Hydrangea-like NiO@NiMoO4 composite and its preparation and application

Abstract

This invention discloses a hydrangea-like NiO@NiMoO4 composite material and its preparation and application, which belongs to the technical field of hydrogen storage materials. This application utilizes a comprehensive combination of hydrothermal, calcination, and ball milling techniques to produce the composite material. The resulting material exhibits a microscopic hydrangea-like spherical morphology with particle diameters of 2-3 μm. When this material was blended with MgH2 to form an MgH2+10 wt% NiO@NiMoO4 composite hydrogen storage material, it began to release hydrogen at 190°C and rapidly released 6.44 wt% H2 within 4.5 min at 300°C, achieving 99.4% of the theoretical hydrogen release amount. This demonstrates that this composite hydrogen storage material has good low-temperature hydrogen storage / desorption mechanical properties, a high hydrogen storage / desorption capacity, and good cycling stability. Overall, this material has great prospects for application in hydrogen storage and may provide a new concept for the research and development of hydrogen storage materials.

Description

[Technical Field]

[0001] The present invention belongs to the technical field of hydrogen storage materials, and particularly relates to hydrangea-like NiO@NiMoO4 composite materials and their preparation methods and applications in hydrogen storage materials. [Background technology]

[0002] In an era of advocating green, low-carbon, and environmental protection, hydrogen energy, as a green and environmentally friendly energy, is sure to become one of the mainstream energy sources of the future. With the rapid development of the new energy automobile industry in recent years, the demand for hydrogen energy in the energy market will also increase rapidly. Therefore, the development and application of hydrogen storage materials will be of great significance to environmental protection and energy development in the long term.

[0003] Hydrogen is a secondary energy source that can be stored in solid materials through physical or chemical absorption. Compared with traditional high-pressure gas and cryogenic liquid storage methods, gaseous solid hydrogen storage has the advantages of high density and safe storage. However, solid hydrogen storage materials pose several major challenges in their large-scale application: 1. How to improve the hydrogen storage capacity of the material; and 2. How to reduce material costs and the use of precious metals. Currently, commonly used hydrogen storage materials mainly include metallic and non-metallic hydrogen storage materials, among which magnesium-based hydrogen storage materials are one with great potential. Among the many magnesium-based hydrogen storage materials, MgH2 is considered one of the ideal solid hydrogen storage materials due to its high hydrogen storage capacity (7.6 wt%) and reversible hydrogen absorption and desorption performance, and it has broad potential in energy conversion, fuel cells, and heat storage applications. However, magnesium-based materials have obvious defects in practical use, mainly due to their poor hydrogen release mechanical properties, requiring high temperatures of around 350°C to efficiently absorb and release hydrogen, and the thermodynamic properties of MgH2 are too stable, which also leads to the problem that the hydrogen release temperature of MgH2 is too high. All of these factors hinder the large-scale application of such materials in the field of hydrogen storage.

[0004] Due to the problems inherent in MgH2, it is necessary to explore ways to effectively improve the performance of magnesium-based hydrogen storage materials. Currently, there are three main approaches. First, modify the MgH2 microstructure. Second, improve hydrogen storage performance by adding transition metals, metal oxides, or metal salts as catalysts. Third, modify the surface of the material. Among these, doping catalysts is considered the simplest and most effective strategy for improving the mechanical properties of MgH2, which can solve the problems of MgH2's high hydrogen release temperature and slow and poor hydrogen absorption kinetics. However, there has been no significant progress in reducing the thermodynamic stability of MgH2 for a long time, which is the essential cause of its high hydrogen release temperature.

[0005] Tianping Huang et al. (Tianping Huang, Xu Huang, Chuanzhu Hu. et. Enhancing hydrogen storage properties of MgH2 through the addition of Ni / CoMoO4 nanorods, Journal Pre-proof, S2468-6069 (20) 30232-X) proposed a method to improve the hydrogen storage performance of MgH2 by using Ni / CoMoO4 nanorods. Specifically, they introduced one-dimensional NiMoO4 and CoMoO4 nanorods into MgH2. The addition of NiMoO4 and CoMoO4 lowered the onset and peak release temperatures of MgH2, particularly NiMoO2. The peak temperature of MgH2-10wt%NiMoO4 was only 257.3°C. By doping with NiMoO4, the hydrogen release activation energy of MgH2 was reduced by approximately 40.8%, and the MgH2-NiMoO4 system exhibited enhanced isothermal hydrogen release and resorption behavior, releasing 6 wt.% hydrogen within 10 minutes at 300°C and absorbing 5.5 wt.% hydrogen within 10 minutes at 150°C and an initial pressure of 3.2 MPa. The MgH2-NiMoO4 system exhibited lower hydrogen release temperatures and faster kinetics than pure MgH2, a clear breakthrough over previous research.

