CeVO4-MgH2 composite material, and preparation method and application thereof

Abstract

The application provides a CeVO4-MgH2 composite material and a preparation method and application thereof. The CeVO4-MgH2 composite material comprises a core and a coating layer, the core comprises MgH2, and the coating layer comprises CeVO4. The preparation method comprises the following steps: ball milling CeVO4 powder and MgH2 powder to obtain the CeVO4-MgH2 composite material. The CeVO4 powder is used as a catalyst to perform synergistic catalytic modification on a MgH2 hydrogen storage material system, the hydrogen absorption and release performance of the MgH2 hydrogen storage material is significantly improved, and the CeVO4-MgH2 composite hydrogen storage material with fast hydrogen absorption and release kinetics is obtained.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen storage materials, and relates to a CeVO4-MgH2 composite material, its preparation method and application. Background Technology

[0002] Energy is the core driving force for the development of industrial civilization and the realization of sustainable human development. With the excessive consumption of traditional fossil fuels, human society is facing a huge energy crisis. Developing clean and efficient renewable energy sources and establishing related energy production and supply systems is urgently needed. Hydrogen energy, due to its abundant sources, green and low-carbon characteristics, and high calorific value, has become the most promising clean energy source for the 21st century.

[0003] Currently, achieving safe, efficient, and high-density reversible hydrogen storage is one of the key technologies restricting the large-scale application of hydrogen energy. Current research and development focuses on three hydrogen storage methods: high-pressure gaseous hydrogen storage, liquid hydrogen storage, and solid-state hydrogen storage. While high-pressure gaseous hydrogen storage is technically mature at present, its storage cylinders operate at high pressures (70 MPa), posing significant safety risks. Cryogenic liquid hydrogen storage suffers from high liquefaction energy consumption and requires stringent insulation protection, resulting in high costs. Solid-state hydrogen storage, with its high volumetric hydrogen storage density, good safety, and ease of equipment and infrastructure construction, is becoming one of the important hydrogen storage methods for future large-scale hydrogen energy applications. Among the currently developed solid-state hydrogen storage materials, the Mg / MgH2 system boasts a high mass hydrogen storage density of 7.6 wt%, while other AB, AB2, AB5, and vanadium-based BCC solid solution hydrogen storage alloys, due to the limitations of their inherent theoretical mass hydrogen storage density, make the Mg / MgH2 system the most promising candidate to reach the light-duty vehicle hydrogen storage target (5.50 wt%) proposed by the U.S. Department of Energy (DOE). Furthermore, Mg possesses significant advantages such as abundant resources, light weight, simple preparation, and low cost, making it promising for broad applications. However, the poor thermodynamic properties of MgH2, with a dehydrogenation temperature as high as 300℃ and slow hydrogen absorption and desorption kinetics, severely restrict its practical application and hinder the further development of magnesium-based hydrogen storage materials.

[0004] Traditional AB5 hydrogen storage alloys have a capacity of only 1.4 wt%, AB2 hydrogen storage alloys have a capacity of only 2.0 wt%, V-based solid solution hydrogen storage alloys with BCC structure have a hydrogen storage capacity of 3.8 wt% (but residual hydrogen is as high as 1.4 wt%), while light metal hydrides MgH2 have a capacity as high as 7.6 wt%, but their hydrogen absorption and desorption kinetics are slow and their dehydrogenation temperature is high.

[0005] CN116143069A discloses a magnesium-based hydrogen storage material using oxygen-vacancy-enriched vanadium pentoxide as a catalyst and its preparation method. A MgH2-Ywt%H-V2O5 composite hydrogen storage material was prepared by ball milling commercially available MgH2 and oxygen-vacancy-enriched H-V2O5 nanosheets in a certain proportion; however, its hydrogen absorption performance needs further improvement.

[0006] CN115367701A discloses a MgH2-AlH3-TiF3 composite hydrogen storage material and its preparation method. S1: MgH2 and TiF3 are ball-milled under an inert gas atmosphere to obtain the MgH2-TiF3 composite hydrogen storage material; S2: AlH3 is added to the MgH2-TiF3 composite hydrogen storage material prepared in S1 and ball-milled to obtain the MgH2-AlH3-TiF3 composite hydrogen storage material. However, this method requires a large amount of raw materials and has high preparation costs.

[0007] Therefore, how to prepare a high-capacity hydrogen storage material is an important research direction in this field. Summary of the Invention

[0008] The purpose of this invention is to provide a CeVO4-MgH2 composite material with excellent hydrogen absorption and desorption properties, its preparation method, and its application.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] One objective of this invention is to provide a CeVO4-MgH2 composite material, which includes a core and a coating layer, wherein the core includes MgH2 and the coating layer includes CeVO4.

