A borohydride / graphyne composite hydrogen storage material and a preparation method and application thereof
By loading borohydrides onto graphdiyne supports to form composite hydrogen storage materials, the problem of limited hydrogen absorption and desorption performance of light metal borohydrides has been solved, achieving efficient and reversible hydrogen storage performance at low temperatures and improving the kinetic and thermodynamic properties of the materials.
Patent Information
- Application Number
- CN202311518762.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-11-15
- Publication Date
- 2026-01-13
- Estimated Expiration
- 2043-11-15
AI Technical Summary
In the prior art, the hydrogen absorption and desorption performance of light metal borohydrides such as magnesium borohydride is limited by high thermodynamic stability, harsh hydrogen absorption and desorption conditions, and poor reversibility, which leads to a decline in their cycle performance in practical applications.
Using graphyne as a carrier, borohydride is loaded through nanoconfining technology to form a borohydride/graphyne composite hydrogen storage material. By utilizing the highly conjugated two-dimensional planar structure and large specific surface area of graphyne, the structural morphology of borohydride is optimized to achieve uniform distribution of nanoparticles and improved stability.
Graphdiyne composite hydrogen storage materials significantly reduce the initial hydrogen release temperature, improve hydrogen absorption and desorption kinetics and reversibility, significantly enhance cycle performance, lower the hydrogen release temperature to below 100℃, improve cycle reversibility, and achieve a capacity retention rate of over 87%.
Smart Images
Figure CN117550550B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of borohydride composite hydrogen storage materials, specifically to a borohydride / graphyne composite hydrogen storage material, its preparation method, and its application. Background Technology
[0002] Hydrogen energy is considered one of the most promising clean energy sources for the future due to its large reserves, high energy density, and environmental friendliness; however, the safe and efficient use of hydrogen energy is the key factor limiting its practical application. Storing hydrogen in solid-state media is one of the most efficient and safest methods for widespread hydrogen utilization in the future. Among them, light metal borohydrides have attracted widespread attention due to their extremely high hydrogen storage capacity. For example, magnesium borohydride has an extremely high mass density (14.9 wt%) and the highest volumetric hydrogen storage density (145–147 kg / m³). 3 However, magnesium borohydride has harsh hydrogen absorption and desorption conditions, and its high thermodynamic stability, poor hydrogen absorption and desorption kinetics, and poor reversibility severely limit its practical applications.
[0003] To improve the hydrogen storage performance of magnesium borohydride, current methods mainly include catalyst doping, metal hydride composites, nanoconfinement, and forward / reverse coupling instability. Catalytic modification significantly reduces the activation energy for hydrogen desorption, but still suffers from poor reversibility and difficulty in cycling hydrogen. Metal hydride composites can destabilize the magnesium borohydride reaction, thereby reducing thermodynamic stability and hydrogen desorption temperature; however, stable byproducts are easily generated during hydrogen desorption, leading to decreased cycling performance. Forward / reverse coupling instability can alter the reaction pathway of magnesium borohydride, reducing thermodynamic stability and enabling hydrogen desorption under milder conditions; however, this reaction is irreversible and can only be used as a primary energy source. Nanoconfinement can increase the active sites of magnesium borohydride, enhance its interaction with the support, and effectively shorten the hydrogen diffusion path, improving the hydrogen absorption and desorption performance of magnesium borohydride and achieving dual thermodynamic and kinetic regulation.
[0004] Graphdiyne is a two-dimensional planar network structure formed by inserting alkyne bonds between two benzene rings in the graphene structure, exhibiting high carrier mobility (10⁴–10⁵ cm⁻¹) at room temperature. 2 V -1 s -1 It is the most stable non-natural carbon allotrope containing alkyne bonds.
[0005] Currently, various carbon materials have been used as supports for the nanoconfinement of magnesium borohydride. Early methods involved the in-situ synthesis of magnesium borohydride in activated carbon for nanoconfinement, effectively lowering the initial hydrogen desorption temperature to 160℃ and the activation energy to 102 kJ / mol, significantly improving hydrogen desorption kinetics. However, the loading process inevitably produces MgB2O3. 12 H 12This resulted in low cycle reversibility and poor hydrogen reabsorption (J. Mater. Chem. A, 2013, 1, 11177-11183). Subsequently, a similar method was used to synthesize magnesium borohydride in situ on graphene to achieve nano-confinence, effectively reducing the initial hydrogen desorption temperature to 154℃, shortening the hydrogen diffusion path through nano-sizing, and significantly improving the hydrogen desorption rate. However, its cycle reversibility was not significantly improved, and the capacity retention rate was only 38% after 3 cycles (Adv. Energy Mater. 2018, 8, 1702975).
