A magnesium hydride-vanadium pentoxide@carbon composite hydrogen storage material and its preparation method and application

Abstract

The present invention relates to a magnesium hydride - vanadium pentoxide @ carbon composite hydrogen storage material and its preparation method and application, belonging to the technical field of the preparation of composite hydrogen storage materials. The magnesium hydride - vanadium pentoxide @ carbon composite hydrogen storage material (MgH2 - V2O5@C) of the present invention comprises vanadium pentoxide @ carbon (V2O5@C) nanomaterial powder and magnesium hydride (MgH2) nanomaterial powder, wherein the vanadium pentoxide @ carbon (V2O5@C) nanomaterial powder is coated on the surface of the magnesium hydride (MgH2) nanomaterial powder and the mass percentage of the vanadium pentoxide @ carbon (V2O5@C) nanomaterial powder is 0.1 - 15 wt.%. Due to the doping of the V2O5@C catalyst, the hydrogen storage performance of the composite hydrogen storage material (MgH2 - V2O5@C) of the present invention is significantly improved.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of composite hydrogen storage materials, and relates to a magnesium hydride-vanadium pentoxide@carbon composite hydrogen storage material and a preparation method and application thereof. Background Art

[0002] The increasingly serious energy crisis and the environmental degradation caused by the use of traditional fossil fuels have made it urgent to explore and implement alternative energy carriers. Among a series of potential alternative energy sources, hydrogen energy has become a potential choice due to its characteristics of high efficiency, cleanness and diverse sources. The hydrogen energy system consists of hydrogen production technology, hydrogen storage technology, hydrogen transmission technology and hydrogen utilization technology. Among them, hydrogen storage technology is the key link. How to safely, efficiently and effectively store and transport hydrogen remains a challenge for the large-scale utilization of hydrogen energy.

[0003] Hydrogen storage technologies are mainly divided into gaseous hydrogen storage, liquid hydrogen storage and solid hydrogen storage. The volume density of gaseous hydrogen storage is relatively low (39.05kg / m 3 ), high pressure (35-70MPa) is required to increase the hydrogen storage density, and hydrogen storage in steel cylinders is prone to hydrogen embrittlement, which leads to higher requirements for the material of the cylinder. Gaseous hydrogen storage also has disadvantages such as high risk of leakage during transportation and use, and is prone to explosion. The storage and transportation process of liquid hydrogen storage needs to be kept at low temperatures, and the energy consumed accounts for about 25-45% of the stored hydrogen energy. The storage and transportation process costs are high; and liquid hydrogen is unstable and volatile, and there are many safety hazards during transportation and use, which limits its commercialization. Solid-state hydrogen storage is a method of storing hydrogen in the form of hydrogen atoms. It has a large hydrogen storage capacity, high safety, and is easy to store and transport. It is a hydrogen storage method with great application potential.

[0004] Since magnesium hydride (MgH 2 ) is considered to be a promising solid-state hydrogen storage material due to its high hydrogen storage capacity (7.6 wt.%), good cycling performance, and abundant reserves. 2 Higher thermodynamic stability (ΔH = -75 kJ·mol -1 ) and slow kinetics (E a =161 kJ·mol -1 ) limits its practical application. In recent years, people have adopted methods including alloying, nano-sizing, nano-confinement, and catalytic doping to improve MgH 2 hydrogen storage performance.

[0005] Catalytic doping is one of the research hotspots of modified magnesium-based hydrogen storage materials. This method can significantly improve the hydrogen absorption and desorption kinetics of hydrogen storage materials by adding a small amount of catalyst. Mechanical alloying is one of the main methods for preparing composite hydrogen storage materials. This method is simple and easy to control. Mechanical alloying is a process that continuously breaks up cold welds during ball milling to refine MgH 2 While the catalyst is being granulated, 2 The catalyst and MgH 2 The active species formed in situ can effectively increase the MgH 2 The kinetics of hydrogen absorption and desorption.

[0006] Vanadium oxide has significant advantages in the catalytic performance of magnesium-based hydrogen storage materials, mainly reflected in: first, due to its chemical inertness and thermal stability, it degrades slowly, and compared with other catalysts, vanadium oxide has a longer life; second, it exhibits high catalytic activity and can effectively reduce the energy barrier of hydrogen absorption and desorption, thereby increasing the absorption / desorption rate and capacity of hydrogen, achieving faster hydrogen storage reactions and higher energy density; finally, vanadium oxide, as a low-cost non-precious metal catalyst, can reduce the cost of hydrogen storage materials.

