Magnesium-based hydrogen storage material with resistance to nitrogen poisoning and preparation method thereof

Abstract

This invention discloses a magnesium-based hydrogen storage material resistant to nitrogen poisoning, with the atomic ratio satisfying the following: Nd 2.5-4 at.%, Ni 8-12 at.%, and the remainder Mg. The phase composition includes Mg, Mg₂Ni, and NdH₂ phases, wherein Mg and Mg₂Ni phases are hydrogen storage phases, and NdH₂ phase is a catalytic phase. Furthermore, the Mg phase accounts for more than 50% by mass, the NdH₂ phase accounts for 15%-20% by mass, and the remainder is Mg₂Ni phase. The NdH₂ phase particle size is 20-40 nm. The NdH₂ phase is composed of Nd₄Mg from the Mg-Ni-Nd alloy. 80 The Ni8 phase is formed by in-situ decomposition. A method for preparing a magnesium-based hydrogen storage material resistant to nitrogen poisoning is described. Under a pure hydrogen atmosphere, the magnesium-based hydrogen storage material undergoes repeated hydrogen absorption and desorption cycles of 10-15 times to achieve nitrogen poisoning resistance. The method achieves a hydrogen absorption capacity retention rate greater than 85% at low nitrogen concentrations (initial absorption capacity of 5.00-5.65 wt.%) and 50 cycles; and at high nitrogen concentrations (initial absorption capacity of 5.00-5.65 wt.%) and 30 cycles, the hydrogen absorption capacity retention rate is also greater than 85%.

Description

Technical Field

[0001] This invention relates to the field of hydrogen storage materials technology, specifically to a magnesium-based hydrogen storage material resistant to nitrogen poisoning and its preparation method. Background Technology

[0002] Metallic magnesium (Mg) is a suitable hydrogen storage material, boasting a high hydrogen storage density of 7.6 wt.%, as well as abundant resources and low cost. Currently, the hydrogen purity used in magnesium-based hydrogen storage materials is mostly 99.999%, and purifying the hydrogen source incurs additional costs. In practical applications, the hydrogen source for magnesium-based hydrogen storage materials is industrial hydrogen, specifically byproducts from industries such as coking, ammonia synthesis, chlor-alkali production, and propane dehydrogenation to propylene. In these applications, the content of the impurity gas N2 ranges from 0.5% to 10%, and N2 acts as a poisoning atmosphere for magnesium-based hydrogen storage materials. This means that magnesium-based hydrogen storage materials may lose their hydrogen storage capacity or experience a significant decline in hydrogen storage capacity and kinetics after only a few cycles in a hydrogen atmosphere containing N2 impurities. For example, in existing literature 1 (《The storage of industrially pure hydrogen in magnesium》International Journal of Hydrogen Energy, 1993, 18(4):297-300.), pure MgH2 under a 0.497% N2+H2 atmosphere, at a hydrogen absorption temperature of 395℃ and a hydrogen absorption pressure of 3MPa, experienced a capacity decay of more than 30% after 5 cycles. This literature indicates that Mg-based hydrogen storage materials are extremely susceptible to the influence of impurity gas N2. To solve the technical problem of the rapid performance degradation of magnesium-based hydrogen storage materials due to the poisoning of impurity gas N2, existing anti-nitrogen poisoning strategies mainly fall into two categories: 1. Surface modification; 2. Compositeization.

[0003] The basic principle of improving nitrogen poisoning resistance through surface modification is to provide a filter-like effect by changing the surface composition and structure of the material—allowing H2 to pass through but preventing the passage of impurity gas N2, thus achieving selective permeation of gas molecules. At the same time, the catalytic activity of the material surface is improved to promote the dissociation and diffusion of H2, thereby improving the material's nitrogen poisoning resistance. For example, in existing literature 2 ("Effects of impurity gases on hydrogen storage properties of fluoride-containing AZ61 magnesium alloys", International Journal of Hydrogen Energy, 2025, 105, 923-931.), the untreated AZ61 magnesium alloy had a hydrogen absorption of 6.0 wt.% in pure hydrogen for 30 minutes. Under a 64% H2 + 36% N2 atmosphere, the initial hydrogen absorption rapidly decreased to 2.0 wt.% within 30 minutes. After preparing a MgF2 coating on the surface of the AZ61 alloy by ball milling, the initial hydrogen absorption increased from 2.0 wt.% to 2.75 wt.% within 30 minutes under a 36% N2 + H2 atmosphere, indicating improved resistance to nitrogen poisoning.

[0004] The technical problems with this solution are mainly reflected in the following two aspects:

[0005] 1. There is a problem of discontinuity in the MgF2 coating, which causes some Mg to come into contact with N2, thus hindering the reaction between H2 and Mg and resulting in poor resistance to nitrogen poisoning. The reason is that when the MgF2 coating is prepared by ball milling, the fluoride formed due to the violent mechanical collision during the ball milling process is insufficient to completely cover the entire alloy particle.

