Method for improving hydrogen storage performance of MgH2 based on catalysis of graphene oxide loaded green sulfur stone

Abstract

The invention relates to the field of solid hydrogen storage materials, in particular to a method for improving the hydrogen storage performance of MgH2 on the basis of catalysis of graphene oxide loaded green sulfur stone. According to the preparation method, a GO (at) VS4 nano-particle composite material catalyst is synthesized through a hydrothermal method assisted by ionic liquid chlorinated 1-butyl-3-methylimidazolium salt ([BMIm] Cl), and then GO (at) VS4 doped MgH2 is prepared through a ball milling method. According to the present invention, the prepared transition metal sulfide catalyst cupredite has unsaturated d electrons and high conductivity, the graphene oxide loaded cupredite (GO (at) VS4) catalyst is introduced into MgH2, such that the kinetic stability and the cycle stability of the hydrogen absorption and desorption reaction of MgH2 can be effectively improved, the hydrogen desorption kinetic activation energy of MgH2 is reduced to 63.8 kJ / mol from 122.7 kJ / mol, and the mass hydrogen desorption capacity remains unchanged after 100 cycles. The preparation process is simple, has low requirements on equipment, is easy to operate and has a commercial application prospect.

Description

Technical Field

[0001] The present invention relates to the field of solid-state hydrogen storage materials, and in particular to a method for improving the hydrogen storage performance of MgH2 based on the catalysis of graphene oxide loaded with vanadium sulfide. Technical Background

[0002] As a new type of energy with high reserves, high energy density, clean and environmentally friendly, and renewable, hydrogen energy has become an important development direction to replace fossil fuels. At present, the large-scale utilization of hydrogen energy mainly involves three nodes: hydrogen preparation, storage, and application. The development of safe, efficient, and economical hydrogen storage technology is one of the bottlenecks for the large-scale application of hydrogen energy. Hydrogen storage technology can be divided into high-pressure gaseous hydrogen storage, low-temperature liquid hydrogen storage, and solid-state hydrogen storage. Compared with high-pressure gaseous hydrogen storage materials, solid-state hydrogen storage materials have high safety, good stability, large hydrogen storage capacity, and low hydrogen storage and hydrogenation costs. They are bound to become the most ideal materials for hydrogen storage systems for large-scale applications of hydrogen energy in the future. At present, the research on solid-state hydrogen storage materials continues to develop towards lightweight and high-capacity hydride hydrogen storage systems with high hydrogen storage density, mainly including light metal hydrides. The mass hydrogen storage density of MgH2 is 7.6wt%, and it also has good reversibility, abundant sources, and low cost. It is currently a hot spot in the research of light metal hydrides.

[0003] However, commercial MgH2 dehydrogenation needs to be carried out at temperatures above 300°C, and during the hydrogen absorption and dehydrogenation cycle, there will be a significant attenuation of hydrogen storage capacity. Therefore, to use it as a commercial hydrogen storage material, it is necessary to solve the problems of high dehydrogenation temperature and cyclic stability decay. The main reasons for the high dehydrogenation reaction temperature of MgH2 include the increase in the thermodynamic endothermic enthalpy of dehydrogenation and the slow dehydrogenation kinetics. Introducing a catalyst is one of the effective means to solve the kinetic problems faced by MgH2 dehydrogenation.

[0004] Among many catalysts, vanadium is beneficial to the dehydrogenation of MgH2. Therefore, the prior art has already combined transition metal vanadium-based catalysts with MgH2 to solve the kinetic problems faced by MgH2 dehydrogenation. At present, the research on vanadium-based catalysts mainly includes: introducing vanadium-based oxides and bimetallic salts through ball milling to reduce the reversible hydrogen absorption and desorption temperature of MgH2. For example, in the document with application number "202310745955.9", a method for catalyzing vanadium oxide (vanadium pentoxide @ carbon, V2O5@C) to improve the hydrogen storage performance of MgH2 is disclosed; in the document with application number "202410670564.X", a method for catalyzing copper vanadate to improve the hydrogen storage performance of MgH2 is disclosed. However, the problem with the above scheme is that the low electronic conductivity oxygen-containing catalyst will react with MgH2 to form MgO during the process of MgH2 dehydrogenation, reducing the hydrogen storage capacity of the system, while the dehydrogenation temperature is high and the cycle stability declines. Therefore, it is very necessary to develop some other vanadium-based compound catalysts. Summary of the invention

[0005] In order to solve the problems of high hydrogen desorption temperature, cyclic stability degradation and low hydrogen storage capacity in the prior art, the present invention provides a method for improving the hydrogen storage performance of MgH2 based on graphene oxide loaded green sulfur vanadium catalysis.