[0007] Therefore, there is great application potential in the preparation of magnesium-based hydrogen storage composites using vanadium oxide catalysts. Summary of the invention

[0008] In view of this, one of the objects of the present invention is to provide a magnesium hydride-vanadium pentoxide @ carbon composite hydrogen storage material; a second object of the present invention is to provide a method for preparing a magnesium hydride-vanadium pentoxide @ carbon composite hydrogen storage material; a third object of the present invention is to provide an application of a magnesium hydride-vanadium pentoxide @ carbon composite hydrogen storage material in the storage and transportation of hydrogen.

[0009] In order to achieve the above object, the present invention provides the following technical solutions:

[0010] 1. A magnesium hydride-vanadium pentoxide @ carbon composite hydrogen storage material, the magnesium hydride-vanadium pentoxide @ carbon (MgH 2 -V 2 O 5 @C) composite hydrogen storage material includes vanadium pentoxide @ carbon (V 2 O 5 @C) Nanomaterial powder and magnesium hydride (MgH 2 ) nano material powder, wherein the vanadium pentoxide @ carbon (V 2 O 5 @C) Nanomaterial powder coated on magnesium hydride (MgH 2 ) Nanomaterial powder surface;

[0011] The magnesium hydride-vanadium pentoxide@carbon (MgH 2 -V 2 O 5 @C) Vanadium pentoxide @ carbon (V 2 O 5 @C) The mass percentage of nano material powder is 0.1 to 15wt.%.

[0012] Preferably, the magnesium hydride-vanadium pentoxide@carbon (MgH 2 -V 2 O 5 @C) Vanadium pentoxide @ carbon (V 2 O 5 @C) The mass percentage of nano material powder is 3 to 12 wt.%.

[0013] Preferably, the magnesium hydride-vanadium pentoxide@carbon (MgH 2 -V 2 O 5 @C) Vanadium pentoxide @ carbon (V 2 O 5 @C) The mass percentage of nano material powder is 3 to 9 wt.%.

[0014] Preferably, the magnesium hydride-vanadium pentoxide@carbon (MgH 2 -V 2 O 5 @C) The average particle size of the composite hydrogen storage material is 2 to 5 μm.

[0015] Preferably, the magnesium hydride (MgH 2 ) The particle size of the nano material powder is 10 to 30 μm; the vanadium pentoxide @ carbon (V 2 O 5 @C) The nanomaterial powder is a nano-sheet structure powder with a diameter of 100 to 600 nm and a layer thickness of 2 to 10 nm.

[0016] 2. According to the preparation method of the above composite hydrogen storage material, the preparation method comprises the following steps:

[0017] (1) Preparation of vanadium pentoxide @ carbon (V 2 O 5 @C) Nanomaterial powder: The accordion-shaped multilayer V synthesized by etching 2 C nanomaterial powder was intercalated and ultrasonically exfoliated to obtain few-layer V 2 C nanomaterials, and then calcined at 300-600°C for 15-25h in a carbon dioxide atmosphere to obtain vanadium pentoxide @ carbon (V 2 O 5 @C) Nanomaterial powder;

[0018] (2) Preparation of composite hydrogen storage material: Vanadium pentoxide@carbon (V 2 O 5 @C) Nanomaterial powder and magnesium hydride (MgH 2 ) nanomaterial powders are mixed and ball milled to obtain composite hydrogen storage materials (MgH 2 -V 2 O 5 @C).

[0019] Preferably, the few layers of V in step (1) 2 The specific preparation method of C nanomaterials is: 2 AlC powder was added into a mixed acid solution formed by mixing hydrofluoric acid and hydrochloric acid, and etched at 50-60°C for 1-3 days to obtain an accordion-shaped multilayer V 2 C nanomaterial powder, continue to add tetrabutylammonium hydroxide (TBAOH) solution and stir at room temperature for 1 to 2 days, and prepare a few-layer V 2 C nanomaterials;

[0020] The mass fraction of the hydrofluoric acid is 49%, the mass fraction of the hydrochloric acid is 36-38%, and the volume ratio of the hydrofluoric acid to the hydrochloric acid in the mixed acid solution is 3:2;

[0021] The mass fraction of tetrabutylammonium hydroxide (TBAOH) in the tetrabutylammonium hydroxide (TBAOH) solution is 5%;

[0022] The V 2 The mass volume ratio of AlC powder, hydrofluoric acid and hydrochloric acid is 2:30:20, g:ml:ml;

[0023] The V 2 The mass volume ratio of AlC powder and tetrabutylammonium hydroxide (TBAOH) solution is 2:10-25, g:ml.

