La-containing high-entropy alloy catalyst, preparation method and application thereof

Abstract

This invention discloses a La-containing high-entropy alloy, which is smelted using Fe, Co, Ni, Zr, V, and La metals as raw materials. The resulting high-entropy alloy simultaneously contains LaNi phase, ZrNi2 phase, and V solid solution phase; the particle size is 100-200 mesh; the molar ratio of Fe, Co, Ni, Zr, V, and La is 19:19:19:19:19:5, yielding the La-containing high-entropy alloy FCNZVs-La. A method for preparing magnesium hydride hydrogen storage material based on the La-containing high-entropy alloy is also disclosed, involving ball milling of FCNZVs-La and MgH2. The resulting magnesium hydride hydrogen storage material based on a La-containing high-entropy alloy, when applied in the field of hydrogen storage, showed that the initial hydrogen release temperature dropped to 188.92–191.21 °C, and the hydrogen release amount reached 6.64–6.65 wt.%; under the conditions of hydrogen pressure of 2.5 MPa, hydrogen absorption temperature of 175 °C, and hydrogen absorption time of 4 min, the hydrogen absorption amount was 4.95–5.02 wt.%.

Description

Technical Field

[0001] Magnesium hydride (MgH2) possesses advantages such as high hydrogen storage capacity, abundant resources, and low cost. However, MgH2 suffers from high thermodynamic stability, slow hydrogen desorption kinetics, and high operating temperatures. Current solutions involve adding catalysts to improve the hydrogen storage performance of MgH2. Alloy catalysts exhibit good electronic conductivity and synergistic catalytic effects between metal elements. Among them, FeCoNi-based transition metal alloys also feature high solid solubility among their components and abundant catalytic active sites. For example, existing literature 1 (Singh S, Bhatnagar A, Shukla V, et al. Ternary transition metal alloy FeCoNi nanoparticles on graphene as new catalyst for hydrogen sorption in MgH2[J]. international journal of hydrogen energy, 2020, 45(1): 774-786.) loads FeCoNi nanoparticles onto the surface of graphene, achieving a significant reduction in the initial hydrogen desorption temperature of pure ball-milled MgH2 from 355℃ to approximately 280℃. Furthermore, it absorbs 6.01 wt.% hydrogen within 1.65 minutes, and after 24 cycles, the capacity only decreases from 6.26 wt.% to 6.24 wt.%. However, since the FeCoNi ternary alloy system belongs to the category of low-entropy alloys with a mixing ratio less than 1.5R, the atomic arrangement and electronic structure tend to be ordered, resulting in a low density of surface catalytic active sites and ultimately poor catalytic performance.

[0002] The most direct way to solve the technical problems of low-entropy alloys is to use high-entropy alloys as catalysts. The basic principle of high-entropy alloys is that, since high-entropy alloys contain five or more principal elements, they can achieve a high mixing entropy effect, thereby suppressing the formation of intermetallic compounds and promoting the formation of solid solution phases. At the same time, the resulting lattice distortion effect can form a large number of defects such as dislocations and vacancies inside the alloy, significantly increasing the density of catalytic active sites. For example, existing literature 2 (Wan H, Yang X, Zhou S, et al. Enhancing hydrogen storage properties of MgH2 using FeCoNiCrMn high entropy alloy catalysts[J]. Journal of Materials Science & Technology, 2023, 149: 88-98.) uses vacuum melting combined with mechanical crushing to prepare FeCoNiCrMn pentagonal high entropy alloy powder, achieving the technical effect of reducing the dehydrogenation activation energy of MgH2 from 151.9 kJ / mol to 90.2 kJ / mol, and releasing 5.6 wt.% hydrogen gas within 10 minutes at 280℃ and absorbing 5.5 wt.% hydrogen gas within 0.5 minutes at 150℃. However, the main elements used in this technical solution, Cr, Mn, Fe, Co, and Ni, are all adjacent transition metal elements in the fourth period. Therefore, they have the characteristic of extremely small differences in atomic radius, that is, low atomic size mismatch, resulting in a lattice distortion degree of only 3.74%.

