An ordered porous reticulated iron oxide doped lithium aluminum hydride hydrogen storage material and a preparation method thereof

Abstract

The application discloses an ordered porous net-like iron oxide doped lithium aluminum hydride hydrogen storage material, which is prepared by mixing lithium aluminum hydride and ordered porous net-like iron oxide through ball milling, the micro-morphology of the ordered porous net-like iron oxide is a layered ordered porous net-like morphology, and the surface pore diameter of the layered ordered porous net-like morphology is 200 nm; the ordered porous net-like iron oxide is prepared by calcining a precipitate generated by static drying of ferrous acetate in a mixed solution of polymethyl methacrylate and ethanol; and the adding amount of the ordered porous net-like iron oxide accounts for 3-10 wt.% of the total mass. The preparation method comprises the following steps: 1, polymethyl methacrylate preparation; 2, preparation of ordered porous net-like iron oxide; and 3, preparation of ordered porous net-like iron oxide doped lithium aluminum hydride hydrogen storage material. As application in the field of hydrogen storage, the system initial hydrogen release temperature is 65-84 DEG C when the catalyst adding amount is 3-10 wt.%; the total hydrogen release amount is 6.83-7.35 wt.% and the hydrogen release rate is 72.16-73.94% when the temperature is raised to 300 DEG C.

Description

Technical Field

[0001] This invention relates to the technical field of hydrogen storage materials in new energy materials, specifically to an ordered porous network iron oxide-doped lithium aluminum hydride hydrogen storage material and its preparation method. Background Technology

[0002] Among solid-state hydrogen storage materials, lithium aluminum hydride (LiAlH4) possesses a theoretical hydrogen storage capacity as high as 10.5 wt.%, but it suffers from problems such as excessively high hydrogen desorption temperature, slow hydrogen desorption kinetics, and reversibility. Currently, a common solution is to dope LiAlH4 with metal catalysts to improve its hydrogen storage performance.

[0003] For example, existing literature 1 (Chunmin Zhang, Long Liang, et al. Dehydrogenation behavior and mechanism of LiAlH4 adding nanoCeO2 with different morphologies.[J].J.Nano Res.,16(2023),pp.9426-9434.) prepared nano-cerium oxide-doped lithium aluminum hydride composite hydrogen storage material by ball milling, achieving an initial hydrogen desorption temperature reduced to 76.6℃ and a total hydrogen desorption capacity of 7.17 wt.%. This technical solution improves dehydrogenation performance by providing more active sites due to the defect structure generated by the expansion of the CeO2 lattice. However, the oxygen vacancies formed by CeO2 doping suffer from insufficient migration, thus limiting the reaction rate and overall catalytic performance; furthermore, Ce, as a rare earth element, also presents the problem of high cost.

[0004] Doping with non-precious metals and non-rare earth elements can also improve hydrogen storage performance. For example, existing literature 2 (Li Z, Li P, Wan Q, et al. Dehydrogenation improvement of LiAlH4 catalyzed by Fe2O3 and Co2O3 nanoparticles[J]. J.Phys.Chem.C,2013,(36):18343-18352.) prepared cobalt oxide-doped lithium aluminum hydride composite hydrogen storage material by ball milling, achieving an initial hydrogen release temperature of 76℃ and a total hydrogen release of 7.3 wt.%. This technical solution also uses metal oxide doping to form finely dispersed Co nanoparticles during ball milling, which serve as active sites for the nucleation and growth of dehydrogenation products, promoting the dehydrogenation of lithium aluminum hydride. However, due to the inherent characteristics of cobalt oxide used in this technical solution, it has a low electronic conductivity, and its effect on lowering the desorption barrier of Al-H bonds cannot meet the application requirements.

[0005] Based on existing technology research, the inventors discovered that Fe, due to its multiple oxidation states and high electronic conductivity, can effectively reduce the desorption energy barrier of Al-H bonds and accelerate electron transfer, thereby improving hydrogen storage performance; at the same time, the raw material cost of Fe doping is far lower than that of other metal materials.

