A composite hydrogen storage material and its preparation method

Abstract

This invention belongs to the field of hydrogen storage materials technology, specifically relating to a composite hydrogen storage material and its preparation method. The composite hydrogen storage material provided by this invention uses polyvinyl alcohol / polyacrylonitrile modified TiO2 as a catalyst and ball-milled with MgH2. This not only reduces the hydrogen desorption temperature and improves the hydrogen desorption efficiency, but also exhibits excellent hydrogen storage / desorption capacity and good hydrogen storage / desorption stability, maintaining good hydrogen storage / desorption performance even after multiple cycles.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen storage materials technology, specifically relating to a composite hydrogen storage material and its preparation method. Background Technology

[0002] Hydrogen, as a highly efficient, clean, and energy-density renewable energy source, has attracted widespread attention and plays a crucial role in energy conversion. It is considered one of the secondary energy sources with the greatest research and development potential. However, technical challenges in hydrogen storage restrict its large-scale application. MgH2, as a solid-state hydrogen storage material, possesses advantages such as high hydrogen storage capacity, low cost, and abundant magnesium reserves, making it a promising hydrogen storage material. However, the high stability of MgH2 results in a hydrogen release enthalpy change as high as 76 kJ / mol, leading to a slow reaction rate. Therefore, its performance still needs to be optimized through catalyst-assisted methods.

[0003] TiO2, a metal oxide, is a commonly used catalyst to improve the hydrogen storage performance of MgH2. When combined with MgH2, it helps dissociate hydrogen and accelerates the transfer rate of hydrogen atoms during the reaction. However, while adding TiO2 can improve the hydrogen storage / desorption performance of MgH2 to some extent, the storage / desorption temperature still needs to be above 300℃, and the cycle stability is poor, making it difficult to meet the practical application requirements of MgH2 hydrogen storage materials. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a composite hydrogen storage material, which uses polyvinyl alcohol / polyacrylonitrile modified TiO2 material as a catalyst and ball-milled with MgH2. This not only reduces the hydrogen release temperature and improves the hydrogen release efficiency, but also has excellent hydrogen storage / release capacity and good hydrogen storage / release stability, and can still exhibit good hydrogen storage / release performance after multiple cycles.

[0005] The first aspect of this invention provides a method for preparing a composite hydrogen storage material, comprising the following steps:

[0006] S1: Tetrabutyl titanate and tetrapropylammonium hydroxide were added to deionized water and mixed well. Then, the mixture was placed in a high-pressure reactor and reacted at 180-200℃ for 20-24 h. After centrifugation, washing, drying, and calcination, porous nano-TiO2 was obtained.

[0007] S2: Disperse porous nano-TiO2 and acrylonitrile monomer in deionized water, add dicumyl peroxide, stir thoroughly under nitrogen atmosphere, heat to 50~60℃ for polymerization reaction for 3~4h to obtain TiO2 / polyacrylonitrile composite material.

[0008] S3: Add polyvinyl alcohol powder to deionized water and mix to obtain a polyvinyl alcohol aqueous solution. Then add ammonium persulfate and ultrasonically disperse it evenly to prepare a polyvinyl alcohol crosslinking solution. Immerse the TiO2 / polyacrylonitrile composite material in the polyvinyl alcohol crosslinking solution for 10-20 minutes. After taking it out, wash it with water and dry it to obtain the polyvinyl alcohol / polyacrylonitrile modified TiO2 material.

[0009] S4: Ball mill and mix MgH2 with polyvinyl alcohol / polyacrylonitrile modified TiO2 material.

[0010] Furthermore, the molar ratio of tetrabutyl titanate to tetrapropylammonium hydroxide is 10:1.

[0011] Furthermore, the mixture is stirred in a water bath at 60-80°C for 3-6 hours before being placed in a high-pressure reactor for reaction.

[0012] Furthermore, the calcination temperature is 450~550℃, and the calcination time is 2~3h.

[0013] Furthermore, the mass ratio of porous nano-TiO2, acrylonitrile monomer, and dicumyl peroxide is 2:1:0.03.

[0014] Furthermore, polyvinyl alcohol powder and deionized water are stirred in a water bath at 90-95°C for 30-40 minutes to obtain a polyvinyl alcohol aqueous solution; the concentration of the polyvinyl alcohol aqueous solution is 6wt%-10wt%.

[0015] Furthermore, the mass ratio of ammonium persulfate to polyvinyl alcohol powder is 1:15~20.

