Vanadium-series solid hydrogen storage material and preparation method thereof

Abstract

The invention discloses a vanadium-series solid hydrogen storage material and a preparation method thereof. The vanadium-series solid hydrogen storage material is prepared from the following raw materials in percentage by mass: 5-14% of Ti, 3.5-9% of Cr, 1.5-4% of Ni, 2-8% of Mn, 6-14% of metallized modified carbon nanotubes and the balance of V, the metallization modified carbon nano tube is prepared by the following steps: S1, treating a carbon nano tube with alkali and acid in sequence to obtain a pretreated carbon nano tube; s2, loading carbon dots on the pretreated carbon nanotubes to obtain modified carbon nanotubes; and S3, depositing iron and cobalt on the modified carbon nanotube through chemical plating, and carrying out metallization treatment to obtain the metallized modified carbon nanotube. According to the vanadium-series solid hydrogen storage material provided by the invention, the metallized modified carbon nanotubes are added into a conventional vanadium-series hydrogen storage alloy system as a modifier, so that the hydrogen absorption and desorption amount can be effectively increased, and the cycle stability can be improved.

Description

Technical Field

[0001] This invention relates to the field of solid hydrogen storage materials, and in particular to a vanadium-based solid hydrogen storage material and its preparation method. Background Technology

[0002] Hydrogen energy is a readily available, clean, low-carbon, flexible, efficient, and widely applicable secondary energy source, serving as a crucial vehicle for achieving green and low-carbon transformation in energy consumption. One of the key challenges of hydrogen energy is the difficulty in achieving safe and efficient storage and transportation. Current traditional storage methods include high-pressure gaseous storage and transportation, and cryogenic liquid storage and transportation. Solid-state hydrogen storage, due to its high safety, high volumetric density, and excellent cycle performance, is a very promising storage and transportation method.

[0003] V-based hydrogen storage alloys belong to the BCC-type solid-state hydrogen storage alloys. Due to their high theoretical hydrogen storage capacity and low hydrogen absorption / desorption temperatures, they are among the most promising hydrogen storage materials. However, traditional V-based hydrogen storage alloys can only reversibly release a portion of hydrogen at room temperature and pressure, resulting in a low effective hydrogen absorption capacity. After pure V absorbs hydrogen, only about half of the hydrogen can be reversibly released, with an effective hydrogen absorption capacity of only about 1.96%. Furthermore, conventional V-based hydrogen storage alloys require high-temperature activation before use, which poses difficulties and limitations for their practical applications. In addition, during use, V and the metals such as Ti often added to V-based hydrogen storage alloys are prone to surface oxidation. The resulting oxides can hinder hydrogen absorption and release, leading to a significant decrease in the cycle stability of V-based hydrogen storage alloys. These shortcomings limit the application of V-based hydrogen storage alloys.

[0004] Patent CN119530626A discloses an easily activated, high-capacity vanadium-based hydrogen storage alloy and its preparation method. This method achieves easily activated, high-capacity, and well-cycled hydrogen storage alloys by adding trace amounts of Ce, making it suitable for large-scale production and commercial applications. The small amount of Ce prevents localized oxidation during the smelting process and avoids the problem of excessive rare earth elements reducing hydrogen absorption capacity, thus achieving high hydrogen storage capacity while improving activation performance. However, it does not effectively address the issue of easy oxidation of vanadium and other metals such as Ti, which are commonly added to vanadium-based hydrogen storage alloys, during use.

[0005] Patent CN113502424B discloses a low-temperature activated vanadium-based hydrogen storage alloy, its preparation method, and its applications. By adding rare earth element RE and controlling its content, the prepared vanadium-based hydrogen storage alloy can be directly activated at low temperatures while ensuring high hydrogen absorption and release capabilities, eliminating the need for high-temperature or high-pressure activation processes. Furthermore, the preparation method is simple, rapid, and effective. However, it does not adequately address the issue of easy oxidation of vanadium (V) and other metals such as titanium (Ti) commonly added to vanadium-based hydrogen storage alloys during use, and the effective hydrogen release capability still needs further improvement.

[0006] Therefore, it is now necessary to improve existing technologies to provide more reliable solutions. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a vanadium-based solid hydrogen storage material and its preparation method, addressing the shortcomings of the prior art.

[0008] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a vanadium-based solid hydrogen storage material, the raw materials for its preparation comprising, by mass percentage: Ti 5-14%, Cr 3.5-9%, Ni 1.5-4%, Mn 2-8%, metallized modified carbon nanotubes 6-14%, the remainder being V; The metallized modified carbon nanotubes were prepared through the following steps: S1. Carbon nanotubes are treated sequentially with alkali and acid to obtain pretreated carbon nanotubes; S2. Load carbon dots onto pretreated carbon nanotubes to obtain modified carbon nanotubes; S3. Iron and cobalt are deposited on the modified carbon nanotubes by chemical plating to perform metallization treatment, thereby obtaining metallized modified carbon nanotubes.

[0009] Preferably, step S1 specifically includes: Carbon nanotubes were added to a sodium hydroxide solution, heated under reflux, filtered, and the solid product was washed with deionized water until neutral. Then, the solid product was added to a mixed solution consisting of 20-30 wt% hydrogen peroxide solution and 60-68 wt% nitric acid solution, heated under stirring under reflux, filtered, and the solid product was washed with deionized water until neutral. The solid product was then dried under vacuum to obtain pretreated carbon nanotubes.

[0010] Preferably, step S1 specifically includes: Add 1-4g of carbon nanotubes to 100-400mL of 1-3mol / L sodium hydroxide solution, heat under reflux at 65-80℃ for 1.5-6h, filter, and wash the solid product with deionized water until neutral; then add to a mixed solution consisting of 25-100mL of 20-30wt% hydrogen peroxide solution and 50-200mL of 60-68wt% nitric acid, stir under reflux at 50-70℃ for 2-8h, filter, wash the solid product with deionized water until neutral, and vacuum dry to obtain pretreated carbon nanotubes.

[0011] Preferably, step S2 specifically includes: S2-1. Take pretreated carbon nanotubes and La(NO3)3·6H2O and add them to deionized water. Disperse them by ultrasonication to obtain precursor solution 1. S2-2. Add glucose, L-ascorbic acid, NdCl3, and N,N-diethyl-p-phenylenediamine sulfate to deionized water and stir. Add the resulting mixture to precursor solution 1 while stirring, and stir to obtain precursor solution 2. S2-3. Transfer the precursor solution 2 into the reactor and react at 170-230℃ for 12-24h. After the reaction is completed, cool to room temperature, centrifuge, filter, wash the solid product with deionized water, and vacuum dry to obtain modified carbon nanotubes.

