Sm-Mg-based hydrogen storage alloy composite material added with multivalent niobium oxide and preparation method of Sm-Mg-based hydrogen storage alloy composite material

Abstract

The invention discloses a Sm-Mg-based hydrogen storage alloy composite material added with multivalent niobium oxide and a preparation method of the Sm-Mg-based hydrogen storage alloy composite material, the chemical composition general formula of the Sm-Mg-based hydrogen storage alloy composite material is Sm < x > Mg < 100-x > + 10 wt.% H-Nb2O5, x is an atomic ratio, and x is greater than or equal to 1.7 and less than or equal to 4.5; according to the hydrogen storage alloy composite material, H-Nb2O5 powder is obtained through a hydrothermal method and a reduction method, and then the H-Nb2O5 powder and Sm-Mg-based hydrogen storage alloy are subjected to hydrogenation and ball milling to prepare the hydrogen storage alloy composite material. The preparation method is simple, the process is easy to control, the prepared hydrogen storage alloy composite material generates a multivalent catalytic center in the hydrogen absorption and desorption process, the weakening effect on Mg-H bonds is enhanced, meanwhile, nanocrystalline MgO is generated, capacity fading caused by an Mg-MgO core-shell structure is avoided, a bifunctional Nb / Sm3H7 interface is finally constructed, the dynamic performance of MgH2 is improved, and Nb is prevented from being hydrogenated into NbH2; the initial hydrogen desorption temperature of the composite material is less than 220 DEG C, and the capacity retention ratio is greater than 98% after 50 cycles at 325 DEG C.

Description

Technical Field

[0001] This invention belongs to the field of solid hydrogen storage materials, and relates to a Sm-Mg-based hydrogen storage alloy composite material with added multivalent niobium oxides and its preparation method. Background Technology

[0002] Hydrogen energy has garnered significant attention as a green and sustainable energy source, boasting advantages such as high energy density, high calorific value, cleanliness, zero emissions, and versatility. However, the current lack of safe and efficient hydrogen storage and transportation technologies severely hinders the large-scale utilization of hydrogen energy. Currently, there are three main methods for hydrogen storage: high-pressure gaseous hydrogen storage, cryogenic liquid hydrogen storage, and solid-state hydrogen storage. Compared to the risks of hydrogen leakage and material embrittlement associated with the other two methods, solid-state hydrogen storage achieves fundamental and safe fixation of hydrogen atoms by forming metal hydrides through chemical bonds between hydrogen and the storage material.

[0003] Among various hydrogen storage materials, magnesium-based hydrogen storage materials are the most promising carriers due to their high hydrogen storage density (up to 7.6 wt.%), eco-friendliness, and high geological abundance. However, the presence of energy barriers for Mg-H bond breaking, H2 dissociation / reorganization, and H diffusion poses challenges to the slow kinetics and excessively high thermodynamic stability of magnesium-based hydrogen storage materials. Furthermore, the gradual growth of the Mg / MgH2 phase and particle agglomeration severely hinder hydrogen diffusion, leading to weakened hydrogenation kinetics and reduced capacity. Catalyst doping, alloying, and nano-sizing can mitigate these problems. Among these methods, catalyst doping composite alloying is an effective way to improve the performance of magnesium-based hydrogen storage materials. Introducing a second phase (such as ReH2) through alloying... x Magnesium-based hydrogen storage materials (MgO) can provide hydrogen diffusion channels and accelerate hydrogen diffusion, thus improving the kinetic performance of magnesium-based hydrogen storage materials. Simultaneously, trace amounts of nano-MgO can also provide hydrogen diffusion channels, which is beneficial to the kinetic performance of magnesium-based hydrogen storage materials. However, excessive MgO can form a Mg-MgO core-shell structure, reducing the active sites for hydrogen absorption and desorption, leading to capacity decay. Transition metal-based catalysts have significant effects on hydrogen dissociation and recombination and Mg-H bond breaking. However, some metastable transition metal-based catalysts (TiO2, V2O5, and Nb2O5, etc.) react with Mg redox reactions to generate excessive MgO, forming a Mg-MgO core-shell structure, leading to capacity decay. Furthermore, the hydrogenation of transition metal elements (Ti, V, and Nb, etc.) into hydrides leads to catalytic activity decay. Therefore, how to maintain the catalytic activity of transition metal-based catalysts while avoiding the formation of Mg-MgO core-shell structures—that is, ensuring the cycling stability of magnesium-based hydrogen storage materials while improving their kinetic performance and reducing their dehydrogenation temperature—is currently a hot research topic.

[0004] Based on this, the present invention is proposed. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention aims to provide a Sm-Mg-based hydrogen storage alloy composite material with added multivalent niobium oxides and its preparation method, wherein the general chemical formula is Sm x Mg 100-x +10wt.%H-Nb2O5, where x is the atomic ratio, 1.7≤x≤4.5; the above hydrogen storage alloy composite material is prepared by obtaining H-Nb2O5 powder through hydrothermal and reduction methods, and then preparing it by hydrogenation and ball milling with Sm-Mg-based hydrogen storage alloy; the preparation method of this invention is simple and the process is easy to control. The prepared hydrogen storage alloy composite material generates multivalent catalytic centers (Nb2O5) during hydrogen absorption and desorption. 5+ 、Nb 4+ 、Nb 2+ The composite material enhances the weakening effect of Mg-H bonds by adding Nb, while simultaneously generating nanocrystalline MgO, thus avoiding the capacity decay caused by the Mg-MgO core-shell structure. This ultimately constructs a bifunctional Nb / Sm3H7 interface, which improves the kinetic performance of MgH2 and prevents Nb from hydrogenating to NbH2, maintaining its catalytic activity. The initial hydrogen desorption temperature of this composite material is less than 220℃, and the capacity retention rate is greater than 98% after 50 cycles at 325℃.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A Sm-Mg-based hydrogen storage alloy composite material with added multivalent niobium oxides, characterized in that its general chemical formula is Sm x Mg 100-x +10wt.%H-Nb2O5, where x is the atomic ratio, 1.7≤x≤4.5.

