High-performance hydroboron / magnesium-based composite hydrogen storage material as well as preparation method and application thereof

Abstract

The invention relates to a high-performance hydroboron / magnesium-based composite hydrogen storage material and a preparation method and application thereof, the high-performance hydroboron / magnesium-based composite hydrogen storage material mainly comprises LiBH4, MgH2 and TiVC powder mixture, and TiVC is a novel bimetallic MXene and is obtained by etching TiVAlC MAX with LiF and HCl. The composite material can release 9.3 wt% of hydrogen within 35 min at the temperature of 400 DEG C and can absorb hydrogen completely within 30 min, the hydrogen absorption / release time is shortened to be 1 / 6 of that of 2LiBH4 + MgH2, the capacity retention rate after fifteenth circulation is 96%, and therefore reference significance is provided for improving the vehicle-mounted hydrogen storage efficiency and the coupling energy storage efficiency with other new energy sources.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of hydrogen storage materials, and relates to a high-performance borohydride / magnesium-based composite hydrogen storage material and a preparation method and application thereof. BACKGROUND

[0002] The use of fossil energy has significantly improved the development process of human society, but the environmental pollution problems brought about by the combustion process of its energy release cannot be ignored. In addition, since the industrial revolution, fossil energy has been consumed at an unprecedented rate and is facing the predicament of depletion. Therefore, developing clean and efficient renewable new energy is the focus of work of various countries at present. Hydrogen energy is a clean and efficient energy and has the advantage of wide sources, and is expected to replace traditional fossil energy. However, the difficulties in hydrogen storage limit its large-scale use. At present, common hydrogen storage methods include: high-pressure gas tank hydrogen storage, low-temperature liquid hydrogen storage, organic liquid hydrogen storage and solid hydrogen storage. Among them, solid hydrogen storage has a relatively higher hydrogen storage capacity and is relatively safe and reliable, and has become a research hotspot in hydrogen storage. Researchers have carried out a large number of researches on metal hydrides, complex hydrides (metal borohydride, metal aluminum hydride and metal nitrogen hydride) and the like.

[0003] Metal borohydride is considered as a promising hydrogen storage material due to its high hydrogen storage capacity. Compared with other borohydrides, LiBH4 has a higher theoretical hydrogen storage capacity, with a hydrogen storage capacity of 18.5 wt% (weight percentage) and 121 g L −1 ( volume percentage). However, the decomposition temperature of LiBH4 is too high, and the hydrogen release rate is slow, which cannot meet the working conditions of hydrogen fuel cells. Moreover, the regeneration conditions of LiBH4 after hydrogen release are too harsh (600 °C, 35 MPa), resulting in a high use cost. Therefore, many modification methods have been proposed: catalytic modification, nano confinement, and composite system with other hydrogen storage materials. The introduction of catalysts can cause LiBH4 to be unstable, reduce its decomposition temperature and improve its kinetic performance. The construction of a composite system can significantly improve its reversibility.

[0004] Two-dimensional layered transition metal carbide MXene is a new material emerging in recent years, which has excellent performance in the fields of catalysis and energy storage, and is favored by a large number of researchers. Its special accordion structure can provide more active sites for hydrogen absorption and release reactions of hydrogen storage materials, and its large surface area can inhibit the agglomeration of the composite material and improve its cycle retention rate. The addition of bimetallic MXene is expected to generate a variety of active substances in the 2LiBH4+ MgH2 composite system, so as to better improve the hydrogen storage performance of the composite system. It provides a new perspective and optimization path for the practical application of the 2LiBH4+ MgH2 composite system, such as vehicle hydrogen storage and other new energy storage media.

