A nano-boron composite magnesium-based hydrogen storage material and its preparation method

Abstract

The present invention discloses a nano-boron composite magnesium-based hydrogen storage material and a preparation method thereof, belonging to the technical field of new energy material preparation and development. The nano-boron composite magnesium-based hydrogen storage material of the present invention comprises, by mass fraction, 1-30% boron and the balance magnesium. During the smelting process, boron atoms aggregate into boron nanostructures (nanotubes, nanosheets, nanohorns, and nanospheres) and are partially embedded in the magnesium, enhancing the diffusion of hydrogen and magnesium. The nano-boron structures (nanotubes, nanosheets, nanohorns, and nanospheres) provide an intermediate medium for the magnesium-based hydrogen storage material during hydrogen absorption and desorption, effectively optimizing the hydrogen storage conditions of the magnesium-based hydrogen storage material.

Description

Technical Field

[0001] This invention belongs to the field of new energy material preparation and development technology, and relates to a nano-boron composite magnesium-based hydrogen storage material and its preparation method. Background Technology

[0002] Hydrogen storage materials are one of the key technologies for realizing hydrogen energy applications. They can store and release hydrogen, which is crucial for the transportation and storage of hydrogen energy. The applications of hydrogen storage materials are mainly concentrated in fuel cells, distributed energy supply, and new energy vehicles. Existing types of hydrogen storage materials include physically adsorbed hydrogen storage materials, metal hydride-based hydrogen storage alloys, organic liquid hydrogen storage materials, liquid ammonia hydrogen storage materials, and coordination hydrides. Metal hydride-based hydrogen storage is currently the most promising and rapidly developing solid-state hydrogen storage method, possessing advantages such as high hydrogen volume density, ease of operation, convenient transportation, low cost, good safety, and good reversible recycling. However, metal hydride-based hydrogen storage alloys have relatively low mass efficiency.

[0003] Magnesium-based hydrogen storage materials are considered highly promising solid-state hydrogen storage materials due to their high theoretical gravimetric and volumetric hydrogen storage densities, as well as the abundance and low cost of magnesium resources. Cubic Mg₂Ni, with a theoretical hydrogen storage capacity of 3.6 wt%, is the earliest studied magnesium-based hydrogen storage material. Mg₂Ni undergoes a hydrogen absorption reaction at 300℃ and 2 MPa to form the corresponding hydride Mg₂NiH₄. MgH₄, as a hydrogen storage material, has a theoretical hydrogen storage capacity of 7.6 wt%, which is higher than that of Mg₂Ni, meeting the target for mobile hydrogen storage. However, its poor kinetic performance hinders its practical application. Therefore, improving the hydrogen absorption and dehydrogenation rates of magnesium-based hydrogen storage alloys, thereby enabling magnesium-based hydrogen storage materials to possess superior hydrogen storage conditions, is of great significance.

[0004] Therefore, it is necessary to provide a nano-boron composite magnesium-based hydrogen storage material and its preparation method, optimize the hydrogen storage conditions of the magnesium-based hydrogen storage material, and enable the magnesium-based hydrogen storage material to achieve better hydrogen storage conditions. Summary of the Invention

[0005] To overcome the problems in the prior art, this invention prepares a nano-boron composite magnesium-based hydrogen storage material. Boron is combined with magnesium in a nanoscale structure (nanotubes, nanosheets, nanoangles, nanospheres). The nanoscale structure formed by the aggregation of boron atoms can improve the internal microstructure of the composite magnesium-based hydrogen storage material, enhance the activity of magnesium, and serve as an intermediate medium connecting magnesium and the external environment. Hydrogen atoms can diffuse into magnesium through the boron nanostructure, thereby enhancing the hydrogen absorption and desorption rate of the magnesium-based hydrogen storage material and giving it superior hydrogen storage conditions.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0007] This invention proposes a nano-boron composite magnesium-based hydrogen storage material, which, by mass fraction, comprises: boron: 1-30%, with the balance being magnesium. In the nano-boron composite magnesium-based hydrogen storage material, boron atoms aggregate into a nanoscale structure and are composited with magnesium, with nano-boron serving as an intermediate medium in the hydrogen absorption and release processes.

[0008] In another aspect, the present invention provides a method for preparing the above-mentioned hydrogen storage material, the method comprising the following steps:

[0009] (1) A balanced amount of magnesium powder and magnesium diboride powder are smelted. During the smelting process, a protective gas is introduced and a refining agent is added to the melt. After the melt is cooled, a smelted body is obtained.

[0010] (2) The melt obtained in step (1) is broken into fragments, and the fragments are ball-milled in a non-oxidizing atmosphere or vacuum environment to obtain nano-boron composite magnesium-based hydrogen storage material.