[0008] This invention also provides a method for preparing Sm-Mg-based hydrogen storage alloy composite materials with added multivalent niobium oxides, which is carried out in the following order:

[0009] S1. Preparation of H-Nb2O5

[0010] S11. Dissolve niobium oxalate and ammonium carbonate in 60 mL of deionized water, stir at 100-400 rpm for 20-40 min, and then sonicate for 30 min to obtain the precursor solution.

[0011] S12. The precursor solution was transferred to a polytetrafluoroethylene liner and hydrothermally treated at 180°C for 12 hours. The precipitate was washed with deionized water, centrifuged at 7000 rpm for 5 minutes and washed 3 times. After drying in an 80°C forced-air drying oven for 6 hours, it was calcined in air at 500°C for 2 hours to obtain the Nb2O5 precursor.

[0012] S13. Grind the Nb2O5 precursor and NaBH4 in an argon glove box for 30 min, place them in an alumina crucible, perform thermal reduction under an argon atmosphere, wash with deionized water at 7000 rpm for 5 min to remove residual salts, and freeze-dry at -40℃ for 24 h to obtain H-Nb2O5 powder.

[0013] S2, Preparation of Sm x Mg 100-x +10wt.%H-Nb2O5 hydrogen storage alloy composite material

[0014] S21. Under an argon atmosphere, Sm x Mg 100-x The alloy powder was mixed with 10 wt.% H-Nb2O5 powder and placed in a sample tube for hydrogenation to obtain a black powder.

[0015] S22. Under an argon atmosphere, the black powder was placed in a stainless steel ball mill jar and ball-milled to obtain Sm. x Mg 100-x +10wt.%H-Nb2O5 hydrogen storage alloy composite material.

[0016] As a limitation of the preparation method of the present invention, in step S11, the molar ratio of niobium oxalate to ammonium carbonate is 1:(2.5-5.0).

[0017] As another limitation of the preparation method of the present invention, in step S13, the molar ratio of the Nb2O5 precursor to NaBH4 is 1:(10-20).

[0018] As a third limitation of the preparation method of the present invention, in step S13, the temperature of the thermal reduction is 400-500℃ and the time is 2-3h.

[0019] In this invention, the thermal reduction process is crucial, affecting the valence state of Nb and the morphology of its nanosheet clusters in the H-Nb₂O₅ catalyst. When the thermal reduction temperature is 400-500℃ and the reduction time is 2-3h, it influences the redox rate of the NaBH₄ and Nb₂O₅ precursors, thus allowing H-Nb₂O₅ to retain Nb 5+ and Nb 4+ This process improves catalytic activity while maintaining the nanosheet morphology to prevent agglomeration, thus increasing active sites and enhancing the catalytic performance of H-Nb2O5. However, when the reduction temperature is below 400℃ and the reduction time is less than 2 hours, NaBH4 is difficult to redox with the Nb2O5 precursor, resulting in the catalyst still reacting primarily with Nb2O5. 5+The presence of these substances reduces their catalytic performance. When the reduction temperature is greater than 500℃ and the reduction time is greater than 3h, a violent redox reaction will occur between NaBH4 and the Nb2O5 precursor, which will cause the Nb2O5 precursor to collapse and agglomerate rapidly, resulting in a reduction of catalytic active sites and thus reducing the catalytic performance of the catalyst.

[0020] As a fourth limitation of the preparation method of the present invention, in step S21, the temperature during hydrogenation is 300-450℃, the pressure is 3-4.5MPa, and the time is 10-12h.

[0021] In this invention, the temperature, pressure, and hydrogenation time during hydrogenation are crucial and affect Sm x Mg 100-x Can Sm3H7 and MgH2 be completely hydrogenated and decomposed into Sm3H7 and MgH2, and can H-Nb2O5 undergo a catalytic activity transformation? When the hydrogenation temperature is 300-450℃ and the pressure is 3-4.5MPa, can Sm3H7 be completely hydrogenated and decomposed into Sm3H7 and MgH2, and can H-Nb2O5 undergo a catalytic activity transformation? x Mg 100-x Complete hydrogenation decomposes into Sm3H7 and MgH2. During the reduction of H-Nb2O5, nanocrystalline MgO is generated, thereby enabling Sm... x Mg 100-x +10wt.% H-Nb2O5 composite hydrogen storage material is fully ball-milled in the subsequent process to generate a micron-sized MgH2 matrix, while avoiding the hydrogen storage capacity decay caused by the Mg-MgO core-shell structure; when the temperature is less than 300℃ and the pressure is less than 3MPa, Sm x Mg 100-x It cannot be completely hydrogenated and decomposed into Sm3H7 and MgH2, and still retains Sm5Mg. 41 Phase and Mg phase, due to Sm5Mg 41 The Sm phase and Mg phase have high ductility, which leads to the Sm phase after ball milling x Mg 100-x The MgH2 matrix of the +10wt.% H-Nb2O5 composite hydrogen storage material has a large particle size, and its hydrogen storage capacity decreases. When the temperature exceeds 450℃ and the pressure exceeds 4.5MPa, a violent reaction occurs between H-Nb2O5 and Mg to form a Mg-MgO core-shell structure, resulting in a significant decrease in its hydrogen storage capacity. Hydrogenation for 10-12 hours is to promote the growth of Sm under suitable hydrogenation temperature and pressure. x Mg 100-x While achieving complete hydrogenation and decomposition, it ensures the slow reduction of H-Nb2O5 to generate nanocrystalline MgO, and avoids the formation of Mg-MgO core-shell structure.