[0006] 2. There is a problem that the MgF2 coating is prone to cracking, which has the same consequences as problem 1, but the cause is different. Specifically, the alloy has a serious volume change problem during the hydrogen absorption and desorption process, which causes the MgF2 coating to continuously expand and contract, eventually cracking.

[0007] Therefore, as can be seen from existing literature 2, achieving nitrogen poisoning resistance based on surface modification has the problem of coating cracking leading to a decrease in hydrogen storage performance.

[0008] Furthermore, the principle of nitrogen poisoning resistance through composite materials differs fundamentally from that of surface modification. The basic principle involves introducing catalytically active elements or compounds into the hydrogen storage material to accelerate the dissociation and recombination of H2, while competitively inhibiting the adsorption of the impurity gas N2. Additionally, the introduced elements or compounds alter the electronic structure of the hydrogen storage material, reducing charge transfer with N2 and decreasing the physical and chemical adsorption capacity of N2, ultimately achieving nitrogen poisoning resistance. For example, existing literature 3 (“Reactivity during cycling of nanocrystalline Mg-based hydrogen storage compounds”, International Journal of Hydrogen Energy, 2002, 27, 909-913.) prepared MgH2-5 at.%V nanocomposites by adding 5 at.%V to MgH2 using a ball milling method. Under a 99.47% H2 + 0.53% N2 atmosphere, after 50 cycles at 300°C, the hydrogen storage capacity of this nanocomposite decreased from 5.6 wt.% in pure H2 to 4.4 wt.%, with a capacity retention rate of less than 80%. Compared to pure MgH2 in existing literature 1, its resistance to nitrogen poisoning is improved.

[0009] However, this technical solution has the following three technical problems:

[0010] 1. Some Mg / MgH2 cannot achieve the effect of reducing the physical and chemical adsorption capacity of N2. The reason is that the powder particles undergo a crushing-cold welding cycle during ball milling. The introduced catalytic element V is easily wrapped by the Mg / MgH2 matrix, and the uniform dispersion of V cannot be achieved.

[0011] 2. The MgH2-5 at%V nanocomposite material prepared by ball milling contains MgO, which leads to a decrease in hydrogen storage capacity. This is because the nanomaterials prepared by ball milling are easily oxidized, and the materials prepared by ball milling are not activated.

[0012] 3. The ball milling method results in high energy consumption and is complicated because high energy consumption is a common problem in ball milling, and Ar gas needs to be continuously introduced for protection during the ball milling process.

[0013] Therefore, as can be seen from existing literature 3, the composite method based on ball milling has the problems of uneven dispersion of elements or compounds and easy oxidation of materials to form MgO, which leads to the decay of hydrogen storage capacity.

[0014] Further comparative analysis of existing literature 2 and existing literature 3 shows that composite design has better resistance to nitrogen poisoning cycles. By replacing the surface coating with composite design, the problem of nitrogen poisoning resistance failure caused by the cracking of the surface coating during hydrogen absorption and desorption can be solved. However, the composite design based on ball milling has the problem of uneven distribution of introduced elements or compounds, which leads to some Mg / MgH2 still being poisoned by N2.

[0015] Furthermore, Problem 1 in existing literature 2 is highly related to Problem 1 in existing literature 3. That is, neither the introduction of elements or surface coatings based on ball milling can achieve uniform distribution of elements or surface coatings, inevitably causing some Mg to come into contact with impurity N2, resulting in poor resistance to nitrogen poisoning.

[0016] To address the issue of uneven distribution of introduced elements or compounds in composite materials, this can be solved by in-situ activation treatment of magnesium-based hydrogen storage alloys to form a catalytically active phase. For example, existing literature 4 (A multiphase Mg-Ni-Nd hydrogen storage alloy based on in-situ activation method and its preparation method, CN202310870697.7, 2023) uses pure Mg, Mg-30Ni, and Mg-50Nd as raw materials and prepares Mg-Ni-Nd hydrogen storage alloys through a process of melting-hot extrusion-filing powdering. After activation treatment, a catalytically active and uniformly distributed NdH2 phase is formed in situ, achieving a long-cycle stability of more than 2900 hydrogen absorption and desorption cycles under pure hydrogen atmosphere and 300℃. However, this technical solution has the problem of not being able to suppress the adsorption of impurity gas N2 on the surface. The reason is that the NdH2 phase formed in situ is only uniformly distributed inside the material and cannot provide sites on the surface to suppress the adsorption of impurity gas N2. In addition, this technical solution only has long-term cycle stability under pure hydrogen conditions and cannot achieve the technical effect of stable hydrogen adsorption and desorption under hydrogen conditions mixed with N2, that is, it has anti-nitrogen poisoning performance.

