A method for preparing a porous hydrogen storage alloy

Abstract

The application discloses a preparation method of a porous hydrogen storage alloy. The porous hydrogen storage alloy is prepared by mixing a completely hydrogenated hydrogen storage metal / alloy, nano transition metal powder and carbonate powder, pressing the mixture into a sheet and then sintering. In the sintering process, gas is generated by the reaction of the hydride and the carbonate, and the gas escapes to form a porous structure in the alloy block. Through a staged heating process, the formation process and the morphology structure of the porous hydrogen storage alloy are controlled. The prepared hydrogen storage alloy block has a hydrogen storage performance equivalent to that of pure alloy powder, and can maintain the block shape and has a low volume expansion rate in the repeated hydrogen absorption and release process. The application is suitable for preparing the porous hydrogen storage alloy.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen storage material preparation, specifically a porous hydrogen storage alloy material and its preparation method. Background Technology

[0002] Since the beginning of the 21st century, the excessive exploitation and utilization of traditional fossil fuels has caused immense damage to the Earth's ecological environment and triggered a series of environmental problems, such as the greenhouse effect and smog. Therefore, more and more countries are vigorously developing clean and pollution-free new energy sources, and the demand for new energy sources to gradually replace fossil fuels is becoming increasingly strong. Among many new energy sources, hydrogen energy is pollution-free and has a high energy density (142 MJ·kg⁻¹). -1 Its characteristics, such as [specific features], have received widespread attention. However, among the many aspects of hydrogen energy application, storage and transportation issues have constrained its development.

[0003] The development of high-performance solid-state hydrogen storage materials is an effective way to achieve efficient and safe hydrogen transportation. Furthermore, the development of hydrogen storage materials requires a close correlation between high performance and application characteristics. Localized compaction of solid-state hydrogen storage materials in devices can lead to localized stress concentration on the hydrogen storage tank wall when the hydrogen alloy absorbs hydrogen and expands, causing damage to the hydrogen storage tank and seriously affecting the safety of solid-state hydrogen storage devices. To address the stress concentration problem in solid-state hydrogen storage devices, Chinese invention patent (CN115961160A) uses a single-tube hydrogen storage tank, while other invention patents (CN114440123A and CN115650157A) use a briquetting method to alleviate stress concentration and other problems, providing valuable ideas and explorations for promoting the application of hydrogen storage materials in solid-state hydrogen storage devices. To further reduce the macroscopic volume expansion rate of hydrogen storage bed components, this invention studies porous hydrogen storage bulk materials and their preparation methods. By forming an internal pore structure, the hydrogen storage material can partially expand into the internal voids, thereby reducing the external macroscopic volume expansion, reducing the stress concentration between bed components and between the hydrogen storage material bed and the device wall, protecting the hydrogen storage device, and improving the safety of device operation. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for preparing a porous hydrogen storage alloy. The alloy is prepared by mixing and pressing a fully hydrogenated hydrogen storage metal / alloy, nano-transition metal powder, and carbonate powder into a sheet, followed by sintering. During sintering, gas is generated through the reaction of hydrides and carbonates. This gas escapes and forms a porous structure within the alloy block. By controlling the formation process and morphology of the porous hydrogen storage alloy through a phased heating process, the prepared hydrogen storage alloy block exhibits hydrogen storage performance comparable to that of pure alloy powder. Furthermore, it maintains its block shape during repeated hydrogen absorption and desorption, and has a low volume expansion rate.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for preparing a porous hydrogen storage alloy, comprising the following steps in sequence: S1. Mix the fully hydrogenated hydrogen storage metal / alloy, nano-transition metal powder and carbonate powder evenly, and press them into sheets with a diameter of 5-15 mm and a thickness of 1-15 mm under an inert atmosphere. During the pressing process, maintain the pressure at 10 MPa for 1 min. S2. Place the pressed sheet in a high-temperature tube furnace and sinter it under an inert atmosphere. S3. After sintering, the material is allowed to cool naturally to room temperature to obtain a porous hydrogen storage alloy material.