[0005] Chinese patent application CN201310033389.5 discloses a lithium borohydride / rare earth magnesium-based alloy composite hydrogen storage material and a preparation method thereof. The material is composed of lithium borohydride and a rare earth magnesium-based alloy, and has a general formula of LiBH4 / La 1−x Mg x Ni a Co b Mn c Al d , and the mass percentage of the rare earth magnesium-based alloy in the composite material is 10-80%, wherein x =0.1-0.8, a=2.7-3.2, b=0.1-0.8, c=0.1-0.4, and d=0.05-0.5. According to the component ratio, the alloy sheet is melted and spun, and after heat treatment and cooling, the spun sheet alloy powder is obtained by ball milling, screening, hydrogenation treatment, and mixing with LiBH4 and the alloy powder in a mass ratio, and then adding heptane, hexane or tetrahydrofuran for ball milling. After freeze-drying, the lithium borohydride / rare earth magnesium-based alloy composite hydrogen storage material is obtained. However, the hydrogen storage material provided by the patent has relatively poor cycle performance. SUMMARY

[0006] The purpose of the present application is to provide a high-performance borohydride / magnesium-based composite hydrogen storage material with lower hydrogen absorption / desorption temperature, faster kinetics and excellent cycle retention rate.

[0007] The purpose of the present application can be achieved by the following technical solutions: In a first aspect, the present application provides a high-performance borohydride / magnesium-based composite hydrogen storage material, which is obtained by ball-mixing TiVC MXene powder with LiH and MgB2 and then heating and hydrogenating, wherein the mass content of the TiVC MXene powder is not more than 9%.

[0008] In a second aspect, the present application provides a preparation method of a high-performance borohydride / magnesium-based composite hydrogen storage material, which comprises the following steps: S1, placing LiF in hydrochloric acid, heating and stirring, adding a precursor TiVAlC MAX, reacting, centrifuging, washing and freeze-drying the obtained product to obtain layered TiVC MXene powder; S2, ball-mixing the TiVC MXene powder obtained in S1 with LiH and MgB2, and then heating and hydrogenating to obtain a borohydride / magnesium-based composite hydrogen storage material.

[0009] Further, in S1, the concentration of hydrochloric acid is 8-10 mol / L, the ratio of the addition amounts of LiF, hydrochloric acid and the precursor TiVAlC MAX is (1.8-2.2) g:(1.0-1.4) g:(33-44) mL, for example, it can be 2 g:1.2 g:40 mL, or other values within the above range.

[0010] Further, in S1, the reaction temperature is 40-50 DEG C, preferably 45 DEG C, and the time is 36-60 h, preferably 48 h.

[0011] Further, in S1, the freeze-drying temperature is below -35 DEG C, and the time is 12-36 h, preferably 24 h.

[0012] Further, in S2, the mass ratio of LiH and MgB2 is 1:(2.5-3.5), and the addition amount of TiVC MAXene powder satisfies that the mass fraction thereof in the ball milling system is 3-9%.

[0013] Further, in S2, the ball-to-material ratio during ball milling is 40-60:1, preferably 50:1, the ball milling speed is 350-450 rpm, preferably 400 rpm, and the time is 8-12 h.

[0014] Further, in S2, the heating hydrogenation process is carried out in a pure hydrogen atmosphere, and the heating temperature is controlled to be 330-370 DEG C, preferably 350 DEG C, and the hydrogen pressure is 8-10 MPa, preferably 9 MPa.

[0015] Further, in S2, the heating hydrogenation time is 8-12 h.

[0016] In a third aspect, the application provides a high-performance borohydride / magnesium-based composite hydrogen storage material for use in vehicle-mounted hydrogen storage and hydrogen storage coupled with new energy.

[0017] The application uses TiVAlC MAX powder, LiH and MgB2 as initial raw materials to prepare a composite hydrogen storage material through ball milling and hydrogenation. First, TiVAlC MAX is treated by etching to obtain TiVC MXene. Then, LiH and MgB2 are mixed and ball milled with different addition amounts of TiVC MXene. During the process, the above-mentioned materials are uniformly mixed, the particle size is refined, the interface contact area is increased, and defects are introduced, which significantly improves the activity of the raw materials. Heating hydrogenation can convert LiH and MgB2 into LiBH4 and MgH2. Finally, the composite material 2LiBH4+MgH2 is obtained. x wt% TiVC ( xLiBH4+MgH2+LiF+TiVC (x=0, 3, 6, 9) (referred to as LMBH), characterized by high hydrogen storage capacity and excellent reversibility.

[0018] Compared with the prior art, the present application has the following advantages: (1) The prepared high-performance borohydride / magnesium-based composite hydrogen storage material has lower hydrogen absorption / desorption temperature, faster kinetics and excellent cycle stability.