[0017] Based on existing technology, the technical problems that need to be solved in terms of performance can be summarized in the following three aspects:

[0018] 1. To achieve a uniform distribution of elements or compounds on the surface that catalyze hydrogen absorption and desorption reactions and suppress the adsorption of impurity N2;

[0019] 2. Under hydrogen gas containing impurities such as N2, the material exhibits good resistance to nitrogen poisoning and maintains a stable hydrogen storage capacity during long-term cycling.

[0020] 3. The preparation process is simple and applicable to mass production, reducing energy consumption and time costs. Summary of the Invention

[0021] The present invention aims to provide a magnesium-based hydrogen storage material resistant to nitrogen poisoning and its preparation method. The basic principle is as follows:

[0022] 1. Utilize Nd4Mg 80 The Ni8 phase can form the catalytic NdH2 phase and the hydrogen storage phases Mg and Mg2Ni in situ. Based on this, it further ensures that the NdH2 nanoparticles can be uniformly dispersed on the powder surface, forming a protective barrier to protect the hydrogen storage phases Mg and Mg2Ni from contact with N2 and weakening the poisoning effect. In addition, the NdH2 phase serves as an adsorption and dissociation site for H2, selectively allowing only H2 molecules to pass through, ensuring that the material has a stable hydrogen storage capacity under hydrogen gas mixed with impurities N2.

[0023] 2. To achieve uniform dispersion of NdH2 particles on the powder surface, Nd4Mg in the Mg-Ni-Nd alloy... 80 The mass fraction of Ni8 phase must be greater than 70%. In addition, the Mg-Ni-Nd alloy powder must be subjected to nitrogen poisoning treatment. This not only forms the catalytic phase NdH2 in situ, but also exposes the catalytic phase NdH2 particles while the alloy powder is repeatedly expanded and contracted, causing the powder to break. This results in a structure in which NdH2 particles are evenly distributed on the powder surface.

[0024] 3. A simple nitrogen poisoning resistance treatment method is used to achieve the technical effect of nitrogen poisoning resistance in magnesium-based hydrogen storage materials. As mentioned above, the nitrogen poisoning resistance treatment can not only achieve in-situ formation of NdH2 phase, but also form a structural feature of uniform distribution of NdH2 particles on the powder surface.

[0025] To achieve the above objectives, the present invention adopts the following technical solution:

[0026] A magnesium-based hydrogen storage material resistant to nitrogen poisoning, wherein the atomic ratio of the magnesium-based hydrogen storage material is satisfied that Nd is 2.5-4 at.%, Ni is 8-12 at.%, and the remainder is Mg, and the phase composition of the material is to simultaneously contain Mg, Mg2Ni and NdH2 phases, wherein the Mg and Mg2Ni phases are hydrogen storage phases, the NdH2 phase is a catalytic phase, and the mass percentage of the Mg phase is greater than 50%, the mass percentage of the NdH2 phase is 15%-20%, and the remainder is the Mg2Ni phase;

[0027] The magnesium-based hydrogen storage material has a particle size of 20-50 μm and a microstructure with in-situ formed NdH2 particles uniformly distributed on the surface. The NdH2 phase particles have a size of 20-40 nm.

[0028] In the magnesium-based hydrogen storage material, the catalytic phase NdH2 is composed of Nd4Mg in the Mg-Ni-Nd alloy. 80 Ni8 phase decomposes in situ;

[0029] The Mg-Ni-Nd alloy phase composition is as follows: it contains Nd4Mg 80 Ni8, Mg and Mg2Ni phases, and Nd4Mg 80 The mass fraction of Ni8 phase is greater than 70%, with the remainder being Mg and Mg2Ni.

[0030] When magnesium-based hydrogen storage materials resistant to nitrogen poisoning are used as hydrogen storage materials, in a pure hydrogen atmosphere, after 5 cycles, the hydrogen absorption capacity is 5.00-5.65 wt.% at 300℃ and 3MPa for 30 minutes.

[0031] A method for preparing a magnesium-based hydrogen storage material resistant to nitrogen poisoning involves firstly, under a pure hydrogen atmosphere, with a hydrogen absorption pressure of 4 MPa, a hydrogen absorption temperature of 350°C, and a hydrogen absorption time of 1 h, Mg-Ni-Nd alloy powder (MNN-P) is subjected to hydrogen absorption. Then, hydrogen is released under conditions of a hydrogen release pressure of 0.01 MPa, a hydrogen release temperature of 350°C, and a hydrogen release time of 10 min, thus completing one hydrogen absorption and release treatment. Finally, the hydrogen absorption and release cycle is repeated under certain conditions to complete the nitrogen poisoning resistance treatment of the magnesium-based hydrogen storage material, resulting in a magnesium-based hydrogen storage material Mg / Mg2Ni-NdH2 (MNN-H) resistant to nitrogen poisoning.

[0032] In the repeated hydrogen absorption and desorption cycle, the number of hydrogen absorption and desorption cycles is 10-15 times.