[0022] As a fifth limitation of the preparation method of the present invention, in step S22, the ball milling process is as follows: stainless steel balls and materials with a ball-to-material ratio of (30-50):1 are placed in a ball mill and ball milled at 350-450 rpm for 8-12 cycles, one cycle being: ball milling for 10-20 min, with an interval of 10-20 min.

[0023] This invention prepares Sm by a hydrogenation-composite high-energy ball milling method. x Mg 100-x +10wt.% H-Nb2O5 composite hydrogen storage material. x Mg 100-x In-situ hydrogenation decomposition of the Sm3H7 and MgH2 phases in the alloy, along with redox reactions with H-Nb2O5, is employed. High-energy ball milling then reduces the MgH2 matrix size to the micrometer scale, significantly shortening the hydrogen diffusion distance and promoting the uniform dispersion of in-situ generated Sm3H7. This provides additional hydrogen diffusion pathways while accelerating hydrogen diffusion, thereby improving the material's hydrogen storage performance. Simultaneously, the hydrogenation-composite high-energy ball milling method further excites the Sm3H7 phase. x Mg 100-x The chemical reaction between +10wt.% H-Nb2O5 promotes the redox reaction between H-Nb2O5 and Mg through high mechanical energy, generating a multivalent catalytic center (Nb). 5+ 、Nb 4+ 、Nb 2+ By combining Nb and nanocrystalline MgO, a bifunctional Nb / Sm3H7 interface is ultimately constructed, avoiding the formation of a Mg-MgO core-shell structure and improving the catalytic activity for MgH2. Due to the extremely high diffusion barrier of H within the bulk MgO phase, the Mg-MgO core-shell structure would lead to a decrease in the material's hydrogen storage capacity. This invention uses NaBH4 to reduce Nb2O5 precursor powder to generate amorphous H-Nb2O5, in which some Nb... 5+ Reduced to Nb 4+ This significantly reduces the amount of MgO generated by the redox reaction of H-Nb2O5 with Mg, preventing excessive MgO growth that could lead to the formation of a passivation layer and promoting the formation of nanocrystalline MgO. Nanocrystalline MgO provides numerous phase boundaries, opening up the MgO / MgH2 interface as a hydrogen diffusion channel, thereby further improving the hydrogen storage performance of the material.

[0024] This invention introduces multivalent Nb-based oxides and Sm3H7 through interface engineering to construct a dual-functional Nb / Sm3H7 interface. This interface lowers the energy barrier for Mg-H bond dissociation and promotes hydrogen diffusion and recombination, thereby accelerating dehydrogenation kinetics. Simultaneously, this interface stabilizes the catalytic activity of Nb by promoting hydrogen diffusion and inhibiting further hydrogenation of Nb to NbH2. x It maintains the multivalent niobium species (Nb 5+ 、Nb4+ 、Nb 2+ The composite material contains Nb and maintains its catalytic ability to dissociate Mg-H bonds, while nanocrystalline MgO provides additional hydrogen channels. The excellent synergistic catalytic effect within the composite material counteracts the prolonged hydrogen diffusion distance caused by agglomeration, ultimately achieving better cycle stability.

[0025] The above-mentioned technical solution of the present invention is as a whole, and the various steps are closely related and mutually influential, which together determine the morphological characteristics and performance of the product.

[0026] The above technical solution has the following advantages or beneficial effects:

[0027] 1. This invention is based on Sm x Mg 100-x The alloy powder and H-Nb2O5 powder with nanosheet clusters were prepared by hydrogenation composite high-energy ball milling, wherein the Nb in the H-Nb2O5 powder is mainly Nb. 5+ and Nb 4+ The Nb-based multivalent catalytic centers (Nb) gradually generated during the preparation and hydrogen adsorption / desorption processes of the composite material 5+ 、Nb 4+ 、Nb 2+ The weakening effect of Nb on the Mg-H bond energy gradually increases, and together with the Sm3H7 phase and nanocrystalline MgO, it provides hydrogen channels, avoiding the capacity decay caused by the formation of the Mg-MgO core-shell structure. Ultimately, a bifunctional Nb / Sm3H7 interface is constructed. This interface effectively weakens the Mg-H bond, improving the hydrogen adsorption and desorption kinetics of the material, while also greatly promoting H diffusion, thus preventing the hydrogenation of Nb to form NbH. x The compound retains the catalytic activity of Nb;

[0028] 2. The Sm prepared by this invention x Mg 100-x The +10wt.%H-Nb2O5 composite material absorbs hydrogen at low temperatures and has an initial hydrogen release temperature of less than 220℃. After 50 cycles at 325℃, the capacity retention rate is greater than 98%.

[0029] 3. The preparation method of this invention is simple, the process is easy to control, and it is convenient for industrial application.

