In-situ synthesis catalytic phase reinforced magnesium-based hydrogen storage composite material and preparation method thereof

Abstract

The invention discloses an in-situ synthesis catalytic phase reinforced magnesium-based hydrogen storage composite material and a preparation method thereof.The preparation method comprises the steps that firstly, magnesium, magnesium-nickel intermediate alloy and magnesium-gadolinium intermediate alloy raw materials are weighed according to the chemical composition of Mg < 96.5-x > Ni < 3.5 > Gdx, wherein x is larger than or equal to 1 and smaller than or equal to 3, drying and smelting are conducted, and a magnesium-based alloy ingot is obtained; 2, mechanically crushing into alloy powder; 3, carrying out hydrogenation reaction to obtain hydrogenated alloy powder; and 4, carrying out dehydrogenation reaction to obtain the in-situ synthesis catalytic phase reinforced magnesium-based hydrogen storage composite material. The in-situ synthesized catalytic phase reinforced magnesium-based hydrogen storage composite material is obtained by carrying out primary hydrogen absorption and hydrogen desorption on Mg96.5-xNi3.5 Gd, the in-situ synthesized catalytic phases Mg2Ni and GdH2 are utilized to improve the hydrogen absorption and desorption speed, so that the initial hydrogen desorption temperature is greatly reduced, meanwhile, excellent cycle stability is shown, the preparation process is simple and controllable, the preparation cost is low, and the preparation method is suitable for industrial production. The method is suitable for large-scale production.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen storage materials technology, specifically relating to an in-situ self-generated catalytic phase reinforced magnesium-based hydrogen storage composite material and its preparation method. Background Technology

[0002] Driven by the goal of carbon emission reduction, hydrogen energy-related technologies and the entire hydrogen energy industry chain are developing rapidly. The hydrogen energy industry chain includes hydrogen production, storage, and utilization, with hydrogen storage, as a crucial link connecting the upstream and downstream components, receiving widespread attention. As a strategic solution to overcome the core bottlenecks of insufficient density (<5wt%) in high-pressure gaseous hydrogen storage and excessive energy consumption (-253℃) in liquid cryogenic storage, solid-state hydrogen storage materials demonstrate broad application prospects due to their advantages such as high hydrogen storage density, good safety, economic efficiency, and strong environmental adaptability.

[0003] Among various solid-state hydrogen storage materials, magnesium-based solid-state hydrogen storage materials have become a research hotspot due to their high hydrogen storage density (up to 7.6 wt%), abundant natural reserves, and good reversibility. However, their practical application is limited by problems such as excessively high thermodynamic stability of hydrides leading to high operating temperatures and slow hydrogen absorption / desorption rates caused by sluggish kinetics. Currently, researchers mainly modify magnesium-based hydrogen storage materials through particle or crystal nanosizing, external catalyst doping, and alloying. Although significant optimization effects have been achieved, performance still needs further improvement.

[0004] Nanoscale formation of grains or particles can significantly improve the kinetic performance of magnesium-based hydrogen storage materials, and even when the grain size is less than 20 nm, the thermodynamic performance can be improved. However, this method is relatively cumbersome and not suitable for large-scale applications. Furthermore, the resulting particles are highly active and prone to oxidation, and easily agglomerate during the reaction. External doping of catalysts can also improve the performance of magnesium-based hydrogen storage materials both thermodynamically and kinetically. However, the catalyst is only attached to the particle surface, making it easy to detach and difficult to optimize the internal performance of the particles. Alloying is simple and easy to operate, suitable for large-scale applications, but it also has certain drawbacks. Low alloying levels result in coarse grains, which is detrimental to performance, while high alloying levels lead to a decrease in the hydrogen storage density of the material.

