A flower cluster-like Ni3Fe / TiO2 composite material, its preparation method and application
The flower-like Ni3Fe/TiO2 composite material addresses agglomeration issues in MgH2 by using TiO2 as a catalyst support and grinding aid, achieving lower desorption temperatures and improved hydrogen storage performance.
Patent Information
- Application Number
- CN202310273090.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-03-20
- Publication Date
- 2025-07-15
- Estimated Expiration
- 2043-03-20
AI Technical Summary
In the prior art, MgH2 has high thermal stability and slow kinetic speed. There are agglomeration problems with nanoification and catalyst doping methods, resulting in a degradation of hydrogen storage performance.
The Ni3Fe/TiO2 composite material was prepared by hydrothermal and ball milling technology to enhance the contact area and dispersion of the catalyst with MgH2, and the catalytic action and grinding effect of TiO2 were used to improve the dehydrogenation performance of MgH2.
It effectively reduces the initial hydrogen discharge temperature of MgH2, increases the hydrogen discharge and hydrogen absorption, and maintains good cycle stability, achieving better catalytic performance of MgH2 hydrogen storage.
Smart Images
Figure CN116374950B_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of hydrogen storage materials, and particularly relates to a flower cluster-like Ni3Fe / TiO2 composite material, a preparation method thereof, and an application thereof. Background Art
[0002] Magnesium hydride MgH2 has a hydrogen storage capacity of 7.6 wt% and reversibility, but its high thermal stability and slow kinetics limit the practical application of MgH2. To solve these problems, improvement can be achieved through nanosizing, catalyst doping, and alloying.
[0003] Among them, doping a catalyst is the most effective method to improve the dehydrogenation performance of MgH2, especially doping with transition metal catalysts. For example, in the existing literature 1 (Cong Peng, Yongtao Li, Qingan Zhang. Enhanced hydrogen desorption properties of MgH2 by highly dispersed Ni: The role of in-situ hydrogenolysis of nickelocene in ball milling process. Journal of Alloys and Compounds, 10.1016 / j.jallcom.2021.163547.), the kinetic performance of MgH2 was improved by ball milling Ni nanoparticles with MgH2, and the initial hydrogen desorption temperature of MgH2 was reduced to 250 °C, which proves that the transition metal Ni can effectively improve the kinetic performance of MgH2. The method of doping transition metals used in this technical solution is the ball milling method. In such a method, the material will agglomerate during ball milling, resulting in a significant reduction in kinetic performance and thus a significant reduction in hydrogen storage performance.
[0004] At present, the main method to solve agglomeration is to add appropriate carrier materials to increase the dispersibility of nanoparticle materials. Classified by the type of carrier material, it mainly includes: carbon materials, metal-organic frameworks, metal compounds, etc. For example, in the existing literature 2 (Jiangchuan Liu, Zhongliang Ma, Zhibing Liu. Synergistic effect of rGO supported Ni3Fe on hydrogen storage performance of MgH2. International Journal of Hydrogen Energy. 10.1016 / j.ijhydene.2020.04.104.), through hydrothermal reaction, Ni3Fe was uniformly anchored on the surface of rGO, suppressing the aggregation of nanoparticles during the ball milling process and reducing the initial temperature of MgH2 to 185 °C. The problem with this technical solution is that rGO, as a carrier material, has no catalytic effect on MgH2 itself. Moreover, the carrier can only improve the dispersibility of Ni3Fe during the process of loading Ni3Fe on the surface of rGO, but cannot improve the dispersibility of Ni3Fe or Ni3Fe / rGO on the surface of MgH2 during the ball milling process.