[0030] This invention is applicable to the preparation of Sm x Mg 100-x +10wt.% H-Nb2O5 composite material.

[0031] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0032] Figure 1The hydrogen absorption and desorption curves and cycling curves of the hydrogen storage alloy composite material prepared in Example 1 of the present invention are shown, wherein: a is the hydrogen absorption curve at 250℃, b is the hydrogen desorption curve at 300℃, and c is the cycling curve at 325℃.

[0033] Figure 2 The images shown are HRTEM images of the hydrogen storage alloy composite material prepared in Example 1 of the present invention after complete hydrogen absorption, where: a and b are HRTEM images of Example 1 after complete hydrogen absorption;

[0034] Figure 3 The hydrogen absorption and desorption curves and cycling curves of the hydrogen storage alloy composite material prepared in Example 2 of the present invention are shown, wherein: a is the hydrogen absorption curve at 250℃, b is the hydrogen desorption curve at 300℃, and c is the cycling curve at 325℃.

[0035] Figure 4 The hydrogen absorption and desorption curves and cycling curves of the hydrogen storage alloy composite material prepared in Example 3 of the present invention are shown, wherein: a is the hydrogen absorption curve at 250℃, b is the hydrogen desorption curve at 300℃, and c is the cycling curve at 325℃.

[0036] Figure 5 The hydrogen absorption and desorption curves and cycling curves of the hydrogen storage alloy composite material prepared in Example 4 of the present invention are shown, wherein: a is the hydrogen absorption curve at 250℃, b is the hydrogen desorption curve at 300℃, and c is the cycling curve at 325℃.

[0037] Figure 6 The hydrogen absorption and desorption curves and cycling curves of the hydrogen storage alloy composite material prepared in Example 5 of the present invention are shown, wherein: a is the hydrogen absorption curve at 250℃, b is the hydrogen desorption curve at 300℃, and c is the cycling curve at 325℃.

[0038] Figure 7 The hydrogen absorption and desorption curves and cycling curves of the hydrogen storage alloy composite material prepared in Example 6 of the present invention are shown, wherein: a is the hydrogen absorption curve at 250°C, b is the hydrogen desorption curve at 300°C, and c is the cycling curve at 325°C.

[0039] Figure 8 The hydrogen absorption and desorption curves and cycling curves of the hydrogen storage alloy composite material prepared in Comparative Example 1 of this invention are shown, wherein: a is the hydrogen absorption curve at 250℃, b is the hydrogen desorption curve at 300℃, and c is the cycling curve at 325℃.

[0040] Figure 9The hydrogen absorption and desorption curves and cycling curves of the hydrogen storage alloy composite material prepared in Comparative Example 2 of this invention are shown, wherein: a is the hydrogen absorption curve at 250℃, b is the hydrogen desorption curve at 300℃, and c is the cycling curve at 325℃.

[0041] Figure 10 The hydrogen absorption and desorption curves and cycling curves of the hydrogen storage alloy composite material prepared in Comparative Example 3 of this invention are shown, where: a is the hydrogen absorption curve at 250℃, b is the hydrogen desorption curve at 300℃, and c is the cycling curve at 325℃.

[0042] Figure 11 The hydrogen absorption and desorption curves and cycling curves of the hydrogen storage alloy composite material prepared in Comparative Example 4 of this invention are shown, where: a is the hydrogen absorption curve at 250℃, b is the hydrogen desorption curve at 300℃, and c is the cycling curve at 325℃.

[0043] Figure 12 The hydrogen absorption and desorption curves and cycling curves of the hydrogen storage alloy composite material prepared in Comparative Example 5 of this invention are shown, where: a is the hydrogen absorption curve at 250℃, b is the hydrogen desorption curve at 300℃, and c is the cycling curve at 325℃.

[0044] Figure 13 The figures show the hydrogen absorption / desorption curves and cycling curves of the hydrogen storage alloy composite material prepared in Comparative Example 6 of this invention, where: a is the hydrogen absorption curve at 250℃, b is the hydrogen desorption curve at 300℃, and c is the cycling curve at 325℃. Detailed Implementation

[0045] 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.

[0046] 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.

[0047] Example 1

[0048] This embodiment prepares a Sm 1.7 Mg 98.3 The preparation process and steps of the +10wt.%H-Nb2O5 hydrogen storage alloy composite material are as follows:

[0049] S1. Preparation of H-Nb2O5

[0050] S11. Dissolve 1 mol of niobium oxalate and 4 mol of ammonium carbonate in 60 mL of deionized water, stir at 300 rpm for 30 min, and then sonicate for 30 min to obtain the precursor solution.

[0051] S12. The precursor solution was transferred to a polytetrafluoroethylene liner and hydrothermally treated at 180°C for 12 hours. The precipitate was washed with deionized water, centrifuged at 7000 rpm for 5 minutes and washed 3 times. After drying in an 80°C forced-air drying oven for 6 hours, it was calcined in air at 500°C for 2 hours to obtain the Nb2O5 precursor.

[0052] S13. After grinding and mixing 1 mol Nb2O5 precursor with 15 mol NaBH4 in an argon glove box for 30 min, the mixture was placed in an alumina crucible and thermally reduced at 500℃ for 3 h under an argon atmosphere. After washing with deionized water at 7000 rpm for 5 min to remove residual salts, the mixture was freeze-dried at -40℃ for 24 h to obtain H-Nb2O5 powder.

