A Si-vanadium-based solid solution hydrogen storage alloy resistant to air poisoning and its preparation method

Abstract

This invention belongs to the field of hydrogen storage alloy technology, specifically relating to a Si-vanadium-based solid solution hydrogen storage alloy resistant to air poisoning and its preparation method. The chemical formula of the air poisoning-resistant vanadium-based hydrogen storage alloy is: (V x Ti y Cr z M 100‑x‑y‑z ) 100‑a Si a Wherein, 60≤x≤80, 10≤y≤40, 10≤z≤40, 0.5≤a≤3, and M is at least one of Fe, Mn, Co, Al, Zr, Nb, and Mo. The preparation process includes mixing and melting the elements to obtain a cast alloy ingot; and heat-treating the cast alloy ingot to obtain a vanadium-based hydrogen storage alloy. This scheme adds a small amount of Si to the vanadium-based hydrogen storage alloy, which does not significantly reduce the reversible hydrogen storage capacity, but significantly enhances its resistance to air poisoning, reduces the decay rate, and improves its activation performance. This technical solution solves the problems of unsatisfactory anti-poisoning and activation performance of vanadium-based hydrogen storage alloys, and has ideal prospects for widespread application.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen storage alloy technology, specifically relating to a Si-vanadium-based solid solution hydrogen storage alloy resistant to air poisoning and its preparation method. Background Technology

[0002] Hydrogen, due to its unique properties, is finding increasingly wider applications in energy, chemical, and defense fields. Hydrogen storage and supply are crucial components of these applications. Using hydrogen storage materials enables high-density, high-safety hydrogen storage at lower pressures. Among these, vanadium-based solid solution hydrogen storage alloys have attracted significant attention due to their reversible hydrogen storage capacity of 2.0 wt% at room temperature, exceeding that of commercially available AB5, AB2, and AB types. In practical applications, the presence of impurities such as CO, CO2, O2, N2, and CH4 in the hydrogen source can poison the surface of the storage material, leading to a decrease in reversible hydrogen storage capacity and hydrogen absorption / desorption kinetics. Purifying the hydrogen source incurs additional costs; therefore, improving the anti-poisoning properties of the hydrogen storage alloy itself is of significant practical importance.

[0003] The poisoning of alloys by impurities in the hydrogen source leads to a decline in kinetics and hydrogen storage capacity. The effects of typical impurity gases on alloy poisoning and the poisoning mechanisms have received widespread attention and research. Tiebang Zhang et al. discovered that Zr(V) 0.95 Ni 0.05 The hydrogen absorption capacity of alloy 2 decreased significantly (0.07 HA) in a hydrogen atmosphere with an oxygen content of 2 vol%. -1 (Renewable Energy 2017, 103, 786-793). Ulrich Ulmer et al. reported V 40 Fe8Ti 28 Cr 24 The alloy lost its activity after four cycles in a hydrogen atmosphere containing 250 ppm O2 (ACS Appl. Mater Interfaces 2018, 10, 1662-1671). YANG FS et al. reported that CO and CO2 occupying active sites on the material surface hinder the decomposition and diffusion of hydrogen, thus affecting hydrogen absorption kinetics. The generated hydrogen-depleted products lead to a continuous decline in hydrogen storage capacity (Int. J. Hydrogen Energy 2017, 42, 16225-16234). In summary, impurity gases either block active sites or react with the alloy surface to form oxides, hydroxides, carbon oxides, etc., directly leading to a decrease in the reversible hydrogen storage capacity of the hydrogen storage alloy, a decline in cycle performance, and a slowdown in the hydrogen absorption rate.

[0004] Existing methods for resisting poisoning of hydrogen storage alloys mainly include two approaches: surface and interface control, and bulk phase control. The Shanghai Institute of Applied Physics, Chinese Academy of Sciences, has applied for a patent for a composite hydrogen storage material with resistance to impurity gas poisoning and its preparation method (CN 115744815 A). This material utilizes Mxene material Ti3C2Cl... x A composite hydrogen storage material was obtained by ball milling and mixing with AB5 rare-earth hydrogen storage alloy. After 10 cycles of hydrogen adsorption and desorption from a CO-containing hydrogen source, the material showed significantly reduced degradation and improved resistance to poisoning. Beijing University of Science and Technology has applied for a patent (CN 105731378 B), using AB5 or AB2 hydrogen storage alloy as the matrix and a gas-selective organic polymer (PMMA) as the reinforcement to obtain a composite hydrogen storage material with certain resistance to poisoning. LaNi was tested in hydrogen gas containing 300 ppm CO. 4.7 Al 0.3 The cycling stability and hydrogen absorption / desorption kinetics of the alloy were improved to some extent. Nanjing Institute of Technology applied for an oxidation-resistant magnesium-based composite hydrogen storage material and its preparation method (CN 112225174 A). A Mg-H2-MgNiH4-Nb2O5-CeO2 composite material was obtained using ball milling technology. The multivalent states of Nb and the redox properties of CeO2 resulted in good hydrogen desorption performance even after long-term exposure to air. The China Academy of Engineering Physics encapsulated dense SiO2 on the surface of an AB-type ZrCo alloy, improving the alloy's resistance to CO, CO2, and air poisoning (ZL201410532678.4).