[0006] For example, existing literature 3 (Mengchen Song, Liuting Zhang, et al. Unraveling the degradation mechanism for the hydrogen storage property of Fe nanocatalyst-modified MgH2.[J]Inorg Chem Front,9:2874.) prepared nano-iron-doped magnesium hydride composite hydrogen storage material by ball milling, achieving an initial hydrogen release temperature reduced to 182.3℃, which is 147.7℃ lower than that of pure MgH2, and a total hydrogen release of 7.4 wt.%. Although this technical solution proves that doping with Fe can improve hydrogen storage performance, a comparison with existing literature 1 and literature 2 shows that the technical effect of existing literature 3 is far lower than that of the existing literature. The reasons are mainly twofold:

[0007] 1. This technical solution directly dops with elemental Fe instead of a compound. Since elemental iron cannot form abundant oxygen vacancies and active sites, nor can it achieve multiple oxidation states to improve electron transfer capabilities, it cannot effectively improve the hydrogen storage performance of lithium aluminum hydride.

[0008] 2. This technical solution, due to the direct doping of elemental iron, exhibits agglomeration, resulting in poor dispersibility. This phenomenon can be confirmed by its SEM image.

[0009] To address the technical problems in existing literature 3, modification can be achieved by adding Fe oxides. See the aforementioned existing literature 2 for details. This literature also describes a technical solution involving Fe2O3 doping—its technical effect is superior to that of Co2O3 doping. Existing literature 3 demonstrates that iron oxide doping can effectively improve the hydrogen storage performance of LiAlH4. This is because iron oxide itself possesses good chemical and thermal stability. When nano-sized through ball milling, it achieves beneficial technical effects such as high specific surface area and increased active sites while maintaining structural stability during subsequent catalytic processes, thereby enhancing catalytic activity.

[0010] However, further analysis of existing literature 2 shows that the Fe2O3 obtained by this technical solution is in a state of random stacking. The reason is that the ball milling method leads to uneven particle size distribution and agglomeration. Summary of the Invention

[0011] The purpose of this invention is to provide an ordered porous network iron oxide-doped lithium aluminum hydride hydrogen storage material and its preparation method.

[0012] According to the Pauling scale, iron has an electronegativity of 1.83. Therefore, when iron forms a complex with lithium aluminum hydride (LiAlH4), it acts as both an electron donor and acceptor, thereby altering the electron distribution in LiAlH4. The basic principle is that the electronegativity of iron can induce Li... + The charge shifts, and to ensure charge balance, [AlH4] - The charge of the group also changes accordingly, leading to the instability of the Al-H bond, reducing the desorption energy barrier of the Al-H bond, which is conducive to the dissociation of hydrogen, thereby reducing the initial hydrogen release temperature of the dehydrogenation process; at the same time, since iron oxide has multiple oxidation states and high electronic conductivity, it acts as a catalyst to promote the charge migration at the LiAlH4 interface.

[0013] Based on this, uniformly distributing LiAlH4 on an ordered porous network structure can increase the effective contact area between the catalyst and LiAlH4, thereby improving the hydrogen desorption kinetics and comprehensively enhancing the hydrogen desorption effect of LiAlH4.

[0014] Based on the above fundamental principles, the method of this invention to solve the existing technology is to adjust the LiAlH4 hydrogen storage material by preparing an ordered porous network of iron oxide, thereby controlling the hydrogen release process of the LiAlH4 hydrogen storage material and achieving the following two technical effects simultaneously:

[0015] 1. By uniformly distributing LiAlH4 on a regular and ordered porous structure, the effective contact area between the catalyst and LiAlH4 is increased, the diffusion path of charge or H is shortened, and the initial hydrogen release temperature of the dehydrogenation process is reduced.

[0016] 2. By reducing the amount of catalyst added, more hydrogen was released during the entire hydrogen release process, with the final hydrogen release amount reaching 7.22 wt.%.

[0017] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:

[0018] An ordered porous network iron oxide-doped lithium aluminum hydride hydrogen storage material is prepared by ball milling a mixture of lithium aluminum hydride and ordered porous network iron oxide. The ordered porous network iron oxide has a layered ordered porous network morphology with a surface pore diameter of 200 nm. The ordered porous network iron oxide is prepared by calcining a precipitate formed by ferrous acetate being dried in a mixed solution of polymethyl methacrylate and ethanol.