[0006] As a limitation of the present invention, in step S1, the fully hydrogenated hydrogen storage metal / alloy includes MgH2, Ti-Mn-Cr hydride, and RE-Mg hydride; the nano-transition metal powder includes nano-nickel powder, nano-cobalt powder, and nano-iron powder; and the carbonate includes calcium carbonate, sodium carbonate, barium carbonate, ammonium carbonate, and ammonium bicarbonate.

[0007] In terms of raw material selection, this invention uses metal / alloy hydrides as starting materials because they release highly reducing atomic hydrogen upon heating, readily reacting with carbonates to generate gaseous products such as methane. This invention also employs nano-transition metal powder as a catalyst for the carbonate reaction. During and after hydrogen generation, the nano-transition metal powder in contact with carbonates can act as reactive centers, or as active centers for the reduction of carbon dioxide from carbonate pyrolysis, catalyzing the catalytic reaction between carbonates and carbon dioxide. This invention uses carbonates as pore-forming agents. The gas generated by the carbonate reaction creates small pores on the surface and inside of the compressed mixture tablet. Simultaneously, the repeated adsorption / desorption of gas on the surface of the nano-transition metal powder (as a catalyst) also activates the nano-transition metal, further facilitating the subsequent formation of the hydrogen storage alloy.

[0008] As a second limitation of the present invention, the weight ratio of unhydrogenated hydrogen storage metal / alloy, nano-transition metal powder and carbonate powder is (30-74):(16-60):(2-15).

[0009] The ratio of the above three factors affects the chemical composition, phase structure, pore size, porosity, and uniformity of pore distribution of hydrogen storage alloys.

[0010] As a third limitation of the present invention, in step S2, the sintering process is performed in three stages: The first stage of the process: raise the temperature from room temperature to 200-300℃ and keep it at that temperature for 3-5 hours; The second stage: raise the temperature to 400-500℃ and keep it at that temperature for 3-5 hours; The third stage: raise the temperature to 600-1000℃ and keep it at that temperature for 3-5 hours.

[0011] The staged sintering process of this invention is crucial for the final morphology and composition of the porous hydrogen storage alloy. Firstly, sintering at a low temperature of 200–300°C generates a small amount of gas. This gas includes hydrogen released from the metal / alloy hydride under the catalysis of nano-transition metal powder and gas produced by the decomposition of carbonates (when ammonium carbonate, ammonium bicarbonate, etc. are used). At this stage, the temperature is low, and the catalytic reduction process has not yet occurred. Next, the temperature is raised to 400–500°C and held. During this holding process, the carbonates (or carbon dioxide if ammonium bicarbonate or ammonium carbonate) and the hydrogen gas with a certain pressure generated at low temperature undergo a reduction reaction under the catalysis of the nano-transition metal. This reaction further generates gas, further improving the original porous structure. At this point, the reducing gas... Under the influence of [the specific action / condition], the surface activity of the nano-metal powder is also enhanced, and it is mostly distributed on the pore wall surface, with uniform dispersion. When the temperature is further increased to 600℃, the reduction reaction is basically completed, and the active nano-transition metal powder is also dispersed on the pore wall surface. Continuing to hold at 600-1000℃ allows the dehydrogenated hydrogen storage metal / alloy metal to alloy with the nano-transition metal powder. The oxides and other residues remaining after the reduction of carbonates are not easily thermally diffused during heating, and can help maintain the pore structure during the thermal diffusion of the nano-transition metal powder, further stabilizing the porous structure and forming a stable "grid" structure inside the alloy. This fixes the hydrogen storage alloy powder, preventing pulverization and "dust generation" during repeated hydrogen absorption and desorption, and ensuring stable mass and heat transfer during hydrogen absorption and desorption. At the same time, holding at 600-1000℃ can fully stabilize the alloy structure, increase the eutectic phase, further eliminate dislocation and grain boundary movement, improve the mechanical strength of the "grid" inside the alloy, and avoid alloy pulverization after hydrogen absorption and desorption.

[0012] As a fourth limitation of the present invention, the porous hydrogen storage alloy is a composite material composed of one or more of the following: A2B type magnesium-based hydrogen storage alloy and AB3 type superlattice hydrogen storage alloy.

[0013] As a fifth limitation of the present invention, the porosity of the porous hydrogen storage alloy is 10 to 40%.