[0012] Preferably, step S2 specifically includes: S2-1. Take 0.5-2g of pretreated carbon nanotubes and 0.1-0.43g of La(NO3)3·6H2O and add them to 75-300mL of deionized water. Disperse by ultrasonication for 0.5-2h to obtain precursor solution 1. S2-2: Add 0.36-1.44g glucose, 0.175-0.7g L-ascorbic acid, 0.063-0.25g NdCl3, and 0.131-0.524g N,N-diethyl-p-phenylenediamine sulfate to 50-200mL of deionized water and stir for 10-40min. Add the resulting mixture to precursor solution 1 while stirring, and keep stirring for 15-60min to obtain precursor solution 2. S2-3. Transfer the precursor solution 2 into the reactor and react at 170-230℃ for 12-24h. Cool to room temperature, centrifuge, filter, wash the solid product with deionized water, and vacuum dry to obtain modified carbon nanotubes.

[0013] Preferably, step S3 specifically includes: S3-1. Modified carbon nanotubes are sensitized by stannous chloride sensitizing solution and activated by palladium chloride activating solution to obtain activated modified carbon nanotubes. S3-2. Add the activated modified carbon nanotubes to deionized water and disperse them by ultrasonication. Add the resulting dispersion to the plating solution while stirring. After ultrasonic dispersion, apply the plating solution under heating. After plating is completed, filter the solution, wash with deionized water until neutral, and dry to obtain metallized modified carbon nanotubes.

[0014] Preferably, step S3 specifically includes: S3-1. Take 0.5-2g of modified carbon nanotubes and add them to 250-1000mL of stannous chloride sensitization solution. Stir at room temperature for 30-90min. Filter and wash with deionized water until neutral. Then add it to 250-1000mL of palladium chloride activation solution. Stir at room temperature for 30-90min. Centrifuge and wash with deionized water until neutral to obtain activated modified carbon nanotubes. The stannous chloride sensitizing solution consists of SnCl2 10-18 g / L and HCl 0.3-1 mol / L; the palladium chloride activating solution consists of PdCl 1.5-5 g / L and HCl 0.05-0.2 mol / L. S3-2. Add the activated modified carbon nanotubes to 50-200 mL of deionized water and ultrasonically disperse for 0.5-2 h. Add the resulting dispersion to 450-1800 mL of plating solution under stirring. After ultrasonically dispersing for 10-40 min, plate at 75-90℃ for 0.5-2 h. Filter, wash with deionized water until neutral, and vacuum dry to obtain metallized modified carbon nanotubes. The plating solution consists of: CoSO4 20-30 g / L, FeSO4 10-25 g / L, NaH2PO2 22-35 g / L, sodium citrate 10-18 g / L, and lead nitrate 0.02-0.08 g / L.

[0015] Preferably, the metallized modified carbon nanotubes are prepared by the following steps: S1. Preparation of pretreated carbon nanotubes: 2g of carbon nanotubes were added to 200mL of 1.5mol / L sodium hydroxide solution and heated under reflux at 75℃ for 3h. After filtration, the solid product was washed with deionized water until neutral. Then, it was added to a mixed solution consisting of 50mL of 25wt% hydrogen peroxide solution and 100mL of 65wt% nitric acid solution and stirred under reflux at 60℃ for 4h. After filtration, the solid product was washed with deionized water until neutral and dried under vacuum at 90℃ for 12h to obtain pretreated carbon nanotubes. S2. Preparation of modified carbon nanotubes: S2-1. Take 1g of pretreated carbon nanotubes and 0.215g of La(NO3)3·6H2O and add them to 150mL of deionized water. Disperse by ultrasonication for 1h to obtain precursor solution 1. S2-2, Add 0.72g glucose, 0.35g L-ascorbic acid, 0.125g NdCl3, and 0.262g N,N-diethyl-p-phenylenediamine sulfate to 100mL of deionized water and stir for 20min. Add the resulting mixture 1 to precursor solution 1 while stirring and keep stirring for 30min to obtain precursor solution 2. S2-3. Transfer the precursor solution 2 into the reactor, react at 190℃ for 16h, cool to room temperature, centrifuge, filter, wash the solid product with deionized water, and vacuum dry at 90℃ for 12h to obtain modified carbon nanotubes. S3. Preparation of metallized modified carbon nanotubes: S3-1. Take 1g of modified carbon nanotubes and add them to 500mL of stannous chloride sensitization solution. Stir at room temperature for 45min, filter, wash with deionized water until neutral, and then add to 500mL of palladium chloride activation solution. Stir at room temperature for 45min, centrifuge, wash with deionized water until neutral to obtain activated modified carbon nanotubes. The stannous chloride sensitizing solution consisted of SnCl2 12 g / L and HCl 0.75 mol / L; the palladium chloride activating solution consisted of PdCl 2.5 g / L and HCl 0.1 mol / L. S3-2. Add the activated modified carbon nanotubes to 100 mL of deionized water and ultrasonically disperse for 1 h. Add the resulting dispersion to 900 mL of plating solution under stirring. After ultrasonically dispersing for 20 min, plate at 85 °C for 1 h. Filter, wash with deionized water until neutral, and vacuum dry at 90 °C overnight to obtain metallized modified carbon nanotubes. The plating solution consists of: CoSO4 25g / L, FeSO4 18g / L, NaH2PO2 30g / L, sodium citrate 15g / L, and lead nitrate 0.05g / L.

[0016] The present invention also provides a method for preparing the vanadium-based solid hydrogen storage material as described above, comprising the following steps: adding V powder, Ti powder, Cr powder, Ni powder, Mn powder and metallized modified carbon nanotubes into a ball mill according to the raw material ratio, and ball milling under inert gas protection to obtain the vanadium-based solid hydrogen storage material.

[0017] Preferably, the preparation method of the vanadium-based solid hydrogen storage material includes the following steps: adding V powder, Ti powder, Cr powder, Ni powder, Mn powder and metallized modified carbon nanotubes into a ball mill according to the raw material ratio, and ball milling under nitrogen protection to obtain the vanadium-based solid hydrogen storage material. The ball milling speed is 150-800 rpm, the ball milling time is 60-240 min, and the ball-to-material ratio is controlled at (20~35):1.

[0018] The beneficial effects of this invention are: In the vanadium-based solid hydrogen storage material improved by this invention, metallized modified carbon nanotubes are added as a modifier to the conventional vanadium-based hydrogen storage alloy system, which can effectively increase the hydrogen absorption and desorption capacity and improve the cycle stability.

[0019] In this invention, by coating the surface of carbon nanotubes with a CoFe alloy, the wettability between the carbon nanotubes and the V-based hydrogen storage alloy system can be greatly improved, enabling uniform dispersion. Co has good adhesion and easily forms a strong coating layer on the carbon nanotubes. Simultaneously, Co and Fe entering the alloy system also play the following roles: Fe can lower the formation energy barrier of hydrides, reduce the stability of gold hydrides, promote hydrogen adsorption, and improve hydrogen storage performance; while Co can increase the cycle life of the alloy and improve hydrogen desorption efficiency, shortening the hydrogen saturation time.