[0005] South China University of Technology has applied for a method to prepare a Ni-composite AB-type TiFe hydrogen storage alloy (CN 116287825A), which still exhibits good activation performance after 3 days of exposure to air. Zhejiang University has applied for a surface reconstruction method to enhance the carbon dioxide poisoning resistance of AB-type ZrCo alloys (CN 116288081 A). This method involves in-situ generation of a large number of elemental Co nanoparticles that can catalyze H2 dissociation on the alloy surface after room temperature hydrogen absorption saturation and high-temperature dehydrogenation treatment in a H2+CO2 mixed gas, significantly improving the hydrogen absorption kinetics of the alloy under mixed gas conditions. The Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, has applied for a method to prepare an AB-type hydrogen storage alloy resistant to oxygen poisoning (CN 112391568 A). Its composition is Ti. a Fe b Mn c Co d +x% Mm (La and Ce), the addition of mixed rare earth elements improves the alloy's activation properties. The alloy surface is oxidized in oxygen-containing hydrogen gas, and the rare earth alloy oxides can act as channels for hydrogen entry on the alloy surface. The Karlsruhe Institute of Technology (KIT) in Germany reported on V... 40 Fe8Ti 28Cr 24 The alloy with 6 wt% Ce (ACS Appl. Mater. Interfaces 2018, 10, 1662-1671) still maintained some activity after 20 hydrogen adsorption and desorption cycles in 250 ppm O2, but the reversible hydrogen storage capacity decreased by about 80%.

[0006] In summary, among the patents and published papers reported to date, the surface, interface, and bulk phase modulation efforts to improve the anti-poisoning properties of hydrogen storage materials mainly focus on hydrogen storage alloys such as AB5 and AB type. There is relatively little research on vanadium-based hydrogen storage alloys, and their anti-poisoning effects are not significant. Summary of the Invention

[0007] The present invention aims to provide a vanadium-based hydrogen storage alloy resistant to air poisoning, so as to solve the technical problems of unsatisfactory anti-poisoning and activation performance of vanadium-based hydrogen storage alloys in the prior art.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A Si-vanadium-based solid solution hydrogen storage alloy resistant to air poisoning, with the following chemical formula:

[0010] (V x Ti y Cr z M 100-x-y-z ) 100-a Si a Wherein, 60≤x≤80, 10≤y≤40, 10≤z≤40, 0.5≤a≤3, and M is at least one element selected from Fe, Mn, Co, Al, Zr, Nb, and Mo.

[0011] This invention proposes a vanadium-based hydrogen storage alloy with good resistance to air poisoning and its preparation method. The prepared vanadium-based hydrogen storage alloy has advantages such as strong resistance to air poisoning and easy activation at room temperature.

[0012] (1) The present invention precipitates a small amount of highly active second phase at the grain boundary by adding a small amount of Si element and heat treatment at 1300-1400℃.

[0013] (2) The present invention improves the anti-poisoning ability of vanadium-based solid solution hydrogen storage alloy in an air-containing hydrogen atmosphere by adding a small amount of Si element.

[0014] (3) The present invention significantly improves the activation performance of vanadium-based solid solution hydrogen storage alloy at room temperature by adding a small amount of Si element.

[0015] Furthermore, its main phase has a body-centered cubic structure; a second phase is present at the grain boundaries, and the second phase contains Si elements.

[0016] Furthermore, 1 ≤ a ≤ 3.

[0017] This technical solution also provides a method for preparing a Si-vanadium-based solid solution hydrogen storage alloy resistant to air poisoning, comprising the following steps performed sequentially:

[0018] S1: Mix V, Ti, Cr, M, and Si, and obtain a cast alloy ingot through melting;

[0019] S2: Heat treatment is performed on the cast alloy ingot to obtain a vanadium-based hydrogen storage alloy.

[0020] Furthermore, in S1, the melting temperature is 1900-2200℃, the duration is 1-10 minutes, and the melting process is carried out in an argon atmosphere while maintaining a vacuum level of <5×10⁻⁶. -3 Pa.

[0021] Furthermore, in S1, the smelting is carried out in a non-consumable electric arc furnace or a suspension furnace, and a 300A smelting current plus electromagnetic stirring is used, with the smelting number of times being 5.

[0022] Furthermore, in S1, the molar percentage of Si added is 0.5-3%.

[0023] Furthermore, in S1, the atomic ratio of V, Ti, Cr and M is x:y:z:100-xyz; where 60≤x≤80, 10≤y≤40, 10≤z≤40, and M is one or more elements selected from Fe, Mn, Co, Al, Zr, Nb, Mo, etc.

[0024] Furthermore, in S2, the heat treatment temperature is 1300-1400℃.

[0025] Furthermore, in S2, the heat treatment time is 0.5-6 hours.

[0026] The principle behind this solution is:

[0027] The vanadium-based hydrogen storage alloy in this scheme incorporates a small amount of Si, predominantly exhibiting a body-centered cubic structure with a small amount of highly active second phase appearing at grain boundaries or within the grains. The addition of Si significantly improves the air poisoning resistance of vanadium-based hydrogen storage and markedly enhances the activation performance of the vanadium-based hydrogen storage alloy.

