A MnTi-MOF derivative MnTi@C material based on regulation of crystal structure, a preparation method and application thereof
By preparing MnTi@C, a bimetallic MnTi-MOF derivative based on Mn and Ti, and altering its crystal structure and topology, the stability and catalytic efficiency issues of monometallic MOFs were resolved, thereby improving the hydrogen storage performance of MgH2.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- GUILIN UNIV OF ELECTRONIC TECH
- Filing Date
- 2024-02-05
- Publication Date
- 2026-07-03
AI Technical Summary
Existing monometallic MOF catalysts have low thermal and mechanical stability, low catalytic efficiency and selectivity, and the microstructure of bimetallic MOFs has not been optimized, which makes it impossible to improve the catalytic effect.
By selecting Mn and Ti as metal sources and utilizing their different coordination numbers, bimetallic MnTi-MOF derivative MnTi@C materials were prepared, thereby altering their crystal structure and topology and improving the material's stability and catalytic effect.
This study improved the hydrogen storage kinetics of MgH2, enhanced the thermal and mechanical stability of the material, and improved the catalytic effect and selectivity of the catalyst.
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Figure CN118002113B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of hydrogen storage catalysis technology, specifically to a bimetallic MnTi-MOF derivative MnTi@C material based on regulated crystal structure, its preparation method, and its application. Background Technology
[0002] MgH2, as a highly efficient hydrogen storage material, possesses a high hydrogen storage content (7.6 wt%) and advantages such as good cycle performance, non-toxicity, room temperature stability, and environmental friendliness. However, MgH2 also suffers from drawbacks, including a relatively high activation energy, high hydrogen absorption and desorption temperatures, and slow hydrogen absorption and desorption kinetics. Adding a catalyst is an effective method to address the slow hydrogen absorption and desorption kinetics of MgH2. Compared to alloying or nano-sizing, adding a catalyst requires less dosage, is lower in cost, and is more efficient. Furthermore, non-metallic catalysts offer advantages over precious metals in terms of lower cost, wider availability, and higher yield. Therefore, selecting transition metals as catalysts is an effective way to solve the slow hydrogen absorption and desorption kinetics of MgH2.
[0003] Transition metals exhibit good catalytic activity for magnesium-based hydrogen storage materials, effectively improving hydrogen absorption kinetics. For example, existing literature 1 (MSYahya, NNSulaiman, NSMustafa, FAHalim Yap, M.Ismail, Improvement of hydrogen storage properties in MgH2 catalyzed by K2NbF7, [J] International Journal of Hydrogen Energy, 2018, 943(31) 14532-14540) studied the catalytic effect of K2NbF7 on the hydrogen storage performance of MgH2. MgH2 was ball-milled with 5wt% K2NbF7 powder. MgH2 + 5wt% K2NbF7 reduced the initial dehydrogenation temperature to 255℃. However, the problem with this technique is that the microstructure of K2NbF7 exhibits irregular agglomeration, which is due to the poor dispersibility of K2NbF7 due to its lack of treatment.
[0004] To address the aforementioned dispersion issues, common techniques involve loading transition metals onto a support or fabricating specific structures to improve dispersion. Among these, MOFs possess advantages such as large specific surface area, high porosity, and good dispersibility, effectively improving catalyst dispersion. For example, existing literature 2 (Lu Z, He J, Song M, et al. Bullet-like vanadium-based MOF as a highly active catalyst for promoting the hydrogenstorage property in MgH2[J]. International Journal of Minerals, Metallurgy and Materials, 2023, 30(1):44-53.) synthesized a bullet-shaped catalyst based on V-MOF via solvothermal and calcination methods. By ball milling MgH2, the initial hydrogen decomposition temperature of 7wt% V-MOF-MgH2 decreased to 190.6℃, improving the catalytic effect on MgH2. However, this technical approach has two problems:
[0005] 1. Single-metal MOFs are constructed from a single type of metal ions and ligands, resulting in a relatively simple and monotonous topological structure and microstructure. They lack adaptability and resistance to the external environment, leading to low thermal and mechanical stability.
[0006] 2. Single-metal MOFs have the same valence state and electronic configuration for a single type of metal ion, which limits their catalytic effect. They lack diverse catalytic active sites and the ability to regulate catalytic reaction intermediates, resulting in low catalytic efficiency and selectivity.
