MgH2-based composite hydrogen storage material and preparation method thereof

Abstract

The invention discloses an MgH2-based composite hydrogen storage material and a preparation method thereof, and belongs to the technical field of energy and energy conservation. The composite material is formed by compounding MgH2 and a Fe2O3 / TiO2 porous ball-rod catalyst through high-energy ball milling, the Fe2O3 / TiO2 catalyst is prepared through a one-step hydrothermal method, (NH4) 2TiF6 serves as a titanium source, FeCl3 serves as an iron source, and the Fe2O3 / TiO2 catalyst is obtained after hydrothermal reaction, washing and drying. MgH2 and Fe2O3 / TiO2 are mixed according to the mass ratio of 94: 6, intermittent high-energy ball milling is conducted for 16 h in the argon atmosphere according to the ball-to-material ratio of 10: 1, and the target composite material is prepared. The Fe2O3 / TiO2 catalyst disclosed by the invention has both the hydrophobic characteristic of Fe and the hydrophilic characteristic of Ti, a bidirectional synergistic catalytic effect is formed, and the sphere-rod porous structure can improve the hydrogen diffusion condition and prevent MgH2 agglomeration. The obtained composite material has the advantages that the hydrogen absorption and desorption activation energy is obviously reduced, the dynamic rate is high, about 5.48 wt.% of hydrogen is absorbed in 1 minute at 300 DEG C, about 6.50 wt.% of hydrogen is desorbed in 10 minutes, 83.46% of initial hydrogen storage capacity is still maintained after 90 times of circulation, the thermodynamic property is stable, and the composite material has a wide application prospect in the field of solid hydrogen storage.

Description

Technical Field

[0001] This invention belongs to the field of energy and energy conservation technology, and relates to a MgH2-based composite hydrogen storage material and its preparation method. Background Technology

[0002] MgH2 possesses a high theoretical hydrogen storage capacity (7.6 wt.%) and is considered one of the most promising solid-state hydrogen storage materials. However, its high hydrogen absorption and desorption temperatures, slow reaction kinetics, and poor cycle stability restrict the development of magnesium-based energy storage materials. To improve its hydrogen storage performance, researchers have proposed various modification strategies, including catalysis, alloying, nano-sizing, and composite methods. Among these, catalytic modification is a simple and effective approach. By introducing transition metal catalysts into the system, the activation energy of the reaction can be significantly reduced, accelerating the hydrogen absorption and desorption rates of Mg / MgH2. However, single metal catalysts often only promote hydrogen absorption or desorption, making it difficult to perform bidirectional catalysis and improve the overall hydrogen storage cycle performance. Therefore, developing a composite catalytic system with a multiphase interface and synergistic catalysis of hydrogen-loving and hydrogen-phobic bimetallic catalysts has become crucial for improving the hydrogen storage performance of Mg / MgH2. This invention provides a MgH2-based composite hydrogen storage material and its preparation method. By introducing a nanoporous sphere-rod junction Fe2O3 / TiO2 multiphase catalyst, the hydrogen absorption and desorption kinetics and cycle stability of magnesium hydride are significantly improved. Summary of the Invention

[0003] To achieve the above-mentioned technical objectives and effects, the present invention provides the following technical solution:

[0004] A MgH2-based composite hydrogen storage material is provided, wherein the composite hydrogen storage material is composed of 94% MgH2 by mass and 6% Fe2O3 / TiO2 composite catalyst by mass, wherein the Fe2O3 / TiO2 composite catalyst is a microsphere with a porous sphere-rod structure.

[0005] Preferably, the Fe2O3 / TiO2 composite catalyst has a multiphase interface structure formed by Fe-O-Ti bond bridging.

[0006] On the other hand, the present invention also provides a method for preparing the MgH2-based composite hydrogen storage material as described above, comprising the following steps:

[0007] (1) Preparation of precursor solution: Weigh 5 mmol of (NH4)2TiF6 and 9 mmol of CO(NH2)2, add them to 50 mL of deionized water, and stir magnetically until completely dissolved to obtain a transparent solution;

[0008] (2) Adding an iron source: Prepare 50 mL of 0.2 M FeCl3 solution. Add the FeCl3 solution dropwise to the transparent solution in step (1) above, continue stirring, and sonicate for 20 min to obtain a homogeneous mixed solution;

[0009] (3) Hydrothermal reaction: The mixed solution was transferred to a 100 mL Teflon-lined high-pressure reactor and hydrothermally treated at 140 °C for 12 h. After the reaction was completed, it was naturally cooled to room temperature.