[0024] Preferably, in step (2), the specific conditions for ball milling are: stainless steel balls are used as ball milling beads under a protective atmosphere, the ball-to-material ratio is 20 to 60:1, the ball milling method is forward and reverse intermittent ball milling, the ball milling time is 4 to 24 hours, and the ball mill revolution speed is 300 to 500 rpm.

[0025] Further preferably, the ball-to-material ratio is 40:1, the ball milling time is 12 h, and the ball mill revolution speed is 400 rpm.

[0026] 3. Application of the above composite hydrogen storage material in the storage and transportation of hydrogen.

[0027] The beneficial effects of the present invention are as follows: the present invention discloses a magnesium hydride-vanadium pentoxide@carbon composite hydrogen storage material (MgH 2 -V 2 O 5 @C), including vanadium pentoxide @carbon (V 2 O 5 @C) Nanomaterial powder and magnesium hydride (MgH 2 ) nanomaterial powder, wherein vanadium pentoxide@carbon (V 2 O 5 @C) Nanomaterial powder coated on magnesium hydride (MgH 2 ) nanomaterial powder surface and vanadium pentoxide @ carbon (V 2 O 5 @C) The mass percentage of nano material powder is 0.1-15wt.%. The composite hydrogen storage material prepared by the present invention has the following characteristics: (1) It has an effective hydrogen storage capacity of 6.25wt.% at 325℃; (2) It can release 3.59wt.% and 4.96wt.% of hydrogen within 125min and 50min at 200℃ and 225℃ respectively; (3) It can release 1.48wt.% of hydrogen within 7.5h even at a lower dehydrogenation temperature (180℃). The magnesium hydride-vanadium pentoxide @ carbon composite hydrogen storage material of the present invention has V 2 O 5 The doping of @C catalyst also significantly improved the hydrogen absorption performance. Specifically: (1) At 150°C, the composite hydrogen storage material can absorb 6.03wt.% of hydrogen; (2) Even at room temperature (25°C), it can absorb 3.90wt.% of hydrogen within 2.7h. 2 At 250℃, it can hardly release hydrogen; at 125℃, it absorbs 3.90wt.% hydrogen in 60min. Therefore, ball-milled MgH 2 It is better to dope V 2 O 5 Therefore, the composite hydrogen storage material (MgH 2 -V 2 O 5 @C) Due to V 2 O 5 @C doping significantly improves the hydrogen storage performance.

[0028] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0030] Figure 1 V prepared in Example 1 2 O 5 @Scanning electron microscope image of C;

[0031] Figure 2 V prepared in Example 1 2 O 5 @C, less layer V 2 C nanomaterials, multilayer V 2 C nanomaterials, V 2 AlC powder, standard VO 2 And standard V 2 O 5 X-ray diffraction pattern of

[0032] Figure 3 The V prepared in Example 1 contains 6 wt.% 2 O 5 @C doped MgH 2 -V 2 O 5 @CIsothermal hydrogen release curve of composite hydrogen storage material at different temperatures;

[0033] Figure 4 The V prepared in Example 1 contains 6 wt.% 2 O 5 @C doped MgH 2 -V 2 O 5 @CIsothermal hydrogen release curve of composite hydrogen storage material at 180℃;

[0034] Figure 5 The V prepared in Example 1 contains 6 wt.% 2 O 5 @C doped MgH 2 -V 2 O 5 @CIsothermal hydrogen absorption curve of composite hydrogen storage material at different temperatures;

[0035] Figure 6 The V in Examples 1 to 3 contains 6 wt.% 2 O 5 @C doped MgH 2 -V 2 O 5@C Hydrogen absorption curve of composite hydrogen storage material at room temperature (25℃);

[0036] Figure 7 For ball-milled MgH 2 MgH prepared in Comparative Example 1 2 -V 2 O 5 , MgH prepared in Comparative Example 2 2 -V 2 O 5 / C and MgH prepared in Example 1 2 -V 2 O 5 @CIsothermal hydrogen desorption kinetic curve of composite hydrogen storage material at 250℃;

[0037] Figure 8 For ball-milled MgH 2 MgH prepared in Comparative Example 1 2 -V 2 O 5 , MgH prepared in Comparative Example 2 2 -V 2 O 5 / C and MgH prepared in Example 1 2 -V 2 O 5 @CIsothermal hydrogen absorption kinetic curve of composite hydrogen storage material at 125℃;

[0038] Fig. 9 MgH prepared in Example 1 2 -V 2 O 5 @C Cyclic kinetic curve of composite hydrogen storage material at 300°C, where a is the trend of hydrogen storage capacity changing with the number of cycles, and b is the amount of hydrogen released at different numbers of cycles;

[0039] Fig.10 MgH prepared in Example 1 2 -V 2 O 5 @C SEM images of the composite hydrogen storage material in the ball-milled state (a), the first hydrogen release (b), the 46th hydrogen release (c), and the 251st hydrogen release (d).

