Preparation method of metal-catalyzed lithium borohydride composite hydrogen storage material and product thereof

Abstract

The application discloses a preparation method of a metal-catalyzed lithium borohydride composite hydrogen storage material, which comprises the following steps: mixing raw materials including lithium borohydride and a ferrocene salt, and performing ball milling to obtain the metal-catalyzed lithium borohydride composite hydrogen storage material; the ferrocene salt is selected from one or more of nickelocene, chromocene and manganocene. The preparation method disclosed by the application is simple and controllable, is suitable for large-scale industrial production, and more importantly, the prepared composite hydrogen storage material has the advantages of low hydrogen absorption and desorption temperature, good hydrogen absorption and desorption kinetics, high cycle stability and the like without reducing the high theoretical capacity of lithium borohydride.

Description

Technical Field

[0001] This invention relates to the technical field of hydrogen storage materials, and in particular to a method for preparing a metal-catalyzed lithium borohydride composite hydrogen storage material and its product. Background Technology

[0002] New energy technologies include solar energy, photovoltaic energy, and hydrogen energy, among others, with hydrogen energy holding great potential as a secondary energy source. Firstly, it is clean and efficient. The product of the hydrogen reaction is water, generating no pollutants, and the efficiency of converting hydrogen energy into electricity exceeds 50%, demonstrating high efficiency. Secondly, it can facilitate the interconversion between different forms of energy. Furthermore, hydrogen energy is a renewable energy source; it can be stored and transported, and wastewater and solar power can be used to produce hydrogen. Therefore, current energy research focuses on hydrogen energy. Hydrogen storage is one of the most crucial aspects restricting the development of hydrogen energy. Current hydrogen storage technologies include gaseous, solid-state, and liquid hydrogen storage. Solid-state hydrogen storage has advantages such as high volumetric hydrogen storage density, convenient storage and transportation, and good safety, thus being considered the most promising hydrogen storage method. Solid-state hydrogen storage materials mainly include alloy hydrogen storage materials, porous hydrogen storage materials, carbon materials, and coordination hydride hydrogen storage materials. Among these, lithium borohydride, a coordination hydride hydrogen storage material, has received widespread attention due to its high mass hydrogen storage density of 18.5 wt%. However, lithium borohydride has limitations due to its BH4 content. - Its high stability requires a relatively high temperature to release hydrogen, with an initial hydrogen release temperature of approximately 280°C, and its hydrogen absorption and desorption kinetics and cycle stability are relatively poor.

[0003] Common modification methods include nano-sizing, constructing unstable composite systems, and catalyst doping. Nano-sized borohydride particles, due to their high specific surface area, short hydrogen diffusion paths, and numerous grain boundaries, can effectively improve the hydrogen absorption and desorption kinetics of borohydride systems. However, borohydride particles easily aggregate and grow during subsequent high-temperature cycling, leading to a decrease in the modification effect. Constructing unstable systems, such as the 2LiBH4-MgH2 system, results in a decrease in overall hydrogen desorption capacity due to the incorporation of a large number of low-capacity hydrides. Furthermore, further improvement in hydrogen storage performance requires the use of other modification methods, making the preparation process relatively complex. Catalyst modification can provide more active sites for hydrogen absorption and desorption reactions, thereby accelerating the reaction. Doping is generally carried out through ball milling, enabling large-scale preparation. Catalysts are diverse, mainly including transition metals, alloys, and their various compounds. Some metals react with borohydrides to obtain relatively low hydrogen desorption temperatures and fast hydrogen desorption kinetics, and the hydrogen desorption or absorption products serve as effective catalysts for subsequent cycles.

[0004] As reported in the literature (Improved Dehydrogenation and Rehydrogenation Properties of LiBH4 by Nanosized Ni Addition, Materials Transactions. 55(2014): 1134-1137.), the addition of metallic Ni improves the hydrogen dehydrogenation performance of LiBH4. Adding 25 wt% Ni can reduce the peak dehydrogenation temperature from 746 K to 696 K. However, at a temperature of 673 K, the system only releases 2.8 wt% hydrogen, and the thermodynamic stability is still too high.

[0005] The morphology and doping method of the catalyst are important factors affecting the catalytic effect. One study (Z. Li, S. Wang, M. Gao, K. Xian, Y. Shen, Y. Yang, P. Gao, W. Sun, Y. Liu and H. Pan, Catalyzed LiBH4 Hydrogen Storage System with In Situ Introduced Li3BO3 and V for Enhanced Dehydrogenation and Hydrogenation Kinetics as Well as High Cycling Stability, Acs Applied Energy Materials. 5(2022): 1226-1234) introduced Li3BO3 and V as catalysts in situ through ball milling and heat treatment. This resulted in LiBH4 releasing 5.8 wt% hydrogen after holding at 350℃ for 90 min. However, after only five cycles, the hydrogen release capacity decreased from 6.3 wt% to 5.6 wt%.