[0014] In this invention, the high porosity structure inhibits the volume expansion and pulverization of the hydrogen storage alloy. Specifically, during actual hydrogen absorption and desorption, the hydrogen storage alloy expands / contracts, and the pores act as a buffer, preventing excessive stress concentration that could exceed the alloy's elastic expansion limit and cause damage to the alloy's grain structure, thus avoiding pulverization. The porous structure provides channels for hydrogen diffusion during absorption and desorption. Appropriate pore size increases the contact area between hydrogen and the hydrogen storage alloy, improving the absorption and desorption rate. Simultaneously, the appropriately sized pores stabilize the bulk shape of the alloy during the hydrogen absorption and desorption cycle, forming a buffer space for volume expansion and preventing excessive outward expansion that could lead to excessive local stress concentration in the hydrogen storage container. If the pore size is too small, it cannot effectively resist volume expansion, and the alloy block may still pulverize, causing alloy powder to fly during hydrogen absorption and desorption, affecting mass and heat transfer. If the pore size is too large, the hydrogen storage alloy will not be tightly connected, also resulting in alloy block pulverization and wasting significant internal space.

[0015] As a further limitation of the present invention, the heating rate of the first process is 5°C / min, the heating rate of the second process is 5°C / min, and the heating rate of the third process is 1°C / min.

[0016] The heating rate affects the gas production rate, as well as the size of the internal pores and the pore structure of the hydrogen storage alloy. Too rapid a heating rate results in a large gas production volume in a short time, with a large amount of gas escaping from the hydrogen storage alloy bulk material, creating large pores and weakening the alloy joints, making them prone to breakage. Conversely, too slow a heating rate leads to a slow gas production rate, with later-produced gas escaping through the pores formed by earlier-produced gas, which is detrimental to pore expansion. The above-mentioned technical solution of the present invention is a whole in which each step is closely related and mutually influential, and together they determine the morphological characteristics and performance of the product.

[0017] The above technical solution has the following advantages or beneficial effects: 1. The preparation method of this invention is simple, the process is easy to control, the cycle is short, and it is easy to industrialize and promote.

[0018] 2. This invention creatively utilizes the decomposition of hydrogen storage metal / alloy hydrides upon heating to release hydrogen gas. Taking advantage of the strong reducing properties of hydrogen gas, the carbonates in the precursor react, and the generated gas escapes from the surface and interior of the bulk material, constructing an in-situ network of channels during the formation of the hydrogen storage alloy.

[0019] 3. The porous hydrogen storage alloy prepared by this invention has a porosity of 10-40%. After being filled into a solid hydrogen storage device, it can resist the pulverization phenomenon caused by volume expansion, thereby avoiding the damage to the hydrogen storage device caused by local stress concentration on the hydrogen storage device wall when the hydrogen storage alloy absorbs hydrogen and expands, thus ensuring the safety of the solid hydrogen storage device.

[0020] This invention is applicable to the preparation of porous hydrogen storage alloys. Attached Figure Description

[0021] Figure 1 Scanning electron microscope images of the porous hydrogen storage alloy prepared for the present invention, wherein: (a) - Example 1, (b) - Example 2, (c) - Example 3, (d) - Example 4, (e) - Example 5, (f) - Example 6, (g) - Comparative Example 1, (h) - Comparative Example 2, (i) - Comparative Example 3; Figure 2 Hydrogen absorption curves of the porous hydrogen storage alloy prepared in this invention, wherein: (a) - Example 1, (b) - Example 2, (c) - Example 3, (d) - Example 4, (e) - Example 5, (f) - Example 6, (g) - Comparative Example 1, (h) - Comparative Example 2, (i) - Comparative Example 3. Detailed Implementation

[0022] The following embodiments are merely some, not all, of the embodiments of the present invention. Therefore, the detailed descriptions of the embodiments provided below are not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0023] In this invention, unless otherwise specified, all equipment and raw materials are commercially available or commonly used in the industry. The methods described in the following embodiments are conventional methods in the art, unless otherwise specified.