[0019] The ordered porous network of iron oxide is added at a rate of 3-10 wt.% of the total mass.

[0020] A method for preparing an ordered porous network iron oxide-doped lithium aluminum hydride hydrogen storage material includes the following steps:

[0021] Step 1: Preparation of polymethyl methacrylate (PMMA). Methyl methacrylate and potassium persulfate are mixed in a specific ratio, with potassium persulfate acting as an initiator. First, potassium persulfate is placed in deionized water to obtain solution A. Then, under specific conditions, methyl methacrylate is placed in solution A and stirred to react. After the reaction is complete, the mixture is filtered and dried. Finally, the resulting product is ground under specific conditions to obtain polymethyl methacrylate, abbreviated as PMMA.

[0022] In step 1, the ratio of methyl methacrylate to potassium persulfate is 1L:20g;

[0023] In step 1, the stirring reaction conditions are as follows: under argon atmosphere, the stirring speed is 80-90 rpm / min, the stirring temperature is 80℃, and the stirring time is 40-50 min.

[0024] In step 1, the grinding conditions are as follows: grinding time is 1-2 hours;

[0025] Step 2, Preparation of ordered porous network iron oxide: PMMA obtained in Step 1, ferrous acetate, citric acid monohydrate, and F127 are mixed in a specific ratio. First, F127 is placed in a 40% ethanol aqueous solution to obtain solution A. Then, ferrous acetate and citric acid monohydrate are placed in solution A and magnetically stirred under certain conditions to obtain solution B. Afterward, PMMA is dissolved fully in solution B and allowed to stand under certain conditions. After standing, the resulting product is dried under certain conditions. After drying, the resulting product is ground to obtain powder C. Finally, powder C is calcined under certain conditions to obtain ordered porous network iron oxide, abbreviated as 3DOM-FO.

[0026] In step 2, the ratio of PMMA, ferrous acetate, citric acid monohydrate and F127 is 5g:0.01mol:0.01mol:1g;

[0027] In step 2, the stirring conditions for preparing solution B are: stirring time of 10-20 min; the standing conditions for solution B are: standing time of 4-5 h; and the drying conditions after standing are: drying temperature of 50-60℃ and drying time of 12-16 h.

[0028] In step 2, the calcination conditions are: heating rate of 1-2℃ / min, calcination temperature of 450℃, and calcination time of 5h.

[0029] Step 3: Preparation of ordered porous network iron oxide doped lithium aluminum hydride hydrogen storage material. The 3DOM-FO obtained in step 2 and lithium aluminum hydride LAH are mixed in a certain mass ratio. Under certain conditions, the 3DOM-FO and LAH are ball-milled to obtain the ordered porous network iron oxide doped lithium aluminum hydride hydrogen storage material, abbreviated as 3DOM-FO / LAH.

[0030] In step 3, the mass ratio of 3DOM-FO to LAH is 0.075:1;

[0031] In step 3, the ball milling conditions are as follows: under argon gas, the ball-to-material ratio is (180-200):1, the ball milling speed is (400-500) r / min, and the ball milling time is 1-2 h.

[0032] An ordered porous network iron oxide-doped lithium aluminum hydride hydrogen storage material, when used in the field of hydrogen storage, has an initial hydrogen release temperature of 65-84℃ when the catalyst addition is 3-10 wt.%; when the temperature is raised to 300℃, the total hydrogen release is 6.83-7.35 wt.%, and the hydrogen release rate is 72.16-73.94%.

[0033] The technical effects of this invention have been tested experimentally, and the specific details are as follows:

[0034] To demonstrate the successful preparation of the ordered porous network iron oxide material, XRD tests were performed, and the results are as follows: Figure 2 As shown, the diffraction peaks of the ordered porous network of iron oxide are consistent with the characteristic peaks of Fe2O3. The test results indicate that the composition of 3DOM-FO is Fe2O3.

[0035] To demonstrate the structural characteristics of the ordered porous network iron oxide material, SEM measurements were performed, and the results are as follows: Figure 3 As shown, the porous material prepared by this invention is an ordered porous network structure with a pore size of 200 nm. Its solid walls are composed of nanoparticles with relatively uniform size, and there are also wormhole-like mesoporous structures on the inner walls of the pores.

