hydrogen storage material (with the ratio of chromium nitrate to CNT being 5:5). It can be seen that the intertwined carbon nanotubes connect the massive magnesium hydride together.

[0038] Example 3 MgH 2 Preparation of magnesium-based hydrogen storage materials with CrOOH@CNT materials with different feeding amounts

[0039] Using the CrOOH@CNT material with chromium nitrate:CNT = 5:5 prepared in Example 1, weigh CrOOH@CNT and MgH 2 and then put them into a ball-milling tank, where the CrOOH@CNT material accounts for the composite material (CrOOH@CNT and MgH 25%, 10%, and 15% of the total mass, with the total mass being 2 g; then add about 80 g of stainless steel balls for ball milling and mixing. The ball milling time is 24 h, the rotation speed is 500 rpm, and 40 bar of hydrogen is filled into the ball milling tank. After the ball milling is completed, a magnesium-based hydrogen storage material is obtained.

[0040] Example 4

[0041] Dissolve 0.5 g of Cr(NO) 3 ·9H 2 O in 20 ml of deionized water, then add 0.5 g of carbon nanotubes CNT to this solution. Ultrasonically disperse the mixture for half an hour, then magnetically stir for half an hour, and alternate like this 3 - 4 times. Then react the mixture in a high-pressure reactor at 190 °C for 28 h. After the reaction, filter and dry to obtain the CrOOH@CNT nanometer powder catalyst.

[0042] Example 5

[0043] Dissolve 0.5 g of Cr(NO) 3 ·9H 2 O in 20 ml of deionized water, then add 0.5 g of carbon nanotubes CNT to this solution. Ultrasonically disperse the mixture for half an hour, then magnetically stir for half an hour, and alternate like this 3 - 4 times. Then react the mixture in a high-pressure reactor at 210 °C for 20 h. After the reaction, filter and dry to obtain the CrOOH@CNT nanometer powder catalyst.

[0044] Example 6

[0045] Use the CrOOH@CNT material prepared in Example 4. Weigh 0.2 g of CrOOH@CNT and 1.8 g of MgH 2 and put them into the ball milling tank; then add about 150 g of stainless steel balls for ball milling and mixing. The ball milling time is 48 h, the rotation speed is 300 rpm, and 40 bar of nitrogen is filled into the ball milling tank. After the ball milling is completed, a magnesium-based hydrogen storage material is obtained, and its hydrogen storage performance is also improved. The initial hydrogen release temperature is reduced, and the efficiency of hydrogen absorption and release conversion at low temperature is greatly improved, and it can absorb hydrogen at room temperature.

[0046] Comparative Example 1 Preparation of magnesium-based hydrogen storage material using only CrOOH, CNT, and MgH 2

[0047] Dissolve 1 g of Cr(NO) 3 ·9H 2 ​O and CNT were dissolved in 20 ml of deionized water. The two mixtures were ultrasonically dispersed for half an hour and then magnetically stirred for half an hour, and this was alternated 3 - 4 times. Then the mixture was reacted in a high - pressure reactor at 200 °C for 24 h. After the reaction, it was filtered by suction and dried to obtain CrOOH and CNT catalysts. Then the two catalysts were respectively mixed with MgH 2 and put into a ball - milling tank. The mass of the catalyst was 0.2 g, and the mass of MgH 2 was 1.8 g; about 80 g of stainless - steel balls were added for ball - milling and mixing. The ball - milling time was 24 h, the rotation speed was 500 rpm, and 40 bar of hydrogen was filled into the ball - milling tank. After ball - milling, a magnesium - based hydrogen storage material was obtained.

[0048] In Comparative Example 2, other carbon materials were combined with CrOOH composite catalysts and MgH 2 to prepare magnesium - based hydrogen storage materials

[0049] 1 g of Cr(NO) 3 ·9H 2 O and AC (activated carbon) or KB (Ketjenblack) were dissolved in 20 ml of deionized water to obtain two chromium nitrate solutions with different carbon materials mixed. The two mixtures were ultrasonically dispersed for half an hour and then magnetically stirred for half an hour, and this was alternated 3 - 4 times. Then the mixture was reacted in a high - pressure reactor at 200 °C for 24 h. After the reaction, it was filtered by suction and dried to obtain CrOOH@AC or CrOOH@KB catalysts. Then the two catalysts were respectively mixed with MgH 2 and put into a ball - milling tank. The mass of the catalyst was 0.2 g, and the mass of MgH 2 was 1.8 g; about 80 g of stainless - steel balls were added for ball - milling and mixing. The ball - milling time was 24 h, the rotation speed was 500 rpm, and 40 bar of hydrogen was filled into the ball - milling tank. After ball - milling, a magnesium - based hydrogen storage material was obtained.