[0006] In summary, developing a composite hydrogen storage material system loaded with borohydrides to further improve the hydrogen absorption and desorption performance of the light metal magnesium borohydride is of great significance for the development of high-capacity hydrogen storage materials. Summary of the Invention
[0007] To address the aforementioned technical problems and shortcomings in this field, this invention provides a borohydride / graphyne composite hydrogen storage material. This material is a (light metal) borohydride composite hydrogen storage material with optimized and controlled morphology using graphyne. Using graphyne as a carrier ensures stability during the hydrogen absorption and desorption cycle of the borohydride. The borohydride / graphyne composite hydrogen storage material of this invention exhibits low hydrogen desorption onset and peak temperatures, good hydrogen absorption and desorption kinetics, and high reversibility.
[0008] A borohydride / graphyne composite hydrogen storage material includes a graphyne support and a borohydride loaded on the support.
[0009] In one embodiment, the borohydride is loaded onto the support in the form of nanoparticles. The size of the nanoparticles can be 10–100 nm.
[0010] In one embodiment, the borohydride is magnesium borohydride.
[0011] In one embodiment, the graphyne is graphdiyne, which has a nanowall morphological structure and the diameter of the formed pores is 100-400 nm.
[0012] In one embodiment, the mass ratio of the graphodyne to the borohydride is 1:1 to 2.
[0013] The present invention also provides a method for preparing the aforementioned borohydride / graphyne composite hydrogen storage material, wherein graphyne is added to a homogeneous solution of borohydride and ultrasonically dispersed, and then, while keeping the graphyne suspended, part of the solvent is evaporated to form a paste, and finally, the solvent is removed by vacuum to obtain the aforementioned borohydride / graphyne composite hydrogen storage material.
[0014] The preparation method of this invention can achieve nano-confinence of borohydrides on graphyne, and the borohydride nanoparticles are uniformly distributed on the surface of graphyne, resulting in a significant improvement in hydrogen absorption and desorption performance.
[0015] The borohydride described in this invention can be obtained commercially or prepared according to existing technology.
[0016] The graphdiyne described in this invention can be obtained commercially or prepared according to existing techniques. For example, the graphdiyne can be prepared by referring to existing techniques (e.g., J. Am. Chem. Soc. 2015, 137, 24, 7596-7599).
[0017] In one embodiment, the solvent in the homogeneous solution of the borohydride is a solvent soluble in the borohydride, where soluble means that the solubility of the substance at 20°C is greater than or equal to 1g and less than 10g.
[0018] In one embodiment, the solvent is an organic solvent. Further, the solvent may be selected from at least one of tetrahydrofuran, trimethylamine, triethylamine, tetramethylenediamine, and diethyl ether.
[0019] In one embodiment, the preparation method is operated at a temperature of room temperature to 50°C.
[0020] The preparation method described above allows graphylene to be kept in suspension through continuous stirring. In one embodiment, the stirring speed is 150–300 rpm.
[0021] In one embodiment, the evaporation time is 8 to 12 hours.
[0022] In one embodiment, the vacuuming time is 48–72 hours.
[0023] The present invention also provides the application of the borohydride / graphyne composite hydrogen storage material in the field of hydrogen storage.
[0024] Compared with the prior art, the beneficial effects of this invention are as follows:
[0025] 1) The present invention provides a borohydride / graphyne composite hydrogen storage material, which for the first time applies graphyne to improve the performance of hydrogen storage materials. Graphyne has a highly conjugated two-dimensional planar structure, which can effectively improve the ion diffusion rate, thereby improving the hydrogen absorption and desorption kinetics of magnesium borohydride.
