Carbon nanofiber loaded MnTi bimetallic microsphere as well as preparation method and application thereof

Abstract

The invention discloses a carbon nanofiber loaded MnTi bimetallic microsphere, which is prepared by the following steps: taking transition metal compounds of isopropyl titanate, manganese chloride tetrahydrate and polyvinylpyrrolidone (PVP) as raw materials, and obtaining the carbon nanofiber loaded MnTi bimetallic microsphere PVP-MnTi through an electrostatic spinning method; and then calcining is performed, so that the carbon nanofiber loaded MnTi bimetallic microsphere CNT-MnTi can be prepared. The preparation method comprises the following steps: 1, electrostatic spinning of PVP-MnTi; and 2, the preparation of the CNT-MnTi is carried out. When the CNT-MnTi-based magnesium hydride hydrogen storage material is applied as an MgH2 hydrogen storage catalyst, the CNT-MnTi and magnesium hydride are subjected to ball milling compounding, and the CNT-MnTi-based magnesium hydride hydrogen storage material can be obtained. Under the condition that the temperature programming rate is 3 DEG C / min, the initial hydrogen desorption temperature is 180-190 DEG C; under the conditions that the hydrogen absorption pressure is 20-30 bar, the hydrogen absorption temperature is 150-250 DEG C and the hydrogen absorption time is 200-600 s, the hydrogen absorption amount is 5.8-6.2 wt%; under the conditions that the hydrogen desorption temperature is 275-350 DEG C and the hydrogen desorption time is 240-360 seconds, the hydrogen desorption amount is 4.0-6.1 wt%.

Description

Technical Field

[0001] The invention relates to the technical field of hydrogen storage catalysis, and in particular to a carbon nanofiber-loaded MnTi bimetallic microsphere and a preparation method and application thereof. Background Art

[0002] MgH 2 As an efficient hydrogen storage material, it has a hydrogen storage content of 7.6 wt%, has the advantages of cyclic performance, non-toxicity, stability at room temperature and environmental friendliness. 2 There are problems such as high hydrogen absorption and desorption temperature and high activation energy, that is, slow hydrogen absorption and desorption kinetics. Therefore, it is necessary to add a catalyst to MgH 2 The kinetics of hydrogen absorption and desorption are improved. Since the direct introduction of the catalyst will cause agglomeration during the hydrogen absorption and desorption process, the current conventional technical method is to load the catalyst on a carrier or adjust it to a specific structure for improvement. Among them, the electrospun film has the advantages of large specific surface area and good dispersibility, which can effectively improve the dispersibility problem of the catalyst.

[0003] For example, existing literature 1 (Meng, Q.; Huang, Y.; Ye, J.; Xia, G.; Wang, G.; Dong, L.; Yang, Z.; Yu, X., Electrospun carbon nanofibers with in-situ encapsulated Ninanoparticles as catalyst for enhanced hydrogen storage ofMgH 2 .J.Alloy.Compd.2021,851.) synthesized a thin film material of carbon nanofibers wrapped with nickel particles by electrospinning and calcination, and then ball milled with MgH 2 Compound to obtain MgH 2 -10wt Ni@C composite material. A technical effect of a dehydrogenation capacity of 5.79wt% at 280°C was obtained. However, since there is only one metal element in the film of this technical solution, that is, a single metal film, even if the metal element used in this technology is a transition metal nickel element, there are still fewer electronic configurations, that is, the electronic distribution of metal ions is relatively simple and monotonous. Therefore, this technical solution has a lack of diversity in catalytic active sites, which leads to technical problems such as low catalytic efficiency and selectivity.

[0004] In order to solve the technical problems of low catalytic efficiency and selectivity caused by single metal film, it can be improved by preparing bimetallic film. The basic principle is that due to the presence of two metals at the same time, the electronic structures of the two metals affect each other, resulting in a synergistic catalytic effect, thereby achieving selectivity in the catalytic process and improving the catalytic efficiency; at the same time, the bimetallic film can better disperse the two transition metals in the structure, which plays a role in improving the catalytic effect of the catalyst. For example, the existing literature 2 (Wang, XS; Liu, MZ; Tian, ​​T.; Liu, F.; Wang, JL; Li, JP; Liu, G., Fibrous V / Nb bimetallic oxides with remarkable catalytic effect on hydrogen storage properties of MgH 2 .Int.J.Hydrog.Energy 2025,97,1168-1176.) discloses a method of adding PVP, vanadium and nickel elements in a ratio of 20:2:1 to ethanol, and synthesizing a film composed of carbon nanofiber-supported V / Nb bimetallic oxide by electrospinning and calcination as MgH 2 Catalytic material. This technical solution improves the catalytic efficiency and selectivity by introducing two metal elements and utilizing the synergistic catalytic effect of bimetallics. According to common knowledge in the technical field of the present invention, in the electrospinning technology, the concentration of the electrospinning solution has a significant impact on the technical characteristics represented by the viscosity of the solution, and thus has a significant impact on the technical effects of the materials obtained by electrospinning. Specifically, for the electrospinning solution containing bimetallic elements involved in the present invention, an increase in the element concentration will significantly increase the viscosity of the electrospinning solution. Therefore, in order to improve the dispersibility of metal elements and obtain nanofiber negative metal composite materials, that is, to solve the dispersibility problem, the technical solution adopted is to control / reduce the concentration of metal elements in the electrospinning solution, thereby improving the dispersibility. However, this solution directly leads to a small amount of metal elements added, which ultimately leads to the technical problem of low catalytic performance.