[0010] (4) Washing and drying: Remove the supernatant from the liner of the reactor, centrifuge the remaining turbid suspension, discard the supernatant after centrifugation, add deionized water to redisperse and centrifuge and wash again, repeat this cycle 3 times, place the obtained solid in a forced-air drying oven and dry at 60℃ for 12 h to obtain Fe2O3 / TiO2 powder with porous spherical-rod structure;

[0011] (5) Raw material weighing: Weigh 0.94g MgH2 and 0.06g Fe2O3 / TiO2 powder obtained in step (4), and place them together with 10g of grinding beads in a grinding jar;

[0012] (6) Ball milling: The ball milling jar is transferred to a high-energy ball mill and ball milling is carried out under a protective atmosphere;

[0013] (7) Product collection: After ball milling, the ball mill jar is transferred to the glove box, the sample is taken out, and the MgH2-based composite hydrogen storage material is obtained.

[0014] Preferably, the FeCl3 solution in step (2) is prepared by weighing 1.35g of FeCl3·6H2O and dissolving it in 50 mL of deionized water.

[0015] Preferably, the centrifugation process in step (4) is centrifugation at 10000 r / min for 5 min.

[0016] Preferably, the protective atmosphere in step (6) is an argon atmosphere.

[0017] Preferably, the ball milling process parameters in step (6) are: ball-to-material ratio of 10:1, intermittent ball milling process, ball milling for 10 minutes, pause for 10 minutes, and total ball milling time of 16 hours.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] This invention utilizes a one-step hydrothermal method to construct Fe₂O₃ / TiO₂ nanoporous catalysts, offering a simple and highly controllable preparation process. The resulting catalyst combines the hydrogen-repellent properties of Fe with the hydrogen-affinity properties of Ti, forming a synergistic effect at the interface. This simultaneously promotes the dissociation of hydrogen molecules and the migration of hydrogen atoms, achieving bidirectional catalysis of hydrogen absorption and desorption reactions. Furthermore, the unique spherical-rod-shaped porous structure macroscopically possesses a high specific surface area and abundant interconnected channels, significantly improving hydrogen diffusion and mass transfer conditions. During ball milling, this structure also acts as an effective "micro-spacer," preventing MgH₂ agglomeration and sintering, promoting its refinement and uniform dispersion, thereby enhancing the contact stability between the catalytic phase and the matrix.

[0020] Performance testing revealed that the prepared MgH2-based composite hydrogen storage material exhibited excellent hydrogen storage kinetics and cycling stability. Its hydrogen absorption and desorption activation energies decreased to approximately 67.8 kJ / mol and 70.8 kJ / mol, respectively. At 300℃, it could absorb approximately 5.48 wt.% H2 within 1 minute and release approximately 6.50 wt.% H2 within 10 minutes, while maintaining essentially unchanged thermodynamic properties (ΔH≈75.86 kJ / mol), indicating that the catalyst primarily functions through kinetic regulation. After 90 hydrogen absorption and desorption cycles, the material retained approximately 83.46% of its initial hydrogen storage capacity, demonstrating excellent anti-sintering properties and structural stability. The superior hydrogen storage performance of the MgH2-based composite hydrogen storage material stems from the synergistic catalytic mechanism of the Fe2O3 / TiO2 catalyst: Fe... 3+ The site facilitates the dissociation of hydrogen molecules, Ti 4 + The site promotes the migration of hydrogen atoms, while the stable Fe-O-Ti bond bridge enhances interfacial electron transfer and structural stability, thereby achieving a continuous and efficient catalytic effect. Attached Figure Description

[0021] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the description of the specific embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 (a) is the isothermal hydrogen desorption curve of MgH2+x wt.%Fe2O3 / TiO2 (x=3, 6, 9) at 300℃;

[0023] Figure 1 (b) isothermal hydrogen absorption curves of MgH2+x wt.%Fe2O3 / TiO2 (x=3, 6, 9) at 300℃;

[0024] Figure 1(c) is the isothermal hydrogen absorption curves of the MgH2+6wt.% Fe2O3 / TiO2 composite material at 225℃, 250℃, 275℃, 300℃, and 325℃ with a pressure of 30 bar;

[0025] Figure 1 (d) shows the isothermal hydrogen desorption curves of the MgH2+6wt.% Fe2O3 / TiO2 composite material at 225℃, 250℃, 275℃, 300℃, and 325℃.