[0005] Therefore, designing and developing magnesium-based hydrogen storage materials with stable microstructures and using simple and easy-to-operate preparation methods are key to the development of magnesium-based hydrogen storage materials. Summary of the Invention

[0006] The technical problem to be solved by this invention is to address the shortcomings of the prior art by providing a method for preparing an in-situ self-generated catalytic phase-reinforced magnesium-based hydrogen storage composite material. This method involves... 96.5-x Ni 3.5Gd undergoes a single hydrogen absorption and desorption process to obtain an in-situ self-generated catalytic phase-enhanced magnesium-based hydrogen storage composite material. The in-situ self-generated catalytic phases Mg2Ni and GdH2 are used to increase the hydrogen absorption and desorption rates, resulting in a significant decrease in the initial hydrogen desorption temperature. At the same time, it exhibits excellent cycle stability, solving the problems of slow reaction and difficult hydrogen desorption in existing magnesium-based hydrogen storage materials.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for preparing an in-situ self-generated catalytic phase-reinforced magnesium-based hydrogen storage composite material, characterized in that the method includes the following steps: Step 1: According to the chemical composition Mg 96.5-x Ni 3.5 Gd x , where 1≤ x ≤3, weigh out magnesium, magnesium-nickel master alloy and magnesium-gadolinium master alloy raw materials and dry them, then smelt them to obtain magnesium-based alloy ingots; Step 2: Mechanically crush the magnesium-based alloy ingot obtained in Step 1 into alloy powder of 100-200 mesh; Step 3: Place the alloy powder from Step 2 in a hydrogen atmosphere and heat it to carry out a hydrogenation reaction to obtain hydrogenated alloy powder; Step 4: The hydrogenated alloy powder from Step 3 is placed under high temperature and low hydrogen pressure conditions to carry out a dehydrogenation reaction, thereby obtaining an in-situ self-generated catalytic phase reinforced magnesium-based hydrogen storage composite material.

[0008] The preparation method of the above-mentioned in-situ self-generated catalytic phase-reinforced magnesium-based hydrogen storage composite material is characterized in that the drying process of the raw materials in step one is carried out in a drying oven at a drying temperature of 200℃~300℃ for 2h~4h. Through the above drying process, the moisture adsorbed on the surface of the raw materials is thoroughly removed, preventing the reaction of magnesium with water to produce hydrogen gas, thereby preventing possible devastating explosions and molten splashing; it can also reduce porosity and oxide inclusions in the casting, ensuring the quality of the magnesium-based alloy ingot.

[0009] The above-mentioned method for preparing an in-situ self-generated catalytic phase-enhanced magnesium-based hydrogen storage composite material is characterized in that the smelting process in step one is as follows: first, the dried magnesium block is placed in a crucible and heated in the furnace until it is completely melted; then, the dried magnesium-nickel master alloy is added; after melting, the dried magnesium-gadolinium master alloy is added and kept at a constant temperature; the resulting alloy melt is poured into a mold and air-cooled to obtain a magnesium-based alloy ingot.

[0010] The preparation method of the above-mentioned in-situ self-generated catalytic phase-enhanced magnesium-based hydrogen storage composite material is characterized in that: firstly, the dried magnesium block is placed in a crucible and heated to 600℃~700℃ in the furnace and held for 30min~50min; then, the temperature is raised to 720℃~750℃, and the dried magnesium-nickel master alloy is added and held for 20min~30min; then, the temperature is controlled at 740℃~760℃, and the dried magnesium-gadolinium master alloy is added and held for 20min~30min.

[0011] By using the above smelting process and limiting the smelting temperature and time of each step, the microstructure of the obtained magnesium-based alloy ingot is guaranteed to consist of primary α-Mg, long periodic ordered stacking structure (LPSO) phase and eutectic phase (Mg+Mg2Ni). The chemical composition of the LPSO phase is Mg-(3.7at%~5.5at%)Ni-(5.5at%~8.7at%)Gd, in which Ni and Gd elements are periodically arranged on specific crystal planes.

[0012] The above-mentioned method for preparing an in-situ self-generated catalytic phase-enhanced magnesium-based hydrogen storage composite material is characterized in that the hydrogen pressure of the hydrogenation reaction in step three is 3MPa~5MPa, the heating temperature is 300℃~400℃, and the reaction time is 3h~5h.