[0005] In addition, the type of metal element will also have a significant impact on the electrospinning preparation process and the properties of the subsequent materials. 2 There are few related prior arts for catalytic materials. Therefore, electrode materials that also involve adjusting electronic structure, namely, related prior arts for electrode materials based on electrospinning technology, are selected for analysis. Among them, prior art document 3 is for nickel element, prior art document 4 is for titanium element, and prior art document 5 is for manganese element, as follows.

[0006] Existing document 3 (Luo, Z.; Xia, Y.; Huang, J.; Zeng, H.; Chen, Y.; Chen, L.; Feng, Z.; Chen, Z., Flexible electrospun carbon nanofibers-Nickel disulfide@carbonnanofibers-Carbon nanofibers sandwich structure as binder-free anode for highperformance lithium-ion batteries. Surfaces and Interfaces 2024, 54.) adds nickel nitrate hexahydrate and polyacrylonitrile in a ratio of 2:3 to DMF, and prepares a carbon nanofiber-wrapped nickel composite material by electrospinning and calcination, obtaining a technical effect of a specific capacity of 881.1 mAh / g at a current density of 0.1 A / g.

[0007] Existing document 4 (Li, Y.; Du, J.; Sun, X.; Lan, D.; Cui, J.; Zhao, H.; Zhang, Y.; He, W., Preparation of TiO2 / nitrogen-doped CNF composites as high-performance lithium-ion battery anodes by electrospinning. Journal of Crystal Growth 2023, 624.) adds titanium dioxide and polyacrylonitrile in a ratio of 1:5 to DMF, and prepares carbon nanofiber-wrapped titanium composite materials by electrospinning and calcination, obtaining a technical effect of a specific capacity of 590.2 mAh / g at a current density of 0.1 A / g.

[0008] Existing document 5 (Tang, F.; He, T.; Zhang, H.; Wu, X.; Li, Y.; Long, F.; Xiang, Y.; Zhu, L.; Wu, J.; Wu, X., The MnO@N-doped carbon composite derived from electrospinning ascathode material for aqueous zinc ion battery. Journal of Electroanalytical Chemistry 2020, 873.) adds polyvinyl pyrrolidone and manganese acetate tetrahydrate to ethanol in a ratio of 1:1, and prepares carbon nanofiber-wrapped manganese composite materials by electrospinning and calcination, and obtains a technical effect of a specific capacity of 250.1 mAh / g at a current density of 0.1 A / g.

[0009] The above technical solutions all achieve the technical effect of improving dispersibility by electrospinning, the difference being that the metal elements are different, namely Ni, Ti and Mn. Among them, the technical effect of introducing Ni is better than that of introducing Ti and Mn. The reason is that Ni, as a Group VIII element, has a richer electronic structure than the sub-group elements Ti and Mn, and thus has a better electron transfer ability. Therefore, based on the above prior art, it can be concluded that the technical effect obtained by introducing Ni is better than that by introducing Ti and Mn.

[0010] In addition, the above technical solutions all have the technical problem of small amount of added metal elements. Summary of the invention

[0011] The purpose of the present invention is to provide a carbon nanofiber-loaded MnTi bimetallic microsphere and its preparation method and application. As described in the background technology, simply increasing the amount of metal element added will lead to an increase in the concentration of the electrospinning solution, thereby increasing the viscosity, and ultimately causing the resulting material to agglomerate, that is, it is impossible to increase the amount of metal element added to improve the catalytic performance. Therefore, the present invention adopts a method of introducing bimetallic elements, that is, not increasing the concentration of a single metal, to solve the technical problem of increasing the amount of metal element added, and at the same time, obtain the synergistic catalytic effect of the bimetal.

[0012] However, according to the inventor's research, the electrospinning solution obtained by this method also has the problem of agglomeration caused by increased viscosity, that is, the use of a bimetallic method cannot solve the technical problem of increasing the amount of metal elements added. Its basic principle is known from the common knowledge in the field that when Ni, Ti and Mn are introduced separately, the electrostatic attraction between the fibers in the electrospinning solution will be significantly enhanced, thereby causing fiber agglomeration; and according to the inventor's research, when a bimetallic element is introduced, the above-mentioned phenomenon of enhancing the electrostatic attraction between the fibers in the electrospinning solution also exists.

