Magnesium-based hydrogen storage material and preparation method thereof

Abstract

The invention relates to a magnesium-based hydrogen storage material and a preparation method thereof, and belongs to the technical field of hydrogen storage alloy materials and preparation thereof. The hydrogen storage material is an Mg-5Ni alloy with Sm powder uniformly distributed on the surface layer and an amorphous / nanocrystalline structure in the interior. The Sm powder is wrapped by the surface layer of the Mg-5Ni alloy to form composite powder of a core-shell structure; the hydrogen storage material is prepared from Mg-5Ni alloy powder and Sm powder as raw materials, and the raw materials are mixed and then subjected to dry ball milling. The hydrogen absorption and desorption kinetics of the existing magnesium-based hydrogen storage material can be effectively improved, the hydrogen desorption activation energy of the magnesium-based hydrogen storage material is reduced, and the problem that a solid additive is difficult to uniformly distribute on the surface is solved.

Description

Technical Field

[0001] This invention relates to a magnesium-based hydrogen storage material and its preparation method, belonging to the technical field of hydrogen storage alloy materials and their preparation. Background Technology

[0002] Energy, as an essential foundation for human society's life, development, and construction, will inevitably require more energy sources over time. However, with the rapid depletion of traditional fossil fuel reserves and the significant increase in greenhouse gases from their combustion causing adverse climate change, obtaining green and environmentally friendly energy has become a global focus. Hydrogen energy, as a clean and renewable energy source, plays a crucial role in solving today's energy problems. It is not only abundant and environmentally friendly but also possesses high combustion energy and high energy conversion efficiency. Furthermore, hydrogen energy offers significant advantages as a highly efficient energy storage medium. Therefore, hydrogen energy is widely regarded as a leading option for future energy solutions and a potential alternative fuel. As a crucial link in the development of hydrogen energy, hydrogen storage is one of the key technologies urgently needing to be addressed. Solid-state hydrogen storage alloys, due to their high volumetric hydrogen storage density, ease of operation, and advantages of high safety and low cost, have promising prospects for large-scale application.

[0003] Among various hydrogen storage alloys, Mg-Ni-based hydrogen storage alloys have attracted increasing attention from researchers. However, Mg-Ni-based alloys still face some limitations in their application development. For example, magnesium-based hydrogen storage materials have high hydrogen absorption and desorption temperatures (300 ℃ ~ 400 ℃) and poor kinetic and thermodynamic properties. Without modification, they cannot meet the requirements of practical applications. This is mainly due to the slow dissociation of hydrogen on the magnesium surface and the slow diffusion within the alloy and hydrides. Therefore, it is essential to effectively improve the hydrogen absorption and desorption performance of magnesium-based alloys and provide an ideal magnesium-based hydrogen storage material that is feasible for large-scale industrial application and can serve as a future hydrogen storage and transportation material. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, the present invention aims to provide a magnesium-based hydrogen storage material and its preparation method, which can effectively improve the hydrogen absorption and desorption kinetics of existing magnesium-based hydrogen storage materials, reduce their hydrogen desorption activation energy, and solve the problem that solid additives are difficult to distribute uniformly on the surface.

[0005] To achieve the objectives of this invention, the following technical solutions are provided.

[0006] A magnesium-based hydrogen storage material, wherein the hydrogen storage material is a Mg-5Ni alloy with a uniformly distributed samarium (Sm) powder particle on the surface and an amorphous / nanocrystalline structure inside; the samarium powder particle is coated with the Mg-5Ni alloy to form a core-shell structured composite powder.

[0007] Furthermore, the hydrogen storage material uses Sm powder and Mg-5Ni alloy powder as raw materials, wherein the mass ratio of Mg-5Ni alloy powder to samarium powder is 15~45 : 0.79~1.15; further, the mass ratio of Mg-5Ni alloy powder to samarium powder is 19~39 : 1.

[0008] A method for preparing the magnesium-based hydrogen storage material according to the present invention, the method comprising the following steps: A magnesium-based hydrogen storage material was obtained by mixing Mg-5Ni alloy powder and Sm powder and then dry ball milling the mixture.

[0009] Furthermore, the particle size of Mg-5Ni alloy powder is 100 mesh to 300 mesh, and the particle size of samarium powder is 100 mesh to 300 mesh.

[0010] Furthermore, the ball-to-material mass ratio in the ball mill is 30 to 50:1, the ball mill speed is 150 r / min to 400 r / min, and the ball milling time is 20 h to 40 h.