[0028] The beneficial effects of this plan are as follows:

[0029] (1) This invention found that adding a small amount of Si to vanadium-based hydrogen storage alloys did not significantly reduce the reversible hydrogen storage capacity, but it significantly enhanced the resistance to poisoning in hydrogen environments containing air, exhibiting a low decay rate. For example, the (V) alloy described in this invention... 75 Ti 11 Cr 13Fe1) 99 Si1 exhibited a 15.2% decay rate after 10 hydrogen adsorption / desorption cycles in a hydrogen atmosphere containing 250 ppm air; in contrast, V without Si showed a significantly lower decay rate. 75 Ti 11 Cr 13 Fe1 attenuation rate reached 72.5% under this poisoning condition, and its anti-poisoning performance was greatly improved.

[0030] (2) This invention found that adding a small amount of Si to vanadium-based hydrogen storage alloys did not significantly reduce the reversible hydrogen storage capacity, but significantly improved the activation performance of the alloys. For example, V without added Si... 75 Ti 11 Cr 13 After being vacuumed at 50°C for 1 hour, the Fe1 alloy did not absorb hydrogen within half an hour under a hydrogen pressure of 50°C and 5MPa. The Si alloy sample described in this invention can rapidly absorb hydrogen after a certain incubation period at 50°C and 5MPa, indicating a significant improvement in activation performance. Attached Figure Description

[0031] Figure 1 The X-ray diffraction patterns are those of Examples 1-4 and Comparative Examples 1 and 5.

[0032] Figure 2 Optical micrographs of Examples 1-4 and Comparative Examples 1 and 5.

[0033] Figure 3 The images are SEM-BSE images of Examples 1-2, 5-6 and Comparative Examples 1-5.

[0034] Figure 4 The first hydrogen absorption activation curves are for Examples 1-6 and Comparative Examples 1-5.

[0035] Figure 5 The PCT curves for hydrogen desorption at 50°C are for Examples 1-4 and Comparative Examples 1 and 5.

[0036] Figure 6 This is the initial hydrogen absorption activation curve of the second phase in Example 1.

[0037] Figure 7 The X-ray diffraction patterns are those of the initial state, hydrogen absorption state, and hydrogen release state of the second phase in Example 1.

[0038] Figure 8 The thermal desorption curves of the second phase in Example 1 are obtained by heating from 25 to 400°C.

[0039] Figure 9 The hydrogen absorption kinetics curves for Example 1 are obtained after 10 cycles in an H2 atmosphere containing 250 ppm air.

[0040] Figure 10The hydrogen absorption kinetics curves for Example 2 are obtained after 10 cycles in an H2 atmosphere containing 250 ppm air.

[0041] Figure 11 The hydrogen absorption kinetics curves for Example 3 are obtained after 10 cycles in an H2 atmosphere containing 250 ppm air.

[0042] Figure 12 The hydrogen absorption kinetics curves for Example 4 are obtained after 10 cycles in an H2 atmosphere containing 250 ppm air.

[0043] Figure 13 The hydrogen absorption kinetics curves for Example 5 are obtained after 10 cycles in an H2 atmosphere containing 250 ppm air.

[0044] Figure 14 Example 6 shows the hydrogen absorption kinetics curves after 10 cycles in an H2 atmosphere containing 250 ppm air.

[0045] Figure 15 The hydrogen absorption kinetics curves for Comparative Example 1 are obtained after 10 cycles in an H2 atmosphere containing 250 ppm air.

[0046] Figure 16 The hydrogen absorption kinetics curves for Comparative Example 2 are obtained after 7 cycles in an H2 atmosphere containing 250 ppm air.

[0047] Figure 17 The hydrogen absorption kinetics curves for Comparative Example 3 are shown in 7 cycles under an H2 atmosphere containing 250 ppm air.

[0048] Figure 18 The hydrogen absorption kinetic curves for Comparative Example 4 are obtained after 6 cycles in an H2 atmosphere containing 250 ppm air. Detailed Implementation

[0049] The present invention will be further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto. Unless otherwise specified, the technical means used in the following embodiments are conventional means well known to those skilled in the art; the experimental methods used are all conventional methods; and the materials, reagents, etc. used are all commercially available.

[0050] A vanadium-based hydrogen storage alloy resistant to air poisoning is prepared by the following method:

[0051] (1) Preparation of high vanadium-based hydrogen storage alloys.

[0052] Vanadium-based hydrogen storage alloys were prepared by adding certain amounts of elements such as Ti, Cr, Fe, and Si in stoichiometric proportions to pure vanadium. The chemical formula for the prepared hydrogen storage alloy is (V... x Ti y Cr z M 100-x-y-z ) 100-a Sia Where x, y, and z represent the atomic numbers of V, Ti, and Cr, respectively, x = 60-80, 10 ≤ y ≤ 40, 10 ≤ z ≤ 40, and 0.5 ≤ a ≤ 3. M is at least one element selected from Fe, Mn, Co, Al, Zr, Nb, and Mo. The mixture is prepared by melting in a vacuum electric arc furnace or a vacuum levitation furnace. The melting process employs a specific melting current and electromagnetic stirring, with a melting temperature of 1900-2200℃ and a melting time of 1-10 minutes. Multiple high-purity argon gas purgings are performed, and the vacuum degree is less than 5 × 10⁻⁵. - 3 Pa, and finally smelting was carried out under the protection of high-purity argon gas.