[0036] To demonstrate the worm-like mesopores on the inner walls of the ordered porous network of iron oxide in the dopant, a BET test was performed, such as... Figure 4 , Figure 5 As shown, the pores are interconnected by mesopores, and the pore size of the sample is mainly concentrated at 37.0 nm.

[0037] To demonstrate the effect of the amount of ordered porous network iron oxide as a catalyst on the hydrogen desorption performance of lithium aluminum hydride, 3DOM-FO-doped lithium aluminum hydride hydrogen storage materials were prepared with 3DOM-FO addition amounts of 0 wt.%, 3 wt.%, 7 wt.%, and 10 wt.%. Temperature-induced hydrogen desorption tests were conducted, confirming that the initial hydrogen desorption temperature of the 3DOM-FO-added lithium aluminum hydride hydrogen storage materials was 65-84℃, which was 77-96℃ lower than that of pure lithium aluminum hydride, and the total hydrogen desorption capacity reached 6.83-7.35 wt.%.

[0038] Therefore, the present invention has the following advantages over the prior art:

[0039] 1. The hydrogen storage material prepared by the present invention effectively improves the hydrogen desorption performance of lithium aluminum hydride, has a lower initial hydrogen desorption temperature, and achieves a high final hydrogen desorption capacity with the addition of a small amount of catalyst.

[0040] 2. By utilizing nano-sized iron oxide to form a regular porous structure, the specific surface area is increased, providing more active sites, thereby reducing the initial hydrogen desorption temperature of the dehydrogenation process and ultimately improving the hydrogen desorption performance of LiAlH4.

[0041] 3. The method used to prepare 3DOM-FO in this invention has the advantages of low cost, controllable reaction and easy large-scale preparation. Attached image description:

[0042] Figure 1 This is a SEM image of the PMMA prepared according to a specific embodiment 1 of the present invention;

[0043] Figure 2 The XRD patterns of 3DOM-FO and 3DOM-ZO prepared in Specific Example 1 and Comparative Example 2 of the present invention are shown.

[0044] Figure 3 This is a SEM image of the ordered porous network iron oxide 3DOM-FO prepared in Specific Embodiment 1 of the present invention;

[0045] Figure 4 The image shown is a BET diagram of the ordered porous network iron oxide prepared in Specific Embodiment 1 of the present invention.

[0046] Figure 5 The pore size distribution curve of the ordered porous network iron oxide prepared in Specific Embodiment 1 of the present invention;

[0047] Figure 6 The dehydrogenation curves of LAH with doped 3DOM-FO addition amounts of 7 wt.%, 3 wt.%, and 10 wt.% in specific embodiments 1-3 of the present invention are shown.

[0048] Figure 7The dehydrogenation curve of LAH doped with 0 wt.% 3DOM-FO is shown in the figure for Comparative Example 1 of this invention.

[0049] Figure 8 SEM image of the ordered porous network zirconia prepared in Comparative Example 2 of the present invention;

[0050] Figure 9 The dehydrogenation curve of LAH doped with 7 wt.% 3DOM-ZO is shown in the specific comparative example 2 of this invention.

[0051] Figure 10 The dehydrogenation curve of LAH doped with 7 wt.% PMMA is shown in the specific comparative example 3 of this invention.

[0052] Figure 11 The dehydrogenation curve of LAH doped with 7 wt.% Fe2O3 is shown in the specific comparative example 4 of this invention. Detailed Implementation

[0053] The present invention will be further described in detail through embodiments and with reference to the accompanying drawings, but this is not intended to limit the scope of the invention.

[0054] Example 1

[0055] A method for preparing an ordered porous network iron oxide-doped lithium aluminum hydride hydrogen storage material includes the following steps:

[0056] Step 1: Preparation of polymethyl methacrylate (PMMA). Using a ratio of methyl methacrylate to potassium persulfate of 1L:20g, with potassium persulfate as the initiator, firstly, 0.8g of potassium persulfate was placed in 360mL of deionized water to obtain solution A. Then, under argon atmosphere, 40mL of methyl methacrylate was placed in solution A, and the mixture was stirred at 80℃ for 45min. After the reaction was complete, the mixture was filtered and dried. Finally, the resulting product was ground for 1h to obtain polymethyl methacrylate, abbreviated as PMMA.