[0013] Based on the above research results, the present invention introduces Ti and Mn elements whose single metal properties are not optimal, and at the same time, adds PVP to react with Ti and Mn elements to form a stable complex; the obtained complex has good conductivity, so under the action of the electric field, bimetallic microspheres can be precipitated, thereby significantly reducing the electrostatic attraction between fibers in the electrospinning solution; finally, a three-dimensional network structure with a dispersed structure is obtained through electrospinning.

[0014] The technical solution for achieving the purpose of the present invention is:

[0015] A carbon nanofiber-loaded MnTi bimetallic microsphere, using transition metal compound isopropyl titanate, manganese chloride tetrahydrate, and polyvinyl pyrrolidone PVP as raw materials, through electrostatic spinning to obtain carbon nanofiber-loaded MnTi bimetallic microsphere PVP-MnTi; and then calcining to obtain carbon nanofiber-loaded MnTi bimetallic microsphere CNT-MnTi;

[0016] The microscopic morphology of the PVP-MnTi is a three-dimensional network structure composed of PVP nanofibers with a dispersed structure, and a microsphere structure composed of MnTi bimetallic is loaded on the three-dimensional network structure, the diameter of the PVP nanofibers is 100nm, and the diameter of the bimetallic microspheres is 1μm;

[0017] The CNT-MnTi microstructure is a three-dimensional network structure composed of carbon nanofibers with a dispersed structure, and a microsphere structure composed of MnTi bimetallic oxide is loaded on the three-dimensional network structure, the carbon nanofiber diameter is 100nm, and the bimetallic oxide microsphere diameter is 1μm.

[0018] A method for preparing carbon nanofiber-loaded MnTi bimetallic microspheres comprises the following steps:

[0019] Step 1, electrospinning of PVP-MnTi, first, isopropyl titanate, manganese chloride tetrahydrate MnCl 2 .4H 2O and polyvinyl pyrrolidone PVP meet a certain mass ratio, isopropyl titanate, manganese chloride tetrahydrate and PVP are placed in a mixed solvent, stirred under certain conditions to obtain an electrospinning solution, and then, under certain conditions, the electrospinning solution is electrospun to obtain PVP nanofiber-loaded MnTi bimetallic microspheres, referred to as PVP-MnTi;

[0020] In the step 1, the mass ratio of isopropyl titanate, manganese chloride tetrahydrate and PVP is 1:1.5:0.8.

[0021] In the step 1, the electrospinning solution is stirred for 450-550 min;

[0022] In the step 1, the electrospinning conditions are: positive voltage 14-15KV, negative voltage -3--4KV, propulsion speed 1.5-2.5cm / h, distance between the tip and the collector 8-12cm, and drum speed 80-100rpm;

[0023] In the step 1, the mixed solvent is a mixed solution of N,N-dimethylformamide DMF and ethanol in a volume ratio of 9:1;

[0024] Step 2, preparation of CNT-MnTi, calcining the PVP-MnTi obtained in step 1 under certain conditions to obtain carbon nanofiber-supported MnTi bimetallic microspheres, referred to as CNT-MnTi;

[0025] In the step 2, the calcination conditions are: under argon gas conditions, the calcination temperature is 600° C., and the calcination time is 90 minutes.

[0026] Carbon nanofiber-supported MnTi bimetallic microspheres as MgH 2 When the hydrogen storage catalyst is used, CNT-MnTi and magnesium hydride are ball-milled and compounded to obtain a magnesium hydride hydrogen storage material based on CNT-MnTi; the addition amount of the CNT-MnTi accounts for 7-12wt% of the total mass; the ball milling conditions are: under argon conditions, the ball-to-material ratio is (40-60):1, the ball milling speed is 350-450rpm, and the ball milling time is 10-15h.

[0027] A magnesium hydride hydrogen storage material based on CNT-MnTi has an initial dehydrogenation temperature of 180-190°C under the condition of a programmed heating rate of 3°C / min; a hydrogen absorption amount of 5.8-6.2wt% under the conditions of a hydrogen absorption pressure of 20-30bar, a hydrogen absorption temperature of 150-250°C, and a hydrogen absorption time of 200-600s; and a hydrogen release amount of 4.0-6.1wt% under the conditions of a hydrogen release temperature of 275-350°C and a hydrogen release time of 240-360s.

[0028] Therefore, the present invention can be found out through XRD, SEM, PCT and the like detection:

[0029] SEM testing shows that the microstructure of PVP-MnTi is a three-dimensional network structure composed of PVP nanofibers with a dispersed structure, and a microsphere structure composed of MnTi bimetallic is loaded on the three-dimensional network structure.