[0020] The carbon dots in this invention effectively inherit the reducing properties of precursors glucose and L-ascorbic acid, enhancing the excellent antioxidant properties in the alloy system, thereby reducing the oxidation of metals such as V and Ti, improving the cycle stability of the hydrogen storage alloy, and enhancing its activity. On the other hand, the carbon dots introduce defects and active sites at the metal / carbon interface between the carbon nanotubes and the alloy, thereby enhancing the catalytic performance of the carbon nanotubes in the hydrogen absorption and desorption process. Furthermore, through the loading of carbon nanotubes and metallization treatment, uniform dispersion of carbon dots in the hydrogen storage alloy can be achieved simultaneously. Attached Figure Description

[0021] Figure 1 The diagram shows the structure of the structure.

[0022] Figure 2 XRD pattern of the metallized modified carbon nanotubes prepared in Example 1;

[0023] Figure 3 The results are the reducibility test results of the modified carbon nanotubes prepared in Example 1 and Comparative Example 6; Figure 4 Hydrogen absorption curves of the hydrogen storage materials prepared in Example 1 and Comparative Examples 1-8; Figure 5 The test results of the maximum hydrogen absorption capacity of the hydrogen storage materials prepared in the examples and comparative examples; Figure 6 The effective hydrogen release test results are for the hydrogen storage materials prepared in the examples and comparative examples. Figure 7 The results show the capacity retention test results of the hydrogen storage materials prepared in the examples and comparative examples. Detailed Implementation

[0024] The present invention will be further described in detail below with reference to embodiments, so that those skilled in the art can implement it based on the description.

[0025] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0026] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials and reagents used in the following examples are commercially available. For examples where specific conditions are not specified, conventional conditions or conditions recommended by the manufacturer are followed. For reagents or instruments whose manufacturers are not specified, they are all commercially available products.

[0027] This invention provides a vanadium-based solid hydrogen storage material, the raw materials for which are prepared by weight percentage include: Ti 5-14%, Cr 3.5-9%, Ni 1.5-4%, Mn 2-8%, metallized modified carbon nanotubes 6-14%, the remainder being V; Metallized modified carbon nanotubes were prepared through the following steps: S1. Carbon nanotubes are treated sequentially with alkali and acid to obtain pretreated carbon nanotubes: Add 1-4g of carbon nanotubes to 100-400mL of 1-3mol / L sodium hydroxide solution, heat under reflux at 65-80℃ for 1.5-6h, filter, and wash the solid product with deionized water until neutral; then add to a mixed solution consisting of 25-100mL of 20-30wt% hydrogen peroxide solution and 50-200mL of 60-68wt% nitric acid, stir under reflux at 50-70℃ for 2-8h, filter, wash the solid product with deionized water until neutral, and vacuum dry to obtain pretreated carbon nanotubes.

[0028] S2. Loading carbon dots onto pretreated carbon nanotubes to obtain modified carbon nanotubes: S2-1. Take 0.5-2g of pretreated carbon nanotubes and 0.1-0.43g of La(NO3)3·6H2O and add them to 75-300mL of deionized water. Disperse by ultrasonication for 0.5-2h to obtain precursor solution 1. S2-2: Add 0.36-1.44g glucose, 0.175-0.7g L-ascorbic acid, 0.063-0.25g NdCl3, and 0.131-0.524g N,N-diethyl-p-phenylenediamine sulfate to 50-200mL of deionized water and stir for 10-40min. Add the resulting mixture to precursor solution 1 while stirring, and keep stirring for 15-60min to obtain precursor solution 2. S2-3. Transfer the precursor solution 2 into the reactor and react at 170-230℃ for 12-24h. Cool to room temperature, centrifuge, filter, wash the solid product with deionized water, and vacuum dry to obtain modified carbon nanotubes.

[0029] S3. Metallization treatment is performed by depositing iron and cobalt on the modified carbon nanotubes through chemical plating to obtain metallized modified carbon nanotubes: S3-1. Take 0.5-2g of modified carbon nanotubes and add them to 250-1000mL of stannous chloride sensitization solution. Stir at room temperature for 30-90min. Filter and wash with deionized water until neutral. Then add it to 250-1000mL of palladium chloride activation solution. Stir at room temperature for 30-90min. Centrifuge and wash with deionized water until neutral to obtain activated modified carbon nanotubes. The stannous chloride sensitizing solution consists of SnCl2 10-18 g / L and HCl 0.3-1 mol / L; the palladium chloride activating solution consists of PdCl 1.5-5 g / L and HCl 0.05-0.2 mol / L. S3-2. Add the activated modified carbon nanotubes to 50-200 mL of deionized water and ultrasonically disperse for 0.5-2 h. Add the resulting dispersion to 450-1800 mL of plating solution under stirring. After ultrasonically dispersing for 10-40 min, plate at 75-90℃ for 0.5-2 h. Filter, wash with deionized water until neutral, and vacuum dry to obtain metallized modified carbon nanotubes. The plating solution consists of: CoSO4 20-30 g / L, FeSO4 10-25 g / L, NaH2PO2 22-35 g / L, sodium citrate 10-18 g / L, and lead nitrate 0.02-0.08 g / L.

[0030] This invention also provides a method for preparing the above-mentioned vanadium-based solid hydrogen storage material, comprising the following steps: adding V powder, Ti powder, Cr powder, Ni powder, Mn powder and metallized modified carbon nanotubes into a ball mill according to the raw material ratio, and ball milling under nitrogen protection to obtain the vanadium-based solid hydrogen storage material, wherein the ball milling speed is 150-800 rpm, the ball milling time is 60-240 min, and the ball-to-material ratio is controlled at (20~35):1.

[0031] In this invention, by adding metallized modified carbon nanotubes as a modifier to a conventional vanadium-based hydrogen storage alloy system, the hydrogen absorption and desorption capacity can be effectively increased, and the cycle stability can be improved. The preparation and mechanism of action of the metallized modified carbon nanotubes are described in detail below to facilitate understanding of this invention. I. Preparation Mechanism

[0032] First, carbon nanotubes are pretreated by alkali washing and acid washing to purify them. At the same time, strong acid oxidation introduces abundant carboxyl groups on the surface of the carbon nanotubes, which facilitates the subsequent carbon dot loading process. Then, using pretreated carbon nanotubes as a carrier, and glucose, L-ascorbic acid, and N,N-diethyl-p-phenylenediamine sulfate as carbon sources for the carbon dots, and NdCl3 as a metal-doped neodymium source, a reducing carbon dot was synthesized in situ on the carrier via a one-pot hydrothermal method, resulting in modified carbon nanotubes. In this process, the pretreated carbon nanotubes were first reacted with La...3+ Mixed, La 3+ It coordinates with the carboxyl groups on the surface of pretreated carbon nanotubes, and then mixes with carbon dot raw materials. Glucose, L-ascorbic acid, and N,N-diethyl-p-phenylenediamine sulfate react with La through their oxygen-containing functional groups. 3+ The coordination of Nd and Nd leads to their abundant and uniform binding to the surface of pretreated carbon nanotubes, while Nd 3+ La binds to pretreated carbon nanotubes through coordination with carboxyl groups on the surface of carbon nanotubes and oxygen-containing functional groups in the aforementioned raw materials. 3+ and Nd 3+ Throughout this process, the Overseas Chinese Federation played a crucial role, ensuring that carbon dot raw materials were abundantly and uniformly bonded to the surface of pretreated carbon nanotubes, thus creating favorable conditions for in-situ loading of carbon dots onto the pretreated carbon nanotubes. Subsequently, under high-temperature hydrothermal reaction conditions, La... 3+ and Nd 3+ The corresponding oxides are formed, which covalently bind the carbon dots to the pretreated carbon nanotubes.