[0006] It is evident that the catalyst modification methods disclosed in the existing technology are difficult to achieve the goals of reducing the hydrogen desorption temperature of lithium borohydride, improving the hydrogen desorption reaction kinetics and cycle stability without reducing its high theoretical capacity. Summary of the Invention

[0007] To address the aforementioned problems in the existing technology, this invention discloses a method for preparing a metal-catalyzed lithium borohydride composite hydrogen storage material. This method is simple, controllable, and suitable for large-scale industrial production. More importantly, the prepared composite hydrogen storage material possesses advantages such as low hydrogen absorption / desorption temperature, good hydrogen desorption kinetics, and high cycle stability without reducing the high theoretical capacity of lithium borohydride.

[0008] The specific technical solution is as follows:

[0009] A method for preparing a metal-catalyzed lithium borohydride composite hydrogen storage material involves mixing and ball-milling raw materials including lithium borohydride and dicerocene salt to obtain the metal-catalyzed lithium borohydride composite hydrogen storage material.

[0010] The diacetic salt is selected from one or more of nickel diacetic, chromium diacetic, and manganese diacetic.

[0011] This invention discloses a method for obtaining composite hydrogen storage materials by ball milling and blending dicerocene salts with lithium borohydride. Experiments have shown that the composite hydrogen storage material prepared by this method exhibits a hydrogen release capacity comparable to that of lithium borohydride alone at 500°C, but with lower initial and peak hydrogen release temperatures; it also has a lower apparent activation energy for hydrogen release, resulting in superior hydrogen release kinetics; and it demonstrates superior cycle stability, maintaining a hydrogen release of over 6.2 wt% H2 after ten cycles of hydrogen adsorption and desorption.

[0012] Preferably, the mass ratio of lithium borohydride to dicerocene is (40~80):(20~60); a more preferred mass ratio is (50~60):(40~50).

[0013] Preferably, the diacetic salt is selected from nickel diaceticate and / or chromium diaceticate; experiments have shown that the composite hydrogen storage material system prepared using the preferred diacetic salt has a higher primary hydrogen release capacity.

[0014] Further preferably, the diacetic salt is selected from nickel diaceticate and chromium diaceticate. The composite hydrogen storage material system prepared using the further preferred diacetic salt has a higher primary hydrogen desorption capacity, a lower hydrogen desorption temperature, and superior hydrogen desorption kinetics.

[0015] Experiments also revealed the unexpected formation of carbon nanotubes in a composite hydrogen storage material system prepared by ball milling lithium borohydride, nickel dicerocene, and chromium dicerocene. The presence of lithium borohydride unexpectedly catalyzed the in-situ formation of carbon nanotubes from nickel dicerocene (no carbon nanotube formation was observed after ball milling of individual dicerocene salts, while the pyrolysis of dicerocene salts to generate carbon nanotubes requires a temperature of at least 900°C). Utilizing the advantages of carbon nanotubes in facilitating the dispersion of nano-metals (Ni, Cr), and their excellent thermal conductivity promoting rapid and uniform heat transfer during hydrogen absorption and desorption in the composite hydrogen storage material, combined with the catalytic effect of the metals, the synergistic effect of both can simultaneously reduce the hydrogen desorption temperature of lithium borohydride, improve hydrogen desorption kinetics, and enhance cycle stability without reducing the high theoretical capacity of lithium borohydride.

[0016] Further optimization:

[0017] The mass ratio of nickel dicene to chromium dicene is 1:0.6~1.5.

[0018] Better:

[0019] The mass ratio of lithium borohydride, nickel dicerocene, and chromium dicerocene is 55:20:25. Experiments have shown that the composite hydrogen storage material system prepared with this mass ratio has higher cycle stability.

[0020] Preferred:

[0021] The ball mill is operated at a speed of 300-500 rpm, with a ball-to-material ratio of 120-180:1, a time of 1-4 hours, and the atmosphere is selected from nitrogen or an inert gas.

[0022] The present invention also discloses a metal-catalyzed lithium borohydride composite hydrogen storage material prepared according to the above method.

[0023] Tests showed that the metal-catalyzed lithium borohydride composite hydrogen storage material has an initial hydrogen release temperature of 70~100℃, a peak hydrogen release temperature of 320~360℃, and a hydrogen release amount of not less than 9.3wt% at 500℃.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] This invention discloses a method for preparing a metal-catalyzed lithium borohydride composite hydrogen storage material. The raw materials are simple and readily available, and the process involves only one ball milling step, which is simple, controllable, and suitable for large-scale industrial production.