[0016] Furthermore, the mass ratio of MgH2 to the polyacrylonitrile / polyvinyl alcohol modified TiO2 material is 10:1~1.5.

[0017] Furthermore, the ball milling process is carried out at room temperature, with a ball-to-material ratio of 50:1, a milling time of 10-12 hours, and a milling speed of 300-500 r / min.

[0018] A second aspect of the present invention provides a composite hydrogen storage material, which is prepared by the above-described method for preparing composite hydrogen storage materials.

[0019] The beneficial effects achieved by one or more technical solutions of the present invention are as follows:

[0020] This invention utilizes a hydrothermal method to prepare porous nano-TiO2, effectively increasing the specific surface area of ​​TiO2 and exposing abundant oxygen vacancies on the TiO2 surface. During dehydrogenation, this facilitates the transfer of electrons from the Mg-H bonds in MgH2 to TiO2, promoting the breaking of Mg-H bonds and accelerating dehydrogenation. In-situ polymerization of polyacrylonitrile on TiO2 not only inhibits the aggregation of nano-TiO2 but also enhances catalytic activity, lowers the dehydrogenation temperature, and improves dehydrogenation efficiency. Simultaneously, polyacrylonitrile provides a large number of cyano polar groups, which are beneficial for hydrogen molecule adsorption and improve hydrogen storage performance.

[0021] Building upon this, the present invention employs polyvinyl alcohol (PVA) for further impregnation treatment of the TiO2 / polyacrylonitrile composite material. The hydroxyl groups of PVA and the cyano groups of polyacrylonitrile can form a stable hydrogen bond network within the MgH2 hydrogen storage material system, maintaining structural stability and exhibiting good reversible hydrogen storage / desorption performance. Even after multiple cycles, it still demonstrates good hydrogen storage / desorption performance. Furthermore, the hydroxyl groups on PVA are also polar groups, which can further enhance hydrogen adhesion and increase hydrogen storage capacity. Attached Figure Description

[0022] Figure 1 This is a SEM image of the polyvinyl alcohol / polyacrylonitrile modified TiO2 material prepared in Example 1 of this invention; Detailed Implementation

[0023] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments and comparative examples.

[0024] Example 1

[0025] This embodiment provides a composite hydrogen storage material, and the preparation method is as follows:

[0026] S1: Tetrabutyl titanate and tetrapropylammonium hydroxide were added to deionized water at a molar ratio of 10:1 and mixed well (the addition ratio of deionized water to tetrabutyl titanate was 50mL:0.01mol). After stirring in a water bath at 70℃ for 4h, the mixture was placed in a high-pressure reactor and reacted at 180℃ for 24h. After centrifugation, washing, drying, and calcination, the calcination temperature was 500℃ and the calcination time was 3h to obtain porous nano-TiO2.

[0027] S2: Porous nano-TiO2 and acrylonitrile monomer are dispersed in deionized water, and dicumyl peroxide is added. The mass ratio of porous nano-TiO2, acrylonitrile monomer, and dicumyl peroxide is 2:1:0.03. The mass of deionized water is 30 times the mass of acrylonitrile monomer. The mixture is stirred thoroughly under a nitrogen atmosphere and heated to 60°C for 3 hours to carry out the polymerization reaction, thereby obtaining the TiO2 / polyacrylonitrile composite material.

[0028] S3: Polyvinyl alcohol powder was added to deionized water and stirred in a 90°C water bath for 40 min to obtain a polyvinyl alcohol aqueous solution with a concentration of 8 wt%. Then, ammonium persulfate was added and ultrasonically dispersed evenly (the mass ratio of ammonium persulfate to polyvinyl alcohol powder was 1:15) to prepare a polyvinyl alcohol crosslinking solution. The TiO2 / polyacrylonitrile composite material was immersed in the polyvinyl alcohol crosslinking solution for 15 min. After removal, it was washed with water and dried to obtain the polyvinyl alcohol / polyacrylonitrile modified TiO2 material.

[0029] S4: MgH2 and polyvinyl alcohol / polyacrylonitrile modified TiO2 material were ball-milled at a mass ratio of 10:1 at room temperature, with a ball-to-material ratio of 50:1, a ball-milling time of 10 h, and a ball-milling speed of 500 r / min.