[0053] S2, Preparation of Sm 1.7 Mg 98.3 +10wt.%H-Nb2O5 hydrogen storage alloy composite material

[0054] S21. Under an argon atmosphere, Sm 1.7 Mg 98.3 The alloy powder was mixed with 10 wt.% H-Nb2O5 powder and placed in a sample tube. The mixture was hydrogenated at 400 °C and 4.0 MPa for 12 h to obtain a black powder.

[0055] S22. Under an argon atmosphere, black powder is placed in a stainless steel ball mill jar for ball milling. The ball milling process is as follows: stainless steel balls with a ball-to-material ratio of 40:1 and the material are placed in a ball mill and milled at 400 rpm for 10 cycles. One cycle consists of 10 minutes of milling followed by a 10-minute interval, yielding Sm. 1.7 Mg 98.3 +10wt.%H-Nb2O5 hydrogen storage alloy composite material.

[0056] Examples 2-6

[0057] Examples 2-6 each prepared a hydrogen storage alloy composite material. The preparation process was similar to that of Example 1, except that the parameters were different, as shown in the table below:

[0058]

[0059]

[0060] Comparative Example

[0061] To investigate the influence of different preparation processes on the performance of the product of this invention, the following comparative experiments were conducted. Different hydrogen storage alloys were prepared in the following comparative examples:

[0062] Comparative Example 1

[0063] This comparative example prepares a Sm 1.7 Mg 98.3 The preparation process of the hydrogen storage alloy is as follows:

[0064] (1) Under an argon atmosphere, Sm with a size of 150 μm was... 1.7 Mg 98.3 The alloy powder was placed in a sample tube and hydrogenated at 400℃ and 4MPa for 12h to obtain a black powder.

[0065] (2) Under a protective Ar atmosphere, the black powder was placed in a stainless steel ball mill jar for ball milling. The ball milling process was as follows: stainless steel balls with a ball-to-material ratio of 50:1 and the material were placed in a ball mill and ball milled at 450 rpm for 10 cycles. One cycle consisted of 15 minutes of ball milling followed by a 15-minute interval, to obtain Sm. 1.7 Mg 98.3 Hydrogen storage alloy.

[0066] Comparative Example 2

[0067] This comparative example prepares a Mg+10wt.%Nb2O5 hydrogen storage alloy. The preparation process is similar to that of Example 1, except that step S13 is omitted, and the Sm in step S2 is removed. 1.7 Mg 98.3 Replace all with Mg.

[0068] Comparative Example 3

[0069] This comparative example prepares a Sm 1.7 Mg 98.3 The +10wt.% Nb2O5 hydrogen storage alloy was prepared in a similar manner to Example 1, except that step S13 was omitted.

[0070] Comparative Example 4

[0071] This comparative example prepares a Sm 1.7 Mg 98.3 The +10wt.% H-Nb2O5 hydrogen storage alloy was prepared in a similar manner to that in Example 1, except that step S21 was omitted.

[0072] Comparative Example 5

[0073] This comparative example prepares a Sm 1.7 Mg 98.3The +10wt.% H-Nb2O5 hydrogen storage alloy was prepared in a similar manner to that in Example 1, except that step S22 was omitted.

[0074] Comparative Example 6

[0075] This comparative example prepares a Sm 1.7 Mg 98.3 The +10wt.% H-Nb2O5 hydrogen storage alloy was prepared in a similar manner to that in Example 1, except that in step S21, the hydrogenation temperature was 250℃, the pressure was 2.0MPa, and the time was 12h; in step S22, the ball-to-material ratio during ball milling was 60:1, the ball milling speed was 500rpm, and the ball milling was performed for 15 cycles, with each cycle consisting of 25min of ball milling and a 5min interval.

[0076] Performance testing

[0077] The hydrogen storage alloy composites prepared in Examples 1-6 and Comparative Examples 1-6 were tested for hydrogen absorption performance at 250℃ and 3.0 MPa hydrogen pressure, and for hydrogen desorption performance at 300℃ and 0.001 MPa hydrogen pressure. A 50-cycle hydrogen absorption / desorption performance test was conducted at 325℃, with a hydrogen pressure of 3.0 MPa during absorption and 0.001 MPa during desorption. Specific test results are as follows:

[0078] like Figure 1 Figure 1 shows the hydrogen absorption / desorption curves and cycling curves of the hydrogen storage alloy composite material prepared in Example 1 of this invention. Figure 2 shows the hydrogen absorption curve at 250℃, figure 3 shows the hydrogen desorption curve at 300℃, and figure 4 shows the cycling curve at 325℃. As can be seen from the figures, the hydrogen absorption capacity of this hydrogen storage alloy composite material is 6.157 wt.% within 3600 s at 250℃; and the hydrogen desorption capacity is 5.761 wt.% at 300℃. Its initial hydrogen desorption temperature is 201℃. Furthermore, the hydrogen storage capacity and kinetic performance gradually increase during the initial cycle, and there is no significant capacity decay after 50 cycles, with a dehydrogenation retention rate of 99.2%.

