Hydrogen storage material based on magnesium hydride, method for its production and method for producing hydrogen by hydrolysis

Abstract

The application relates to the hydrogen production technical field, and discloses a hydrogen storage material based on magnesium hydride, a preparation method thereof and a hydrolysis hydrogen production method, which comprises a block structure formed by co-molding powdery magnesium, powdery magnesium hydride, powdery alkali metal salt or alkali earth metal salt, wherein the magnesium accounts for 16-22% in weight percentage, the magnesium hydride accounts for 70-76% in weight percentage, and the alkali metal salt or alkali earth metal salt accounts for 8% in weight percentage. The hydrogen storage material prepared by the application has high strength, high hydrogen storage density and fast hydrolysis performance, and is particularly suitable for stable hydrogen supply in a low-temperature environment such as a field.

Description

Technical Field

[0001] This invention relates to the field of hydrogen production technology, and in particular to a hydrogen storage material based on magnesium hydride, its preparation method, and a method for producing hydrogen by water electrolysis. Background Technology

[0002] Magnesium hydride, as a solid hydrogen storage material, can release hydrogen through hydrolysis, offering advantages such as high hydrogen storage density and good safety performance. Existing magnesium hydride hydrogen storage materials are typically in powder form, which is directly added to water for hydrolysis during use. However, powdered magnesium hydride is prone to scattering during storage and transportation, and the reaction rate during hydrolysis is difficult to control. To facilitate use, pressing magnesium hydride into blocks is a common improvement method, but simple magnesium hydride blocks are prone to disintegration during hydrolysis due to insufficient strength, affecting the stability of hydrogen production. Furthermore, the hydrolysis rate of magnesium hydride in pure water is slow, especially at low temperatures, which limits its application in outdoor environments. In existing technologies, binders are added to improve the block strength, but commonly used binders often do not participate in the hydrolysis reaction, reducing the hydrogen storage density of the block. Simultaneously, adding hydrolysis accelerators can accelerate the reaction rate, but how to effectively combine binders and accelerators with magnesium hydride to form a block material with high strength, high hydrogen storage density, and rapid hydrolysis performance remains a technical challenge. Summary of the Invention

[0003] To address the shortcomings of the prior art, this invention provides a magnesium hydride-based hydrogen storage material, its preparation method, and a method for producing hydrogen through water electrolysis.

[0004] The technical solution of the present invention is: a hydrogen storage material based on magnesium hydride, comprising a block structure jointly molded from powdered metallic magnesium, powdered magnesium hydride, and powdered alkali metal salt or alkaline earth metal salt, wherein, by weight percentage, the metallic magnesium accounts for 16% to 22%, the magnesium hydride accounts for 70% to 76%, and the alkali metal salt or alkaline earth metal salt accounts for 8%.

[0005] Furthermore, the magnesium metal is a powder with a particle size of 10-100 micrometers.

[0006] Furthermore, the magnesium hydride is a powder with a particle size of 1-50 micrometers.

[0007] Furthermore, the alkali metal salt or alkaline earth metal salt includes at least one of magnesium chloride, sodium chloride, potassium chloride, and calcium chloride.

[0008] Furthermore, the block structure has a three-dimensional mesh porous structure skeleton formed by molding and cold welding of metallic magnesium, and the magnesium hydride and the alkali metal salt or alkaline earth metal salt are filled in the three-dimensional mesh porous structure skeleton.

[0009] As one embodiment, the present invention also provides a method for preparing the above-mentioned hydrogen storage material, comprising mixing metallic magnesium, magnesium hydride and alkali metal salt or alkaline earth metal salt under argon protection, placing the mixed powder into a mold for molding, obtaining magnesium hydride block and vacuum sealing.

[0010] Furthermore, the mold closing pressure is 350-450MPa, and the mold closing time is 30-60s.

[0011] As one embodiment, the present invention also provides a method for producing hydrogen by hydrolysis using the above-mentioned hydrogen storage material, comprising placing the hydrogen storage material in a chloride salt solution for hydrolysis.