[0030] XRD test shows that CNT-MnTi contains both MnO and TiO 2 The diffraction peaks of , that is, after calcination, Mn and Ti elements exist in the form of oxides.

[0031] SEM testing shows that there is no substantial difference between the microstructure of CNT-MnTi and the PVP-MnTi obtained in step 1, and the calcination process does not affect the microstructure of the material.

[0032] PCT high temperature gas desorption test shows that under the condition of programmed heating rate of 3-5℃ / min, MgH 2 The initial dehydrogenation temperature of / CNT-MnTi material is 180-185℃.

[0033] PCT high temperature gas adsorption test shows that under the conditions of hydrogen absorption temperature of 150-250℃, hydrogen absorption pressure of 20-30bar, and hydrogen absorption time of 250-500s, MgH 2 The hydrogen absorption capacity of / CNT-MnTi is 5.5-6.2wt%.

[0034] PCT high temperature gas desorption tests at different temperatures show that under the conditions of dehydrogenation temperature of 275-350°C and dehydrogenation time of 240-360s, MgH 2 / CNT-MnTi has a hydrogen release amount of 4.0-6.1wt%.

[0035] Compared with the prior art, the present invention has the following advantages:

[0036] 1. By introducing non-optimal single metal elements such as manganese and titanium, the synergistic effect between the two metals is achieved, and at the same time, the amount of metal added is greatly increased to improve the catalytic performance of the catalyst;

[0037] 2. By adding manganese and titanium elements to the electrospinning solution, bimetallic microspheres are precipitated during electrospinning, which reduces the electrostatic attraction between nanofibers, reduces the agglomeration of nanofibers, and improves the dispersibility of the material;

[0038] 3. The raw materials used in the present invention are all industrially produced chemical raw materials, which are available in the market and easy to obtain. The process for synthesis is simple, the reaction cycle is short, and the reaction process has low energy consumption and low pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 is the SEM image of PVP-MnTi in Example 1;

[0040] Figure 2 XRD diagrams of CNT-MnTi in Example 1, CNT-Mn in Comparative Example 1, CNT-Ti in Comparative Example 2, and CNT-MnTi-1.5 in Comparative Example 3;

[0041] Figure 3 is the SEM image of CNT-MnTi in Example 1;

[0042] Figure 4 is MgH in Example 1 2 / CNT-MnTi, MgH in Comparative Example 1 2 / CNT-Mn, MgH in Comparative Example 2 2 / CNT-Ti, MgH in Comparative Example 3 2 / CNT-MnTi-1.5 and pure MgH 2 Temperature-dependent hydrogen release performance diagram

[0043] Figure 5 is MgH in Example 1 2 / CNT-MnTi, MgH in Comparative Example 1 2 / CNT-Mn, MgH in Comparative Example 2 2 / CNT-Ti, MgH in Comparative Example 3 2 / CNT-MnTi-1.5 and pure MgH 2 Isothermal hydrogen absorption performance diagram;

[0044] Figure 6 is MgH in Example 1 2 / Isothermal hydrogen desorption performance diagram of CNT-MnTi at different temperatures;

[0045] Figure 7 is the SEM image of CNT-Mn in Comparative Example 1;

[0046] Figure 8 is the SEM image of CNT-Ti in Comparative Example 2;

[0047] Fig. 9 This is the SEM image of CNT-MnTi-1.5 in Comparative Example 3. DETAILED DESCRIPTION

[0048] The present invention is further described in detail through embodiments and in conjunction with the accompanying drawings, but the present invention is not limited thereto.

[0049] Example 1

[0050] A method for preparing carbon nanofiber-loaded MnTi bimetallic microspheres comprises the following steps:

[0051] Step 1, electrospinning of PVP-MnTi, first, isopropyl titanate, manganese chloride tetrahydrate MnCl 2 .4H 2 The mass ratio of O and polyvinyl pyrrolidone PVP is 1:1.5:0.8, isopropyl titanate, manganese chloride tetrahydrate and PVP are placed in a mixed solvent, stirred for 480 min to obtain an electrospinning solution, and then, under the conditions of positive voltage 14 KV, negative voltage -3 KV, propulsion speed 2 cm / h, distance between the tip and the collector 10 cm, and drum speed 80 rpm, the electrospinning solution is electrospun to obtain PVP nanofiber-loaded MnTi bimetallic microspheres, referred to as PVP-MnTi;

[0052] The mixed solvent is a mixed solution of N,N-dimethylformamide DMF and ethanol in a volume ratio of 9:1;

[0053] In order to verify the microstructure of PVP-MnTi, SEM test was carried out. The test results are shown in Figure 1 As shown, the microstructure of PVP-MnTi is a three-dimensional network structure composed of PVP nanofibers with a dispersed structure, and a microsphere structure composed of MnTi bimetallic is loaded on the three-dimensional network structure, wherein the diameter of the PVP nanofibers is 100nm and the particle size of the MnTi bimetallic microspheres is 1μm.

