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

Abstract

The application discloses a Sm-Mg-based hydrogen storage alloy composite material added with multi-valence niobium oxide and a preparation method thereof. x Mg 100‑x +10wt.% H-Nb2O5, wherein x is an atomic ratio, 1.7<=x<=4.5; the hydrogen storage alloy composite material is prepared by obtaining H-Nb2O5 powder through a hydrothermal method and a reduction method, and then hydrogenating and ball milling the H-Nb2O5 powder and the Sm-Mg-based hydrogen storage alloy; the preparation method is simple, the process is easy to control, the hydrogen storage alloy composite material prepared by the method generates multi-valence catalytic centers in the hydrogen absorption and release process, enhances the weakening effect on Mg-H bonds, generates nanocrystalline MgO at the same time, avoids capacity attenuation caused by Mg-MgO core-shell structure, and finally constructs a double-function Nb / Sm3H7 interface, which improves the kinetic performance of MgH2 and avoids Nb hydrogenation into NbH2; the initial hydrogen release temperature of the composite material is less than 220 DEG C, and the capacity retention rate is greater than 98% after 50 cycles at 325 DEG C.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of solid-state hydrogen storage materials, and relates to a Sm-Mg-based hydrogen storage alloy composite material added with multi-valence niobium oxide and a preparation method thereof. BACKGROUND

[0002] Hydrogen energy, as a kind of green and sustainable energy, has attracted much attention due to its high energy density, high combustion heat value, cleanliness, zero emission and multi-purpose applicability. However, the lack of safe and efficient hydrogen storage and transportation technology greatly hinders the large-scale utilization of hydrogen energy. At present, there are mainly three methods for hydrogen storage: high-pressure gaseous hydrogen storage, low-temperature liquid hydrogen storage and solid-state hydrogen storage. Compared with the risks of hydrogen leakage and material embrittlement existing in the other two methods, solid-state hydrogen storage can fundamentally realize the safe fixation of hydrogen atoms by forming chemical bonds between hydrogen and hydrogen storage materials to generate metal hydrides.

[0003] Among various hydrogen storage materials, magnesium-based hydrogen storage materials have become the most promising carrier due to their high hydrogen storage density of up to 7.6wt.%, ecological friendliness and high geological abundance. However, the slow kinetics and excessively high thermodynamic stability of magnesium-based hydrogen storage materials have been challenged due to the energy barriers of Mg-H bond breaking, H2 dissociation / recombination and H diffusion. In addition, the gradual growth of Mg / MgH2 phase and the serious particle agglomeration seriously hinder the diffusion of hydrogen, leading to weakened hydrogenation kinetics and reduced capacity. Methods such as catalyst doping, alloying and nanocrystallization can be adopted to improve the above problems. Among them, catalyst doping composite alloying is an effective method to improve the performance of magnesium-based hydrogen storage materials. The introduction of a second phase (such as ReH x phase and Mg2Ni phase, and Re is a rare earth element) can provide hydrogen diffusion channels and accelerate hydrogen diffusion, thereby improving the kinetic performance of magnesium-based hydrogen storage materials. At the same time, trace amounts of nano-MgO can provide hydrogen diffusion channels and also be beneficial to the kinetic performance of magnesium-based hydrogen storage materials, but excessive MgO will form a Mg-MgO core-shell structure, which will reduce the active sites of magnesium-based hydrogen storage materials for hydrogen absorption and desorption and thus exhibit capacity decay. Transition metal-based catalysts have obvious effects on hydrogen dissociation / recombination and Mg-H bond breaking, but some metastable transition metal-based catalysts (TiO2, V2O5 and Nb2O5, etc.) generate excessive MgO to form a Mg-MgO core-shell structure with Mg redox, which leads to capacity decay. At the same time, the hydrogenation of transition metal elements (Ti, V and Nb, etc.) into hydrides leads to the decay of catalytic activity. Therefore, how to maintain the catalytic activity of transition metal-based catalysts while avoiding the formation of a Mg-MgO core-shell structure, that is, to ensure the cycle stability of magnesium-based hydrogen storage materials on the basis of improving the kinetic performance and reducing the dehydrogenation temperature of magnesium-based hydrogen storage materials is a hot spot of current research.