[0026] The composite hydrogen storage material system prepared by this invention has a lower initial hydrogen desorption temperature and peak hydrogen desorption temperature without reducing the high theoretical capacity of lithium borohydride; it also has a lower apparent activation energy for hydrogen desorption, thus exhibiting superior hydrogen desorption kinetics; and it also has superior cycle stability, with the hydrogen desorption amount still reaching more than 6.2 wt% H2 after ten cycles of hydrogen absorption and desorption. Attached Figure Description

[0027] Figure 1 XPS spectra of the composite hydrogen storage material prepared in Example 1 are shown, and XPS spectra of the raw materials are given for comparison.

[0028] Figure 2 SEM images of the composite hydrogen storage material prepared in Example 1 and intensity maps of different elements when line scanned along the direction of the arrow in the images;

[0029] Figure 3 TEM image of the composite hydrogen storage material prepared in Example 1;

[0030] Figure 4 The XRD patterns of the products prepared in Example 1 and Comparative Examples 2-4 are shown below.

[0031] Figure 5The isothermal hydrogen desorption curves of the composite hydrogen storage material prepared in Example 1 at 300℃, 350℃, and 400℃ are given for comparison with the hydrogen desorption curve of the ball-milled lithium borohydride in Comparative Example 1.

[0032] Figure 6 The image shows the Kissinger fitting curve of the composite hydrogen storage material prepared in Example 1. The attached figure in the upper right corner shows its TPD-MS curves at different heating rates.

[0033] Figure 7 Isothermal hydrogen release curve (a) and hydrogen release data (b) of ten hydrogen release cycles are given for the composite hydrogen storage material prepared in Example 1. Hydrogen release data of ball-milled lithium borohydride in Comparative Example 1 are also given.

[0034] Figure 8 XPS spectra of the 2p orbitals of Cr (a) and Ni (b) elements in the composite hydrogen storage material prepared in Example 1 after one hydrogen release, one hydrogen absorption, and ten hydrogen releases are shown, and the XPS spectra before hydrogen release are given for comparison.

[0035] Figure 9 The XRD patterns of the composite hydrogen storage material prepared in Example 1 after one hydrogen release, one hydrogen absorption, and ten hydrogen releases are shown, and the XRD pattern before hydrogen release is given for comparison.

[0036] Figure 10 The images shown are TEM images of the composite hydrogen storage material prepared in Example 1 after a single hydrogen release, with the insets being FFT images of regions 1 and 2, respectively.

[0037] Figure 11 The images shown are TEM images of the composite hydrogen storage material prepared in Example 1 after a single hydrogen absorption. The insets are FFT images of regions 3 and 4, respectively.

[0038] Figure 12 The figures show the temperature-dependent hydrogen desorption curves of the products prepared in Examples 1-5, with the temperature-dependent hydrogen desorption curve of LiBH4 prepared in Comparative Example 1 shown for comparison.

[0039] Figure 13 The figures show the temperature-dependent secondary hydrogen desorption curves of the products prepared in Examples 1-5, with the temperature-dependent secondary hydrogen desorption curve of LiBH4 prepared in Comparative Example 1 shown for comparison.

[0040] Figure 14 The TPD-MS curves of the composite hydrogen storage materials prepared in Examples 1 and 6-7 are shown, and LiBH4 prepared in Comparative Example 1 is given as a comparison.

[0041] Figure 15The figures show the hydrogen release curves (a) and hydrogen absorption curves (b) of the composite hydrogen storage materials prepared in Examples 1 and 6-7, respectively, with LiBH4 prepared in Comparative Example 1 shown as a comparison.

[0042] Figure 16 The figures show the temperature-dependent primary hydrogen release curves (a) and temperature-dependent secondary hydrogen release curves (b) of the composite hydrogen storage materials prepared in Examples 7-10, respectively. The figures also show the LiBH4 prepared in Comparative Example 1 as a comparison.

[0043] Figure 17 The first hydrogen release curve (a) and the second hydrogen release curve (b) of the composite hydrogen storage materials prepared in Examples 4 and 11, respectively, are shown. Detailed Implementation

[0044] The specific implementation methods of the present invention will be further described below with reference to examples. It should be noted that the specific implementation methods described herein are only for illustration and explanation of the present invention and are not intended to limit the scope of protection of the present invention.

[0045] Unless otherwise specified, the operating methods in the following examples are generally performed under conventional conditions or as recommended by the manufacturer.

[0046] Example 1

[0047] 55wt% LiBH4, 25wt% chromium dicerocene (CrCp2), and 20wt% nickel dicerocene (NiCp2) were simultaneously added to a ball mill jar at a ball-to-material ratio of 150:1. The ball milling atmosphere was argon, and the mixture was ball-milled at 500 rpm for 2 hours to obtain a composite hydrogen storage material. The product was designated as LiBH4-25CrCp220NiCp2.