[0033] The obtained magnesium-based hydrogen storage material with nitrogen poisoning resistance exhibits an initial hydrogen absorption capacity of 5.00-5.65 wt.% within 30 minutes at 300℃ and 3MPa in a 99.5% H2 + 0.5% N2 atmosphere, with a hydrogen absorption capacity retention rate greater than 85% after 50 cycles. Similarly, in a 95% H2 + 5% N2 atmosphere, at 300℃ and 3MPa, the initial hydrogen absorption capacity of 5.00-5.65 wt.% within 30 minutes also exhibits a hydrogen absorption capacity retention rate greater than 85% after 30 cycles.

[0034] The technical effects of this invention have been tested and confirmed to be:

[0035] XRD analysis revealed that the Mg-Ni-Nd alloy powder also contains Nd4Mg. 80 Ni8 phase, Mg phase, and Mg2Ni phase were refined by Rietveld to obtain the following mass fractions for each phase: Nd4Mg 80 The Ni8 phase was 82.5 wt.%, the Mg phase was 13.2 wt.%, and the Mg2Ni phase was 4.3 wt.%; XRD results after nitrogen poisoning resistance treatment showed that Nd4Mg 80The Ni8 phase decomposes in situ to form Mg, Mg2Ni and NdH2 phases. After Rietveld refinement, the mass fractions of each phase were: Mg phase 56.3 wt.%, Mg2Ni phase 26.2 wt.%, and NdH2 phase 17.5 wt.%. XRD results after cyclic testing in a poisoning atmosphere of N2 and H2 gas show that the phase composition of the material is not affected by the poisoning atmosphere.

[0036] SEM analysis revealed that the Mg-Ni-Nd alloy powder exhibited a serrated microstructure with a particle size of 200-300 μm. After nitrogen poisoning treatment, the particles broke down, and the particle size was significantly reduced to 10-20% of the original particle size. Furthermore, the serrated morphology disappeared, forming a structure in which NdH2 nanoparticles were uniformly distributed on the powder surface. SEM results after cyclic testing under a poisoning atmosphere of N2 and H2 mixed gas showed that the microstructure of the material powder remained essentially unchanged.

[0037] Cyclic tests under a pure hydrogen atmosphere showed that the magnesium-based hydrogen storage material with nitrogen poisoning resistance achieved an initial hydrogen absorption of 5.38 wt.% at a hydrogen absorption temperature of 300℃, a hydrogen absorption pressure of 3MPa, and a hydrogen absorption time of 30 min. After 5 cycles, the hydrogen absorption was 5.41 wt.%. Cyclic tests under a 99.5% H₂ + 0.5% N₂ atmosphere, under the same conditions as the pure hydrogen atmosphere, showed an initial hydrogen absorption of 5.42 wt.%. After 15 cycles, the hydrogen absorption was 5.30 wt.%, with negligible capacity decay. After 50 cycles, the hydrogen absorption was 4.75 wt.%, with a capacity retention rate of 87.9%. Simultaneously, under a 95% H₂ + 5% N₂ atmosphere, the initial hydrogen absorption was 5.41 wt.%, and after 30 cycles, the hydrogen absorption was 4.80 wt.%, with a capacity retention rate of 88.8%. Therefore, this material has good resistance to nitrogen poisoning.

[0038] Compared with the prior art, the present invention has the following advantages:

[0039] 1. This invention is based on the structure of in-situ formed nanocatalytic phase NdH2 uniformly distributed on the powder surface prepared by anti-nitrogen poisoning treatment, which significantly enhances the material's resistance to nitrogen poisoning in H2+N2 mixed gas;

[0040] 2. Compared with the prior art, the present invention has superior resistance to nitrogen poisoning; at the same time, under the same 95% H2 + 5% N2 atmosphere, compared with Comparative Example 1, the capacity retention rate of the first hydrogen absorption is increased by nearly 1.7 times, and when the number of cycles is 10, the hydrogen storage capacity increases by more than 3.0 wt.%, and the capacity retention rate is increased by more than 2.5 times.

[0041] 3. The preparation method of this invention is simple, safe and efficient, and has a high commercial application potential. Attached Figure Description

[0042] Figure 1 The XRD pattern of MNN-P in Example 1;

[0043] Figure 2 The XRD patterns of MNN-A and MNN-H in Example 1;

[0044] Figure 3 The image shown is a SEM image of MNN-P in Example 1.

[0045] Figure 4 The image shown is the SEM image of MNN-A in Example 1.

[0046] Figure 5 The image shown is the SEM image of MNN-H in Example 1.

[0047] Figure 6 These are the high-magnification SEM and STEM-EDS images of MNN-H from Example 1;

[0048] Figure 7 The curves showing the hydrogen storage capacity versus cycle number of MNN-H in Example 1 under pure hydrogen and N-0.5 atmosphere conditions are shown.

[0049] Figure 8 The XRD pattern of MNN-HN-0.5 in Example 1;

[0050] Figure 9 The image shown is a SEM image of MNN-HN-0.5 in Example 1.

