Magnesium-based hydrogen storage material as well as preparation method and application thereof

Abstract

The invention relates to the field of magnesium-based hydrogen storage material preparation, and particularly provides a magnesium-based hydrogen storage material as well as a preparation method and application thereof. The high-entropy alloy contains Ti, V, Cr, Ni and Zr. The preparation method of the magnesium-based hydrogen storage material comprises the following steps that under the hydrogen pressure, MgH2 and the high-entropy alloy powder are mixed and subjected to ball milling. The invention provides application of the magnesium-based hydrogen storage material in hydrogen storage. By adding the high-entropy alloy, the hydrogen desorption temperature of MgH2 can be remarkably reduced, and the hydrogen desorption temperature of MgH2 can be reduced to 300 DEG C or below from 350-400 DEG C through doping modification of the high-entropy alloy.

Description

Technical Field

[0001] The present invention relates to the field of preparation of magnesium-based hydrogen storage materials, and particularly to a magnesium-based hydrogen storage material, a preparation method thereof and an application thereof. Background Art

[0002] Hydrogen energy is a secondary energy source with zero carbon emissions, no pollution, high energy density and rich sources, and its applications are very extensive. The development of hydrogen energy is an important strategic path to promote China's economic and social development and achieve a low-carbon and green transformation of energy. Hydrogen energy has received great attention from major economies in the world such as the United States, the European Union and Japan, and is also an important part of China's energy strategic system. China is accelerating the industrial layout of hydrogen energy. In the entire hydrogen energy industrial chain, safe, economic and efficient hydrogen storage technology is one of the key factors restricting the development and application of hydrogen energy. Among the three hydrogen storage methods of gaseous, liquid and solid states, the solid-state hydrogen storage method based on metal or alloy hydrides has received extensive attention from researchers. In hydrogen storage alloys, hydrogen reacts with the alloy in the form of chemical adsorption to form hydrides, thereby storing hydrogen reversibly in solid form, with advantages such as low cost, high hydrogen storage density and good safety.

[0003] Compared with other hydrogen storage alloy systems, magnesium-based hydrogen storage materials have advantages such as rich resources, non-toxicity and high weight hydrogen storage density, and are one of the important branches of solid-state hydrogen storage materials. The theoretical hydrogen storage capacity of MgH2 can reach 7.6 wt%, but its hydrogen desorption reaction enthalpy is relatively high (~76 kJ / mol·H2 -1 ), and the reaction activation energy is also relatively high (160 kJ / mol). The above characteristics make the hydrogen desorption temperature of MgH2 too high (>300 °C), and the hydrogen absorption and desorption kinetics are slow, seriously hindering the practical application of MgH2. Therefore, researchers usually adopt methods of nanosizing the material and doping and modifying with catalysts to improve the hydrogen storage performance of MgH2. When the size of the MgH2 material is reduced to the nanoscale, its hydrogen absorption and desorption kinetic performance will be significantly improved. At the same time, researchers have found that when catalysts such as metals, intermetallic compounds, oxides, halides and carbides are doped into MgH2, the hydrogen absorption and desorption kinetic performance of MgH2 can be further improved, and the hydrogen desorption temperature of the material can be reduced. Among many magnesium-based hydrogen storage material catalysts, transition metals and their compounds have the best catalytic effect, which can significantly reduce the hydrogen absorption and desorption rate of the alloy and significantly reduce its hydrogen desorption temperature. Nevertheless, the hydrogen desorption temperature of magnesium-based hydrogen storage materials is still too high, and there is an urgent need to develop new catalysts with better catalytic performance. Summary of the Invention

[0004] The object of the present invention is to overcome the problems that the dehydrogenation temperature of MgH2 is too high, the hydrogen absorption and desorption kinetic performance is poor, and the existing catalyst systems have limited improvement effect on the hydrogen storage performance of MgH2. A high-entropy alloy containing Ti, V, Cr, Ni, and Zr is added to the MgH2 material to prepare a magnesium-based hydrogen storage material with good hydrogen storage performance.

[0005] To achieve the above object, on the one hand, the present invention provides a magnesium-based hydrogen storage material, which contains MgH2 and a high-entropy alloy; the high-entropy alloy contains Ti, V, Cr, Ni, and Zr.