[0057] To demonstrate the microstructure of PMMA, SEM testing was performed. The test results are as follows: Figure 1 As shown, PMMA is a layered, ordered microsphere structure with a diameter of 200 nm.

[0058] Step 2, Preparation of ordered porous network iron oxide: Using PMMA obtained in Step 1, ferrous acetate, citric acid monohydrate, and F127 in a ratio of 5g:0.01mol:0.01mol:1g, firstly, 1g of F127 was placed in a 40% ethanol aqueous solution to obtain solution A. Then, 1.7393g of ferrous acetate and 2.1014g of citric acid monohydrate were placed in solution A and magnetically stirred for 10min to obtain solution B. Next, 5g of PMMA was dissolved in solution B and allowed to stand for 4h. After standing, the product was dried at 50℃ for 12h. After drying, the product was ground to obtain powder C. Finally, powder C was calcined at a heating rate of 1℃ / min, a calcination temperature of 450℃, and a calcination time of 5h to obtain ordered porous network iron oxide, abbreviated as 3DOM-FO.

[0059] To confirm the composition of 3DOM-FO, XRD tests were performed. The test results are as follows: Figure 2 As shown, the diffraction peaks of 3DOM-FO are consistent with the characteristic peaks of Fe2O3. The test results indicate that the composition of 3DOM-FO is Fe2O3.

[0060] To demonstrate the microstructure of 3DOM-FO, SEM testing was performed. The test results are as follows: Figure 3 As shown, 3DOM-FO is an ordered porous network structure with a pore size of 200 nm. Its solid walls are composed of relatively uniformly sized nanoparticles, and wormhole-like mesoporous structures also exist on the inner walls of the pores. Compared with the PMMA obtained in step 1, it can be seen that the PMMA as a whole has a layered and ordered structure. After removing the PMMA, 3DOM-FO has a layered porous network structure with uniform pore size and orderly arrangement.

[0061] To further demonstrate the pore structure of 3DOM-FO, BET tests were performed. The test results are as follows: Figure 4 and Figure 5 As shown, the specific surface area of ​​3DOM-FO is 183.63 m². 2 ·g -1 Its pore size distribution ranges from 2 to 50 nm, with the pore size distribution concentrated at 37.0 nm.

[0062] Step 3: Preparation of ordered porous network iron oxide-doped lithium aluminum hydride hydrogen storage material. Using the mass ratio of 3DOM-FO obtained in Step 2 to lithium aluminum hydride (LAH) of 0.075:1, under argon atmosphere, 0.0210 g of 3DOM-FO and 0.2790 g of LAH are ball-milled at a ball-to-material ratio of 200:1, a ball milling speed of 400 r / min, and a ball milling time of 1 h. This yields an ordered porous network iron oxide-doped lithium aluminum hydride hydrogen storage material with a 3DOM-FO addition of 7 wt.%, abbreviated as 3DOM-FO / LAH-7.

[0063] To demonstrate the dehydrogenation performance of 3DOM-FO / LAH-7, specifically the role of 3DOM-FO as an LAH catalyst, a temperature-intensity dehydrogenation test was conducted. The test conditions were a heating rate of 3 °C / min and a heating temperature of 300 °C. The test results for the dehydrogenation performance of 3DOM-FO / LAH-7 are as follows: Figure 6 As shown, the initial hydrogen release temperature of 3DOM-FO / LAH-7 is 75℃; when the temperature is raised to 300℃, the hydrogen release amount is 7.22wt.%, and the hydrogen release rate is 73.94%.

[0064] To demonstrate the effect of 3DOM-FO as a catalyst on the hydrogen desorption performance of lithium aluminum hydride, Comparative Example 1 is provided, which is a lithium aluminum hydride hydrogen storage material without the addition of 3DOM-FO.

[0065] Comparative Example 1

[0066] A method for preparing lithium aluminum hydride hydrogen storage material without the addition of 3DOM-FO, i.e., lithium aluminum hydride hydrogen storage material with 0 wt.% 3DOM-FO, is as follows: the steps unless otherwise specified are the same as in Example 1, except that in step 3, 3DOM-FO is not added, i.e. only 0.3000 g of LAH is weighed and ball-milled to obtain lithium aluminum hydride hydrogen storage material without the addition of 3DOM-FO, abbreviated as mill-LAH.