[0033] Finally, using CoSO4 and FeSO4 as Co and Fe sources respectively, a Co-Fe alloy was coated on the surface of the modified carbon nanotubes using a chemical plating process to achieve metallization modification of the carbon nanotubes and obtain metallized modified carbon nanotubes. II. Mechanism of Action

[0034] V-based hydrogen storage alloys belong to the BCC-type solid-state hydrogen storage alloys. Due to their high theoretical hydrogen storage capacity and low hydrogen absorption / desorption temperatures, they are among the most promising hydrogen storage materials. However, traditional V-based hydrogen storage alloys can only reversibly release a portion of hydrogen at room temperature and pressure, resulting in a low effective hydrogen absorption capacity. After pure V absorbs hydrogen, only about half of the hydrogen can be reversibly released, with an effective hydrogen absorption capacity of only about 1.96%. Furthermore, conventional V-based hydrogen storage alloys require high-temperature activation before use, which poses difficulties and limitations for their practical applications. In addition, during use, V and the metals such as Ti often added to V-based hydrogen storage alloys are prone to surface oxidation. The resulting oxides can hinder hydrogen absorption and release, leading to a significant decrease in the cycle stability of V-based hydrogen storage alloys. These defects limit the application of V-based hydrogen storage alloys. In this invention, the addition of metallized modified carbon nanotubes can effectively improve the above-mentioned defects of V-based hydrogen storage alloys, thereby improving their hydrogen storage capacity and hydrogen absorption / desorption performance.

[0035] 1. The role of carbon nanotubes: (1) Carbon nanotubes are a material with high thermal conductivity, which can improve the thermal conductivity efficiency during hydrogen absorption and desorption, and improve the hydrogen absorption and desorption kinetics of hydrogen storage alloys. Related studies have shown that carbon nanotubes have excellent catalytic performance for hydrogen absorption and desorption processes of hydrogen storage alloys: through their unique internal structure, they can provide hydrogen diffusion channels, shorten the hydrogen diffusion distance, and increase the diffusion rate. Carbon nanotubes are prone to segregation at grain boundaries, which increases the diffusion of hydrogen at grain boundaries (Wu CZ, Wang P, Yao X, et al. Effect of carbon / noncarbon addition on hydrogen storage behaviors of magnesium hydride[J]. Journal of Alloys and Compounds, 2006, 414:259-264.DOI:10.1016 / J.JALLCOM.2005.07.021.) (2) Carbon nanotubes have a nanoscale tubular structure, abundant nanoscale pores and high specific surface area. Theoretically, the hydrogen storage capacity can reach 9.9 wt% (Li Ge. Properties and applications of hydrogen storage carbon nanotube composite materials [J]. Journal of Chengdu Textile College, 2006, 23(1):3.DOI:10.3969 / j.issn.1008-5580.2006.01.010.). Adding them to hydrogen storage alloys can effectively improve the hydrogen storage density.

[0036] However, the metal elements in carbon nanotubes have poor wettability with V-based hydrogen storage alloys, making them prone to agglomeration and hindering uniform dispersion, thus preventing them from fully realizing their reinforcing properties. In this invention, by coating the surface of carbon nanotubes with a CoFe alloy, the wettability between carbon nanotubes and V-based hydrogen storage alloys can be greatly improved, enabling uniform dispersion. Furthermore, Co has good adhesion properties, facilitating the formation of a strong coating layer on the carbon nanotubes. Meanwhile, Co and Fe entering the alloy system can also play the following roles: Fe can reduce the formation energy barrier of hydrides, reduce the stability of gold hydrides, promote hydrogen adsorption, and improve hydrogen storage performance; while Co can improve the cycle life of the alloy, and can improve the hydrogen desorption efficiency and shorten the hydrogen saturation time (Li Duo, Lou Yuwan, Du Junlin, et al. Research progress of vanadium-based hydrogen storage alloys [J]. Materials Reports, 2015, 29(23):6.DOI:10.11896 / j.issn.1005-023X.2015.023.017.).

[0037] 2. The function of carbon dots: The carbon dots in this invention effectively inherit the reducing properties of precursors glucose and L-ascorbic acid, enhancing the alloy system's superior antioxidant properties. This reduces the oxidation of metals such as V and Ti, improves the cycle stability of the hydrogen storage alloy, and enhances its activity. Furthermore, the carbon dots introduce defects and active sites at the metal / carbon interface between the carbon nanotubes and the alloy, thereby strengthening the catalytic performance of the carbon nanotubes in the hydrogen adsorption and desorption processes. Moreover, through the loading of carbon nanotubes and metallization treatment, uniform dispersion of the carbon dots within the hydrogen storage alloy can be achieved simultaneously.

[0038] N,N-diethyl-p-phenylenediamine sulfate in carbon dopants achieves S and N doping. N and S doping can effectively improve carrier mobility, increase electron transfer efficiency, and improve reducing properties. Neodymium doping in carbon dots can act as an electron donor and enhance the activity of functional groups on the carbon dot surface, thereby improving the oxidation resistance of the carbon dots. After the formation of neodymium oxide in the alloy system, the hydrogen bonding ability of the alloy can be optimized, and the hydrogen absorption and desorption kinetics can be improved.

[0039] 3. The function of La: During the preparation process, its cross-linking effect promotes the loading of carbon dots on carbon nanotubes. The rare earth oxides formed under high-temperature hydrothermal reaction can reduce the stability of hydrides in the hydrogen storage alloy system, increase the hydrogen absorption and desorption rate, and improve the hydrogen absorption and desorption kinetics. La has a low free energy and can combine with hydrogen at room temperature, which can reduce the oxide layer on the alloy surface. It plays the role of "window" and "channel" in the hydrogen absorption process, thereby improving the activation performance of the hydrogen storage alloy.

[0040] The above is the general concept of the present invention. Based on this, detailed embodiments and comparative examples are provided below to further illustrate the present invention.