[0011] Furthermore, the particle size of the Mg-5Ni alloy powder is 200 mesh, and the particle size of the samarium powder is 150 mesh; the ball-to-material mass ratio of the ball mill is 40:1, the ball milling speed is 350 r / min, and the ball milling time is 40 h.

[0012] Beneficial effects (1) This invention provides a magnesium-based hydrogen storage material. The internal microstructure of the material is an amorphous / nanocrystalline Mg-5Ni alloy. Simultaneously, Sm powder is added to enhance the surface properties of the Mg-5Ni alloy powder by uniformly distributing it on the surface. By simultaneously controlling both the internal microstructure and surface properties of the material, the hydrogen storage performance is significantly improved. Experimental results show that the material can be activated after one hydrogen absorption / desorption cycle at 633 K and 3.5 MPa, and exhibits excellent hydrogen absorption performance from 573 K to 633 K. Especially at 573 K, the hydrogen absorption capacity exceeds 1.8 wt.% within 1 h. (2) The present invention provides a magnesium-based hydrogen storage material. The material utilizes the characteristic that hydrogen absorption reaction usually occurs on the surface of the material and uses element Sm doping to generate Sm3H7. Sm3H7 has a catalytic effect, which can not only accelerate the speed of hydrogen atoms passing through the Mg surface, but also enable more hydrogen atoms to combine with Mg, thereby alleviating the diffusion restriction of H at low temperature and effectively improving the hydrogen absorption and desorption performance of magnesium-based alloys. In addition, for the reversible reaction of MgH2 and Mg2NiH4, Sm3H7 can accelerate the reaction by weakening the bond energy between Mg-H bonds. (3) The present invention provides a magnesium-based hydrogen storage material, which utilizes the complementary effect between Mg-5Ni alloy and Sm powder to explore the optimal ratio range of the two, which greatly improves the hydrogen storage performance of the material at lower temperatures. (4) This invention provides a method for preparing magnesium-based hydrogen storage materials. The method employs dry ball milling, which improves the internal microstructure of Mg-5Ni alloy powder into an amorphous / nanocrystalline structure. Simultaneously, the additives Sm powder and samarium powder have a higher hardness than magnesium, thus aiding in grinding and effectively enhancing the refinement of magnesium. During high-energy ball milling, the Mg-5Ni alloy powder, with its excellent ductility, undergoes plastic deformation under intense mechanical force, physically coating the brittle samarium powder particles to form a core-shell composite powder. This dense metal matrix effectively isolates the samarium powder from direct contact with external oxidizing atmospheres (such as oxygen and water vapor), effectively preventing samarium powder ablation. (5) The present invention provides a method for preparing magnesium-based hydrogen storage material. In the method, the particle size of Mg-5Ni alloy powder is preferably 100-300 mesh and the particle size of samarium powder is preferably 100-300 mesh. The powder can effectively accept the impact energy of the grinding media and has good powder flowability, which helps to promote crushing in the early stage of ball milling. It can effectively optimize ball milling efficiency and energy utilization, balance the dynamic process of crushing and cold welding, ensure process safety and operation convenience, and take into account the cost and availability of raw materials. Furthermore, the preferred ball-to-material mass ratio for ball milling is 30-50:1, the ball milling speed is 150 r / min-400 r / min, and the ball milling time is 20 h-40 h. This can overcome the kinetic and thermodynamic bottlenecks in material preparation, achieve extreme grain refinement, complete alloying or amorphization, thereby obtaining high-performance materials; improve grinding efficiency, reduce equipment wear and material contamination, avoid grinding failure caused by centrifugal effect, and alleviate particle agglomeration and potential structural degradation. (6) The present invention provides a method for preparing a magnesium-based hydrogen storage alloy. The method is simple and stable and easy to promote on a large scale in industry. The prepared magnesium-based hydrogen storage alloy is expected to become an excellent hydrogen storage alloy for future applications such as hydrogen storage, transportation, hydrogen fuel cells and hydrogen energy engines. Attached Figure Description