[0067] The results of the temperature-induced dehydrogenation test of mill-LAH are as follows: Figure 7 As shown, the initial hydrogen release temperature of the mill-LAH is 115℃, and the hydrogen release amount is 7.45wt.% when the temperature is raised to 300℃, with a hydrogen release rate of 71.0% of the theoretical value.

[0068] By comparing Comparative Example 1 with Example 1, it can be seen that adding 3DOM-FO as a catalyst reduces the initial hydrogen desorption temperature of LAH from 115°C to 75°C and increases the hydrogen desorption rate from 71.0% to 73.94%.

[0069] To further demonstrate the effect of Fe on the hydrogen desorption performance of lithium aluminum hydride in 3DOM-FO, Comparative Example 2 is provided, in which Zr is used instead of Fe to prepare lithium aluminum hydride hydrogen storage material with added 3DOM-ZO / LAH.

[0070] Comparative Example 2

[0071] A method for preparing an ordered porous zirconia-doped lithium aluminum hydride hydrogen storage material is disclosed. Unless otherwise specified, the steps are the same as in Example 1, except that in step 2, Zr(NO3)4·5H2O is added instead of ferrous acetate. Therefore, the material obtained in step 2 is an ordered porous zirconia-doped lithium aluminum hydride hydrogen storage material, abbreviated as 3DOM-ZO. Finally, the material obtained in step 3 is an ordered porous zirconia-doped lithium aluminum hydride hydrogen storage material with a ZrO2 addition amount of 7 wt.%, abbreviated as 3DOM-ZO / LAH.

[0072] The XRD test results of 3DOM-ZO are as follows: Figure 2 As shown, the diffraction peaks of 3DOM-ZO are consistent with the characteristic peaks of ZrO2. The test results indicate that the composition of 3DOM-ZO is ZrO2.

[0073] The SEM test results of 3DOM-ZO are as follows: Figure 8 As shown, 3DOM-ZO is an ordered porous mesh structure. After the PMMA template is removed, its overall structure presents open pores.

[0074] The dehydrogenation performance test results of 3DOM-ZO / LAH are as follows: Figure 9 As shown, the initial hydrogen release temperature of 3DOM-ZO / LAH is 112℃; when the temperature is raised to 300℃, the hydrogen release amount is 7.15wt.%, and the hydrogen release rate is 73.22%.

[0075] Comparing Comparative Example 2 with Example 1, it can be seen that the initial hydrogen desorption temperature is 37°C lower with the addition of 3DOM-FO than with the addition of 3DOM-ZO.

[0076] To further demonstrate the effect of 3DOM-FO on the hydrogen desorption performance of lithium aluminum hydride, Comparative Example 3 is provided, in which lithium aluminum hydride hydrogen storage material with PMMA / LAH is prepared without 3DOM-FO.

[0077] Comparative Example 3

[0078] A method for preparing PMMA-doped lithium aluminum hydride hydrogen storage material is provided. The steps not specifically described are the same as those in Example 1, except that step 2 is omitted. In step 3, the PMMA obtained in step 1 is directly added to replace 3DOM-FO. The final material obtained in step 3 is an ordered polymethyl methacrylate microsphere-doped lithium aluminum hydride hydrogen storage material with a PMMA addition amount of 7 wt.%, abbreviated as PMMA / LAH.

[0079] The dehydrogenation performance test results of PMMA / LAH are as follows: Figure 10 As shown, the initial hydrogen release temperature of PMMA / LAH is 101℃; when the temperature is raised to 300℃, the hydrogen release amount is 6.94 wt.%, and the hydrogen release rate is 71.07%.

[0080] By comparing Comparative Example 3 with Comparative Example 2, it can be seen that the initial hydrogen release temperature of adding PMMA is lower than that of adding 3DOM-ZO. In other words, the introduction of Zr has a negative effect on the initial hydrogen release temperature.

[0081] Further comparison of Comparative Example 3 with Example 1 shows that the addition of 3DOM-FO is far superior to the addition of PMMA in terms of both initial hydrogen release temperature and hydrogen release rate.