[0006] On the second hand, the present invention provides a preparation method of the magnesium-based hydrogen storage material, including the following steps: under hydrogen pressure, mixing and ball-milling MgH2 with the high-entropy alloy powder.

[0007] On the third hand, the present invention provides an application of the magnesium-based hydrogen storage material in hydrogen storage.

[0008] The high-entropy alloy composed of the present invention can significantly reduce the dehydrogenation temperature of MgH2. After being doped and modified with the high-entropy alloy, the dehydrogenation temperature of MgH2 can be reduced from 350-400 °C to below 300 °C. Description of the Drawings

[0009] Figure 1 is Ti 20 V 20 Cr 20 Ni 20 Zr 20 Backscattered electron image and element surface distribution map (EDS mapping) of the high-entropy alloy; Figure 2 is Ti 20 V 20 Cr 20 Ni 20 Zr 20 First hydrogen absorption curve of the high-entropy alloy powder under the conditions of 23.5 °C and 0.5 Mpa hydrogen pressure; Figure 3 is Ti after the first hydrogenation 20 V 20 Cr 20 Ni 20 Zr 20 TG and DSC curves of the high-entropy alloy; Figure 4 is Ti in the as-cast state (As-melted), after hydrogenation (Hydrogenated) and after dehydrogenation (Desorbed) 20 V 20 Cr 20 Ni 20 Zr 20XRD pattern of high-entropy alloy; Figure 5 are the TG and DSC curves of the magnesium-based hydrogen storage material prepared by high-energy ball milling under a hydrogen atmosphere in Example 1; Figure 6 is the first hydrogen absorption curve of the magnesium-based hydrogen storage material prepared by high-energy ball milling under a hydrogen atmosphere in Example 1 after the first hydrogen release under the conditions of 23.5 °C and 0.5 Mpa hydrogen pressure. Detailed implementation manners

[0010] The following will detail the specific implementation manners of the present invention. It should be understood that the specific implementation manners described herein are only for explaining and illustrating the present invention, and are not used to limit the present invention.

[0011] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0012] The present invention provides a magnesium-based hydrogen storage material, which contains MgH2 and a high-entropy alloy; the high-entropy alloy contains Ti, V, Cr, Ni, and Zr. The addition of the high-entropy alloy composed of the present invention can significantly reduce the hydrogen release temperature of MgH2. After being doped and modified by the high-entropy alloy, the hydrogen release temperature of MgH2 can be reduced from 350 - 400 °C to below 300 °C.

[0013] According to the present invention, the weight ratio of MgH2 and the high-entropy alloy in the magnesium-based hydrogen storage material can be selected as needed. An exemplary embodiment is described, but it does not limit the scope of the present invention. For example, based on the total weight of the material, the content of MgH2 is 93 - 97 wt%, and the content of the high-entropy alloy is 3 - 7 wt%. Adopting the foregoing preferred technical solution helps to ensure good hydrogen storage capacity of the material while improving the hydrogen absorption and desorption kinetic performance of the material.

[0014] According to a preferred embodiment of the present invention, in the magnesium-based hydrogen storage material, the high-entropy alloy has a single-phase structure, preferably a C14 Laves single-phase structure; Ti and Ni elements are mainly distributed at the grain boundaries, Cr element is mainly distributed in the grains, and V and Zr elements are relatively uniformly distributed in the microstructure of the alloy.

[0015] In the present invention, the foregoing material compositions can all achieve the purpose of the present invention, and there are no special requirements for the specific composition of the elements of the high-entropy alloy in the magnesium-based hydrogen storage material. For example, the chemical formula of the high-entropy alloy is denoted as Ti a V b Cr cNi d Zr e , where 5 at% ≤ a ≤ 35 at%, 5 at% ≤ b ≤ 35 at%, 5 at% ≤ c ≤ 35 at%, 5 at% ≤ d ≤ 35 at%, 5 at% ≤ e ≤ 35 at%, and a + b + c + d + e = 100. According to a preferred embodiment of the present invention, a = b = c = d = e. By adopting the aforementioned preferred technical solution, a high-entropy alloy catalyst with good room-temperature hydrogen storage performance can be obtained. a, b, c, d, and e are the atomic ratios of each metal, and at% is a well-known technical term in the art, referring to the atomic mass percentage %.