[0003] A common method to address the issue of small differences in atomic radii is to introduce rare earth elements with larger atomic radii to enhance lattice distortion. Among rare earth elements, La has a much larger atomic radius than transition metals such as Fe, Co, and Ni, and it also has the characteristic of forming the LaNi active phase with Ni. For example, existing literature 3 (Jiang Y, Liu Y, Yue M, et al. Pulsedelectrodeposited rare earth medium-entropy amorphous alloys for catalyzing MgH2 for solid-state hydrogen storage[J]. Journal of Energy Storage, 2025,107: 114956.) prepared FeCoNiLa medium-entropy amorphous alloys using pulsed electrodeposition, achieving a significant reduction in the dehydrogenation temperature of MgH2 from 360.0℃ to 281.6℃, a decrease in the dehydrogenation activation energy from 151.90 kJ / mol to 116.06 kJ / mol, and the release of 6.50 wt.% hydrogen within 5 minutes at 325℃, with a capacity retention rate as high as 98% after 20 cycles. The reason why this technical solution improves kinetic performance and cycle stability is that the introduction of La can not only increase the degree of lattice distortion, but also adjust the electronic structure of Fe, Co, and Ni, enhance the electronic interaction between transition metals, and ultimately achieve a significant improvement in catalytic activity. However, this technical solution only has four main elements, and the resulting alloy is a medium-entropy system. Therefore, it cannot achieve the technical effect of a high-entropy alloy.

[0004] Existing literature 4 (Feng DC, Li H, Li DC, et al. Enhanced hydrogen storage properties of MgH2 catalyzed by TiVCrFeNi high entropy alloy[J]. Journal of Alloys and Compounds, 2025, 1043: 184150.) shows that after introducing MgH2 into TiVCrFeNi, the initial hydrogen desorption temperature decreased to 455 K, the dehydrogenation activation energy decreased to 71.49 kJ / mol, and the hydrogen absorption rate increased by 65 times at 533 K. The basic principle of this technical solution is that V element has the conventional function of providing multivalent electronic structures to promote the dissociation of hydrogen molecules; however, Zr element not only has the conventional function of increasing lattice distortion and generating more dislocations and defects due to its large atomic radius, but also has the function of destroying the compactness of the oxide layer on the alloy surface and increasing the density of catalytic active sites. However, this technical solution only has two main elements, and the resulting alloy is a low-entropy system. Therefore, it cannot achieve the technical effect of a high-entropy alloy.

[0005] To simultaneously achieve the technical effects of high-entropy alloys and Zr doping, the most direct solution is to prepare Zr-containing high-entropy alloys. However, according to existing literature 5 (Qi W, Wang W, Yang X, et al. Effect of Zr onphase separation, mechanical and corrosion behavior of heterogeneous CoCrFeNiZrx high-entropy alloy[J]. Journal of Materials Science & Technology,2022, 109: 76-85.), the Zr content significantly affects the performance of CoCrFeNiZrx alloys. X The microstructure and mechanical properties of high-entropy alloys are significantly affected, for the following reasons:

[0006] Since the atomic radius of Zr is significantly larger than that of Fe, Co, and Ni, increasing the Zr content will lead to the precipitation of hard and brittle intermetallic compounds and a transformation of the solid solution structure. At the same time, the excessive Zr will segregate at the grain boundaries during solidification, forming a continuous network of brittle intermetallic phases. All of the above reasons together lead to severe local stress concentration in the alloy, which in turn leads to brittle fracture along the grain boundaries under the action of cooling thermal stress.

[0007] At the same time, there is a mismatch between the atomic radius of V and the matrix. Furthermore, due to the strong affinity of V for oxygen, under high-purity arc melting conditions, trace amounts of residual oxygen will preferentially react with V, resulting in the formation of vanadium oxide particles inside the alloy. A loose interface region exists around the vanadium oxide particles, which ultimately forms the initiation source of microcracks.

[0008] Although the combined effect of Zr and V atoms can increase the degree of lattice distortion, it also leads to inconsistent shrinkage in different regions during alloy solidification, causing a rapid accumulation of internal stress and ultimately resulting in the alloy ingot cracking.

[0009] As can be seen from the existing literature, it is impossible to obtain high-entropy alloys containing Zr and V using conventional methods. Summary of the Invention

[0010] The purpose of this invention is to provide a La-containing high-entropy alloy catalyst, its preparation method, and its application. To achieve this objective, the basic principle of this invention is to use FeCoNiZrV as the matrix alloy and introduce La metal for doping modification. In addition to the conventional effect of significantly increasing the lattice distortion and mixing entropy of FeCoNiZrV, La can form the LaNi phase with Ni, refine the grains, effectively reduce the hot cracking force of the alloy, enhance the alloy's feeding ability (i.e., the alloy's stability), and ultimately improve the safety during alloy smelting.