[0006] In order to achieve the purpose of the present invention, the present invention provides a method for improving the hydrogen storage performance of MgH2 based on graphene oxide (GO) loaded with green sulfur vanadium (VS4) catalysis, comprising the following steps:

[0007] Step 1: GO and 1-butyl-3-methylimidazolium chloride ([BMIm]Cl) are uniformly dispersed in deionized water by ultrasonication to obtain a mixed solution;

[0008] Step 2: Na3VO4·12H2O and C2H5NS(TAA) are added to the mixed solution, and the stirred mixed solution is transferred into a reactor for hydrothermal reaction.

[0009] Step 3: After the reaction solution is cooled to room temperature, the product is collected by centrifugation, washed several times with deionized water and anhydrous ethanol, and vacuum dried at 60°C to obtain a catalyst labeled GO@VS4.

[0010] Step 4: Mix MgH2 and the prepared GO@VS4 catalyst and ball mill them to prepare a composite material of MgH2 and GO@VS4.

[0011] In the above step 4, the mass ratio of MgH2 and GO@VS4 is 80-95:5-20.

[0012] In the above step 4, the preferred mass ratio of MgH2 and GO@VS4 is 85:15.

[0013] In the above step 1, 15 mg of GO and 2 mmol of 1-butyl-3-methylimidazolium chloride ([BMIm]Cl) were uniformly dispersed in 15 mL of deionized water by ultrasonication for 6 h.

[0014] In the above step 1, ultrasonication is performed for 5-8 hours.

[0015] In the above step 2, 0.5 mmol of Na3VO4·12H2O and 10 mmol of C2H5NS(TAA) were successively added to the mixed solution, and stirring was continued for 1-2 h.

[0016] In the above step 2, the hydrothermal reaction temperature is 160-180°C and the time is 20-24h.

[0017] In the above step 4, MgH2 and GO@VS4 are loaded into a ball mill, filled with 50 bar hydrogen and then ball milled. A bidirectional operation mode is adopted during ball milling, first rotating forward for 12 minutes, then pausing for 6 minutes, then reversing for 12 minutes, and then pausing for 6 minutes, and repeating this cycle.

[0018] In the above step 4, the ball milling speed is 400 rpm, and the mass ratio of grinding balls to materials is 120:1.

[0019] In the above step 4, the ball milling beads are made of stainless steel and come in three sizes with diameters of 16 mm, 12 mm and 6 mm, respectively, in a weight ratio of 51:42:27.

[0020] Compared with the prior art, the advantages of the present invention are:

[0021] 1) Vanadium sulfide has higher electronic conductivity than vanadium oxide and vanadium-containing salts, and does not generate MgO during the process of hydrogen absorption and desorption, which can improve the hydrogen storage performance of MgH2 while improving its hydrogen storage capacity.

[0022] 2) The present invention synthesizes GO@VS4 nanoparticle composite catalyst by a hydrothermal method assisted by ionic liquid 1-butyl-3-methylimidazolium chloride ([BMIm]Cl). The size of VS4 nanoparticles can be controlled to about 10 nm by a hydrothermal method assisted by ionic liquid 1-butyl-3-methylimidazolium chloride ([BMIm]Cl).

[0023] 3) The transition metal sulfide catalyst vanadium sulfide prepared by the present invention has unsaturated d electrons and high conductivity. By introducing graphene oxide-loaded vanadium sulfide (GO@VS4) catalyst into MgH2, the kinetics of hydrogen absorption and desorption reactions and the cycle stability of MgH2 can be effectively improved. The kinetic activation energy of hydrogen desorption of MgH2 is reduced from 122.7 kJ / mol to 63.8 kJ / mol, and the mass hydrogen desorption capacity remains unchanged after 100 cycles.