[0082] To demonstrate the effect of the ferric oxide preparation method, i.e. the ordered porous network structure, on the hydrogen desorption performance of lithium aluminum hydride, Comparative Example 4 is provided, in which conventional ferric oxide-doped lithium aluminum hydride hydrogen storage material was prepared.

[0083] Comparative Example 4

[0084] A method for preparing a conventional ferric oxide-doped lithium aluminum hydride hydrogen storage material is described. The steps unless otherwise specified are the same as in Example 1, except that steps 1 and 2 are omitted. In step 3, commercially available Fe2O3 is added instead of 3DOM-FO. The final material obtained in step 3 is a conventional ferric oxide-doped lithium aluminum hydride hydrogen storage material with an Fe2O3 addition amount of 7 wt.%, abbreviated as C-FO / LAH.

[0085] The dehydrogenation performance test results of C-FO / LAH are as follows: Figure 11 As shown, the initial hydrogen release temperature of C-FO / LAH is 97℃; when the temperature is raised to 300℃, the hydrogen release amount is 7.18wt.%, and the hydrogen release rate is 73.53%.

[0086] Comparing Comparative Example 4 with Example 1, it can be seen that the addition of 3DOM-FO is far superior to the addition of conventional Fe2O3 in terms of both initial hydrogen release temperature and hydrogen release rate. This proves that adjusting the microstructure of conventional Fe2O3 into an ordered porous network structure through steps 1 and 2 can increase the specific surface area of ​​the material, shorten the H diffusion path, and significantly improve the hydrogen storage performance.

[0087] To demonstrate the effect of the amount of 3DOM-FO added on the hydrogen desorption performance of lithium aluminum hydride, Examples 2 and 3 are provided, in which ordered porous network iron oxide-doped lithium aluminum hydride hydrogen storage materials are prepared with 3 wt.% and 10 wt.% of 3DOM-FO added, respectively.

[0088] Example 2

[0089] A method for preparing an ordered porous network iron oxide-doped lithium aluminum hydride hydrogen storage material with an addition amount of 3wt.% of 3DOM-FO. The steps unless otherwise specified are the same as in Example 1, except that in step 3, the addition amount of 3DOM-FO is 3wt.%, specifically 0.0090g of 3DOM-FO and 0.2910g of LAH. The final material obtained in step 3 is an ordered porous network iron oxide-doped lithium aluminum hydride hydrogen storage material with an addition amount of 3wt.% of 3DOM-FO, abbreviated as 3DOM-FO / LAH-3.

[0090] The dehydrogenation performance test results of 3DOM-FO / LAH-3 are as follows: Figure 6 As shown, the initial hydrogen release temperature of 3DOM-FO / LAH-3 is 84℃; when the temperature is raised to 300℃, the hydrogen release amount is 7.35wt.%, and the hydrogen release rate is 72.16%.

[0091] Example 3

[0092] A method for preparing an ordered porous network iron oxide-doped lithium aluminum hydride hydrogen storage material with an addition amount of 10 wt.% of 3DOM-FO. The steps unless otherwise specified are the same as in Example 1, except that in step 3, the addition amount of 3DOM-FO is 10 wt.%, specifically 0.0300 g of 3DOM-FO and 0.2700 g of LAH. The final material obtained in step 3 is an ordered porous network iron oxide-doped lithium aluminum hydride hydrogen storage material with an addition amount of 10 wt.% of 3DOM-FO, abbreviated as 3DOM-FO / LAH-10.

[0093] The dehydrogenation performance test results of 3DOM-FO / LAH-10 are as follows: Figure 6 As shown, the initial hydrogen release temperature of 3DOM-FO / LAH-10 is 65℃; when the temperature is raised to 300℃, the hydrogen release amount is 6.83wt.%, and the hydrogen release rate is 72.28%.

[0094] Comparing Example 2 with Example 1, it can be seen that although the total hydrogen release in Example 2 is higher than that in Example 1, the initial hydrogen release temperature is higher. The reason is that the contact area between 3DOM-FO and LAH is lower in Example 2, resulting in a slower hydrogen release rate, which does not meet the application requirements.