[0019] (2) LiBH4, MgH2, LiF, precursor TiVAlC powder, HCl solution and other conventional drugs are used as raw materials, and are prepared based on etching and ball milling. The process is mature, simple, efficient, the obtained sample has high purity, excellent hydrogen storage performance, and can realize large-scale production. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 It is an image of the precursor TiVAlC MAX and the TiVC MXene powder obtained after etching in Example 1, wherein (a) is an electron image and an element energy spectrum of TiVC MXene, (b) is an SAED and HRTEM image of TiVC MXene, (c) is a SEM image of TiVAlC, and (d) is a SEM image of TiVC MXene.

[0021] Figure 2 It is an image of 2LiBH4+ MgH2+ 6wt% TiVC (x=0, 6) composite material prepared in Example 1 and Comparative Example 1, wherein (a) is a SEM image of 2LiBH4+ MgH2 after the first hydrogen desorption, (b) is a SEM image of 2LiBH4+ MgH2+ 6wt% TiVC after the first hydrogen desorption, (c) is a SEM image of 2LiBH4+ MgH2 after the third hydrogen desorption, and (d) is a SEM image of 2LiBH4+ MgH2+ 6wt% TiVC after the fifteenth hydrogen desorption. x x It is a temperature programmed desorption (TPD) curve of 2LiBH4+ MgH2+ 6wt% TiVC (x=0, 3, 6, 9) composite hydrogen storage material prepared in Example 1, Example 2, Example 3 and Comparative Example.

[0022] Figure 3 x It is a 15-cycle hydrogen absorption / desorption curve of 2LiBH4+ MgH2+ 6wt% TiVC composite hydrogen storage material prepared in Example 1 at 350°C, 9MPa, 400°C, 0.3MPa. x

[0023] Figure 4 ​​​​

[0024] Figure 5 XRD patterns of 2LiBH4+ MgH2+ 6 wt% TiVC composite prepared in Example 1, Example 2, Example 3 and Comparative Example. x wt% TiVC ( x XRD patterns of 2LiBH4+ MgH2+ 6 wt% TiVC composite prepared in Example 1, Example 2, Example 3 and Comparative Example.

[0025] Figure 6 XRD patterns of 2LiBH4+ MgH2+ 6 wt% TiVC composite prepared in Example 1 and Comparative Example 1 after the first dehydrogenation (A), the fifteenth dehydrogenation (C), the fifteenth hydrogenation (E); 2LiBH4+ MgH2after the first dehydrogenation (B), the third dehydrogenation (D), the third hydrogenation (F).

[0026] Figure 7 HRTEM image of 2LiBH4+ MgH2+ 6 wt% TiVC composite prepared in Example 1 after the fifteenth dehydrogenation.

[0027] Figure 8 400 °C isothermal dehydrogenation test curve of the composite prepared in Comparative Example 1.

[0028] Figure 9 400 °C isothermal dehydrogenation test curve of the composite prepared in Comparative Example 2. DETAILED DESCRIPTION

[0029] The application will be described in greater detail with reference to the accompanying drawings and specific embodiments. The embodiments are implemented on the premise of the technical solution of the application, and detailed implementation and specific operation processes are given, but the protection scope of the application is not limited to the following examples.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description herein is for describing the specific embodiments only and is not intended to be limiting of the application.

[0031] The selection scope of the terms "and / or", "or / and", "and / or" used in the present application includes any one of two or more relevant listed items, and also includes any and all combinations of the relevant listed items, including any two relevant listed items, any more relevant listed items, or all relevant listed items. It should be noted that when at least three items are connected by at least two conjunctions selected from "and / or", "or / and", "and / or", it should be understood that in the present application, the technical solution undoubtedly includes the technical solution connected by "logical and", and also undoubtedly includes the technical solution connected by "logical or".

[0032] In the present application, the technical features described in an open manner include both the closed technical solution consisting of the listed features and the open technical solution containing the listed features.

[0033] In the present application, as long as there is no special description, the numerical range is considered to be continuous, and includes the minimum value and the maximum value of the range, as well as every value between the minimum value and the maximum value. Further, when the range refers to an integer, every integer between the minimum value and the maximum value of the range is included. In addition, when multiple ranges are provided to describe a feature or a characteristic, the ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all sub-ranges therein.