[0024] 4) The preparation process of the catalyst and the corresponding composite material provided by the present invention is simple, has low requirements on equipment, and is easy to operate;

[0025] 5) The obtained composite material has excellent hydrogen release performance and stable cycle performance, and has commercial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is the SEM image of GO@VS4 catalyst;

[0027] Figure 2 is the XRD pattern of GO@VS4 catalyst;

[0028] Figure 3is the TEM image of GO@VS4 catalyst;

[0029] Figure 4 is the HRTEM of GO@VS4 catalyst;

[0030] Figure 5 is the SEM image of MgH2-10wt%GO@VS4;

[0031] Figure 6 is the SEM image of MgH2-15wt%GO@VS4;

[0032] Figure 7 are the XRD patterns of pristine MgH2, GO@VS4, MgH2-10wt%GO@VS4, and MgH2-10wt%GO@VS4;

[0033] Figure 8 It is the temperature-dependent hydrogen release performance diagram of the original MgH2, the composite materials with 10wt% GO@VS4 and 15wt% GO@VS4 added;

[0034] Fig. 9 are the DSC curves of original MgH2 and MgH2-15wt% GO@VS4;

[0035] Fig.10 It is the isothermal hydrogen desorption performance diagram of MgH2-15wt%GO@VS4;

[0036] Fig.11 This is the hydrogen release performance diagram of MgH2-15wt%GO@VS4100 cycles;

[0037] Fig.12 is the activation energy of the original MgH2 and MgH2-15wt% GO@VS4 samples;

[0038] Fig.13 This is the XRD spectrum of the sample of MgH2-15wt%GO@VS4 after the first dehydrogenation, the second dehydrogenation, and the dehydrogenation after 100 cycles;

[0039] Fig.14 This is the XRD spectrum of the MgH2-15wt% GO@VS4 sample after the first hydrogen absorption, the second hydrogen absorption, and 100 cycles of hydrogen absorption. Specific implementation methods

[0041] The technical solution of the present invention is further illustrated below through specific embodiments and drawings.

[0042] The preparation process of the present invention is: synthesizing a GO@VS4 nanoparticle composite material catalyst by an ionic liquid-assisted hydrothermal method, and then preparing GO@VS4-doped MgH2 by a ball milling method.

[0043] Example 1: A method for improving the hydrogen storage performance of MgH2 based on graphene oxide supported green sulfur vanadium catalysis provided by the present invention comprises the following steps:

[0044] Step 1: 15 mg of GO and 2 mmol of 1-butyl-3-methylimidazolium chloride ([BMIm]Cl) were uniformly dispersed in 15 mL of deionized water by ultrasonication for 6 h to obtain a mixed solution.

[0045] Step 1: 0.5 mmol of Na3VO4·12H2O and 10 mmol of C2H5NS(TAA) were successively added to the mixed solution, and after stirring for 1 hour, the formed mixed solution was transferred to a 30 mL stainless steel reactor lined with polytetrafluoroethylene, and reacted at 160°C for 24 hours to obtain a reaction solution.

[0046] Step 3: After the reaction solution is cooled to room temperature, the product is collected by centrifugation, washed several times with deionized water and anhydrous ethanol, and dried in vacuum at 60°C. The obtained catalyst is marked as GO@VS4.

[0047] like Figure 1 As shown, VS4 nanoparticles are tightly attached to the wrinkled and curled graphene oxide (GO) nanosheets, with clear gaps between the particles.

[0048] The phase and purity of GO@VS4 composites were characterized by XRD, such as Figure 2 As shown, the diffraction peak at about 26.5° is the diffraction peak of GO, and the other diffraction peaks correspond to VS4 (JCPDS No. 87-0603), and no diffraction peaks of other substances are observed.

[0049] like Figure 3 As shown, the low-magnification TEM images further demonstrate that a large number of highly dispersed VS4 nanoparticles are anchored on the GO nanosheets.

[0050] like Figure 4 As shown, the HRTEM images show that the size of VS4 nanoparticles is about 10 nm.

[0051] Step 4: Weigh MgH2 at a mass ratio of 90:10 and put it into a ball mill with the GO@VS4 catalyst prepared in step 3, fill it with 50 bar hydrogen and then perform ball milling to prepare a sample labeled as MgH2-10wt%GO@VS4 (see Figure 5). The ball mill adopts a two-way operation mode, first forward for 12 minutes, then pause for 6 minutes, then reverse for 12 minutes, and then pause for 6 minutes, and repeat this cycle. The ball mill speed is 400rpm, and the mass ratio of grinding balls to materials is 120:1. The ball mill jar is made of stainless steel, with a volume of about 170mL. A valve is connected to the lid for easy filling and discharging of gas. The ball mill beads used are also made of stainless steel. There are three sizes, with diameters of 16mm, 12mm and 6mm respectively. According to the mass ratio of 51:42:27, the total mass is weighed to be 120g.