[0006] However, the applicant believes that although the above solution can significantly lower the hydrogen desorption temperature of MgH2, the actual hydrogen desorption temperature is still high, which may be related to the one-dimensional rod-like structure of the doping catalyst NiMoO4 used. The catalyst shape first affects the catalyst's densely packed structure, and then affects the support surface required for the raw material reaction. The one-dimensional rod-like morphology of the material provides limited reactive active sites, and the changes in electronic structure and charge transfer characteristics during the reaction promotion process are somewhat insufficient, so it may not provide sufficient H "diffusion channels" for the subsequent hydrogen absorption / desorption process. In order to further lower the hydrogen desorption temperature and improve the hydrogen desorption mechanical properties of MgH2, new materials that can further lower the hydrogen desorption temperature of MgH2 are needed, and further exploration of the catalyst composition and morphology is necessary to provide new concepts and guidance for the research and development of hydrogen storage material catalysts. Summary of the Invention [Problem to be solved by the invention]

[0007] The purpose of the present invention is to propose a hydrangea-like NiO@NiMoO4 composite material and its preparation and application to solve the problems existing in the prior art. This material has a unique morphological advantage that provides more hydrogen "diffusion channels" and active "catalytic sites" for the subsequent hydrogen absorption / desorption process, thereby more effectively lowering the hydrogen desorption temperature than the prior art and solving the problem of slow desorption kinetics of conventional hydrogen storage materials. [Means for solving the problem]

[0008] The technical solution of the present invention is as follows: A hydrangea-like NiO@NiMoO4 composite material, which has a continuous layer structure with obvious micro-wrinkles, and exhibits a hydrangea-like spherical shape as a whole, with the diameter of the microspheres being 2-3 μm.

[0009] The method for producing the hydrangea-like NiO@NiMoO composite material is as follows: 1) Dissolve nickel salt and molybdate in deionized water and stir to form a mixed solution; 2) Add a certain amount of surface modifier and precipitant to the mixed solution and stir to form a homogeneous solution; 3) The homogeneous solution is placed in a reactor, sealed, and then placed in a vacuum drying box to carry out a hydrothermal reaction. 4) After the reaction is completed, cool the reactor, clean and dry the precipitate at room temperature, 5) The cleaned and dried precipitate is placed in a tube furnace and calcined. 6) The calcined product is taken out and crushed to obtain the final product NiO@NiMoO4.

[0010] Furthermore, in step 1), the molar ratio of nickel salt to molybdate is 2-3:1.

[0011] Furthermore, in step 2), the surface modifier used is at least one of NH4F, NH4NO3, and CHO2, and the precipitating agent used is at least one of CO(NH2)2, HC(NH2)2, and (C3H5NO)n.

[0012] Furthermore, in step 3), the hydrothermal reaction is carried out at a temperature of 130 to 135°C for a heat retention time of 12 to 13 hours.

[0013] Furthermore, in step 5), the firing temperature is 500 to 600° C., and the firing time is 3 to 4 hours.

[0014] The hydrangea-like NiO@NiMoO composite material can be applied to hydrogen storage. This composite material is mixed with MgH2 as a hydrogen storage material catalyst in a certain ratio, and then placed in a ball mill tank under an inert atmosphere for mixing and ball milling to obtain a composite hydrogen storage material.

[0015] Furthermore, the mass ratio of NiO@NiMoO4 to MgH2 in the compounded composite hydrogen storage material is 1:9, and this composite hydrogen storage material begins to release hydrogen at 190°C and can release 6.44 wt% H2 within 4.5 min at 300°C, reaching 99.4% of the theoretical hydrogen deposition amount.

[0016] Furthermore, the inert atmosphere is a high-purity argon atmosphere with a pressure of 7 to 7.5 MPa, the revolution speed of the ball mill device is 400 to 450 r / min, and the ball mill time is 2 to 3 hours.