[0016] For the magnesium-based hydrogen storage material according to a preferred embodiment of the present invention, the first hydrogen desorption endothermic peak of the magnesium-based hydrogen storage material is 256.88 °C, and the total hydrogen desorption amount is 5.74 wt%.

[0017] For the magnesium-based hydrogen storage material according to a preferred embodiment of the present invention, under the conditions of 23.5 °C and 0.5 Mpa hydrogen pressure, the magnesium-based hydrogen storage material absorbs hydrogen for the first time and reaches saturated hydrogen absorption in 5 h, and the maximum hydrogen absorption amount is 3.08 wt%.

[0018] For the magnesium-based hydrogen storage material according to a preferred embodiment of the present invention, the high-entropy alloy reaches saturated hydrogen absorption within 4 minutes under the conditions of 23.5 °C and 0.5 Mpa hydrogen pressure, and the maximum hydrogen absorption amount is 1.6 wt%; The hydrogen desorption endothermic peak is 311.35 °C, and the maximum hydrogen desorption amount is 1.52 wt%.

[0019] In the present invention, the foregoing material compositions can all achieve the purpose of the present invention. There are no special requirements for the preparation method of the magnesium-based hydrogen storage material. A preferred embodiment is demonstrated as follows, but the scope of the present invention is not limited thereby, including the following steps: Under hydrogen pressure, MgH2 and high-entropy alloy powder are mixed and ball-milled. By adopting the aforementioned preferred technical solution, it is helpful to avoid hydrogen desorption during the ball-milling process of the composite material, prevent material oxidation, and has the advantage of hydrogen storage performance.

[0020] According to the method of the present invention, as long as the purpose of the present invention can be achieved, there are no special requirements for the steps and conditions of ball-milling. The following is a demonstration, but the scope of the present invention is not limited thereby.

[0021] According to an embodiment of the present invention, ball-milling is carried out under the conditions of 15 - 20 Mpa hydrogen pressure for 4 - 6 h.

[0022] According to an embodiment of the present invention, the steps of ball-milling include: performing multiple ball-millings, each ball-milling time is 0.1 - 1 h, the intermittent time between two adjacent ball-millings is 0.1 - 1 h, and the total ball-milling time is 4 - 6 h.

[0023] According to a specific embodiment of the present invention, the ball milling steps include: performing multiple ball milling operations, with each ball milling time being 0.5 h, the intermittent time between two adjacent ball milling operations being 0.5 h, and the total ball milling time being 4 - 6 h. A specific embodiment is demonstrated by way of example, but the scope of the present invention is not limited thereby, and it includes the following steps: outside the glove box, after repeatedly purging the ball milling tank with argon and vacuuming, hydrogen is filled. After closing the gas filling valve of the ball milling tank, the ball milling tank is loaded into a planetary high-energy ball mill for ball milling. After the ball milling is completed, the hydrogen in the ball milling tank is depressurized, and after repeatedly purging with argon and vacuuming, the gas valve is closed and sealed. Inside the glove box, the sealed ball milling tank is opened, and the ball milled product is taken out. By adopting the aforementioned preferred technical solution, powder caking and wall sticking can be effectively avoided, and the ball milling yield can be improved. The above is an illustrative example, but the scope of the present invention is not limited thereby.

[0024] According to an embodiment of the present invention, the mass ratio of balls to materials during the ball milling process is 10 - 40:1, preferably 20 - 30:1. By adopting the aforementioned preferred technical solution, it has the advantages of ensuring the ball milling effect, reducing energy consumption, and reducing the wear of the ball mill.

[0025] According to an embodiment of the present invention, the diameter of the grinding balls is 2 - 10 mm.

[0026] According to a preferred embodiment of the present invention, in the magnesium-based hydrogen storage material, the high-entropy alloy has a single-phase structure, preferably a C14 Laves single-phase structure; Ti and Ni elements are mainly distributed at the grain boundaries, Cr element is mainly distributed in the grains, and V and Zr elements are relatively evenly distributed in the microstructure of the alloy.