[0007] To address the issues of low catalytic efficiency and selectivity in monometallic MOFs, bimetallic MOFs can be prepared to improve these properties. The basic principle is that bimetallic MOFs contain two metals simultaneously, and the electronic structures of these two metals interact, resulting in a synergistic catalytic effect. This leads to increased selectivity in the catalytic process and thus improved catalytic efficiency. Furthermore, bimetallic MOFs can better disperse the two transition metals within their structure, enhancing the catalytic effect of the catalyst. For example, existing literature 3 (Xing X, Liu Y, Zhang Z, et al. Hierarchical Structure Carbon-Coated CoNi Nanocatalysts Derived from Flower-Like Bimetal MOFs: Enhancing the Hydrogen Storage Performance of MgH2 under Mild Conditions[J].ACS Sustainable Chemistry & Engineering, 2023, 11(12): 4825-4837.) synthesized a CoNi bimetallic MOF catalytic material via a solvothermal method and obtained CoNi@C through calcination. Although this technical solution achieves synergistic catalytic effects between the two metals and improves selectivity, the microstructure of the bimetallic MOF is not optimized. This is because, in the preparation of conventional bimetallic MOFs, the selection of the second metal element is based on whether it can maintain the crystal form and microstructure of the original monometallic MOF to ensure successful preparation. In other words, conventional bimetallic MOFs do not have the ability to change the crystal structure. This directly results in the ligand and the two metal ions reacting to form only a single crystal phase, maintaining the initial crystal structure and topology. Therefore, the structure of the MOF cannot be adjusted, and ultimately, the thermal and mechanical stability of the MOF cannot be improved. Summary of the Invention
[0008] The purpose of this invention is to provide a bimetallic MnTi-MOF derivative MnTi@C material based on regulated crystal structure, its preparation method, and its applications. To address the technical problems existing in the prior art, the following approach is adopted to solve the aforementioned problems:
[0009] Bimetallic MOFs were prepared by selecting compounds of Mn and Ti as metal sources. The different coordination numbers of Mn and Ti (Mn ions have a coordination number of 6 and Ti ions have a coordination number of 8) and their different coordination preferences were utilized to give the MOFs a more compact crystal structure and topology by mixing metal ions with different coordination. This changed the microstructure of the material and improved the thermal and mechanical stability of the MOFs. At the same time, it improved the MOFs' resistance to water molecules and other organic solvents.
[0010] The technical solution to achieve the objective of this invention is:
[0011] A bimetallic MnTi-MOF derivative, MnTi@C, based on a controlled crystal structure, is prepared from two transition metal sources, N,N-dimethylformamide, methanol, and terephthalic acid. The bimetallic MOF, named MnTi-MOF, is obtained by a solvothermal method; the resulting material, MnTi@C, is obtained by calcination.
[0012] The MnTi-MOF has a regular hexagonal prism-pyramidal structure with a diameter of 3-5 micrometers and a length of 15-20 micrometers.
[0013] The microstructure of the MnTi@C is a rough hexagonal prism-pyramidal structure with a diameter of 3-5 micrometers and a length of 15-20 micrometers.
[0014] A method for preparing bimetallic MnTi-MOF derivative MnTi@C materials based on regulated crystal structure includes the following steps:
[0015] Step 1, Preparation of MnTi-MOF: First, isopropyl titanate, MnCl2·4H2O, and terephthalic acid are placed in a mixed solvent to obtain a reaction solution, which is then stirred under certain conditions. After that, the reaction is carried out under certain conditions. Finally, the reaction product is centrifuged and washed under certain conditions. After centrifugation and washing, it is then vacuum dried under certain conditions to obtain MnTi-MOF.
[0016] In step 1, the molar ratio of isopropyl titanate, MnCl2·4H2O and terephthalic acid is 1:1:3.
[0017] In step 1, the mixed solvent is obtained by mixing N,N-dimethylformamide (DMF) and methanol in a volume ratio of 9:1.
[0018] In step 1, the stirring conditions for the reaction solution are as follows: stirring time is 20-40 min.
[0019] In step 1, the reaction conditions are: reaction temperature of 150°C and reaction time of 16 hours.
[0020] In step 1, the conditions for centrifugal washing are as follows: centrifugal washing rate is 8000-10000 rpm, centrifugal washing time is 10-20 min, centrifugal washing solutions are DMF and methanol, and centrifugal washing is performed 2-4 times for each centrifugal washing solution.