[0095] Comparing Example 3 with Example 1, it can be seen that although the initial hydrogen release temperature of Example 3 is lower, the total hydrogen release is lower. The reason is that the doping amount of 3DOM-FO in Example 3 is higher and the LAH content is reduced, which does not meet the application requirements.

Claims

1. A method for preparing an ordered porous network iron oxide-doped lithium aluminum hydride hydrogen storage material, characterized in that... Includes the following steps: Step 1: Preparation of polymethyl methacrylate (PMMA). Methyl methacrylate and potassium persulfate are mixed in a specific ratio, with potassium persulfate acting as an initiator. First, potassium persulfate is placed in deionized water to obtain solution A. Then, under specific conditions, methyl methacrylate is placed in solution A and stirred to react. After the reaction is complete, the mixture is filtered and dried. Finally, the resulting product is ground under specific conditions to obtain polymethyl methacrylate, abbreviated as PMMA. Step 2, Preparation of ordered porous network iron oxide: PMMA obtained in Step 1, ferrous acetate, citric acid monohydrate, and F127 are mixed in a specific ratio. First, F127 is placed in a 40% ethanol aqueous solution to obtain solution A. Then, ferrous acetate and citric acid monohydrate are placed in solution A and magnetically stirred under certain conditions to obtain solution B. Afterward, PMMA is dissolved in solution B and allowed to stand under certain conditions. After standing, the resulting product is dried under certain conditions. After drying, the resulting product is ground to obtain powder C. Finally, powder C is calcined under certain conditions to obtain ordered porous network iron oxide, abbreviated as 3DOM-FO. Step 3: Preparation of ordered porous network iron oxide doped lithium aluminum hydride hydrogen storage material. The 3DOM-FO obtained in step 2 and lithium aluminum hydride LAH are mixed in a certain mass ratio. Under certain conditions, the 3DOM-FO and LAH are ball-milled to obtain the ordered porous network iron oxide doped lithium aluminum hydride hydrogen storage material, abbreviated as 3DOM-FO / LAH.

2. The preparation method according to claim 1, characterized in that: In step 1, the ratio of methyl methacrylate to potassium persulfate is 1 L: 20 g; In step 1, the stirring reaction conditions are as follows: under argon atmosphere, the stirring speed is 80-90 rpm / min, the stirring temperature is 80 ℃, and the stirring time is 40-50 min. In step 1, the grinding conditions are as follows: grinding time is 1-2 hours.

3. The preparation method according to claim 1, characterized in that: In step 2, the ratio of PMMA, ferrous acetate, citric acid monohydrate, and F127 is 5 g: 0.01 mol: 0.01 mol: 1 g. In step 2, the stirring conditions for preparing solution B are: stirring time of 10-20 min; the standing conditions for solution B are: standing time of 4-5 h; and the drying conditions after standing are: drying temperature of 50-60 ℃ and drying time of 12-16 h. In step 2, the calcination conditions are: heating rate of 1-2 ℃ / min, calcination temperature of 450 ℃, and calcination time of 5 h.

4. The preparation method according to claim 1, characterized in that: In step 3, the mass ratio of 3DOM-FO to LAH is 0.075:1; In step 3, the ball milling conditions are as follows: under argon gas, the ball-to-material ratio is (180-200):1, the ball milling speed is (400-500) r / min, and the ball milling time is 1-2 h.

5. The preparation method according to claim 1, characterized in that: The obtained ordered porous network iron oxide doped with lithium aluminum hydride hydrogen storage material is prepared by ball milling a mixture of lithium aluminum hydride and ordered porous network iron oxide. The microstructure of the ordered porous network iron oxide is a layered ordered porous network morphology, and the surface pore diameter of the layered ordered porous network morphology is 200 nm. The ordered porous network iron oxide is prepared by calcining the precipitate formed by ferrous acetate being dried in a mixed solution of polymethyl methacrylate and ethanol. The amount of ordered porous network iron oxide added accounts for 3-10 wt.% of the total mass. For applications in hydrogen storage, when the catalyst addition is 3-10 wt.%, the initial hydrogen release temperature of the system is 65-84 ℃; when the temperature is raised to 300 ℃, the total hydrogen release is 6.83-7.35 wt.%, and the hydrogen release rate is 72.16-73.94%.

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