[0004] Based on this, the present application is proposed. SUMMARY

[0005] In order to solve the above technical problems, the present application aims to provide a Sm-Mg-based hydrogen storage alloy composite material added with multi-valence niobium oxide and a preparation method thereof, which has a general chemical composition formula of Sm x Mg 100-x +10wt.% H-Nb2O5, wherein x is an atomic ratio, 1.7<=x<=4.5; the hydrogen storage alloy composite material is prepared by obtaining H-Nb2O5 powder through a hydrothermal method and a reduction method, and then hydrogenating and ball-milling the H-Nb2O5 powder together with the Sm-Mg-based hydrogen storage alloy; the preparation method is simple and the process is easy to control; and the hydrogen storage alloy composite material prepared by the method generates multi-valence catalytic centers (Nb 5+ , Nb 4+ , Nb 2+ , Nb) in the hydrogen absorption and release process, enhances the weakening effect on Mg-H bonds, generates nanocrystalline MgO at the same time, avoids capacity attenuation caused by Mg-MgO core-shell structure, and finally constructs a double-function Nb / Sm3H7 interface, which improves the kinetic performance of MgH2 and avoids Nb hydrogenation into NbH2, and maintains the catalytic activity; the initial hydrogen release temperature of the composite material is less than 220 DEG C, and the capacity retention rate is greater than 98% after 50 cycles at 325 DEG C.

[0006] To achieve the above object, the technical scheme adopted by the present application is as follows:

[0007] The Sm-Mg-based hydrogen storage alloy composite material added with multi-valence niobium oxide has a general chemical composition formula of Sm x Mg 100-x +10wt.% H-Nb2O5, wherein x is an atomic ratio, 1.7<=x<=4.5.

[0008] The present application also provides a preparation method of the Sm-Mg-based hydrogen storage alloy composite material added with multi-valence niobium oxide, which is sequentially performed according to the following steps:

[0009] S1, preparing H-Nb2O5

[0010] S11, dissolving niobium oxalate and ammonium carbonate in 60 mL of deionized water, stirring at 100-400 rpm for 20-40 min, and then ultrasonic treating for 30 min to obtain a precursor solution;

[0011] S12, transferring the precursor solution into a polytetrafluoroethylene liner, hydrothermally treating at 180 DEG C for 12 h, washing the precipitate with deionized water, centrifuging at 7000 rpm for 5 min for 3 times, drying in a 80 DEG C air drying oven for 6 h, and then calcining in air at 500 DEG C for 2 h to obtain a Nb2O5 precursor;

[0012] S13, grinding Nb2O5 precursor and NaBH4 in an argon glove box for 30 min, putting it into an alumina crucible, heat-reducing under an argon atmosphere, washing and removing residual salts by centrifugation at 7000 rpm for 5 min with deionized water, and freeze-drying at -40℃ for 24 h to obtain H-Nb2O5 powder;

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

[0014] S21, placing Sm x Mg 100-x alloy powder and 10wt.% H-Nb2O5 powder in a sample tube for hydrogenation to obtain black powder;

[0015] S22, placing the black powder in a stainless steel ball mill jar for ball milling under an argon atmosphere 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 application, in step S11, the molar ratio of the niobium oxalate to the ammonium carbonate is 1: (2.5-5.0).

[0017] As another limitation of the preparation method of the application, 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 application, in step S13, the temperature during heat reduction is 400-500℃, and the time is 2-3h.