[0021] In step 1, the drying conditions are: drying temperature of 60-80℃ and drying time of 18-30h.
[0022] Step 2, Preparation of MnTi@C: Under certain conditions, the MnTi-MOF obtained in Step 1 is calcined to obtain MnTi@C;
[0023] In step 2, the calcination conditions are as follows: under argon atmosphere, the calcination temperature is 600-650℃, and the calcination time is 60-120 min.
[0024] An application of MnTi@C, a bimetallic MnTi-MOF derivative with regulated crystal structure, as a hydrogen storage catalyst for MgH2 is proposed. Based on ball milling, under certain conditions, MnTi@C and MgH2 are ball milled to meet a certain mass ratio to obtain MgH2-MnTi@C.
[0025] The conditions for the ball milling method are as follows: the mass fraction of MnTi@C is 5-15 wt% of the total mass, under argon conditions, the mass ratio of ball to material is (40-60):1, the ball milling speed is 400-500 rpm, and the ball milling time is 12-15 h.
[0026] The initial hydrogen release temperature of the obtained MgH2-MnTi@C was 150-160℃ under a programmed heating rate of 3-5℃ / min.
[0027] The obtained MgH2-MnTi@C has a hydrogen absorption capacity of 5.5-6.1 wt% under the conditions of hydrogen absorption pressure of 20-30 bar, hydrogen absorption temperature of 150-250℃, and hydrogen absorption time of 30-90 s.
[0028] The hydrogen release amount of the obtained MgH2-MnTi@C was 5.0-5.6 wt% under the conditions of hydrogen release temperature of 250-350℃ and hydrogen release time of 120-240s.
[0029] Therefore, the present invention has been shown to be identifiable by XRD, SEM, PCT, and other methods as follows:
[0030] To verify the composition of MnTi-MOF, XRD analysis was performed. The synthesized MnTi-MOF exhibited distinct diffraction peaks at 2θ = 7.01°, 8.55°, and 9.83°. Furthermore, the sharp diffraction peaks indicated that the MnTi-MOF possessed good crystallinity, large grains, few crystal defects, and a smooth, regular, and uniform microstructure.
[0031] To verify the microstructure of MnTi-MOF, SEM tests were performed. The microstructure of MnTi-MOF exhibits a hexagonal prism-pyramidal structure with a smooth surface and sharp edges.
[0032] To verify the composition of MnTi@C, XRD analysis was performed. MnTi@C exhibited diffraction peaks for both MnO and TiO2. The results indicate that the carbonized MnTi-MOF exists in oxide form.
[0033] To verify the microstructure of MnTi@C, SEM analysis was performed. MnTi@C retains the hexagonal prism-pyramidal structure of MnTi-MOF, but its surface is rough. The test results indicate that the carbonization process does not change the microstructure of the material. Combined with XRD results, it is clear that the carbonization process removes organic components while retaining the carbon skeleton. Therefore, the surface of the material becomes rough due to calcination. The direct effect is that calcination increases the active sites of the material, increases the specific surface area of the catalyst, which is beneficial to mass and heat transfer between the catalyst and reactants, and can reduce the adsorption time of reactants on the catalyst.
[0034] To demonstrate the hydrogen desorption kinetics of MgH2-MnTi@C, high-temperature gas desorption tests (PCT) were conducted. Under a programmed heating rate of 3-5 °C / min, the initial hydrogen desorption temperature of the MgH2-MnTi@C material was 150-160 °C.
[0035] To demonstrate the isothermal hydrogen adsorption kinetics of MgH2-MnTi@C, high-temperature gas adsorption tests (PCT) were conducted. Under the conditions of hydrogen adsorption temperature of 150-250℃, hydrogen adsorption pressure of 20-30 bar, and hydrogen adsorption time of 30-90 s, the hydrogen adsorption capacity of MgH2-MnTi@C was 5.5-6.1 wt%.
[0036] To demonstrate the isothermal hydrogen desorption kinetics of MgH2-MnTi@C material, PCT high-temperature gas desorption tests were conducted at different temperatures. Under the conditions of hydrogen desorption temperature of 250-350℃ and hydrogen desorption time of 120-240s, the hydrogen desorption amount of MgH2-MnTi@C was 5.0-5.6wt%.