[0011] Preferably, in step (1), the melting temperature is 700-1500℃ and the holding time is 1-5h.

[0012] Preferably, in step (1), the refining agent is a mixture of KCl, MgCl2, and CaF2, and the mass of the refining agent added is 2% of the total mass of magnesium powder and magnesium diboride. The refining agent used in the refining process of magnesium alloys can be used as the refining agent of this invention.

[0013] Preferably, in step (1), when the melting temperature rises to 350°C, the protective gas is introduced. During the cooling process, when the temperature drops to 350°C, the protective gas is stopped. The flow rate of the protective gas is 3-6 L / h.

[0014] Preferably, in step (1), the protective gas is one of argon and carbon dioxide or a mixture of argon and carbon dioxide, wherein the volume ratio of carbon dioxide to argon in the mixture is CO2:Ar = 8:2.

[0015] Preferably, in step (2), the ball-to-material ratio is 20-120:1, the ball milling speed is 300-900 rpm, and the ball milling time is 12-60 h.

[0016] Preferably, in step (2), the ball milling process is carried out in a cycle of 30 minutes of ball milling followed by 20 minutes of intermittent milling.

[0017] As a preferred option, the smelting equipment is preheated to 150-250°C before smelting magnesium powder and magnesium diboride powder.

[0018] Preferably, in step (2), the non-oxidizing atmosphere is argon.

[0019] The beneficial effects of this invention are:

[0020] 1. This invention prepares a nano-boron composite magnesium-based hydrogen storage material containing nanoscale structures (nanotubes, nanosheets, nanoangles, and nanospheres), improves the internal microstructure of the magnesium-based hydrogen storage material, and utilizes the boron nanostructure as an intermediate medium in the hydrogen absorption and desorption process, effectively enhancing the hydrogen absorption and desorption rates of the magnesium-based hydrogen storage material, thereby optimizing the hydrogen storage effect of the magnesium-based hydrogen storage material.

[0021] 2. The preparation process of this invention is pollution-free, does not produce toxic substances, and is simple, easy to implement, and has low preparation cost, making it suitable for industrial application. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the preparation method of the nano-boron composite magnesium-based hydrogen storage material of the present invention;

[0023] Figure 2 This is a schematic diagram of the microstructure of the nano-boron composite magnesium-based hydrogen storage material of the present invention, simulating the hydrogen absorption process.

[0024] Figure 3 This is a schematic diagram of the microstructure of the nano-boron composite magnesium-based hydrogen storage material of the present invention, simulating the hydrogen release process. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to specific embodiments.

[0026] In this embodiment of the invention, all chemical reagents not specified were commercially available analytical grade reagents used in the experiments.

[0027] Example 1

[0028] This embodiment prepares a nano-boron composite magnesium-based hydrogen storage material according to the following method:

[0029] (1) Weigh 68g of magnesium powder and 32g of magnesium diboride alloy powder in a glove box filled with Ar gas, totaling 100g, of which boron accounts for 15% by mass. Weigh 2g of refining agent.

[0030] (2) First, put the crucible into the melting furnace, heat it to 150°C, preheat it for 30 minutes, then add the weighed magnesium powder and magnesium diboride into the crucible, continue to heat it, and when the temperature in the furnace reaches 350°C, introduce CO2-Ar mixed gas at a flow rate of 3.5 L / h. In the mixed gas, the volume ratio of CO2 to Ar is 8:2. When the temperature reaches 900°C, add the refining agent, stir for 2 minutes, keep it warm for 1.5 hours, and continue to circulate gas during the process. The gas flow rate can be increased appropriately during the stirring process.

[0031] (3) After the heat preservation is completed, the material is cooled. Gas flow is stopped at 350℃, and cooling continues until room temperature. The resulting block material is then removed, cut into small pieces, and placed in a ball mill for ball milling. The ball milling is performed under an Ar atmosphere (Ar gas is introduced into the equipment before ball milling to expel air and create an Ar atmosphere). The ball-to-material ratio is 70:1, the ball milling speed is 800 rpm, and the ball milling time is 30 hours. After ball milling, the material is cooled, and the powder is removed to obtain the nano-boron composite magnesium-based hydrogen storage material. In the nano-boron composite magnesium-based hydrogen storage material prepared in this embodiment, boron atoms aggregate into a nanotube structure.