[0051] Figure 10 The curves showing the hydrogen storage capacity versus cycle number of MNN-H in Example 1 under pure hydrogen and N-5 atmosphere conditions, respectively;

[0052] Figure 11 The curves show the hydrogen storage capacity versus cycle number of MN-H in Comparative Example 1 under pure hydrogen and N-5 atmosphere conditions. Detailed Implementation

[0053] The present invention will be further described in detail through embodiments and with reference to the accompanying drawings, but this is not intended to limit the scope of the invention.

[0054] Example 1

[0055] A method for preparing a magnesium-based hydrogen storage material resistant to nitrogen poisoning, namely a method for treating magnesium-based hydrogen storage materials to resist nitrogen poisoning, includes the following steps: [The method involves a material with the chemical formula Mg...] 88.5 Ni 8.0 Nd 3.5The Mg-Ni-Nd alloy powder, abbreviated as MNN-P, is first subjected to hydrogen absorption at a hydrogen absorption pressure of 4 MPa, a hydrogen absorption temperature of 350℃, and a hydrogen absorption time of 1 h. Then, hydrogen is released at a hydrogen release pressure of 0.01 MPa, a hydrogen release temperature of 350℃, and a hydrogen release time of 10 min, thus completing one hydrogen absorption and release treatment. Finally, the hydrogen absorption and release treatment is repeated 10 times to complete the nitrogen poisoning resistance treatment of the magnesium-based hydrogen storage material, resulting in a magnesium-based hydrogen storage material Mg / Mg2Ni-NdH2, abbreviated as MNN-H, which is resistant to nitrogen poisoning.

[0056] To demonstrate the difference between nitrogen poisoning treatment and conventional activation treatment, MNN-P was activated using conventional activation treatment. Unless otherwise specified, the nitrogen poisoning treatment method was the same, except that the hydrogen absorption and desorption treatment was performed three times. The resulting material was named MNN-A.

[0057] To demonstrate the effect of nitrogen poisoning resistance on phase composition and content, XRD analysis and Rietveld refinement were performed on MNN-H. Meanwhile, for comparison, XRD analysis and Rietveld refinement were performed on MNN-P as a baseline reference. Furthermore, to demonstrate the difference between nitrogen poisoning resistance and conventional activation treatment, XRD analysis and Rietveld refinement were performed on MNN-A.

[0058] The test results of MNN-P are as follows Figure 1 As shown, MNN-P simultaneously contains Nd4Mg 80 Characteristic peaks of Ni8 phase, Mg phase, and Mg2Ni phase; and, calculated, their mass fractions are: Nd4Mg 80 The Ni8 phase was 82.5 wt.%, the Mg phase was 13.2 wt.%, and the Mg2Ni phase was 4.3 wt.%.

[0059] The test results of MNN-A are as follows Figure 2 As shown, MNN-A simultaneously contains characteristic peaks of Mg, Mg2Ni and NdH2 phases, and the calculated mass fractions are: Mg phase 56.5 wt.%, Mg2Ni phase 26.0 wt.%, and NdH2 phase 17.5 wt.%.

[0060] The test results of MNN-H are as follows Figure 2 As shown, MNN-H simultaneously contains characteristic peaks of Mg, Mg2Ni and NdH2 phases, and the calculated mass fractions are: Mg phase 56.3 wt.%, Mg2Ni phase 26.2 wt.%, and NdH2 phase 17.5 wt.%.

[0061] A comparison of the test results of MNN-P and MNN-H shows that, after nitrogen poisoning treatment, the Nd4Mg in MNN-P... 80 The Ni8 phase decomposes in situ to form the Mg phase, Mg2Ni phase and NdH2 phase, among which the Mg and Mg2Ni phases are hydrogen storage phases and the NdH2 phase is a catalytic phase;

[0062] A comparison of the test results of MNN-A and MNN-H shows that there is no substantial difference in phase composition and phase content between MNN-H and MNN-A.

[0063] To further demonstrate the effect of nitrogen poisoning resistance on microstructure morphology, SEM was performed on MNN-H. Meanwhile, for comparison, SEM was performed on MNN-P as a baseline reference. Furthermore, to demonstrate the difference between nitrogen poisoning resistance and conventional activation treatment, SEM was performed on MNN-A.

[0064] The test results of MNN-P are as follows Figure 3 As shown, the microstructure of MNN-P is serrated, and the particle size of MNN-P is 200-300 μm.

[0065] The test results of MNN-A are as follows Figure 4 As shown, the microstructure of MNN-A is not substantially different from that of MNN-P, that is, it is serrated and the particle size is 200-300μm.

[0066] The test results of MNN-H are as follows Figure 5 As shown, the microstructure of MNN-H is a structure in which fine particles are uniformly distributed on the surface, and the particle size of MNN-H is 30-40 μm.