[0011] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:

[0012] A high-entropy alloy containing La is obtained by smelting Fe metal, Co metal, Ni metal, Zr metal, V metal and La metal as raw materials. The resulting high-entropy alloy simultaneously contains LaNi phase, ZrNi2 phase and V solid solution phase; the particle size is 100-200 mesh.

[0013] A method for preparing a La-containing high-entropy alloy involves melting Fe, Co, Ni, Zr, V, and La in a molar ratio of 19:19:19:19:19:5, with an additional 6.059 wt.% of La being lost upon burning. First, Fe, Co, Ni, Zr, V, and La metals are ultrasonically cleaned. Then, they are subjected to arc melting. After melting, the resulting alloy is cooled in the furnace to obtain an alloy ingot. The ingot is then ground, crushed, milled, and sieved to obtain the La-containing high-entropy alloy FCNZVs-La.

[0014] The ultrasonic method involves using ethanol as the cleaning solution and a cleaning time of 30 minutes; the sieve particle size is 200 mesh.

[0015] The conditions for the electric arc melting are a vacuum degree of 2×10⁻⁶. -3 Arc melting is carried out under the following conditions: Pa and argon gas pressure of 0.05 MPa are used as protective gas, and the number of inversions is 5. The specific method of arc melting is as follows: Fe metal, Co metal and Ni metal are melted under the condition of current intensity of 100 A. After Fe metal, Co metal and Ni metal are completely melted, Zr metal, V metal and La metal are added in sequence under the condition of current intensity of 200 A and melted until completely melted.

[0016] A method for preparing magnesium hydride hydrogen storage material based on a La-containing high-entropy alloy is disclosed. The method involves ball milling at a mass ratio of FCNZVs-La to MgH2 of 10:90, a ball-to-material ratio of 80:1, a ball milling speed of 400 rpm, a ball milling time of 18 h, and specific ball milling intervals to obtain the La-containing high-entropy alloy-based magnesium hydride hydrogen storage material MgH2-FCNZVs-La. The ball milling interval is defined as follows: after each 12 min of ball milling, the milling is paused for 6 min.

[0017] The obtained magnesium hydride hydrogen storage material based on La-containing high-entropy alloy, when applied in the field of hydrogen storage, shows that when the catalyst doping amount is 10 wt.%, the initial hydrogen release temperature drops to 188.92-191.21 ℃, and the hydrogen release amount reaches 6.64-6.65 wt.%; under the conditions of dehydrogenation temperature of 300℃ and dehydrogenation time of 7 min, the hydrogen release amount is 5.36-5.38 wt.%; and under the conditions of hydrogen pressure of 2.5 MPa, hydrogen absorption temperature of 175℃, and hydrogen absorption time of 4 min, the hydrogen absorption amount is 4.95-5.02 wt.%.

[0018] The technical effects of this invention have been tested and verified:

[0019] ICP testing showed that FCNZVs-La contains Fe, Co, Ni, Zr, V, and La elements, with a mixing entropy of 1.67 R. The test results indicate that FCNZVs-La is a high-entropy alloy.

[0020] XRD, EDS and SEM results show that FCNZVs-La simultaneously contains LaNi phase, ZrNi2 phase and V solid solution phase.

[0021] Thermodynamic tests on dehydrogenation showed that the initial hydrogen release temperature was 188.92-191.21℃. At a test temperature of 300℃, the total hydrogen release reached 6.01-6.04 wt.%, which is 87.87-88.30% of the theoretical maximum hydrogen release of 6.84 wt.%.

[0022] Dehydrogenation kinetics tests showed that, under the conditions of a dehydrogenation temperature of 300℃ and a dehydrogenation time of 7 min, the hydrogen release was 5.36-5.383 wt.%.

[0023] The dehydrogenation kinetics test results show that under the conditions of hydrogen pressure of 2.5 MPa, hydrogen absorption temperature of 175℃, and hydrogen absorption time of 4 min, the hydrogen absorption amount is 4.95-5.02 wt.%.