[0030] Example 2

[0031] This embodiment provides a composite hydrogen storage material, and the preparation method is as follows:

[0032] S1: Tetrabutyl titanate and tetrapropylammonium hydroxide were added to deionized water at a molar ratio of 10:1 and mixed well (the addition ratio of deionized water to tetrabutyl titanate was 50mL:0.01mol). After stirring in a water bath at 80℃ for 3h, the mixture was placed in a high-pressure reactor and reacted at 190℃ for 20h. After centrifugation, washing, drying, and calcination, the calcination temperature was 500℃ and the calcination time was 2h to obtain porous nano-TiO2.

[0033] S2: Porous nano-TiO2 and acrylonitrile monomer are dispersed in deionized water, and dicumyl peroxide is added. The mass ratio of porous nano-TiO2, acrylonitrile monomer, and dicumyl peroxide is 2:1:0.03. The mass of deionized water is 30 times the mass of acrylonitrile monomer. The mixture is stirred thoroughly under a nitrogen atmosphere and heated to 60°C for 3 hours to carry out the polymerization reaction, thereby obtaining the TiO2 / polyacrylonitrile composite material.

[0034] S3: Polyvinyl alcohol powder was added to deionized water and stirred in a 90°C water bath for 40 min to obtain a polyvinyl alcohol aqueous solution with a concentration of 10 wt%. Then, ammonium persulfate was added and ultrasonically dispersed evenly (the mass ratio of ammonium persulfate to polyvinyl alcohol powder was 1:15) to prepare a polyvinyl alcohol crosslinking solution. The TiO2 / polyacrylonitrile composite material was immersed in the polyvinyl alcohol crosslinking solution for 10 min. After removal, it was washed with water and dried to obtain the polyvinyl alcohol / polyacrylonitrile modified TiO2 material.

[0035] S4: MgH2 and polyvinyl alcohol / polyacrylonitrile modified TiO2 material were ball-milled at a mass ratio of 10:1.3 at room temperature, with a ball-to-material ratio of 50:1, a ball-milling time of 12 h, and a ball-milling speed of 400 r / min.

[0036] Example 3

[0037] This embodiment provides a composite hydrogen storage material, and the preparation method is as follows:

[0038] S1: Tetrabutyl titanate and tetrapropylammonium hydroxide were added to deionized water at a molar ratio of 10:1 and mixed well (the addition ratio of deionized water to tetrabutyl titanate was 50mL:0.01mol). After stirring in a water bath at 70℃ for 6h, the mixture was placed in a high-pressure reactor and reacted at 200℃ for 20h. After centrifugation, washing, drying, and calcination, the calcination temperature was 450℃ and the calcination time was 3h to obtain porous nano-TiO2.

[0039] S2: Porous nano-TiO2 and acrylonitrile monomer are dispersed in deionized water, and dicumyl peroxide is added. The mass ratio of porous nano-TiO2, acrylonitrile monomer, and dicumyl peroxide is 2:1:0.03. The mass of deionized water is 30 times the mass of acrylonitrile monomer. The mixture is stirred thoroughly under a nitrogen atmosphere and heated to 60°C for 3 hours to carry out the polymerization reaction, thereby obtaining the TiO2 / polyacrylonitrile composite material.

[0040] S3: Polyvinyl alcohol powder was added to deionized water and stirred in a 95°C water bath for 30 min to obtain a polyvinyl alcohol aqueous solution with a concentration of 6 wt%. Then, ammonium persulfate was added and ultrasonically dispersed evenly (the mass ratio of ammonium persulfate to polyvinyl alcohol powder was 1:18) to prepare a polyvinyl alcohol crosslinking solution. The TiO2 / polyacrylonitrile composite material was immersed in the polyvinyl alcohol crosslinking solution for 10 min. After removal, it was washed with water and dried to obtain the polyvinyl alcohol / polyacrylonitrile modified TiO2 material.

[0041] S4: MgH2 and polyvinyl alcohol / polyacrylonitrile modified TiO2 material were ball-milled at a mass ratio of 10:1.5 at room temperature, with a ball-to-material ratio of 50:1, a ball-milling time of 12 h, and a ball-milling speed of 400 r / min.

[0042] Example 4

[0043] This embodiment provides a composite hydrogen storage material, and the preparation method is as follows:

[0044] S1: Tetrabutyl titanate and tetrapropylammonium hydroxide were added to deionized water at a molar ratio of 10:1 and mixed well (the addition ratio of deionized water to tetrabutyl titanate was 50mL:0.01mol). After stirring in a water bath at 80℃ for 5h, the mixture was placed in a high-pressure reactor and reacted at 180℃ for 24h. After centrifugation, washing, drying, and calcination, the calcination temperature was 550℃ and the calcination time was 2h to obtain porous nano-TiO2.

