NANO MAGNESIUM HYDRIDE AND IN-SITU PREPARATION METHOD THEREOF

Abstract

The invention discloses nano magnesium hydride and an in-situ preparation method thereof, including disposing and stirring magnesium chloride and lithium hydride in an organic solvent under a protection of an inert atmosphere, so as to obtain an organic suspension of a mixture; performing an ultrasonic treatment to the organic suspension, so as to promote a chemical reaction of the mixture. After the reaction is completed, the suspension is filtered; the solid reaction product is washed, centrifuged and dried to remove residual organic matter, so as to obtain nano-magnesium hydride.

Claims

1. An in-situ preparation method of nano magnesium hydride, comprising steps of: step (1) disposing and stirring magnesium chloride and lithium hydride in a first organic solvent under a protection of an inert atmosphere, so as to obtain an organic suspension of a mixture; step (2) performing an ultrasonic treatment to the organic suspension under the protection of the inert atmosphere, so as to promote a chemical reaction of the mixture, after the chemical reaction is completed, the organic suspension is filtered to obtain a solid reaction product; and step (3) washing, centrifuging and drying the solid reaction product by using a second organic solvent under the protection of the inert atmosphere, so as to remove a residual organic material and obtain nano-magnesium hydride.

2. The in-situ preparation method of nano magnesium hydride of claim 1, wherein in step (1), before disposing magnesium dichloride and lithium hydride in the first organic solvent, magnesium dichloride and lithium hydride are ball milled respectively to obtain post-milled magnesium dichloride and lithium hydride; a rotational speed of the ball milling is 100-400 revolutions/hour, and a time of the ball milling is 3-12 hours.

3. The in-situ preparation method of nano magnesium hydride of claim 1, wherein in step (1), magnesium dichloride is anhydrous, and a molar ratio of magnesium dichloride to lithium hydride is 1:2.

4. The in-situ preparation method of nano magnesium hydride of claim 1, wherein in step (1), the first organic solvent is ultra-dry tetrahydrofuran, ultra-dry cyclohexane, or ultra-dry ether.

5. The in-situ preparation method of nano magnesium hydride of claim 1, wherein step (1) is replaced by step (A); step (A) disposing and stirring magnesium dichloride, lithium hydride and transition metal chlorides in the first organic solvent to obtain the organic suspension; after step (2) and step (3) are performed, nano magnesium hydride is obtained; wherein the transition metal chlorides are anhydrous chlorides, including titanium tetrachloride, titanium trichloride, zirconium tetrachloride, vanadium trichloride, niobium pentachloride, nickel dichloride or cobalt dichloride.

6. The in-situ preparation method of nano magnesium hydride of claim 5, wherein a molar ratio of the transition metal chloride and magnesium chloride is 0.01-0.05:1; and a molar ratio of lithium hydride and chlorine ion in the transition metal chloride is 1:1.

7. The in-situ preparation method of nano magnesium hydride of claim 1, wherein in step (2), an ultrasonic output power is 100-600 W, a single ultrasound time is 0.5-1 h, a pause time is 10-30 min, and an overall ultrasound time is 3-24 h.

8. The in-situ preparation method of nano magnesium hydride of claim 1, wherein in step (2), an ultrasonic rod is inserted into the organic suspension for the ultrasonic treatment.

9. The in-situ preparation method of nano magnesium hydride of claim 1, wherein in step (3), the second organic solvent is ultra-dry tetrahydrofuran, or ultra-thy acetone, a washing time is 1-2 h, a drying treatment is achieved by heating under a protection of vacuum or inert atmosphere.

10. A nano magnesium hydride, prepared by the in-situ preparation method of nano magnesium hydride of claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] FIG. 1 shows (a) an EDS spectrum and (b) an XPS pattern of the nano magnesium hydride prepared in example 1;

[0039] FIG. 2 shows SEM images of the nano magnesium hydride prepared in example 1;

[0040] FIG. 3 shows (a) the TEM image and (b, c) the high-resolution TEM images of magnesium hydride nanoparticles prepared in example 1;

[0041] FIG. 4 shows the temperature-dependent degassing mass spectrum curves of the nano-magnesium hydride prepared in example 1: (a) hydrogen evolution curve and (b) tetrahydrofuran evolution curve;

[0042] FIG. 5 shows the temperature-dependent desorption mass spectrometry curves of the nano magnesium hydride prepared in example 1 and the magnesium hydrides prepared in controls 2 and 3;