[0024] Therefore, the present invention has the following advantages over the prior art:

[0025] 1. This invention is the first to apply FeCoNiZrVLa high-entropy alloy as a catalyst to the MgH2 hydrogen storage system. By utilizing the large atomic radius of La, the degree of lattice distortion is increased from 10.4% to 13.3%, which significantly increases the density of surface catalytic active sites.

[0026] 2. The addition of La in this invention prevents high-entropy alloys that would otherwise explode from exploding, thus improving safety.

[0027] 3. The method used to prepare the La-containing high-entropy alloy according to the present invention only requires trace amounts of La metal, and has the advantages of low cost, simple preparation process, controllable reaction and easy large-scale preparation. Attached Figure Description

[0028] Figure 1 The images show the smelted alloy ingots of FCNZVs-La and FCNZVs in Example 1 and Comparative Example 1;

[0029] Figure 2 The XRD patterns of FCNZVs-La and FCNZVs in Example 1 and Comparative Example 1 are shown.

[0030] Figure 3 The SEM image and EDS energy spectrum of FCNZVs-La in Example 1 are shown.

[0031] Figure 4 The temperature-induced dehydrogenation curves of pure magnesium hydride are shown for Example 1 and Comparative Examples 1, 2, 3, and 4.

[0032] Figure 5 The isothermal dehydrogenation curve of MgH2-FCNZVs-La-10 prepared in Example 1 is shown.

[0033] Figure 6 The isothermal hydrogen absorption curve of MgH2-FCNZVs-La-10 prepared in Example 1 is shown.

[0034] Figure 7 Isothermal dehydrogenation curve of pure magnesium hydride;

[0035] Figure 8 Isothermal hydrogen absorption curve of pure magnesium hydride;

[0036] Figure 9 The figure shows the dehydrogenation activation energy of MgH2-FCNZVs-La-10 prepared in Example 1.

[0037] Figure 10 The figure shows the fitting of the dehydrogenation activation energy of pure magnesium hydride. Detailed Implementation

[0038] 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.

[0039] Example 1

[0040] A method for preparing a La-containing high-entropy alloy includes the following steps: Smelting with Fe, Co, Ni, Zr, V, and La in a molar ratio of 19:19:19:19:19:5, with an additional 6.059 wt.% loss on ignition for La; firstly, ultrasonically cleaning 7.928 g Fe metal, 8.366 g Co metal, 8.332 g Ni metal, 12.950 g Zr metal, 7.231 g V metal, and 5.188 g La metal using ethanol as the cleaning solution for 30 min; then, under a vacuum of 2×10⁻⁶... -3 With Pa and argon gas pressure of 0.05 MPa as the protective gas, the electric arc melting was carried out under the condition of 5 inversions. After the melting was completed, the resulting alloy was cooled with the furnace to obtain an alloy ingot. The resulting alloy ingot was then ground, crushed, pulverized and sieved to obtain a La-containing high-entropy alloy, abbreviated as FCNZVs-La.

[0041] The method of electric arc melting is as follows: first, Fe metal, Co metal and Ni metal are melted under a current intensity of 100 A. After the Fe metal, Co metal and Ni metal are completely melted, Zr metal, V metal and La metal are added in sequence under a current intensity of 200 A and melted until completely melted.

[0042] The particle size sieved is 200 mesh.

[0043] To prove that the composition of FCNZVs-La meets the requirements of a high-entropy alloy, ICP testing was performed. The test results are shown in Table 1. FCNZVs-La contains Fe, Co, Ni, Zr, V, and La elements, with a mixing entropy of 1.67 R. The test results indicate that FCNZVs-La is a high-entropy alloy.

[0044] Table 1. ICP test results of FCNZVs-La alloy

[0045] To verify that La doping enhances the feeding performance of the alloy, specifically the stability of FCNZVs-La, macroscopic tests were conducted. The test results are as follows: Figure 1 As shown, FCNZVs-La can yield a complete ingot.

[0046] To verify the crystal structure of FCNZVs-La, XRD tests were performed. The test results are as follows: Figure 2 As shown, FCNZVs-La contains both LaNi and ZrNi2 phases, but no characteristic peaks for V related to Fe and Co elements were detected.