[0032] The microstructure diagram of the hydrogen absorption process of the nano-boron composite magnesium-based hydrogen storage material prepared in this embodiment was obtained through first-principles simulation calculations, as shown in the figure below. Figure 2 As shown, the white atoms are hydrogen, the black atoms are boron, and the gray atoms are magnesium. Figure 2 It can be seen that boron itself can react with hydrogen, and the specific way boron nanotubes are combined with magnesium is through partial embedding in magnesium, causing lattice distortion in magnesium and enhancing its activity. The microstructure of the boron nanotube-magnesium composite hydrogen storage material prepared in this embodiment, obtained through first-principles simulation calculations, is shown in the following diagram. Figure 3 As shown, through Figure 3 It can be seen that magnesium atoms aggregate on the surface of boron nanotubes, and some hydrogen atoms are adsorbed around the boron nanotubes. This indicates that boron nanotubes can promote the movement of magnesium and hydrogen atoms, thereby accelerating the rate of hydrogen absorption and release and optimizing the hydrogen storage conditions of composite magnesium-based hydrogen storage materials.

[0033] Example 2

[0034] This embodiment prepares a nano-boron composite magnesium-based hydrogen storage material according to the following method:

[0035] (1) Weigh 87g of magnesium powder and 13g of magnesium diboride alloy powder in a glove box filled with Ar gas, totaling 100g, of which boron accounts for 6% of the mass. Weigh 2g of refining agent.

[0036] (2) First, put the crucible into the melting furnace, heat it to 150°C, preheat it for 30 minutes, then add the weighed magnesium powder and magnesium diboride into the crucible, continue to heat it, and when the temperature in the furnace reaches 350°C, introduce CO2-Ar mixed gas at a flow rate of 4L / h. In the mixed gas, the volume ratio of CO2 to Ar is 8:2. When the temperature reaches 800°C, add the refining agent, stir for 2 minutes, keep it warm for 2 hours, and continue to circulate gas during the process. The gas flow rate can be increased appropriately during the stirring process.

[0037] (3) After the heat preservation is completed, the material is cooled. When the temperature is 350℃, the gas supply is stopped and the material is cooled to room temperature. The resulting block material is taken out, cut into small pieces, and put into a ball milling device for ball milling. The ball milling process is carried out in an Ar atmosphere with a ball-to-material ratio of 20:1, a ball milling speed of 800 rpm, and a ball milling time of 30 h. After the ball milling is completed, the material is cooled and the powder is taken out to obtain nano-boron composite magnesium-based hydrogen storage material.

[0038] The nano-boron composite magnesium-based hydrogen storage material prepared in this embodiment has similar performance to the nano-boron composite magnesium-based hydrogen storage material in Example 1.

[0039] Example 3

[0040] This embodiment prepares a nano-boron composite magnesium-based hydrogen storage material according to the following method:

[0041] (1) Weigh 97.8g of magnesium powder and 2.2g of magnesium diboride alloy powder in a glove box filled with Ar gas, totaling 100g, of which boron accounts for 1% by mass. Weigh 2g of refining agent.

[0042] (2) First, put the crucible into the melting furnace, heat it to 250°C, preheat it for 30 minutes, then add the weighed magnesium powder and magnesium diboride into the crucible, continue to heat it, and when the temperature in the furnace reaches 350°C, introduce CO2-Ar mixed gas at a flow rate of 3L / h. In the mixed gas, the volume ratio of CO2 to Ar is 8:2. When the temperature reaches 700°C, add the refining agent, stir for 2 minutes, keep it warm for 1 hour, and continue to circulate gas during the process. The gas flow rate can be increased appropriately during the stirring process.

[0043] (3) After the heat preservation is completed, the material is cooled. When the temperature is 350℃, the gas supply is stopped and the material is cooled to room temperature. The resulting block material is taken out, cut into small pieces, and put into a ball milling device for ball milling. The ball milling process is carried out in an Ar atmosphere with a ball-to-material ratio of 120:1, a ball milling speed of 300 rpm, and a ball milling time of 12 h. After the ball milling is completed, the material is cooled and the powder is taken out to obtain nano-boron composite magnesium-based hydrogen storage material.

[0044] The nano-boron composite magnesium-based hydrogen storage material prepared in this embodiment has similar performance to the nano-boron composite magnesium-based hydrogen storage material in Example 1.

[0045] Example 4

[0046] This embodiment prepares a nano-boron composite magnesium-based hydrogen storage material according to the following method:

[0047] (1) Weigh 36.3g of magnesium powder and 63.7g of magnesium diboride alloy powder in a glove box filled with Ar gas, totaling 100g, of which boron accounts for 30% by mass. Weigh 2g of refining agent.