[0012] Furthermore, the hydrolysis temperature is 25-40℃. This invention has the following beneficial effects: By molding powdered metallic magnesium, powdered magnesium hydride, and powdered alkali metal salts or alkaline earth metal salts in a specific ratio, the metallic magnesium is cold-welded under high pressure to form a three-dimensional network porous structure, serving as a skeleton to provide sufficient mechanical strength to the bulk material and prevent disintegration during hydrolysis; magnesium hydride, as the main hydrogen storage component, maintains its weight percentage at 70%~76%, ensuring a high hydrogen storage density in the bulk material; alkali metal salts or alkaline earth metal salts, as hydrolysis promoters, fill the skeleton, accelerating the reaction and increasing the hydrolysis rate at low temperatures. The amount of metallic magnesium as a binder is optimized to 16%~22%, ensuring the integrity of the skeleton structure while minimizing the negative impact on hydrogen storage density. Therefore, this hydrogen storage material possesses high strength, high hydrogen storage density, and rapid hydrolysis performance. Attached Figure Description

[0013] Figure 1 These are the hydrolysis hydrogen release rate curves of the hydrogen storage material in pure water at different temperatures in this invention; Figure 2 These are the hydrolysis hydrogen release rate curves of the hydrogen storage material in sodium chloride solution at different temperatures in this invention; Figure 3 This is a structural diagram of the hydrogen storage material in this invention.

[0014] Reference numerals: 1. Magnesium metal skeleton; 2. Magnesium hydride particles; 3. Magnesium chloride particles. Detailed Implementation

[0015] The technical solutions of the present invention will now be described with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0016] Hereinafter, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0017] Furthermore, in this invention, directional terms such as "upper," "lower," "left," and "right" may be defined relative to the orientation of the components shown in the accompanying drawings. It should be understood that these directional terms can be relative concepts, used for relative description and clarification, and can change accordingly depending on the orientation of the components in the accompanying drawings.

[0018] This invention provides a magnesium hydride-based hydrogen storage material, comprising a bulk structure molded from powdered metallic magnesium, powdered magnesium hydride, and powdered alkali metal salts or alkaline earth metal salts. By weight percentage, powdered metallic magnesium accounts for 16%–22%, powdered magnesium hydride accounts for 70%–76%, and powdered alkali metal salts or alkaline earth metal salts account for 8%. During high-pressure molding, the powdered metallic magnesium undergoes cold welding, forming a continuous three-dimensional network framework structure. This framework provides sufficient mechanical strength to the bulk material, ensuring structural integrity during hydrolysis and preventing disintegration. Powdered magnesium hydride serves as the primary hydrogen storage medium. The hydrolysis reaction equation for hydrogen production is as follows: MgH₂ + 2H₂O = Mg(OH)₂ + 2H₂, meaning that 1 mole of MgH₂ (26g) can produce 2 moles of hydrogen (4g) through hydrolysis. Therefore, the hydrogen storage density of pure magnesium hydride is m(H₂) / m(MgH₂) = 15.38%. Consequently, the hydrogen storage density of the bulk structure obtained in this scheme is 15.38% × (70%~76%) = (10.77%~11.69%). Powdered alkali metal salts or alkaline earth metal salts act as hydrolysis promoters, uniformly dispersed in the framework network. Upon contact with water, they rapidly dissolve, forming a locally high-concentration salt solution environment. This environment significantly reduces the activation energy of the magnesium hydride hydrolysis reaction, thereby accelerating the hydrolysis rate at low temperatures. Through the synergistic effect of these three components, a bulk material hydrolysis hydrogen production technology with high strength, high hydrogen storage density, and rapid hydrolysis performance is formed.

[0019] In this scheme, the powdered alkali metal salt or alkaline earth metal salt includes at least one of magnesium chloride, sodium chloride, potassium chloride, and calcium chloride. These salts have good solubility in water, and their anions (Cl⁻) have a significant catalytic promoting effect on the hydrolysis reaction of magnesium hydride. Among them, anhydrous magnesium chloride is preferred as a hydrolysis promoter, on the one hand, because its catalytic effect is significant, and on the other hand, because it contains magnesium, it will not introduce new impurity cations into the system, which is beneficial to the subsequent treatment of hydrolysis products.