[0053] (2) Vacuum annealing to homogenize the composition.

[0054] The as-cast alloy obtained in the previous step was annealed under vacuum at 1300-1400℃ for 0.5-6 hours to improve the uniformity of the microstructure. The annealed vanadium-based hydrogen storage alloy exhibited a predominantly body-centered cubic structure with a small amount of highly active second phase appearing at grain boundaries or within grains. When other process parameters met the requirements, the above-mentioned annealing temperature and time ensured the formation of the second phase, resulting in a high-vanadium-based hydrogen storage alloy with ideal performance. Subsequent examples will use a set annealing temperature of 1400℃ for specific experimental studies to illustrate this.

[0055] This invention can significantly improve the resistance to air poisoning in vanadium-based hydrogen storage and significantly improve the activation performance of vanadium-based hydrogen storage alloys.

[0056] Example 1: High vanadium-based hydrogen storage alloy (V 75 Ti 11 Cr 13 Fe1) 99 Si1

[0057] (1) Implementation steps

[0058] The first step involves weighing pure V (99.99 wt%), and adding certain amounts of Ti (99.99 wt%), Cr (99.9 wt%), Fe (99.95 wt%), and Si (99.95 wt%) to prepare (V) 75 Ti 11 Cr 13 Fe1) 99A vanadium-based hydrogen storage alloy based on Si1 was prepared by batching materials according to the alloy's stoichiometric ratio and then melting and turning the alloy five times in a vacuum magnetic levitation induction furnace under high-purity argon (99.99%) protection to produce a cast alloy ingot weighing approximately 20g. In this embodiment, the melting process used a 300A melting current with electromagnetic stirring, the melting temperature was controlled at approximately 2000℃, and the melting time was approximately 5 minutes. The melting process involved three high-purity argon gas purgings, and the vacuum degree was controlled to be <5×10⁻⁶. -3 Pa is smelted under the protection of high-purity argon gas.

[0059] The second step involves heating the as-cast alloy ingot at 1400℃ under vacuum (vacuum degree < 5 × 10⁻⁶). -3 Heat treatment for 0.5 h under vacuum (without high-purity argon gas washing or protection) to improve tissue homogeneity.

[0060] (2) Phase structure

[0061] XRD: The sample was prepared as a 100-mesh powder for X-ray diffraction testing. The XRD pattern shows that Example 1 is a single-phase BCC. Figure 1 As shown, the lattice constant of the BCC phase is 0.3022 nm.

[0062] Metallography and SEM: The cast alloy ingot was sliced ​​using a slicing machine to obtain 1-3 mm alloy thin sheets. The alloy thin sheets were then mounted on sandpaper, polished, and etched with an etching solution (HNO3:H2O:HF = 1:2:1). Metallographic and SEM images were then obtained to obtain surface and microscopic morphology images.

[0063] like Figure 2 As shown, microcrystal cracks were observed at the grain boundaries of the sample in Example 1 after etching, indicating the formation of a small amount of second phase. Figure 3 In the study, backscattered electron diffraction (ESD) patterns confirmed the formation of a second phase along the grain boundaries. Due to the insufficient corrosion resistance of this second phase, cracks formed after corrosion. EDS analysis revealed a higher Ti and Si content in the second phase, a significant contrast to the composition of the main phase. Figure 3 As shown.

[0064] (3) Hydrogen absorption and desorption performance

[0065] Step 1: Activation. The cast alloy ingot was crushed, and alloy particles of 5-10 mm in size were taken and placed in the sample chamber for testing. Initially, a vacuum was applied at 50°C for 1 hour, followed by a pressurization of 5 MPa hydrogen gas at 50°C. After a 20-minute incubation period, the alloy began to rapidly absorb hydrogen, with an initial hydrogen absorption of 3.72 wt%. The experimental results are shown below. Figure 4 .

[0066] Step 2: Kinetic Performance Testing. In Example 1, after activation, the system was evacuated at 50°C for 15 minutes, then cooled to room temperature. A hydrogen absorption test was performed at 0°C with 8 MPa hydrogen gas, followed by a hydrogen release PCT test at 50°C. Figure 5 As shown, the hydrogen release platform pressure is approximately 0.51 MPa, and the hydrogen release amount is 2.48 wt%, which is slightly lower than the hydrogen release amount of 2.57 wt% in Comparative Example 1.

[0067] (4) Second phase determination and performance testing

[0068] Based on the EDS, the composition information of the second phase was obtained, and according to the approximate composition of the second phase, the same synthesis process as in "(1) Implementation Steps" of this embodiment was used to obtain Ti. 53 Cr 15 V 17 Si 11 Fe3 alloy ingots were used to study the properties of the second phase.

[0069] The alloy was incubated at 50°C with 5 MPa hydrogen gas. After a 20-minute incubation period, the alloy began to rapidly absorb hydrogen, with an initial absorption of 3.07 wt%. The experimental results are shown below. Figure 6 The verification results show that the second phase obtained by this method has high activity.