[0041] The following describes some of the raw materials used in the examples and comparative examples: N,N-Diethyl-p-phenylenediamine sulfate, CAS No.: 6283-63-2, Molecular formula C 10 H 16 N2·H2SO4, Shanghai Coleman Reagent Co., Ltd.; Carbon nanotubes, specifically multi-walled carbon nanotubes, with a length of 10-30 μm and a diameter of 10-20 nm, are produced by Jiangsu Xianfeng Nanomaterials Technology Co., Ltd. L-Ascorbic Acid, Jiangsu Caiwei Biotechnology Co., Ltd.; NdCl3, Shanghai Yanbei New Materials Technology Co., Ltd.; La(NO3)3·6H2O, Shanghai Gelin Technology Co., Ltd. Example 1

[0042] A vanadium-based solid hydrogen storage material, the raw materials for its preparation comprising, by mass percentage: Ti 8.5%, Cr 6%, Ni 2.5%, Mn 4%, metallized modified carbon nanotubes 9%, the remainder being V; The preparation method of the vanadium-based solid hydrogen storage material is as follows: V powder, Ti powder, Cr powder, Ni powder, Mn powder (V powder, Ti powder, Cr powder, Ni powder, and Mn powder are all crushed to below 2μm under nitrogen protection) and metallized modified carbon nanotubes are added to a ball mill according to the raw material ratio and ball milled under nitrogen protection to obtain the vanadium-based solid hydrogen storage material. The ball milling speed is 400 rpm, the ball milling time is 120 min, and the ball-to-material ratio is controlled at 30:1.

[0043] Metallized modified carbon nanotubes were prepared through the following steps: S1. Preparation of pretreated carbon nanotubes: 2g of carbon nanotubes were added to 200mL of 1.5mol / L sodium hydroxide solution and heated under reflux at 75℃ for 3h. After filtration, the solid product was washed with deionized water until neutral. Then, it was added to a mixed solution consisting of 50mL of 25wt% hydrogen peroxide solution and 100mL of 65wt% nitric acid solution and stirred under reflux at 60℃ for 4h. After filtration, the solid product was washed with deionized water until neutral and dried under vacuum at 90℃ for 12h to obtain pretreated carbon nanotubes. S2. Preparation of modified carbon nanotubes: S2-1. Take 1g of pretreated carbon nanotubes and 0.215g of La(NO3)3·6H2O and add them to 150mL of deionized water. Disperse by ultrasonication for 1h to obtain precursor solution 1. S2-2, Add 0.72g glucose, 0.35g L-ascorbic acid, 0.125g NdCl3, and 0.262g N,N-diethyl-p-phenylenediamine sulfate to 100mL of deionized water and stir for 20min. Add the resulting mixture 1 to precursor solution 1 while stirring and keep stirring for 30min to obtain precursor solution 2. S2-3. Transfer the precursor solution 2 into the reactor, react at 190℃ for 16h, cool to room temperature, centrifuge, filter, wash the solid product with deionized water, and vacuum dry at 90℃ for 12h to obtain modified carbon nanotubes. S3. Preparation of metallized modified carbon nanotubes: S3-1. Take 1g of modified carbon nanotubes and add them to 500mL of stannous chloride sensitization solution. Stir at room temperature for 45min, filter, wash with deionized water until neutral, and then add to 500mL of palladium chloride activation solution. Stir at room temperature for 45min, centrifuge, wash with deionized water until neutral to obtain activated modified carbon nanotubes. The stannous chloride sensitizing solution consisted of SnCl2 12 g / L and HCl 0.75 mol / L; the palladium chloride activating solution consisted of PdCl 2.5 g / L and HCl 0.1 mol / L. S3-2. Add the activated modified carbon nanotubes to 100 mL of deionized water and ultrasonically disperse for 1 h. Add the resulting dispersion to 900 mL of plating solution under stirring. After ultrasonically dispersing for 20 min, plate at 85 °C for 1 h. Filter, wash with deionized water until neutral, and vacuum dry at 90 °C overnight to obtain metallized modified carbon nanotubes. The plating solution consists of: CoSO4 25g / L, FeSO4 18g / L, NaH2PO2 30g / L, sodium citrate 15g / L, and lead nitrate 0.05g / L.

[0044] Example 2 A vanadium-based solid hydrogen storage material, characterized in that its raw materials, by mass percentage, comprise: Ti 9%, Cr 5.5%, Ni 2.8%, Mn 3.7%, metallized modified carbon nanotubes 9%, the remainder being V; The preparation method of the vanadium-based solid hydrogen storage material is as follows: V powder, Ti powder, Cr powder, Ni powder, Mn powder (V powder, Ti powder, Cr powder, Ni powder, and Mn powder are all crushed to below 2μm under nitrogen protection) and metallized modified carbon nanotubes are added to a ball mill according to the raw material ratio and ball milled under nitrogen protection to obtain the vanadium-based solid hydrogen storage material. The ball milling speed is 400 rpm, the ball milling time is 120 min, and the ball-to-material ratio is controlled at 30:1.

[0045] Metallized modified carbon nanotubes were prepared through the following steps: S1. Preparation of pretreated carbon nanotubes: 2g of carbon nanotubes were added to 200mL of 1.5mol / L sodium hydroxide solution and heated under reflux at 75℃ for 3h. After filtration, the solid product was washed with deionized water until neutral. Then, it was added to a mixed solution consisting of 50mL of 25wt% hydrogen peroxide solution and 100mL of 65wt% nitric acid solution and stirred under reflux at 60℃ for 4h. After filtration, the solid product was washed with deionized water until neutral and dried under vacuum at 90℃ for 12h to obtain pretreated carbon nanotubes. S2. Preparation of modified carbon nanotubes: S2-1. Take 1g of pretreated carbon nanotubes and 0.215g of La(NO3)3·6H2O and add them to 150mL of deionized water. Disperse by ultrasonication for 1h to obtain precursor solution 1. S2-2, Add 0.72g glucose, 0.35g L-ascorbic acid, 0.125g NdCl3, and 0.262g N,N-diethyl-p-phenylenediamine sulfate to 100mL of deionized water and stir for 20min. Add the resulting mixture 1 to precursor solution 1 while stirring and keep stirring for 30min to obtain precursor solution 2. S2-3. Transfer the precursor solution 2 into the reactor, react at 190℃ for 16h, cool to room temperature, centrifuge, filter, wash the solid product with deionized water, and vacuum dry at 90℃ for 12h to obtain modified carbon nanotubes. S3. Preparation of metallized modified carbon nanotubes: S3-1. Take 1g of modified carbon nanotubes and add them to 500mL of stannous chloride sensitization solution. Stir at room temperature for 45min, filter, wash with deionized water until neutral, and then add to 500mL of palladium chloride activation solution. Stir at room temperature for 45min, centrifuge, wash with deionized water until neutral to obtain activated modified carbon nanotubes. The stannous chloride sensitizing solution consisted of SnCl2 12 g / L and HCl 0.75 mol / L; the palladium chloride activating solution consisted of PdCl 2.5 g / L and HCl 0.1 mol / L. S3-2. Add the activated modified carbon nanotubes to 100 mL of deionized water and ultrasonically disperse for 1 h. Add the resulting dispersion to 900 mL of plating solution under stirring. After ultrasonically dispersing for 20 min, plate at 85 °C for 1 h. Filter, wash with deionized water until neutral, and vacuum dry at 90 °C overnight to obtain metallized modified carbon nanotubes. The plating solution consists of: CoSO4 25g / L, FeSO4 18g / L, NaH2PO2 30g / L, sodium citrate 15g / L, and lead nitrate 0.05g / L.