[0011] This invention utilizes CeVO4 powder as a catalyst to synergistically modify the MgH2 hydrogen storage material system, significantly improving the hydrogen absorption and desorption performance of the MgH2 hydrogen storage material, and obtaining a composite hydrogen storage material with rapid hydrogen absorption and desorption kinetics.

[0012] In this invention, a coating layer is prepared in the composite material. The coating layer includes CeVO4, where V element facilitates the dehydrogenation of MgH2, and the rare earth element Ce forms CeH during the hydrogen absorption and desorption process of MgH2. x It acts as a "hydrogen pump," providing a diffusion channel for H atoms. Therefore, based on the catalytic effect of Ce and V, CeVO4 is used as a catalyst to coat the MgH2 system. By coating the surface of MgH2 powder with transition metals Ce and V, the hydrogen absorption and desorption kinetics of the composite material are improved, and the operating temperature of MgH2 is also significantly reduced.

[0013] As a preferred technical solution of the present invention, the total mass of the CeVO4-MgH2 composite material is 100%, and the mass fraction of CeVO4 is 1-20%. The mass fraction of CeVO4 can be 1%, 2%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, or 20%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable. Preferably, it is 3-12%, and more preferably 7-10%.

[0014] In this invention, if the mass fraction of CeVO4 is too high, the hydrogen storage capacity of the composite material will decrease significantly. If the mass fraction of CeVO4 is too low, the hydrogen storage capacity of the material will not change significantly and will show a slight decreasing trend.

[0015] As a preferred technical solution of the present invention, the raw materials of the CeVO4-MgH2 composite material include CeVO4 powder and MgH2 powder.

[0016] Preferably, the CeVO4 powder is spherical nanoparticles with a diameter of 50-100 nm. The diameter can be 50 nm, 85 nm, 60 nm, 65 nm, 80 nm, 85 nm, 90 nm, 95 nm or 100 nm, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0017] Preferably, the MgH2 powder is spherical particles with a diameter of 0.5 to 5 μm. The diameter can be 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, or 5 μm, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0018] Preferably, the diameter of the CeVO4-MgH2 composite material is 200-300 nm, wherein the diameter can be 200 nm, 210 nm, 220 nm, 230 nm, 240 nm, 250 nm, 260 nm, 270 nm, 280 nm, 290 nm or 300 nm, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0019] In this invention, if the diameter of the CeVO4-MgH2 composite material is too large, the hydrogen absorption and desorption performance of the material will decrease. If the diameter of the CeVO4-MgH2 composite material is too small, the surface activity of the material will increase, but after repeated hydrogen absorption and desorption tests, agglomeration is likely to occur, leading to the performance degradation of the composite material.

[0020] A second objective of this invention is to provide a method for preparing the CeVO4-MgH2 composite material as described in one objective, the method comprising:

[0021] The CeVO4-MgH2 composite material was obtained by ball milling CeVO4 powder and MgH2 powder.

[0022] This invention induces a reaction in CeVO4 powder through ball milling, which facilitates the formation of active sites on the MgH2 surface and effectively accelerates the hydrogen absorption and desorption reaction process. The CeVO4-MgH2 composite material is prepared by mechanical ball milling, which is simple, has controllable process conditions, and low preparation cost. The catalytic phase generated by MgH2 and CeVO4 during the hydrogen absorption and desorption process greatly improves the dehydrogenation temperature and hydrogen absorption and desorption rate of the composite material system.

[0023] As a preferred technical solution of the present invention, the average particle size of the ball-milled CeVO4-MgH2 composite material is 200-300 nm. The average particle size can be 200 nm, 210 nm, 220 nm, 230 nm, 240 nm, 250 nm, 260 nm, 270 nm, 280 nm, 290 nm or 300 nm, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0024] Preferably, the ball-to-material ratio of the ball mill is 100 to 140:1, wherein the ball-to-material ratio can be 100:1, 105:1, 110:1, 115:1, 120:1, 125:1, 130:1, 135:1 or 140:1, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0025] Preferably, the ball milling speed is 450-550 rpm, wherein the speed can be 450 rpm, 460 rpm, 470 rpm, 480 rpm, 490 rpm, 500 rpm, 510 rpm, 520 rpm, 530 rpm, 540 rpm or 550 rpm, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0026] Preferably, the ball milling time is 20 to 28 hours, wherein the time can be 20 hours, 21 hours, 22 hours, 23 hours, 24 hours, 25 hours, 26 hours, 27 hours or 28 hours, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0027] Preferably, the ball milling process involves a 10-15 minute interval followed by a 4-8 minute rest period. The ball milling time can be 10 minutes, 11 minutes, 12 minutes, 13 minutes, 14 minutes, or 15 minutes, and the rest period can be 4 minutes, 5 minutes, 6 minutes, 7 minutes, or 8 minutes, etc. However, it is not limited to the listed values; other unlisted values ​​within the above ranges are also applicable.