[0034] Only some numerical ranges are specifically disclosed herein. However, any lower limit can be combined with any upper limit to form a range not explicitly recited; and any lower limit can be combined with other lower limits to form a range not explicitly recited, and likewise any upper limit can be combined with any other upper limit to form a range not explicitly recited. In addition, each individual disclosed point or single numerical value can itself be combined as a lower limit or an upper limit with any other point or single numerical value or with other lower limits or upper limits to form a range not explicitly recited.

[0035] In the present application, the temperature parameter, unless otherwise specified, allows for constant temperature treatment, and also allows for treatment within a certain temperature range. The constant temperature treatment allows the temperature to fluctuate within the accuracy range controlled by the instrument. Fluctuation within a range such as ±5°C, ±4°C, ±3°C, ±2°C, ±1°C is allowed.

[0036] In the present application, "suitable" in "suitable combination", "suitable manner", "any suitable manner" and the like means that the technical solution of the present application can be implemented, the technical problems of the present application can be solved, and the expected technical effects of the present application can be achieved.

[0037] In the present application, "further", "even further", "in particular" and the like are used for descriptive purposes only and should not be interpreted as limiting the scope of the present application.

[0038] In the present application, "optionally", "optional" or "optional" means optional, i.e. selected from either of the two parallel schemes "with" or "without". If there are multiple "options" in a technical solution, each "option" is independent of each other unless otherwise specified, and there is no contradictory relationship or mutual restriction.

[0039] In the description of the application, "multiple" means at least two, for example, two, three, etc., unless otherwise specifically limited.

[0040] Unless otherwise specified, all formulations and tests in the present application occur in an environment of 25°C.

[0041] In the present application, "including", "containing", "comprising", "having", "possessing" or other variants are intended to cover non-closed inclusion, and there is no distinction between these terms. The term "comprising" means that other steps and ingredients can be added without affecting the final result. The compositions and methods / processes of the present application comprise, consist of and consist essentially of the essential elements and limitations described herein and any additional or optional ingredients, components, steps or limitations described herein. There is no distinction between the terms "efficiency", "performance", "effect", "efficacy" in the present application.

[0042] If not specifically stated, all embodiments and optional embodiments of the present application can be combined to form new technical solutions. If not specifically stated, all technical features and optional technical features of the present application can be combined to form new technical solutions.

[0043] If not specifically stated, all steps of the present application can be performed in sequence or randomly, preferably in sequence.

[0044] In the following examples, the TiVC MAX powder used was purchased from Foshan Xinyan Technology Co., Ltd.; lithium hydride powder (LiH, purity 99.9%, Alfa Aesar), magnesium boride powder (MgB2, purity 99%, Aladdin), lithium fluoride powder (LiF, purity 99.9%, Aladdin), hydrochloric acid (HCl, 9M, Aladdin), and the rest of the raw materials were commercially available products in the art unless otherwise specified.

[0045] Example 1: The present embodiment provides a method for preparing a high-performance 2LiBH4+ MgH2+ 6 wt% TiVC high-performance borohydride and magnesium-based composite hydrogen storage material, and the specific steps are as follows: (1) 1.2 g of LiF was placed in 40 mL of hydrochloric acid (9 M) and stirred in a Teflon-lined cap for 15 min while heating to 45 °C with an oil bath; (2) 2 g of the precursor TiVAlC MAX was added to the above LiF and HC1 mixed solution in five times, and placed in a magnetic rotor for stirring for 48 h, keeping the temperature at 45 °C; (3) The sample obtained in step (2) was centrifuged and washed with deionized water, repeated for several times, and the supernatant was detected to be neutral; (4) The sample prepared in step (3) was suction filtered to obtain a solid product; (5) The solid product in step (4) was freeze-dried for 24 h, and the obtained product was TiVC MXene.