[0052] Example 2, the present invention provides a method for improving the hydrogen storage performance of MgH2 based on the catalysis of graphene oxide supported by green sulfur vanadium, comprising the following steps:

[0053] Step 1 to step 3 are the same as in Example 1;

[0054] Step 4: Weigh MgH2 and the GO@VS4 catalyst prepared in step 3 at a mass ratio of 85:15, and prepare the sample MgH2-15wt% GO@VS4 according to step 4 of Example 1 (see Figure 6 ).

[0055] The preparation process of MgH2 is as follows:

[0056] Take 6 grams of Mg powder and put it into the reactor. Connect the reactor with Mg powder to the hydrogen storage test stand for synthesizing MgH2, evacuate for half an hour, fill with hydrogen to 50 bar, heat to 580°C, keep warm for 2 hours, then slowly cool to 340°C and keep warm for 8 hours. Transfer the powder in the reactor to the ball mill, fill the ball mill with hydrogen to 50 bar, ball milling parameters: 400rpm, 8 hours. Put the ball-milled powder back into the reactor and connect it to the dedicated hydrogen storage test stand for synthesizing MgH2 again, and fill with hydrogen to 50 bar after evacuating. Heat to 380°C and keep warm for 12 hours to prepare the original MgH2, marked as Pristine MgH2.

[0057] Figure 7 The XRD spectra show that after ball milling, the XRD diffraction peaks of MgH2-10wt% GO@VS4 and MgH2-15wt% GO@VS4 samples completely match the diffraction peaks of MgH2.

[0058] See also Figure 8, the main dehydrogenation of the original MgH2 is concentrated between 320 and 380 ° C. Adding 10wt% GO@VS4 catalyst can reduce the dehydrogenation temperature range of MgH2 to 250-350 ° C, which is 70 ° C lower than the original MgH2, and the dehydrogenation amount at 400 ° C is about 6.5wt%. Adding 15wt% GO@VS4 catalyst can reduce the dehydrogenation temperature range of MgH2 to 180-320 ° C, which is 140 ° C lower than the original MgH2, and the dehydrogenation amount when heated to 400 ° C is about 6.2wt%.

[0059] Since the performance of the composite material with 15wt% GO@VS4 catalyst added is better than that of the composite material with 10wt% GO@VS4 catalyst added, it can be seen that Example 2 is the best. Therefore, the hydrogen desorption performance and reaction mechanism of the composite material of Example 2-with 15wt% GO@VS4 catalyst added are further analyzed.

[0060] Depend on Fig. 9 It can be seen that the addition of GO@VS4 can significantly reduce the dehydrogenation temperature of MgH2. The original MgH2 without catalyst starts to dehydrogenate from ~320℃, with a peak temperature of 348℃. After adding 15wt% GO@VS4 catalyst, the peak temperature of the main dehydrogenation peak of MgH2 is 220℃, which is 128℃ lower than that of the original MgH2. Fig.10 , at 270 °C, the MgH2-15wt% GO@VS4 sample can quickly release 5wt% H2 within 10 min.

[0061] See also Fig.11 After 100 cycles, the hydrogen release amount of the sample was 6.1wt%, showing good cycle stability.

[0062] The activation energy of hydrogen desorption of pristine MgH2 and GO@VS4 modified MgH2 was calculated using the Kissinger method. Fig.12 The DSC curves of the two samples at different heating rates are shown in Figure 2. As the heating rate increases, the hydrogen desorption curve of the sample gradually shifts to high temperature. According to the Kissinger equation, the activation energy of hydrogen desorption of the original MgH2 is 122.7 kJ / mol, while the activation energy of hydrogen desorption of the MgH2-15wt% GO@VS4 sample is 63.8 kJ / mol, which is only 52% of the original MgH2. Therefore, the GO@VS4 catalyst greatly improves the hydrogen absorption and desorption kinetics of MgH2.

[0063] See also Fig.13In the XRD patterns of all samples after dehydrogenation, hexagonal Mg was the main phase, and MgS and MgO diffraction peaks were observed. During the first dehydrogenation process, VS4 and MgH2 reacted to form MgS. In addition, compared with the first dehydrogenation sample, the diffraction peaks of the samples after dehydrogenation after 100 cycles were basically not shifted, indicating that the addition of catalysts can reduce the operating temperature of the sample during the cycle, inhibit the grain growth of the sample and the agglomeration growth of the particles, and thus improve the cycle stability of the sample.