[0020] In this scheme, the average particle size of the powdered magnesium can be selected between 10 micrometers and 100 micrometers. When the particle size of the powdered magnesium is within this range, it has better flowability and deformability during molding, and it is easier for cold welding to occur at the particle contact points, thereby forming a uniform and robust metal skeleton network. In a more preferred scheme, the average particle size of the powdered magnesium is 20 micrometers to 50 micrometers.

[0021] In this scheme, the average particle size of the powdered magnesium hydride can be selected between 1 micrometer and 50 micrometers. A suitable particle size facilitates thorough mixing of the powdered magnesium hydride with powdered metallic magnesium, powdered alkali metal salts, or alkaline earth metal salts, and ensures uniform filling within the metal framework network. In one specific scheme, the average particle size of the powdered magnesium hydride is between 5 micrometers and 30 micrometers.

[0022] like Figure 3 As shown, the bulk structure of this hydrogen storage material has a three-dimensional porous network structure formed by molding and cold welding of metallic magnesium, namely a metallic magnesium skeleton 1, with powdered magnesium hydride and powdered magnesium chloride filling the magnesium skeleton. This structure is naturally formed through a molding process. The metallic magnesium skeleton 1 encapsulates and supports magnesium hydride particles 2 and magnesium chloride particles 3. The pores between the skeleton and the powder particles provide channels for water molecules to enter the bulk and for hydrogen to escape, thus ensuring that the bulk has high strength while still being able to carry out efficient and complete hydrolysis reactions.

[0023] This application also provides a method for preparing the above-mentioned magnesium hydride-based hydrogen storage material, the method comprising: step S1, mixing powdered metallic magnesium, powdered magnesium hydride and powdered magnesium chloride under argon protection: preferably, a three-dimensional mixer or a V-type mixer or other mixing equipment can be used to mix the weighed component powders evenly under argon atmosphere protection.

[0024] Step S2: Under argon protection, the uniformly mixed powder obtained in step S1 is transferred into the mold cavity of a special mold.

[0025] Step S3, Compression Molding: A pressure of 350 MPa to 450 MPa is applied to a mold containing the mixed powder, and the pressure is held for 30 to 60 seconds. During this high pressure and holding time, the powdered magnesium particles undergo plastic deformation and cold welding occurs at their contact points, thereby forming a continuous three-dimensional network skeleton. Simultaneously, powdered magnesium hydride and powdered magnesium chloride are tightly compacted and filled into the skeleton network, ultimately resulting in a magnesium hydride block with a specific shape (such as a cylinder or cuboid) and strength.

[0026] Step S4, Vacuum Sealing: Remove the molded magnesium hydride block from the mold, immediately place it in an aluminum-plastic composite film packaging bag, vacuum seal it, and store it in a cool, dry place. Vacuum sealing can isolate air and moisture, ensuring the chemical stability of the hydrogen storage material during storage.

[0027] This application also provides a method for producing hydrogen through water electrolysis using the aforementioned hydrogen storage material. The method includes: placing the hydrogen storage material block into a chloride salt solution (such as a 0.5%-5% NaCl solution or natural seawater) to carry out a hydrolysis reaction. The temperature of the hydrolysis reaction can be between 25°C and 40°C, which simulates outdoor or room temperature environmental conditions. Figure 1 and Figure 2 As shown, compared with a pure water environment, the hydrogen release rate of magnesium hydride is significantly improved at low temperatures in a solution containing sodium chloride. This method is simple to operate, requires no complex equipment or high-temperature conditions, and can quickly and stably generate hydrogen, making it particularly suitable for mobile or emergency applications.

[0028] Example 1: The components and weight ratios in this example are as follows: 18% metallic magnesium powder, 74% magnesium hydride powder, and 8% magnesium chloride powder. Under the protection of argon at room temperature, the above powders are mixed and placed in a mold. A pressure of 350 MPa to 450 MPa is applied and the pressure is maintained for 30 to 60 seconds to obtain magnesium hydride blocks, which are then vacuum sealed. The calculated hydrogen storage density is 11.38%.

[0029] Example 2: Unlike Example 1, the composition and weight ratio of this example are as follows: 16% magnesium powder, 76% magnesium hydride powder, and 8% magnesium chloride powder. The calculated hydrogen storage density is 11.69%.