[0026] Figure 2 (a) is a fitting plot of hydrogen absorption data at 300℃ for nine kinetic models of MgH2+6wt.% Fe2O3 / TiO2 composite material;

[0027] Figure 2 (b) shows the fitting curves of hydrogen absorption data of the D3 model of MgH2+6wt.% Fe2O3 / TiO2 composite material at different temperatures;

[0028] Figure 2 (c) is the activation energy fitting curve of the MgH2+6wt.% Fe2O3 / TiO2 composite material;

[0029] Figure 2 (d) is a fitting plot of hydrogen absorption data at 300℃ for nine kinetic models of MgH2+6wt.% Fe2O3 / TiO2 composite material;

[0030] Figure 2 (e) shows the fitting curves of hydrogen release data of the MgH2+6wt.% Fe2O3 / TiO2 composite material at different temperatures using the A2 model.

[0031] Figure 2 (f) is the activation energy fitting curve of the MgH2+6wt.% Fe2O3 / TiO2 composite material;

[0032] Figure 3 (a) PCT curves of the MgH2+6wt.% Fe2O3 / TiO2 composite material at 275℃, 300℃ and 325℃;

[0033] Figure 3 (b) Vant'Hoff plot and its fitted line for the MgH2+6wt.% Fe2O3 / TiO2 composite material;

[0034] Figure 3 (c) shows the isothermal cyclic hydrogen absorption and desorption curves of the MgH2+6wt.% Fe2O3 / TiO2 composite material at 300℃. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] The invention will now be further described with reference to the accompanying drawings.

[0037] Example 1

[0038] 1. Fe2O3 / TiO2 composite catalyst

[0039] 1.1 Preparation of precursor solution

[0040] Weigh 0.99 g (NH4)2TiF6 (5 mmol) and 0.54 g CO(NH2)2 (9 mmol), add them to 50 mL of deionized water, and stir continuously on a magnetic stirrer until the solid is completely dissolved to obtain a transparent precursor solution.

[0041] 1.2 Adding iron source

[0042] Weigh 1.35g FeCl3・6H2O and dissolve it in 50 mL of deionized water to prepare 50 mL of 0.2M FeCl3 solution; add the FeCl3 solution dropwise to the above precursor solution, continue stirring, and then transfer it to an ultrasonic cleaner for ultrasonic dispersion for 20 min to form a homogeneous mixed solution.

[0043] 1.3 Hydrothermal Reaction

[0044] The homogeneous mixture was transferred to a 100 mL Teflon-lined high-pressure reactor, sealed, and placed in a constant-temperature oven at 140 °C for 12 h for hydrothermal reaction. After the reaction was completed, the oven was turned off and the reactor was allowed to cool naturally to room temperature.

[0045] 1.4 Washing and Drying

[0046] Open the reactor, remove the supernatant from the liner, transfer the remaining turbid suspension to a 50ml centrifuge tube, place it in a high-speed centrifuge, and centrifuge at 10000r / min for 5min. After centrifugation, discard the supernatant, add deionized water to redisperse the precipitate, centrifuge and wash again, and repeat this process 3 times. Place the washed solid precipitate in a drying oven and dry it at 60℃ for 12h to obtain Fe2O3 / TiO2 composite catalyst powder with a porous spherical-rod structure.

[0047] 2. Preparation of MgH2-based composite hydrogen storage materials

[0048] 2.1 Weighing raw materials

[0049] Inside the glove box, accurately weigh 0.94g of MgH2 powder and 0.06g of the Fe2O3 / TiO2 composite catalyst powder prepared above, add them together to the ball mill jar, and add 10g of milling beads to ensure that the ball-to-material ratio is 10:1.

[0050] 2.2 Ball milling composite

[0051] After sealing the ball mill jar, remove it from the glove box and transfer it to the high-energy ball mill. Introduce argon gas as a protective atmosphere and set the ball milling process parameters as follows: intermittent ball milling (10 minutes of ball milling, 10 minutes of pause), with a total ball milling time of 16 hours.

[0052] 2.3 Product Collection

[0053] After ball milling, the milling jar is transferred to a glove box, the jar opening is opened, and the sample is taken out, which is the MgH2-based composite hydrogen storage material.

[0054] Performance Testing and Results Analysis

[0055] The hydrogen storage performance of the MgH2-based composite hydrogen storage material prepared in Example 1 was tested:

[0056] (1) Isothermal hydrogen absorption and desorption performance test

[0057] The prepared MgH2-based composite hydrogen storage material was placed under different temperature conditions (225℃, 250℃, 275℃, 300℃, 325℃), and isothermal hydrogen absorption and desorption tests were conducted using a hydrogen storage performance testing system. The results are as follows: Figure 1 As shown, at 300℃, the hydrogen absorption capacity of this composite material can reach 5.48 wt.% within 1 minute, and the hydrogen release capacity is about 6.50 wt.% within 10 minutes. As the temperature increases, the hydrogen absorption and release rate increases significantly, and the time to reach hydrogen saturation at 325℃ is further shortened, indicating that the material has excellent hydrogen storage kinetics performance in the medium and high temperature range.