[0050] Test Example 1: The hydrogen - releasing test was carried out on the magnesium - based hydrogen storage material prepared in Example 3

[0051] After ball - milling, the ball - milling tank was opened in the glove box, and about 200 mg of the composite material powder was scraped and put into a self - made Sieverts - type gas - solid reaction device. After loading, vacuum treatment was carried out. After repeatedly evacuating at intervals several times, the test was started. The heating program was set to start from 20 °C and increase to 450 °C at a heating rate of 2 °C / min. Among them, the composite material included: ball - milled MgH 2 , MgH ball - milled according to the ball - milling conditions of Example 3 2 , and magnesium - based hydrogen storage materials with different doping amounts prepared in Example 3: MgH 2 +5% CrOOH@CNT, MgH 2+10% CrOOH@CNT, MgH 2 +15% CrOOH@CNT.

[0052] Figure 3 MgH doped with different contents of CrOOH@CNT 2 Hydrogen desorption curves of hydrogen storage materials with temperature. The hydrogen desorption curves are as Figure 3 shown. As the content of CrOOH@CNT increases, the hydrogen desorption temperature of the material gradually decreases, and the initial hydrogen desorption temperature decreases from 240 °C to about 200 °C. Although the hydrogen desorption capacity gradually decreases as the content of CrOOH@CNT increases, it still maintains a high capacity of about 6 wt%.

[0053] Under the same test conditions, the initial hydrogen desorption temperature of the composite material with the catalyst added decreases to about 200 °C, which is about 180 °C lower than the hydrogen desorption temperature of unball-milled MgH 2 and about 100 °C lower than the hydrogen desorption temperature of ball-milled MgH 2 , achieving a significant decrease in the hydrogen desorption temperature of MgH 2 catalyzed by CrOOH@CNT.

[0054] Test Example 2 Hydrogen desorption test was carried out on the magnesium-based hydrogen storage material prepared in Example 2

[0055] The steps of the hydrogen desorption test are the same as those in Test Example 1. Figure 4 MgH of CrOOH@CNT synthesized by doping different ratios of chromium nitrate and CNT 2 Hydrogen desorption curves of hydrogen storage materials with temperature. As the ratio of chromium nitrate and CNT increases, the hydrogen desorption temperature of the material gradually decreases. When the ratio of chromium nitrate and CNT is 5:5, further increasing the ratio will basically not cause an obvious change in the hydrogen desorption temperature of the material, but compared with the hydrogen desorption temperature of pure MgH after ball milling 2 it also decreases by about 100 °C. Therefore, in subsequent tests, the CrOOH@CNT catalyst is used in a ratio of chromium nitrate:CNT = 5:5.

[0056] Test Example 3 Room temperature hydrogenation test of MgH 2 +10% CrOOH@CNT (chromium nitrate:CNT = 5:5) magnesium-based hydrogen storage material

[0057] MgH prepared in Example 3 was used 2+10% CrOOH@CNT (chromium nitrate: CNT = 5:5) magnesium-based hydrogen storage material, and dehydrogenation has been carried out. Weigh about 200 mg of the composite material powder after dehydrogenation and put it into a self-made Sieverts-type gas-solid reaction device. After loading, vacuum treatment is carried out, and hydrogenation test starts at room temperature (preferably 20 - 30 °C). When hydrogenating, the hydrogen pressure is set to 30 bar, and the hydrogenation time is set to 24 h.

[0058] Figure 7 is MgH 2 Room temperature hydrogen absorption curve of +10% CrOOH@CNT. It can be seen that the sample after dehydrogenation can absorb 4.8 wt.% of hydrogen at room temperature, which is equivalent to 63% of the hydrogen storage system capacity.

[0059] Test Example 4 MgH 2 Isothermal dehydrogenation test of +10% CrOOH@CNT (chromium nitrate: CNT = 5:5) magnesium-based hydrogen storage material

[0060] Use the MgH prepared in Example 3 2 +10% CrOOH@CNT (chromium nitrate: CNT = 5:5) magnesium-based hydrogen storage material. After ball milling, open the ball milling tank in the glove box, scrape about 200 mg of the composite material powder and put it into a self-made Sieverts-type gas-solid reaction device. After loading, vacuum treatment is carried out. After repeatedly evacuating at intervals several times, the test starts. The heating program starts from 20 °C and is quickly heated to 250 °C at a heating rate of 20 °C / min. Set the holding time to 12 h. The test method for the pure MgH 2 sample is the same.

[0061] Such as Figure 5 is the 250 °C constant temperature dehydrogenation curve of the two. Under the same test conditions, the composite material with the catalyst can release 5.5 wt.% of hydrogen in less than one hour, while pure MgH 2 basically does not release hydrogen at 250 °C. This comparison fully shows that CrOOH@CNT catalysis realizes the rapid dehydrogenation of MgH 2 material at low temperature.

[0062] Test Example 5

[0063] Use the MgH2 + 10% CrOOH or MgH2 + 10% CNT magnesium-based hydrogen storage material prepared in Comparative Example 1. After ball milling, open the ball milling tank in the glove box, scrape about 200 mg of the composite material powder and put it into a self-made Sieverts-type gas-solid reaction device. After loading, vacuum treatment is carried out. After repeatedly evacuating at intervals several times, the test starts. The heating program is set to start from 20 °C and is raised to 450 °C at a heating rate of 2 °C / min.