[0079] like Figure 2 The figures show HRTEM images of the hydrogen storage alloy composite material prepared in Example 1 of this invention after complete hydrogen absorption, where a and b are both HRTEM images of Example 1 after complete hydrogen absorption. It can be seen from the figures that... Figure 2 In a, the (220) and (200) crystal planes of MgH2, as well as the (110) and (200) crystal planes of Sm3H7 and NbO, can be observed. This proves that the composite material, after hydrogenation ball milling, forms an Sm3H7 / MgH2 interface that acts as a hydrogen diffusion channel, and that H-Nb2O5 reacts with Mg to generate multivalent catalytic centers in situ. Meanwhile, in Figure 2In step b, further observation of the Nb(110) and MgO(200) crystal planes confirmed the in-situ reaction of H-Nb₂O₅ with Mg. Nanocrystalline MgO provides more hydrogen diffusion channels. Importantly, the Nb / Sm₃H₇ interface was also observed, further demonstrating that hydrogenation ball milling facilitates the formation of a bifunctional Nb / Sm₃H₇ interface. Although Nb-mediated electron transfer induces the spontaneous dissociation of MgH₂, the dehydrogenation barrier of MgH₂ at the Nb interface is high. This is because the energy barriers for H diffusion and H₂ generation are high. On the one hand, the strong hydrogen chemisorption capacity of Nb kinetically hinders hydrogen diffusion and recombination at the interface; on the other hand, the strong interaction between Nb and H leads to the formation of NbH₂, resulting in a decrease in its catalytic activity. When the Nb / Sm₃H₇ interface is formed, hydrogen exhibits low diffusion and bonding energy barriers, which not only promotes the dehydrogenation of MgH₂ but also effectively inhibits the hydrogenation of Nb, thus maintaining its catalytic activity. Simultaneously, Figure 2 The absence of NbH2 crystal planes observed in b further demonstrates that the Nb / Sm3H7 interface inhibits Nb hydrogenation. The bifunctional Nb / Sm3H7 interface not only effectively lowers the energy barrier for MgH2 dehydrogenation but also stabilizes the catalytic activity of Nb by promoting hydrogen diffusion and preventing NbH2 formation.

[0080] like Figure 3 Figure 1 shows the hydrogen absorption / desorption curves and cycling curves of the hydrogen storage alloy composite material prepared in Example 2 of this invention. Figure 2 shows the hydrogen absorption curve at 250℃, the hydrogen desorption curve at 300℃, and the cycling curve at 325℃. As can be seen from the figures, the hydrogen storage alloy composite material absorbs 5.417 wt.% hydrogen at 250℃ and within 3600 s, and desorbs 5.437 wt.% hydrogen at 300℃ and within 3600 s. Its initial hydrogen desorption temperature is 205℃. After 50 cycles of hydrogen absorption / desorption at 325℃, its capacity retention rate is 98.1%.

[0081] like Figure 4 Figure 1 shows the hydrogen absorption / desorption curves and cycling curves of the hydrogen storage alloy composite material prepared in Example 3 of this invention. Figure 2 shows the hydrogen absorption curve at 250℃, figure 3 shows the hydrogen desorption curve at 300℃, and figure 4 shows the cycling curve at 325℃. As can be seen from the figures, the hydrogen storage alloy composite material absorbs 5.282 wt.% hydrogen at 250℃ and within 3600 s, and desorbs 5.124 wt.% hydrogen at 300℃ and within 3600 s. Its initial hydrogen desorption temperature is 210℃. After 50 cycles of hydrogen absorption / desorption at 325℃, its capacity retention rate is 98.8%.

[0082] like Figure 5Figure 1 shows the hydrogen absorption / desorption curves and cycling curves of the hydrogen storage alloy composite material prepared in Example 4 of this invention. Figure 2 shows the hydrogen absorption curve at 250℃, figure 3 shows the hydrogen desorption curve at 300℃, and figure 4 shows the cycling curve at 325℃. As can be seen from the figures, the hydrogen storage alloy composite material absorbs 6.006 wt.% hydrogen at 250℃ and within 3600 s, and desorbs 5.397 wt.% hydrogen at 300℃ and within 3600 s. Its initial hydrogen desorption temperature is 203℃. After 50 cycles of hydrogen absorption / desorption at 325℃, its capacity retention rate is 98.2%.

[0083] like Figure 6 Figure 1 shows the hydrogen absorption / desorption curves and cycling curves of the hydrogen storage alloy composite material prepared in Example 5 of this invention. Figure 2 shows the hydrogen absorption curve at 250℃, figure 3 shows the hydrogen desorption curve at 300℃, and figure 4 shows the cycling curve at 325℃. As can be seen from the figures, the hydrogen storage alloy composite material absorbs 5.916 wt.% hydrogen at 250℃ and within 3600 s, and desorbs 5.623 wt.% hydrogen at 300℃ and within 3600 s. Its initial hydrogen desorption temperature is 208℃. After 50 cycles of hydrogen absorption / desorption at 325℃, its capacity retention rate is 98.5%.

[0084] like Figure 7 Figure 1 shows the hydrogen absorption / desorption curves and cycling curves of the hydrogen storage alloy composite material prepared in Example 6 of this invention. Figure 2 shows the hydrogen absorption curve at 250℃, figure 3 shows the hydrogen desorption curve at 300℃, and figure 4 shows the cycling curve at 325℃. As can be seen from the figures, the hydrogen storage alloy composite material absorbs 5.772 wt.% hydrogen at 250℃ and within 3600 s, and desorbs 5.599 wt.% hydrogen at 300℃ and within 3600 s. Its initial hydrogen desorption temperature is 212℃. After 50 cycles of hydrogen absorption / desorption at 325℃, its capacity retention rate is 98.9%.