[0028] In this invention, the ball milling process generates a large amount of heat due to prolonged milling, which can easily cause the decomposition of MgH2. Furthermore, the ball mill is pressurized, necessitating pauses for heat dissipation. Excessive or insufficient milling time can cause the powder to agglomerate and stick, resulting in a decrease in hydrogen absorption and desorption performance.

[0029] Preferably, the atmosphere used in the ball mill is an inert atmosphere.

[0030] Preferably, the inert atmosphere comprises hydrogen.

[0031] As a preferred embodiment of the present invention, the method for preparing the CeVO4 powder includes the following steps:

[0032] (1) A first solution is obtained by mixing a cerium source and a template directing agent in a solvent, and a second solution is obtained by mixing a vanadium source in a solvent;

[0033] (2) After mixing the first solution and the second solution in step (1), the pH is adjusted to obtain a mixture, and the mixture is heated to obtain the CeVO4 powder.

[0034] In this invention, a cerium source and a template directing agent are mixed to obtain a first solution. Since the vanadium source has low solubility, it is prepared separately as a second solution. The first and second solutions are then mixed to obtain a reactant with better uniform particle size. In step (2), an alkaline solution is added to adjust the pH of the mixture. The pH value determines the morphology of the reaction product. Different morphological products will be obtained at different pH values.

[0035] As a preferred technical solution of the present invention, the cerium source in step (1) includes any one or a combination of at least two of cerium nitrate hexahydrate, cerium chloride, or cerium oxalate. Typical but non-limiting examples of such combinations include: a combination of cerium nitrate hexahydrate and cerium chloride, a combination of cerium chloride and cerium oxalate, or a combination of cerium nitrate hexahydrate and cerium oxalate.

[0036] Preferably, the template directing agent in step (1) includes EDTA and / or CTAB.

[0037] Preferably, the vanadium source in step (1) includes any one or a combination of at least two of potassium metavanadate, vanadium chloride, or ammonium metavanadate, wherein typical but non-limiting examples of the combination include: a combination of potassium metavanadate and vanadium chloride, a combination of potassium metavanadate and ammonium metavanadate, or a combination of vanadium chloride and ammonium metavanadate, etc.

[0038] Preferably, the solvent in step (1) includes water.

[0039] Preferably, the mass ratio of the cerium source, template directing agent, and vanadium source in step (1) is 1:(1~1.5):(0.8~1.2), wherein the mass ratio can be 1:1:0.8, 1:1:0.9, 1:1:1, 1:1:1.1, 1:1:1.2, 1:1.2:0.8, 1:1.2:1, 1:1.2:1.1, 1:1.2:1.2, 1:1.5:0.8, 1:1.5:0.9, 1:1.5:1, 1:1.5:1.1, or 1:1.5:1.2, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0040] As a preferred technical solution of the present invention, the pH of the mixture in step (2) is 9.0 to 11.0, wherein the pH can be 9.0, 9.2, 9.4, 9.6, 9.8, 10.0, 10.2, 10.4, 10.6, 10.8 or 11.0, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0041] If the pH of the mixture is too high, the material is likely to form a cube-shaped morphology; if the pH of the mixture is too low, CeVO4 crystals cannot be formed.

[0042] The heating in step (2) of this invention is carried out in a high-pressure sealed environment, and the heating atmosphere is an air atmosphere. The sealed environment improves the safety of heating.

[0043] Preferably, the heating temperature in step (2) is 150 to 200°C, wherein the temperature can be 150°C, 160°C, 170°C, 180°C, 190°C or 200°C, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0044] Preferably, the heating time in step (2) is 10 to 15 hours, wherein the time can be 10 hours, 11 hours, 12 hours, 13 hours, 14 hours or 15 hours, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0045] Preferably, the precipitate is obtained by heating and then cooling, and the precipitate is then washed, dried and calcined in sequence to obtain the CeVO4 powder.

[0046] The present invention involves calcination after heating to remove excess phases from the heated product, resulting in a purer final product.

[0047] Preferably, the calcination temperature is 400-500℃, wherein the temperature can be 400℃, 410℃, 420℃, 430℃, 440℃, 450℃, 460℃, 470℃, 480℃, 490℃ or 500℃, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0048] Preferably, the calcination time is 3 to 5 hours, wherein the time can be 3 hours, 4 hours or 5 hours, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0049] As a preferred technical solution of the present invention, the preparation method includes:

[0050] CeVO4 powder and MgH2 powder were ball-milled to obtain the CeVO4-MgH2 composite material with an average particle size of 200-300 nm. The ball milling speed was 450-550 rpm and the time was 20-28 h. During the ball milling, each ball milling session lasted 10-15 min, followed by a 4-8 min pause.