[0046] Example 3 A vanadium-based solid hydrogen storage material, characterized in that its raw materials, by mass percentage, comprise: Ti 8.7%, Cr 6%, Ni 2.5%, Mn 4.2%, metallized modified carbon nanotubes 8.6%, the remainder being V; The preparation method of the vanadium-based solid hydrogen storage material is as follows: V powder, Ti powder, Cr powder, Ni powder, Mn powder (V powder, Ti powder, Cr powder, Ni powder, and Mn powder are all crushed to below 2μm under nitrogen protection) and metallized modified carbon nanotubes are added to a ball mill according to the raw material ratio and ball milled under nitrogen protection to obtain the vanadium-based solid hydrogen storage material. The ball milling speed is 400 rpm, the ball milling time is 120 min, and the ball-to-material ratio is controlled at 30:1.

[0047] Metallized modified carbon nanotubes were prepared through the following steps: S1. Preparation of pretreated carbon nanotubes: 2g of carbon nanotubes were added to 200mL of 1.5mol / L sodium hydroxide solution and heated under reflux at 75℃ for 3h. After filtration, the solid product was washed with deionized water until neutral. Then, it was added to a mixed solution consisting of 50mL of 25wt% hydrogen peroxide solution and 100mL of 65wt% nitric acid solution and stirred under reflux at 60℃ for 4h. After filtration, the solid product was washed with deionized water until neutral and dried under vacuum at 90℃ for 12h to obtain pretreated carbon nanotubes. S2. Preparation of modified carbon nanotubes: S2-1. Take 1.25g of pretreated carbon nanotubes and 0.215g of La(NO3)3·6H2O and add them to 150mL of deionized water. Disperse by ultrasonication for 1h to obtain precursor solution 1. S2-2, Add 0.72g glucose, 0.35g L-ascorbic acid, 0.125g NdCl3, and 0.262g N,N-diethyl-p-phenylenediamine sulfate to 100mL of deionized water and stir for 20min. Add the resulting mixture 1 to precursor solution 1 while stirring and keep stirring for 30min to obtain precursor solution 2. S2-3. Transfer the precursor solution 2 into the reactor, react at 190℃ for 16h, cool to room temperature, centrifuge, filter, wash the solid product with deionized water, and vacuum dry at 90℃ for 12h to obtain modified carbon nanotubes. S3. Preparation of metallized modified carbon nanotubes: S3-1. Take 1g of modified carbon nanotubes and add them to 500mL of stannous chloride sensitization solution. Stir at room temperature for 45min, filter, wash with deionized water until neutral, and then add to 500mL of palladium chloride activation solution. Stir at room temperature for 45min, centrifuge, wash with deionized water until neutral to obtain activated modified carbon nanotubes. The stannous chloride sensitizing solution consisted of SnCl2 12 g / L and HCl 0.75 mol / L; the palladium chloride activating solution consisted of PdCl 2.5 g / L and HCl 0.1 mol / L. S3-2. Add the activated modified carbon nanotubes to 100 mL of deionized water and ultrasonically disperse for 1 h. Add the resulting dispersion to 900 mL of plating solution under stirring. After ultrasonically dispersing for 20 min, plate at 85 °C for 1 h. Filter, wash with deionized water until neutral, and vacuum dry at 90 °C overnight to obtain metallized modified carbon nanotubes. The plating solution consists of: CoSO4 25g / L, FeSO4 18g / L, NaH2PO2 30g / L, sodium citrate 15g / L, and lead nitrate 0.05g / L.

[0048] Comparative Example 1 A vanadium-based solid hydrogen storage material, the raw materials for its preparation comprising, by mass percentage: Ti 8.5%, Cr 6%, Ni 2.5%, Mn 4%, with the remainder being V; The preparation method of the vanadium-based solid hydrogen storage material is as follows: V powder, Ti powder, Cr powder, Ni powder, and Mn powder (V powder, Ti powder, Cr powder, Ni powder, and Mn powder are all crushed to below 2μm under nitrogen protection) are added to a ball mill according to the raw material ratio and ball milled under nitrogen protection to obtain the vanadium-based solid hydrogen storage material. The ball milling speed is 400 rpm, the ball milling time is 120 min, and the ball-to-material ratio is controlled at 30:1.

[0049] Comparative Example 2 This example is basically the same as Example 1, except that the metallized modified carbon nanotubes are replaced with the pretreated carbon nanotubes prepared in Example 1.

[0050] Comparative Example 3 This example is basically the same as Example 1, except that the metallized modified carbon nanotubes are replaced with the modified carbon nanotubes prepared in Example 1.

[0051] Comparative Example 4 This example is basically the same as Example 1, except that: The metallized modified carbon nanotubes in this example were prepared through the following steps: S1. Pre-treated carbon nanotubes are prepared, with the same steps as in Example 1; S2. Preparation of metallized modified carbon nanotubes: S2-1. Take 1g of pretreated carbon nanotubes and add them to 500mL of stannous chloride sensitization solution. Stir at room temperature for 45min, filter, wash with deionized water until neutral, and then add to 500mL of palladium chloride activation solution. Stir at room temperature for 45min, centrifuge, wash with deionized water until neutral to obtain activated modified carbon nanotubes. The stannous chloride sensitizing solution consisted of SnCl2 12 g / L and HCl 0.75 mol / L; the palladium chloride activating solution consisted of PdCl 2.5 g / L and HCl 0.1 mol / L. S2-2. Add the activated modified carbon nanotubes to 100 mL of deionized water and ultrasonically disperse for 1 h. Add the resulting dispersion to 900 mL of plating solution under stirring. After ultrasonically dispersing for 20 min, plate at 85 °C for 1 h. Filter, wash with deionized water until neutral, and vacuum dry at 90 °C overnight to obtain metallized modified carbon nanotubes. The plating solution consists of: CoSO4 25g / L, FeSO4 18g / L, NaH2PO2 30g / L, sodium citrate 15g / L, and lead nitrate 0.05g / L.

[0052] Comparative Example 5 This example is basically the same as Example 1, except that: In this example, La(NO3)3·6H2O is not added in step S2-1 of the preparation of metallized modified carbon nanotubes.

[0053] Comparative Example 6 This example is basically the same as Example 1, except that: In this example, NdCl is not added in step S2-2 of the metallization-modified carbon nanotube preparation process. 3。

[0054] Comparative Example 7 This example is basically the same as Example 1, except that: In this example, CoSO₄ is not added to the plating bath in step S3 of the metallization-modified carbon nanotube preparation process. 4。

[0055] Comparative Example 8 This example is basically the same as Example 1, except that: In this example, FeSO₄ is not added to the plating bath in step S3 of the metallization-modified carbon nanotube preparation process. 4。

[0056] I. Performance Characterization 1. Reference Figure 1 The image shows the infrared absorption spectrum of the modified carbon nanotubes prepared in Example 1, illustrating the successful loading of carbon dots onto the pretreated carbon nanotubes; (Refer to...) Figure 1 The image shows the XRD pattern of the metallized modified carbon nanotubes prepared in Example 1, which demonstrates that an Fe-Co alloy layer was successfully deposited on the surface of the modified carbon nanotubes.