[0017] Furthermore, the ball material ratio during ball milling is 40:1, and the ball milling tools used are tungsten carbide hard alloy steel balls. [Effects of the Invention]

[0018] The present invention has the following advantages over the prior art: 1. The NiO@NiMoO4 composite material prepared in this application has an overall spherical structure similar to that of a hydrangea, specifically a continuous layered structure with obvious wrinkles, and the diameter of the microspheres is approximately 2-3 μm. Compared with conventional one-dimensional catalytic materials, this structure of the composite material can provide more reactive active sites as a catalyst for hydrogen storage materials, further promoting the changes in electronic structure and charge transfer properties during the reaction process, and providing more hydrogen "diffusion channels" and active "catalytic sites" for the subsequent hydrogen absorption / release process.

[0019] 2. After the NiO@NiMoO catalyst prepared in this application is composited with MgH2, it is uniformly distributed on the surface of MgH2, which is beneficial to increase the catalytic sites, effectively improving the hydrogen storage performance of MgH2, accelerating the absorption and desorption of hydrogen gas on MgH2, and significantly lowering the hydrogen desorption temperature of MgH2, thereby achieving the purpose of fast hydrogen absorption and desorption.

[0020] 3. The NiO@NiMoO4 composite material prepared in this application and MgH2 were mixed in a mass ratio of 1:9 and ball-milled to form the MgH2+10wt%NiO@NiMoO4 composite hydrogen storage material. The material began to release hydrogen at 190°C during temperature-programmed hydrogen release experiments. Compared with the prior art, the MgH2 hydrogen release temperature was significantly lower, indicating that this composite hydrogen storage material has good low-temperature hydrogen absorption and desorption mechanical properties.

[0021] 4. The MgH2+10wt%NiO@NiMoO4 composite hydrogen storage material prepared in this application can rapidly release 6.44wt% H2 within 4.5min at 300℃, reaching 99.4% of the theoretical hydrogen deposition amount, demonstrating that this composite hydrogen storage material has a high hydrogen absorption / desorption capacity.

[0022] 5. The composite hydrogen storage material prepared in this application has good cycle stability. After 10 cycles, the hydrogen storage capacity reaches 5.84% and the efficiency can be maintained above 90%.

[0023] 6. The manufacturing method disclosed in this application is simple and easy to operate. NiO@NiMoO4 microparticles are manufactured using simple hydrothermal, calcination, and ball milling techniques. The raw materials used are common, readily available, and inexpensive. This composite material can also be applied to hydrogen energy fuel cells and hydrogen storage sources for portable power supplies. [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 1 is a SEM image of the NiO@NiMoO4 composite material prepared in Example 1. [Figure 2] The temperature-promoted hydrogen release curves of MgH2+10wt%NiO@NiMoO4 composite hydrogen storage material and MgH2. [Figure 3] XRD spectrum of MgH2+10wt%NiO@NiMoO4 composite hydrogen storage material. [Figure 4] XRD spectrum of MgH2+10wt%NiO@NiMoO4 composite hydrogen storage material after hydrogen release. [Figure 5] Figure 1 shows the constant temperature hydrogen release curves of MgH2+10wt%NiO@NiMoO4 composite hydrogen storage material and MgH2. [Figure 6] The temperature-promoted hydrogen absorption curves of the MgH2+10wt%NiO@NiMoO4 composite hydrogen storage material and MgH2. [Figure 7] XRD spectrum of MgH2+10wt%NiO@NiMoO4 composite hydrogen storage material after hydrogen absorption. [Figure 8] This is a graph showing the constant temperature hydrogen absorption / desorption cycle performance of the MgH2+10wt%NiO@NiMoO4 composite hydrogen storage material. DETAILED DESCRIPTION OF THE INVENTION

[0025] The technical solution of the present invention will be further described below in conjunction with the drawings, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention shall all be included in the protection scope of the present invention.

[0026] Example 1: Preparation of hydrangea-like NiO@NiMoO4 composite material 1. 4 mmol of NiCl2·6H2O and 2 mmol of (NH4)6Mo7O 24 Dissolve 4H2O in 70mL of deionized water and stir for 5min to form a mixed solution. 2. Add 6 mmol of NH4F and 10 mmol of CO(NH2)2 to the mixed solution and stir for 1 hour. 3. The homogeneous solution obtained by stirring is placed in a hydrothermal reactor, sealed, and kept in a vacuum drying box at 130°C for 12 hours. 4. After the reactor is cooled, the precipitate is cleaned and dried at room temperature. 5. The dried material is placed in a tube furnace and baked at 500°C for 3 hours in an air environment. 6. After calcination, the dried material was taken out and crushed multiple times in a crusher to obtain the final product, NiO@NiMoO4 composite material.