[0043] FIG. 6 shows the XRD patterns of the nano magnesium hydride samples prepared by (a) example 1 and the nano magnesium hydride prepared by (b) controls 2 and 3 to different stages of dehydrogenation;

[0044] FIG. 7 shows (a) the EDS spectrum and (b) the XPS spectrums of Ti-catalyzed nano magnesium hydride prepared in example 2;

[0045] FIG. 8 shows (a) the TEM image and (b) the high-resolution TEM image of the Ti-catalyzed doped nano magnesium hydride prepared in example 2;

[0046] FIG. 9 shows the temperature-dependent desorption mass spectrometry curves of Ti-doped nano magnesium hydride prepared in example 2 and the TiCl.sub.4 doped nano magnesium hydride prepared in controls 2 and 3;

[0047] FIG. 10 shows the mass spectra of dehydrogenation of magnesium hydride with different amounts of Ti catalyst additions prepared in example 2 and control 6;

[0048] FIG. 11 shows the XRD patterns of the dehydrogenation products of magnesium hydride prepared in example 2 and control 6 with different amounts of Ti catalyst;

[0049] FIG. 12 shows (a) the EDS spectrum and (b) the V XPS spectrum of the nano magnesium hydride doped with vanadium prepared in example 3;

[0050] FIG. 13 shows the temperature-dependent desorption mass spectrometry curves of V-doped nano magnesium hydride prepared in example 3 and the VCl.sub.2 doped nano magnesium hydride prepared in controls 7 and 8;

[0051] FIG. 14 shows (a) the EDS spectrum and (b) the Zr XPS spectrum of the nano magnesium hydride doped with zirconium prepared in example 4;

[0052] FIG. 15 shows the temperature-dependent desorption mass spectrometry curves of Zr-doped nano magnesium hydride prepared in example 4 and the TiCl.sub.4 doped nano magnesium hydride prepared in controls 9 and 10;

[0053] FIG. 16 shows the temperature-dependent desorption mass spectrometry curves of Nb-doped nano magnesium hydride prepared in example 5 and the NbCl.sub.5 doped nano magnesium hydride prepared in controls 11 and 12;

[0054] FIG. 17 shows (a) the SEM image, (b) the TEM image and (c,d) the high-resolution TEM image of the Ni-catalyzed nano magnesium hydride prepared in example 6;

[0055] FIG. 18 shows the temperature-dependent desorption mass spectrometry curves of the Ni-catalyzed nano-magnesium hydride prepared in example 6 and the NiCl.sub.2-doped magnesium hydride prepared by the traditional method.

DESCRIPTION OF THE EMBODIMENTS

[0056] The following is a further description of the invention in combination with specific examples. The following are only specific examples of the invention, but the scope of protection of the invention is not limited to this.

Example 1 Preparation of Nano Magnesium Hydride

[0057] (1) Put 500 mg of anhydrous magnesium chloride and 500 mg of lithium hydride into a ball mill jar in an argon atmosphere glove box, and crush them for 3 hours at a speed of 350 r.p.m.;

[0058] (2) In an argon atmosphere glove box, take a total of 600 mg of ball-milled anhydrous magnesium chloride and lithium hydride (molar ratio 1:2) and put them into a 250 ml flask. Then, pour 150 ml of ultra-dry tetrahydrofuran into the flask and stir for 30 min, wait until the magnesium chloride is fully dissolved;

[0059] (3) Insert the ultrasonic horn into the flask, keep the end of the ultrasonic horn in the middle of the mixture in the flask, and perform ultrasonic treatment with 210 W output power. During the ultrasonic process, in order to keep the sample temperature from rising, the ultrasonic must be paused after half an hour. After 6 hours of treatment, an ultrasonic product can be obtained;

[0060] (4) Using centrifugation (8000 r.p.m.), separate the solid powder in the product after ultrasound in step (3), put it into a 100 ml flask, and inject 50 ml of ultra-dry tetrahydrofuran, stir for 2 hours for cleaning, so that the by-product lithium chloride can be fully dissolved in tetrahydrofuran;

[0061] (5) The solid powder obtained in step (4) is separated by centrifugation (8000 r.p.m.), washed with tetrahydrofuran and centrifuged to obtain the solid powder, and heated for 2 hours in a dynamic vacuum (vacuum degree of 1×10.sup.−3 Torr). After removing the residual tetrahydrofuran, the nano-magnesium hydride can be obtained, and then the sample is stored in the glove box for later use.