[0005] According to the research of the inventors, the selected carrier material can be a material with catalytic performance. At the same time, it has a specific microscopic morphology and can act as a grinding aid during the ball milling process, further reducing the initial hydrogen release temperature of MgH2. Summary of the Invention
[0006] The purpose of the present invention is to provide a flower cluster-like Ni3Fe / TiO2 composite material, its preparation method and application. In view of the technical problems existing in the prior art, the following principles and methods are adopted to solve the above problems:
[0007] 1. Since transition metal single nanoparticle can effectively improve the initial hydrogen release temperature of MgH2, but metal nanoparticles are prone to agglomeration during synthesis, ball milling and reaction processes, a carrier is selected to limit the agglomeration of metal nanoparticles, enabling the metal particles to be in full contact with MgH2 during the ball milling and reaction processes, thereby improving the dehydrogenation performance of MgH2;
[0008] 2. Flower cluster-like TiO2 is selected as the carrier, which can not only act as a grinding aid to promote the uniform growth of Ni3Fe particles on the surface of MgH2, thereby increasing the contact area between the catalyst and MgH2 to improve the dehydrogenation performance. Moreover, flower cluster-like TiO2 also has a catalytic effect on MgH2 and can co-catalyze MgH2 with Ni3Fe.
[0009] In order to achieve the above invention purpose, the technical solution adopted by the present invention is:
[0010] A flower cluster-like Ni3Fe / TiO2 composite material is composed of flower cluster-like TiO2 and Ni3Fe particles in-situ prepared on its surface. The flower cluster-like TiO2 is prepared by first preparing TiO2 / SiO2 and then forming hollow flower cluster-like TiO2.
[0011] The microstructure of the TiO2 / SiO2 is hollow spherical, with a size of 50 - 70 nm; the microstructure of the flower cluster-like TiO2 is a hollow flower cluster-like structure, with a size of 200 - 500 nm; the Ni3Fe particles are loaded on the surface of the flower cluster-like TiO2, with a size of 3 - 5 μm.
[0012] A preparation method of a flower cluster-like Ni3Fe / TiO2 composite material includes the following steps:
[0013] Step 1, preparation of the TiO2 / SiO2 precursor. First, oleylamine and absolute ethanol are mixed and stirred to obtain a mixture. Then, tetrabutyl titanate, tetraethyl orthosilicate, and H2O are successively and slowly dropped into the mixture and allowed to stand. After that, the precipitate obtained by standing is centrifuged, washed, and dried, and then calcined under certain conditions to obtain the TiO2 / SiO2 precursor.
[0014] In step 1, the volume ratio of oleylamine, absolute ethanol, tetrabutyl titanate, tetraethyl orthosilicate, and H2O is 1.5:200:5:10:1.
[0015] In step 1, the stirring time is 30 - 60 min, and the standing time is 10 - 12 h; the calcination conditions are that under air conditions, the calcination temperature is 450 - 500 °C, and the holding time is 2 - 3 h.
[0016] Step 2, preparation of flower cluster-like TiO2. First, the TiO2 / SiO2 precursor obtained in step 1 is placed in a KOH solution and subjected to a first hydrothermal reaction under certain conditions. The obtained precipitate is centrifuged, washed, and dried. Then, it is soaked in an HCl solution under certain conditions, and the soaked precipitate is centrifuged, washed, and dried. Finally, it is calcined under certain conditions to obtain flower cluster-like TiO2.
[0017] In step 2, the mass ratio of the TiO2 / SiO2 precursor to KOH is 1:20, the concentration of the KOH solution is 2 mol / l; the concentration of the HCl solution is 0.12 mol / L, and the soaking time is 2 - 3 h.
[0018] In step 2, the conditions of the first hydrothermal reaction are that the hydrothermal temperature is 100 - 120 °C, and the hydrothermal time is 20 - 24 h.
[0019] In Step 2, the conditions for the first calcination are as follows: under air conditions, the calcination temperature is 300 - 350 °C, and the calcination time is 2 - 3 h;
[0020] Step 3: Preparation of the flower cluster-like Ni3Fe / TiO2 composite material. Nickel nitrate hexahydrate, ferric nitrate nonahydrate, urea, and ammonium fluoride with a certain mass ratio are added to methanol and stirred to dissolve, obtaining Solution A. At the same time, the flower cluster-like TiO2 obtained in Step 2 is added to ionized water at a certain ratio and ultrasonicated to obtain Solution B. Then, Solution B is slowly added dropwise to Solution A, and a second hydrothermal reaction is carried out under certain conditions. After the obtained product is centrifuged, washed, and dried, a second calcination is carried out under certain conditions to obtain the flower cluster-like Ni3Fe / TiO2 composite material, named Ni3Fe / TiO2.