[0027] According to an embodiment of the present invention, the high-entropy alloy powder has a particle size of less than 200 mesh. Generally, the massive as-cast high-entropy alloy is crushed and ground, and then sieved with a sieve mesh to obtain the high-entropy alloy powder. A specific embodiment is demonstrated by way of example, but the scope of the present invention is not limited thereby, and it includes the following steps: placing the melted high-entropy alloy ingot into a glove box with an argon atmosphere, using a titanium alloy mortar and pestle to break and grind the ingot, and sieving the ground powder with a 200-mesh sieve to obtain the high-entropy alloy powder.

[0028] In the present invention, there is no special requirement for the purity of MgH2. According to a preferred embodiment of the present invention, the purity of MgH2 is above 99%.

[0029] In the present invention, there is no special requirement for the equipment for preparing the magnesium-based hydrogen storage material by ball milling and doping modification of MgH2, and common equipment can be used for the present invention, such as a planetary high-energy ball mill.

[0030] In the present invention, there are no special requirements for preparing the high-entropy alloy, and any method commonly used in the art for preparing high-entropy alloys can be used in the present invention, such as a high-vacuum arc melting furnace. Specifically, for example, in an argon atmosphere, the weighed Ti, V, Cr, Ni, and Zr are flipped and melted to obtain a bulk as-cast high-entropy alloy. A demonstration of one embodiment is given below, but the scope of the present invention is not limited thereby, and it includes the following steps: placing the taken Ti, V, Cr, Ni, and Zr into a clean high-vacuum arc melting furnace, sealing the melting furnace, evacuating to the required vacuum degree for melting, introducing a small amount of argon, and then repeatedly flipping and melting the above particles 4 times to ensure uniform melting, thereby obtaining the high-entropy alloy.

[0031] The present invention provides the application of the magnesium-based hydrogen storage material in hydrogen storage.

[0032] In the present invention, the hydrogen release temperature of the magnesium-based hydrogen storage material is lower than 300 °C.

[0033] The present invention will be further described below by way of examples, but the application of the present invention is not limited by these examples.

[0034] The high-entropy alloy in the following examples was prepared by the following steps: Prepare Ti by high-vacuum arc melting method 20 V 20 Cr 20 Ni 20 Zr 20 The high-entropy alloy, the specific experimental process is as follows: (1) Weigh out high-purity Ti particles (99.9%, 3*3 mm), V particles (99.95%, 3*3 mm), Cr particles (99.95%, 1-3 mm), Ni particles (99.9%, 3*3 mm)), and Zr particles (99.9%, 2.4*5 mm) according to the corresponding atomic ratios using an analytical balance, that is, 7.960 g of Ti particles, 8.469 g of V particles, 8.645 g of Cr particles, 9.758 g of Ni particles, and 15.167 g of Zr particles, with a total weight of 50 g; (2) Place the taken Ti, V, Cr, Ni, and Zr particles into a clean high-vacuum arc melting furnace, seal the melting furnace, evacuate to the required vacuum degree for melting, introduce a small amount of argon, and then repeatedly flip and melt the above particles 4 times to ensure uniform melting, thereby obtaining the high-entropy alloy; (3) Ti 20 V 20 Cr 20 Ni 20 Zr 20The high-entropy alloy ingot is placed in a glove box with an argon atmosphere (H2O < 1 ppm, O2 < 1 ppm). Using a titanium alloy mortar and pestle, the ingot is crushed and ground. The ground powder is screened through a 200-mesh sieve to obtain the alloy powder.

[0035] Figure 1 is Ti 20 V 20 Cr 20 Ni 20 Zr 20 Backscattered electron image and elemental surface distribution map (EDS mapping) of the high-entropy alloy.

[0036] It can be seen that Ti 20 V 20 Cr 20 Ni 20 Zr 20 The high-entropy alloy shows a single-phase structure, and no other second phases are found in the alloy. In addition, it can be seen that Ti and Ni elements are mainly distributed at the grain boundaries, Cr element is mainly distributed in the grains, and V and Zr elements are relatively evenly distributed in the microstructure of the alloy.

[0037] Figure 2 is Ti 20 V 20 Cr 20 Ni 20 Zr 20 The first hydrogen absorption curve of the high-entropy alloy powder under the conditions of 23.5 °C and 0.5 MPa hydrogen pressure, as Figure 2 shown.