[0045] S2: Porous nano-TiO2 and acrylonitrile monomer are dispersed in deionized water, and dicumyl peroxide is added. The mass ratio of porous nano-TiO2, acrylonitrile monomer, and dicumyl peroxide is 2:1:0.03, and the mass of deionized water is 30 times the mass of acrylonitrile monomer. The mixture is stirred thoroughly under a nitrogen atmosphere and heated to 50°C for 4 hours to carry out the polymerization reaction, thereby obtaining the TiO2 / polyacrylonitrile composite material.

[0046] S3: Polyvinyl alcohol powder was added to deionized water and stirred in a 95°C water bath for 30 min to obtain a polyvinyl alcohol aqueous solution with a concentration of 8 wt%. Then, ammonium persulfate was added and ultrasonically dispersed evenly (the mass ratio of ammonium persulfate to polyvinyl alcohol powder was 1:20) to prepare a polyvinyl alcohol crosslinking solution. The TiO2 / polyacrylonitrile composite material was immersed in the polyvinyl alcohol crosslinking solution for 20 min. After removal, it was washed with water and dried to obtain the polyvinyl alcohol / polyacrylonitrile modified TiO2 material.

[0047] S4: MgH2 and polyvinyl alcohol / polyacrylonitrile modified TiO2 material were ball-milled at a mass ratio of 10:1.5 at room temperature, with a ball-to-material ratio of 50:1, a ball-milling time of 10 h, and a ball-milling speed of 300 r / min.

[0048] Comparative Example 1

[0049] This comparative example provides a composite hydrogen storage material, and the preparation method is as follows:

[0050] S1: Tetrabutyl titanate and tetrapropylammonium hydroxide were added to deionized water at a molar ratio of 10:1 and mixed well (the addition ratio of deionized water to tetrabutyl titanate was 50mL:0.01mol). After stirring in a water bath at 80℃ for 3h, the mixture was placed in a high-pressure reactor and reacted at 190℃ for 20h. After centrifugation, washing, drying, and calcination, the calcination temperature was 500℃ and the calcination time was 2h to obtain porous nano-TiO2.

[0051] S2: MgH2 and porous nano-TiO2 were ball-milled at a mass ratio of 10:1.3 at room temperature, with a ball-to-material ratio of 50:1, a ball-milling time of 12 h, and a ball-milling speed of 400 r / min.

[0052] Comparative Example 2

[0053] This comparative example provides a composite hydrogen storage material, and the preparation method is as follows:

[0054] S1: Tetrabutyl titanate and tetrapropylammonium hydroxide were added to deionized water at a molar ratio of 10:1 and mixed well (the addition ratio of deionized water to tetrabutyl titanate was 50mL:0.01mol). After stirring in a water bath at 80℃ for 3h, the mixture was placed in a high-pressure reactor and reacted at 190℃ for 20h. After centrifugation, washing, drying, and calcination, the calcination temperature was 500℃ and the calcination time was 2h to obtain porous nano-TiO2.

[0055] S2: Porous nano-TiO2 and acrylonitrile monomer are dispersed in deionized water, and dicumyl peroxide is added. The mass ratio of porous nano-TiO2, acrylonitrile monomer, and dicumyl peroxide is 2:1:0.03. The mass of deionized water is 30 times the mass of acrylonitrile monomer. The mixture is stirred thoroughly under a nitrogen atmosphere and heated to 60°C for 3 hours to carry out the polymerization reaction, thereby obtaining the TiO2 / polyacrylonitrile composite material.

[0056] S3: MgH2 and TiO2 / polyacrylonitrile composite material were ball-milled at a mass ratio of 10:1.3 at room temperature, with a ball-to-material ratio of 50:1, a ball-milling time of 12 h, and a ball-milling speed of 400 r / min.

[0057] Performance testing:

[0058] The hydrogen desorption performance of the composite hydrogen storage materials prepared in Examples 1-4 and Comparative Examples 1-2 was tested. The sample amount was 10 mg. The hydrogen desorption test was carried out at a heating rate of 2 °C / min. The peak hydrogen desorption temperature was measured, and the isothermal hydrogen desorption kinetics of the sample at 300 °C was detected. The results are shown in Table 1.

[0059] Table 1

[0060]

[0061] As shown in Table 1, the composite hydrogen storage materials prepared in Examples 1-4 of this invention have lower peak hydrogen release temperature, faster hydrogen release efficiency, and higher hydrogen release capacity.