[0047] Therefore, to further verify the phase composition of FCNZV-La, EDS and SEM tests were performed. The test results are as follows: Figure 2 FCNZVs-La contains not only La, Ni, and Zr elements, but also Fe, Co, and V elements;

[0048] Furthermore, combining the XRD and SEM test results, it can be seen that the white part of FCNZVs-La is the LaNi phase, the black part is the solid solution phase of V, and the gray part is the ZrNi2 phase.

[0049] A magnesium hydride hydrogen storage material based on a La-containing high-entropy alloy includes the following steps: ball milling is performed with a mass ratio of FCNZVs-La to MgH2 of 10:90, a ball-to-material ratio of 80:1, a ball milling speed of 400 rpm, a ball milling time of 18 h, and a ball milling interval, to obtain a magnesium hydride hydrogen storage material based on a La-containing high-entropy alloy, abbreviated as MgH2-FCNZVs-La. Specifically, the MgH2-FCNZVs-La obtained in Example 1 is named MgH2-FCNZVs-La-10 because the content of FCNZVs-La is 10 wt.%.

[0050] The ball milling interval is defined as follows: after each ball milling session of 12 minutes, the ball milling is paused for 6 minutes.

[0051] To demonstrate the dehydrogenation thermodynamic performance of FCNZVs-La as a catalyst, temperature-increasing dehydrogenation tests were conducted on MgH2-FCNZVs-La-10 and pure magnesium hydride.

[0052] The results of the temperature-induced dehydrogenation test of pure magnesium hydride are as follows: Figure 4As shown, the initial hydrogen release temperature was 273.36℃; when the test temperature was 300℃, the hydrogen release was only 0.11 wt.%, which only reached 1.45% of the theoretical maximum hydrogen release of 7.6 wt.%, that is, the hydrogen release rate was 1.45%.

[0053] The results of the MgH2-FCNZVs-La-10 temperature-induced dehydrogenation test are as follows: Figure 4 As shown, the initial hydrogen release temperature is 188.92-191.21℃; when the test temperature is 300℃, the hydrogen release is 6.01-6.04 wt.%, reaching 87.87-88.30% of the theoretical maximum hydrogen release of 6.84 wt.%, that is, the hydrogen release rate reaches 87.87%.

[0054] The results of the temperature-induced dehydrogenation test show that adding FCNZV-La catalyst to magnesium hydride can significantly reduce the initial hydrogen release temperature and significantly increase the hydrogen release rate.

[0055] To demonstrate the hydrogen absorption and dehydrogenation kinetics performance of FCNZVs-La as a catalyst, isothermal dehydrogenation and isothermal hydrogen absorption tests were conducted on MgH2-FCNZVs-La-10 and pure magnesium hydride.

[0056] The results of the isothermal dehydrogenation test of pure magnesium hydride are as follows: Figure 7 As shown, under the conditions of a dehydrogenation temperature of 300℃ and a dehydrogenation time of 30 min, the hydrogen release was 2.05 wt.%.

[0057] The results of the isothermal dehydrogenation test of MgH2-FCNZVs-La-10 are as follows: Figure 5 As shown, under the conditions of a dehydrogenation temperature of 300℃ and a dehydrogenation time of 7 min, the hydrogen release was 5.36-5.383 wt.%.

[0058] The results of the isothermal hydrogen absorption test of pure magnesium hydride are as follows: Figure 8 As shown, under the conditions of hydrogen pressure of 2.5 MPa, hydrogen absorption temperature of 175℃, and hydrogen absorption time of 4 min, the hydrogen absorption rate was 0.297 wt.%.

[0059] The results of the isothermal hydrogen adsorption test of MgH2-FCNZVs-La-10 are as follows: Figure 6 As shown, under the conditions of hydrogen pressure of 2.5 MPa, hydrogen absorption temperature of 175℃, and hydrogen absorption time of 6 min, the hydrogen absorption amount is 4.95-5.02 wt.%.

[0060] Isothermal dehydrogenation and isothermal hydrogen absorption test results show that adding FCNZV-La as a catalyst can significantly improve the dehydrogenation and hydrogen absorption kinetics of magnesium hydride.

[0061] To demonstrate the effect of La doping on the performance of FCNZV as a catalyst for magnesium hydride, Comparative Example 1 is provided, which is an alloy catalyst prepared without La doping.