[0024] Example 1

[0025] Weigh 0.82g of metallic Mg powder and place it in a sample tube for complete hydrogenation. The fully hydrogenated Mg powder (MgH2) is then mixed and ground uniformly with 0.98g of nano-nickel powder and 0.20g of ammonium bicarbonate granules (a pore-forming agent) in an argon atmosphere and pressed into sheets under a pressure of 10MPa for 1 min. The pressed mixture is then placed in a tube furnace for sintering. Argon gas is introduced to isolate the air, and the temperature is increased from room temperature to 200℃ at a rate of 5℃ / min and held for 3 h. The temperature is then increased to 400℃ at a rate of 5℃ / min and held for 3 h. Finally, the temperature is increased to 600℃ at a rate of 1℃ / min and held for 5 h. The furnace is then cooled to room temperature to obtain a porous Mg2Ni hydrogen storage alloy material.

[0026] The prepared material was tested using scanning electron microscopy, see details below. Figure 2 As shown, the microstructure of the porous Mg2Ni hydrogen storage alloy material exhibits small pores with diameters ranging from 20 to 50 μm, present both on the alloy surface and internally. Hydrogen absorption and desorption tests were performed on the obtained porous Mg2Ni hydrogen storage alloy. Figure 1 As shown, the porous Mg2Ni hydrogen storage alloy achieved a hydrogen absorption capacity of 3.1 wt% at 200℃, reaching its maximum capacity within 100 s. After 10 cycles, the hydrogen absorption capacity remained at 3.1 wt%, showing no decrease compared to the maximum capacity. After 10 hydrogen absorption / desorption cycles, the alloy remained in bulk form with a volume expansion rate of 10%.

[0027] Example 2

[0028] Weigh 0.77g of metallic Mg powder and place it in a sample tube for complete hydrogenation. The fully hydrogenated Mg powder (MgH2) is then mixed and ground uniformly with 0.93g of nano-nickel powder and 0.30g of ammonium carbonate granules (a pore-forming agent) in an argon atmosphere and pressed into sheets under a pressure of 10MPa for 1 min. The pressed mixture is then placed in a tube furnace for sintering. Argon gas is introduced to isolate the air, and the temperature is increased from room temperature to 200℃ at a rate of 5℃ / min and held for 5 h. The temperature is then increased to 400℃ at a rate of 5℃ / min and held for 5 h. Finally, the temperature is increased to 600℃ at a rate of 1℃ / min and held for 3 h. The furnace is then cooled to room temperature to obtain a porous Mg2Ni hydrogen storage alloy material.

[0029] The prepared material was tested using scanning electron microscopy, see details below. Figure 2 As shown, the microstructure of the porous Mg2Ni hydrogen storage alloy material exhibits small pores with diameters ranging from 30 to 70 μm, present both on the alloy surface and internally. Hydrogen absorption and desorption tests were performed on the obtained porous Mg2Ni hydrogen storage alloy. Figure 1As shown, the porous Mg2Ni hydrogen storage alloy achieved a hydrogen absorption capacity of 3.1 wt% at 200℃, reaching its maximum capacity within 400 s. After 10 cycles, the hydrogen absorption capacity remained at 3.1 wt%, showing no decrease compared to the maximum capacity. After 10 hydrogen absorption / desorption cycles, the alloy remained in bulk form with a volume expansion rate of 11%.

[0030] Example 3

[0031] Weigh 0.89g of metallic Mg powder and place it in a sample tube for complete hydrogenation. The fully hydrogenated Mg powder (MgH2) is mixed and ground uniformly with 1.07g of nano-nickel powder and 0.04g of barium carbonate pore-forming agent in an argon atmosphere and pressed into sheets under a pressure of 10MPa for 1 min. The pressed mixture is then placed in a tube furnace for sintering. Argon gas is introduced to isolate the air, and the temperature is increased from room temperature to 300℃ at a rate of 5℃ / min and held for 3 h. The temperature is then increased to 400℃ at a rate of 5℃ / min and held for 4 h. Next, the temperature is increased to 600℃ at a rate of 5℃ / min, and then increased to 630℃ at a rate of 1℃ / min and held for 4 h. The furnace is then cooled to room temperature to obtain a porous Mg2Ni hydrogen storage alloy material.