[0046] Figure 1 Figures (a), (b), (c) and (d) respectively show the electron image and element energy spectrum (a), SAED and HRTEM images (b), SEM image of TiVAlC (c) and SEM image of TiVC (d) of the TiVC MXene material prepared in this step. As shown in the figure, the TiVC MXene material has a clear accordion layered structure. This structure has good stability and at the same time provides more active sites for hydrogen absorption and desorption reactions; (6) 79 mg of LiH and 229 mg of MgB2 were taken and placed in a 100 mL ball mill jar together with 18.5 mg of TiVC MXene material obtained in step (5), the mass ratio of ball mill ball to powder was 50:1, and the ball milling was carried out at a speed of 400 rpm for 10 h to obtain a composite hydrogen storage material, which was recorded as 2LiH + MgB2+ 6 wt% TiVC; (7) The material obtained in step (6) was placed in a reactor, and pure hydrogen gas with a hydrogen pressure of 9 MPa was introduced, and 2LiBH4+ MgH2+ 6 wt% TiVC borohydride and magnesium-based composite hydrogen storage material with high performance were obtained by heating at 350 °C for 10 h.

[0047] Figure 4 The 15-cycle hydrogen absorption and desorption curves of the high-performance 2LiBH4+ MgH2+ 6 wt% TiVC borohydride / magnesium-based composite hydrogen storage material prepared in this step. The composite material can release 9.3 wt% of hydrogen gas within 35 min at 400 °C. It can absorb hydrogen completely within 30 min at 350 °C, and the hydrogen absorption capacity reaches 9.3 wt%, and the capacity retention rate is 96% when cycled to the fifteenth time. This shows that TiVC MXene significantly improves the cycle stability of the composite material.

[0048] Figure 7Figures (a) and (b) show the SAED and HRTEM images of the high-performance 2LiBH4+ MgH2+ 6 wt% TiVC borohydride and magnesium-based composite hydrogen storage material prepared in this step after 15 desorption cycles. From the (a) figure, the corresponding diffraction rings of MgB2(101), V7C8(440), and TiH (222) crystal planes can be observed. From the (b) figure, the MgB2(101) crystal plane, LiH (200) crystal plane, V7C8(440) crystal plane, and TiH (200) crystal plane can be observed, and the TiH / V7C8 and substrate symbiotic interface can also be observed. There are TiH / LiH / V7C8 / MgB2 interfaces in the composite material, and hydrogen has a lower diffusion energy at the grain boundary, which provides a channel for the diffusion of hydrogen during the hydrogen absorption and desorption process, and at the same time improves the kinetic performance of the composite system.

[0049] Example 2 The preparation method of the 2LiBH4+ MgH2+ 3 wt% TiVC borohydride / magnesium-based composite hydrogen storage material provided in this embodiment is as follows: (1) 1.2 g of LiF was placed in 40 mL of hydrochloric acid (9 M) and stirred in a Teflon-lined cap for 15 min, while an oil bath was used to heat it to 45 °C; (2) 2 g of the precursor TiVAlC MAX was added to the above LiF and HCl mixed solution in five times, and placed in a magnetic rotor for stirring for 48 h, keeping the temperature at 45 °C; (3) The sample obtained in step (2) was centrifuged and washed with deionized water, and after repeated multiple times, the supernatant was detected to be neutral; (4) The sample prepared in step (3) was suction filtered to obtain the product; (5) The product in step (4) was freeze-dried for 24 h, and the obtained product was TiVC MXene; (6) 79 mg of LiH and 229 mg of MgB2 were placed in a 100 mL ball mill jar together with 9.3 mg of the TiVC MXene catalyst obtained in step (5), and the mass ratio of ball mill ball to powder was 50:1, and the ball milling was carried out at a speed of 400 rpm for 10 h to obtain a composite hydrogen storage material, which was denoted as 2LiH + MgB2+ 3wt% TiVC; (7) The material obtained in step (6) was placed in a reactor, and 9 MPa of hydrogen pressure was introduced, and the temperature was kept at 350 °C for 10 h to obtain a high-performance 2LiBH4+ MgH2+ 3wt% TiVC borohydride and magnesium-based composite hydrogen storage material.