[0064] As Figure 9 Figure 9 shows the hydrogen desorption curves of the two with temperature. Under the same test conditions, the initial hydrogen desorption temperature and hydrogen desorption capacity of the individual CrOOH and CNT catalysts are lower than those of the catalyst composed of both, indicating that the synergistic effect of CrOOH and CNT can best improve their hydrogen storage performance.

[0065] Test Example 6

[0066] The MgH prepared in Example 3 was used 2 +10% CrOOH@CNT magnesium-based hydrogen storage material (chromium nitrate: CNT = 5:5), and hydrogen desorption was carried out. About 200 mg of the composite material powder after hydrogen desorption was weighed and put into a self-made Sieverts-type gas-solid reaction device. After loading, vacuum treatment was carried out. The heating program was set to start at 20 °C and was heated to 40 °C, 100 °C, and 150 °C at a heating rate of 20 °C / min respectively.

[0067] As Figure 6 Figure 6 shows the isothermal hydrogen absorption curves at three different temperatures. It can be seen that at temperatures of 100 °C and 150 °C, hydrogen can be rapidly absorbed to saturation within 100 min, and the hydrogen absorption capacity reaches about 6 wt%, achieving good hydrogen absorption and desorption reversibility. Even at a relatively low temperature of 40 °C, nearly 5.1 wt% of hydrogen can be absorbed.

[0068] Test Example 7

[0069] The MgH prepared in Comparative Example 2 was used 2 +10% CrOOH@AC or

[0070] MgH 2 +10% CrOOH@KB magnesium-based hydrogen storage material. After ball milling, the ball milling tank was opened in the glove box, and about 200 mg of the composite material powder was scraped and put into a self-made Sieverts-type gas-solid reaction device. After loading, vacuum treatment was carried out. After repeated intermittent vacuum pumping several times, the test began. The heating program was set to start at 20 °C and was heated to 450 °C at a heating rate of 2 °C / min.

[0071] As Figure 10 Figure 10 shows the hydrogen desorption curves of the two with temperature. Under the same test conditions, the initial hydrogen desorption temperatures of the carbon materials AC and KB are higher than that of the catalyst containing CNT, indicating that the effect of CNT is more excellent than the other two carbon materials, and it further shows that the synergistic effect of CrOOH and CNT can best improve their hydrogen storage performance.

[0072] The above-described embodiments are only preferred solutions of the present invention and do not impose any formal limitations on the present invention. There are other variations and modifications without exceeding the technical solutions recorded in the claims.

Claims

1. A solid-state magnesium-based hydrogen storage material MgH 2 -CrOOH@CNT, It is characterized in that The hydrogen storage material described is obtained by ball-milling the CrOOH@CNT material with MgH 2 to obtain a solid-state magnesium-based hydrogen storage material MgH 2 -CrOOH@CNT. The CrOOH@CNT material is a CNT-supported CrOOH nanoparticle catalytic material, and the CrOOH@CNT material is prepared by a hydrothermal method from a chromium source and CNT.

2. The solid-state magnesium-based hydrogen storage material MgH 2 -CrOOH@CNT according to claim 1 It is characterized in that The CrOOH@CNT material accounts for 0.1%-20% of the total mass of the composite material.

3. The solid-state magnesium-based hydrogen storage material MgH 2 -CrOOH@CNT according to claim 2 It is characterized in that The CrOOH@CNT material accounts for 5%-15% of the total mass of the composite material.

4. A solid-state magnesium-based hydrogen storage material MgH 2 -CrOOH@CNT, It is characterized in that The chromium source is chromium nitrate nonahydrate.

5. A solid-state magnesium-based hydrogen storage material MgH 2 -CrOOH@CNT, It is characterized in that The chromium source accounts for 5%-90% of the total mass of the chromium source and CNT.

6. The solid-state magnesium-based hydrogen storage material MgH 2 -CrOOH@CNT according to claim 5 It is characterized in that The chromium source accounts for 30%-80% of the total mass of the chromium source and CNT.

7. The solid-state magnesium-based hydrogen storage material MgH 2 -CrOOH@CNT according to claim 1 It is characterized in that The temperature of the hydrothermal reaction is 200±10°C, and the reaction time is 24±4 h.

8. A method for preparing the solid magnesium-based hydrogen storage material MgH 2 -CrOOH@CNT according to any one of claims 1-7 It is characterized in that Mix the CrOOH@CNT material with MgH 2 by ball milling to obtain the solid-state magnesium-based hydrogen storage material MgH 2 -CrOOH@CNT.

9. A preparation method of a solid-state magnesium-based hydrogen storage material MgH 2 -CrOOH@CNT according to claim 8 It is characterized in that The ball milling includes: under a protective atmosphere, the ball-to-material ratio is 40~80:1, the ball milling time is 12~48 h, and the revolution speed of the ball mill is not less than 300 rpm.

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