[0070] Desorption curves of hydrogen-absorbed alloys were obtained by heating from 25 to 400 °C, as shown below. Figure 7 As shown, at temperatures below 120℃, a small portion of hydrogen is released. Above 200℃, hydrogen desorbs rapidly and in large quantities. This indicates that hydrogen adsorption in the second phase is more difficult to desorb, and it remains in a saturated hydrogen adsorption state within 50℃, which may explain its prolonged high activity.

[0071] X-ray diffraction tests were performed on the alloy in its initial state (bulk), saturated hydrogen-absorbing state (powder), and hydrogen-degrading state (powder), respectively. Figure 8 In the initial state, the dominant phase is BCC, with a small amount of Ti5Si3 present. The overall diffraction peaks of the BCC phase show a shift towards smaller angles, suggesting that heteroatoms increase the cell parameters and interplanar spacing. After hydrogen absorption, the FCC phase and a small amount of Ti5Si3H appear. 0.9 This corresponds to a hydrogen absorption capacity of 3.07 wt% in the first cycle. Subsequent high-temperature hydrogen release treatment at 400℃ was performed on the FCC phase and Ti5Si3H... 0.9 The peaks have mostly disappeared, but a small amount of BCT phase remains (a sharp peak exists at 40-42°).

[0072] It is evident that the second phase, after hydrogenation, remains stable within the hydrogen absorption / desorption test temperature range (0℃-50℃), exhibiting high activity, and is consistent with the alloy (V). 75 Ti 11 Cr 13 Fe1)99 When Si1 absorbs and desorbs hydrogen in a hydrogen atmosphere containing air, the hydrogen gas provides a channel for its entry.

[0073] (5) Air toxicity performance test

[0074] The activated alloy was ground and passed through a 200-mesh sieve to obtain alloy powder with a size of approximately 75 μm, which was used for air poisoning experiments. The first cycle involved hydrogen absorption at 2.0 MPa pure hydrogen and 0°C, achieving a hydrogen absorption rate of 2.20 wt%. After hydrogen saturation, hydrogen was released under vacuum at 50°C for 15 minutes. Then, hydrogen absorption and desorption cycles were performed under a hydrogen atmosphere containing 250 ppm air at 2.0 MPa. Figure 9 As shown, after 10 cycles, the hydrogen uptake decreased from 2.20 wt% to 1.87 wt%, with a reversible hydrogen storage capacity reduction rate of 15.2%. Compared with Comparative Example 1, after 10 poisoning cycles, the hydrogen uptake decreased from 2.38 wt% to 0.66 wt%, with a reduction rate of 72.5%. Figure 13 It is evident that the addition of Si significantly improves the alloy's resistance to air poisoning.

[0075] Example 2: High vanadium-based hydrogen storage alloy (V 75 Ti 11 Cr 13 Fe1) 97 Si3

[0076] Except for the elemental composition, the implementation steps are basically the same as in Example 1. Example 2 is still almost a single-phase BCC structure, see... Figure 1 Microcrystal cracks were observed at the grain boundaries after the sample was etched, indicating the precipitation of a small amount of second phase at the grain boundaries. Figure 2 ).

[0077] After being vacuumed at 50°C for 1 hour, the alloy immediately absorbs hydrogen at 50°C and 5 MPa, exhibiting good activation performance. The hydrogen release at 50°C reaches 2.25 wt%. Figure 5 After 10 cycles of air poisoning testing, the reversible hydrogen storage capacity decayed by 13.4%, as... Figure 10 As shown.

[0078] Example 3: High vanadium-based hydrogen storage alloy (V 60 Ti 18 Cr 21 Fe1) 99 Si1

[0079] Except for the elemental composition, the implementation steps are basically the same as in Example 1. Example 3 is still almost a single-phase BCC structure, see... Figure 1 After etching, microcrystal cracks were observed at the grain boundaries of the sample, and a small amount of second phase precipitated on the surface at the grain boundaries. Figure 2The alloy, after being vacuumed at 50℃ for 1 hour, and then incubated at 50℃ and 5MPa for 8 minutes, rapidly absorbed hydrogen, exhibiting good activation performance. The hydrogen release at 50℃ reached 2.47wt%, see [reference needed]. Figure 5 After 10 cycles of air poisoning test, the reversible hydrogen storage capacity decayed by 4%, such as... Figure 11 As shown, it exhibits strong resistance to toxicity.

[0080] Example 4: High vanadium-based hydrogen storage alloy (V 80 Ti9Cr 10 Fe1) 99.5 Si 0.5

[0081] The implementation steps are basically the same as in Example 1, the difference being the elemental composition and the fact that the cast alloy ingot is heat-treated in vacuum at 1300°C for 2 hours. Example 4 has an almost BCC single-phase structure, see... Figure 1 However, a small amount of second phase is generated at the grain boundaries. Figure 2 The alloy, after being vacuumed at 50℃ for 1 hour, and then incubated at 50℃ and 5MPa for 5 minutes, rapidly absorbed hydrogen, exhibiting good activation performance. Hydrogen release at 50℃ reached 2.39 wt%, see [reference needed]. Figure 5 After 10 cycles of air toxicity testing, the attenuation rate was 28%, such as... Figure 12 As shown.