[0062] The sample prepared in the above process is the nano-magnesium hydride. As can be seen from FIG. 1a, the sample only contains magnesium, and the weak oxygen signal and carbon signal are derived from carbon and oxygen pollution in the air or trace organic solvent residue, indicating that the sample is composed of magnesium. It can be seen from FIG. 1b that the 2p spin orbit peak of magnesium in the obtained sample is located at 50.2 eV, indicating that all the magnesium in the sample exists in the form of magnesium hydride.

[0063] It can be seen from FIG. 2 that the sample is composed of a large number of nano magnesium hydride, and the particles are spherical morphology.

[0064] It can be seen from FIG. 3 that the size of nano magnesium hydride is basically maintained at 5 nm. From the high-resolution TEM image, it can be calibrated that the interplanar spacing of magnesium hydride particles of 0.225 nm corresponds to the (200) crystal plane.

[0065] It can be seen from the above analysis that the nano magnesium hydride can be successfully prepared by this method. The sample was heated from room temperature to 400° C. at 2° C./min, and the desorption behavior of the sample during the heating process was analyzed by the mass spectrometer. It can be seen from FIG. 4 that the nano magnesium hydride only releases hydrogen during the heating process, and almost no tetrahydrofuran is released, indicating that the organic solvent has been completely removed in the dynamic vacuum. It can be seen from the dehydrogenation curve that the initial dehydrogenation temperature of the sample is below 100° C., and the peak value of the first dehydrogenation temperature is 190° C., which is lower than the dehydrogenation temperature of magnesium hydride samples prepared by conventional methods.

[0066] Control 1 Preparation of magnesium hydride without reaction promotion

[0067] (1) Put 500 mg of anhydrous magnesium chloride and 500 mg of lithium hydride into a ball milling jar in an argon atmosphere glove box, and mill them for 3 hours at the speed of 350 r.p.m.;

[0068] (2) In an argon atmosphere glove box, take the ball-milled anhydrous magnesium chloride and lithium hydride totaling 600 mg (molar ratio 1:2), put them into a 250 ml flask, then inject 150 ml of ultra-dry tetrahydrofuran into the flask and stir for 12 h;

[0069] (3) The solid state powder in the ultrasonic product in step (3) is separated by centrifugation (8000 r.p.m.).

[0070] After the above experiments, it was found that the solid material could not be collected by centrifugation. It can be seen that the reaction between MgCl.sub.2 and LiH has a higher energy barrier. In the absence of additional energy input (ultrasonic wave), the reaction kinetics between MgCl.sub.2 and LiH is too slow at room temperature and pressure. Therefore, in the invention, ultrasound not only plays a role in controlling the agglomeration and growth of particles, but also plays a role in accelerating the chemical reaction between MgCl.sub.2 and LiH.

[0071] Control 2

[0072] In a glove box filled with argon, a total of 1.2 g of anhydrous magnesium chloride and lithium hydride (molar ratio 1:2) are put into a ball milling jar, and the ball milling is performed on a high-energy ball mill. The ball milling atmosphere is argon atmosphere and the speed is 500 r.p.m., the ball-to-powder weight ratio is 120:1, and the milling time is 24 hours. Put the ball-milled sample in tetrahydrofuran for washing twice to remove the by-product lithium chloride, and then obtain solid powder by centrifugation, and remove the residual tetrahydrofuran under dynamic vacuum conditions (vacuum degree of 1×10.sup.−3 Torr). The magnesium hydride prepared by the ball milling method can be obtained, and then the sample is heated to 400° C. at a heating rate of 2° C./min, and the hydrogen release behavior of the sample during the heating process is recorded by a mass spectrometer. The above operations are carried out under inert atmosphere.

[0073] It can be seen from FIG. 5 that the initial temperature of the nano magnesium hydride prepared by the ultrasonic-assisted method is lower than that of the magnesium hydride prepared by the ball milling method by 180° C., the peak temperature of the hydrogen release in the first step is reduced by 130° C., and the hydrogen release performance is significantly improved.

[0074] It can be seen from FIG. 6a that the diffraction peak intensity of the prepared magnesium hydride due to the fine particles of MgH.sub.2 is lower and the peak width is larger. During the hydrogen release process, the diffraction peak of Mg gradually appears and strengthens with the increase of temperature. After the dehydrogenated product absorbs hydrogen, the Mg peak disappears. Compared with the hydrogen desorption process of MgH.sub.2 prepared by the traditional method in Control 2, the metal magnesium obtained by the decomposition of the nano magnesium hydride prepared by ultrasound has smaller particles, a larger proportion of surface atoms, worse lattice order, and wider diffraction peak, compared with the product of dehydrogenation prepared by the traditional method, the crystallinity of which is better and the peak shape is sharper.