[0048] (2) First, put the crucible into the melting furnace, heat it to 200℃, preheat it for 30 minutes, then add the weighed magnesium powder and magnesium diboride into the crucible, continue to heat it, and when the temperature in the furnace reaches 350℃, introduce CO2-Ar mixed gas at a flow rate of 6L / h. In the mixed gas, the volume ratio of CO2 to Ar is 8:2. When the temperature reaches 1500℃, add the refining agent, stir for 2 minutes, keep it warm for 5 hours, and continue to ventilate during this period. The gas flow rate can be appropriately increased during the stirring process.

[0049] (3) After the heat preservation is completed, the material is cooled. When the temperature is 350℃, the gas supply is stopped and the material is cooled to room temperature. The resulting block material is taken out, cut into small pieces, and put into a ball milling device for ball milling. The ball milling process is carried out in a vacuum environment with a ball-to-material ratio of 80:1, a ball milling speed of 900 rpm, and a ball milling time of 60 h. After the ball milling is completed, the material is cooled and the powder is taken out to obtain nano-boron composite magnesium-based hydrogen storage material.

[0050] The nano-boron composite magnesium-based hydrogen storage material prepared in this embodiment has similar performance to the nano-boron composite magnesium-based hydrogen storage material in Example 1.

[0051] In summary, in the nano-boron composite magnesium-based hydrogen storage material prepared by this invention, boron atoms can aggregate to form nanoscale structures. These boron-formed nanostructures can not only partially embed themselves in magnesium, causing lattice distortion and enhancing the activity of magnesium, but also serve as an intermediate medium, allowing hydrogen atoms to diffuse into magnesium through the nano-boron, thereby improving the hydrogen absorption and desorption rates of the magnesium-based hydrogen storage material and giving it superior hydrogen storage conditions.

[0052] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made to it in form and detail without departing from the scope defined by the claims of the present invention.

Claims

1. A nano-boron composite magnesium-based hydrogen storage material, characterized in that: The nano-boron composite magnesium-based hydrogen storage material comprises, by mass fraction: boron: 1-30%, with the balance being magnesium. In this material, boron atoms aggregate into nanoscale structures and are composited with magnesium. The nano-boron acts as an intermediate medium in the hydrogen absorption and desorption processes. The preparation method of the nano-boron composite magnesium-based hydrogen storage material includes the following steps: (1) The symmetrically measured magnesium powder and magnesium diboride powder are smelted. During the smelting process, a protective gas is introduced and a refining agent is added to the melt. After the melt is cooled, the smelted body is obtained. (2) The melt obtained in step (1) is broken into fragments, and the fragments are ball-milled in a non-oxidizing atmosphere or vacuum environment to obtain nano-boron composite magnesium-based hydrogen storage material.

2. The preparation method of the nano-boron composite magnesium-based hydrogen storage material according to claim 1, characterized in that: The preparation method includes the following steps: (1) The symmetrically measured magnesium powder and magnesium diboride powder are smelted. During the smelting process, a protective gas is introduced and a refining agent is added to the melt. After the melt is cooled, the smelted body is obtained. (2) The melt obtained in step (1) is broken into fragments, and the fragments are ball-milled in a non-oxidizing atmosphere or vacuum environment to obtain nano-boron composite magnesium-based hydrogen storage material.

3. The preparation method according to claim 2, characterized in that: In step (1), the melting temperature is 700-1500℃ and the holding time is 1-5h.

4. The preparation method according to claim 2, characterized in that: In step (1), the refining agent is a mixture of KCl, MgCl2 and CaF2, and the mass of the refining agent added is 2% of the total mass of magnesium powder and magnesium diboride.

5. The preparation method according to claim 2, characterized in that: In step (1), when the melting temperature rises to 350°C, protective gas is introduced. During the cooling process, when the temperature drops to 350°C, the protective gas is stopped. The flow rate of the protective gas is 3-6 L / h.

6. The preparation method according to claim 2, characterized in that: In step (1), the protective gas is one of argon and carbon dioxide or a mixture of argon and carbon dioxide, wherein the volume ratio of carbon dioxide to argon in the mixture is CO2:Ar=8:

2.

7. The preparation method according to claim 2, characterized in that: In step (2), the ball-to-material ratio is 20-120:1, the ball milling speed is 300-900 rpm, and the ball milling time is 12-60 h.

8. The preparation method according to claim 2 or 7, characterized in that: In step (2), the ball milling process is carried out in a cycle of 30 minutes of ball milling followed by 20 minutes of intermittent milling.

9. The preparation method according to any one of claims 2-7, characterized in that: Before smelting magnesium powder and magnesium diboride powder, preheat the smelting equipment to 150-250℃.

10. The preparation method according to claim 2, characterized in that: In step (2), the non-oxidizing atmosphere is argon.

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