[0064] See also Fig.14 In the XRD patterns of all samples after hydrogen absorption, the hexagonal MgH2 phase is the main phase, and the diffraction peaks of MgS and MgO are observed at the same time. The MgS generated by the first hydrogen release is stable in the entire hydrogen absorption and desorption process. In addition, compared with the first hydrogen absorption sample, the diffraction peaks of the hydrogen absorption sample after 100 cycles are basically not offset, indicating that the addition of catalysts can reduce the operating temperature of the sample during the cycle, inhibit the grain growth of the sample and the agglomeration growth of the particles, and thus improve the cycle stability of the sample.

[0065] The above are only specific embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for improving the hydrogen storage performance of MgH2 based on graphene oxide supported green sulfur vanadium catalysis, characterized in that: The following steps are involved: Step 1: GO and 1-butyl-3-methylimidazolium chloride are uniformly dispersed in deionized water by ultrasonication to obtain a mixed solution; Step 2: Na3VO4·12H2O and C2H5NS are added to the mixed solution, and the stirred mixed solution is transferred to a reactor for hydrothermal reaction; Step 3: After the reaction solution is cooled to room temperature, the product is collected by centrifugation, washed several times with deionized water and anhydrous ethanol, and dried under vacuum at 60°C to obtain a catalyst labeled GO@VS4; Step 4: Mix MgH2 and the prepared GO@VS4 catalyst and ball mill them to prepare a composite material of MgH2 and GO@VS4.

2. A method for improving the hydrogen storage performance of MgH2 based on graphene oxide supported green sulfur vanadium catalysis according to claim 1, characterized in that: In the step 4, the mass ratio of MgH2 to GO@VS4 is 80-95:5-20.

3. The method for improving the hydrogen storage performance of MgH2 based on graphene oxide supported vanadium sulfate catalysis according to claim 1, characterized in that: In the step 4, the mass ratio of MgH2 and GO@VS4 is preferably 85:

15.

4. The method for improving the hydrogen storage performance of MgH2 based on graphene oxide supported vanadium sulfate catalysis according to claim 1, characterized in that: In the step 1, 15 mg of GO and 2 mmol of chloro-1-butyl-3-methylimidazolium salt were uniformly dispersed in 15 mL of deionized water by ultrasonication for 6 h.

5. The method for improving the hydrogen storage performance of MgH2 based on graphene oxide supported vanadium sulfate catalysis according to claim 1, characterized in that: In the step 1, ultrasonication is performed for 5-8 hours.

6. The method for improving the hydrogen storage performance of MgH2 based on graphene oxide supported vanadium sulfate catalysis according to claim 1, characterized in that: In the step 2, 0.5 mmol of Na3VO4·12H2O and 10 mmol of C2H5NS were successively added to the mixed solution, and stirring was continued for 1-2 h.

7. The method for improving the hydrogen storage performance of MgH2 based on graphene oxide supported vanadium sulfate catalysis according to claim 1, characterized in that: In the step 2, the hydrothermal reaction temperature is 160-180°C and the reaction time is 20-24 h.

8. The method for improving the hydrogen storage performance of MgH2 based on graphene oxide supported vanadium sulfate catalysis according to claim 1, characterized in that: In the step 4, MgH2 and GO@VS4 are loaded into a ball milling tank, filled with 50 bar hydrogen and then ball milled. A bidirectional operation mode is adopted during ball milling, first forward rotation for 12 min, then pause for 6 min, then reverse rotation for 12 min, and then pause for 6 min, and this cycle is repeated.

9. The method for improving the hydrogen storage performance of MgH2 based on graphene oxide supported vanadium sulfate catalysis according to claim 1, characterized in that: In the step 4, the ball milling speed is 400 rpm, and the mass ratio of grinding balls to materials is 120:

1.

10. The method for improving the hydrogen storage performance of MgH2 based on graphene oxide supported vanadium sulfate catalysis according to claim 1, characterized in that: In step 4, the ball milling beads are made of stainless steel and are available in three sizes with diameters of 16 mm, 12 mm and 6 mm, respectively, in a weight ratio of 51:42:27.

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