[0054] Step 2, preparation of CNT-MnTi, calcining the PVP-MnTi obtained in step 1 under argon conditions at a calcination temperature of 600°C and a calcination time of 90 minutes to obtain carbon nanofiber-loaded MnTi bimetallic microspheres, referred to as CNT-MnTi.

[0055] In order to prove the composition of CNT-MnTi, XRD test was carried out. The test results are shown in Figure 2 As shown, CNT-MnT contains both MnO and TiO 2 The test results show that after calcination in step 2, Mn and Ti elements exist in the form of oxides.

[0056] In order to verify the microstructure of CNT-MnTi, SEM test was performed. The test results are shown in Figure 3 As shown, the microstructure of CNT-MnTi is not substantially different from that of PVP-MnTi obtained in step 1. The test results show that the calcination process in step 2 does not affect the microstructure of the material.

[0057] In order to demonstrate that CNT-MnTi as MgH 2 The performance of the catalyst was investigated by preparing CNT-MnTi based magnesium hydride hydrogen storage material for hydrogen absorption and desorption performance testing.

[0058] A preparation method of magnesium hydride hydrogen storage material based on CNT-MnTi comprises the following steps: under argon conditions, CNT-MnTi and MgH are mixed under the conditions that the addition amount of CNT-MnTi accounts for 10wt% of the total mass, the ball-to-material ratio is 40:1, the ball milling speed is 400rpm, and the ball milling time is 12h. 2 By ball milling, CNT-MnTi-based magnesium hydride hydrogen storage material can be obtained, referred to as MgH 2 / CNT-MnTi.

[0059] To prove that MgH 2 / CNT-MnTi desorption kinetics, PCT high temperature gas desorption test was carried out. At the same time, for comparison, pure MgH 2 Conduct PCT high temperature gas desorption test.

[0060] Pure MgH 2 The test results are as follows Figure 4 As shown, under the condition of program heating rate of 3℃ / min, pure MgH 2 The initial hydrogen release temperature is 298°C;

[0061] MgH 2 / CNT-MnTi test results are as follows Figure 4 As shown in the figure, under the condition of program heating rate of 3℃ / min, MgH 2 / The initial hydrogen desorption temperature of CNT-MnTi is 185 °C;

[0062] The test results show that the introduction of MgH 2 / CNT-MnTi as a catalyst can significantly reduce MgH 2 The initial dehydrogenation temperature is 113°C, that is, MgH 2 / CNT-MnTi can significantly increase the MgH 2 The hydrogen release kinetics.

[0063] To prove that MgH 2 / CNT-MnTi isothermal hydrogen absorption kinetics, PCT high temperature gas adsorption test was carried out. At the same time, for comparison, pure MgH 2 Perform PCT high temperature gas adsorption test.

[0064] Pure MgH 2 The test results are as follows Figure 5As shown in the figure, under the conditions of hydrogen absorption temperature of 200 °C, hydrogen absorption pressure of 24 bar, and hydrogen absorption time of 60 s, pure MgH 2 The hydrogen absorption capacity is only 0.177wt%, that is, the hydrogen absorption performance is negligible;

[0065] MgH 2 / CNT-MnTi test results are as follows Figure 5 As shown in the figure, under the conditions of hydrogen absorption temperature of 200°C, hydrogen absorption pressure of 24 bar, and hydrogen absorption time of 500 s, MgH 2 / The hydrogen absorption capacity of CNT-MnTi is 6.2wt%;

[0066] The test results show that the introduction of MgH 2 / CNT-MnTi as a catalyst can significantly increase the MgH 2 The hydrogen absorption capacity, i.e. MgH 2 / CNT-MnTi can significantly increase the MgH 2 Hydrogen absorption kinetics.

[0067] To prove that MgH 2 / CNT-MnTi isothermal hydrogen desorption kinetics. PCT high temperature gas desorption tests were carried out at different temperatures. At the same time, for comparison, pure MgH 2 Perform PCT high temperature gas adsorption test.

[0068] Pure MgH 2 The test results are as follows Figure 6 As shown in the figure, under the conditions of dehydrogenation temperature of 300℃ and dehydrogenation time of 180s, pure MgH 2 The amount of hydrogen released is only 0.005wt%; that is, the hydrogen absorption performance can be ignored.

[0069] MgH 2 / CNT-MnTi test results are as follows Figure 6 As shown in the figure, under the conditions of dehydrogenation temperature of 325℃ and dehydrogenation time of 240s, MgH 2 The hydrogen release amount of / CNT-MnTi is 5.9wt%.