[0030] Example 3: Unlike Example 1, the composition and weight ratio of this example are as follows: 22% magnesium metal powder, 70% magnesium hydride powder, and 8% magnesium chloride powder. The calculated hydrogen storage density is 10.77%.

[0031] Comparative Example 1: Unlike Example 1, the composition and weight ratio of this comparative example are as follows: 30% magnesium metal powder, 62% magnesium hydride powder, and 8% magnesium chloride powder. The calculated hydrogen storage density is 9.54%.

[0032] Comparative Example 2: Unlike Example 1, the composition and weight distribution of this comparative example are as follows: 14% magnesium powder, 78% magnesium hydride powder, and 8% magnesium chloride powder. The calculated hydrogen storage density is 12%.

[0033] Hydrolysis comparison experiments were conducted on the hydrogen storage materials of the above examples and Comparative Example 1. For example, 0.1 g (accurately weighed) of block sample was put into a closed reactor containing 50 mL of 3 wt.% NaCl solution at 30 °C. The cumulative hydrogen production within 20 minutes was measured by the water displacement gas collection method, and the hydrogen production rate and final hydrolysis rate were calculated, resulting in Table 1.

[0034] Table 1. Hydrolysis performance test results of each embodiment and Comparative Example 1 The data above shows that when the content of powdered metallic magnesium is 16%~22%, the content of powdered magnesium hydride is 70%~76%, and 8% of powdered anhydrous magnesium chloride is contained (Examples 1-3), the resulting bulk material maintains a high hydrogen storage density (>10.8%) while also possessing good structural strength and excellent low-temperature hydrolysis performance (high hydrolysis rate and high reaction rate). In Comparative Example 1, the excessively high content of metallic magnesium severely crowded out the magnesium hydride content, resulting in a significant decrease in hydrogen storage density and a reduced hydrogen production rate during hydrolysis. In Comparative Example 2, the excessively low content of metallic magnesium prevented the formation of a robust framework, resulting in poor bulk strength and easy disintegration during hydrolysis, thus failing to meet the application requirements.

[0035] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A hydrogen storage material based on magnesium hydride, characterized in that, It includes a block structure formed by molding powdered metallic magnesium, powdered magnesium hydride, powdered alkali metal salt or alkaline earth metal salt together, wherein, by weight percentage, the metallic magnesium accounts for 16% to 22%, the magnesium hydride accounts for 70% to 76%, and the alkali metal salt or alkaline earth metal salt accounts for 8%.

2. The hydrogen storage material based on magnesium hydride according to claim 1, characterized in that, The magnesium metal is a powder with a particle size of 10-100 micrometers.

3. The hydrogen storage material based on magnesium hydride according to claim 1, characterized in that, The magnesium hydride is a powder with a particle size of 1-50 micrometers.

4. A hydrogen storage material based on magnesium hydride according to claim 1, characterized in that, The alkali metal salt or alkaline earth metal salt includes at least one of magnesium chloride, sodium chloride, potassium chloride, and calcium chloride.

5. A hydrogen storage material based on magnesium hydride according to any one of claims 1-4, characterized in that, The block structure has a three-dimensional mesh porous structure skeleton formed by molding and cold welding of metallic magnesium, and the magnesium hydride and the alkali metal salt or alkaline earth metal salt are filled in the three-dimensional mesh porous structure skeleton.

6. A method for preparing a hydrogen storage material according to any one of claims 1-5, characterized in that, include: Magnesium metal, magnesium hydride, and alkali metal or alkaline earth metal salts are mixed under argon protection. The mixed powder is then placed into a mold and molded to obtain magnesium hydride blocks, which are then vacuum sealed.

7. The method for preparing the hydrogen storage material according to claim 6, characterized in that, The mold closing pressure is 350-450MPa, and the closing time is 30-60s.

8. A method for producing hydrogen by water electrolysis using the hydrogen storage material according to any one of claims 1-5, comprising: The hydrogen storage material is hydrolyzed in a chloride salt solution.

9. The method for producing hydrogen by hydrolysis according to claim 8, characterized in that, The hydrolysis temperature is 25-40℃.

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