[0026] 2) Compared to typical carbon nanostructure materials, graphdiene is composed of sp and sp 2The unique electronic structure formed by hybridization possesses abundant carbon chemical bonds, a large conjugated system, wide interfacial spacing, and excellent chemical stability. It also exhibits a larger specific surface area and higher porosity, effectively limiting the particle radius during in-situ growth of borohydrides. After loading, the borohydrides are distributed as uniformly dispersed nanoparticles on graphyne, which is highly beneficial for the interlayer diffusion and mass transport of borohydride ions. The excellent nanoconfining effect shortens the hydrogen diffusion path, lowers the hydrogen desorption energy barrier, and significantly advances the hydrogen desorption temperature. The composite material's initial hydrogen desorption temperature can be below 100℃, making it even more promising for applications.
[0027] 3) Graphdiyne has a stable structure and can effectively anchor borohydride nanoparticles during hydrogen absorption and desorption cycles, inhibiting their aggregation; at the same time, it is closely linked with borohydride to prevent the formation of a stable intermediate phase during hydrogen reabsorption, thus jointly promoting a significant improvement in cycle reversibility. Attached Figure Description
[0028] Figure 1 The hydrogen release curves of the magnesium borohydride / graphyne composite hydrogen storage material and magnesium borohydride obtained in Example 1 are shown.
[0029] Figure 2 The hydrogen release curves of the magnesium borohydride / graphyne composite hydrogen storage material and magnesium borohydride obtained in Example 2 are shown.
[0030] Figure 3 The figure shows the hydrogen desorption curve at 300°C for the magnesium borohydride / graphyne composite hydrogen storage material obtained in Example 2.
[0031] Figure 4 This is a graph showing the capacity curve of the magnesium borohydride / graphyne composite hydrogen storage material obtained in Example 2 after 10 hydrogen desorption cycles.
[0032] Figure 5 The image shows a scanning electron microscope (SEM) image of the magnesium borohydride / graphyne composite hydrogen storage material obtained in Example 2.
[0033] Figure 6 SEM image of the magnesium borohydride / graphyne composite hydrogen storage material obtained in Example 2;
[0034] Figure 7 This is a transmission electron microscope (TEM) image of the magnesium borohydride / graphyne composite hydrogen storage material obtained in Example 2;
[0035] Figure 8 The images show the infrared spectra of the magnesium borohydride / graphyne composite hydrogen storage material obtained in Example 2 under different conditions. Detailed Implementation
[0036] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.
[0037] Unless otherwise specified, the operating methods in the following examples are generally performed under conventional conditions or as recommended by the manufacturer.
[0038] The graphyne in the following embodiments is graphdiyne, which has a nanowall morphological structure and forms pores with diameters ranging from 100 to 400 nm. The specific preparation process is described below:
[0039] 50 mg of HEB-TMS (hexa(trimethylsilylethynyl)benzene, CAS No. 100516-62-9) was dissolved in 15 mL of tetrahydrofuran (THF). Under an argon atmosphere and at 0 °C, 1 mL of tetrabutylammonium fluoride (TBAF) was added, and the mixture was stirred for 20 min. At this point, the mixture should be pale pink or purple depending on the purity of the reactants. Ethyl acetate was then added to dilute the solution to 30 mL. The diluted mixture was added to a separatory funnel and washed with 30 mL of saturated sodium chloride (NaCl) aqueous solution, followed by separation. The upper organic phase was collected, and the washing was repeated three times. Then, 20 mg of anhydrous MgSO4 was added to remove excess water, and the mixture was filtered. The filtered mixture was transferred to a rotary evaporator and evaporated at 40 °C to remove excess organic solvent, yielding hexaethynylbenzene (HEB, yellow solid). The entire process required protection from light.
[0040] Ten 2cm × 2cm copper foils, pre-prepared and acid-washed in 1mol / L hydrochloric acid solution for 24 hours, were sequentially ultrasonically cleaned for 20 minutes each in 1mol / L hydrochloric acid, water, anhydrous ethanol, and acetone (total 80 minutes). Then, the copper foils, along with 100mL acetone, 5mL pyridine, and 1mL tetramethylethylenediamine, were added sequentially to a foil-wrapped round-bottom flask and mixed under an argon atmosphere, heated to 50°C, and maintained for 1 hour. The prepared HEB was dissolved in 50mL acetone and then added to a constant-pressure separatory funnel. Over 4 hours, the solution in the separatory funnel was slowly added to the flask prepared in the previous step. After the addition was complete, the mixture was magnetically stirred and reacted at 50°C for over 36 hours to obtain a black suspension. This suspension was then centrifuged at 10000 rpm for 12 minutes, and the black precipitate was collected. The black precipitate was washed at least twice, sequentially with acetone, N,N-dimethylformamide (DMF), ethanol, and water, to remove excess organic matter (first centrifugation time 5 min, second centrifugation time 10 min, speed 9000 r / min). The washed black solid was then added to a round-bottom flask and acid-washed under reflux in 1 mol / L hydrochloric acid solution at 90 °C for 12 h. The mixture was cooled to room temperature, with continuous stirring during the acid washing and reflux process. The acid-washed product was then centrifuged with double-distilled water until the pH reached 7. The washed solid was dried in a vacuum drying oven at 70 °C for 7 h to obtain graphdiyne (GDY) for later use.
