Easily-activated high-capacity vanadium-based hydrogen storage alloy and preparation method thereof

Abstract

The composition general formula of the vanadium-based hydrogen storage alloy is VxTiyCrzCCe, x is larger than or equal to 0.7 and smaller than or equal to 0.8, y is larger than or equal to 0.04 and smaller than or equal to 0.1, z is larger than or equal to 0.1 and smaller than or equal to 0.18, x + y + z = 1, and a is larger than or equal to 0.001 and smaller than or equal to 0.005. The prepared vanadium-based hydrogen storage alloy has the advantages that the preparation process is simple, the hydrogen storage alloy which is easy to activate, high in capacity and good in cycling stability can be obtained by adding trace Ce, and the vanadium-based hydrogen storage alloy is suitable for large-scale generation preparation and commercial application. The alloy is prevented from being locally oxidized in the smelting process due to a small amount of Ce element, and the problem that the hydrogen absorption capacity is reduced due to excessive rare earth elements is avoided, so that the activation performance of the alloy is improved, and meanwhile, the high hydrogen storage capacity is obtained.

Description

Technical Field

[0001] The invention relates to an easily activated high-capacity vanadium-based hydrogen storage alloy and a preparation method thereof, and belongs to the field of solid-state hydrogen storage materials. Background Art

[0002] At present, the world's energy system is still dominated by fossil fuels. The large-scale use of fossil fuels will produce greenhouse gases and toxic and hazardous substances, thus causing a series of environmental problems. Hydrogen energy, as a clean, efficient, safe and sustainable new energy, is regarded as the cleanest energy with the greatest development potential in the 21st century and is also the strategic energy development direction of mankind. The key problem of hydrogen energy is that hydrogen is difficult to store and transport safely and efficiently. At present, traditional storage methods include high-pressure gas storage and transportation, low-temperature liquid storage and transportation, etc. Solid-state hydrogen storage is a very promising storage and transportation method due to its high safety, high volume density and excellent cycle performance. In recent years, the research and development of hydrogen storage alloy materials with large hydrogen storage capacity, good activation performance, good kinetic performance and long cycle life has become a research hotspot.

[0003] V-based hydrogen storage alloy belongs to BCC type solid hydrogen storage alloy. It is one of the most promising hydrogen storage materials because of its high theoretical hydrogen storage capacity, low hydrogen absorption and desorption temperature, and good cycle performance. However, V-based hydrogen storage alloy needs to be activated before use so that the hydrogen storage alloy can reach the optimal hydrogen absorption and desorption state. Titanium-vanadium-based solid solution usually needs high-temperature activation to absorb and desorb hydrogen, which brings difficulties to its practical application. In addition, vanadium-based hydrogen storage alloy can only reversibly release part of the hydrogen at room temperature and pressure, and the smelting of metal vanadium is very difficult, making it very expensive and the alloy cost is very high. How to improve its effective hydrogen storage capacity and reduce the alloy cost is the main problem it faces. At present, the multi-element alloying method is an effective method to improve the effective hydrogen storage capacity of vanadium-based alloys, but alloying will also lead to poor cycle performance of the alloy (Li Duo, Lou Yuwan, Du Junlin, et al. Adding Mn and Co to V 80 Ti8Cr 12Influence of rare earth elements on the hydrogen storage properties of alloys [J]. Journal of Functional Materials and Devices, 2015, 21(05): 145-149.), adding rare earth elements can improve the activation properties of alloys, but too high a content will lead to a decrease in the hydrogen storage capacity of the alloy (Xiao H, Hu H, Li J, et al. Enhanced hydrogen storage properties of Ti-Cr-Nb alloys by melt-spin and Mo-doping [J]. International Journal of Hydrogen Energy, 2023, 48(58): 22174-22182.). Therefore, it is very important to develop a technology that can improve the activation properties of vanadium-based hydrogen storage alloys without reducing the hydrogen storage capacity of the alloy for the practical application of vanadium-based alloys. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides an easily activated high-capacity vanadium-based hydrogen storage alloy and a preparation method thereof. The developed easily activated high-capacity vanadium-based hydrogen storage alloy has a simple preparation process and can be activated at 80°C. At the same time, the alloy has a high hydrogen storage capacity and excellent cycle stability, which is conducive to commercial application.