[0051] The preparation method of CeVO4 powder includes the following steps:

[0052] (1) A first solution is obtained by mixing a vanadium source and a template directing agent in a solvent, and a second solution is obtained by mixing a vanadium source in a solvent;

[0053] (2) After mixing the first solution and the second solution in step (1), adjust the pH to 9.0 to 11.0 to obtain a mixture. Heat the mixture at 150 to 200°C for 10 to 15 hours to obtain the CeVO4 powder.

[0054] A third objective of this invention is to provide an application of the CeVO4-MgH2 composite material as described in one objective, wherein the CeVO4-MgH2 composite material is applied in the field of hydrogen storage materials.

[0055] Compared with the prior art, the present invention has the following beneficial effects:

[0056] (1) This invention utilizes CeVO4 powder as a catalyst to synergistically catalytically modify the MgH2 hydrogen storage material system, which significantly improves the hydrogen absorption and desorption performance of the MgH2 hydrogen storage material. It can release 6.00 wt% of hydrogen within 6 minutes at 300℃ and 5.5 wt% of hydrogen within 20 minutes at 275℃.

[0057] (2) This invention utilizes CeVO4 powder as a catalyst to synergistically modify the MgH2 hydrogen storage material system, thereby obtaining a CeVO4-MgH2 composite hydrogen storage material with rapid hydrogen absorption and desorption kinetics. At temperatures of 1000℃, 150℃ and 200℃, the hydrogen absorption capacity within 200s can reach 2.2wt%, 4.08wt% and 5.52wt%, respectively.

[0058] (3) The present invention prepares CeVO4-MgH2 composite material by mechanical ball milling. The preparation process is simple, the preparation conditions are controllable, and the preparation cost is low. Attached Figure Description

[0059] Figure 1 This is the XRD pattern of CeVO4 in Embodiment 1 of the present invention.

[0060] Figure 2 This is the XRD pattern of the CeVO4-MgH2 composite material in Example 1 of this invention.

[0061] Figure 3 This is a TEM image of the CeVO4-MgH2 composite material in Example 1 of this invention.

[0062] Figure 4 These are TPD diagrams of MgH2 hydrogen storage materials with different CeVO4 doping contents in Examples 1, 4-7 of this invention, and the comparative example MgH2.

[0063] Figure 5 The isothermal hydrogen desorption curves of CeVO4-MgH2 composite material compared to pure MgH2 at 300℃ are shown in Example 1 of this invention.

[0064] Figure 6 These are the isothermal hydrogen absorption curves of the CeVO4-MgH2 composite material in Example 1 of this invention at different temperatures.

[0065] Figure 7 These are the isothermal hydrogen absorption curves of ball-milled pure MgH2 at different temperatures in Comparative Example 1 of this invention. Detailed Implementation

[0066] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0067] Example 1

[0068] This embodiment provides a CeVO4-MgH2 composite material with a diameter of 200-300 nm. The CeVO4-MgH2 composite material includes a core and a coating layer. The core includes MgH2, and the coating layer includes CeVO4. Based on the total mass of the CeVO4-MgH2 composite material as 100%, the mass fraction of CeVO4 is 10%, and the mass fraction of MgH2 is 90%.

[0069] This embodiment also provides a method for preparing the above-mentioned CeVO4-MgH2 composite material, the preparation method comprising:

[0070] CeVO4 powder with a diameter of 100 nm and MgH2 powder with a diameter of 5 μm were selected as raw materials, and the CeVO4 powder and MgH2 powder were ball-milled to obtain the CeVO4-MgH2 composite material.

[0071] The specific method of ball milling includes: weighing the powder and placing it into a 250ml stainless steel ball mill jar, and adding stainless steel grinding balls at a ball-to-powder ratio of 120:1. Remove the ball mill jar, filled with powder and grinding balls, from the glove box and purge it with 50 bar of hydrogen gas through the gas valve for protection. Then install the ball mill and rotate it forward and backward at 500 rpm, grinding for 12 minutes followed by a 6-minute rest, for a total grinding time of 24 hours. Every 6 hours, the jar needs to be placed back into the glove box for compaction to prevent excessive material sticking to the walls.

[0072] This embodiment also provides a method for preparing the above-mentioned CeVO4 powder, the preparation method comprising the following:

[0073] (1) Dissolve 3.47g Ce(NO3)3·6H2O and 2.92g EDTA in 25mL distilled water and stir for 30 minutes to obtain the first solution. Add 0.936g NH4VO3 to 25mL distilled water and stir to obtain the second solution.