[0013] Through the above hydrogen absorption reaction, the composition of the alloy powder is transformed into MgH2, Mg2NiH4 and GdH2. MgH2 is generated in situ by hydrogenation reaction of primary α-Mg, Mg in the eutectic phase and Mg in the LPSO phase with hydrogen. Mg2NiH4 is generated in situ by hydrogenation reaction of Mg2Ni in the eutectic phase and Mg / Ni in the LPSO phase with hydrogen. GdH2 is generated in situ by hydrogenation reaction of Gd in the LPSO phase with hydrogen. Since Gd elements are regularly and periodically arranged in LPSO, the formed GdH2 phase can exhibit a uniform and dispersed distribution.

[0014] The above-mentioned method for preparing an in-situ self-generated catalytic phase-enhanced magnesium-based hydrogen storage composite material is characterized in that the hydrogen pressure of the dehydrogenation reaction in step four is 0.01 MPa to 0.1 MPa, the heating temperature is the same as the temperature of the hydrogenation reaction in step three, and the reaction time is 0.5 h to 1 h.

[0015] Through the above dehydrogenation reaction, the composition of the hydrogenated alloy powder is transformed into Mg, Mg2Ni, and GdH2. Mg comes from three sources: primary α-Mg hydrogenation followed by dehydrogenation, Mg in the eutectic phase hydrogenation followed by dehydrogenation, and Mg in the LPSO phase hydrogenation followed by in-situ generation. Mg2Ni is generated from Mg2Ni in the eutectic phase hydrogenation followed by dehydrogenation and from Mg / Ni in the LPSO phase hydrogenation followed by in-situ generation. GdH2 is generated in-situ from Gd in the LPSO phase after hydrogenation with hydrogen. However, due to its high thermodynamic stability, it does not decompose and dehydrogenate, and therefore can exist stably in subsequent hydrogen absorption and desorption cycles.

[0016] Based on the phase transition analysis during hydrogen absorption and desorption, it is evident that after the in-situ hydrogenation decomposition of the LPSO phase, the GdH2 phase remains stable and will not recombine after dehydrogenation. Furthermore, since GdH2 and some Mg2Ni are generated from the in-situ decomposition of the LPSO phase, and Ni and Gd elements in the LPSO phase appear periodically at the atomic scale, the GdH2 and Mg2Ni generated from the in-situ decomposition of the LPSO phase are uniformly dispersed nanoscale particles. Therefore, the Mg+Mg2Ni+GdH2 nanocomposite material obtained in this invention is a composite material.

[0017] Meanwhile, the present invention also discloses an in-situ self-generated catalytic phase enhanced magnesium-based hydrogen storage composite material, characterized in that it is prepared by the above-described method.

[0018] Compared with the prior art, the present invention has the following advantages: 1. This invention uses Mg 96.5-x Ni 3.5 Using Gd as a raw material, the material is pulverized and then subjected to hydrogen absorption and desorption processes to obtain an in-situ self-generated catalytic phase-reinforced magnesium-based hydrogen storage composite material. This composite material is composed of Mg, Mg2Ni, and GdH2. Among them, the hydrogen desorption reaction enthalpy of Mg2Ni hydride is lower than that of Mg hydride, and it can act as a "hydrogen pump" to drive the decomposition of Mg hydride to release hydrogen. GdH2 can not only increase the hydrogen absorption rate by promoting the adsorption and decomposition of hydrogen molecules, but also catalyze the decomposition of Mg hydride to release hydrogen by weakening Mg-H bonds. This effectively improves the kinetic performance of the magnesium-based hydrogen storage composite material, significantly reducing its initial hydrogen desorption temperature. At the same time, the stable nano-sized GdH2 can also act as a pinning agent to inhibit grain boundary migration, enabling the magnesium-based hydrogen storage composite material to obtain excellent cycle stability.

[0019] 2. The method of the present invention obtains magnesium-based hydrogen storage composite material with in-situ self-generated catalytic phase reinforcement through only one hydrogen absorption / desorption process, and its hydrogen desorption temperature can be reduced to 200℃. The process is simple and controllable, with low preparation cost, and is suitable for large-scale production applications.

[0020] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0021] Figure 1 These are transmission electron microscope (TEM) characterization images of the product materials prepared in Example 1 and Comparative Examples 1-2 of this invention.

[0022] Figure 2 The XRD patterns are those of the product materials prepared in Example 1 and Comparative Examples 1-2 of this invention.