[0038] It can be seen that Ti 20 V 20 Cr 20 Ni 20 Zr 20 The high-entropy alloy has good hydrogen absorption kinetic performance at room temperature. Under the condition of 0.5 MPa hydrogen pressure, the alloy reaches saturated hydrogen absorption in 4 minutes, and the maximum hydrogen absorption amount is 1.60 wt%.

[0039] Figure 3 is Ti after the first hydrogenation 20 V 20 Cr 20 Ni 20 Zr 20 TG and DSC curves of the high-entropy alloy, as Figure 3 shown.

[0040] It can be seen that after complete hydrogenation, Ti 20 V 20 Cr 20 Ni 20 Zr 20High-entropy alloys cannot release hydrogen at room temperature. The endothermic peak for hydrogen release from the alloy is approximately at 311.35 °C, and the maximum hydrogen release capacity is 1.52 wt%, which is equivalent to the maximum hydrogen absorption capacity in the first cycle.

[0041] Figure 4 Ti in the as-melted, hydrogenated, and desorbed states 20 V 20 Cr 20 Ni 20 Zr 20 XRD patterns of the high-entropy alloy are shown as Figure 4 follows.

[0042] It can be seen that Ti 20 V 20 Cr 20 Ni 20 Zr 20 The high-entropy alloy consists of a single-phase C14 Laves structure; after hydrogenation, the crystal structure of the alloy remains unchanged and is still a single-phase C14 Laves structure. However, the XRD diffraction peaks of the alloy shift to the left, indicating that the alloy lattice expands due to hydrogen absorption and the lattice parameter increases. At this time, the alloy forms a typical interstitial hydride; after dehydrogenation, the XRD diffraction peaks of the alloy shift to the right compared to the hydrogenated Ti 20 V 20 Cr 20 Ni 20 Zr 20 high-entropy alloy and return to the corresponding positions of the as-cast alloy.

[0043] The test process of the hydrogen absorption and desorption kinetic curves in the present invention is as follows: In the glove box, approximately 0.3 g of the sample is placed into the hydrogen storage test sample rod. The temperature of the sample is kept constant using a heating jacket. After purging with argon, the test is carried out under a given hydrogen pressure.

[0044] The test processes of thermogravimetry (TG) and differential scanning calorimetry (DSC) are as follows: Approximately 20 mg of the alloy powder sample is placed into an alumina crucible. After purging with argon, the sample is heated from room temperature to 400 - 500 °C at a heating rate of 20 °C / min under a flowing argon atmosphere of 200 ml / min to complete the test.

[0045] Example 1 Ti 20 V 20 Cr 20 Ni 20 Zr 20 The high-entropy alloy is doped and modified with MgH2 by planetary high-energy ball milling in a high-pressure hydrogen atmosphere to prepare a high-entropy alloy containing 5 wt% Ti 20 V 20 Cr20 Ni 20 Zr 20 Magnesium-based hydrogen storage material of high-entropy alloy, and the specific experimental preparation process is as follows: (1) Place the high-entropy alloy ingot into a glove box with an argon atmosphere (H2O < 1 ppm, O2 < 1 ppm). Use a titanium alloy mortar and pestle to crush and grind the ingot. For the ground powder, sieve it through a 200-mesh sieve to obtain alloy powder, and take out 0.132 g of Ti 20 V 20 Cr 20 Ni 20 Zr 20 high-entropy alloy powder; 20 V 20 Cr 20 Ni 20 Zr 20 high-entropy alloy powder; (2) Inside the above glove box, use an analytical balance to weigh 52.64 g of clean stainless steel grinding balls with a diameter of 5 mm and 2.5 g of MgH2 (99%) powder. Put the above two kinds of powder and 0.132 g of Ti 20 V 20 Cr 20 Ni 20 Zr 20 high-entropy alloy powder into a ball milling jar with an inflation valve at the same time. At this time, the mass ratio of balls to materials for ball milling is 20:1, and the mass of high-entropy alloy powder accounts for 5% of the total powder mass. After loading the powder, seal the ball milling jar and take it out of the glove box; (3) Outside the glove box, after repeatedly purging the ball milling jar with argon-vacuum, fill it with hydrogen at 15 MPa. After closing the inflation valve of the ball milling jar, put the ball milling jar into a planetary high-energy ball mill. To reduce cold welding and caking of the powder during ball milling, set the ball milling parameters as follows: plasma ball milling runs for 30 min, the machine stops running for 30 min, and so on. Set the total running time of plasma ball milling to 4 h.