[0037] Compared with the prior art, the present invention has the following advantages:
[0038] 1. By using bimetals, the crystal structure and topology of MOFs can be altered, improving their resistance to water molecules and other organic solvents, thereby enhancing the material's stability.
[0039] 2. The modified crystal structure and topology of the resulting MiTi-MOF can more stably support metal particles, thereby improving the catalytic effect of subsequent MnTi@C and enhancing the hydrogen storage kinetics of MgH2.
[0040] 3. The raw materials used in this invention are all industrially produced chemical raw materials that are available on the market and easy to obtain. The synthesis process is simple, the reaction cycle is short, and the reaction process has low energy consumption and low pollution. Attached image description:
[0041] Figure 1 The images show the XRD patterns of MnTi-MOF in Example 1, Mn-MOF in Comparative Example 1, and Ti-MOF in Comparative Example 2.
[0042] Figure 2 Here is a SEM image of MnTi-MOF in Example 1;
[0043] Figure 3 The images show the XRD patterns of MnTi@C in Example 1, Mn@C in Comparative Example 1, and Ti@C in Comparative Example 2.
[0044] Figure 4 Here is a SEM image of MnTi@C in Example 1;
[0045] Figure 5 The graph shows the hydrogen desorption performance of MgH2-MnTi@C in Example 1, MgH2-Mn@C in Comparative Example 1, MgH2-Ti@C in Comparative Example 2, and pure MgH2 as a function of temperature.
[0046] Figure 6 The isothermal hydrogen absorption performance graphs are shown for MgH2-MnTi@C in Example 1, MgH2-Mn@C in Comparative Example 1, MgH2-Ti@C in Comparative Example 2, and pure MgH2.
[0047] Figure 7 The graph shows the isothermal hydrogen desorption performance of MgH2-MnTi@C at different temperatures in Example 1.
[0048] Figure 8 The image shows the SEM image of Mn@C in Comparative Example 1;
[0049] Figure 9 The image shows the SEM image of Ti@C in Comparative Example 2. Detailed Implementation
[0050] The present invention will be further described in detail through embodiments and with reference to the accompanying drawings, but this is not intended to limit the scope of the invention.
[0051] Example 1
[0052] A method for preparing bimetallic MnTi-MOF derivative MnTi@C materials based on controlled crystal structure, the specific steps of which are as follows:
[0053] Step 1, Preparation of MnTi-MOF: First, a reaction solution was prepared by mixing isopropyl titanate, MnCl2·4H2O, and terephthalic acid in a mixed solvent with a molar ratio of 1:1:3. The mixed solvent was N,N-dimethylformamide (DMF) and methanol in a volume ratio of 9:1. The reaction solution was stirred for 20 min, and then reacted at 150 °C for 16 h. Finally, the reaction product was centrifuged at 10,000 rpm for 15 min, using DMF and methanol as washing solutions, and centrifuged twice with each washing solution. After centrifugation and washing, the product was vacuum dried at 60 °C for 24 h to obtain MnTi-MOF.
[0054] To verify the composition of MnTi-MOF, XRD tests were performed. The test results are as follows: Figure 1 As shown, the synthesized MnTi-MOF has obvious diffraction peaks at 2θ = 7.01°, 8.55° and 9.83°. At the same time, the sharp diffraction peaks indicate that MnTi-MOF has good crystallinity, large grains, few crystal defects, and a smooth, regular and uniform microstructure.
[0055] To verify the microstructure of MnTi-MOF, SEM testing was performed. The test results are as follows: Figure 2 As shown, the microstructure of MnTi-MOF exhibits a hexagonal prism-pyramidal structure with a smooth surface and distinct edges.
[0056] Step 2, Preparation of MnTi@C: Under argon atmosphere, the MnTi-MOF obtained in Step 1 is calcined at a calcination temperature of 600℃ for 120 min to obtain the MnTi@C material, a bimetallic MnTi-MOF derivative based on regulated crystal structure, which is abbreviated as MnTi@C.
[0057] To verify the composition of MnTi@C, XRD tests were performed. The test results are as follows: Figure 3 As shown, MnTi@C contains diffraction peaks for both MnO and TiO2. The test results indicate that the carbonized MnTi-MOF exists in the form of oxides.