[0048] Figure 1 The XPS spectra of the product and raw material CrCp2 prepared in this embodiment are shown in (a). As can be confirmed by (a), 584.3 eV and 575.1 eV correspond to the 2p1 / 2–2p3 / 2 spin orbitals of CrCp2, indicating that chromium dicene did not decompose during ball milling and still exists in the form of chromium dicene. In (b), the two pairs of peaks at 869.4 / 852.2 eV and 872.4 / 854.4 eV correspond to the binding energy positions of elemental Ni and NiCp2, respectively, indicating that nickel dicene partially decomposes into elemental nickel during ball milling.

[0049] Figure 2The SEM images (a) of the product prepared in this embodiment and the intensity maps (b) of different elements when line scanning is performed along the direction of the arrow in the SEM image are shown. Observing the image (a), it can be seen that the LiBH4 particles are in the size of micrometers to submicrometers, and nanowires with diameters of several to tens of nanometers are entangled between the LiBH4 particles. As can be seen from the image (b), only the C signal fluctuates significantly with the change of line scanning distance, indicating that the nanowires are carbon materials.

[0050] Figure 3 The TEM image of the product prepared in this embodiment shows that the carbonaceous material is carbon nanotubes with a diameter of about 5 nm.

[0051] Combination Figures 1-3 It can be confirmed that carbon nanotubes were generated in situ in the ball milling product and wrapped between the borohydride particles. The ball milling product also contains undecomposed CrCp2, decomposed nickel metal, and a small amount of undecomposed NiCp2.

[0052] Comparative Example 1

[0053] LiBH4 was added to the ball mill jar at a ball-to-material ratio of 150:1. The ball milling atmosphere was argon, and the ball milling was carried out at 500 rpm for 2 hours.

[0054] Comparative Example 2

[0055] Chromium dicene (CrCp2) was added to the ball mill jar at a ball-to-material ratio of 150:1. The ball milling atmosphere was argon, and the ball milling was carried out at 500 rpm for 2 hours.

[0056] Comparative Example 3

[0057] Nickel dicene (NiCp2) was added to the ball mill jar at a ball-to-material ratio of 150:1. The ball milling atmosphere was argon, and the mixture was milled at 500 rpm for 2 hours.

[0058] Comparative Example 4

[0059] The mixture was prepared by adding 55wt% LiBH4, 25wt% chromium dichromate (CrCp2), and 20wt% nickel dicerocene (NiCp2) to a mortar in an argon atmosphere in a glove box and grinding by hand for 15 minutes.

[0060] Figure 4 The XRD patterns are of the products prepared in Example 1 and Comparative Examples 2-4, respectively.

[0061] (a) The figure shows the XRD patterns of the product prepared in Example 1 and the product from which LiBH4 was removed. In this example, only the diffraction peaks of LiBH4 are visible in the XRD pattern of the product prepared in this example. To eliminate the interference of LiBH4, we further stirred the ball-milled LiBH4-25CrCp220NiCp2 with tetrahydrofuran for 2 hours and then filtered to obtain a ball-milled LiBH4-25CrCp220NiCp2 sample from which LiBH4 was removed. Its XRD pattern shows that the dicenecrolein salt did not have obvious diffraction peaks after ball milling and was either amorphous or had very small particles. (b) The figure shows the XRD patterns of the products prepared in Comparative Examples 2 to 4. From Figure (b), it can be seen that the diffraction peaks of the CrCp2 and NiCp2 samples before and after ball milling are almost unchanged, indicating that NiCp2 does not decompose during ball milling alone. The peaks of CrCp2 are very weak and it is basically amorphous. Therefore, it is not possible to determine its decomposition from the XRD pattern alone, but combined with Figure 1 XPS characterization before and after ball milling confirmed that CrCp2 did not decompose. Manually milled LiBH4-25CrCp220NiCp2 showed diffraction peaks for both LiBH4 and NiCp2, indicating that manually milled LiBH4-25CrCp220NiCp2 also does not decompose. In contrast, ball-milled LiBH4-25CrCp220NiCp2 only showed diffraction peaks for LiBH4, further indicating that NiCp2 decomposed during ball milling with LiBH4 and CrCp2. This conclusion is consistent with... Figure 1 The conclusions are consistent with those in the text.

[0062] Performance testing:

[0063] 1. The hydrogen release performance of the material at different temperatures was tested using the volumetric hydrogen release method. The material was heated to 300℃, 350℃, and 400℃ at a heating rate of 10℃ / min under a hydrogen pressure of 10 MPa, and then subjected to a vacuum of 1×10⁻⁶. -3 Keep warm under Torr conditions for 50 minutes.