[0046] (4) After ball milling, release the pressure of hydrogen in the ball milling jar. After repeatedly purging with argon-vacuum, close the gas valve and seal it. Inside the glove box, open the sealed ball milling jar and take out the magnesium-based hydrogen storage material doped and modified with 5 wt% Ti 20 V 20 Cr 20 Ni 20 Zr 20 high-entropy alloy.

[0047] Performance evaluation: Figure 5 TG and DSC curves of the magnesium-based hydrogen storage material prepared by high-energy ball milling under a hydrogen atmosphere in Example 1 are asFigure 5 as shown

[0048] It can be seen that the dehydrogenation endothermic peak position of the modified MgH2 is 256.88 °C, while for Ti 20 V 20 Cr 20 Ni 20 Zr 20 the dehydrogenation endothermic peak position of the high-entropy alloy is 316.90 °C, and the total dehydrogenation capacity of the material is 5.74 wt%.

[0049] The above results show that Ti 20 V 20 Cr 20 Ni 20 Zr 20 the addition of high-entropy alloy powder can significantly reduce the dehydrogenation temperature of MgH2. After doping with Ti 20 V 20 Cr 20 Ni 20 Zr 20 high-entropy alloy and high-energy ball milling in a hydrogen atmosphere, the dehydrogenation temperature of MgH2 can be reduced from 350 - 400 °C to below 300 °C.

[0050] Figure 6 Fig. shows the first hydrogen absorption curve of the magnesium-based hydrogen storage material prepared by high-energy ball milling in a hydrogen atmosphere in Example 1 after the first dehydrogenation at 23.5 °C and 0.5 Mpa hydrogen pressure.

[0051] It can be seen that Ti 20 V 20 Cr 20 Ni 20 Zr 20 the doping modification of the high-entropy alloy significantly improves the room-temperature hydrogen storage performance of the material. MgH2 forms Mg at a relatively high temperature, while pure Mg is difficult to react with hydrogen at room temperature. However, for Ti 20 V 20 Cr 20 Ni 20 Zr 20 the magnesium-based hydrogen storage material modified by high-entropy alloy can complete the first hydrogenation at 23.5 °C and 0.5 Mpa hydrogen pressure, and the maximum hydrogen absorption capacity after 5 h is 3.08 wt%.

[0052] Example 2: Mix Ti 20 V 20 Cr 20 Ni 20 Zr 20The high-entropy alloy doped and modified MgH2 by planetary high-energy ball milling in a high-pressure hydrogen atmosphere to prepare a magnesium-based hydrogen storage material containing 3 wt.% Ti 20 V 20 Cr 20 Ni 20 Zr 20 The specific experimental preparation process of the magnesium-based hydrogen storage material of the high-entropy alloy is as follows: (1) Place the melted ingot of the high-entropy alloy containing Ti 20 V 20 Cr 20 Ni 20 Zr 20 in a glove box with an argon atmosphere (H2O < 1 ppm, O2 < 1 ppm). Use a titanium alloy mortar and pestle to crush and grind the ingot. Screen the ground powder through a 200-mesh sieve to obtain alloy powder, and take out 0.077 g of Ti 20 V 20 Cr 20 Ni 20 Zr 20 high-entropy alloy powder; (2) In the above glove box, use an analytical balance to weigh 51.54 g of clean stainless steel grinding balls with a diameter of 5 mm and 2.5 g of MgH2 (99%) powder. Put the above two powders and 0.077 g of Ti 20 V 20 Cr 20 Ni 20 Zr 20 high-entropy alloy powder into a ball mill tank with an inflation valve at the same time. At this time, the mass ratio of balls to materials for ball milling is 20:1, and the mass of the high-entropy alloy powder accounts for 3% of the total powder mass. After loading the powder, seal the ball mill tank and take it out of the glove box; (3) Outside the glove box, after repeatedly purging the ball mill tank with argon-vacuum, fill it with 15 MPa of hydrogen. After closing the inflation valve of the ball mill tank, put the ball mill tank into a planetary high-energy ball mill. To reduce cold welding and caking of the powder during ball milling, set the ball milling parameters as plasma ball milling for 30 min and the machine stops running for 30 min, and so on. Set the total running time of plasma ball milling to 4 h.