[0032] The prepared material was tested using scanning electron microscopy, see details below. Figure 2 As shown, the microstructure of the porous Mg2Ni hydrogen storage alloy material exhibits small pores with diameters ranging from 15 to 40 μm, present both on the alloy surface and internally. Hydrogen absorption and desorption tests were performed on the obtained porous Mg2Ni hydrogen storage alloy. Figure 1 As shown, the porous Mg2Ni hydrogen storage alloy achieved a hydrogen absorption capacity of 3.1 wt% at 200℃, reaching its maximum capacity within 400 s. After 10 cycles, the hydrogen absorption capacity remained at 3.1 wt%, showing no decrease compared to the maximum capacity. After 10 hydrogen absorption / desorption cycles, the alloy remained in bulk form, with a volume expansion rate of 14%.

[0033] Example 4

[0034] Weigh 0.60g of metallic La2Mg alloy powder and place it in a sample tube for complete hydrogenation. Mix the fully hydrogenated alloy powder with 1.20g of nano-nickel powder and 0.20g of pore-forming barium carbonate particles in an argon atmosphere, grind evenly, and press into sheets under a pressure of 10MPa for 1min. Place the pressed mixture in a tube furnace for sintering. Introduce argon to isolate it from air, and heat from room temperature to 250℃ at a rate of 5℃ / min, holding for 4h. Then heat to 450℃ at a rate of 5℃ / min, holding for 4h. Finally, heat to 885℃ at a rate of 1℃ / min, holding for 5h, and cool to room temperature in the furnace to obtain a porous La2MgNi9 hydrogen storage alloy material.

[0035] The prepared material was tested using scanning electron microscopy, see details below. Figure 2 As shown, the microstructure of the porous La2MgNi9 hydrogen storage alloy material exhibits small pores with diameters ranging from 15 to 30 μm, present both on the alloy surface and internally. Hydrogen absorption and desorption tests were performed on the obtained porous La2MgNi9 hydrogen storage alloy. Figure 1 As shown, the porous La2MgNi9 hydrogen storage alloy achieved a hydrogen absorption capacity of 1.4 wt% at 30 °C, reaching its maximum capacity within 100 s. After 10 cycles, the hydrogen absorption capacity remained at 1.4 wt%, showing no decrease compared to the maximum capacity. After 10 hydrogen absorption / desorption cycles, the alloy remained in bulk form with a volume expansion rate of 18%.

[0036] Example 5

[0037] Weigh 0.63g of metallic Sm2Mg alloy powder and place it in a sample tube for complete hydrogenation. The fully hydrogenated alloy powder is then mixed and ground uniformly with 1.17g of nano-cobalt powder and 0.20g of pore-forming ammonium carbonate particles in an argon atmosphere and pressed into sheets under a pressure of 10MPa for 1 min. The pressed mixture is then placed in a tube furnace for sintering. Argon gas is introduced to isolate the air, and the temperature is increased from room temperature to 300℃ at a rate of 5℃ / min and held for 3 h. The temperature is then increased to 500℃ at a rate of 5℃ / min and held for 4 h. Finally, the temperature is increased to 925℃ at a rate of 1℃ / min and held for 5 h. The furnace is then cooled to room temperature to obtain a porous Sm2MgNi9 hydrogen storage alloy material.

[0038] The prepared material was tested using scanning electron microscopy, see details below. Figure 2 As shown, the microstructure of the porous Sm2MgNi9 hydrogen storage alloy material exhibits small pores with diameters ranging from 20 to 50 μm, present both on the alloy surface and internally. Hydrogen absorption and desorption tests were performed on the obtained porous Sm2MgNi9 hydrogen storage alloy. Figure 1 As shown, the porous Sm2MgNi9 hydrogen storage alloy achieved a hydrogen absorption capacity of 1.5 wt% at 30℃, reaching its maximum capacity within 100 s. After 10 cycles, the hydrogen absorption capacity remained at 1.5 wt%, showing no decrease compared to the maximum capacity. After 10 hydrogen absorption / desorption cycles, the alloy remained in bulk form, with a volume expansion rate of 13%.