[0064] Figure 5 The isothermal hydrogen desorption curves of the composite hydrogen storage material prepared in this embodiment at 300℃, 350℃, and 400℃ are shown, and the hydrogen desorption curve of the ball-milled lithium borohydride in Comparative Example 1 is given for comparison. Figure 5As shown, LiBH4-25CrCp220NiCp2 released 3.4 wt% H2 and 7.4 wt% H2 after being held at 300℃ and 350℃ for 50 minutes, respectively. In contrast, LiBH4 released only 1.0 wt% H2 and 1.6 wt% H2 under the same conditions. LiBH4-25CrCp220NiCp2 released 9.3 wt% H2 after being held at 400℃ for only 20 minutes, while LiBH4 released only 2.7 wt% H2 after 50 minutes. These data indicate that the composite hydrogen storage material prepared in this embodiment exhibits superior hydrogen desorption kinetics compared to LiBH4 alone.

[0065] 2. Mass spectrometry curves were obtained using a TPD-MS testing system, and the apparent activation energy of hydrogen desorption of the test material was calculated based on the Kissinger equation. High-purity argon was used as the carrier gas at a flow rate of 20 mL / min. The test material was heated from 30℃ to 500℃ at different heating rates, and TPD-MS curves at different heating rates were obtained; and the Kissinger equation was used to calculate the apparent activation energy of hydrogen desorption of the test material. ,in For the heating rate, T p Let R be the peak hydrogen release temperature at this heating rate, and R be the ideal gas constant, expressed as ln(β / T). p 2 ) is the ordinate, 1 / T p Plot the x-axis and perform a linear fit; the slope of the fitted line is -E. a / R, from which the apparent activation energy of hydrogen expulsion of the material under test can be calculated.

[0066] Figure 6 The image shows the Kissinger fitting curve for LiBH4-25CrCp220NiCp2. The attached figure in the upper right corner shows the TPD-MS curves of LiBH4-25CrCp220NiCp2 at different heating rates. The slope of the fitted straight line is -E. a / R, from which the hydrogen desorption activation energy of the composite hydrogen storage material system prepared in this embodiment can be calculated to be 106.4 kJ mol. -1 Compared to the isolated LiBH4 prepared in Comparative Example 1 (with a hydrogen desorption activation energy of 176.4 kJ / mol), -1 The composite hydrogen storage material prepared in this embodiment has a lower hydrogen desorption activation energy, and therefore has significantly better hydrogen desorption kinetics than LiBH4.

[0067] 3. The cycle performance of the hydrogen storage material was tested using the volumetric hydrogen release method. The hydrogen release process was as follows: under a hydrogen pressure of 10 MPa, the temperature was heated to 400 °C at a heating rate of 10 °C / min, under vacuum conditions (initial vacuum degree of 1 × 10⁻⁶). -3The isothermal hydrogen release test was conducted by holding the temperature at Torr for 4 hours. The hydrogen absorption process was as follows: the temperature was increased to 450℃ at a heating rate of 10℃ / min under a hydrogen pressure of 10 MPa, and held at this temperature for 2 hours to conduct isothermal hydrogen absorption.

[0068] Figure 7 Figure (a) shows the isothermal hydrogen release curve of the composite hydrogen storage material prepared in this embodiment; Figure (b) shows the hydrogen release data in ten hydrogen release cycles, and the specific data are listed in Table 1 below.

[0069] Table 1

[0070]

[0071] contrast Figure 7 As shown in Table 1, the composite hydrogen storage material prepared in this embodiment still has a hydrogen release capacity of 6.2 wt% H2 after 10 cycles, while the capacity of single LiBH4 is only 3 wt% H2 after 5 cycles. This indicates that the composite hydrogen storage material prepared in this embodiment has significantly better cycle stability than single LiBH4.

[0072] Figure 8 XPS spectra of Cr (a) and Ni (b) in the composite hydrogen storage material prepared in this embodiment after one hydrogen release, one hydrogen absorption, and ten hydrogen releases are shown, with the XPS spectra before hydrogen release provided for comparison. Observation revealed that after one hydrogen release, the spin orbital peaks of Cr at 583.8 eV and 574.7 eV correspond to elemental Cr, while the spin orbital peaks corresponding to nickel dicene disappear, leaving only the orbital peaks corresponding to elemental Ni. This indicates that after one hydrogen release, both chromium dicene and nickel dicene completely decompose into elemental metals. After one hydrogen absorption, the spin orbital peaks of Cr at 583.4 eV and 574.3 eV in the XPS spectrum correspond to CrB2, consistent with the samples after ten hydrogen releases. After one hydrogen absorption, the Ni 2p orbitals at 869.7 eV and 852.5 eV correspond to the 2p1 / 2-2p3 / 2 spin orbitals of Ni2B, consistent with the orbital peak positions after ten hydrogen releases. Therefore, it can be concluded that after one hydrogen absorption, metallic Cr and Ni are converted into CrB2 and Ni2B respectively and remain stable in subsequent cycles.