[0053] (4) After ball milling, release the pressure of the hydrogen in the ball mill tank. After repeatedly purging with argon-vacuum, close the gas valve and seal it. In the glove box, open the sealed ball mill tank and take out the magnesium-based hydrogen storage material doped and modified with 3 wt% Ti 20 V 20 Cr 20 Ni 20 Zr 20 high-entropy alloy.

[0054] Performance evaluation: For the modified MgH2, the position of the hydrogen desorption endothermic peak is 261.43 °C, and the total hydrogen desorption amount of the material is 5.78 wt%, as shown in Table 1.

[0055] Example 3: Put Ti 20 V 20 Cr 20 Ni 20 Zr 20 The high-entropy alloy doped and modified MgH2 by planetary high-energy ball milling under a high-pressure hydrogen atmosphere to prepare a magnesium-based hydrogen storage material containing 7 wt.% Ti 20 V 20 Cr 20 Ni 20 Zr 20 The specific experimental preparation process is as follows: (1) Put the melted ingot of Ti 20 V 20 Cr 20 Ni 20 Zr 20 The high-entropy alloy ingot into a glove box with an argon atmosphere (H2O less than 1 ppm, O2 less than 1 ppm). Use a titanium alloy mortar and pestle to crush and grind the ingot. For the ground powder, sieve the alloy powder with a 200-mesh sieve, and take out 0.188 g of Ti 20 V 20 Cr 20 Ni 20 Zr 20 High-entropy alloy powder; (2) In the above glove box, use an analytical balance to weigh 53.76 g of clean stainless steel grinding balls with a diameter of 5 mm and 2.5 g of MgH2 (99%) powder. Put the above two powders and 0.188 g of Ti 20 V 20 Cr 20 Ni 20 Zr 20 High-entropy alloy powder into the ball milling tank with an inflation valve at the same time. At this time, the mass ratio of balls to materials for ball milling is 20:1, and the mass of the high-entropy alloy powder accounts for 7% of the total powder mass. After filling the powder, seal the ball milling tank and take it out of the glove box; (3) Outside the glove box, after repeatedly purging the ball milling tank with argon-vacuum, fill it with 15 MPa of hydrogen. After closing the inflation valve of the ball milling tank, put the ball milling tank into a planetary high-energy ball mill. To reduce cold welding and caking of the powder during ball milling, set the ball milling parameters as plasma ball milling for 30 min and the machine stops running for 30 min, and so on. Set the total running time of plasma ball milling to 4 h.

[0056] (4) After the ball milling is completed, the hydrogen in the ball milling tank is depressurized. After repeated washing with argon-vacuum pumping, the gas valve is closed and sealed. Inside the glove box, the sealed ball milling tank is opened, and the magnesium-based hydrogen storage material containing 7 wt% Ti 20 V 20 Cr 20 Ni 20 Zr 20 magnesium-based hydrogen storage material doped and modified with high-entropy alloy.

[0057] Performance evaluation: In Example 3, the position of the hydrogen desorption endothermic peak corresponding to the catalytically modified MgH2 is 257.62 °C, and the total hydrogen desorption amount of the material is 5.29 wt%, as shown in Table 1.

[0058] Table 1 shows the comparison of the hydrogen storage performance of Examples 1, 2, and 3.

[0059] Table 1

[0060] Comparative Example 1: Prepare a magnesium-based hydrogen storage material without Ti 20 V 20 Cr 20 Ni 20 Zr 20 high-entropy alloy, and the specific experimental preparation process is as follows: (1) Inside the glove box, use an analytical balance to weigh 50 g of clean stainless steel grinding balls with a diameter of 5 mm and 2.5 g of MgH2 (99%) powder. At this time, the ball-to-powder mass ratio of the ball milling is 20:1. After loading the powder, seal the ball milling tank and take it out of the glove box; (2) Outside the glove box, after repeatedly washing the ball milling tank with argon-vacuum pumping, fill it with 15 MPa of hydrogen. After closing the gas filling valve of the ball milling tank, install the ball milling tank into a planetary high-energy ball mill. To reduce cold welding and caking of the powder during ball milling, set the ball milling parameters as plasma ball milling for 30 min and the machine stops running for 30 min, and so on. Set the total running time of the plasma ball milling to 4 h.