[0050] Example 3 The preparation method of the 2LiBH4+ MgH2+ 9 wt% TiVC borohydride and magnesium-based composite hydrogen storage material provided by the embodiment is as follows: (1) 1.2 g of LiF was placed in 40 mL of hydrochloric acid (9 M) and stirred in a Teflon-lined cap for 15 min, while heating to 45 °C with an oil bath; (2) 2 g of the precursor TiVAlC MAX was added to the above LiF and HCl mixed solution in five times, and placed in a magnetic rotor for stirring for 48 h, keeping the temperature at 45 °C; (3) The sample obtained in step (2) was centrifuged and washed with deionized water, and after repeated multiple times, the supernatant was detected to be neutral; (4) The sample prepared in step (3) was suction filtered to obtain the product; (5) The product in step (4) was freeze-dried for 24 h, and the obtained product was TiVC MXene; (6) 79 mg of LiH and 229 mg of MgB2 were placed in a 100 mL ball mill jar together with 27.8 mg of the TiVC MXene catalyst obtained in step (5), the mass ratio of ball mill ball to powder was 50:1, and the ball milling was carried out at a speed of 400 rpm for 10 h to obtain a composite hydrogen storage material, which was recorded as 2LiH + MgB2+ 9wt% TiVC; (7) The material obtained in step (6) was placed in a reactor, 9 MPa of hydrogen pressure was introduced, and 350 °C was kept for 10 h to obtain a high-performance 2LiBH4+ MgH2+ 9 wt% TiVC borohydride and magnesium-based composite hydrogen storage material.

[0051] Comparative Example 1 (1) 79 mg of LiH and 229 mg of MgB2 were placed in a 100 mL ball mill jar, the mass ratio of ball mill ball to powder was 50:1, and the ball milling was carried out at a speed of 400 rpm for 10 h to obtain a 2LiH + MgB2 composite material; (2) The material obtained in step (1) was placed in a reactor, 9 MPa of hydrogen pressure was introduced, and 350 °C was kept for 10 h to obtain a comparative sample 2LiBH4+ MgH2 borohydride / magnesium-based composite hydrogen storage material.

[0052] Figure 2Images (a), (b), (c), and (d) provide SEM images of the 2LiBH4+MgH2 borohydride and magnesium-based composite hydrogen storage material prepared in the comparative example after the first and third hydrogen releases, and SEM images of the high-performance 2LiBH4+MgH2+ 6 wt% TiVC borohydride and magnesium-based composite hydrogen storage material prepared in Example 1 after the first and fifteenth hydrogen releases. It can be seen that, regardless of whether it is the first or fifteenth hydrogen release, the size of the 2LiBH4+MgH2+ 6 wt% TiVC is small, and there is no aggregation. This indicates that the addition of TiVC effectively suppresses aggregation during the reaction process.

[0053] Figure 3 The 2LiBH4+ MgH2+ samples prepared in Examples 1, 2, 3 and the comparative examples are provided. x wt% TiVC ( x The TPD (temperature programmed desorption) performance test results of the composite material (= 0, 3, 6, 9) show that 2LiBH4 + MgH2 begins to decompose and release hydrogen at around 348 °C. After adding TiVC MXene, the decomposition temperature of MgH2 decreases by 18 °C. The hydrogen release process of LiBH4 ends about 50 °C earlier.

[0054] Figure 5 2LiBH4+ MgH2+ was prepared in Examples 1, 2, 3 and the Comparative Example. x wt% TiVC ( x XRD patterns of composite hydrogen storage materials (= 0, 3, 6, 9). This verifies the 2LiH + MgB2+ molecule. x wt% TiVC ( x = 0, 3, 6, 9) are converted to 2LiBH4+ MgH2+ after hydrogenation treatment. x wt% TiVC ( x = 0, 3, 6, 9). TiH and V7C8 were also detected.

[0055] Figure 6 The images show the XRD patterns of the 2LiBH4+MgH2+6 wt% TiVC composite materials prepared in Example 1 and the comparative example after the first hydrogen release (A), the fifteenth hydrogen release (C), and the fifteenth hydrogen absorption (E); and the XRD patterns of 2LiBH4+MgH2 after the first hydrogen release (B), the third hydrogen release (D), and the third hydrogen absorption (F). The difference between 2LiBH4+MgH2+6 wt% TiVC and 2LiBH4+MgH2 before and after hydrogen absorption / desorption lies in the detection of two active substances: TiH and V7C8. These two active substances are stable once formed and catalyze the hydrogen absorption / desorption reaction process of the composite material.