[0057] 2. Reduction Test The modified carbon nanotubes prepared in Example 1 and Comparative Example 6 were added to ethanol and ultrasonically dispersed to obtain modified carbon nanotube dispersions of different concentrations (0, 0.25, 0.5, 0.75, and 1 mg / mL). The modified carbon nanotube dispersions of Example 1 and Comparative Example 6 were designated CNTs 1# and CNTs 6#, respectively. The antioxidant properties of the dispersions were tested using a total antioxidant capacity assay kit (DPPH method) (Ise-Ku (Jiangsu Lianyungang) Biotechnology Co., Ltd.). Test principle: DPPH free radicals have a single electron, and their ethanol solution is purple. They have maximum absorption at 515 nm. When an antioxidant is added, a decolorization reaction occurs, and the absorbance at 515 nm decreases. Within a certain range, the change in absorbance is directly proportional to the antioxidant capacity. The change in absorbance at 515 nm can characterize the reducing power; the greater the decrease in absorbance, the stronger the reducing power.

[0058] Test results are as follows Figure 3 As shown, the modified carbon nanotubes prepared in Example 1 and Comparative Example 6 both exhibited certain reduction performance, with Example 1 showing better performance than Comparative Example 6, indicating that neodymium doping in carbon dots can improve their reduction performance.

[0059] II. Performance Testing 1. Hydrogen storage density and hydrogen absorption / desorption performance The hydrogen storage performance was measured using an H-Sorb 2600PCT hydrogen storage tester. Activation was completed by vacuuming at 40℃ for 2 hours, followed by testing of hydrogen absorption and desorption performance: 2 grams of hydrogen storage alloy were placed in the reactor of the PCT test device, and hydrogen was absorbed for the first time at 25℃ and 4 MPa hydrogen pressure; then, hydrogen was desorbed for the first time at 25℃ and 0.1 MPa hydrogen pressure.

[0060] 2. Cyclic stability 100 complete hydrogen absorption / desorption cycles were performed at 25℃ (desorption pressure 0.1 MPa, absorption pressure 4 MPa), the hydrogen storage density was measured, and then the capacity retention rate was calculated. The capacity retention rate = (maximum hydrogen absorption after the 100th cycle / initial maximum hydrogen absorption) × 100%.

[0061] Test results: Figure 4 The first hydrogen absorption curve shows that Example 1 was able to absorb more than 3.7% of hydrogen in 180 seconds.

[0062] The test data for maximum hydrogen absorption, effective hydrogen release, and cycle stability are shown in Table 1 below. Figure 5 , Figure 6 , Figure 7 As shown: Table 1 Maximum hydrogen absorption (wt%) Effective hydrogen release Capacity retention rate (%) Example 1 3.74 2.81% 99.0 Example 2 3.72 2.78 98.6 Example 3 3.69 2.75 98.4 Comparative Example 1 3.09 1.96 77.2 Comparative Example 2 3.31 2.28 79.0 Comparative Example 3 3.49 2.54 91.6 Comparative Example 4 3.44 2.50 84.8 Comparative Example 5 3.68 2.61 98.3 Comparative Example 6 3.70 2.64 98.5 Comparative Example 7 3.67 2.70 93.2 Comparative Example 8 3.59 2.67 97.9 The test results show that: The vanadium-based solid hydrogen storage materials prepared in Examples 1-3 have high maximum hydrogen absorption and effective hydrogen release, and high capacity retention, indicating that they also have excellent cycle stability.

[0063] In Comparative Example 1, without the addition of metallized modified carbon nanotubes, all properties decreased significantly; Comparative Example 2 added pretreated carbon nanotubes, which were not loaded with carbon dots and were not metallized, resulting in a significant decrease in their hydrogen absorption and desorption performance and cycle stability. In Comparative Example 3, the modified carbon nanotubes were not metallized, which prevented them from being uniformly dispersed in the alloy system, resulting in a significant decrease in their overall performance. The metallized modified carbon nanotubes in Comparative Example 4 were not loaded with reducing carbon dots, which significantly reduced their cycle stability and also reduced their effective hydrogen release. This is attributed to the fact that carbon dots can enhance the catalytic performance of carbon nanotubes in the hydrogen absorption and desorption process. The metallized carbon nanotubes in Comparative Example 5 were not doped with rare earth lanthanum, which led to a decrease in their hydrogen absorption and desorption performance. In Comparative Example 6, the carbon dots were not doped with Nd, which reduced their reducibility and led to a certain decrease in the cycle stability of the hydrogen storage material. In Comparative Example 7, the coating did not contain Co, and the cycle stability of the hydrogen storage material was somewhat reduced. In Comparative Example 8, the coating did not contain Fe, and the hydrogen absorption and desorption performance of the hydrogen storage material was somewhat reduced.

[0064] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details.

Claims

1. A vanadium-based solid hydrogen storage material, characterized in that, Its raw materials, by mass percentage, include: Ti 5-14%, Cr 3.5-9%, Ni 1.5-4%, Mn 2-8%, metallized modified carbon nanotubes 6-14%, the remainder being V; The metallized modified carbon nanotubes were prepared through the following steps: S1. Carbon nanotubes are treated with alkali and acid in sequence to obtain pretreated carbon nanotubes; S2. Load carbon dots onto pretreated carbon nanotubes to obtain modified carbon nanotubes; S3. Iron and cobalt are deposited on the modified carbon nanotubes by chemical plating to perform metallization treatment, thereby obtaining metallized modified carbon nanotubes.

2. The vanadium-based solid hydrogen storage material according to claim 1, characterized in that, Step S1 is as follows: Carbon nanotubes were added to a sodium hydroxide solution, heated under reflux, filtered, and the solid product was washed with deionized water until neutral. Then, the solid product was added to a mixed solution consisting of 20-30 wt% hydrogen peroxide solution and 60-68 wt% nitric acid solution, heated under stirring under reflux, filtered, and the solid product was washed with deionized water until neutral. The solid product was then dried under vacuum to obtain pretreated carbon nanotubes.

3. The vanadium-based solid hydrogen storage material according to claim 2, characterized in that, Step S1 is as follows: Add 1-4g of carbon nanotubes to 100-400mL of 1-3mol / L sodium hydroxide solution, heat under reflux at 65-80℃ for 1.5-6h, filter, and wash the solid product with deionized water until neutral; then add to a mixed solution consisting of 25-100mL of 20-30wt% hydrogen peroxide solution and 50-200mL of 60-68wt% nitric acid, stir under reflux at 50-70℃ for 2-8h, filter, wash the solid product with deionized water until neutral, and vacuum dry to obtain pretreated carbon nanotubes.