[0073] Figure 9 XRD patterns of the composite hydrogen storage material prepared in this embodiment after one hydrogen desorption, one hydrogen absorption, and ten hydrogen desorptions are shown, with the XRD pattern before hydrogen desorption also provided for comparison. Observations revealed that the absence of diffraction peaks in the sample after one hydrogen desorption suggests that the desorption product is amorphous or small in size. The presence of LiBH4 after one hydrogen absorption indicates good reversibility of the system. Furthermore, diffraction peaks for CrB2 and Ni2B were observed after one hydrogen absorption, and the boride remained stable after ten hydrogen desorptions. These conclusions are consistent with... Figure 8 This aligns with the conclusions given in the text.

[0074] Figure 10 The images show TEM images of the composite hydrogen storage material prepared in this embodiment after a single hydrogen release. The insets are FFT images of regions 1 and 2, respectively. The images show 4–8 nm nanoparticles distributed in the matrix. The interplanar spacing of region 1 is 0.24 nm, corresponding to the (111) crystal plane of Ni; the interplanar spacing of region 2 is 0.26 nm, corresponding to the (111) crystal plane of Cr. This further confirms the presence of nano-metallic Cr and Ni elements after hydrogen release.

[0075] Figure 11 The images shown are TEM images of the composite hydrogen storage material prepared in this embodiment after one hydrogen absorption. The insets are FFT images of regions 3 and 4, respectively. The nanoparticles that appear after one hydrogen absorption are relatively large, but still maintain a size of 5-10 nm. The interplanar spacing of region 3 is 0.31 nm, corresponding to the (001) crystal plane of CrB2; the interplanar spacing of region 4 is 0.21 nm, corresponding to the (002) crystal plane of Ni2B.

[0076] Figures 10-11 The crystal structure confirmed in the middle and Figures 8-9 The conclusions are completely consistent with those in the previous article. The ultrafine particle size of Cr / Ni and CrB2 / Ni2B and their uniform dispersion in the hydrogen storage material matrix effectively promote the improvement of dehydrogenation / hydrogenation kinetics. In addition, as shown in the figure, the close contact between Cr / Ni and CrB2 / Ni2B particles may also play a synergistic catalytic role in the dehydrogenation / hydrogenation kinetics of LiBH4.

[0077] Example 2

[0078] The preparation process is basically the same as in Example 1, except that the mass ratio of LiBH4, CrCp2 and NiCp2 is 60:20:20, and the product is denoted as LiBH4-20CrCp220NiCp2.

[0079] Example 3

[0080] The preparation process is basically the same as in Example 1, except that the mass ratio of LiBH4, CrCp2 and NiCp2 is 50:30:20, and the product is denoted as LiBH4-30CrCp220NiCp2.

[0081] Example 4

[0082] The preparation process is basically the same as in Example 1, except that the mass ratio of LiBH4, CrCp2 and NiCp2 is 55:20:25, and the product is denoted as LiBH4-20CrCp225NiCp2.

[0083] Example 5

[0084] The preparation process is basically the same as in Example 1, except that the mass ratio of LiBH4, CrCp2 and NiCp2 is 50:20:30, and the product is denoted as LiBH4-20CrCp230NiCp2.

[0085] The hydrogen desorption curves of the products prepared in Examples 1-5 were tested, and the hydrogen desorption curves were tested again with temperature changes. The testing process was as follows:

[0086] The hydrogen release performance of the material was tested using a volumetric hydrogen release method with a single temperature-dependent hydrogen release, at an initial vacuum of 1×10⁻⁶. -3 Hydrogen release under Torr conditions involves heating to 500°C at a heating rate of 2°C / min. Hydrogen absorption conditions involve heating to 500°C at a hydrogen pressure of 10 MPa at a heating rate of 2°C / min and holding at that temperature for 2 hours. The secondary and primary hydrogen release procedures are set identically.

[0087] Figure 12 To illustrate the single-temperature hydrogen desorption curve obtained from the test, the figure also shows the single-temperature hydrogen desorption curve of LiBH4 prepared in Comparative Example 1 for comparison. Figure 13 To illustrate the temperature-dependent secondary hydrogen desorption curves obtained from the tests, a separate temperature-dependent secondary hydrogen desorption curve for LiBH4 is also shown in the figure for comparison. (Observation) Figure 12 Compared with LiBH4 alone, the initial hydrogen desorption temperature and the main hydrogen desorption temperature of the composite hydrogen storage materials prepared in each embodiment were significantly reduced; although Figure 12 Among them, the composite hydrogen storage material prepared in Example 2 has the highest hydrogen release capacity (10.8 wt%), slightly higher than that of Example 1 (9.9 wt%), but combined with Figure 13 The composite hydrogen storage material prepared in Example 1 has a higher secondary hydrogen release capacity and the lowest hydrogen release temperature, thus making it the optimal composite hydrogen storage material system.