[0041] Example 1
[0042] 60 mg of magnesium borohydride powder was placed in a container, and 15 mL of tetrahydrofuran was added. The mixture was stirred at 150 rpm for 30 min at room temperature to obtain a magnesium borohydride tetrahydrofuran solution. 60 mg of graphyne was added to the above solution, and the mixture was ultrasonically dispersed for 30 min. The graphyne was then stirred at 150 rpm to keep it suspended, resulting in a suspension. The suspension was allowed to evaporate naturally for 12 h to remove most of the solvent and form a paste. The mixture was then vacuumed at room temperature for 72 h to remove all tetrahydrofuran, resulting in a magnesium borohydride / graphyne composite hydrogen storage material.
[0043] The hydrogen desorption performance of the material was tested using a volumetric hydrogen desorption method with an initial vacuum of 1×10⁻⁶. -3 Hydrogen release under bar conditions, heated to 500℃ at a heating rate of 5K / min, the hydrogen release curve is as follows. Figure 1 As shown, compared with pure magnesium borohydride, the large specific surface area and higher porosity of graphdiene result in a significant nanoconfining effect, which is beneficial for the diffusion and mass transport of borohydride ions between its layers. The hydrogen release temperature and the peak hydrogen release temperature of the loaded sample are significantly reduced, enabling magnesium borohydride to continuously release hydrogen at a lower temperature (about 90°C).
[0044] Example 2
[0045] 60 mg of magnesium borohydride powder was placed in a container, and 15 mL of tetrahydrofuran was added. The mixture was stirred at 150 rpm for 30 min at room temperature to obtain a magnesium borohydride tetrahydrofuran solution. 30 mg of graphyne was added to the above solution, and the mixture was ultrasonically dispersed for 30 min. The graphyne was then stirred at 150 rpm to keep it suspended, resulting in a suspension. The suspension was allowed to evaporate naturally for 12 h to remove most of the solvent and form a paste. The mixture was then vacuumed at room temperature for 72 h to remove the tetrahydrofuran, yielding a magnesium borohydride / graphyne composite hydrogen storage material, which can be denoted as 2 magnesium borohydride / graphyne.
[0046] The hydrogen desorption performance of the material was tested using a volumetric hydrogen desorption method with an initial vacuum of 1×10⁻⁶. -3 Hydrogen release under bar conditions, heated to 500℃ at a heating rate of 5K / min, the hydrogen release curve is as follows. Figure 2 As shown, comparing the hydrogen desorption curves of pure magnesium borohydride, it can be found that due to the large specific surface area and high porosity of graphdiyne, the nanoconfining effect is superior, significantly reducing the initial hydrogen desorption temperature of 2-Mg / Mg borohydride, which begins to significantly desorb hydrogen at 60℃, nearly 210℃ lower than the 270℃ initial hydrogen desorption temperature of pure magnesium borohydride. Simultaneously, graphdiyne possesses a highly conjugated two-dimensional planar structure, which effectively improves the ion diffusion rate and enhances the hydrogen absorption and desorption kinetics, advancing the peak hydrogen desorption temperature to 300℃ and lowering the hydrogen desorption energy barrier, allowing magnesium borohydride to continuously desorb hydrogen at lower temperatures.
[0047] It is evident that graphylene as a support in the composite hydrogen storage material of this invention can effectively reduce the decomposition energy barrier of magnesium borohydride, achieve nanoscale confinement, shorten the hydrogen diffusion path, and realize dual regulation of the thermodynamic kinetics of magnesium borohydride.