[0027] Figure 1 shows an SEM image of the NiO@NiMoO4 prepared in this example. This application assembled NiO into NiMoO4 using a conventional hydrothermal process. The NiO@NiMoO4 composite exhibited a spherical structure resembling a hydrangea, exhibiting a morphology distinct from that of typical magnesium-based hydrogen storage catalysts. Rather than a simple one-dimensional sheet or rod structure, it exhibited a continuous layered structure with distinct wrinkles. This unique morphology was primarily due to catalyst extrusion and aggregation under the influence of van der Waals forces during the hydrothermal reduction reaction under certain conditions. The microspheres, approximately 2-3 μm in diameter, formed a spherical structure composed of nanosheets and nanorods. This unique phenomenon was attributed to defects in the crystal structure. The defects provided more reactive sites, further accelerating changes in the electronic structure and charge transfer properties during the reaction, providing more hydrogen diffusion pathways and active catalytic sites for the subsequent hydrogen storage process.

[0028] Example 2: Preparation of MgH2+10wt%NiO@NiMoO4 composite hydrogen storage material In an Ar atmosphere with a pressure of approximately 7 MPa, 100 mg of the NiO@NiMoO4 microparticles prepared in Example 1 and 900 mg of MgH2 were mixed and placed in a ball mill tank. The mixture was ball-to-material ratio was 40:1 and the revolution speed of the ball mill was 400 r / min for 2 h. During the ball milling, the ball mill tank was alternately rotated forward and backward for 30 min each, with a 10-min pause between each rotation. After 1 h of ball milling, the sample mass in the tank was pulverized, and then alternately ball milled forward and backward for 30 min each. After the ball milling was completed, the sample was removed and stored in a glove box. This yielded a MgH2 + 10 wt% NiO@NiMoO4 composite hydrogen storage material.

[0029] Preferably, in this embodiment, tungsten carbide hard alloy steel balls are used as ball milling tools, which have excellent wear resistance and bending resistance and can be used for a long time under harsh conditions. Compared with ordinary stainless steel balls, the tungsten carbide hard alloy steel balls in the ball milling process do not drop worn carbides, which can improve the purity and uniformity of the composite hydrogen storage material.

[0030] Related Performance Tests Hydrogen absorption and desorption stability tests were carried out in a Sievert-type hydrogen storage performance tester, a gaseous hydrogen storage performance tester, with a technical performance index of 1-15 MPa H2 and 20-600°C.

[0031] 1. Study on the effect of doping catalyst NiO@NiMoO4 on the hydrogen release performance of MgH2: Hydrogen desorption tests were conducted on MgH2 and MgH2 + 10 wt% NiO@NiMoO4. A 100-150 mg sample of each was placed in a glove box, vacuumed, and tested for leaks before the test began. The temperature was raised to 450°C at a rate of 2°C / min. Figure 2 shows the temperature-dependent hydrogen desorption curves for MgH2 + 10 wt% NiO@NiMoO4 and MgH2 obtained after the test. As can be seen from the figure, the hydrogen desorption onset temperature of the MgH2 + 10 wt% NiO@NiMoO4 composite system was reduced to 190°C, approximately 170°C lower than that of pure MgH2. This significantly lowered the hydrogen desorption temperature of MgH2 and improved the hydrogen desorption mechanical properties, demonstrating a significant breakthrough over conventional magnesium-based hydrogen storage material catalysts.

[0032] Figure 3 shows the XRD spectrum of MgH2 + 10wt%NiO@NiMoO4. As can be seen from the figure, the main component of the composite is MgH2, and the diffraction peak of MgO appears near 2θ = 42°, which may be due to the oxidation of a small amount of Mg powder during the manufacturing process. Overall, the fact that no additional new phases appeared after doping the MgH2 material with the NiO@NiMoO4 catalyst indicated the high stability of NiO@NiMoO4 during ball milling.

[0033] Figure 4 shows the XRD phase spectrum of the MgH2+10wt%NiO@NiMoO4 composite hydrogen storage material after complete hydrogen release. This spectrum was measured using an X-ray diffractometer. As can be seen from the figure, after complete hydrogen release from the MgH2+10wt%NiO@NiMoO4 composite, the main diffraction peak changed from MgH2 to Mg, and the NiO@NiMoO4 phase disappeared. Instead, the diffraction peaks of Mg2, Ni, and Mo appeared, indicating that the catalyst had reacted with MgH2.