[0039] Example 6

[0040] Weigh 1.48g of metallic Ti 1.0 Mn 0.9 Cr 0.6Alloy powder was placed in a sample tube and fully hydrogenated. The fully hydrogenated alloy powder was then mixed and ground uniformly with 0.32 g of nano-iron powder and 0.20 g of pore-forming ammonium bicarbonate particles in an argon atmosphere and pressed into sheets under a pressure of 10 MPa for 1 min. The pressed mixture was then placed in a tube furnace for sintering. Argon gas was introduced to isolate air, and the temperature was increased from room temperature to 300 °C at a rate of 5 °C / min and held for 4 h. The temperature was then increased to 400 °C at a rate of 5 °C / min and held for 4 h. Finally, the temperature was increased to 1000 °C at a rate of 1 °C / min and held for 5 h. The furnace was then cooled to room temperature to obtain porous Ti. 1.0 Mn 0.9 Cr 0.6 Fe 0.5 Hydrogen storage alloy materials.

[0041] The prepared material was tested using scanning electron microscopy, see details below. Figure 2 As shown, porous Ti 1.0 Mn 0.9 Cr 0.6 Fe 0.5 The microstructure of the hydrogen storage alloy material is characterized by small pores with diameters ranging from 15 to 50 μm, present both on the alloy surface and internally. The obtained porous Ti... 1.0 Mn 0.9 Cr 0.6 Fe 0.5 Hydrogen storage alloys were subjected to hydrogen absorption and desorption tests, see [link / reference]. Figure 1 As shown, porous Ti is obtained 1.0 Mn 0.9 Cr 0.6 Fe 0.5 The hydrogen storage alloy achieves a hydrogen absorption capacity of 1.7 wt% at 45°C, reaching its maximum absorption capacity within 100 seconds. After 10 cycles, the hydrogen absorption capacity remains at 1.7 wt%, showing no decrease compared to the maximum capacity. After 10 hydrogen absorption / desorption cycles, the alloy remains in bulk form with a volume expansion rate of 17%.

[0042] Comparative Example 1 2.0 g of Mg2Ni hydrogen storage alloy powder was weighed and pressed into a sheet under a pressure of 10 MPa for 1 min. The sheet was then placed in a sample tube for complete hydrogenation. The hydrogen absorption capacity of the Mg2Ni hydrogen storage alloy at 200 °C was approximately 2.7 wt%, and it took about 800 s to reach its maximum hydrogen absorption capacity. After 10 cycles, the hydrogen absorption capacity was approximately 2.6 wt%, with no significant decrease compared to the maximum capacity. After 10 hydrogen absorption and desorption cycles, the alloy essentially became powder.

[0043] Comparative Example 2 Weigh 0.64g of metallic Mg powder and place it in a sample tube for complete hydrogenation. The fully hydrogenated Mg powder (MgH2) is then mixed and ground uniformly with 0.76g of nano-nickel powder and 0.60g of ammonium bicarbonate granules (a pore-forming agent) in an argon atmosphere and pressed into sheets under a pressure of 10MPa for 1 min. The pressed mixture is then placed in a tube furnace for sintering. Argon gas is introduced to isolate the air, and the temperature is increased from room temperature to 200℃ at a rate of 5℃ / min and held for 3 h. The temperature is then increased to 400℃ at a rate of 5℃ / min and held for 3 h. Finally, the temperature is increased to 600℃ at a rate of 5℃ / min and held for 5 h. The furnace is then cooled to room temperature to obtain a porous Mg2Ni hydrogen storage alloy material.

[0044] The porous Mg2Ni hydrogen storage alloy exhibits a microstructure characterized by small pores with diameters ranging from 80 to 120 μm, present both on the alloy surface and internally. Hydrogen absorption and desorption tests were conducted on the obtained porous Mg2Ni hydrogen storage alloy, revealing a hydrogen absorption capacity of 3.1 wt% at 200 °C, reaching its maximum capacity within 400 s. After 10 cycles, the hydrogen absorption capacity remained at 3.1 wt%, showing no decrease compared to the maximum capacity. Following 10 hydrogen absorption and desorption cycles, some of the bulk material fractured, forming hydrogen storage alloy particles.

[0045] Comparative Example 3 Weigh 0.82g of metallic Mg powder and place it in a sample tube for complete hydrogenation. The fully hydrogenated Mg powder (MgH2) is then mixed and ground uniformly with 0.98g of nano-nickel powder and 0.20g of ammonium bicarbonate granules (a pore-forming agent) under an argon atmosphere. The mixture is then pressed into sheets at 10MPa for 1 min. The pressed mixture is placed in a tube furnace for sintering. Argon gas is introduced to isolate it from air, and the temperature is increased from room temperature to 600℃ at a rate of 5℃ / min, then increased to 800℃ at a rate of 1℃ / min, and held for 5 h to obtain a porous Mg2Ni hydrogen storage alloy material.