[0074] (2) After mixing the first solution and the second solution, stir continuously for 30 minutes, then slowly add 1 mol / L NaOH solution to keep the pH value at 10 to obtain a mixture. Transfer the mixture to a 100 mL sealed polytetrafluoroethylene-lined high-pressure reactor and react at 180 °C for 12 h. Gradually cool to room temperature. The precipitate generated by heating is washed with deionized water and anhydrous ethanol, centrifuged at 10000 rpm for 5 min, washed several times with distilled water and ethanol, dried at 80 °C for 12 h, and finally calcined in a tube furnace at 450 °C for 4 h to obtain CeVO4 powder.

[0075] The XRD pattern of the CeVO4 powder prepared in this embodiment is as follows: Figure 1As shown, the XRD pattern of the prepared CeVO4-MgH2 composite material is as follows. Figure 2 As shown, Figure 1 The peak shapes of the spectrum correspond to those in card PDF#82-1969, indicating that the synthesized CeVO4 nanoparticles have a relatively complete crystal structure. After mechanically ball-milling MgH2 powder to coat it with a certain amount of CeVO4 powder, the XRD diffraction pattern of the composite powder was obtained. Figure 2 The main peak was a MgH2 phase diffraction peak, with a small amount of CeVO4 diffraction peaks. This indicates that the additive can be uniformly dispersed in the MgH2 powder after ball milling.

[0076] The TEM image of the CeVO4-MgH2 composite material prepared in this embodiment after ball milling is shown below. Figure 3 As shown, the average particle size is around 200-300 nm, and CeVO4 is uniformly coated on the surface of MgH2 particles.

[0077] Example 2

[0078] This embodiment provides a CeVO4-MgH2 composite material with a diameter of 200-300 nm. The CeVO4-MgH2 composite material includes a core and a coating layer. The core includes MgH2, and the coating layer includes CeVO4. Based on the total mass of the CeVO4-MgH2 composite material being 100%, the mass fraction of CeVO4 is 10%, and the mass fraction of MgH2 is 90%.

[0079] This embodiment also provides a method for preparing the above-mentioned CeVO4-MgH2 composite material, the preparation method comprising:

[0080] CeVO4 powder with a diameter of 50 nm and MgH2 powder with a diameter of 0.5 μm were selected as raw materials, and the CeVO4 powder and MgH2 powder were ball-milled to obtain the CeVO4-MgH2 composite material.

[0081] The specific method of ball milling includes: weighing the powder and placing it into a 250ml stainless steel ball mill jar, and adding stainless steel grinding balls at a ball-to-powder ratio of 100:1. Remove the ball mill jar, filled with powder and grinding balls, from the glove box and purge it with 50 bar of hydrogen gas through the gas valve for protection. Then install the ball mill and rotate it forward and backward at 450 rpm, grinding for 10 minutes followed by a 4-minute rest, for a total grinding time of 28 hours. Every 6 hours, the jar needs to be placed back in the glove box for compaction to prevent excessive material sticking to the walls.

[0082] This embodiment also provides a method for preparing the above-mentioned CeVO4 powder, the preparation method comprising the following:

[0083] (1) Dissolve 3.47g Ce(NO3)3·6H2O and 2.92g EDTA in 25mL distilled water and stir for 30 minutes to obtain the first solution. Add 0.936g NH4VO3 to 25mL distilled water and stir to obtain the second solution.

[0084] (2) After mixing the first solution and the second solution, stir continuously for 30 minutes, then slowly add 1 mol / L NaOH solution to keep the pH value at 9.0 to obtain a mixture. Transfer the mixture to a 100 mL sealed polytetrafluoroethylene-lined high-pressure reactor and react at 150 °C for 15 h. Gradually cool to room temperature. The precipitate generated by heating is washed with deionized water and anhydrous ethanol, centrifuged at 10000 rpm for 5 min, washed several times with distilled water and ethanol, dried at 80 °C for 12 h, and finally calcined in a tube furnace at 400 °C for 5 h to obtain CeVO4 powder.

[0085] Example 3

[0086] This embodiment provides a CeVO4-MgH2 composite material with a diameter of 200-300 nm. The CeVO4-MgH2 composite material includes a core and a coating layer. The core includes MgH2, and the coating layer includes CeVO4. Based on the total mass of the CeVO4-MgH2 composite material being 100%, the mass fraction of CeVO4 is 10%, and the mass fraction of MgH2 is 90%.

[0087] This embodiment also provides a method for preparing the above-mentioned CeVO4-MgH2 composite material, the preparation method comprising:

[0088] CeVO4 powder with a diameter of 100 nm and MgH2 powder with a diameter of 5 μm were selected as raw materials, and the CeVO4 powder and MgH2 powder were ball-milled to obtain the CeVO4-MgH2 composite material.