[0005] In order to achieve the above-mentioned invention effects, the present invention adopts the following technical solutions:

[0006] An easily activated high-capacity vanadium-based hydrogen storage alloy, the chemical formula of the alloy composition is: V x Ti y Cr z Ce a , and the general chemical formula satisfies the conditions: 0.7≤x≤0.8, 0.04≤y≤0.1, 0.1≤z≤0.19, and x+y+z=1, 0.001≤a≤0.005.

[0007] Preferably, the alloy crystals of the present invention mainly have a body-centered cubic (BCC) structure.

[0008] Further preferably, the main phase of the alloy crystal of the present invention is BCC phase, and also includes a small amount of CeO2 phase. The alloy crystal structure of the present invention is a two-phase coexistence structure with BCC phase as the main phase and CeO2 phase as the main phase.

[0009] Preferably, the general chemical formula of the alloy of the present invention satisfies the following conditions: 0.75≤x≤0.80, 0.05≤y≤0.07, 0.14≤z≤0.19, and x+y+z=1, 0.001≤a≤0.003.

[0010] More preferably, the chemical formula of the alloy of the present invention satisfies the following conditions: 0.78≤x≤0.80, 0.05≤y≤0.07, 0.14≤z≤0.16, and x+y+z=1, 0.001≤a≤0.003.

[0011] Preferably, after vacuuming at 80° C. for 120 minutes, the vanadium-based hydrogen storage alloy of the present invention can be fully activated by absorbing and desorbing hydrogen no more than three times at 25° C. and H2 of not less than 4.5 MPa.

[0012] Preferably, under the conditions of 25° C. and H 2 of not less than 4.5 MPa, the maximum hydrogen absorption capacity of the vanadium-based hydrogen storage alloy of the present invention is ≥2.27wt%, and the hydrogen storage capacity retention rate after 1000 cycles of hydrogen absorption and desorption is ≥90%.

[0013] Preferably, under the conditions of 25° C. and H 2 of not less than 7 MPa, the maximum hydrogen absorption capacity of the vanadium-based hydrogen storage alloy of the present invention is ≥2.43wt%, and the hydrogen storage capacity retention rate after 1000 cycles of hydrogen absorption and desorption is ≥90%.

[0014] Preferably, the hydrogen absorption within 200 s at 25° C. and 4.5 MPa of H 2 reaches 2.41 wt.%, and the hydrogen absorption within 200 s reaches 90% of the maximum hydrogen absorption.

[0015] A method for preparing the easily activated high-capacity vanadium-based hydrogen storage alloy according to the present invention comprises the following steps:

[0016] The chemical formula of the vanadium-based hydrogen storage alloy prepared according to the target is: x Ti y Cr z Ce a , and the chemical formula satisfies the conditions: 0.7≤x≤0.8, 0.04≤y≤0.1, 0.1≤z≤0.19, and x+y+z=1, 0.001≤a≤0.005, according to the element ratio in the chemical formula, the components are mixed with raw materials in a proportion, wherein high vanadium alloy and trace Ce source material are used as raw materials, and the purity of the raw materials used to prepare the high vanadium alloy is ≥99.9wt%; the Cr in the mixed raw materials is excessive by 10-12wt.%; through a vacuum arc melting method, the mixed raw materials are placed in an arc melting furnace, after vacuuming, high-purity argon gas is introduced, and after flipping and remelting at least 5 times under the condition of argon protection, the prepared vanadium-based hydrogen storage alloy is obtained. The vanadium-based hydrogen storage alloy is prepared by arc melting a high-vanadium alloy and a trace amount of Ce, so that Ce oxidizes itself during the melting process to reduce the oxidation of the vanadium-based alloy, thereby improving the alloy's oxidation resistance without reducing the alloy's hydrogen storage capacity, thereby obtaining an easily activated high-capacity vanadium-based hydrogen storage alloy.

[0017] Preferably, the high vanadium alloy is at least one of a V-Ti alloy, a V-Cr alloy or a V-Ti-Cr alloy.

[0018] Preferably, during vacuum arc melting, after evacuation, the vacuum degree in the induction melting furnace is ≤5.0×10 -3 Pa.

[0019] Preferably, during vacuum arc melting, the steps of evacuating and introducing high-purity argon gas can be repeated 2-4 times. After evacuating, the vacuum degree in the induction melting furnace is ≤4.0×10 -3 Pa.