4. The vanadium-based solid hydrogen storage material according to claim 1, characterized in that, Step S2 is as follows: S2-1. Take pretreated carbon nanotubes and La(NO3)3·6H2O and add them to deionized water. Disperse them by ultrasonication to obtain precursor solution 1. S2-2. Add glucose, L-ascorbic acid, NdCl3, and N,N-diethyl-p-phenylenediamine sulfate to deionized water and stir. Add the resulting mixture to precursor solution 1 while stirring to obtain precursor solution 2. S2-3. Transfer the precursor solution 2 into the reactor and react at 170-230℃ for 12-24h. After the reaction is completed, cool to room temperature, centrifuge, filter, wash the solid product with deionized water, and vacuum dry to obtain modified carbon nanotubes.

5. The vanadium-based solid hydrogen storage material according to claim 4, characterized in that, Step S2 is as follows: S2-1. Take 0.5-2g of pretreated carbon nanotubes and 0.1-0.43g of La(NO3)3·6H2O and add them to 75-300mL of deionized water. Disperse by ultrasonication for 0.5-2h to obtain precursor solution 1. S2-2: Add 0.36-1.44g glucose, 0.175-0.7g L-ascorbic acid, 0.063-0.25g NdCl3, and 0.131-0.524g N,N-diethyl-p-phenylenediamine sulfate to 50-200mL of deionized water and stir for 10-40min. Add the resulting mixture to precursor solution 1 while stirring, and keep stirring for 15-60min to obtain precursor solution 2. S2-3. Transfer the precursor solution 2 into the reactor and react at 170-230℃ for 12-24h. Cool to room temperature, centrifuge, filter, wash the solid product with deionized water, and vacuum dry to obtain modified carbon nanotubes.

6. The vanadium-based solid hydrogen storage material according to claim 1, characterized in that, Step S3 is as follows: S3-1. Modified carbon nanotubes are sensitized by stannous chloride sensitizing solution and activated by palladium chloride activating solution to obtain activated modified carbon nanotubes. S3-2. Add the activated modified carbon nanotubes to deionized water and disperse them by ultrasonication. Add the resulting dispersion to the plating solution while stirring. After ultrasonic dispersion, apply the plating solution under heating. After plating is completed, filter the solution, wash with deionized water until neutral, and dry to obtain metallized modified carbon nanotubes.

7. The vanadium-based solid hydrogen storage material according to claim 6, characterized in that, Step S3 is as follows: S3-1. Take 0.5-2g of modified carbon nanotubes and add them to 250-1000mL of stannous chloride sensitization solution. Stir at room temperature for 30-90min. Filter and wash with deionized water until neutral. Then add it to 250-1000mL of palladium chloride activation solution. Stir at room temperature for 30-90min. Centrifuge and wash with deionized water until neutral to obtain activated modified carbon nanotubes. The stannous chloride sensitizing solution consists of SnCl2 10-18 g / L and HCl 0.3-1 mol / L; the palladium chloride activating solution consists of PdCl 1.5-5 g / L and HCl 0.05-0.2 mol / L. S3-2. Add the activated modified carbon nanotubes to 50-200 mL of deionized water and ultrasonically disperse for 0.5-2 h. Add the resulting dispersion to 450-1800 mL of plating solution under stirring. After ultrasonically dispersing for 10-40 min, plate at 75-90℃ for 0.5-2 h. Filter, wash with deionized water until neutral, and vacuum dry to obtain metallized modified carbon nanotubes. The plating solution consists of: CoSO4 20-30 g / L, FeSO4 10-25 g / L, NaH2PO2 22-35 g / L, sodium citrate 10-18 g / L, and lead nitrate 0.02-0.08 g / L.

8. The vanadium-based solid hydrogen storage material according to claim 1, characterized in that, The metallized modified carbon nanotubes were prepared through the following steps: S1. Preparation of pretreated carbon nanotubes: 2g of carbon nanotubes were added to 200mL of 1.5mol / L sodium hydroxide solution and heated under reflux at 75℃ for 3h. After filtration, the solid product was washed with deionized water until neutral. Then, it was added to a mixed solution consisting of 50mL of 25wt% hydrogen peroxide solution and 100mL of 65wt% nitric acid solution and stirred under reflux at 60℃ for 4h. After filtration, the solid product was washed with deionized water until neutral and dried under vacuum at 90℃ for 12h to obtain pretreated carbon nanotubes. S2. Preparation of modified carbon nanotubes: S2-1. Take 1g of pretreated carbon nanotubes and 0.215g of La(NO3)3·6H2O and add them to 150mL of deionized water. Disperse by ultrasonication for 1h to obtain precursor solution 1. S2-2, Add 0.72g glucose, 0.35g L-ascorbic acid, 0.125g NdCl3, and 0.262g N,N-diethyl-p-phenylenediamine sulfate to 100mL of deionized water and stir for 20min. Add the resulting mixture 1 to precursor solution 1 while stirring and keep stirring for 30min to obtain precursor solution 2. S2-3. Transfer the precursor solution 2 into the reactor, react at 190℃ for 16h, cool to room temperature, centrifuge, filter, wash the solid product with deionized water, and vacuum dry at 90℃ for 12h to obtain modified carbon nanotubes. S3. Preparation of metallized modified carbon nanotubes: S3-1. Take 1g of modified carbon nanotubes and add them to 500mL of stannous chloride sensitization solution. Stir at room temperature for 45min, filter, wash with deionized water until neutral, and then add to 500mL of palladium chloride activation solution. Stir at room temperature for 45min, centrifuge, wash with deionized water until neutral to obtain activated modified carbon nanotubes. The stannous chloride sensitizing solution consisted of SnCl2 12 g / L and HCl 0.75 mol / L; the palladium chloride activating solution consisted of PdCl2 5 g / L and HCl 0.1 mol / L. S3-2. Add the activated modified carbon nanotubes to 100 mL of deionized water and ultrasonically disperse for 1 h. Add the resulting dispersion to 900 mL of plating solution under stirring. After ultrasonically dispersing for 20 min, plate at 85 °C for 1 h. Filter, wash with deionized water until neutral, and vacuum dry at 90 °C overnight to obtain metallized modified carbon nanotubes. The plating solution consists of: CoSO4 25g / L, FeSO4 18g / L, NaH2PO2 30g / L, sodium citrate 15g / L, and lead nitrate 0.05g / L.

9. A method for preparing a vanadium-based solid hydrogen storage material as described in any one of claims 1-8, characterized in that, The process includes the following steps: adding V powder, Ti powder, Cr powder, Ni powder, Mn powder and metallized modified carbon nanotubes into a ball mill according to the raw material ratio, and ball milling under inert gas protection to obtain vanadium-based solid hydrogen storage materials.

10. The method for preparing vanadium-based solid hydrogen storage material according to claim 9, characterized in that, The process includes the following steps: adding V powder, Ti powder, Cr powder, Ni powder, Mn powder and metallized modified carbon nanotubes into a ball mill according to the raw material ratio, and ball milling under nitrogen protection to obtain vanadium-based solid hydrogen storage material. The ball milling speed is 150-800 rpm, the ball milling time is 60-240 min, and the ball-to-material ratio is controlled at (20~35):1.

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