[0067] Comparing the test results of MNN-P and MNN-H, it can be seen that after nitrogen poisoning treatment, the particle size is significantly reduced to 10-20% of the original particle size, and the serrated morphology disappears. The reason is that during the hydrogen absorption and desorption cycle treatment, MNN-P not only forms the catalytic phase NdH2 in situ, but also repeatedly expands and contracts, causing the particles to break down. This not only significantly reduces the particle size, but also exposes the catalytic phase NdH2 particles.

[0068] A comparison of the test results of MNN-A and MNN-H shows that conventional activation treatment cannot achieve the technical effect of nitrogen poisoning treatment, specifically manifested in a significant reduction in particle size and exposure of NdH2 particles in the catalytic phase.

[0069] To further verify the microstructure and composition of MNN-H, high-magnification SEM and STEM-EDS tests were performed. The test results are as follows: Figure 6As shown, the microstructure of MNN-H is characterized by the presence of nanoparticles composed of NdH2, with the NdH2 particles having a size of 20-30 nm.

[0070] To demonstrate that MNN-H has resistance to nitrogen poisoning, cyclic testing was conducted on MNN-H under poisoning atmosphere conditions. Meanwhile, for comparison, cyclic testing was conducted on MNN-H under pure hydrogen atmosphere conditions as a baseline reference.

[0071] The specific method for the cycle test is as follows: under certain atmospheric conditions, hydrogen absorption and hydrogen release tests are performed. Completing one hydrogen absorption and hydrogen release test constitutes one cycle test.

[0072] The conditions for the hydrogen absorption test are: hydrogen absorption temperature of 300℃, hydrogen absorption pressure of 3MPa, and hydrogen absorption time of 30min.

[0073] The conditions for the hydrogen release test are as follows: hydrogen pressure of 0.01 MPa, hydrogen release temperature of 300°C, and hydrogen release time of 30 min.

[0074] The poisoning atmosphere is a mixture of N2 and H2 gases, and the volume fraction of N2 is 0.5%. Therefore, the poisoning atmosphere is simply referred to as N-0.5. Thus, the MNN-H after cyclic testing is named MNN-HN-0.5.

[0075] The cycle test results of MNN-H under pure hydrogen atmosphere conditions are as follows: Figure 7 As shown,

[0076] The initial hydrogen absorption reached 5.38 wt.%.

[0077] When the number of cycles is 5, the hydrogen absorption is 5.41 wt.%, the capacity does not decrease, and the cycle stability is good;

[0078] Under the poisoning atmosphere of N-0.5, the cyclic test results of MNN-H are as follows: Figure 7 As shown,

[0079] The initial hydrogen absorption reached 5.41 wt.%.

[0080] When the number of cycles is 15, the hydrogen absorption is 5.30 wt.%, and the decrease in hydrogen absorption capacity is negligible;

[0081] When the number of cycles was 30, the hydrogen absorption was 5.06 wt.%, and the hydrogen absorption capacity retention rate was 93.5%.

[0082] When the number of cycles was 50, the hydrogen absorption was 4.75 wt.%, and the hydrogen absorption capacity retention rate was 87.9%.

[0083] Test results show that MNN-H has the same hydrogen absorption performance under N-0.5 atmosphere as under pure hydrogen atmosphere, that is, it has good resistance to nitrogen poisoning and cycle stability.

[0084] To demonstrate the reason for MNN-H's resistance to nitrogen poisoning, specifically the effect of the poisoning atmosphere N-0.5 on the phase composition of MNN-H, XRD tests were performed on MNN-HN-0.5. The test results are as follows: Figure 8 As shown, the phase composition of MNN-HN-0.5 is the same as that of MNN-H, that is, it simultaneously contains characteristic peaks belonging to the Mg, Mg2Ni, and NdH2 phases. The test results show that under the poisoning atmosphere N-0.5, the phase composition of MNN-H is not affected by the poisoning atmosphere.

[0085] To further demonstrate the reason for MNN-H's resistance to nitrogen poisoning, specifically the effect of the poisoning atmosphere N⁻⁰.⁵ on the microstructure of MNN-H, SEM testing was performed on MNN-HN⁻⁰.⁵. The test results are as follows: Figure 9 As shown, the microstructure of MNN-HN-0.5 is basically the same as that of MNN-H, that is, NdH2 nanoparticles are uniformly distributed on the surface. However, in MNN-HN-0.5, the NdH2 particle size increases to 50-80 nm. This is because the growth of NdH2 particles under high temperature conditions leads to an increase in the size of the NdH2 particles.

[0086] A comparison of MNN-H and MNN-HN-0.5 reveals that MNN-H shows no significant change under poisoning atmosphere conditions, indicating it is unaffected by the poisoning atmosphere. This is because the uniformly distributed NdH2 phase on its surface serves as adsorption and dissociation sites for H2 molecules. Simultaneously, it acts as a barrier, inhibiting direct contact between N2 and the hydrogen storage phases Mg and Mg2Ni, thus ensuring the stability of hydrogen absorption during nitrogen poisoning cycle testing.