[0082] Example 5: High vanadium-based hydrogen storage alloy (V 75 Ti 11 Cr 11 Mn1Co1Al1) 99 Si1

[0083] In the implementation steps, in addition to V, Ti, Cr, and Si, Mn (99.8% purity), Co (99.95% purity), and Al (99.999% purity) were added to prepare a high-vanadium-based hydrogen storage alloy. Other implementation steps were the same as in Example 1. In Example 5, a small amount of second-phase precipitation could be observed through backscattering, such as... Figure 3 As shown, after being vacuumed at 50℃ for 1 hour, the alloy can rapidly absorb hydrogen after an incubation period of 10 minutes at 50℃ and 5MPa, exhibiting good activation performance. Figure 4 After 10 cycles of air poisoning testing, the reversible hydrogen storage capacity decayed by 21.2%. Figure 13 As shown.

[0084] Example 6: High vanadium-based hydrogen storage alloy (V 75 Ti 11 Cr 11 Zr1Nb1Mo1) 99 Si1

[0085] In the implementation steps, in addition to V, Ti, Cr, and Si, Zr (99.95% purity), Nb (99.95% purity), and Mo (99.95% purity) were added to prepare a high-vanadium-based hydrogen storage alloy. Other implementation steps were the same as in Example 1. In Example 6, a small amount of second-phase precipitation could be observed through backscattering, such as... Figure 3 As shown. After being evacuated at 50℃ for 1 hour, the alloy can immediately absorb hydrogen at 50℃ and 5MPa, exhibiting good activation performance. Figure 4 After 10 cycles of air poisoning test, the reversible hydrogen storage capacity decayed by 7%, such as... Figure 14 As shown, it exhibits strong resistance to toxicity.

[0086] Comparative Example 1: High Vanadium-Based Hydrogen Storage Alloy V 75 Ti 11 Cr 13 Fe1

[0087] Except for the elemental composition, the implementation steps are the same as in Example 1. Comparative Example 1 is a BCC single-phase structure, see... Figure 1 No second phase formation was observed. Figure 2 , 3 At 50°C, hydrogen release reached 2.57 wt%. Figure 5 The alloy failed to activate after being vacuumed at 50°C for 1 hour and then incubated at 50°C and 5MPa for 30 minutes. After 10 cycles of air poisoning test, the reversible hydrogen storage capacity decay rate was 72.5%. Figure 15 As shown.

[0088] Comparative Example 2: High-vanadium-based hydrogen storage alloy (V 75 Ti 11 Cr 13 Fe1) 99 Si1# As-cast state

[0089] The implementation steps are basically the same as in Example 1, except that the cast alloy ingot was not subjected to vacuum heat treatment (i.e., the second step was not performed), and various tests were conducted on the obtained alloy ingot. No second phase precipitation was observed at the grain boundaries in Comparative Example 2. Figure 3 After 7 cycles of air poisoning test, the reversible hydrogen storage capacity decayed by 86.5%, as shown below. Figure 16 As shown.

[0090] Comparative Example 3: High-vanadium-based hydrogen storage alloy (V 75 Ti 11 Cr 13 Fe1) 99 Si1# heat-treated sample at 1200℃

[0091] The implementation steps are basically the same as in Example 1, except for the adjustment of the heat treatment parameters (second step). The cast alloy ingot was heat-treated at 1200℃ under vacuum for 0.5h. In Comparative Example 3, no grain boundary second phase precipitation was observed after heat treatment at 1200℃. Figure 3 After 7 cycles of air poisoning test, the reversible hydrogen storage capacity decayed by 89.0%, as shown below. Figure 17 As shown.

[0092] Comparative Example 4: High-vanadium-based hydrogen storage alloy (V 75 Ti 11 Cr 13 Fe1) 99.7 Si 0.3

[0093] Except for the elemental composition, the implementation steps were the same as in Example 1. No second phase precipitation was observed at the grain boundaries in Comparative Example 4. Figure 3 After 6 cycles of air poisoning test, the reversible hydrogen storage capacity decay rate was 86.9%, such as... Figure 18 As shown.

[0094] Comparative Example 5: High Vanadium-based Hydrogen Storage Alloy (V 75 Ti 11 Cr 13 Fe1) 95 Si5

[0095] The implementation steps are basically the same as in Example 1. Comparative Example 5 is still almost a single-phase BCC structure, see... Figure 1 However, after etching, numerous microcrystal cracks appeared at the grain boundaries, indicating the formation of a large amount of second phase. Figure 2 , 3 The alloy, after being vacuumed at 50℃ for 1 hour, exhibited good activation performance after a 2-minute incubation period at 50℃ and 5MPa, and rapidly absorbed hydrogen. However, due to the excessive Si content, the hydrogen storage capacity was significantly reduced, with the reversible hydrogen storage capacity at 50℃ reaching only 1.62wt%. Figure 5 Furthermore, the platform pressure is too high, exceeding 5MPa. Figure 5 The pressure exceeded the limits of existing laboratory poisoning mixing equipment, therefore no attenuation rate test was conducted. Furthermore, compared to other examples and comparative examples, Comparative Example 5 showed a significant decrease in hydrogen release after Si addition, making further poisoning attenuation rate testing largely meaningless.

[0096] The performance test results of the high vanadium-based hydrogen storage alloys in the examples and comparative examples are summarized in Table 1.