[0058] To verify the microstructure of MnTi@C, SEM testing was performed. The test results are as follows: Figure 4As shown, MnTi@C retains the hexagonal prism-pyramidal structure of MnTi-MOF, but its surface is rough. Test results indicate that the carbonization process does not change the material's microstructure. Combined with XRD results, it is clear that the carbonization process removes organic components while retaining the carbon skeleton. Therefore, the surface of the material becomes rough due to calcination. The direct effect is that calcination increases the active sites and the specific surface area of the catalyst, which is beneficial for mass and heat transfer between the catalyst and reactants, and can reduce the adsorption time of reactants on the catalyst.
[0059] To demonstrate the performance of MnTi@C as a MgH2 catalyst, MgH2-MnTi@C materials were prepared.
[0060] A method for preparing MgH2-MnTi@C material involves ball milling MnTi@C and MgH2 under argon conditions, with MnTi@C accounting for 10 wt% of the total mass, a ball-to-material mass ratio of 40:1, a ball milling speed of 400 rpm, and a ball milling time of 12 h.
[0061] To demonstrate the hydrogen desorption kinetics of MgH2-MnTi@C, PCT high-temperature gas desorption tests were conducted. Simultaneously, for comparison, PCT high-temperature gas desorption tests were performed on pure MgH2.
[0062] The test results for pure MgH2 are as follows: Figure 5 As shown, under a programmed heating rate of 3℃ / min, the initial hydrogen desorption temperature of pure MgH2 material is 298℃.
[0063] The test results of MgH2-MnTi@C are as follows: Figure 5 As shown, under a programmed heating rate of 3℃ / min, the initial hydrogen desorption temperature of the MgH2-MnTi@C material is 155℃.
[0064] Test results show that MnTi@C effectively improves the hydrogen desorption kinetics of MgH2.
[0065] To demonstrate the isothermal hydrogen adsorption kinetics of MgH2-MnTi@C, PCT high-temperature gas adsorption tests were conducted. Simultaneously, for comparison, PCT high-temperature gas adsorption tests were performed on pure MgH2.
[0066] The test results for pure MgH2 are as follows: Figure 6 As shown, under the conditions of hydrogen absorption temperature of 200℃, hydrogen absorption pressure of 24 bar, and hydrogen absorption time of 60 s, the hydrogen absorption capacity of pure MgH2 is only 0.177 wt%.
[0067] The test results of MgH2-MnTi@C are as follows: Figure 6As shown, under the conditions of hydrogen absorption temperature of 200℃, hydrogen absorption pressure of 24 bar, and hydrogen absorption time of 60 s, the hydrogen absorption capacity of MgH2-MnTi@C is 5.9 wt%.
[0068] Test results show that MnTi@C effectively improves the hydrogen absorption kinetics of MgH2.
[0069] To demonstrate the isothermal hydrogen desorption kinetics of MgH2-MnTi@C material, PCT high-temperature gas desorption tests were conducted at different temperatures. Meanwhile, for comparison, PCT high-temperature gas adsorption tests were performed on pure MgH2.
[0070] The test results for pure MgH2 are as follows: Figure 7 As shown, under the conditions of hydrogen release temperature of 300℃ and hydrogen release time of 180s, the hydrogen release amount of pure MgH2 is only 0.005wt%.
[0071] The test results of MgH2-MnTi@C are as follows: Figure 7 As shown, under the conditions of hydrogen release temperature of 300℃ and hydrogen release time of 180s, the hydrogen release amount of MgH2-MnTi@C is 5.3wt%.
[0072] Test results show that MnTi@C effectively improves the isothermal hydrogen desorption kinetics of MgH2.
[0073] To demonstrate the effect of Ti on catalytic performance, Comparative Example 1 is provided, showing Mn@C materials prepared without the addition of a Ti metal source.
[0074] Comparative Example 1
[0075] A method for preparing Mn@C material without adding Ti metal source. Unless otherwise specified, the steps are the same as in Example 1, except that: isopropyl titanate is not added in step 1, the material obtained in step 1 is named Mn-MOF, the material obtained in step 2 is named Mn@C, and the material obtained by ball milling is MgH2-Mn@C.