[0021] In Step 3, the mass ratio of nickel nitrate hexahydrate, ferric nitrate nonahydrate, urea, ammonium fluoride, and flower cluster-like TiO2 is 2:1:1.2:0.1:0.25;
[0022] In Step 3, the conditions for the second hydrothermal reaction are as follows: the hydrothermal temperature is 100 - 140 °C, and the hydrothermal time is 8 - 10 h;
[0023] In Step 3, the conditions for the second calcination are as follows: under a hydrogen-argon mixed atmosphere condition, the calcination temperature is 450 - 500 °C, and the calcination time is 2 - 3 h.
[0024] A preparation method of a MgH2-based hydrogen storage material based on Ni3Fe / TiO2 includes the following steps: under argon conditions throughout the process, Ni3Fe / TiO2 and MgH2 are mixed and then subjected to forward and reverse ball milling under certain conditions to obtain the MgH2-based hydrogen storage material based on Ni3Fe / TiO2, named MgH2-Ni3Fe / TiO2;
[0025] The addition amount of Ni3Fe / TiO2 is 5 wt%; the conditions for the forward and reverse ball milling are as follows: the ball-to-material ratio is 30:1, the ball milling speed is 400 rpm, the total ball milling time is 10 h, the single ball milling time is 12 min, and the ball milling interval is 6 min.
[0026] An application of a MgH2-based hydrogen storage material based on Ni3Fe / TiO2 as a hydrogen storage material. The doping amount of Ni3Fe / TiO2 is 5 wt%, the initial dehydrogenation temperature is 155 - 175 °C; the dehydrogenation amount at 300 °C is 6.9 - 7.1 wt%; the hydrogen absorption amount at 100 °C is 4.2 - 4.8 wt%; the retention rate after 15 cycles is 96 - 98%.
[0027] The technical effects of the present invention are tested, and the specific content is as follows:
[0028] It can be known from the XRD detection of the present invention that the TiO2 / SiO2 precursor, flower cluster-like TiO2, and Ni3Fe / TiO2 are successfully synthesized.
[0029] It can be known from the SEM and EDS detections of the present invention that the TiO2 / SiO2 precursor is a hollow sphere with a diameter of 50-70 nm, TiO2 is in a circular flower cluster shape, and Ni3Fe / TiO2 is that Ni3Fe nanoparticles are evenly dispersed on the surface of the flower cluster-like TiO2.
[0030] It can be known from the TG detection of the present invention that when the doping amount of Ni3Fe / TiO2 is 3-7 wt%, the initial hydrogen release temperature is 155-175 °C.
[0031] It can be known from the dehydrogenation detection of the present invention that when the doping amount of Ni3Fe / TiO2 is 5 wt%, at the hydrogen release temperatures of 300, 285, and 270 °C, the hydrogen release amount is 6.5-7.0 wt%.
[0032] It can be known from the hydrogen absorption detection of the present invention that when the doping amount of Ni3Fe / TiO2 is 5 wt%, at the hydrogen release temperatures of 100, 125, and 150 °C, the hydrogen absorption amount is 4.0-5.6 wt%.
[0033] It can be known from the dehydrogenation cycle detection of the present invention that when the doping amount of Ni3Fe / TiO2 is 5 wt%, the dehydrogenation temperature is 300 °C, and the hydrogen pressure is 2 Mpa, the hydrogen capacity remains at 6.74 wt% after fifteen cycles.
[0034] Therefore, the flower cluster-like Ni3Fe / TiO2 composite material of the present invention has the following advantages over the prior art:
[0035] 1. The preparation method of the flower cluster-like Ni3Fe / TiO2 composite material provided by the present invention is applicable to various catalysts prepared based on non-noble metals, including but not limited to Ni, Co, Fe, and Cu; moreover, it also has an obvious improvement effect on the dehydrogenation performance of MgH2;
[0036] 2. The flower cluster-like TiO2 prepared by the present invention itself has a catalytic effect on MgH2;
[0037] 3. The flower cluster-like TiO2 prepared by the present invention has a hollow structure, which can increase the loading amount of Ni3Fe nanoparticles;
[0038] 4. During the ball milling process, the flower cluster-like TiO2 prepared by the present invention can not only act as a grinding aid through its flower cluster-like structure, but also has the characteristic of being easily broken, and can be evenly dispersed in MgH2 together with the loaded Ni3Fe during the ball milling process;
[0039] Through the combined effects of the above 2, 3, and 4, the hydrogen desorption performance of MgH2 is effectively improved, that is, the initial hydrogen desorption temperature is reduced and the hydrogen desorption amount is increased;
[0040] 5. The simultaneous addition of flower cluster-like TiO2 and Ni3Fe can produce a synergistic effect;
[0041] 6. The raw materials used in the present invention are all chemical raw materials that have been industrially produced, are commercially available, and the synthesis process is simple, with low energy consumption and low pollution during the reaction process.