[0040] Fig.11 MgH prepared in Example 1 2 -V 2 O 5 @C XRD patterns of the composite hydrogen storage material in ball-milled state (Ball-milled), dehydrogenated state (1st DEH), re-absorbed hydrogen state (1st REH) and cycled state (251st DEH);

[0041] Fig.12 MgH prepared in Example 1 2 -V 2 O 5 XPS spectra of @C composite hydrogen storage materials at different cycle times (a) and VO and V 2 O 3 Relative content analysis (b). DETAILED DESCRIPTION

[0042] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0043] Example 1

[0044] A magnesium hydride-vanadium pentoxide@carbon composite hydrogen storage material (MgH 2 -V 2 O 5 @C), the specific preparation method is as follows:

[0045] (1) Preparation of vanadium pentoxide @ carbon (V 2 O 5 @C) Nanomaterial powder: The accordion-shaped multilayer V synthesized by etching 2 C nanomaterial powder was intercalated and ultrasonically exfoliated to obtain few-layer V 2 C nanomaterials (the specific method is as follows: V 2 AlC powder is slowly added into a mixed acid solution formed by mixing 49% by mass hydrofluoric acid and 37% by mass hydrochloric acid (wherein V 2 The mass volume ratio of AlC powder, hydrofluoric acid and hydrochloric acid was 2:30:20, g:ml:ml), and the accordion-shaped multilayer V was obtained by stirring and etching at 55°C for 2 days. 2 C nanomaterial powder, continue to add 5% by mass fraction of tetrabutylammonium hydroxide (TBAOH) solution (where V 2 The mass volume ratio of AlC powder and tetrabutylammonium hydroxide (TBAOH) solution was 2:10, g:ml) and then stirred at room temperature for 1 day. After ultrasonic peeling, a few layers of V 2 C nanomaterial), and then calcined at 400 °C for 15 h in a carbon dioxide atmosphere to obtain vanadium pentoxide @ carbon (V 2 O5 @C) Nanomaterial powder;

[0046] (2) Preparation of composite hydrogen storage material: Vanadium pentoxide@carbon (V 2 O 5 @C) Nanomaterial powder and magnesium hydride (MgH 2 ) nanomaterial powder mixture (including vanadium pentoxide @ carbon (V 2 O 5 @C) the mass of the nanomaterial powder is 6wt.% of the total mass of the two), and ball milling (the specific conditions are: stainless steel balls are used as ball milling beads under protective atmosphere, the ball-to-material ratio is 40:1, the ball milling method is forward and reverse intermittent ball milling, the ball milling time is 12h, and the ball mill revolution speed is 400rpm) to obtain the composite hydrogen storage material (MgH 2 -V 2 O 5 @C).

[0047] Example 2

[0048] A magnesium hydride-vanadium pentoxide@carbon composite hydrogen storage material (MgH 2 -V 2 O 5 @C), the specific preparation method is as follows:

[0049] (1) Preparation of vanadium pentoxide @ carbon (V 2 O 5 @C) Nanomaterial powder: The accordion-shaped multilayer V synthesized by etching 2 C nanomaterial powder was intercalated and ultrasonically exfoliated to obtain few-layer V 2 C nanomaterials (the specific method is as follows: V 2 AlC powder is slowly added into a mixed acid solution formed by mixing 49% by mass hydrofluoric acid and 36% by mass hydrochloric acid (wherein V 2 The mass volume ratio of AlC powder, hydrofluoric acid and hydrochloric acid was 2:30:20, g:ml:ml), and the accordion-shaped multilayer V was obtained by stirring and etching at 50°C for 3 days. 2 C nanomaterial powder, continue to add 5% mass fraction of tetrabutylammonium hydroxide (TBAOH) solution (where V 2 The mass volume ratio of AlC powder and tetrabutylammonium hydroxide (TBAOH) solution was 2:10, g:ml) and then stirred at room temperature for 1 day. After ultrasonic peeling, a few layers of V 2 C nanomaterial), and then calcined at 300 °C for 25 h in a carbon dioxide atmosphere to obtain vanadium pentoxide @ carbon (V 2 O 5 @C) Nanomaterial powder;