[0076] The XRD test results of Mn-MOF are as follows: Figure 1 As shown, the diffraction peaks of the synthesized Mn-MOF at 2θ = 10.5°, 19.2°, and 20.06° are consistent with the standard peaks of Mn-MOF, thus proving the successful synthesis of Mn-MOF. A comparison with the XRD results of MnTi-MOF in Example 1 reveals that the difference in diffraction peaks indicates that the addition of the Ti metal source altered the crystal structure of Mn-MOF.
[0077] The XRD test results of Mn@C are as follows: Figure 3As shown, Mn@C contains characteristic peaks of MnO. A comparison with the XRD test results of MnTi@C in Example 1 shows that adding a Ti metal source does not affect the form of Mn in the composite material.
[0078] The SEM test results of Mn@C are as follows: Figure 8 As shown, Mn@C exhibits a prismatic structure. However, during the preparation of the sample for SEM testing, it was observed that Mn@C partially dissolves in ethanol solution, indicating that Mn@C is unstable in ethanol. Comparison with the SEM test results of MnTi@C in Example 1 shows that adding a Ti source can transform the microstructure of the composite material from a prismatic structure to a hexagonal prism-pyramidal structure, thus regulating the microstructure. Furthermore, adding a Ti source can improve the stability of the composite material.
[0079] The test results of hydrogen desorption kinetics of MgH2-Mn@C are as follows: Figure 5 As shown, under a programmed heating rate of 3 °C / min, the initial hydrogen decomposition temperature of MgH2-Mn@C is 180 °C. Comparative analysis of the hydrogen decomposition kinetics test results of Example 1 and Comparative Example 1 reveals that MgH2-MnTi@C has a lower initial hydrogen decomposition temperature than MgH2-Mn@C. This phenomenon indicates that MnTi@C has better catalytic performance than Mn@C. Furthermore, it demonstrates that the addition of a Ti metal source resulted in a bimetallic synergistic catalytic effect, thereby improving the catalytic performance of Mn@C.
[0080] The test results of hydrogen absorption kinetics of MgH2-Mn@C are as follows: Figure 6 As shown, under the conditions of 24 bar, 200 °C, and a hydrogen absorption time of 60 s, the hydrogen absorption capacity of MgH2-Mn@C was only 0.282 wt%. Comparative analysis of the results of Example 1 and Comparative Example 2 reveals that MgH2-MnTi@C exhibits better hydrogen absorption kinetics than MgH2-Mn@C. This phenomenon indicates that MnTi@C has better catalytic performance than Mn@C. Furthermore, it demonstrates that due to the addition of the Ti metal source, Ti elements replace some of the Mn elements, making the Mn elements in MnTi@C more dispersed compared to Mn@C, thereby improving the catalytic performance of Mn@C.
[0081] To demonstrate the effect of Mn on catalytic performance, Comparative Example 2 is provided, showing Ti@C materials prepared without the addition of Mn metal sources.
[0082] Comparative Example 2
[0083] A method for preparing Ti@C material without adding Mn metal source is disclosed. Unless otherwise specified, the steps are the same as in Example 1, except that manganese chloride tetrahydrate is not added in step 1. The material obtained in step 1 is named Ti-MOF, the material obtained in step 2 is named Ti@C, and the material obtained by ball milling is MgH2-Ti@C.
[0084] The XRD test results of Ti-MOF are as follows: Figure 1 As shown, the diffraction peaks of the synthesized Ti-MOF at 2θ = 6.79°, 9.83°, and 11.69° are consistent with the standard peaks of Ti-MOF, thus proving the successful synthesis of Ti-MOF. A comparison with the XRD results of MnTi@C in Example 1 shows that the difference in diffraction peaks indicates that the addition of the Mn metal source altered the crystal structure of Ti-MOF.
[0085] The XRD test results of Ti@C are as follows: Figure 3 As shown, Ti@C contains characteristic peaks of TiO2. A comparison with the XRD test results of MnTi@C in Example 1 shows that adding a Mn metal source does not affect the form of Ti in the composite material.
[0086] The row SEM test results of Ti@C are as follows: Figure 9 As shown, Ti@C has a cylindrical structure. However, during the preparation of the sample for SEM testing, it was found that Ti@C partially dissolves in ethanol solution, indicating that Ti@C is unstable in ethanol. Comparison with the SEM test results of MnTi@C in Example 1 shows that adding a Mn metal source can transform the microstructure of the composite material from a cylindrical structure to a hexagonal prism-pyramidal structure, thus regulating the microstructure. Furthermore, adding a Mn metal source can improve the stability of the composite material.