[0042] Therefore, compared with the prior art, the present invention has better hydrogen storage catalytic performance of MgH2, improves the stability and catalytic activity of the catalyst, and has broad application prospects in the fields of hydrogen storage materials, fuel cells, etc. BRIEF DESCRIPTION OF THE DRAWINGS
[0043] Figure 1 XRD pattern of the TiO2 / SiO2 precursor prepared in step 1 of Example 1
[0044] Figure 2 SEM image of the TiO2 / SiO2 precursor prepared in step 1 of Example 1;
[0045] Figure 3 XRD pattern of the TiO2 / SiO2 precursor prepared in step 1 of Example 1
[0046] Figure 4 SEM image of the flower cluster-like TiO2 prepared in step 2 of Example 1;
[0047] Figure 5 XRD pattern of Ni3Fe / TiO2 prepared in step 3 of Example 1.
[0048] Figure 6 、 7 SEM and energy spectrum images of Ni3Fe / TiO2 prepared in step 3 of Example 1;
[0049] Figure 8 TG curve of the MgH2-5wt% Ni3Fe / TiO2 composite material prepared in step 3 of Example 1;
[0050] Figure 9 TG curves of the MgH2-5wt% Ni3Fe / TiO2, MgH2-5wt% Ni3Fe, MgH2-5wt% TiO2, and as-milled MgH2 composite materials prepared in step 3 of Example 1;
[0051] Figure 10 Dehydrogenation curves of the MgH2-5wt% Ni3Fe / TiO2 composite material prepared in step 3 of Example 1 at different temperatures;
[0052] Figure 11 Hydrogen absorption curves of the MgH2-5wt% Ni3Fe / TiO2 composite material prepared in step 3 of Example 1 at different temperatures;
[0053] Figure 12 Dehydrogenation cycle life curve of the MgH2-5wt% Ni3Fe / TiO2 composite material prepared in step 3 of Example 1. Detailed implementation mode
[0054] The present invention further elaborates on the content of the present invention through examples in combination with the accompanying drawings of the specification, but it is not a limitation of the present invention.
[0055] Example 1
[0056] A preparation method of a flower cluster-like Ni3Fe / TiO2 composite material, comprising the following steps:
[0057] Step 1, preparation of the TiO2 / SiO2 precursor. First, 1.5 mL of oleylamine and 200 mL of absolute ethanol are mixed and stirred for 30 min to obtain a mixture. Then, 5.0 mL of tetrabutyl titanate, 10.0 mL of tetraethyl orthosilicate, and 1 mL of H2O are sequentially and slowly dropped into the mixture and left to stand for 12 h. After that, the precipitate obtained by standing is centrifuged, washed, and dried, and then calcined under air conditions at a calcination temperature of 450 °C and a holding time of 2 h to obtain the TiO2 / SiO2 precursor;
[0058] Unless otherwise specified, the centrifugation and washing conditions of the present invention are carried out under the conditions of a centrifugation speed of 9000 revolutions per minute, a centrifugation time of 5 min, and a centrifugation number of 6 times;
[0059] Unless otherwise specified, the drying conditions of the present invention are carried out under the conditions of a drying temperature of 65 °C and a drying time of 10 h;
[0060] In order to prove the successful preparation of the TiO2 / SiO2 precursor in step 1, XRD testing was carried out. The test results are as follows Figure 1 shown. The diffraction peaks of the TiO2 / SiO2 precursor are in good agreement with the standard peak crystal planes of TiO2 and SiO2. The test results show that the TiO2 / SiO2 was successfully synthesized, and it has high purity and high crystallinity.