[0088] Example 6

[0089] 55wt% LiBH4 and 45wt% chromium dicene (CrCp2) were simultaneously added to a ball mill jar at a ball-to-material ratio of 150:1. The ball milling atmosphere was argon, and the mixture was ball-milled at 500 rpm for 2 hours to obtain a composite hydrogen storage material. The product was denoted as LiBH4-45CrCp2.

[0090] Example 7

[0091] 55wt% LiBH4 and 45wt% nickel dicerocene (NiCp2) were simultaneously added to a ball mill jar at a ball-to-material ratio of 150:1. The ball milling atmosphere was argon, and the mixture was ball-milled at 500 rpm for 2 hours to obtain a composite hydrogen storage material. The product was denoted as LiBH4-45NiCp2.

[0092] SEM testing showed that carbon nanotubes were only produced in situ after ball milling when the selected dicene salt contained NiCp2 (Examples 1 and 7); however, when the dicene salt did not contain NiCp2 (Example 6), carbon nanotubes were not produced in situ even after subsequent heating to release hydrogen and decompose the dicene salt.

[0093] The hydrogen intensity released by the composite hydrogen storage materials prepared in Examples 1 and 6-7 when heated to different temperatures was tested using a TPD-MS testing system. High-purity argon was used as the carrier gas, with a flow rate of 20 mL / min. The temperature was increased from 30℃ to 500℃ at a heating rate of 2℃ / min.

[0094] Figure 14 The TPD-MS curves of the composite hydrogen storage materials prepared in Examples 1 and 6-7 are shown, with LiBH4 prepared in Comparative Example 1 provided for comparison. Observation Figure 14 Compared with LiBH4 alone, the hydrogen desorption peak temperature of the composite hydrogen storage materials prepared in each embodiment is significantly reduced, with the composite hydrogen storage material prepared in Example 1 having the lowest temperature.

[0095] Figure 15 The figures show the temperature-dependent hydrogen release curve (a) and temperature-dependent hydrogen absorption curve (b) of the composite hydrogen storage materials prepared in Examples 1 and 6-7, respectively (the conditions for single hydrogen absorption were heating from room temperature to 500℃ at a heating rate of 2℃ / min under a hydrogen pressure of 10MPa). LiBH4 prepared in Comparative Example 1 is also shown in the figures for comparison. (Observation) Figure 15 (a) It can be seen that when heated to 360℃, the hydrogen release amounts of LiBH4-25CrCp220NiCp2, LiBH4-45CrCp2, and LiBH4-45NiCp2 are 8.1wt%, 7.5wt%, and 7.5wt%, respectively. Even when heated to 500℃, the hydrogen release amount of LiBH4-25CrCp220NiCp2 is the highest among the three. Figure 15 (b) In this embodiment, LiBH4-25CrCp220NiCp2 begins to absorb hydrogen from 142℃, and its hydrogen absorption capacity reaches 9.8wt% when heated to 500℃. At 400℃, the hydrogen absorption capacities of LiBH4-25CrCp220NiCp2, LiBH4-45CrCp2, and LiBH4-45NiCp2 are 3.2wt%, 1.9wt%, and 0.9wt%, respectively. In summary, the hydrogen release and absorption performance of LiBH4-25CrCp220NiCp2 is superior to that of the other two embodiments. It is evident that lithium borohydride, CrCp2, and NiCp2 in the composite hydrogen storage material of this invention exhibit a synergistic effect, and its hydrogen storage performance is significantly higher than that of single lithium borohydride or two-component composite hydrogen storage materials.

[0096] Example 8

[0097] 80 wt% LiBH4 and 20 wt% nickel dicerocene (NiCp2) were simultaneously added to a ball mill jar at a ball-to-material ratio of 150:1. The ball milling atmosphere was argon, and the mixture was ball-milled at 500 rpm for 2 hours to obtain a composite hydrogen storage material. The product was denoted as LiBH4-20NiCp2.

[0098] Example 9

[0099] 80 wt% LiBH4 and 20 wt% manganese dicene (MnCp2) were simultaneously added to a ball mill jar at a ball-to-material ratio of 150:1. The ball milling atmosphere was argon, and the mixture was ball-milled at 500 rpm for 2 hours to obtain a composite hydrogen storage material. The product was denoted as LiBH4-20MnCp2.