[0013] Figure 1 The scanning electron microscope (SEM) image of (Mg-5Ni)-2.5Sm prepared in Example 1; Figure 2 The SEM image of (Mg-5Ni)-5Sm prepared in Example 2; Figure 3Transmission electron microscopy (TEM) image and energy dispersive spectroscopy (EDS) spectrum of (Mg-5Ni)-2.5Sm prepared in Example 1; Figure 4 Hydrogen absorption performance of (Mg-5Ni)-2.5Sm prepared in Example 1 at 633 K; Figure 5 The hydrogen absorption performance of (Mg-5Ni)-5Sm prepared in Example 2 at 633 K; Figure 6 The hydrogen absorption performance of Mg-5Ni prepared in Comparative Example 1 at 633 K; Figure 7 The isothermal hydrogen absorption performance of the magnesium-based hydrogen storage materials prepared in Examples 1 and 2 at 613 K and 3.5 MPa; Figure 8 The isothermal hydrogen absorption performance of the magnesium-based hydrogen storage materials prepared in Examples 1 and 2 at 593 K and 3.5 MPa; Figure 9 The isothermal hydrogen absorption performance of the magnesium-based hydrogen storage materials prepared in Examples 1 and 2 at 573 K and 3.5 MPa; Figure 10 The isothermal hydrogen desorption performance of the magnesium-based hydrogen storage materials prepared in Examples 1 and 2 at 613 K and 3.5 MPa; Figure 11 The isothermal hydrogen desorption performance of the magnesium-based hydrogen storage materials prepared in Examples 1 and 2 at 593 K and 3.5 MPa; Figure 12 The isothermal hydrogen desorption performance of the magnesium-based hydrogen storage materials prepared in Examples 1 and 2 at 573 K and 3.5 MPa. Detailed Implementation

[0014] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0015] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0016] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0017] Example 1 A method for preparing a magnesium-based hydrogen storage material, comprising the following steps: In an argon-filled glove box, 1.95 g of Mg-5Ni alloy powder and 0.05 g of Sm powder were weighed out, with a mass ratio of Mg-5Ni alloy powder to Sm powder of 39:1. The particle size of the Mg-5Ni alloy powder was 200 mesh, and the particle size of the Sm powder was 150 mesh. They were placed in a 100 mL ball mill jar for dry ball milling. The ball mill jar was filled with stainless steel balls with a diameter of 4 mm to 8 mm as grinding balls, with a ball-to-material mass ratio of 40:1. The ball milling speed was set to 350 r / min, and the ball milling time was 40 h. To prevent local overheating during ball milling, a forward and reverse rotation mode was adopted, and the rotation was stopped for 30 min after every 30 min of operation. A magnesium-based hydrogen storage material was prepared, which is abbreviated as (Mg-5Ni)-2.5Sm.

[0018] Example 2 The difference between this embodiment and Example 1 is that 1.95 g of Mg-5Ni alloy powder and 0.10 g of Sm powder were weighed, that is, the mass ratio of Mg-5Ni alloy powder to Sm powder was 19:1; the remaining steps and conditions were the same as in Example 1, and a magnesium-based hydrogen storage material was prepared, which is simply referred to as (Mg-5Ni)-5Sm.

[0019] Comparative Example 1 The difference between this comparative example and Example 1 is that Sm powder was not used, and the Mg-5Ni alloy powder was ball-milled separately; the remaining steps and conditions were the same as in Example 1, resulting in a magnesium-based hydrogen storage material, referred to as Mg-5Ni.

[0020] Performance testing experiment The magnesium-based hydrogen storage materials prepared in the examples and comparative examples were observed and tested as follows: (1) Observation of surface micromorphology The surface microstructure of the magnesium-based hydrogen storage materials prepared in Examples 1 and 2 was characterized using scanning electron microscopy and transmission electron microscopy, and the results are as follows: Figure 1 As shown in Figure 3, samarium powder is coated with a Mg-5Ni alloy layer to form a core-shell structured composite powder, which is uniformly distributed on the surface of the Mg-5Ni alloy powder and has a uniform particle size distribution. The particle size of the magnesium-based hydrogen storage material is 0.8 μm to 4 μm. (2) X-ray diffraction (XRD) test XRD testing revealed that the Mg-5Ni alloy has an amorphous / nanocrystalline structure. (2) Hydrogen absorption performance test The isothermal hydrogen absorption performance of the magnesium-based hydrogen storage materials prepared in Examples 1, 2, and Comparative Example 1 was tested using a pressure-composition-temperature (PCT) analyzer manufactured by the Beijing General Research Institute of Nonferrous Metals. The sample size for each test was 0.6 g. The magnesium-based hydrogen storage materials used as test samples underwent hydrogen absorption-vacuum activation. Testing began when the hydrogen absorption reached more than 95% of the theoretical capacity. The samples were heated in a furnace at a set temperature with a heating rate of 5 °C / min and a hydrogen pressure of 3.5 MPa. The hydrogen absorption performance test results of the magnesium-based hydrogen storage materials prepared in Examples 1, 2, and Comparative Example 1 at different temperatures are as follows: Figure 4 As shown in Figure 9, the test results show that (Mg-5Ni)-2.5Sm and (Mg-5Ni)-5Sm can be activated after one hydrogen absorption and desorption cycle under the conditions of 633 K and 3.5 MPa, demonstrating the positive effect of the additive samarium powder on the activation performance of magnesium-based hydrogen storage materials.