[0061] In order to prove the microstructure of the TiO2 / SiO2 precursor obtained in step 1, SEM testing was carried out. The test results are as follows Figure 2 shown. It is known from the SEM test that the microstructure of the TiO2 / SiO2 precursor is a hollow spherical structure with a diameter of 50-70 nm.
[0062] Step 2: Preparation of flower cluster-like TiO₂. First, 0.25 g of the TiO₂ / SiO₂ precursor obtained in Step 1 was placed in 30 ml of a KOH solution with a concentration of 2 mol / L. The first hydrothermal reaction was carried out at a hydrothermal temperature of 100 °C for 24 h, and the resulting precipitate was centrifuged, washed, and dried. Then, it was soaked under the conditions of an HCl solution concentration of 0.12 mol / L and a soaking time of 2 h, and the soaked precipitate was centrifuged, washed, and dried. Finally, the first calcination was carried out at a calcination temperature of 300 °C for 2 h to obtain flower cluster-like TiO₂;
[0063] To prove the successful preparation of flower cluster-like TiO₂ in Step 2, XRD testing was carried out. The test results are as Figure 3 shown. For the flower cluster-like TiO₂, only the diffraction peaks of TiO₂ are present, while the diffraction peaks of SiO₂ disappear. The test results indicate that through the KOH hydrothermal reaction and hydrochloric acid soaking in Step 2, SiO₂ was successfully etched to form a flower cluster-like structure.
[0064] To prove the microstructure of the TiO₂ obtained in Step 2, SEM testing was carried out. The test results are as Figure 4 shown. The microstructure of the flower cluster-like TiO₂ is in the form of flower clusters with a size of 200 - 500 nm. The test results indicate that SiO₂, as a template agent, successfully achieved the regulation of the morphology of the material.
[0065] Step 3: Preparation of flower cluster-like Ni₃Fe / TiO₂ composite. 0.872 g of nickel nitrate hexahydrate, 0.403 g of iron nitrate nonahydrate, 0.48 g of urea, and 0.037 g of ammonium fluoride were added to 50 ml of methanol and stirred to dissolve to obtain Solution A. At the same time, 0.01 g of the flower cluster-like TiO₂ obtained in Step 2 was added to 10 mL of deionized water and ultrasonicated for 5 min to obtain Solution B. Then, Solution B was slowly added dropwise to Solution A, and the second hydrothermal reaction was carried out at a hydrothermal temperature of 140 °C for 8 h. After the resulting product was centrifuged, washed, and dried, the second calcination was carried out under a hydrogen-argon mixed gas condition at a calcination temperature of 500 °C for 2 h to obtain the flower cluster-like Ni₃Fe / TiO₂ composite, named Ni₃Fe / TiO₂.
[0066] To prove the successful preparation of Ni₃Fe / TiO₂ in Step 3, XRD testing was carried out. The test results are as Figure 5 shown. The diffraction peaks of Ni₃Fe / TiO₂ are in good agreement with the standard peak crystal planes of Ni₃Fe and TiO₂. The test results indicate that Ni₃Fe / TiO₂ was successfully synthesized, and it has high purity and high crystallinity.
[0067] To prove the microstructure of Ni₃Fe / TiO₂ obtained in step 3, SEM test and EDS test were carried out. The test results are as Figure 6 and Figure 7 shown. Granular Ni₃Fe is uniformly distributed on the surface of flower cluster-like TiO₂. The test results also show that Ni₃Fe is successfully loaded on TiO₂.
[0068] A preparation method of a MgH₂-based hydrogen storage material based on Ni₃Fe / TiO₂, that is, the application of flower cluster-like Ni₃Fe / TiO₂ as a catalyst for the MgH₂ hydrogen storage material. The specific preparation method is as follows. Under argon atmosphere, with the addition amount of Ni₃Fe / TiO₂ being 5 wt%, after mixing Ni₃Fe / TiO₂ and MgH₂, planetary ball milling is carried out under the conditions of a ball-to-material ratio of 30:1, a ball milling speed of 400 rpm, and a total ball milling time of 10 h. Among them, the specific method of planetary ball milling is that the single ball milling time is 12 min and the ball milling interval is 6 min, then a MgH₂-based hydrogen storage material with 5 wt% Ni₃Fe / TiO₂ addition is obtained, named MgH₂-5wt%Ni₃Fe / TiO₂.