[0034] The constant-temperature hydrogen release performance of the composite hydrogen storage materials was measured using the "constant volume pressure method." The test results are shown in Figure 5. This composite system exhibited an ultrafast hydrogen release rate at a constant temperature of 300°C. MgH2 + 10 wt% NiO@NiMoO4 rapidly released 6.44 wt% H2 within 4.5 min, nearly reaching the theoretical hydrogen release amount (6.48 wt%). However, MgH2 only released 0.04 wt% H2, and even after 60 min of reaction, the amount of hydrogen gas released by MgH2 was less than 1 wt%.

[0035] 2. Study on the effect of doping catalyst NiO@NiMoO4 on the temperature-programmed hydrogen storage performance of MgH2 Temperature-programmed hydrogen storage performance test of MgH2+10wt%NiO@NiMoO4 composite hydrogen storage material: After evacuation and leak detection, a hydrogen absorption test was conducted using the composite material that had completely released hydrogen. The temperature rise process was controlled using a temperature control box so that the temperature rose to 400°C at a rate of 1°C / min.

[0036] Figure 6 shows the temperature-promoted hydrogen absorption curve of the MgH2+10wt%NiO@NiMoO4 composite. As can be seen, this composite began to absorb hydrogen slowly below 40°C, and by the time the temperature reached 150°C, it had absorbed 4.54wt% H2. However, at the same temperature, pure MgH2 had only just begun to absorb hydrogen, only absorbing less than 0.2wt% H2.

[0037] Figure 7 shows the XRD phase spectrum of the MgH2+10wt%NiO@NiMoO4 composite hydrogen storage material after complete hydrogen absorption. This spectrum was measured using an X-ray diffractometer. After the composite material had fully dehydrogenated, the main diffraction peak changed from Mg to MgH2. The Mo diffraction peak still existed, but the Mg2Ni diffraction peak disappeared and reappeared after hydrogen absorption. This indicates that Mg2Ni and Mg2NiH4 repeatedly switched between hydrogen absorption and desorption processes, improving the hydrogen storage capacity of MgH2 and acting as a substantial catalyst in conjunction with Mo alone.

[0038] 3. Study on the cycle stability of MgH2+10wt%NiO@NiMoO4 composite hydrogen storage material In the cycle test, the hydrogen release time was 15 minutes and the hydrogen absorption time was 5 minutes.

[0039] As shown in Figure 8, after the first cycle, the hydrogen release capacity of the composite material was 6.48 wt% and the hydrogen storage capacity was 6.3 wt%. The lack of hydrogen storage capacity may be due to the formation of MgO. After the second cycle, the hydrogen release capacity of the material began to decrease, and the hydrogen storage capacity also declined slightly. In subsequent cycles, the decrease trend became more gradual, and the hydrogen storage capacity tended to stabilize. Finally, after the 10th cycle, the hydrogen storage capacity of the composite material was 5.84 wt%, and the efficiency remained above 90%.

[0040] In summary, in the composite hydrogen storage material prepared in this example, NiO@NiMoO4 functions as a catalyst to improve the mechanical properties of MgH2 for hydrogen absorption and desorption. MgH2 primarily functions as a carrier for hydrogen absorption and desorption, and the NiO@NiMoO4 catalyst is uniformly distributed on the surface of MgH2. Under high-temperature conditions during hydrogen absorption and desorption, the synergistic effect of Mg2NiH4 generated in situ in the composite hydrogen storage material and Mo promotes H2 desorption and diffusion, thereby accelerating the hydrogen gas absorption and desorption performance of MgH2.

[0041] The above is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structure or equivalent flow conversion made by using the contents of the specification and drawings of the present invention, or anything directly or indirectly applied in other related technical fields, is included in the patent protection scope of the present invention for the same reason.

Claims

1. A composite hydrogen storage material comprising an MgH2 support and a NiO@NiMoO4 catalyst, The NiO@NiMoO catalyst is a hydrangea-like NiO@NiMoO composite material that has a continuous layered structure with clear microscopic wrinkles and exhibits a hydrangea-like spherical morphology as a whole. Composite hydrogen storage materials.

2. A method for producing a composite hydrogen storage material, comprising: mixing a hydrangea-like NiO@NiMoO composite material with MgH2 as a hydrogen storage material catalyst in a certain ratio; and then placing the mixture in a ball mill tank under an inert atmosphere for mixing and ball milling, The hydrangea-like NiO@NiMoO composite has a continuous layered structure with obvious microscopic wrinkles, and exhibits an overall hydrangea-like spherical morphology. Methods for manufacturing composite hydrogen storage materials.

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