[0070] The test results show that CNT-MnTi can significantly increase the MgH 2 Isothermal hydrogen desorption kinetics.

[0071] In order to demonstrate the influence of each component on the performance, Comparative Examples 1 and 2 are provided, which are composite materials prepared by introducing Mn element and Ti element separately.

[0072] Comparative Example 1

[0073] A method for preparing a CNT-Mn composite material into which Mn element is introduced alone, wherein the steps not specifically described are the same as those in Example 1, except that: in the step 1, isopropyl titanate is not added, the material obtained in the step 1 is named PVP-Mn, the material obtained in the step 2 is named CNT-Mn, and the obtained magnesium hydride hydrogen storage material is named MgH 2 / CNT-Mn.

[0074] The XRD test results of CNT-Mn are as follows Figure 2 As shown, CNT-Mn contains the diffraction peak of MnO, which proves that CNT-Mn is successfully synthesized. Compared with Example 1, it can be seen that the introduction of Ti element does not affect the existence form of Mn element in the composite material.

[0075] The SEM test results of CNT-Mn are as follows Figure 7 As shown, although the basic microscopic morphology of CNT-Mn still presents a three-dimensional network structure and a microsphere structure, the nanofibers have serious agglomeration phenomenon, and the microspheres are wrapped by the nanofibers due to the agglomeration of the nanofibers. Compared with Example 1, it can be seen that the introduction of the Ti element can transform the microscopic morphology of the composite material from an agglomerated network structure to a dispersed three-dimensional network structure, that is, it has the effect of improving dispersibility and then adjusting the microscopic morphology.

[0076] MgH 2 The test results of hydrogen desorption kinetics of CNT-Mn are as follows: Figure 4 As shown in the figure, under the condition of program heating rate of 3℃ / min, MgH 2 The initial dehydrogenation temperature of / CNT-Mn is 260°C. Compared with Example 1, it can be seen that the introduction of Ti element can increase the MgH 2 / CNT-Mn hydrogen release kinetics, that is, improve the catalytic performance of CNT-Mn. The reason is that by introducing the Ti metal source, CNT-Mn obtains a bimetallic synergistic catalytic effect, thereby improving the catalytic performance of CNT-Mn, that is, proves the role of the Ti element in the technical solution.

[0077] MgH 2 The test results of hydrogen absorption kinetics of CNT-Mn are as follows: Figure 5 As shown in the figure, under the conditions of hydrogen absorption temperature of 200°C, hydrogen absorption pressure of 24 bar and hydrogen absorption time of 500 s, MgH 2 / CNT-Mn has a hydrogen absorption capacity of only 2.7 wt%. Compared with Example 1, it can be seen that the introduction of Ti element can significantly increase the hydrogen absorption capacity of MgH 2The isothermal hydrogen absorption kinetics of CNT-Mn / CNT-Mn increased by 129.6%, that is, the catalytic performance of CNT-Mn was improved. The reason is that the introduction of Ti metal source replaced part of the Mn element, making the Mn element in CNT-MnTi more dispersed than that in CNT-Mn, resulting in the Mn element and MgH 2 The larger the contact area, the more complete the reaction, thus improving the catalytic efficiency of CNT-Mn, which proves the role of the Ti element in the technical solution.

[0078] Comparative Example 2

[0079] A method for preparing a CNT-Ti composite material with Ti element introduced alone, wherein the steps not specifically described are the same as those in Example 1, except that: in step 1, manganese chloride tetrahydrate is not added, the material obtained in step 1 is named PVP-Ti, the material obtained in step 2 is named CNT-Ti, and the obtained magnesium hydride hydrogen storage material is named MgH 2 / CNT-Ti.

[0080] The XRD test results of CNT-Ti are as follows Figure 2 As shown, CNT-Ti contains TiO 2 The diffraction peak of CNT-Ti is shown in Figure 1, which proves that CNT-Ti is successfully synthesized. Compared with Example 1, it can be seen that the introduction of Mn element does not affect the existence form of Ti element in the composite material.

[0081] The SEM test results of CNT-Ti are as follows Figure 8 As shown, the basic microscopic morphology of CNT-Ti is similar to that of CNT-Mn, that is, the agglomerated three-dimensional network structure wraps the microspheres. The conclusions obtained from the test results are similar to those of Comparative Example 1, that is, the introduction of Ti elements can improve the dispersibility and thus adjust the microscopic morphology.

[0082] From the SEM test results of Example 1 and Comparative Examples 1 and 2, it can be seen that the introduction of Mn element and Ti element alone both cause serious agglomeration, and a three-dimensional network structure with a dispersed structure cannot be obtained, which proves that the simultaneous introduction of Mn element and Ti element causes substantial changes in the microscopic morphology.