[0069] To prove the hydrogen storage performance of MgH₂-5wt%Ni₃Fe / TiO₂, TG test and PCT test were carried out.
[0070] To prove the initial dehydrogenation temperature and dehydrogenation amount of MgH₂-5wt%Ni₃Fe / TiO₂, TG test was carried out. The test results are as Figure 8 shown. The initial dehydrogenation temperature of MgH₂-5wt%Ni₃Fe / TiO₂ is 163 °C, and the dehydrogenation amount is 6.02 wt%. The test results show that by adding Ni₃Fe / TiO₂, the initial dehydrogenation temperature of MgH₂ is reduced from 295.2 °C to 163 °C.
[0071] To prove the kinetic performance of MgH₂-5wt%Ni₃Fe / TiO₂, PCT test was carried out at different temperatures.
[0072] The test results of the dehydrogenation performance of MgH₂-5wt%Ni₃Fe / TiO₂ are as Figure 10 shown. When the dehydrogenation temperature is 270 °C, the hydrogen release amount in 30 min is 5.1 wt%; when the dehydrogenation temperature is 300 °C, the hydrogen release amount in 30 min is 7 wt%.
[0073] The test results of the hydrogen absorption performance of MgH₂-5wt%Ni₃Fe / TiO₂ are as Figure 11 shown. When the hydrogen absorption temperature is 100 °C, the hydrogen absorption amount in 30 min is 3.88 wt% of hydrogen.
[0074] The PCT test results show that MgH2-5wt% Ni3Fe / TiO2 has low-temperature hydrogen storage performance.
[0075] To prove the stability of MgH2-5wt% Ni3Fe / TiO2, a cyclic performance test was carried out. The specific test method was as follows: at 300 °C, the cyclic performance test was carried out with a hydrogenation hydrogen pressure of 2 Mpa. The test results are as Figure 12 shown. After 15 cycles, the actual hydrogen capacity of MgH2-5wt% Ni3Fe / TiO2 remained at 6.74 wt%. Compared with the capacity of the first cycle, the capacity retention rate was 96.3%. The test results show that MgH2-5wt% Ni3Fe / TiO2 exhibits stable dehydrogenation, that is, it has good cyclic stability.
[0076] Through the above TG test and PCT test results, it can be proved that Ni3Fe / TiO2 as a catalyst can significantly reduce the initial dehydrogenation temperature of MgH2 and effectively catalyze the hydrogen absorption and dehydrogenation reactions of MgH2, thereby improving the hydrogen absorption and dehydrogenation capacity.
[0077] To prove the influence of Ni3Fe / TiO2 on the hydrogen storage performance of MgH2, Comparative Example 1 was provided, in which only ball milling was carried out, and MgH2 without adding a catalyst was used as a reference ratio. At the same time, to further prove the respective roles of Ni3Fe and TiO2 in the technical solution, Comparative Example 2 and Comparative Example 3 were provided, which were MgH2-based hydrogen storage materials using Ni3Fe and TiO2 as catalysts respectively.
[0078] Comparative Example 1
[0079] A preparation method of a MgH2 hydrogen storage material, the steps not specifically described are the same as those in Example 1, except that: during the ball milling process, Ni3Fe / TiO2 is not added as a catalyst, that is, only 0.5 g of MgH2 is weighed and ball milled, and the obtained MgH2 hydrogen storage material is simply called as-milled MgH2.
[0080] The TG test results of as-milled MgH2 are as Figure 9 shown. The initial dehydrogenation temperature of as-milled MgH2 is 260 °C. Compared with the initial dehydrogenation temperature of the original MgH2 without ball milling, it decreased from 295.2 °C to 260 °C, with a decrease of 35.2 °C.
[0081] Comparative Example 2
[0082] A preparation method of a TiO₂-based MgH₂-based hydrogen storage material. The steps not specifically described are the same as those in Example 1, except that: during the ball milling process, the flower cluster-like TiO₂ obtained in Step 2 is used instead of the Ni₃Fe / TiO₂ obtained in Step 3, thus obtaining a TiO₂-based MgH₂-based hydrogen storage material, simply referred to as MgH₂-5wt%TiO₂.