[0050] (2) Preparation of composite hydrogen storage material: Vanadium pentoxide@carbon (V 2 O 5 @C) Nanomaterial powder and magnesium hydride (MgH 2 ) nanomaterial powder mixture (including vanadium pentoxide @ carbon (V 2 O 5 @C) the mass of the nanomaterial powder is 6wt.% of the total mass of the two), and ball milling (the specific conditions are: stainless steel balls are used as ball milling beads under protective atmosphere, the ball-to-material ratio is 20:1, the ball milling method is forward and reverse intermittent ball milling, the ball milling time is 24h, and the ball mill revolution speed is 300rpm) to obtain the composite hydrogen storage material (MgH 2 -V 2 O 5 @C).

[0051] Example 3

[0052] A magnesium hydride-vanadium pentoxide@carbon composite hydrogen storage material (MgH 2 -V 2 O 5 @C), the specific preparation method is as follows:

[0053] (1) Preparation of vanadium pentoxide @ carbon (V 2 O 5 @C) Nanomaterial powder: The accordion-shaped multilayer V synthesized by etching 2 C nanomaterial powder was intercalated and ultrasonically exfoliated to obtain few-layer V 2 C nanomaterials (the specific method is as follows: V 2 AlC powder is slowly added into a mixed acid solution formed by mixing 49% by mass hydrofluoric acid and 38% by mass hydrochloric acid (wherein V 2 The mass volume ratio of AlC powder, hydrofluoric acid and hydrochloric acid was 2:30:20, g:ml:ml), and the accordion-shaped multilayer V was obtained by stirring and etching at 30°C for 1 day. 2 C nanomaterial powder, continue to add 5% mass fraction of tetrabutylammonium hydroxide (TBAOH) solution (where V 2 The mass volume ratio of AlC powder and tetrabutylammonium hydroxide (TBAOH) solution was 2:25, g:ml) and then stirred at room temperature for 2 days. After ultrasonic peeling, a few layers of V 2 C nanomaterial), and then calcined at 600 °C for 15 h in a carbon dioxide atmosphere to obtain vanadium pentoxide @ carbon (V 2 O 5 @C) Nanomaterial powder;

[0054] (2) Preparation of composite hydrogen storage material: Vanadium pentoxide@carbon (V 2 O 5@C) Nanomaterial powder and magnesium hydride (MgH 2 ) nanomaterial powder mixture (including vanadium pentoxide @ carbon (V 2 O 5 @C) the mass of the nanomaterial powder is 6wt.% of the total mass of the two), and ball milling (specific conditions are: stainless steel balls are used as ball milling beads under protective atmosphere, the ball-to-material ratio is 60:1, the ball milling method is forward and reverse intermittent ball milling, the ball milling time is 4h, and the ball mill revolution speed is 500rpm) to obtain the composite hydrogen storage material (MgH 2 -V 2 O 5 @C).

[0055] Comparative Example 1

[0056] AMgH 2 -V 2 O 5 Composite hydrogen storage material, the specific preparation method is as follows:

[0057] The commercial vanadium pentoxide (V) with a purity of 99% 2 O 5 ) powder and magnesium hydride (MgH 2 ) nano material powder mixture (including vanadium pentoxide (V 2 O 5 ) powder mass is 6wt.% of the total mass of the two), and the composite hydrogen storage material (MgH 2 -V 2 O 5 ).

[0058] Comparative Example 2

[0059] AMgH 2 -V 2 O 5 / C composite hydrogen storage material, the specific preparation method is as follows:

[0060] The commercial vanadium pentoxide (V) with a purity of 99% 2 O 5 ) powder and commercial activated carbon (C) powder with a purity of 99% and magnesium hydride (MgH 2 ) nano material powder mixture (including vanadium pentoxide (V 2 O 5 ) and activated carbon (C) in a molar ratio of 2:1, mol:mol, and vanadium pentoxide (V 2 O 5 ) and activated carbon (C) powder with a mass of 6 wt.% of the total mass of the three) can be obtained by ball milling to obtain a composite hydrogen storage material (MgH 2 -V 2 O5 / C).