[0061] (3) After the ball milling is completed, the hydrogen in the ball milling tank is depressurized. After repeated washing with argon-vacuum pumping, the gas valve is closed and sealed. Inside the glove box, open the sealed ball milling tank and take out the magnesium-based hydrogen storage material without high-entropy alloy doping and modification.

[0062] Performance evaluation: In Comparative Example 1, the position of the hydrogen desorption endothermic peak corresponding to MgH2 is 387.61 °C, and the total hydrogen desorption amount of the material is 6.89 wt%, as shown in Table 2.

[0063] Table 2 shows the comparison of hydrogen storage performance between Example 1 and Comparative Example 1.

[0064] Table 2

[0065] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the technical concept scope of the present invention, various simple modifications can be made to the technical solutions of the present invention, including the combination of each technical feature in any other suitable manner. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A magnesium-based hydrogen storage material, characterized in that, This material contains MgH2 and a high-entropy alloy; the high-entropy alloy contains Ti, V, Cr, Ni, and Zr.

2. The magnesium-based hydrogen storage material according to claim 1, wherein, Based on the total weight of the material, the content of MgH2 is 93-97 wt%, and the content of the high-entropy alloy is 3-7 wt%; and / or The high-entropy alloy has a single-phase structure, preferably a C14 Laves single-phase structure; Ti and Ni elements are mainly distributed at grain boundaries, Cr elements are mainly distributed within grains, and V and Zr elements are relatively evenly distributed within the microstructure of the alloy.

3. The magnesium-based hydrogen storage material according to claim 1 or 2, wherein, The chemical formula of the high-entropy alloy is denoted as Ti a V b Cr c Ni d Zr e , where a, b, c, d, and e are the atomic percentages of each metal. Among them, 5 at% ≤ a ≤ 35 at%, 5 at% ≤ b ≤ 35 at%, 5 at% ≤ c ≤ 35 at%, 5 at% ≤ d ≤ 35 at%, 5 at% ≤ e ≤ 35 at%, and a + b + c + d + e = 100.

4. The magnesium-based hydrogen storage material according to claim 3, wherein, Values of a, b, c, d, e, etc.

5. A method for preparing the magnesium-based hydrogen storage material according to any one of claims 1-4, comprising the following steps: mixing and ball-milling MgH2 with a high-entropy alloy powder under hydrogen pressure.

6. The preparation method according to claim 5, wherein, The conditions for ball milling include: Ball milling for 4-6 h under a hydrogen pressure of 15-20 Mpa.

7. The preparation method according to claim 5 or 6, wherein, The steps of ball milling include: performing multiple ball milling operations, with each ball milling time being 0.1-1 h, the intermittent time between adjacent ball milling operations being 0.1-1 h, and the total ball milling time being 4-6 h.

8. The preparation method according to any one of claims 5-7, wherein, The mass ratio of balls to material during the ball milling process is 10-40:1, preferably 20-30:1; and / or The diameter of the grinding balls is 2-10 mm.

9. The preparation method according to any one of claims 5-8, wherein, The high-entropy alloy has a single-phase structure, preferably a C14 Laves single-phase structure; Ti and Ni elements are mainly distributed at grain boundaries, Cr elements are mainly distributed within grains, and V and Zr elements are relatively evenly distributed within the microstructure of the alloy; and / or The particle size of the high-entropy alloy powder is below 200 mesh; and / or The purity of MgH2 is above 99%.

10. The preparation method according to any one of claims 5-9, wherein, Use a planetary high-energy ball mill for ball milling.

11. The preparation method according to any one of claims 5-10, wherein, The high-entropy alloy is prepared by a melting method.

12. Application of the magnesium-based hydrogen storage material according to any one of claims 1-4 in hydrogen storage.

13. The application according to claim 12, wherein, The hydrogen desorption temperature of the magnesium-based hydrogen storage material is below 300 °C.

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