[0087] To demonstrate that the MNN-H of the present invention has good resistance to nitrogen poisoning and cyclic stability, a comparison is made with existing literature where the N2 concentration is on the same order of magnitude as the poisoning atmosphere N-0.5 in Example 1 of the present invention.

[0088] According to existing literature 1-1, pure Mg under a 99.503% H2 + 0.497% N2 atmosphere, at a hydrogen absorption temperature of 395℃ and a hydrogen absorption pressure of 3MPa, exhibits a rapid decrease in hydrogen absorption capacity after 5 cycles, with a capacity retention rate of less than 70%.

[0089] According to existing literature 1-2, the hydrogen storage capacity of MgH2-5 at%V nanocomposite material decreased from 5.6 wt.% under pure H2 atmosphere to 4.4 wt.% after 50 cycles at 300℃ under 99.47% H2 + 0.53% N2 atmosphere, with a capacity retention rate of less than 80%.

[0090] The comparison shows that the materials obtained in existing literatures 1-1 and 1-2 have lower resistance to nitrogen poisoning and long-cycle stability than the MNN-H of this invention.

[0091] 1-1.ASPedersen, B. Larsen, The storage of industrially pure hydrogen in magnesium, International Journal of Hydrogen Energy, 18 (1993) 297-300.

[0092] 1-2. S. Bouaricha, J. Huot, D. Guay, R. Schulz, Reactivity during cycling of nanocrystalline Mg-based hydrogen storage compounds, International Journal of Hydrogen Energy, 27 (2002) 909-913.

[0093] The following conclusions can be drawn by comparing with existing literature:

[0094] The chemical formula is Mg 88.5 Ni 8.0 Nd 3.5 Mg / Mg2Ni-Nd alloy powder was subjected to nitrogen poisoning resistance treatment to obtain a nitrogen-poisoned magnesium-based hydrogen storage material, Mg / Mg2Ni-NdH2. The in-situ formed NdH2 phase is uniformly distributed on the powder surface, forming a protective layer that hinders the contact between nitrogen and the hydrogen storage phases Mg and Mg2Ni, thus weakening the poisoning effect of N2. Simultaneously, NdH2 acts as a catalytic phase, providing sites for H2 adsorption and dissociation, effectively ensuring the stability of the material's hydrogen absorption and desorption capacity under hydrogen conditions mixed with 0.5% N2. The nitrogen-poisoned magnesium-based hydrogen storage material Mg / Mg2Ni-NdH2 of this invention exhibits superior nitrogen poisoning resistance compared to materials in existing literature.

[0095] To further demonstrate the nitrogen poisoning resistance of MNN-H, cyclic testing was conducted on MNN-H under a higher concentration of poisoning atmosphere. Specifically, the poisoning atmosphere was a mixture of N2 and H2 gases; however, the volume fraction of N2 was 5%, therefore, the poisoning atmosphere is simply referred to as N-5. This indicates that the N2 poisoning atmosphere concentration in N-5 is 10 times that in existing literature 1-1 and 1-2.

[0096] Under the toxic atmosphere N-5, the cyclic test results of MNN-H are as follows: Figure 10 As shown,

[0097] The initial hydrogen absorption reached 5.41 wt.%.

[0098] When the number of cycles is 15, the hydrogen absorption is 5.35 wt.%, and the decrease in hydrogen absorption capacity is negligible;

[0099] When the number of cycles was 30, the hydrogen absorption was 4.80 wt.%, and the hydrogen absorption capacity retention rate was 88.8%.

[0100] Comparison with the cyclic test results under N-0.5 atmosphere conditions shows that even when the concentration of the poisoning atmosphere is increased by 10 times, MNN-H still exhibits good resistance to nitrogen poisoning and cyclic stability.

[0101] The following conclusions can be drawn from the test results of MNN-H under N-5 poisoning atmosphere:

[0102] MNN-H not only exhibits good resistance to nitrogen poisoning at low concentrations of N2, but also maintains good resistance to nitrogen poisoning and cycle stability at high concentrations of N2. Furthermore, the resistance to nitrogen poisoning of MNN-H far exceeds that of existing literature 1-1 and 1-2.

[0103] To further demonstrate the nitrogen poisoning resistance and cycle stability of MNN-H, Comparative Example 1 is provided, using a conventional commercial magnesium-based hydrogen storage alloy with similar atomic ratios of Mg and Ni. 90.5 Ni 9.5 Compare them.

[0104] Comparative Example 1

[0105] Conventional commercial magnesium-based hydrogen storage alloys Mg 90.5 Ni 9.5 Using the same nitrogen poisoning treatment method as in Example 1, the resulting alloy is referred to as MN-H.

[0106] To demonstrate the performance of MN-H under poisoned atmosphere conditions, cyclic testing was conducted on MN-H under an N-5 poisoned atmosphere. Simultaneously, for comparison, cyclic testing was performed on MN-H under a pure hydrogen atmosphere as a baseline reference.