[0023] Figure 3 The TPD curves of the product materials prepared in Example 1 and Comparative Examples 1-2 of this invention at a heating rate of 3℃ / min are shown.

[0024] Figure 4 The dehydrogenation curves of the product materials prepared in Example 1 and Comparative Examples 1-2 of this invention at different temperatures are shown.

[0025] Figure 5 The figures show the fitting results of the dehydrogenation kinetics of the product materials prepared in Example 1 and Comparative Examples 1-2 of this invention at different temperatures. Detailed Implementation

[0026] Example 1 This embodiment includes the following steps: Step 1: According to the chemical composition Mg 95.5 Ni 3.5 Gd1, which has an atomic percentage of 95.5 at% Mg, 3.5 at% Ni, and 1 at% Gd, was prepared by weighing magnesium, magnesium-nickel master alloy, and magnesium-gadolinium master alloy raw materials and drying them in a drying oven at 200°C for 3 hours. The following smelting process was then carried out: the dried magnesium blocks were first placed in a crucible and heated to 650°C and held for 40 minutes. Then, the temperature was raised to 740°C, and the dried magnesium-nickel master alloy was added and held for 25 minutes. Subsequently, the temperature was controlled at 750°C, and the dried magnesium-gadolinium master alloy was added again and held for 25 minutes. The resulting alloy melt was then held at 730°C for 30 minutes before being poured into a mold and air-cooled to obtain Mg. 95.5 Ni 3.5 Gd1 ingot; Step 2: Take the Mg obtained in Step 1 95.5 Ni 3.5 Gd1 ingots are mechanically crushed into alloy powder of 100-200 mesh; Step 3: Place the alloy powder from Step 2 in a hydrogen atmosphere at a pressure of 4 MPa and heat it to 350°C for 4 hours to carry out a hydrogenation reaction to obtain hydrogenated alloy powder. Step 4: Adjust the pressure of the hydrogen atmosphere to 0.1 MPa, while maintaining the temperature at 350℃, and carry out the dehydrogenation reaction of the hydrogenated alloy powder for 1 hour to obtain the Mg+Mg2Ni+GdH2 nanocomposite material, namely the in-situ self-generated catalytic phase reinforced magnesium-based hydrogen storage composite material, named Mg+Mg2Ni+GdH2-1#.

[0027] The Mg+Mg2Ni+GdH2-1# prepared in this embodiment was subjected to XRD and TEM detection, and the results are shown in the figure. Figure 1 and Figure 2 .

[0028] from Figure 1 It can be seen that the nanoscale particle phase is uniformly distributed within the particles, confirming the formation of a uniformly dispersed, stable nanoscale catalytic phase in this magnesium-based hydrogen storage composite material; from Figure 2 Diffraction peaks of Mg, Mg2Ni and GdH2 can be observed, confirming that a composite material with a phase composition of Mg+Mg2Ni+GdH2 was obtained in this embodiment.

[0029] Example 2 This embodiment includes the following steps: Step 1: According to the chemical composition Mg 94.5 Ni 3.5 Gd2, with an atomic percentage content of 94.5 at% Mg, 3.5 at% Ni, and 2 at% Gd, was prepared by weighing magnesium, magnesium-nickel master alloy, and magnesium-gadolinium master alloy raw materials and drying them in a drying oven at 200°C for 3 hours. The following smelting process was then carried out: the dried magnesium blocks were first placed in a crucible and heated to 650°C and held for 40 minutes. Then, the temperature was raised to 740°C, and the dried magnesium-nickel master alloy was added and held for 25 minutes. Subsequently, the temperature was controlled at 750°C, and the dried magnesium-gadolinium master alloy was added again and held for 25 minutes. The resulting alloy melt was then held at 730°C for 30 minutes before being poured into a mold and air-cooled to obtain Mg. 94.5 Ni 3.5 Gd2 ingots; Step 2: Take the Mg obtained in Step 1 94.5 Ni 3.5 Gd2 ingots are mechanically crushed into alloy powder of 100-200 mesh; Step 3: Place the alloy powder from Step 2 in a hydrogen atmosphere at a pressure of 4 MPa and heat it to 350°C for 4 hours to carry out a hydrogenation reaction to obtain hydrogenated alloy powder. Step 4: Adjust the pressure of the hydrogen atmosphere to 0.1 MPa, while maintaining the temperature at 350℃, and carry out the dehydrogenation reaction of the hydrogenated alloy powder for 1 hour to obtain the Mg+Mg2Ni+GdH2 nanocomposite material, namely the in-situ self-generated catalytic phase reinforced magnesium-based hydrogen storage composite material, named Mg+Mg2Ni+GdH2-2#.