[0083] The TG test results of MgH₂-5wt%TiO₂ are as Figure 9 shown. The initial dehydrogenation temperature of MgH₂-5wt%TiO₂ is 240 °C. Compared with Comparative Example 1, after excluding the ball milling factor, adding flower cluster-like TiO₂ can reduce the initial hydrogen release temperature from 260 °C to 240 °C, with a decrease of 20 °C. The reason is that flower cluster-like TiO₂ has easy breakability and can act as a grinding aid during the ball milling process, reducing the initial hydrogen release temperature of MgH₂.
[0084] Comparative Example 3
[0085] A preparation method of a Ni₃Fe-based MgH₂-based hydrogen storage material. The steps not specifically described are the same as those in Example 1, except that: during the ball milling process, the Ni₃Fe obtained in Step 2 is used instead of the Ni₃Fe / TiO₂ obtained in Step 3, thus obtaining a Ni₃Fe-based MgH₂-based hydrogen storage material, simply referred to as MgH₂-5wt%Ni₃Fe.
[0086] The TG test results of MgH₂-5wt%Ni₃Fe are as Figure 9 shown. The initial dehydrogenation temperature of MgH₂-5wt%Ni₃Fe is 175 °C. Compared with Comparative Example 1, after excluding the ball milling factor, adding Ni₃Fe can reduce the initial hydrogen release temperature from 260 °C to 175 °C, with a decrease of 85 °C. The reason is that Ni₃Fe can effectively reduce the initial hydrogen release temperature of MgH₂ as a catalyst.
[0087] Further comparative analysis of the above experimental results can lead to the following conclusions:
[0088] 1. By comparing Example 1 and Comparative Example 2, it can be seen that after excluding the ball milling factor, loading Ni₃Fe can reduce the initial hydrogen release temperature from 240 °C to 163 °C, with a decrease of 77 °C, which can also prove the conclusion obtained in the aforementioned Comparative Example 3 that adding Ni₃Fe can reduce the initial hydrogen release temperature;
[0089] 2. By comparing Example 1 and Comparative Example 3, it can be seen that after excluding the ball milling factor, adding flower cluster-like TiO₂ as a carrier can reduce the initial hydrogen release temperature from 175 °C to 163 °C, with a decrease of 12 °C, which can also prove the conclusion obtained in the aforementioned Comparative Example 2 that adding flower cluster-like TiO₂ can reduce the initial hydrogen release temperature;
[0090] 3. By comparing Example 1 and Comparative Example 1, it can be seen that after excluding the ball milling factor, adding Ni3Fe / TiO2 can reduce the initial hydrogen release temperature from 260 °C to 163 °C, a decrease of 97 °C. Comparing with the sum of the temperature decreases in Comparative Example 2 and Comparative Example 3, which is 20 + 85 = 105 °C, it can be seen that the total technical effects of separately adding 5 wt% Ni3Fe and 5 wt% flower cluster-like TiO2 are the same as those obtained by only adding 5 wt% Ni3Fe / TiO2 in Example 1. From the above analysis, it can be seen that simultaneously adding flower cluster-like TiO2 and Ni3Fe can produce a synergistic effect.