[0062] The hydrogen storage materials in Example 1 and Comparative Example 2 were tested at 300°C and 270°C for hydrogen storage / release capacity and cycle performance, respectively. The results are shown in Table 2 (Example 1) and Table 3 (Comparative Example 2).

[0063] Table 2

[0064]

[0065] Table 3

[0066]

[0067] As shown in Tables 2 and 3, the composite hydrogen storage material prepared in Example 1 of this invention exhibits excellent hydrogen storage / desorption stability, maintaining a high hydrogen storage / desorption capacity even after 100 cycles. This excellent stability is mainly attributed to the use of TiO2 material co-modified with polyvinyl alcohol and polyacrylonitrile as a catalyst. The hydroxyl groups of polyvinyl alcohol and the cyano groups of polyacrylonitrile can form a stable hydrogen bond network within the MgH2 hydrogen storage material system, maintaining structural stability and demonstrating good reversibility of hydrogen storage / desorption. It still exhibits good hydrogen storage / desorption performance after multiple cycles. In contrast, the composite hydrogen storage material in Comparative Example 2, which only uses TiO2 / polyacrylonitrile composite material as the MgH2 catalyst, shows poor structural stability and rapid decay of hydrogen storage / desorption capacity during cycling.

Claims

1. A method for preparing a composite hydrogen storage material, characterized by: The method comprises the following steps: S1: adding tetrabutyl titanate and tetrapropyl ammonium hydroxide into deionized water, mixing, and then placing in a high-pressure reaction kettle to react at 180-200 DEG C for 20-24 h, centrifuging, washing, drying, and then calcining to obtain porous nano-TiO2; S2: dispersing the porous nano-TiO2 and acrylonitrile monomer in deionized water, adding dicumyl peroxide, stirring sufficiently under a nitrogen atmosphere, heating to 50-60 DEG C, and then performing polymerization for 3-4 h to obtain a TiO2 / polyacrylonitrile composite material; S3: adding polyvinyl alcohol powder into deionized water to obtain a polyvinyl alcohol aqueous solution, adding ammonium persulfate and ultrasonically dispersing uniformly to prepare a polyvinyl alcohol crosslinking solution, immersing the TiO2 / polyacrylonitrile composite material in the polyvinyl alcohol crosslinking solution for 10-20 min, and then washing and drying to obtain a polyvinyl alcohol / polyacrylonitrile modified TiO2 material; S4: ball-milling the MgH2 and the polyvinyl alcohol / polyacrylonitrile modified TiO2 material.

2. The preparation method of the composite hydrogen storage material as described in claim 1, characterized in that: The molar ratio of tetrabutyl titanate to tetrapropyl ammonium hydroxide is 10:

1.

3. The method for preparing the composite hydrogen storage material as described in claim 1, characterized in that: After stirring in a water bath at 60-80 DEG C for 3-6 h, the mixture is placed in a high-pressure reaction kettle to react.

4. The method for preparing the composite hydrogen storage material as described in claim 1, characterized in that: The calcination temperature is 450-550 DEG C, and the calcination time is 2-3 h.

5. The method for preparing the composite hydrogen storage material as described in claim 1, characterized in that: The mass ratio of the porous nano-TiO2, acrylonitrile monomer and dicumyl peroxide is 2:1:0.

03.

6. The method for preparing the composite hydrogen storage material as described in claim 1, characterized in that: The polyvinyl alcohol powder and deionized water are stirred in a water bath at 90-95 DEG C for 30-40 min to obtain a polyvinyl alcohol aqueous solution; the concentration of the polyvinyl alcohol aqueous solution is 6wt%-10wt%.

7. The method for preparing the composite hydrogen storage material as described in claim 1, characterized in that: The mass ratio of ammonium persulfate to polyvinyl alcohol powder is 1:15-20.

8. The method for preparing the composite hydrogen storage material as described in claim 1, characterized in that: The mass ratio of MgH2 to the polyacrylonitrile / polyvinyl alcohol modified TiO2 material is 10:1-1.

5.

9. The method for preparing the composite hydrogen storage material as described in claim 1, characterized in that: The ball-milling process is performed at room temperature, the ball-to-material ratio is 50:1, the ball-milling time is 10-12 h, and the ball-milling rotation speed is 300-500 r / min.

10. A composite hydrogen storage material, characterized by, The composite hydrogen storage material is prepared by the method of any one of claims 1-9.

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