[0030] Example 3 This embodiment includes the following steps: Step 1: According to the chemical composition Mg 93.5 Ni 3.5 Gd3, with an atomic percentage content of 93.5 at% Mg, 3.5 at% Ni, and 3 at% Gd, was prepared by weighing magnesium, magnesium-nickel master alloy, and magnesium-gadolinium master alloy raw materials and drying them in a drying oven at 200°C for 3 hours. The following smelting process was then carried out: the dried magnesium blocks were first placed in a crucible and heated to 650°C in the furnace, held for 40 minutes, then heated to 740°C, and the dried magnesium-nickel master alloy was added and held for 25 minutes. The temperature was then controlled at 750°C, and the dried magnesium-gadolinium master alloy was added again and held for 25 minutes. The resulting alloy melt was then held at 730°C for 30 minutes before being poured into a mold and air-cooled to obtain Mg. 93.5 Ni 3.5 Gd3 ingot; Step 2: Take the Mg obtained in Step 1 93.5 Ni 3.5 Gd3 ingots are mechanically crushed into alloy powder of 100-200 mesh; Step 3: Place the alloy powder from Step 2 in a hydrogen atmosphere at a pressure of 4 MPa and heat it to 350°C for 4 hours to carry out a hydrogenation reaction to obtain hydrogenated alloy powder. Step 4: Adjust the pressure of the hydrogen atmosphere to 0.1 MPa, while maintaining the temperature at 350℃, and carry out the dehydrogenation reaction of the hydrogenated alloy powder for 1 hour to obtain the Mg+Mg2Ni+GdH2 nanocomposite material, namely the in-situ self-generated catalytic phase reinforced magnesium-based hydrogen storage composite material, named Mg+Mg2Ni+GdH2-3#.

[0031] Example 4 This embodiment includes the following steps: Step 1: According to the chemical composition Mg 95.5 Ni 3.5 Gd1, which has an atomic percentage of 95.5 at% Mg, 3.5 at% Ni, and 1 at% Gd, was prepared by weighing magnesium, magnesium-nickel master alloy, and magnesium-gadolinium master alloy raw materials and drying them in a drying oven at 200°C for 3 hours. The following smelting process was then carried out: the dried magnesium blocks were first placed in a crucible and heated to 650°C and held for 40 minutes. Then, the temperature was raised to 740°C, and the dried magnesium-nickel master alloy was added and held for 25 minutes. Subsequently, the temperature was controlled at 750°C, and the dried magnesium-gadolinium master alloy was added again and held for 25 minutes. The resulting alloy melt was then held at 730°C for 30 minutes before being poured into a mold and air-cooled to obtain Mg. 95.5 Ni 3.5 Gd1 ingot; Step 2: Take the Mg obtained in Step 1 95.5 Ni 3.5 Gd1 ingots are mechanically crushed into alloy powder of 100-200 mesh; Step 3: Place the alloy powder from Step 2 in a hydrogen atmosphere at a pressure of 3 MPa and heat it to 400°C for 3 hours to carry out a hydrogenation reaction to obtain hydrogenated alloy powder. Step 4: Adjust the pressure of the hydrogen atmosphere to 0.1 MPa, while maintaining the temperature at 400℃, and carry out the dehydrogenation reaction of the hydrogenated alloy powder for 1 hour to obtain the Mg+Mg2Ni+GdH2 nanocomposite material, namely the in-situ self-generated catalytic phase reinforced magnesium-based hydrogen storage composite material, named Mg+Mg2Ni+GdH2-4#.