[0062] Comparative Example 1

[0063] A method for preparing an undoped La alloy, the steps of which are the same as those in Example 1 unless otherwise specified, are different in that: La is not added, and the molar ratio of Fe, Co, Ni, Zr and V is 1:1:1:1:1, which is abbreviated as FCNZV; further, the resulting magnesium hydride hydrogen storage material is abbreviated as MgH2-FCNZVs-10.

[0064] To demonstrate that doping with Zr and V elements causes the alloy ingot to crack, i.e., the instability of FCNZVs-La, macroscopic tests were conducted. The test results are as follows: Figure 1 As shown in document 5, FCNZVs exhibit ingot cracking during solidification.

[0065] To verify the crystal structure of FCNZV, XRD tests were performed. The test results are as follows: Figure 1 As shown, FCNZV contains only the ZrNi2 phase. Since it is not doped with La, the characteristic peaks of the LaNi phase are not present.

[0066] To demonstrate the thermodynamic performance of FCNZV as a catalyst for dehydrogenation, a temperature-increased dehydrogenation test was conducted on MgH2-FCNZVs-10. The test results are as follows: Figure 4 As shown, the initial hydrogen release temperature of MgH2-FCNZVs-10 is 196.28℃. When the test temperature is 300℃, the hydrogen release amount is 4.36 wt.%, which reaches 63.74% of the theoretical maximum hydrogen release amount of 6.84 wt.%, that is, the hydrogen release rate is 63.74%.

[0067] Compared with pure magnesium hydride, it can be seen that although adding FCNZV as a catalyst can also significantly reduce the initial hydrogen desorption temperature, further comparison with Example 1 shows that doping with La can further significantly increase the hydrogen desorption rate at 300°C, with an increase of 31.169%.

[0068] To further demonstrate the effect of FCNZVs-La doping on the performance of magnesium hydride, Comparative Examples 2, 3, and 4 are provided, with magnesium hydride hydrogen storage materials having FCNZVs-La doping amounts of 5 wt.%, 7 wt.%, and 12 wt.%, respectively.

[0069] Comparative Example 2

[0070] A method for preparing a magnesium hydride hydrogen storage material with an FCNZVs-La doping amount of 5 wt.% is provided. The steps not specifically described are the same as those in Example 1, except that the mass ratio of FCNZVs-La to MgH2 is 5:95, and the resulting MgH2-FCNZV-La is named MgH2-FCNZVs-La-5.

[0071] To demonstrate the thermodynamic performance of MgH2-FCNZVs-La-5 as a catalyst for dehydrogenation, a temperature-increasing dehydrogenation test was conducted on MgH2-FCNZVs-La-5. The test results are as follows: Figure 4 As shown, the initial hydrogen release temperature of MgH2-FCNZVs-5 is 199.37℃; when the test temperature is 300℃, the hydrogen release is 3.21 wt.%, which reaches 44.46% of the theoretical maximum hydrogen release of 7.22 wt.%, that is, the hydrogen release rate is 44.46%.

[0072] Compared with Comparative Example 1, it can be seen that when the doping amount of FCNZVs-La is too small, it leads to an increase in the initial hydrogen desorption temperature and a decrease in the hydrogen desorption rate.

[0073] Comparative Example 3

[0074] A method for preparing a magnesium hydride hydrogen storage material with an FCNZVs-La doping amount of 7 wt.% is provided. The steps not specifically described are the same as those in Example 1, except that the mass ratio of FCNZVs-La to MgH2 is 7:93, and the resulting MgH2-FCNZV-La is named MgH2-FCNZVs-La-7.

[0075] To demonstrate the thermodynamic performance of MgH2-FCNZVs-La-7 as a catalyst for dehydrogenation, a temperature-increasing dehydrogenation test was conducted on MgH2-FCNZVs-La-7. The test results are as follows: Figure 4 As shown, the initial hydrogen release temperature of MgH2-FCNZVs-7 is 195.41℃; when the test temperature is 300℃, the hydrogen release is 6.1 wt.%, which reaches 86.3% of the theoretical maximum hydrogen release of 7.068 wt.%, that is, the hydrogen release rate is 86.3%.

[0076] Compared with Comparative Example 2, it can be seen that although slightly increasing the doping amount of FCNZVs-La can only slightly reduce the initial hydrogen desorption temperature, it can significantly improve the hydrogen desorption rate, exceeding that of Comparative Example 1 without La doping.