[0107] The cyclic test results of MN-H under pure hydrogen atmosphere conditions are as follows: Figure 11 As shown,

[0108] The initial hydrogen absorption reached 5.40 wt.%.

[0109] When the number of cycles was 5, the hydrogen absorption was 5.30 wt.%, and the hydrogen absorption capacity decreased slightly by 0.1 wt.%.

[0110] The cyclic test results of MN-H under the poisonous atmosphere N-5 are as follows: Figure 11 As shown,

[0111] The initial hydrogen absorption was only 3.18 wt.%; the initial hydrogen absorption decreased sharply, with a 40% reduction in hydrogen absorption capacity compared to 5.40 wt.% under pure hydrogen conditions.

[0112] When the number of cycles was 10, the hydrogen absorption was only 2.01 wt.% and the capacity retention was only 37.2%.

[0113] Test results show that MN-H does not have resistance to nitrogen poisoning, meaning that conventional magnesium-based hydrogen storage alloys cannot obtain resistance to nitrogen poisoning even with nitrogen poisoning treatment methods.

[0114] Further comparison with the cyclic test results of MNN-H reveals that the reason why MNN-H acquires resistance to nitrogen poisoning is, firstly, by introducing Nd element to form Nd4Mg. 80 The Ni8 phase is then subjected to nitrogen poisoning treatment to achieve a uniformly distributed NdH2 phase on the surface. Finally, NdH2 acts as a catalytic phase, providing sites for H2 adsorption and dissociation. At the same time, it acts as a barrier, inhibiting direct contact between N2 and the hydrogen storage phases Mg and Mg2Ni, thus ensuring the stability of the material's hydrogen adsorption and desorption capacity under hydrogen conditions mixed with N2.

Claims

1. A magnesium-based hydrogen storage material resistant to nitrogen poisoning, characterized in that: The atomic ratio of the magnesium-based hydrogen storage material is as follows: Nd is 2.5-4 at.%, Ni is 8-12 at.%, and the remainder is Mg. Furthermore, the phase composition of the material includes Mg, Mg2Ni and NdH2 phases, wherein Mg and Mg2Ni phases are hydrogen storage phases, NdH2 phase is a catalytic phase, and the mass percentage of Mg phase is greater than 50%, the mass percentage of NdH2 phase is 15%-20%, and the remainder is Mg2Ni phase. The magnesium-based hydrogen storage material has a particle size of 20-50 μm and a microstructure with in-situ formed NdH2 particles uniformly distributed on the surface. The NdH2 phase particles have a size of 20-40 nm. In the magnesium-based hydrogen storage material, the catalytic phase NdH2 is composed of Nd4Mg in the Mg-Ni-Nd alloy. 80 Ni8 phase decomposes in situ; The Mg-Ni-Nd alloy phase composition is as follows: it contains Nd4Mg 80 Ni8, Mg and Mg2Ni phases, and Nd4Mg 80 The mass fraction of Ni8 phase is greater than 70%, with the remainder being Mg and Mg2Ni; When used as a hydrogen storage material, in a pure hydrogen atmosphere, after 5 cycles, the hydrogen absorption capacity is 5.00-5.65 wt.% at 300℃ and 3 MPa for 30 minutes.

2. A method for preparing a magnesium-based hydrogen storage material resistant to nitrogen poisoning, characterized in that: First, under a pure hydrogen atmosphere, with a hydrogen absorption pressure of 4 MPa, a hydrogen absorption temperature of 350℃, and a hydrogen absorption time of 1 h, Mg-Ni-Nd alloy powder, abbreviated as MNN-P, is subjected to hydrogen absorption. Then, hydrogen is released under the conditions of a hydrogen release pressure of 0.01 MPa, a hydrogen release temperature of 350℃, and a hydrogen release time of 10 min, thus completing one hydrogen absorption and release treatment. Finally, the hydrogen absorption and release cycle treatment is repeated to complete the nitrogen poisoning resistance treatment of the magnesium-based hydrogen storage material, resulting in a magnesium-based hydrogen storage material Mg / Mg2Ni-NdH2, abbreviated as MNN-H, which is resistant to nitrogen poisoning. In the repeated hydrogen absorption and desorption cycle, the number of hydrogen absorption and desorption cycles is 10-15 times.

3. The preparation method according to claim 2, characterized in that: The obtained magnesium-based hydrogen storage material with resistance to nitrogen poisoning showed an initial hydrogen absorption capacity of 5.00-5.65 wt.% within 30 min at 300℃ and 3 MPa in a 99.5% H2 + 0.5% N2 atmosphere, and a hydrogen absorption capacity retention rate of more than 85% after 50 cycles.

4. The preparation method according to claim 2, characterized in that: The obtained magnesium-based hydrogen storage material with nitrogen poisoning resistance has an initial hydrogen absorption capacity of 5.00-5.65 wt.% within 30 min at 300℃ and 3 MPa in a 95% H2+5% N2 atmosphere, and a hydrogen absorption capacity retention rate of more than 85% after 30 cycles.

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