[0058] (2) Dynamic analysis

[0059] Nine kinetic models were used to fit the hydrogen absorption and desorption data of the composite material at 300℃, such as... Figure 2 As shown, the results indicate that the D3 model had the highest good fit (R²=0.996) during hydrogen absorption, with an activation energy of 67.80±3.54 kJ / mol; while the A2 model had the best good fit (R²=0.997) during hydrogen release, with an activation energy of 70.84±17.38 kJ / mol, which was significantly lower than the hydrogen absorption and release activation energies of pure MgH2. This confirms that the synergistic catalytic effect of the Fe2O3 / TiO2 catalyst effectively reduced the reaction energy barrier.

[0060] (3) Thermodynamic and Cyclic Stability Tests

[0061] Analysis of PCT curves and Vant'Hoff plots showed that the thermodynamic properties of the composite material (ΔH≈75.86kJ / mol) were basically consistent with those of pure MgH2, indicating that the catalyst mainly improves hydrogen storage performance through kinetic regulation. After 90 hydrogen absorption and desorption cycles at 300℃, the material still maintained 83.46% of its initial hydrogen storage capacity, demonstrating good cycle stability and anti-sintering ability. This is attributed to the porous spherical-rod structure of the Fe2O3 / TiO2 catalyst and the stable multiphase interface formed by Fe-O-Ti bond bridges.

[0062] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0063] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A MgH2-based composite hydrogen storage material, characterized in that, The composite hydrogen storage material is composed of 94% MgH2 and 6% Fe2O3 / TiO2 composite catalyst, wherein the Fe2O3 / TiO2 composite catalyst is a microsphere with a porous sphere-rod structure.

2. The MgH2-based composite hydrogen storage material according to claim 1, characterized in that, The Fe2O3 / TiO2 composite catalyst has a multiphase interface structure formed by Fe-O-Ti bond bridging.

3. A method for preparing the MgH2-based composite hydrogen storage material as described in claim 1 or 2, characterized in that, Includes the following steps: (1) Preparation of precursor solution: Weigh 5 mmol of (NH4)2TiF6 and 9 mmol of CO(NH2)2, add them to 50 mL of deionized water, and stir magnetically until completely dissolved to obtain a transparent solution; (2) Adding an iron source: Prepare 50 mL of 0.2 M FeCl3 solution. Add the FeCl3 solution dropwise to the transparent solution in step (1) above, continue stirring, and sonicate for 20 min to obtain a homogeneous mixed solution; (3) Hydrothermal reaction: The mixed solution was transferred to a 100 mL Teflon-lined high-pressure reactor and hydrothermally treated at 140 °C for 12 h. After the reaction was completed, it was naturally cooled to room temperature. (4) Washing and drying: Remove the supernatant from the liner of the reactor, centrifuge the remaining turbid suspension, discard the supernatant after centrifugation, add deionized water to redisperse and centrifuge and wash again, repeat this cycle 3 times, place the obtained solid in a forced-air drying oven and dry at 60℃ for 12 h to obtain Fe2O3 / TiO2 powder with porous spherical-rod structure; (5) Raw material weighing: Weigh 0.94g MgH2 and 0.06g Fe2O3 / TiO2 powder obtained in step (4), and place them together with 10g of grinding beads in a grinding jar; (6) Ball milling: The ball milling jar is transferred to a high-energy ball mill and ball milling is carried out under a protective atmosphere; (7) Product collection: After ball milling, the ball mill jar is transferred to the glove box, the sample is taken out, and the MgH2-based composite hydrogen storage material is obtained.

4. The preparation method according to claim 3, characterized in that, The FeCl3 solution in step (2) is prepared by weighing 1.35g of FeCl3·6H2O and dissolving it in 50 mL of deionized water.

5. The preparation method according to claim 3, characterized in that, In step (4), the centrifugation process involves centrifuging at 10,000 r / min for 5 min.

6. The preparation method according to claim 3, characterized in that, The protective atmosphere mentioned in step (6) is an argon atmosphere.

7. The preparation method according to claim 3, characterized in that, The ball milling process parameters in step (6) are: ball-to-material ratio of 10:1, intermittent ball milling process, ball milling for 10 minutes, pause for 10 minutes, and total ball milling time of 16 hours.

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