[0061] Performance Testing

[0062] Figure 1 V prepared in Example 1 2 O 5 @C scanning electron microscope image, Figure 2 V prepared in Example 1 2 O 5 @C, less layer V 2 C nanomaterials, multilayer V 2 C nanomaterials, V 2 AlC powder, standard VO 2 And standard V 2 O 5 X-ray diffraction pattern of. Figure 1 and Figure 2 It can be seen that the method in the above embodiment can indeed prepare V 2 O 5 @C.

[0063] Figure 3 The V prepared in Example 1 contains 6 wt.% 2 O 5 @C doped MgH 2 -V 2 O 5 @CIsothermal hydrogen release curve of composite hydrogen storage material at different temperatures. Figure 3 It can be seen that at 325℃, 300℃, 275℃, 250℃, 225℃, 200℃ and 180℃, MgH 2 -V 2 O 5 The maximum hydrogen release amounts of @C composite hydrogen storage materials were 6.30wt.%, 6.28wt.%, 6.12wt.%, 5.88wt.%, 4.96wt.%, 3.59wt.% and 1.48wt.%, respectively.

[0064] Figure 4 The V prepared in Example 1 contains 6 wt.% 2 O 5 @C doped MgH 2 -V 2 O 5 @C isothermal hydrogen release curve of composite hydrogen storage material at 180℃. Figure 4 It can be seen that even at a temperature of 180 °C, MgH 2 -V 2 O 5 @C composite hydrogen storage material can also release 1.48wt.% hydrogen within 7.5h.

[0065] Figure 5 The V prepared in Example 1 contains 6 wt.% 2 O 5 @C doped MgH 2 -V 2 O 5 @C Isothermal hydrogen absorption curve of composite hydrogen storage material at different temperatures. Figure 5 It can be seen that at temperatures of 25°C, 50°C, 75°C, 100°C and 125°C, MgH 2 -V 2 O 5 The maximum hydrogen absorption capacities of @C composite hydrogen storage materials are 3.90wt.%, 6.03wt.%, 5.17wt.%, 4.84wt.%, 4.18wt.% and 3.94wt.% respectively.

[0066] Figure 6 The V in Examples 1 to 3 contains 6 wt.% 2 O 5 @C doped MgH 2 -V 2 O 5 @C room temperature (25℃) hydrogen absorption curve of composite hydrogen storage material. Figure 6 It can be seen that even at room temperature (25°C), the fully dehydrogenated MgH 2 -V 2 O 5 @C composite hydrogen storage material can also absorb 3.90wt.% hydrogen within 2.7h.

[0067] Figure 7 For ball-milled MgH 2 MgH prepared in Comparative Example 1 2 -V 2 O 5 , MgH prepared in Comparative Example 2 2 -V 2 O 5 / C and MgH prepared in Example 1 2 -V 2 O 5 @C isothermal hydrogen desorption kinetic curve of composite hydrogen storage material at 250℃. Figure 7 It can be seen that at a temperature of 250°C, MgH 2 -V 2 O 5 MgH 2 -V 2 O 5 / C and MgH 2 -V 2 O5 @C-catalyzed MgH 2 The hydrogen released in the ball-milled MgH2O2 solution was 4.46 wt.%, 1.66 wt.%, and 5.80 wt.% in 10 min, while the hydrogen released in the ball-milled MgH2O2 solution was 4.46 wt.%, 1.66 wt.%, and 5.80 wt.% in 10 min. 2 Hydrogen release under the same conditions is negligible.

[0068] Figure 8 For ball-milled MgH 2 MgH prepared in Comparative Example 1 2 -V 2 O 5 , MgH prepared in Comparative Example 2 2 -V 2 O 5 / C and MgH prepared in Example 1 2 -V 2 O 5 @C isothermal hydrogen absorption kinetic curve of composite hydrogen storage material at 125℃. Figure 8 It can be seen that MgH 2 -V 2 O 5 @C exhibited the fastest hydrogen uptake rate, reaching 5.0 wt.% hydrogen within 8 min. In contrast, MgH 2 -V 2 O 5 and MgH 2 -V 2 O 5 / C require 14 and 19 min respectively to reach the same hydrogen absorption level.

[0069] Fig. 9 MgH prepared in Example 1 2 -V 2 O 5 @C Cyclic kinetic curve of composite hydrogen storage material at 300°C, where a is the trend of hydrogen storage capacity changing with the number of cycles, and b is the amount of hydrogen released at different numbers of cycles. Fig. 9 It can be seen that MgH 2 -V 2 O 5 The initial hydrogen absorption of @C was 6.02wt.%, which dropped to 4.28wt.% after 46 cycles, accounting for 71.1% of the maximum hydrogen release. As the number of cycles increased, the hydrogen storage capacity gradually increased and finally stabilized at 213 cycles. After completing 251 cycles, MgH 2 -V 2 O 5 The hydrogen release of @C remains at 5.45 wt.%, accounting for 90.5% of the maximum hydrogen absorption, showing good cycling performance.