[0056] Comparative Example 2: Most of the same as Example 1, except replacing TiVC MXene powder with equal mass of VNbC MXene powder. Figure 8 The 400 °C isothermal dehydrogenation test curves for LMBH + 6 wt% TiVC and LMBH + 6 wt% VNbC. It can be seen that LMBH + 6 wt% TiVC has a faster dehydrogenation rate, which shows that the material after etching treatment has better improvement effect.

[0057] Comparative Example 3: Most of the same as Example 1, except replacing TiVC MXene powder with equal mass of TiVAlC powder. Figure 9 The 400 °C isothermal dehydrogenation test curves for LMBH + 6 wt% TiVC and LMBH + 6 wt% TiVAlC. It can be seen that LMBH + 6 wt% TiVC has a faster dehydrogenation rate, which shows that the material after etching treatment has better improvement effect.

[0058] The above description of comparative examples is to facilitate the ordinary skilled person in the art to understand and use the invention. Those skilled in the art can obviously make various modifications to these examples, and apply the general principles described herein to other examples without having to go through creative labor. Therefore, the present application is not limited to the above examples, and the improvements and modifications made by those skilled in the art according to the disclosure of the present application without departing from the scope of the present application should be within the scope of protection of the present application.

Claims

1. A high performance borohydride / magnesium based composite hydrogen storage material, characterized in that, The borohydride / magnesium-based composite hydrogen storage material is obtained by hydrogenation after ball-milling and mixing of TiVC MXene powder, LiH and MgB2, wherein the mass content of the TiVC MXene powder is not more than 9%.

2. The preparation method of a high-performance borohydride / magnesium-based composite hydrogen storage material as described in claim 1, characterized in that, The method comprises the following steps: S1, taking LiF and placing it in hydrochloric acid, heating and stirring, then adding a precursor TiVAlC MAX, reacting, centrifuging, washing, freeze-drying the obtained product to obtain layered TiVC MXene powder; S2, ball-milling and mixing the TiVC MXene powder obtained in S1 with LiH and MgB2, and then hydrogenating to obtain a borohydride / magnesium-based composite hydrogen storage material.

3. The method for preparing high-performance borohydride / magnesium-based composite hydrogen storage material according to claim 2, characterized in that, In S1, the concentration of the hydrochloric acid is 8-10 mol / L, and the adding amount ratio of LiF, hydrochloric acid and the precursor TiVAlC MAX is (1.8-2.2) g:(1.0-1.4) g:(33-44) mL.

4. The method for preparing a high-performance borohydride / magnesium-based composite hydrogen storage material according to claim 2, characterized in that, In S1, the reaction temperature is 40-50℃, and the reaction time is 36-60 h.

5. The method for preparing a high-performance borohydride / magnesium-based composite hydrogen storage material according to claim 2, characterized in that, In S1, the freeze-drying temperature is below -35℃, and the freeze-drying time is 12-36 h.

6. The method for preparing a high-performance borohydride / magnesium-based composite hydrogen storage material according to claim 2, characterized in that, In S2, the mass ratio of LiH and MgB2 is 1:(2.5-3.5), and the adding amount of the TiVC MXene powder satisfies that the mass fraction of the TiVC MXene powder in the ball-milling system is 3-9%.

7. The method for preparing a high-performance borohydride / magnesium-based composite hydrogen storage material according to claim 2, characterized in that, In S2, the ball-to-material ratio during the ball-milling is 40-60:1, the ball-milling rotation speed is 350-450 rpm, and the ball-milling time is 8-12 h.

8. The method for preparing a high-performance borohydride / magnesium-based composite hydrogen storage material according to claim 2, characterized in that, In S2, the hydrogenation process is carried out in a pure hydrogen atmosphere, and the heating temperature is controlled to be 330-370℃, the hydrogen pressure is 8-10 MPa.

9. The method for preparing a high-performance borohydride / magnesium-based composite hydrogen storage material according to claim 2, characterized in that, In S2, the hydrogenation time is 8-12 h.

10. Application of the high-performance borohydride / magnesium-based composite hydrogen storage material of claim 1 in vehicle-mounted hydrogen storage and hydrogen storage coupled with new energy.

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