[0097] Table 1: Activation incubation period, hydrogen release (reversible hydrogen storage capacity), and decay rate of the high vanadium-based hydrogen storage alloys prepared in the examples and comparative examples (test conditions are detailed in Example 1, "—" indicates that this test was not performed).

[0098]

[0099]

[0100] In existing technologies, reports on the effects of Si doping in high-vanadium-based hydrogen storage alloys are mostly negative. Si is generally considered an impurity and needs to be removed from the alloy to mitigate its negative impact. This technical solution overcomes this bias by actively adding a certain amount of Si to improve the overall performance of the alloy. More specifically, this is described below:

[0101] (1) Appropriate addition of Si enhances the anti-poisoning ability of high vanadium-based hydrogen storage alloys and shortens the incubation period.

[0102] Comparing the performance test data of the high-vanadium-based hydrogen storage alloys in Comparative Example 1, Example 1, Example 2, and Comparative Example 5, it can be seen that the hydrogen release capacity of the high-vanadium-based hydrogen storage alloy gradually decreases with the increase of Si content. In the above comparative examples and examples, all conditions were the same except for the amount of Si added. The hydrogen release capacity of Comparative Example 1 without Si addition was 2.57%, that of Example 1 with 1% Si addition was 2.48%, that of Example 2 with 2% Si addition was 2.25%, and that of Comparative Example 5 with 5% Si addition was 1.62%. This indicates that the greater the amount of Si added, the greater the negative impact on the hydrogen storage and release capacity of the high-vanadium-based hydrogen storage alloy. This aligns with other reports in the prior art. For example, Chinese patent CN101624674A, "Solid Solution Hydrogen Storage Alloy Using Low-Cost Ferrovanadium Alloy as Raw Material," reports that ferrovanadium alloys cost only 1 / 5 to 1 / 6 of pure vanadium. Using ferrovanadium as a raw material to prepare Ti-Cr-V-Fe hydrogen storage alloys simultaneously satisfies the dual requirements of adding both vanadium and Fe, thus improving alloy performance. However, because ferrovanadium alloys contain oxides or other phases containing Al and / or Si, they have certain adverse effects on alloy performance, such as reducing hydrogen storage capacity, increasing plateau pressure, and tilting the hydrogen absorption / desorption plateau. Therefore, researching alloys using ferrovanadium as raw material to obtain hydrogen storage performance close to that of pure vanadium and pure iron is of great significance. Most prior art reports on the inclusion of Si in vanadium-based solid solution hydrogen storage alloys describe the negative effects of Si. Those skilled in the art do not tend to add Si to vanadium-based solid solution hydrogen storage alloys to reduce the negative impact of Si on alloy performance.

[0103] However, during the research process of this scheme, the inventors discovered that all effects of adding Si were negative. Appropriate Si addition can effectively improve the anti-poisoning ability of high-vanadium-based hydrogen storage alloys, and the hydrogen storage capacity decay rate is significantly reduced after multiple cycles. Furthermore, Si addition also shortens the activation incubation period; after a shorter incubation period, hydrogen can be rapidly absorbed, indicating a significant improvement in activation performance. Such phenomena were unforeseen by the inventors before the development of this technology. Moreover, the inventors also found that with a small amount of Si added, its impact on the hydrogen release (reversible hydrogen storage capacity) of the high-vanadium-based hydrogen storage alloy is not significant, only an acceptable, very small reduction. However, a small amount of Si addition can simultaneously greatly reduce the decay rate; therefore, a small amount of Si addition can lead to an overall improvement in product performance. A balance point can be found in the amount of Si added, maintaining a certain amount of hydrogen storage and release while simultaneously reducing decay and increasing the activation rate. Therefore, this technical solution uses a Si addition amount of 0.5-3% (a = 0.5-3) to achieve the above objectives and form a second phase in the product. Furthermore, an addition of 1-3% Si is a better choice (a=1-3), which further ensures that the hydrogen release capacity of the high vanadium-based hydrogen storage alloy will not decrease excessively.

[0104] (2) The amount of vanadium added affects the anti-attenuation performance of high vanadium-based hydrogen storage alloys.

[0105] The inventors also studied the amount of V added to the high-vanadium-based hydrogen storage alloy. Comparing Examples 3, 4, and 1, it can be seen that the amount of V added (60-80%, x = 60-80) has little effect on the hydrogen storage and desorption performance of the high-vanadium-based hydrogen storage alloy, and all are relatively excellent. However, the lower the amount of V added, the more ideal the anti-attenuation performance of the high-vanadium-based hydrogen storage alloy, preferably x = 60-75, with x = 60 being the best (4% attenuation rate).

[0106] (3) The amount of Si added significantly affects whether a second phase forms and the performance of high vanadium-based hydrogen storage alloys.