[0020] Compared with the prior art, the present invention has the following obvious outstanding substantive features and significant advantages:

[0021] 1. The easily activated high-capacity vanadium-based hydrogen storage alloy provided by the present invention has excellent hydrogen storage performance, can be activated at ≤80°C, has a hydrogen absorption capacity of ≥2.40% at 25°C, and a capacity retention rate of ≥90% after 1000 cycles of hydrogen absorption and desorption;

[0022] 2. The easily activated high-capacity vanadium-based hydrogen storage alloy provided by the present invention has a simple component design, and the difficulty in activating the vanadium-based alloy can be solved by adding only a trace amount of Ce without affecting its cycle stability. At the same time, due to the low content of Ce added, the hydrogen storage capacity of the alloy will not be reduced;

[0023] 3. The present invention provides an easily activated high-capacity vanadium-based hydrogen storage alloy with a simple preparation process and excellent hydrogen storage performance, which is suitable for large-scale production and commercial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is V in Example 1 of the present invention 78 Ti6Cr 16 Ce 0.2 X-ray diffraction pattern of the alloy.

[0025] Figure 2 is V in Example 1 of the present invention 78 Ti6Cr 16 Ce 0.2 Activation curves of the alloys.

[0026] Figure 3 is V in Example 1 of the present invention 78 Ti6Cr 16 Ce 0.2 PCT curve of the alloy.

[0027] Figure 4 is V in Example 1 of the present invention 78 Ti6Cr 16 Ce 0.2Cyclic performance curve of the alloy.

[0028] Figure 5 is V in Example 2 of the present invention 75 Ti6Cr 19 Ce 0.2 V in alloy and comparative example 75 Ti6Cr 19 First activation curve of the alloy. DETAILED DESCRIPTION

[0029] To facilitate understanding of the present invention, the above scheme is further described below in conjunction with specific embodiments. The following embodiments are only exemplary to illustrate and explain the present invention and should not be construed as limiting the scope of protection of the present invention. Preferred embodiments of the present invention are described in detail as follows:

[0030] Example 1

[0031] This embodiment provides an easily activated high-capacity vanadium-based hydrogen storage alloy, whose chemical formula is V 78 Ti6Cr 16 Ce 0.2 .

[0032] The method for preparing the easily activated high-capacity vanadium-based hydrogen storage alloy in this embodiment has the chemical formula of the easily activated high-capacity vanadium-based hydrogen storage alloy as follows: 78 Ti6Cr 16 Ce 0.2 The preparation method is as follows: the raw materials are mixed according to the proportion of elements in the chemical formula and placed in a vacuum arc melting furnace. After vacuuming, high-purity argon is introduced, and the target alloy is obtained by remelting 5 times and then cooling. High-vanadium alloy and trace Ce raw materials are used as raw materials, and the purity of the raw materials is 99.9wt%, and the raw material Cr is 10wt.% excessive. The high-vanadium alloy is V-Ti-Cr alloy, and the Ce raw material is metal Ce. The steps of vacuuming and introducing high-purity argon are repeated 3 times, and the vacuum degree in the furnace is ≤4.0×10 -3 Pa.

[0033] Experimental test analysis:

[0034] Example 1 Preparation of V 78 Ti6Cr 16 Ce 0.2 The alloy is mainly composed of BCC phase and a small amount of CeO2 phase, such as Figure 1 The alloy was vacuumed at 80℃ for 2h, and the sample was completely activated. Figure 2 The activated sample was tested for hydrogen absorption kinetics at 25°C and 4.5MPa H2, and the sample absorbed 2.47wt.% hydrogen in 200s. Figure 3As shown in FIG. 1 , the activated sample was subjected to a PCT test at 25°C and 7MPa hydrogen pressure, and the maximum hydrogen absorption of the sample reached 2.64wt.%. The activated sample was subjected to a hydrogen absorption and desorption cycle test at 25°C and 4.5MPa H2, as shown in FIG. Figure 4 As shown in the figure, after 1000 cycles of hydrogen absorption and desorption, the capacity retention rate reaches 90%. These results show that the alloy is easy to activate, has high capacity, good cycle stability, and is suitable for commercial applications. In this embodiment, a high vanadium alloy and a trace amount of Ce are prepared by an arc melting method, so that Ce oxidizes itself during the melting process to reduce the oxidation of the vanadium-based alloy, thereby improving the alloy's antioxidant capacity without reducing the alloy's hydrogen storage capacity, thereby obtaining an easily activated high-capacity vanadium-based hydrogen storage alloy.