[0087] The test results of hydrogen desorption kinetics of MgH2-Ti@C are as follows: Figure 5 As shown, under a programmed heating rate of 3℃ / min, the initial hydrogen desorption temperature of MgH2-Ti@C is 165℃. Comparative analysis of the hydrogen desorption kinetics test results of Example 1 and Comparative Example 2 reveals that the MgH2-MnTi@C material has a lower initial hydrogen desorption temperature than MgH2-Ti@C. This phenomenon indicates that MnTi@C has better catalytic performance than Ti@C. Furthermore, it demonstrates that the addition of a Ti metal source achieves a bimetallic synergistic catalytic effect, thereby improving the catalytic performance of Mn@C.
[0088] The test results of MgH2-Ti@C are as follows: Figure 6As shown, under the conditions of 24 bar, 200 °C, and a hydrogen absorption time of 60 s, the hydrogen absorption capacity of MgH2-Ti@C was only 4.1 wt%. Comparative analysis of the results of Example 1 and Comparative Example 2 shows that MgH2-MnTi@C exhibits better kinetic hydrogen absorption performance than MgH2-Ti@C. This phenomenon indicates that MnTi@C has better catalytic performance than Ti@C. Furthermore, it demonstrates that due to the addition of the Mn metal source, Mn elements replace some of the Ti elements, making the Ti elements in MnTi@C more dispersed compared to Ti@C, thereby improving the catalytic performance of Ti@C.
Claims
1. A method for preparing bimetallic MnTi-MOF derivative MnTi@C materials based on controlled crystal structure, characterized in that... Includes the following steps: Step 1, Preparation of MnTi-MOF: First, isopropyl titanate, MnCl2·4H2O, and terephthalic acid are placed in a mixed solvent to obtain a reaction solution, which is then stirred under certain conditions. After that, the reaction is carried out under certain conditions. Finally, the reaction product is centrifuged and washed under certain conditions. After centrifugation and washing, it is then vacuum dried under certain conditions to obtain MnTi-MOF. In step 1, the molar ratio of isopropyl titanate, MnCl2·4H2O and terephthalic acid is 1:1:
3. In step 1, the mixed solvent is obtained by mixing N,N-dimethylformamide (DMF) and methanol in a volume ratio of 9:
1. In step 1, the reaction conditions are: reaction temperature of 150 °C and reaction time of 16 h. Step 2, Preparation of MnTi@C: Under certain conditions, the MnTi-MOF obtained in Step 1 is calcined to obtain MnTi@C; In step 2, the calcination conditions are as follows: under argon atmosphere, the calcination temperature is 600-650 ℃, and the calcination time is 60-120 min. The resulting material is a bimetallic MnTi-MOF derivative MnTi@C with a regulated crystal structure. The MnTi-MOF has a regular hexagonal prism-pyramidal structure with a diameter of 3-5 micrometers and a length of 15-20 micrometers. The microstructure of the MnTi@C is a rough hexagonal prism-pyramidal structure with a diameter of 3-5 micrometers and a length of 15-20 micrometers.
2. The application of the MnTi@C material based on the bimetallic MnTi-MOF derivative with regulated crystal structure obtained by the preparation method of claim 1 as a MgH2 hydrogen storage catalyst, characterized in that: Based on the ball milling method, under certain conditions, MnTi@C and MgH2 are ball milled to meet a certain mass ratio to obtain MgH2-MnTi@C; The conditions for the ball milling method are as follows: the mass fraction of MnTi@C is 5-15 wt% of the total mass, under argon atmosphere, the ball-to-material mass ratio is (40-60):1, the ball milling speed is 400-500 rpm, and the ball milling time is 12-15 h. The initial hydrogen release temperature of the obtained MgH2-MnTi@C was 150-160℃ under a programmed heating rate of 3-5 ℃ / min. The obtained MgH2-MnTi@C exhibited a hydrogen absorption capacity of 5.5-6.1 wt% under the following conditions: hydrogen absorption pressure of 20-30 bar, hydrogen absorption temperature of 150-250 ℃, and hydrogen absorption time of 30-90 s. The hydrogen release amount of the obtained MgH2-MnTi@C was 5.0-5.6 wt% under the conditions of hydrogen release temperature of 250-350 ℃ and hydrogen release time of 120-240 s.