[0019] In the application, the heat reduction process is crucial and will affect the valence state of Nb in the H-Nb2O5 catalyst and the morphology of the nanosheet clusters. When the heat reduction temperature is 400-500℃ and the reduction time is 2-3h, the redox rate of NaBH4 and the Nb2O5 precursor will be affected, so that the H-Nb2O5 not only maintains the state of Nb 5+ and Nb 4+ , improves the catalytic activity, but also maintains the nanosheet morphology without agglomeration into blocks, increases the active sites, and further improves the catalytic performance of H-Nb2O5; when the reduction temperature is less than 400℃ and the reduction time is less than 2h, NaBH4 is difficult to oxidize and reduce with the Nb2O5 precursor, so that the catalyst is still in the state of Nb 5+The existence thereof reduces the catalytic performance; when the reduction temperature is greater than 500 DEG C and the reduction time is greater than 3h, a severe redox reaction between NaBH4 and the Nb2O5 precursor occurs, thereby causing the Nb2O5 precursor to collapse and agglomerate into a fast shape, reducing the catalytic active site, and further reducing the catalytic performance of the catalyst.

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

[0021] In the application, the temperature, pressure and hydrogenation time during hydrogenation are crucial and will affect the Sm x Mg 100-x Whether complete hydrogenation decomposition into Sm3H7 and MgH2 and the catalytic activity conversion of H-Nb2O5 occur; when the hydrogenation temperature is 300-450 DEG C and the pressure is 3-4.5 MPa, Sm x Mg 100-x Complete hydrogenation decomposition into Sm3H7 and MgH2, and the generation of nanocrystalline MgO from H-Nb2O5 during reduction, thereby making Sm x Mg 100-x +10wt.%H-Nb2O5 composite hydrogen storage material is fully ball milled to generate a micron-sized MgH2 matrix during subsequent ball milling, while avoiding the hydrogen storage capacity attenuation caused by the Mg-MgO core-shell structure; when the temperature is less than 300 DEG C and the pressure is less than 3 MPa, Sm x Mg 100-x Cannot be completely hydrogenated and decomposed into Sm3H7 and MgH2, and still retains Sm5Mg 41 Phase and Mg phase, and because the Sm5Mg 41 Phase and Mg phase have high ductility, thereby causing Sm x Mg 100-x +10wt.%H-Nb2O5 composite hydrogen storage material has a large MgH2 matrix particle size, while its hydrogen storage capacity attenuates; when the temperature is greater than 450 DEG C and the pressure is greater than 4.5 MPa, a severe reaction between H-Nb2O5 and Mg occurs, generating a Mg-MgO core-shell structure, thereby causing its hydrogen storage capacity to significantly attenuate. Hydrogenation for 10-12h is to promote Sm x Mg 100-x Complete hydrogenation decomposition while ensuring slow reduction of H-Nb2O5 to generate nanocrystalline MgO, and avoiding the generation of a 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 a whole in which each step is closely related and mutually influential, and together they 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 ball milled at 400 rpm for 10 cycles. One cycle consists of 10 minutes of ball 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 that in 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 +10 wt.%H-Nb2O5, where x is the atomic ratio, 1.7≤x≤4.5; The preparation method of the Sm-Mg-based hydrogen storage alloy composite material with added multivalent niobium oxide is carried out in the following order: 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 12 h. The precipitate was washed with deionized water, centrifuged at 7000 rpm for 5 min and washed 3 times. After drying in an oven at 80℃ for 6 h, it was calcined in air at 500℃ for 2 h 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, and perform thermal reduction under an argon atmosphere. The temperature of the thermal reduction is 400-500℃ and the time is 2-3 h. After washing with deionized water at 7000 rpm for 5 min to remove residual salts, freeze-dry at -40℃ for 24 h to obtain H-Nb2O5 powder. S2, Preparation of Sm x Mg 100-x +10 wt.% 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. The hydrogenation temperature was 300-450℃, the pressure was 3-4.5 MPa, and the time was 10-12 h, resulting in a black powder. S22. Under an argon atmosphere, the 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 (30-50):1 and the material are placed in a ball mill and ball milled at 350-450 rpm for 8-12 cycles. One cycle consists of ball milling for 10-20 minutes followed by a 10-20 minute interval, to obtain Sm. x Mg 100-x +10 wt.% H-Nb2O5 hydrogen storage alloy composite material.

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

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

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