[0035] Example 2

[0036] This embodiment provides an easily activated high-capacity vanadium-based hydrogen storage alloy, whose chemical formula is V 75 Ti6Cr 19 Ce 0.2 .

[0037] This embodiment provides a method for preparing an easily activated high-capacity vanadium-based hydrogen storage alloy, wherein the composition of the vanadium-based hydrogen storage alloy to be prepared is: 75 Ti6Cr 19 Ce 0.2 , the excess Cr in the mixed raw material is 10wt.%, and other preparation conditions are the same as those in Example 1.

[0038] Experimental test analysis:

[0039] Example 2 Preparation of V 75 Ti6Cr 19 Ce 0.2 The alloy is mainly composed of BCC phase and a small amount of CeO2 phase. Figure 5 As shown in the figure, the alloy can be activated by vacuuming at 80℃ for 2h. The sample after activation absorbs 2.27wt.% of hydrogen in 10 minutes at 25℃ and 4.5MPa H2, and the hydrogen absorption reaches 90% of the maximum hydrogen absorption in 200s. The activated sample is subjected to a dehydrogenation PCT test after being completely hydrogenated to saturation at 25℃ and 7MPaH2, and the maximum hydrogen absorption of the sample reaches 2.43wt.%. These results show that the alloy is easy to activate, has high capacity and good cycle stability, and is suitable for large-scale production and commercial application.

[0040] Example 3

[0041] This embodiment provides an easily activated high-capacity vanadium-based hydrogen storage alloy, whose chemical formula is V 80 Ti6Cr 14 Ce 0.2 .

[0042] This embodiment provides a method for preparing an easily activated high-capacity vanadium-based hydrogen storage alloy. The composition of the prepared vanadium-based hydrogen storage alloy is: 80 Ti6Cr 14 Ce 0.2 , other preparation conditions are the same as those in Example 1.

[0043] Experimental test analysis:

[0044] Example 3 Preparation of V 80 Ti6Cr 14 Ce 0.2 The alloy is mainly composed of BCC phase and a small amount of CeO2 phase. The alloy can be activated by vacuuming at 80℃ for 2h. The hydrogen absorption of the activated sample reached 2.41wt.% in 200s at 25℃ and 4.5MPa H2, and the hydrogen absorption reached 90% of the maximum hydrogen absorption in 200s. After the activated sample was completely hydrogenated to saturation at 25℃ and 7MPa H2, a dehydrogenation PCT test was carried out, and the maximum hydrogen absorption of the sample reached 2.60wt.%. These results show that the alloy is easy to activate, has high capacity and good cycle stability, and is suitable for large-scale production and commercial application.

[0045] Comparative Example

[0046] In the comparative example, a vanadium-based hydrogen storage alloy and a preparation method thereof are provided, wherein the alloy composition is: V 75 Ti6Cr 19 , other preparation conditions are the same as those in Example 2.

[0047] Experimental test analysis:

[0048] Comparative Example Preparation of V 75 Ti6Cr 19 The alloy is mainly composed of BCC phase. Figure 5 As shown in the figure, the first hydrogen absorption rate and hydrogen absorption capacity of the alloy at 80°C and 7MPaH2 are significantly lower than those of the alloy with Ce added, and the alloy is still not fully activated after three hydrogen absorption and desorption cycles, which is not conducive to practical application. Its maximum hydrogen absorption capacity is lower than that of the alloy described in the present invention. The reason should be that the sample is partially oxidized during the smelting process due to the lack of Ce element, resulting in poor activation performance and hydrogen absorption capacity.

[0049] In summary, the above-mentioned embodiments 1-3 provide easily activated high-capacity vanadium-based hydrogen storage alloys and preparation methods thereof. The general composition formula of the alloy is: V x Ti y Cr z Ce a, where 0.75≤x≤0.80, y=0.06, 0.14≤z≤0.19, and x+y+z=1, a=0.002. The preparation method adopts a vacuum arc melting furnace, and the target alloy is obtained by turning over and remelting at least 5 times under the protection of high-purity argon gas and then cooling. A small amount of Ce element prevents the alloy from being locally oxidized during the smelting process, and avoids the problem of excessive rare earth elements reducing the hydrogen absorption capacity, so that the alloy obtains a high hydrogen storage capacity while improving the activation performance. In summary, the advantage of the above-mentioned embodiment of the present invention is that the difficulty in activating V-based alloys and the problem of excessive rare earth elements reducing the hydrogen absorption amount can be solved by adding only a small amount of Ce, and a V-based hydrogen storage alloy with high capacity and high cycle stability can be obtained, and the preparation process is simple, which is suitable for large-scale production and commercial application.