[0085] like Figure 8 Figure 1 shows the hydrogen absorption / desorption curves and cycling curves of the hydrogen storage alloy composite material prepared in Comparative Example 1 of this invention. Figure 2 shows the hydrogen absorption curve at 250℃, figure 3 shows the hydrogen desorption curve at 300℃, and figure 4 shows the cycling curve at 325℃. As can be seen from the figures, the hydrogen storage alloy absorbs 6.124 wt.% hydrogen at 250℃ and within 3600 s, and desorbs 4.606 wt.% hydrogen at 300℃ and within 3600 s. Its initial hydrogen desorption temperature is 320℃. After 50 cycles of hydrogen absorption / desorption at 325℃, its capacity retention rate is 71.5%. (Sm...) 1.7 Mg 98.3 In hydrogen storage alloys, the hydrogenation process generates Sm3H7, which acts as a catalyst phase. Its main function is to provide hydrogen diffusion channels and accelerate hydrogen diffusion; it has little effect on weakening the Mg-H transition. Therefore, Sm... 1.7 Mg98.3 The hydrogen desorption rate and capacity of the hydrogen storage alloy are lower than those of the present invention, and the initial hydrogen desorption temperature is higher than that of the present invention. Furthermore, during the cycling process, Sm3H7 is a stable phase and its catalytic activity remains unchanged. However, the agglomeration effect caused by high temperature and long cycling leads to an extension of the hydrogen diffusion distance and a reduction in the number of sites, resulting in a lower capacity retention rate than that of the present invention.

[0086] like Figure 9 Figure 1 shows the hydrogen absorption / desorption curves and cycling curves of the hydrogen storage alloy composite material prepared in Comparative Example 2 of this invention. Figure 2 shows the hydrogen absorption curve at 250℃, the hydrogen desorption curve at 300℃, and the cycling curve at 325℃. As can be seen from the figures, the hydrogen storage alloy composite material absorbs 5.270 wt.% hydrogen at 250℃ and within 3600 s, and desorbs 5.415 wt.% hydrogen at 300℃ and within 3600 s. Its initial hydrogen desorption temperature is 218℃. After 50 cycles of hydrogen absorption / desorption at 325℃, its capacity retention rate is 70.2%. When using the Mg+10 wt.% Nb2O5 hydrogen storage alloy, firstly, the Sm3H7 phase, which serves as a hydrogen diffusion channel, is not formed during hydrogenation, resulting in a high hydrogen diffusion barrier. During cycling, the capacity retention rate is easily reduced due to the agglomeration effect. Secondly, since the Nb2O5 precursor is not thermally reduced, the high-valence Nb... 5+ During the hydrogenation ball milling and circulation process, Mg / MgH2 will undergo a rapid redox reaction to generate a MgO passivation layer that hinders hydrogen diffusion, which will further reduce its capacity retention.

[0087] like Figure 10 Figure 1 shows the hydrogen absorption / desorption curves and cycling curves of the hydrogen storage alloy composite material prepared in Comparative Example 3 of this invention. Figure 2 shows the hydrogen absorption curve at 250℃, figure 3 shows the hydrogen desorption curve at 300℃, and figure 4 shows the cycling curve at 325℃. As can be seen from the figures, the hydrogen storage alloy composite material absorbs 5.539 wt.% hydrogen at 250℃ and within 3600 s, and desorbs 4.842 wt.% hydrogen at 300℃ and within 3600 s. Its initial hydrogen desorption temperature is 220℃. After 50 cycles of hydrogen absorption / desorption at 325℃, its capacity retention rate is 92.5%. (Sm...) 1.7 Mg 98.3 When Nb₂O₅ hydrogen storage alloys are made with +10 wt.% Nb₂O₅, the hydrogenation process generates Sm₃H₇, which acts as a hydrogen diffusion channel, effectively reducing the increase in hydrogen diffusion barrier caused by agglomeration during cycling. However, high-valence Nb 5+ During the hydrogenation ball milling and circulation process, Mg / MgH2 will undergo a rapid redox reaction to generate a MgO passivation layer that hinders hydrogen diffusion, resulting in a lower capacity retention rate in this comparative example compared to that of the present invention.

[0088] like Figure 11Figure 1 shows the hydrogen absorption / desorption curves and cycling curves of the hydrogen storage alloy composite material prepared in Comparative Example 4 of this invention. Figure 2 shows the hydrogen absorption curve at 250℃, figure 3 shows the hydrogen desorption curve at 300℃, and figure 4 shows the cycling curve at 325℃. As can be seen from the figures, the hydrogen storage alloy composite material absorbs approximately 4.597 wt.% hydrogen at 250℃ and 360℃, and desorbs 4.333 wt.% hydrogen at 300℃. Its initial hydrogen desorption temperature is 252℃. After 50 cycles of hydrogen absorption / desorption at 325℃, its capacity retention rate is 65.5%. When Sm 1.7 Mg 98.3 After the alloy powder is mixed with H-Nb2O5 powder, it is directly subjected to high-energy ball milling without hydrogenation. Due to the excellent ductility of the Sm-Mg alloy, the alloy is not broken into micron-sized powder, but instead forms a plate-like structure. This greatly affects the reduction of the particle size of the MgH2 matrix and the uniform distribution of the catalyst, resulting in a decrease in its hydrogen storage capacity and cycle stability.