[0100] Example 10

[0101] 60 wt% LiBH4, 20 wt% manganese diacene (MnCp2) and 20 wt% nickel diacene (NiCp2) were simultaneously added to a ball mill jar with a ball-to-material ratio of 150:1. The ball milling atmosphere was argon, and the mixture was ball milled at 500 rpm for 2 hours to obtain a composite hydrogen storage material. The product was designated as LiBH4-20MnCp220NiCp2.

[0102] Figure 16 Figure (a) shows the temperature-dependent primary hydrogen release curves (TLC) and secondary hydrogen release curves (B) of the composite hydrogen storage materials prepared in Examples 7-10, respectively. Observation of Figure (a) reveals that LiBH4-20NiCp2 exhibits the highest hydrogen release capacity, while LiBH4-45NiCp2 has the lowest hydrogen release temperature. Although the hydrogen release capacity of LiBH4-20MnCp220NiCp2 is slightly higher than that of LiBH4-45NiCp2, its primary hydrogen release temperature is significantly higher. Figure (b) shows that LiBH4-45NiCp2 has the lowest hydrogen release temperature. The hydrogen release capacities of LiBH4-20MnCp220NiCp2 and LiBH4-45NiCp2 are similar. Considering the performance of both hydrogen release cycles, LiBH4-45NiCp2 is significantly superior to LiBH4-20MnCp220NiCp2. Meanwhile... Figure 15 In the performance comparison, we have already concluded that the lithium borohydride, CrCp2, and NiCp2 three-component system is superior to the lithium borohydride, NiCp2 two-component system. Therefore, we believe that the lithium borohydride, CrCp2, and NiCp2 three-component system is superior to the LiBH4, MnCp2, and NiCp2 three-component system.

[0103] Example 11

[0104] 55 wt% LiBH4, 20 wt% chromium dicene (CrCp2), and 25 wt% carbon nanotubes (CNTs) were simultaneously added to a ball mill jar at a ball-to-material ratio of 150:1. The ball milling atmosphere was argon, and the mixture was ball-milled at 500 rpm for 2 hours to obtain a composite hydrogen storage material. The product was designated as LiBH4-20CrCp225CNT.

[0105] Figure 17 The figures (a) and (b) show the temperature-dependent primary hydrogen release curves (TDC) and secondary hydrogen release curves (BDC) of the composite hydrogen storage materials prepared in Examples 4 and 11, respectively. It was observed that the primary hydrogen release performance of LiBH4-20CrCp225NiCp2 was significantly better than that of LiBH4-20CrCp225CNT. Although the secondary hydrogen release temperature was slightly higher than that of the latter, the hydrogen release capacity was much higher. It can be inferred that the in-situ generation of carbon nanotubes in the lithium borohydride, CrCp2, and NiCp2 three-component system disclosed in Example 4 is more effective than the addition of carbon nanotubes in improving performance, especially reversibility.

[0106] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. The specific examples used above to illustrate the present invention are only for the purpose of helping to understand the present invention and are not intended to limit the present invention. Those skilled in the art to which this invention pertains can make several simple deductions, modifications, substitutions, or combinations based on the concept of the present invention. These deductions, modifications, substitutions, or combinations also fall within the scope of the claims of the present invention.

Claims

1. A method for preparing a metal-catalyzed lithium borohydride composite hydrogen storage material, comprising: mixing raw materials including lithium borohydride and a ferrocene salt to obtain the metal-catalyzed lithium borohydride composite hydrogen storage material by ball milling; wherein the ferrocene salt is selected from nickelocene and chromocene; the mass ratio of lithium borohydride to ferrocene salt is (40-80) : (20-60) ; and the mass ratio of nickelocene to chromocene is 1 : 0.6-1.

5. 2.The method according to claim 1, wherein the mass ratio of lithium borohydride to ferrocene salt is (50-60) : (40-50). 3.The method according to claim 1, wherein the mass ratio of lithium borohydride, nickelocene and chromocene is 55 : 20 :

25. 4.The method according to claim 1, wherein the ball milling is performed at a rotation speed of 300-500 rpm, a ball-to-material ratio of 120-180 : 1, for 1-4 h in an atmosphere selected from nitrogen or an inert gas. 5.A metal-catalyzed lithium borohydride composite hydrogen storage material prepared by the method according to any one of claims 1-4, having an initial hydrogen release temperature of 70-100 ℃, a peak hydrogen release temperature of 320-360 ℃, and a hydrogen release amount of no less than 9.3 wt% at 500 ℃. ​ ​ ​ ​ ​ ​ ​ 6. The metal-catalyzed lithium borohydride composite hydrogen storage material of claim 5, wherein, ​

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