[0083] MgH 2 The test results of hydrogen desorption kinetics of CNT-Ti are as follows: Figure 4 As shown in the figure, under the condition of program heating rate of 3℃ / min, MgH 2 The initial dehydrogenation temperature of / CNT-Ti is 220°C. Compared with Example 1, it can be seen that the introduction of Mn element can increase the MgH 2 / CNT-Ti's hydrogen release kinetics, that is, improving the catalytic performance of CNT-Ti. The reason is that by introducing the Mn metal source, CNT-Ti obtains a bimetallic synergistic catalytic effect, thereby improving the catalytic performance of CNT-Ti, that is, proving the role of the Mn element in the technical solution.

[0084] MgH 2 / CNT-Ti hydrogen absorption kinetics test results are as follows Figure 5 As shown in the figure, under the conditions of hydrogen absorption temperature of 200 °C, hydrogen absorption pressure of 24 bar, and hydrogen absorption time of 500 s, MgH 2 / CNT-Ti has a hydrogen absorption capacity of only 2.1 wt%. Compared with Example 1, it can be seen that the introduction of Mn element can significantly increase the hydrogen absorption capacity of MgH 2 The isothermal hydrogen absorption kinetics of CNT-Ti was improved by 195.2%, that is, the catalytic performance of CNT-Ti was improved. The reason is that the introduction of Mn metal source replaced part of the Ti element, making the Ti element in CNT-MnTi more dispersed than that in CNT-Ti, resulting in the Ti element and MgH 2 The larger the contact area, the more complete the reaction, thus improving the catalytic efficiency of CNT-Ti, which proves the role of the Mn element in the technical solution.

[0085] Based on the test results of hydrogen desorption kinetics and hydrogen absorption kinetics of Example 1 and Comparative Examples 1 and 2, it can be seen that the introduction of Mn element and Ti element alone cannot effectively improve the catalytic performance, and only the simultaneous introduction of Mn element and Ti element can significantly improve the catalytic performance, which proves that there is a synergistic effect between the Mn element and the Ti element in the technical solution.

[0086] In order to demonstrate the effect of the PVP addition ratio on the performance, Comparative Example 3 is provided, in which a CNT-MnTi composite material is prepared by increasing the PVP addition ratio.

[0087] Comparative Example 3

[0088] A method for preparing a CNT-MnTi composite material with a relatively high PVP addition ratio, wherein the steps not specifically described are the same as those in Example 1, except that: in the step 1, the mass ratio of isopropyl titanate, manganese chloride tetrahydrate and PVP is 1:1.5:1.5, the material obtained in the step 1 is named PVP-MnTi-1.5, the material obtained in the step 2 is named CNT-MnTi-1.5, and the obtained magnesium hydride hydrogen storage material is named MgH 2 / CNT-MnTi-1.5.

[0089] The XRD test results of CNT-MnTi-1.5 are as follows Figure 2 As shown, CNT-MnTi-1.5 contains MnO and TiO2 The characteristic peaks of CNT-MnTi-1.5 are shown in Table 1, which proves that CNT-MnTi-1.5 is successfully synthesized. Compared with Example 1, it can be seen that changing the addition ratio of PVP does not affect the existence form of Mn and Ti elements in the composite material.

[0090] The SEM test results of CNT-MnTi-1.5 are as follows Fig. 9 As shown, although CNT-MnTi-1.5 still presents a three-dimensional network structure, the nanofibers are agglomerated and there are no microspheres. Compared with Example 1, when the PVP addition ratio is too high, in addition to causing the nanofibers to agglomerate, more importantly, the Mn and Ti elements cannot form a microsphere structure, which proves that the addition ratio of PVP can significantly change the microscopic morphology.

[0091] MgH 2 The test results of hydrogen desorption kinetics of / CNT-MnTi-1.5 are as follows Figure 4 As shown in the figure, under the condition of program heating rate of 3℃ / min, MgH 2 The initial dehydrogenation temperature of / CNT-MnTi-1.5 is 190°C. Compared with Example 1, when the proportion of PVP added is too high, the initial dehydrogenation temperature increases, that is, the performance deteriorates. The reason for this, combined with the SEM test results, is that the nanofibers have serious agglomeration, which leads to the formation of MgH 2 / The initial hydrogen desorption temperature of CNT-MnTi-1.5 increases instead, that is, the catalytic performance of CNT-MnTi-1.5 decreases.

[0092] MgH 2 The test results of hydrogen absorption kinetics of / CNT-MnTi-1.5 are as follows Figure 5 As shown in the figure, under the conditions of hydrogen absorption temperature of 200 °C, hydrogen absorption pressure of 24 bar, and hydrogen absorption time of 500 s, MgH 2 The hydrogen absorption capacity of / CNT-MnTi-1.5 is 6.0wt%. Compared with Example 1, it can be seen that when the PVP addition ratio is too high, the hydrogen absorption capacity is reduced. The reason is consistent with the conclusion obtained from the hydrogen release kinetics test.