[0021] At low temperatures, (Mg-5Ni)-2.5Sm and (Mg-5Ni)-5Sm exhibit superior hydrogen absorption kinetics. This is because the magnesium is refined and the generated Sm3H7 has a catalytic effect, which not only accelerates the passage of hydrogen atoms through the Mg surface but also allows more hydrogen atoms to combine with Mg, alleviating the diffusion restriction of H at low temperatures and effectively improving the hydrogen absorption and desorption kinetics of magnesium-based alloys. For the reversible reactions of MgH2 and Mg2NiH4, Sm3H7 can accelerate the reaction by weakening the bond energy between Mg-H bonds.

[0022] Among them, (Mg-5Ni)-2.5Sm showed the best performance. It can be activated after one hydrogen absorption and desorption cycle and also exhibits excellent hydrogen absorption performance at 573 K ~ 633 K. In particular, at 573 K, the hydrogen absorption capacity exceeds 1.8 wt.% within 1 hour, based on 100% of the mass of magnesium-based hydrogen storage material.

[0023] (3) Hydrogen release performance test The isothermal hydrogen desorption performance of the magnesium-based hydrogen storage materials prepared in Examples 1 and 2 was tested using a PCT tester manufactured by the Beijing General Research Institute of Nonferrous Metals. First, the magnesium-based hydrogen storage materials used as samples were fully absorbing hydrogen. Then, high-pressure hydrogen gas was used to suppress the hydrogen desorption behavior during the heating process. The test results of the hydrogen desorption performance of the magnesium-based hydrogen storage materials prepared in Examples 1 and 2 at different temperatures are as follows: Figure 10 As shown in Figure 12. The test results show that (Mg-5Ni)-2.5Sm exhibits the fastest hydrogen desorption rate and the highest hydrogen desorption capacity at 573 K ~ 613 K.

Claims

1. A magnesium-based hydrogen storage material, characterized in that: The hydrogen storage material is a Mg-5Ni alloy with a uniformly distributed Sm powder on the surface and an amorphous / nanocrystalline structure inside; the Sm powder is coated by the Mg-5Ni alloy surface to form a core-shell structured composite powder.

2. The magnesium-based hydrogen storage material according to claim 1, characterized in that: The hydrogen storage material uses Sm powder and Mg-5Ni alloy powder as raw materials, with a mass ratio of Mg-5Ni alloy powder to Sm powder of 15~45 : 0.79~1.

15.

3. A magnesium-based hydrogen storage material according to claim 2, characterized in that: The mass ratio of Mg-5Ni alloy powder to Sm powder is 19 ~ 39 :

1.

4. A method for preparing a magnesium-based hydrogen storage material according to any one of claims 1 to 3, characterized in that: A magnesium-based hydrogen storage material was obtained by mixing Mg-5Ni alloy powder and Sm powder and then dry ball milling the mixture.

5. A method for preparing a magnesium-based hydrogen storage material according to claim 4, characterized in that: The particle size of Mg-5Ni alloy powder is 100 mesh to 300 mesh, and the particle size of Sm powder is 100 mesh to 300 mesh.

6. A method for preparing a magnesium-based hydrogen storage material according to claim 4 or 5, characterized in that: The ball-to-material mass ratio in the ball mill is 30-50:1, the ball mill speed is 150 r / min-400 r / min, and the ball milling time is 20 h-40 h.

7. A method for preparing a magnesium-based hydrogen storage material according to claim 4, characterized in that: The particle size of Mg-5Ni alloy powder is 200 mesh, and the particle size of Sm powder is 150 mesh; the ball-to-material mass ratio of the ball mill is 40:1, the ball milling speed is 350 r / min, and the ball milling time is 40 h.

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