[0048] The hydrogen absorption and desorption cycle performance of 2-magnesium borohydride / graphyne was tested using the volumetric hydrogen desorption method. Figure 3 The hydrogen desorption cycle performance of 2-magnesium borohydride / graphyne at 300℃ is extremely fast in the first hydrogen desorption cycle, releasing nearly 10 wt% of hydrogen gas within 50 minutes. Although the hydrogen desorption cycle performance of the second hydrogen desorption cycle is relatively slowed down, it is almost stable. It is worth noting that the hydrogen absorption and desorption capacity retention rate is nearly 100% in the first three cycles. Figure 4 The results of 10 isothermal hydrogen absorption and desorption cycles at 300℃ are surprising. After 10 cycles, the capacity retention remained above 87%, and the kinetic decay was minimal. Compared to the extremely poor cycling performance of pure magnesium borohydride, the hydrogen absorption and desorption cycling performance of the composite hydrogen storage material obtained in this invention is significantly improved.
[0049] Figure 5 , Figure 6 The SEM images of magnesium borohydride / graphyne show that the graphyne mainly consists of nanowall structures with pore diameters ranging from 100 to 400 nm. Magnesium borohydride is uniformly dispersed on the graphyne as nanoparticles with diameters ranging from 10 to 100 nm, demonstrating excellent nanoconfining effect. Furthermore, the magnesium borohydride and graphyne are tightly bound together, with minimal agglomeration.
[0050] Figure 7 The TEM results for 2-magnesium borohydride / graphyne show that a large number of magnesium borohydride nanoparticles are uniformly loaded on the sheet-like graphyne.
[0051] Figure 8 The infrared spectra of magnesium borohydride / graphyne in different forms are shown, with the 2150-2400 cm⁻¹ range being the most significant. -1 An absorption peak corresponding to the BH bond stretching vibration in magnesium borohydride (Mg(BH4)2) appeared at the IR spectrum. Infrared results of the loaded sample show that the loaded 2-Mg borohydride / graphyne exhibits a BH bond stretching vibration peak, proving that magnesium borohydride was successfully generated in situ on graphyne. The 2-Mg borohydride / graphyne absorbs an absorption peak at 2150-2400 cm⁻¹ after hydrogen desorption. -1 The disappearance of the absorption peak and the regeneration of the BH bond stretching vibration absorption peak after hydrogen absorption prove that magnesium borohydride has a good regeneration effect, which is consistent with the results of cyclic hydrogen absorption and desorption.
[0052] Furthermore, it should be understood that after reading the above description of the present invention, those skilled in the art can make various alterations or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims.
Claims
1. A borohydride / graphyne composite hydrogen storage material, characterized in that, The invention comprises a graphyne support and a borohydride loaded on the support; the borohydride is magnesium borohydride; the borohydride is loaded on the support in the form of nanoparticles; the mass ratio of the graphyne to the borohydride is 1:
2.
2. The borohydride / graphyne composite hydrogen storage material according to claim 1, characterized in that, The size of the nanoparticles is 10–100 nm.
3. The borohydride / graphyne composite hydrogen storage material according to claim 1, characterized in that, The graphyne is graphdiyne, which has a nanowall morphological structure and forms pores with diameters ranging from 100 to 400 nm.
4. The method for preparing the borohydride / graphyne composite hydrogen storage material according to any one of claims 1 to 3, characterized in that, Graphdiyne was added to a homogeneous solution of borohydride and ultrasonically dispersed. Then, while keeping the graphdiyne suspended, some of the solvent was evaporated to form a paste. Finally, the solvent was removed by vacuum to obtain the borohydride / graphdiyne composite hydrogen storage material.
5. The preparation method according to claim 4, characterized in that, The solvent is an organic solvent selected from at least one of tetrahydrofuran, trimethylamine, triethylamine, tetramethylenediamine, and diethyl ether.
6. The preparation method according to claim 4, characterized in that, The preparation method operates at a temperature of room temperature to 50°C, and the graphylene is kept in suspension by continuous stirring. The stirring speed is 150 to 300 rpm, the volatilization time is 8 to 12 hours, and the vacuuming time is 48 to 72 hours.
7. The application of the borohydride / graphyne composite hydrogen storage material according to any one of claims 1 to 3 in the field of hydrogen storage.