[0032] Example 5 This embodiment includes the following steps: Step 1: According to the chemical composition Mg 95.5 Ni 3.5 Gd1, which has an atomic percentage of 95.5 at% Mg, 3.5 at% Ni, and 1 at% Gd, was prepared by weighing magnesium, magnesium-nickel master alloy, and magnesium-gadolinium master alloy raw materials and drying them in a drying oven at 200°C for 3 hours. The following smelting process was then carried out: the dried magnesium blocks were first placed in a crucible and heated to 650°C and held for 40 minutes. Then, the temperature was raised to 740°C, and the dried magnesium-nickel master alloy was added and held for 25 minutes. Subsequently, the temperature was controlled at 750°C, and the dried magnesium-gadolinium master alloy was added again and held for 25 minutes. The resulting alloy melt was then held at 730°C for 30 minutes before being poured into a mold and air-cooled to obtain Mg. 95.5 Ni 3.5 Gd1 ingot; Step 2: Take the Mg obtained in Step 1 95.5 Ni 3.5 Gd1 ingots are mechanically crushed into alloy powder of 100-200 mesh; Step 3: Place the alloy powder from Step 2 in a hydrogen atmosphere at a pressure of 5 MPa and heat it to 300°C for 5 hours to carry out a hydrogenation reaction to obtain hydrogenated alloy powder. Step 4: Adjust the pressure of the hydrogen atmosphere to 0.1 MPa, while maintaining the temperature at 300℃, and carry out the dehydrogenation reaction of the hydrogenated alloy powder for 1 hour to obtain the Mg+Mg2Ni+GdH2 nanocomposite material, namely the in-situ self-generated catalytic phase reinforced magnesium-based hydrogen storage composite material, named Mg+Mg2Ni+GdH2-5#.

[0033] Example 6 This embodiment includes the following steps: Step 1: According to the chemical composition Mg 95.5 Ni3.5 Gd1, which has an atomic percentage of 95.5 at% Mg, 3.5 at% Ni, and 1 at% Gd, was prepared by weighing magnesium, magnesium-nickel master alloy, and magnesium-gadolinium master alloy raw materials and drying them in a drying oven at 200°C for 3 hours. The following smelting process was then carried out: the dried magnesium blocks were first placed in a crucible and heated to 650°C and held for 40 minutes. Then, the temperature was raised to 740°C, and the dried magnesium-nickel master alloy was added and held for 25 minutes. Subsequently, the temperature was controlled at 750°C, and the dried magnesium-gadolinium master alloy was added again and held for 25 minutes. The resulting alloy melt was then held at 730°C for 30 minutes before being poured into a mold and air-cooled to obtain Mg. 95.5 Ni 3.5 Gd1 ingot; Step 2: Take the Mg obtained in Step 1 95.5 Ni 3.5 Gd1 ingots are mechanically crushed into alloy powder of 100-200 mesh; Step 3: Place the alloy powder from Step 2 in a hydrogen atmosphere at a pressure of 4 MPa and heat it to 350°C for 4 hours to carry out a hydrogenation reaction to obtain hydrogenated alloy powder. Step 4: Adjust the pressure of the hydrogen atmosphere to 0.01 MPa, while maintaining the temperature at 350℃, and carry out the dehydrogenation reaction of the hydrogenated alloy powder for 0.5 h to obtain Mg+Mg2Ni+GdH2 nanocomposite material, namely, in-situ self-generated catalytic phase reinforced magnesium-based hydrogen storage composite material, named Mg+Mg2Ni+GdH2-6#.