[0093] Therefore, it can be seen from Example 1 and Comparative Example 3 that too much PVP addition ratio will lead to agglomeration of nanofibers, which proves the role of adjusting the PVP addition ratio in the technical solution.

Claims

1. A carbon nanofiber-loaded MnTi bimetallic microsphere, characterized in that: Using transition metal compound isopropyl titanate, manganese chloride tetrahydrate and polyvinyl pyrrolidone PVP as raw materials, carbon nanofiber-loaded MnTi bimetallic microspheres PVP-MnTi are obtained by electrospinning; and carbon nanofiber-loaded MnTi bimetallic microspheres CNT-MnTi are obtained by calcination.

2. The carbon nanofiber-loaded MnTi bimetallic microspheres according to claim 1, characterized in that: The microscopic morphology of the PVP-MnTi is a three-dimensional network structure composed of PVP nanofibers with a dispersed structure, and a microsphere structure composed of MnTi bimetallic is loaded on the three-dimensional network structure, the diameter of the PVP nanofibers is 100nm, and the diameter of the bimetallic microspheres is 1μm; The CNT-MnTi microstructure is a three-dimensional network structure composed of carbon nanofibers with a dispersed structure, and a microsphere structure composed of MnTi bimetallic oxide is loaded on the three-dimensional network structure, the carbon nanofiber diameter is 100nm, and the bimetallic oxide microsphere diameter is 1μm.

3. A method for preparing carbon nanofiber-loaded MnTi bimetallic microspheres, characterized in that The following steps are involved: Step 1, electrospinning of PVP-MnTi, first, isopropyl titanate, manganese chloride tetrahydrate MnCl2.4H2O and polyvinyl pyrrolidone PVP meet a certain mass ratio, isopropyl titanate, manganese chloride tetrahydrate and PVP are placed in a mixed solvent, stirred under certain conditions to obtain an electrospinning solution, and then, under certain conditions, the electrospinning solution is electrospun to obtain PVP nanofiber-loaded MnTi bimetallic microspheres, referred to as PVP-MnTi; In the step 1, the mixed solvent is a mixed solution of N,N-dimethylformamide DMF and ethanol in a volume ratio of 9:1; Step 2, preparation of CNT-MnTi, calcining the PVP-MnTi obtained in step 1 under certain conditions to obtain carbon nanofiber-loaded MnTi bimetallic microspheres, referred to as CNT-MnTi.

4. The preparation method according to claim 3, characterized in that: In the step 1, the mass ratio of isopropyl titanate, manganese chloride tetrahydrate and PVP is 1:1.5:0.8; In the step 1, the electrospinning solution is stirred for 450-550 min; In the step 1, the conditions for electrospinning are: positive voltage 14-15 KV, negative voltage -3--4 KV, propulsion speed 1.5-2.5 cm / h, distance between the tip and the collector 8-12 cm, and drum speed 80-100 rpm.

5. The preparation method according to claim 3, characterized in that: In the step 2, the calcination conditions are: under argon gas conditions, the calcination temperature is 600° C., and the calcination time is 90 minutes.

6. The carbon nanofiber-loaded MnTi bimetallic microspheres according to claim 1, characterized in that: When used as a MgH2 hydrogen storage catalyst, CNT-MnTi and magnesium hydride are ball-milled and compounded to obtain a magnesium hydride hydrogen storage material based on CNT-MnTi.

7. The carbon nanofiber-loaded MnTi bimetallic microspheres according to claim 6, characterized in that: The addition amount of CNT-MnTi accounts for 7-12wt% of the total mass.

8. The carbon nanofiber-loaded MnTi bimetallic microspheres according to claim 6, characterized in that: The ball milling conditions are as follows: under argon conditions, the ball-to-material ratio is (40-60):1, the ball milling speed is 350-450 rpm, and the ball milling time is 10-15 h.

9. A magnesium hydride hydrogen storage material based on CNT-MnTi, characterized in that: When used as a MgH2 hydrogen storage catalyst, the initial hydrogen release temperature is 180-190°C under the condition of a programmed heating rate of 3°C / min.

10. A magnesium hydride hydrogen storage material based on CNT-MnTi, characterized in that: When used as a MgH2 hydrogen storage catalyst, the hydrogen absorption amount is 5.8-6.2wt% under the conditions of hydrogen absorption pressure of 20-30bar, hydrogen absorption temperature of 150-250℃, and hydrogen absorption time of 200-600s; Under the conditions of hydrogen desorption temperature of 275-350°C and hydrogen desorption time of 240-360s, the amount of hydrogen desorption is 4.0-6.1wt%.

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