[0077] Comparative Example 4

[0078] A method for preparing a magnesium hydride hydrogen storage material with an FCNZVs-La doping amount of 12 wt.% is provided. The steps not specifically described are the same as those in Example 1, except that the mass ratio of FCNZVs-La to MgH2 is 12:88, and the resulting MgH2-FCNZVs-La is named MgH2-FCNZVs-La-12.

[0079] To demonstrate the thermodynamic performance of MgH2-FCNZVs-La-12 as a catalyst for dehydrogenation, a temperature-increasing dehydrogenation test was conducted on MgH2-FCNZVs-La-12. The test results are as follows: Figure 4 As shown, the initial hydrogen release temperature of MgH2-FCNZVs-12 is 189.91℃; when the test temperature is 300℃, the hydrogen release is 5.734 wt.%, which reaches 85.736% of the theoretical maximum hydrogen release of 6.688 wt.%, that is, the hydrogen release rate is 85.736%.

[0080] Compared with Example 1, it can be seen that when the doping amount of FCNZVs-La is too high, although the initial hydrogen release temperature can be further reduced, the total hydrogen release will decrease.

Claims

1. A La-containing high-entropy alloy, characterized in that: The high-entropy alloy is obtained by smelting Fe metal, Co metal, Ni metal, Zr metal, V metal and La metal as raw materials, and simultaneously contains LaNi phase, ZrNi2 phase and V solid solution phase; the particle size is 100-200 mesh.

2. A method for preparing a La-containing high-entropy alloy, characterized by: The alloy was smelted with Fe, Co, Ni, Zr, V and La in a molar ratio of 19:19:19:19:19:5, with an additional 6.059 wt.% loss of La due to burn-off. First, Fe, Co, Ni, Zr, V and La metals were ultrasonically cleaned. Then, they were smelted by electric arc. After smelting, the resulting alloy was cooled in the furnace to obtain an alloy ingot. The resulting alloy ingot was then ground, crushed, milled and sieved to obtain the La-containing high-entropy alloy FCNZVs-La.

3. The preparation method according to claim 2, characterized in that: The ultrasonic method involves using ethanol as the cleaning solution and cleaning for 30 minutes. The particle size sieved is 200 mesh.

4. The preparation method according to claim 2, characterized in that: The electric arc melting was performed under the conditions of a vacuum degree of 2 x 10 -3 The electric arc melting was performed under the conditions of a vacuum degree of 2 x 10 - 0.05 MPa of argon gas pressure as a protective gas, and 5 times of overturning.

5. The preparation method according to claim 4, characterized in that: The specific method of the electric arc melting is as follows: first, Fe metal, Co metal, and Ni metal are melted under a current intensity of 100 A. After the Fe metal, Co metal, and Ni metal are completely melted, Zr metal, V metal, and La metal are added sequentially under a current intensity of 200 A and melted until completely melted.

6. A method for preparing magnesium hydride hydrogen storage materials based on La-containing high-entropy alloys, characterized in that: Ball milling was performed with a mass ratio of FCNZVs-La to MgH2 of 10:90, a ball-to-material ratio of 80:1, a ball milling speed of 400 rpm, a ball milling time of 18 h, and a ball milling interval to obtain MgH2-FCNZVs-La, a magnesium hydride hydrogen storage material based on a La-containing high-entropy alloy.

7. The preparation method according to claim 6, characterized in that: The ball milling interval is defined as follows: after each ball milling session of 12 minutes, the ball milling is paused for 6 minutes.

8. The preparation method according to claim 7, characterized in that: When the obtained magnesium hydride hydrogen storage material based on La-containing high-entropy alloy is applied in the field of hydrogen storage, the initial hydrogen release temperature drops to 188.92-191.21℃ and the hydrogen release amount reaches 6.64-6.65 wt.% when the catalyst doping amount is 10 wt.%.

9. The preparation method according to claim 7, characterized in that: The obtained magnesium hydride hydrogen storage material based on La-containing high-entropy alloy, when applied in the field of hydrogen storage, exhibits a hydrogen release of 5.36-5.38 wt.% under the conditions of a dehydrogenation temperature of 300℃ and a dehydrogenation time of 7 min; and a hydrogen absorption of 4.95-5.02 wt.% under the conditions of a hydrogen pressure of 2.5 MPa, a hydrogen absorption temperature of 175℃, and a hydrogen absorption time of 4 min.

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