[0089] The specific method of ball milling includes: weighing the powder and placing it into a 250ml stainless steel ball mill jar, and adding stainless steel grinding balls at a ball-to-powder ratio of 140:1. Remove the ball mill jar, filled with powder and grinding balls, from the glove box and purge it with 50 bar of hydrogen gas through the gas valve for protection. Then install the ball mill and rotate it forward and backward at 550 rpm, grinding for 15 minutes followed by an 8-minute rest, for a total grinding time of 28 hours. Every 6 hours, the jar needs to be placed back in the glove box for compaction to prevent excessive material sticking to the walls.

[0090] This embodiment also provides a method for preparing the above-mentioned CeVO4 powder, the preparation method comprising the following:

[0091] (1) Dissolve 3.47g Ce(NO3)3·6H2O and 2.92g EDTA in 25mL distilled water and stir for 30 minutes to obtain the first solution. Add 0.936g NH4VO3 to 25mL distilled water and stir to obtain the second solution.

[0092] (2) After mixing the first solution and the second solution, stir continuously for 30 minutes, then slowly add 1 mol / L NaOH solution to keep the pH value at 11.0 to obtain a mixture. Transfer the mixture to a 100 mL sealed polytetrafluoroethylene-lined high-pressure reactor and react at 200 °C for 10 h. Gradually cool to room temperature. The precipitate generated by heating is washed with deionized water and anhydrous ethanol, centrifuged at 10000 rpm for 5 min, washed several times with distilled water and ethanol, dried at 80 °C for 12 h, and finally calcined in a tube furnace at 500 °C for 3 h to obtain CeVO4 powder.

[0093] Example 4

[0094] In this embodiment, all conditions are the same as in Example 1, except that "based on the total mass of the CeVO4-MgH2 composite material being 100%, the mass fraction of CeVO4 is 10%, and the mass fraction of MgH2 is 90%" is replaced with "based on the total mass of the CeVO4-MgH2 composite material being 100%, the mass fraction of CeVO4 is 5%, and the mass fraction of MgH2 is 95%".

[0095] Example 5

[0096] In this embodiment, all conditions are the same as in Example 1, except that "based on the total mass of the CeVO4-MgH2 composite material being 100%, the mass fraction of CeVO4 is 10%, and the mass fraction of MgH2 is 90%" is replaced with "based on the total mass of the CeVO4-MgH2 composite material being 100%, the mass fraction of CeVO4 is 7%, and the mass fraction of MgH2 is 93%".

[0097] Example 6

[0098] In this embodiment, all conditions are the same as in Example 1, except that "based on the total mass of the CeVO4-MgH2 composite material being 100%, the mass fraction of CeVO4 is 10% and the mass fraction of MgH2 is 90%" is replaced with "based on the total mass of the CeVO4-MgH2 composite material being 100%, the mass fraction of CeVO4 is 12% and the mass fraction of MgH2 is 88%".

[0099] Example 7

[0100] In this embodiment, all conditions are the same as in Example 1, except that "based on the total mass of the CeVO4-MgH2 composite material being 100%, the mass fraction of CeVO4 is 10% and the mass fraction of MgH2 is 90%" is replaced with "based on the total mass of the CeVO4-MgH2 composite material being 100%, the mass fraction of CeVO4 is 15% and the mass fraction of MgH2 is 85%".

[0101] Example 8

[0102] In this embodiment, except that step (2) of the CeVO4 powder preparation process does not involve calcination, all other conditions are the same as in Example 1.

[0103] Comparative Example 1

[0104] This comparative example directly uses pure MgH2 in a ball-milled state, that is, without coating MgH2 with CeVO4.

[0105] Comparative Example 2

[0106] In this comparative example, CeO2 powder with a diameter of approximately 100 nm and MgH2 powder with a diameter of 5 μm were selected as raw materials. The CeO2 powder and MgH2 powder were ball-milled to obtain CeO2-MgH2 composite material.

[0107] Comparative Example 3

[0108] In this comparative example, VO2 powder with a diameter of approximately 100 nm and MgH2 powder with a diameter of 5 μm were selected as raw materials. The VO2 powder and MgH2 powder were ball-milled to obtain VO2-MgH2 composite material.

[0109] To further compare the effects of different CeVO4 contents on the performance of MgH2 hydrogen storage materials, the present invention performed temperature programmed desorption (TPD) on the powders of Examples 1, 4, 5, 6, 7 and Comparative Example 1, and conducted isothermal hydrogen absorption and desorption performance tests on the 10wt% MgH2-CeVO4 powder in Example 1.