[0034] Example 7 This embodiment includes the following steps: Step 1: According to the chemical composition Mg 95.5 Ni 3.5 Gd1, which has an atomic percentage of 95.5 at% Mg, 3.5 at% Ni, and 1 at% Gd, was prepared by weighing magnesium, magnesium-nickel master alloy, and magnesium-gadolinium master alloy raw materials and drying them in a drying oven at 200°C for 3 hours. The following smelting process was then carried out: the dried magnesium blocks were first placed in a crucible and heated to 650°C and held for 40 minutes. Then, the temperature was raised to 740°C, and the dried magnesium-nickel master alloy was added and held for 25 minutes. Subsequently, the temperature was controlled at 750°C, and the dried magnesium-gadolinium master alloy was added again and held for 25 minutes. The resulting alloy melt was then held at 730°C for 30 minutes before being poured into a mold and air-cooled to obtain Mg. 95.5 Ni 3.5 Gd1 ingot; Step 2: Take the Mg obtained in Step 1 95.5 Ni 3.5 Gd1 ingots are mechanically crushed into alloy powder of 100-200 mesh; Step 3: Place the alloy powder from Step 2 in a hydrogen atmosphere at a pressure of 4 MPa and heat it to 350°C for 4 hours to carry out a hydrogenation reaction to obtain hydrogenated alloy powder. Step 4: Adjust the pressure of the hydrogen atmosphere to 0.05 MPa, while maintaining the temperature at 350℃, and carry out the dehydrogenation reaction of the hydrogenated alloy powder for 0.75 h to obtain Mg+Mg2Ni+GdH2 nanocomposite material, namely, in-situ self-generated catalytic phase reinforced magnesium-based hydrogen storage composite material, named Mg+Mg2Ni+GdH2-7#.

[0035] Comparative Example 1 The difference between this comparative example and Example 1 is that magnesium ingots are prepared in step one; and the material obtained in step four is Mg material.

[0036] Comparative Example 2 The difference between this comparative example and Example 1 is that the chemical composition in step one is Mg. 96.5 Ni 3.5 That is, the Mg content is 96.5 at and the Ni content is 3.5 at, by atomic percentage; the material obtained in step four is Mg 96.5 Ni 3.5 Composite materials.

[0037] Performance testing (1) The product materials prepared in Examples 1-7 and Comparative Examples 1-2 of the present invention were hydrogenated at 350℃ / 3MPa for 3h and then cooled to room temperature. Dehydrogenation tests were performed as a function of temperature. The heating rate was set to 3℃ / min and the hydrogen pressure was adjusted to 0.1MPa. The TPD curves of the test results are shown below. Figure 3 As shown.

[0038] from Figure 3 It can be seen that, under the test conditions, the initial hydrogen release temperature of the Mg prepared in Comparative Example 1 after hydrogenation is approximately 333℃, while that of the Mg prepared in Comparative Example 2 is... 96.5 Ni 3.5 The initial hydrogen release temperature after hydrogenation is approximately 217°C. The initial hydrogen release temperature of Mg+Mg2Ni+GdH2-1# prepared in Example 1 is higher than that of Mg... 96.5 Ni 3.5 The temperature further decreased, remaining around 200°C, indicating that the preparation process of this invention significantly reduced the initial hydrogen release temperature of the material.

[0039] (2) The product materials prepared in Examples 1-7 and Comparative Examples 1-2 of this invention were subjected to hydrogen absorption and desorption tests at different temperatures. The test results are shown in Table 1 below, and the dehydrogenation curves were recorded. The results are as follows: Figure 4 As shown.

[0040] Table 1. Time required for the product materials prepared in Examples 1-7 and Comparative Examples 1-2 to achieve complete hydrogen desorption at different temperatures.

[0041] Based on Table 1 Figure 4 It can be seen that for the same material, the hydrogen release temperature increases with increasing temperature; at the same reaction temperature, the in-situ self-generated catalytic phase-reinforced magnesium-based hydrogen storage composite materials prepared in Examples 1-7 of this invention require less time to completely release hydrogen than the Mg prepared in Comparative Example 1 and the Mg prepared in Comparative Example 2. 96.5 Ni 3.5 .

[0042] (3) To quantitatively compare the hydrogen desorption kinetics of the product materials prepared in Example 1 and Comparative Examples 1-2, the Johnson-Mehl-Avrami-Kolmogorow (JMAK) kinetic model of Equation (1) and Equation (2) were used for data fitting and apparent activation energy calculation. The results are as follows: Figure 5 As shown.

[0043] (1) (2) in, α The corresponding reaction time is t The ratio of the products of the initial reaction to the total products of the reaction process, and 0 < α <1; n The reaction order is... k The rate constant of the reaction, E a The apparent activation energy of hydrogen absorption and desorption reactions. A It is a constant. R The gas constant is T This is absolute temperature, measured in Kelvin (K).