[0107] In this technical solution, the raw materials for preparing the high-vanadium-based hydrogen storage alloy are high-purity elemental substances, avoiding the introduction of unnecessary impurities. This process results in the following structure: the main phase is a body-centered cubic structure; and a small amount of a second phase (mainly Si and Ti) precipitates at the grain boundaries. In the inventors' prior research (CN115612903B A high-vanadium solid solution type hydrogen storage alloy and its preparation method), high-vanadium-based hydrogen storage alloys were prepared using raw materials containing certain impurities, including Si (usually existing in the form of oxides). Although methods such as adding Ce to remove impurities were employed during refining and smelting, the resulting high-vanadium-based hydrogen storage alloy still contained very trace amounts of Si. However, in the above case, due to the low Si content and the different addition method and form of Si in the raw materials compared to this process, a small amount of a second phase did not precipitate at the grain boundaries. Unplanned Si doping or residues formed due to impurities cannot form a second phase and reduce the alloy's attenuation rate, thus failing to achieve the air poisoning resistance objective of this solution. Comparative Example 4 of this scheme is similar to the case of very small Si doping mentioned above. The experimental results show that a second phase cannot be formed, and the ability to resist poisoning cannot be improved.

[0108] (4) Vacuum annealing conditions affect the formation of the second phase.

[0109] In addition, the process conditions of annealing the cast alloy at 1300-1400℃ under vacuum are crucial for the formation of the second phase. Without vacuum heat treatment or at too low a temperature, the second phase cannot be formed, which in turn will prevent the product from improving its resistance to poisoning and from reducing the activation incubation period.

[0110] Based on the above Examples 1-6 and Comparative Examples 1-5, the negative impacts of Si reported in previous patents mainly refer to its reduction in hydrogen storage capacity and increase in platform pressure. The anti-poisoning performance mentioned in this solution focuses on the alloy surface properties. The embodiments in this solution also conform to the influence of Si addition on platform pressure and hydrogen storage capacity. Previous studies have not explored the contact between the alloy surface and air after Si addition. This study reveals that appropriate silicon addition under certain process conditions can improve the anti-poisoning performance of the product, which is non-obvious compared to existing reports. The air poisoning resistance of this solution is achieved with minimal impact on the basic hydrogen absorption performance after Si addition, considering the comprehensive performance of the alloy and application conditions. Simultaneously, the highly active second phase is also one of the keys to achieving anti-poisoning in this solution. Experimental data shows that the composition of the second phase is comprehensively controlled by the amount of Si added and the melting heat treatment conditions.

[0111] Comparative Example 6:

[0112] Yan et al. reported that by adding Si to vanadium-based hydrogen storage materials, (V30 Ti 35 Cr 25 Fe 10 ) 1-x Si x The system with (x = 0.32-2.5 at.%) also generates a second phase (Journal of Alloys and Compounds 2007, 441, 297-300). However, in comparison, the second phase generated in that system is a Laves phase, while the second phase generated in this scheme is mainly a BCC phase, containing a small amount of Ti5Si3 phase. Compared with this scheme, the vanadium content and Ti / Cr ratio in that report are significantly different, and the alloy preparation method in that report does not include the 1400℃ heat treatment step implemented in this scheme. The differences mentioned above may lead to differences in the process conditions for generating a second phase, as well as differences in the composition and properties of the final second phase, thus resulting in differences in the technical effects brought about by Si addition. In particular, using the alloy preparation method of this scheme, a small amount of Si addition can effectively improve the poisoning resistance of high vanadium-based hydrogen storage alloys, which has not been reported in the prior art.

[0113] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A Si-vanadium-based solid solution hydrogen storage alloy resistant to air poisoning, characterized in that: Its chemical formula is: (V x Ti y Cr z M 100-x-y-z ) 100-a Si a The molar percentage of Si added is 0.5-3%; the atomic ratio of V, Ti, Cr and M is x:y:z:100-xyz; where 60≤x≤80, 10≤y≤40, 10≤z≤40, 0.5≤a≤3, and M is at least one element selected from Fe, Mn, Co, Al, Zr, Nb and Mo. Its main phase is a body-centered cubic structure; a small amount of second phase precipitates at the grain boundaries, and the main elements of the second phase are Si and Ti; The hydrogen storage alloy is obtained by the following preparation method, comprising the following steps performed in sequence: S1: Mix V, Ti, Cr, M, and Si, and obtain a cast alloy ingot through melting; S2: Heat-treat the cast alloy ingot at 1300-1400℃ for 0.5-6h to obtain vanadium-based hydrogen storage alloy.

2. The Si-vanadium-based solid solution hydrogen storage alloy resistant to air poisoning according to claim 1, characterized in that: 1≤a≤3。 3. The method for preparing a Si-vanadium-based solid solution hydrogen storage alloy resistant to air poisoning according to claim 1 or 2, characterized in that: The steps are as follows, performed sequentially: S1: Mix V, Ti, Cr, M, and Si, and obtain a cast alloy ingot through melting; S2: Heat-treat the cast alloy ingot at 1300-1400℃ for 0.5-6h to obtain vanadium-based hydrogen storage alloy.

4. The method for preparing a Si-vanadium-based solid solution hydrogen storage alloy resistant to air poisoning according to claim 3, characterized in that: In S1, the melting temperature is 1900-2200℃, the duration is 1-10 minutes, and the melting process is carried out in an argon atmosphere while maintaining a vacuum level of <5×10⁻⁶. -3 Pa.

5. The method for preparing a Si-vanadium-based solid solution hydrogen storage alloy resistant to air poisoning according to claim 4, characterized in that: In S1, smelting is carried out in a non-consumable electric arc furnace or a suspension furnace, and a 300A smelting current plus electromagnetic stirring is used, with smelting times of 5.

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