[0070] Fig.10MgH prepared in Example 1 2 -V 2 O 5 SEM images of the composite hydrogen storage material in the ball-milled state (a), the first hydrogen release (b), the 46th hydrogen release (c), and the 251st hydrogen release (d). Fig.10 It can be seen that the hydrogen absorption and desorption cycle will cause Mg / MgH 2 Agglomeration of particles; it is most obvious after 251 cycles, and the particles of the composite hydrogen storage material are aggregated together in a rod shape.

[0071] Fig.11 MgH prepared in Example 1 2 -V 2 O 5 @C XRD patterns of the composite hydrogen storage material in ball-milled state (Ball-milled), dehydrogenated state (1st DEH), re-absorbed hydrogen state (1st REH) and cycled state (251st DEH). Fig.11 It can be seen that even after 251 hydrogen releases, the XRD spectrum still does not show MgH 2 The presence of the signal indicates that V 2 O 5 @C significantly promoted the 2 In addition, the presence of Mg signals in the re-absorbed hydrogen state samples can be seen, which indicates that the weakening of hydrogen storage during the cycle is caused by the insufficient hydrogenation of Mg during the hydrogen absorption process.

[0072] Fig.12 MgH prepared in Example 1 2 -V 2 O 5 XPS spectra of @C composite hydrogen storage materials at different cycle times (a) and VO and V 2 O 3 Relative content analysis (b). Fig.12 As can be seen in a, V 2 O 5 @C incorporated into MgH 2 In the process, VO and V are formed in situ. 2 O 3 Catalytic Mg / MgH 2 Hydrogen absorption and desorption process. Fig.12 As can be seen in b, as the cycle progresses, V 2 O 3 is constantly reduced to VO. In addition, Fig.12 It can also be seen that the in-situ formed VO acts as a strong hydrogen absorption site; with the increase of VO content, the increase of hydrogen absorption active sites enables part of the deactivated Mg to re-combine with hydrogen, resulting in an increase in hydrogen storage capacity.

[0073] Similarly, the magnesium hydride-vanadium pentoxide@carbon composite hydrogen storage material (MgH 2 -V 2 O 5 The results are similar to those of the magnesium hydride-vanadium pentoxide@carbon composite hydrogen storage material (MgH 2 -V 2 O 5 @C) have similar performances, both have good hydrogen storage and release properties, and have good application prospects in hydrogen storage and transportation.

[0074] In summary, the present invention discloses a magnesium hydride-vanadium pentoxide@carbon composite hydrogen storage material (MgH 2 -V 2 O 5 @C), including vanadium pentoxide @carbon (V 2 O 5 @C) Nanomaterial powder and magnesium hydride (MgH 2 ) nanomaterial powder, wherein vanadium pentoxide@carbon (V 2 O 5 @C) Nanomaterial powder coated on magnesium hydride (MgH 2 ) nanomaterial powder surface and vanadium pentoxide @ carbon (V 2 O 5 @C) The mass percentage of nano material powder is 0.1-15wt.%. The composite hydrogen storage material prepared by the present invention has the following characteristics: (1) It has an effective hydrogen storage capacity of 6.25wt.% at 325℃; (2) It can release 3.59wt.% and 4.96wt.% of hydrogen within 125min and 50min at 200℃ and 225℃ respectively; (3) It can release 1.48wt.% of hydrogen within 7.5h even at a lower dehydrogenation temperature (180℃). The magnesium hydride-vanadium pentoxide @ carbon composite hydrogen storage material of the present invention has V 2 O 5 The doping of @C catalyst also significantly improved the hydrogen absorption performance. Specifically: (1) At 150°C, the composite hydrogen storage material can absorb 6.03wt.% of hydrogen; (2) Even at room temperature (25°C), it can absorb 3.90wt.% of hydrogen within 2.7h. 2 At 250℃, it can hardly release hydrogen; at 125℃, it absorbs 3.90wt.% hydrogen in 60min. Therefore, ball-milled MgH 2 It is better to dope V 2 O 5Therefore, the composite hydrogen storage material (MgH 2 -V 2 O 5 @C) Due to V 2 O 5 @C doping significantly improves the hydrogen storage performance.