[0110] Figure 4 The figures show the temperature-programmed desorption volumetric hydrogen release curves for MgH2 hydrogen storage materials coated with 10 wt%, 5 wt%, 7 wt%, 12 wt%, and 15 wt% CeVO4 in Examples 1 and 4-7, respectively, and for ball-milled pure MgH2 in Comparative Example 1. The CeVO4 coating significantly reduced the hydrogen release temperature of MgH2, and the total hydrogen release tended to decrease with increasing coating weight. In Example 1, the initial dehydrogenation temperature of the composite material was reduced to 212°C while maintaining a high hydrogen release rate; the optimal coating weight was preferably 10 wt%.

[0111] Figure 5The isothermal hydrogen desorption curves of 10wt% MgH2-CeVO4 powder compared to ball-milled pure MgH2 at 300℃ are shown in Example 1. It can be seen that ball-milled MgH2 releases approximately 6.91wt% hydrogen in 60 minutes at 300℃; however, after coating with 10wt% CeVO4, the CeVO4-MgH2 composite powder exhibits excellent hydrogen desorption performance, releasing 6.00wt% hydrogen in 6 minutes at 300℃ and 5.5wt% hydrogen in 20 minutes at 275℃. This indicates that coating with 10wt% CeVO4 can effectively improve the hydrogen desorption kinetics of MgH2.

[0112] Figure 6 The MgH2 hydrogen storage material coated with 10 wt% CeVO4 was prepared in Example 1. Figure 7 The figures show the hydrogen absorption kinetics curves of the ball-milled pure MgH2 hydrogen storage material in Comparative Example 1 at different temperatures. Figure 6 and Figure 7 As can be seen, in Example 1, the MgH2 hydrogen storage material coated with 10wt% CeVO4 achieved hydrogen absorption of 2.2wt%, 4.08wt%, and 5.52wt% within 200s at temperatures of 100℃, 150℃, and 200℃, respectively. In contrast, the hydrogen absorption of ball-milled pure MgH2 within 1000s at 150℃ was less than 2wt%. Compared to ball-milled pure MgH2, the MgH2 hydrogen storage material coated with 10wt% CeVO4 exhibited excellent low-temperature hydrogen absorption kinetics.

[0113] The hydrogen absorption and hydrogen release of the materials in Examples 1-8 and Comparative Examples 1-3 were tested, and the test results are shown in Table 1.

[0114] The test conditions for hydrogen absorption and release were as follows: the initial hydrogen pressure was 50 bar. After the target temperature of 150°C was kept constant, the sample valve was opened directly, and the maximum isothermal hydrogen absorption was measured within 2 minutes. For hydrogen release, the sample was evacuated to 0.001 bar, the sample valve was closed, and the temperature was raised to 275°C and held for several minutes before the sample valve was opened. The maximum hydrogen release of the sample within 20 minutes was then measured.

[0115] Table 1

[0116] Hydrogen absorption capacity (2 min @ 150℃) Hydrogen release rate (20 min @ 275 °C) Example 1 4.02wt% 5.50wt% Example 2 4.23wt% 5.15wt% Example 3 3.89wt% 5.23wt% Example 4 3.35wt% 5.26wt% Example 5 3.42wt% 5.42wt% Example 6 3.56wt% 5.33wt% Example 7 3.26wt% 5.25wt% Example 8 3.81wt% 4.36wt% Comparative Example 1 0.58wt% 0.12wt% Comparative Example 2 4.09wt% 4.55wt% Comparative Example 3 3.95wt% 5.12wt%

[0117] The table above shows that in Examples 1-7, the hydrogen absorption and desorption performance was best when the mass fraction of CeVO4 was between 7% and 10%. The hydrogen absorption increased within 2 minutes at a constant temperature of 150°C, and the isothermal hydrogen desorption was greater than 5 wt% within 20 minutes at a constant temperature of 275°C. In Example 8, step (2) was not calcined, and the hydrogen absorption and desorption performance of the catalyst decreased compared to Example 1. Comparative Example 1 showed that pure MgH2 without CeVO4 coating, after ball milling, showed almost no hydrogen absorption or desorption in the above isothermal hydrogen absorption and desorption tests. In Comparative Examples 2-3, CeO2 or VO2 alone were used as additives, and the hydrogen absorption and desorption performance was good without the addition of CeVO4 as a catalyst.

[0118] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A CeVO4-MgH2 composite material, characterized in that, The CeVO4-MgH2 composite material includes a core and a coating layer, wherein the core includes MgH2 and the coating layer includes CeVO4.

2. The CeVO4-MgH2 composite material according to claim 1, characterized in that, The total mass of the CeVO4-MgH2 composite material is 100%, and the mass fraction of CeVO4 is 1~20%.