Claims
1. A preparation method of a flower cluster-like Ni3Fe / TiO2 composite material, characterized in that It includes the following steps: Step 1, preparation of TiO2 / SiO2 precursor. First, oleylamine and absolute ethanol are mixed and stirred to obtain a mixture. Then, tetrabutyl titanate, tetraethyl orthosilicate and H2O are slowly dropped into the mixture in sequence and left to stand. After that, the precipitate obtained by standing is centrifuged, washed and dried, and then calcined under certain conditions to obtain the TiO2 / SiO2 precursor; In the said Step 1, the volume ratio of oleylamine, absolute ethanol, tetrabutyl titanate, tetraethyl orthosilicate and H2O is 1.5:200:5:10:1; In the said Step 1, the stirring time is 30 - 60 min, and the standing time is 10 - 12 h; the calcination conditions are: under air condition, the calcination temperature is 450 - 500 °C, and the heat preservation time is 2 - 3 h; Step 2, preparation of flower cluster-like TiO2. First, the TiO2 / SiO2 precursor obtained in Step 1 is placed in a KOH solution and subjected to a first hydrothermal reaction under certain conditions, and the obtained precipitate is centrifuged, washed and dried. Then, it is soaked in an HCl solution under certain conditions, and the soaked precipitate is centrifuged, washed and dried. Finally, it is subjected to a first calcination under certain conditions to obtain flower cluster-like TiO2; In the said Step 2, the mass ratio of TiO2 / SiO2 precursor to KOH is 1:20, the concentration of the KOH solution is 2 mol / l; the concentration of the HCl solution is 0.12 mol / L, and the soaking time is 2 - 3 h; In the said Step 2, the conditions of the first hydrothermal reaction are: the hydrothermal temperature is 100 - 120 °C, and the hydrothermal time is 20 - 24 h; In the said Step 2, the conditions of the first calcination are: under air atmosphere, the calcination temperature is 300 - 350 °C, and the calcination time is 2 - 3 h; Step 3, preparation of flower cluster-like Ni3Fe / TiO2 composite. Nickel nitrate hexahydrate, iron nitrate nonahydrate, urea and ammonium fluoride with a certain mass ratio are added to methanol and stirred to dissolve to obtain solution A. At the same time, the flower cluster-like TiO2 obtained in Step 2 is added to ionized water according to a certain ratio and ultrasonically treated to obtain solution B. Then, solution B is slowly dropped into solution A, and a second hydrothermal reaction is carried out under certain conditions. The obtained product is centrifuged, washed and dried, and then subjected to a second calcination under certain conditions to obtain flower cluster-like Ni3Fe / TiO2 composite, named Ni3Fe / TiO2; In the said Step 3, the mass ratio of nickel nitrate hexahydrate, iron nitrate nonahydrate, urea, ammonium fluoride and flower cluster-like TiO2 is 2:1:1.2:0.1:0.25; In the said Step 3, the conditions of the second hydrothermal reaction are: the hydrothermal temperature is 100 - 140 °C, and the hydrothermal time is 8 - 10 h; In the said Step 3, the conditions of the second calcination are: under a hydrogen-argon mixed atmosphere condition, the calcination temperature is 450 - 500 °C, and the calcination time is 2 - 3 h.
2. The preparation method according to claim 1, wherein: The obtained flower cluster-like Ni3Fe / TiO2 composite material is composed of flower cluster-like TiO2 and Ni3Fe particles prepared on its surface. The flower cluster-like TiO2 is prepared by first preparing TiO2 / SiO2 and then forming hollow flower cluster-like TiO2. The microstructure of the TiO2 / SiO2 is a hollow spherical shape with a size of 50 - 70 nm. The microstructure of the flower cluster-like TiO2 is a hollow flower cluster-like structure with a size of 200 - 500 nm. The Ni3Fe particles are loaded on the surface of the flower cluster-like TiO2.
3. The preparation method according to claim 1, characterized in that: For the obtained flower cluster-like Ni3Fe / TiO2 composite material, under argon gas conditions throughout, after mixing Ni3Fe / TiO2 with MgH2 and performing forward and reverse ball milling under certain conditions, the MgH2-based hydrogen storage material based on Ni3Fe / TiO2 is obtained, named MgH2-Ni3Fe / TiO2. The addition amount of Ni3Fe / TiO2 is 5 wt%. The conditions for the forward and reverse ball milling are as follows: the ball-to-material ratio is 30:1, the ball milling speed is 400 rpm, the total ball milling time is 10 h, the single ball milling time is 12 min, and the ball milling interval is 6 min.
4. The preparation method according to claim 3, characterized in that: For the application of the obtained MgH2-based hydrogen storage material based on Ni3Fe / TiO2 as a hydrogen storage material, the doping amount of Ni3Fe / TiO2 is 5 wt%, the initial dehydrogenation temperature is 155 - 175 °C; the dehydrogenation amount at 300 °C is 6.9 - 7.1 wt%; the hydrogen absorption amount at 100 °C is 4.2 - 4.8 wt%.
5. The preparation method according to claim 3, characterized in that: For the application of the obtained MgH2-based hydrogen storage material based on Ni3Fe / TiO2 as a hydrogen storage material, the retention rate after 15 cycles is 96 - 98%.