[0075] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A magnesium hydride-vanadium pentoxide@carbon composite hydrogen storage material, It is characterized in that The magnesium hydride-vanadium pentoxide@carbon composite hydrogen storage material comprises vanadium pentoxide@carbon nanomaterial powder and magnesium hydride nanomaterial powder, wherein the vanadium pentoxide@carbon nanomaterial powder is coated on the surface of the magnesium hydride nanomaterial powder; The preparation method of vanadium pentoxide@carbon nanomaterial powder is as follows: accordion-shaped multilayer V 2 C nanomaterial powder was intercalated and ultrasonically exfoliated to obtain few-layer V 2 C nanomaterial, continue to calcine at 300-600°C for 15-25h in a carbon dioxide atmosphere to obtain vanadium pentoxide@carbon nanomaterial powder; The mass percentage of vanadium pentoxide@carbon nanomaterial powder in the magnesium hydride-vanadium pentoxide@carbon composite hydrogen storage material is 0.1-15wt.%.

2. The composite hydrogen storage material according to claim 1, It is characterized in that The mass percentage of vanadium pentoxide@carbon nanomaterial powder in the magnesium hydride-vanadium pentoxide@carbon composite hydrogen storage material is 3-12wt.%.

3. The composite hydrogen storage material according to claim 1, It is characterized in that The mass percentage of vanadium pentoxide@carbon nanomaterial powder in the magnesium hydride-vanadium pentoxide@carbon composite hydrogen storage material is 3-9wt.%.

4. The composite hydrogen storage material according to claim 1, It is characterized in that The average particle size of the magnesium hydride-vanadium pentoxide@carbon composite hydrogen storage material is 2-5 μm.

5. The composite hydrogen storage material according to claim 1, It is characterized in that The particle size of the magnesium hydride nanomaterial powder is 10-30 μm; the vanadium pentoxide@carbon nanomaterial powder is a nano-sheet structure powder with a diameter of 100-600 nm and a layer thickness of 2-10 nm.

6. The method for preparing the composite hydrogen storage material according to any one of claims 1 to 5, It is characterized in that The preparation method comprises the following steps: (1) Preparation of vanadium pentoxide@carbon nanomaterial powder: The accordion-shaped multilayer V 2 C nanomaterial powder was intercalated and ultrasonically exfoliated to obtain few-layer V 2 C nanomaterial, continue to calcine at 300-600°C for 15-25h in a carbon dioxide atmosphere to obtain vanadium pentoxide@carbon nanomaterial powder; (2) Preparation of composite hydrogen storage material: Mix vanadium pentoxide@carbon nanomaterial powder and magnesium hydride nanomaterial powder, and then perform ball milling to obtain composite hydrogen storage material.

7. The preparation method according to claim 6, It is characterized in that The few layers of V 2 The specific preparation method of C nanomaterials is: 2 AlC powder was added into a mixed acid solution formed by mixing hydrofluoric acid and hydrochloric acid, and etched at 50-60°C for 1-3 days to obtain an accordion-shaped multilayer V 2 C nanomaterial powder, continue to add tetrabutylammonium hydroxide solution and stir at room temperature for 1-2 days, and prepare a few-layer V 2 C nanomaterials; The mass fraction of the hydrofluoric acid is 49%, the mass fraction of the hydrochloric acid is 36-38%, and the volume ratio of the hydrofluoric acid to the hydrochloric acid in the mixed acid solution is 3:2; The mass fraction of tetrabutylammonium hydroxide in the tetrabutylammonium hydroxide solution is 5%; The V 2 The mass volume ratio of AlC powder, hydrofluoric acid and hydrochloric acid is 2:30:20, g:ml:ml; The V 2 The mass volume ratio of AlC powder and tetrabutylammonium hydroxide solution is 2:10~25, g:ml.

8. The preparation method according to claim 6, It is characterized in that In step (2), the specific conditions of the ball milling are: stainless steel balls are used as ball milling beads under a protective atmosphere, the ball-to-material ratio is 20-60:1, the ball milling method is forward and reverse intermittent ball milling, the ball milling time is 4-24 hours, and the ball mill revolution speed is 300-500 rpm.

9. The preparation method according to claim 8, It is characterized in that The ball-to-material ratio is 40:1, the ball milling time is 12 hours, and the ball mill revolution speed is 400 rpm.

10. Use of the composite hydrogen storage material according to any one of claims 1 to 5 in the storage and transportation of hydrogen.

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