[0089] like Figure 12 Figure 1 shows the hydrogen absorption / desorption curves and cycling curves of the hydrogen storage alloy composite material prepared in Comparative Example 5 of this invention. Figure 2 shows the hydrogen absorption curve at 250℃, figure 3 shows the hydrogen desorption curve at 300℃, and figure 4 shows the cycling curve at 325℃. As can be seen from the figures, the hydrogen storage alloy composite material absorbs approximately 3.625 wt.% hydrogen at 250℃ and within 3600 s, and the hydrogen desorption capacity at 300℃ is 1.003 wt.%. Its initial hydrogen desorption temperature is 266℃. After 50 cycles of hydrogen absorption / desorption at 325℃, its capacity retention rate is 62.5%. When only hydrogenation is performed without ball milling during the preparation process, due to Sm... 1.7 Mg 98.3 The alloy powder has a large particle size, resulting in poor contact with the catalyst and a limited number of effective catalytic active sites; simultaneously, the large-particle-size Sm... 1.7 Mg 98.3 The alloy powder will lead to a significant increase in the hydrogen diffusion distance, which is extremely detrimental to the activation, hydrogen absorption and desorption, and cycling performance of the composite material, resulting in poor performance.

[0090] like Figure 13Figure 1 shows the hydrogen absorption / desorption curves and cycling curves of the hydrogen storage alloy composite material prepared in Comparative Example 6 of this invention. Figure 2 shows the hydrogen absorption curve at 250℃, figure 3 shows the hydrogen desorption curve at 300℃, and figure 4 shows the cycling curve at 325℃. As can be seen from the figures, the hydrogen storage alloy composite material absorbs approximately 5.385 wt.% hydrogen at 250℃ and within 3600 s, and the hydrogen desorption capacity at 300℃ is 4.725 wt.%. Its initial hydrogen desorption temperature is 228℃. After 50 cycles of hydrogen absorption / desorption at 325℃, its capacity retention rate is 90.5%. When the hydrogenation ball milling parameters are all outside the scope of this invention, the lower hydrogenation temperature and pressure lead to incomplete hydrogenation of the composite material, which still contains Sm5Mg with good ductility. 41 The presence of the Mg phase hinders particle size reduction during subsequent ball milling, easily leading to the formation of a large-particle matrix. Furthermore, excessively high ball milling parameters (ball-to-material ratio, rotational speed, and time) cause cold welding between composite materials during milling, further increasing the matrix particle size. Larger particle sizes impede hydrogen absorption / desorption and diffusion during cycling, ultimately resulting in lower hydrogen storage performance compared to this invention.

[0091] 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 Sm-Mg-based hydrogen storage alloy composite material with added multivalent niobium oxide, characterized in that, Its general chemical formula is Sm x Mg 100-x +10wt.%H-Nb2O5, where x is the atomic ratio, 1.7≤x≤4.

5.

2. The method for preparing a Sm-Mg-based hydrogen storage alloy composite material with added multivalent niobium oxide according to claim 1, characterized in that, Follow these steps in sequence: S1. Preparation of H-Nb2O5 S11. Dissolve niobium oxalate and ammonium carbonate in 60 mL of deionized water, stir at 100-400 rpm for 20-40 min, and then sonicate for 30 min to obtain the precursor solution. S12. The precursor solution was transferred to polytetrafluoroethylene and hydrothermally treated at 180℃ for 12h. The precipitate was washed with deionized water, centrifuged at 7000rpm for 5min and washed 3 times. After drying in an 80℃ forced-air drying oven for 6h, it was calcined in air at 500℃ for 2h to obtain the Nb2O5 precursor. S13. Grind the Nb2O5 precursor and NaBH4 in an argon glove box for 30 min, place them in an alumina crucible, perform thermal reduction under an argon atmosphere, wash with deionized water at 7000 rpm for 5 min to remove residual salts, and freeze-dry at -40℃ for 24 h to obtain H-Nb2O5 powder. S2, Preparation of Sm x Mg 100-x +10wt.%H-Nb2O5 hydrogen storage alloy composite material S21. Under an argon atmosphere, Sm x Mg 100-x The alloy powder was mixed with 10 wt.% H-Nb2O5 powder and placed in a sample tube for hydrogenation to obtain a black powder. S22. Under an argon atmosphere, the black powder was placed in a stainless steel ball mill jar and ball-milled to obtain Sm. x Mg 100-x +10wt.%H-Nb2O5 hydrogen storage alloy composite material.

3. The method for preparing a Sm-Mg-based hydrogen storage alloy composite material with added multivalent niobium oxide according to claim 2, characterized in that, In step S11, the molar ratio of niobium oxalate to ammonium carbonate is 1:(2.5-5.0).

4. The method for preparing a Sm-Mg-based hydrogen storage alloy composite material with added multivalent niobium oxide according to claim 2, characterized in that, In step S13, the molar ratio of the Nb2O5 precursor to NaBH4 is 1:(10-20).

5. The method for preparing a Sm-Mg-based hydrogen storage alloy composite material with added multivalent niobium oxide according to claim 2, characterized in that, In step S13, the temperature during thermal reduction is 400-500℃, and the time is 2-3 hours.

6. The method for preparing a Sm-Mg-based hydrogen storage alloy composite material with added multivalent niobium oxide according to claim 2, characterized in that, In step S21, the hydrogenation temperature is 300-450℃, the pressure is 3-4.5MPa, and the time is 10-12h.

7. The method for preparing a Sm-Mg-based hydrogen storage alloy composite material with added multivalent niobium oxide according to claim 2, characterized in that, In step S22, the ball milling process is as follows: stainless steel balls with a ball-to-material ratio of (30-50):1 and the material are placed in a ball mill and milled at 350-450 rpm for 8-12 cycles. One cycle consists of 10-20 min of milling followed by 10-20 min of rest.

Images