[0046] The porous Mg2Ni hydrogen storage alloy exhibits a microstructure characterized by small pores with diameters ranging from 2 to 10 μm, present both on the alloy surface and internally. Hydrogen absorption and desorption tests were conducted on the obtained porous Mg2Ni hydrogen storage alloy, revealing a hydrogen absorption capacity of 3.1 wt% at 200 °C, reaching its maximum capacity within 400 s. After 10 cycles, the hydrogen absorption capacity remained at 3.1 wt%, showing no decrease compared to the maximum capacity. After 10 hydrogen absorption and desorption cycles, most of the bulk material had pulverized, with only a small number of particles remaining in the central region.

[0047] Comparative Example 4 Group A: The preparation process is similar to that in Example 1, except that no pore-forming agent is added to the precursor.

[0048] Group B: The preparation process is similar to that in Example 1, except that the sintering process is a single-stage heating process, where the temperature is increased from room temperature to 600°C at a rate of 5°C / min and held for 60min.

[0049] Group C: The preparation process is similar to that in Example 1, except that the thickness of the tablet is 20 mm.

[0050] The properties of the alloys prepared in groups A to C above were measured, and the specific results are as follows: The hydrogen storage capacity of the alloys prepared in groups A to C was not significantly different, all ranging from 3.0 to 3.1 wt%. However, the hydrogen absorption rate was significantly different, with groups A, C, and C reaching their maximum hydrogen absorption capacity in 700 s, 400 s, and 150 s, respectively. After 10 hydrogen absorption and desorption cycles, group A had become powder, group B had become larger particles, while group C showed obvious powder shedding at the edges of the bulk material.

[0051] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a porous hydrogen storage alloy, characterized in that, Follow these steps in sequence: S1. Mix the fully hydrogenated hydrogen storage metal or alloy, nano-transition metal powder and carbonate powder evenly, and press them into sheets with a diameter of 5-15 mm and a thickness of 1-15 mm under an inert atmosphere. During the pressing process, maintain the pressure at 10 MPa for 1 min. The weight ratio of unhydrogenated hydrogen storage metal or alloy, nano-transition metal powder to carbonate powder is (30-74):(16-60):(2-15). S2. Place the pressed sheet in a high-temperature tube furnace and sinter it under an inert atmosphere. S3. After sintering, the material is allowed to cool naturally to room temperature to obtain a porous hydrogen storage alloy material.

2. The method for preparing a porous hydrogen storage alloy according to claim 1, characterized in that, In step S1, the fully hydrogenated hydrogen storage metal or alloy includes any one of MgH2, Ti-Mn-Cr hydride, and RE-Mg hydride; the nano-transition metal powder includes any one of nano-nickel powder, nano-cobalt powder, and nano-iron powder; and the carbonate includes any one of calcium carbonate, sodium carbonate, barium carbonate, ammonium carbonate, and ammonium bicarbonate.

3. The method for preparing a porous hydrogen storage alloy according to claim 1, characterized in that, In step S2, the sintering process is divided into three stages: The first stage of the process: raise the temperature from room temperature to 200-300℃ and keep it at that temperature for 3-5 hours; The second stage: raise the temperature to 400-500℃ and keep it at that temperature for 3-5 hours; The third stage: raise the temperature to 600-1000℃ and keep it at that temperature for 3-5 hours.

4. The method for preparing a porous hydrogen storage alloy according to claim 3, characterized in that, The heating rate for the first stage is 5℃ / min, the heating rate for the second stage is 5℃ / min, and the heating rate for the third stage is 1℃ / min.

5. The method for preparing a porous hydrogen storage alloy according to claim 1, characterized in that, The porous hydrogen storage alloy has a chemical composition of one of the following: A2B type magnesium-based hydrogen storage alloy, AB3 type superlattice hydrogen storage alloy, and AB2 type titanium-based hydrogen storage alloy.

6. The method for preparing a porous hydrogen storage alloy according to claim 1, characterized in that, The porosity of the porous hydrogen storage alloy is 10–40%.

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