[0044] Figure 5 This is a graph showing the fitting results of the dehydrogenation kinetics of the product materials prepared in Example 1 and Comparative Examples 1-2 of this invention at different temperatures. Figure 5 It can be seen that the Mg+Mg2Ni+GdH2-1# prepared in Example 1 has the lowest apparent activation energy for the dehydrogenation reaction, that is, the lowest energy barrier needs to be overcome for the dehydrogenation reaction to occur, and the best kinetic performance; the Mg prepared in Comparative Example 2 without the addition of Gd element 96.5 Ni 3.5 The apparent activation energy is significantly lower than that of magnesium prepared in Comparative Example 1, which is attributed to the performance optimization effect of Mg2Ni; while the Mg+Mg2Ni+GdH2-1# prepared in Example 1 is significantly lower than that of Mg prepared in Comparative Example 2. 96.5 Ni 3.5The performance is further improved, thanks to the in-situ formed nano-GdH2 catalytic phase, which indicates that the in-situ self-generated catalytic phase enhanced magnesium-based hydrogen storage composite material prepared by the technical solution of the present invention has excellent hydrogen storage performance.

[0045] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing an in-situ self-generated catalytic phase-reinforced magnesium-based hydrogen storage composite material, characterized in that, The method includes the following steps: Step 1: According to the chemical composition Mg 96.5-x Ni 3.5 Gd x , where 1≤ x ≤3, weigh out magnesium, magnesium-nickel master alloy and magnesium-gadolinium master alloy raw materials and dry them, then smelt them to obtain magnesium-based alloy ingots; Step 2: Mechanically crush the magnesium-based alloy ingot obtained in Step 1 into alloy powder of 100-200 mesh; Step 3: Place the alloy powder from Step 2 in a hydrogen atmosphere and heat it to carry out a hydrogenation reaction to obtain hydrogenated alloy powder; Step 4: The hydrogenated alloy powder from Step 3 is placed under high temperature and low hydrogen pressure conditions to carry out a dehydrogenation reaction, thereby obtaining an in-situ self-generated catalytic phase reinforced magnesium-based hydrogen storage composite material.

2. The method for preparing an in-situ self-generated catalytic phase-reinforced magnesium-based hydrogen storage composite material according to claim 1, characterized in that, The drying process of the raw materials described in step one is carried out in a drying oven at a temperature of 200℃~300℃ for 2h~4h.

3. The method for preparing an in-situ self-generated catalytic phase-reinforced magnesium-based hydrogen storage composite material according to claim 1, characterized in that, The smelting process described in step one is as follows: First, put the dried magnesium block into a crucible and heat it in the furnace until it is completely melted. Then, add the dried magnesium-nickel master alloy. After it melts, add the dried magnesium-gadolinium master alloy and keep it warm. Pour the resulting alloy melt into a mold and air cool it to obtain a magnesium-based alloy ingot.

4. The method for preparing an in-situ self-generated catalytic phase-reinforced magnesium-based hydrogen storage composite material according to claim 3, characterized in that, First, place the dried magnesium block into a crucible and heat it to 600℃~700℃ in the furnace and hold it for 30min~50min. Then, heat it to 720℃~750℃, add the dried magnesium-nickel master alloy and hold it for 20min~30min. After that, control the temperature to 740℃~760℃ and add the dried magnesium-gadolinium master alloy and hold it for 20min~30min.

5. The method for preparing an in-situ self-generated catalytic phase-reinforced magnesium-based hydrogen storage composite material according to claim 1, characterized in that, In step three, the hydrogen pressure for the hydrogenation reaction is 3 MPa to 5 MPa, the heating temperature is 300°C to 400°C, and the reaction time is 3 to 5 hours.

6. The method for preparing an in-situ self-generated catalytic phase-reinforced magnesium-based hydrogen storage composite material according to claim 1, characterized in that, The hydrogen pressure for the dehydrogenation reaction in step four is 0.01 MPa to 0.1 MPa, the heating temperature is the same as that for the hydrogenation reaction in step three, and the reaction time is 0.5 h to 1 h.

7. An in-situ self-generated catalytic phase-reinforced magnesium-based hydrogen storage composite material, characterized in that, It is prepared by the method described in any one of claims 1 to 6.

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