[0050] The above describes the embodiments of the present invention in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments. Various changes can be made according to the purpose of the invention. Any changes, modifications, substitutions, combinations or simplifications made according to the spirit and principle of the technical solution of the present invention should be equivalent replacement methods. As long as they meet the purpose of the invention and do not deviate from the technical principles and inventive concepts of the present invention, they belong to the protection scope of the present invention.

Claims

1. An easily activated high-capacity vanadium-based hydrogen storage alloy, characterized in that: The general chemical formula of its alloy composition is: V x Ti y Cr z Ce a , and the general chemical formula satisfies the conditions: 0.7≤x≤0.8, 0.04≤y≤0.1, 0.1≤z≤0.19, and x+y+z=1, 0.001≤a≤0.

005.

2. The easily activated high-capacity vanadium-based hydrogen storage alloy according to claim 1, characterized in that: The alloy crystals mainly have a body-centered cubic (BCC) structure.

3. The easily activated high-capacity vanadium-based hydrogen storage alloy according to claim 2, characterized in that: The main phase of the alloy crystal is BCC phase, and also includes a small amount of CeO2 phase.

4. The easily activated high-capacity vanadium-based hydrogen storage alloy according to claim 1, characterized in that: The general chemical formula satisfies the following conditions: 0.75≤x≤0.80, 0.05≤y≤0.07, 0.14≤z≤0.19, and x+y+z=1, 0.001≤a≤0.

003.

5. The easily activated high-capacity vanadium-based hydrogen storage alloy according to claim 1, characterized in that: After vacuuming at 80° C. for 120 minutes, the vanadium-based hydrogen storage alloy can be fully activated by absorbing and desorbing hydrogen no more than three times at 25° C. and H 2 of not less than 4.5 MPa.

6. The easily activated high-capacity vanadium-based hydrogen storage alloy according to claim 1, characterized in that: Under the conditions of 25° C. and H 2 of not less than 4.5 MPa, the maximum hydrogen absorption capacity of the vanadium-based hydrogen storage alloy is ≥2.27wt%, and the hydrogen storage capacity retention rate after 1000 cycles of hydrogen absorption and desorption is ≥90%.

7. The easily activated high-capacity vanadium-based hydrogen storage alloy according to claim 6, characterized in that: Under the conditions of 25° C. and H 2 of not less than 7 MPa, the maximum hydrogen absorption capacity of the vanadium-based hydrogen storage alloy is ≥2.43wt%, and the hydrogen storage capacity retention rate after 1000 cycles of hydrogen absorption and desorption is ≥90%.

8. A method for preparing the easily activated high-capacity vanadium-based hydrogen storage alloy according to claim 1, characterized in that: The steps include: The chemical formula of the vanadium-based hydrogen storage alloy prepared according to the target is: x Ti y Cr z Ce a , and the chemical formula satisfies the conditions: 0.7≤x≤0.8, 0.04≤y≤0.1, 0.1≤z≤0.19, and x+y+z=1, 0.001≤a≤0.005, according to the element ratio in the chemical formula, the components are mixed with raw materials in a proportion, wherein high vanadium alloy and trace Ce source material are used as raw materials, and the purity of the raw materials used to prepare the high vanadium alloy is ≥99.9wt%; the Cr in the mixed raw materials is excessive by 10-12wt.%; through a vacuum arc melting method, the mixed raw materials are placed in an arc melting furnace, after vacuuming, high-purity argon gas is introduced, and after flipping and remelting at least 5 times under the condition of argon protection, the prepared vanadium-based hydrogen storage alloy is obtained.

9. The method for preparing the easily activated high-capacity vanadium-based hydrogen storage alloy according to claim 8, characterized in that: After vacuuming, the vacuum degree in the induction melting furnace is ≤5.0×10 -3 Pa.

10. The method for preparing the easily activated high-capacity vanadium-based hydrogen storage alloy according to claim 8, characterized in that: The steps of evacuating the vacuum and introducing high-purity argon gas can be repeated 2-4 times. After evacuating the vacuum, the vacuum degree in the induction melting furnace is ≤4.0×10 -3 Pa.

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