3. The CeVO4-MgH2 composite material according to claim 2, characterized in that, The mass fraction of CeVO4 is 3-12%.

4. The CeVO4-MgH2 composite material according to claim 3, characterized in that, The mass fraction of CeVO4 is 7-10%.

5. The CeVO4-MgH2 composite material according to claim 1, characterized in that, The raw materials for the CeVO4-MgH2 composite material include CeVO4 powder and MgH2 powder.

6. The CeVO4-MgH2 composite material according to claim 5, characterized in that, The CeVO4 powder is a spherical nanoparticle with a diameter of 50~100nm.

7. The CeVO4-MgH2 composite material according to claim 5, characterized in that, The MgH2 powder is in the form of spherical particles with a diameter of 0.5~5µm.

8. The CeVO4-MgH2 composite material according to claim 1, characterized in that, The CeVO4-MgH2 composite material has a diameter of 200~300nm.

9. A method for preparing the CeVO4-MgH2 composite material according to any one of claims 1-8, characterized in that, The preparation method includes: CeVO4 powder and MgH2 powder were ball-milled to obtain the CeVO4-MgH2 composite material.

10. The preparation method according to claim 9, characterized in that, The average particle size of the ball-milled CeVO4-MgH2 composite material is 200~300nm.

11. The preparation method according to claim 9, characterized in that, The ball-to-material ratio of the ball mill is 100~140:

1.

12. The preparation method according to claim 9, characterized in that, The ball milling speed is 450~550 rpm.

13. The preparation method according to claim 9, characterized in that, The ball milling time is 20-28 hours.

14. The preparation method according to claim 9, characterized in that, The ball milling process involves 10-15 minutes of milling followed by a 4-8 minute rest period.

15. The preparation method according to claim 9, characterized in that, The atmosphere used in the ball mill is an inert atmosphere.

16. The preparation method according to claim 15, characterized in that, The inert atmosphere includes hydrogen.

17. The preparation method according to claim 9, characterized in that, The method for preparing the CeVO4 powder includes the following steps: (1) A first solution is obtained by mixing a cerium source and a template directing agent in a solvent, and a second solution is obtained by mixing a vanadium source in a solvent; (2) After mixing the first solution and the second solution in step (1), the pH is adjusted to obtain a mixture, and the mixture is heated to obtain the CeVO4 powder.

18. The preparation method according to claim 17, characterized in that, The cerium source in step (1) includes any one or a combination of at least two of cerium nitrate hexahydrate, cerium chloride, or cerium oxalate.

19. The preparation method according to claim 17, characterized in that, The template directing agent in step (1) includes EDTA and / or CTAB.

20. The preparation method according to claim 17, characterized in that, The vanadium source in step (1) includes any one or a combination of at least two of potassium metavanadate, vanadium chloride, or ammonium metavanadate.

21. The preparation method according to claim 17, characterized in that, The solvent in step (1) includes water.

22. The preparation method according to claim 17, characterized in that, The mass ratio of the cerium source, template directing agent and vanadium source in step (1) is 1:(1~1.5):(0.8~1.2).

23. The preparation method according to claim 17, characterized in that, The pH of the mixture in step (2) is 9.0~11.

0.

24. The preparation method according to claim 17, characterized in that, The heating temperature in step (2) is 150~200℃.

25. The preparation method according to claim 17, characterized in that, The heating time in step (2) is 10~15h.

26. The preparation method according to claim 17, characterized in that, The precipitate is obtained by heating and then cooling. The precipitate is then washed, dried and calcined to obtain the CeVO4 powder.

27. The preparation method according to claim 26, characterized in that, The calcination temperature is 400~500℃.

28. The preparation method according to claim 26, characterized in that, The calcination time is 3-5 hours.

29. The preparation method according to claim 9, characterized in that, The preparation method includes: CeVO4 powder and MgH2 powder were ball-milled at 450-550 rpm for 20-28 hours, with a 4-8 minute pause after every 10-15 minutes of ball milling, to obtain a CeVO4-MgH2 composite material with an average particle size of 200-300 nm. The preparation method of CeVO4 powder includes the following steps: (1) The vanadium source and the template directing agent are mixed in a solvent to obtain a first solution, and the vanadium source is mixed in a solvent to obtain a second solution; (2) After mixing the first solution and the second solution in step (1), adjust the pH to 9.0~11.0 to obtain a mixture, and heat the mixture at 150~200℃ for 10~15h to obtain the CeVO4 powder.

30. The application of the CeVO4-MgH2 composite material as described in any one of claims 1-8, characterized in that, The CeVO4-MgH2 composite material is used in the field of hydrogen storage materials.

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