[0075] Control 3

[0076] In a glove box filled with argon, 1 g of magnesium powder was put into a stainless steel tubular reactor, filled with high-purity hydrogen at 20 atm, and then the reactors are heated to 550 and 350° C., respectively. Keep the temperature for 4 hours each to ensure that the magnesium powder in the reactors is fully hydrogenated to convert to magnesium hydride. Subsequently, the magnesium hydride in the reactor is transferred to the ball milling jar and filled with 50 atmospheres of high-purity hydrogen. Ball milling is conducted at a speed of 500 r.p.m. and a ball-to-powder weight ratio of 120:1. The magnesium hydride is obtained after ball milling for 24 hours. Then, the sample is heated to 400° C. at a heating rate of 2° C./min, and the hydrogen release behavior during the heating process is recorded by a mass spectrometer.

[0077] It can be seen from FIG. 5 that the initial temperature of the nano-magnesium hydride prepared by the ultrasonic-assisted method is lower by 125° C. than the magnesium hydride prepared by the heating-ball milling method, and the peak temperature of the hydrogen release in the first step is reduced by 90° C., and the hydrogen release performance is significantly improved. It can be seen from FIG. 6b that the crystal lattice structure of the Mg generated during the hydrogen desorption process of MgH.sub.2 in this example is obviously different from of that obtained by the decomposition of the nano magnesium hydride prepared by ultrasound.

Example 2 Preparation of Ti-Catalyzed Nano Magnesium Hydride

[0078] (1) Put anhydrous magnesium chloride (500 mg) and lithium hydride (500 mg) into a ball milling tank in an argon atmosphere glove box, and crush them for 3 hours at a speed of 350 rpm/min.

[0079] (2) In an argon atmosphere glove box, take the ball-milled anhydrous magnesium chloride and lithium hydride (molar ratio 1:2) totaling 600 mg and titanium tetrachloride (16.4 μL), put them into a 250 ml flask, and then pour into the flask 100 ml of ultra-dry cyclohexane. They are stirred for 30 minutes. The molar ratio of Ti catalyst to magnesium chloride in this example is 0.03:1.

[0080] (3) Insert the ultrasonic horn into the flask, keep the end of the ultrasonic rod in the middle of the mixture in the flask, and perform ultrasonic treatment with 210 W output power. During the ultrasonic process, in order to keep the sample temperature from rising, the continuous ultrasonic must be paused after half an hour. After 6 hours of treatment, an ultrasonic product is obtained.

[0081] (4) Use centrifugation (8000 r.p.m.) to separate the solid powder in the ultrasonic product in step (3), and then put it into a 100 ml flask and inject 50 ml of ultra-dry tetrahydrofuran, and magnetically stir for 2 hours for cleaning to make sure that the lithium chloride as by-products is fully dissolved in tetrahydrofuran.

[0082] (5) The solid powder obtained in step (4) is separated by centrifugation (8000 r.p.m.), washed again with tetrahydrofuran and centrifuged to obtain the solid powder, and kept in a dynamic vacuum (vacuum degree of 1×10.sup.−3 Torr) for 2 hours to remove the residual tetrahydrofuran. The Ti-catalyzed doped nano magnesium hydride named nano-MgH.sub.2-0.03Ti can be obtained, and then the sample is stored in a glove box for later use.

[0083] It can be seen from FIG. 7a that the sample contains only magnesium and titanium elements. The weak oxygen and carbon signals come from carbon and oxygen pollution in the air or trace organic solvent residues, indicating that the main phase of the sample is magnesium hydride and a small amount of titanium as a catalyst. It can be seen from FIG. 7b that the Ti 2p.sub.3/2-2p.sub.1/2 dual spin-orbit peaks of the titanium element in the obtained sample are located at 453.9 and 459.3 eV, respectively, indicating that TiCl.sub.4 has been completely reduced to Ti element by this method. It can be seen that ultrasound can not only trigger the synthesis reaction of MgH.sub.2, but also trigger the reduction reaction of TiCl.sub.4 by LiH.

[0084] It can be seen from FIG. 8 that the nano magnesium hydride are basically maintained at 5 nm. From the high-resolution transmission photos, it can be calibrated that the interplanar spacing of the magnesium hydride particles 0.225 nm corresponds to the (200) crystal plane.

[0085] It can be seen from the above analysis that the method can successfully prepare Ti-catalyzed doped nano magnesium hydride samples. The sample is heated from room temperature to 400° C. at 2° C./min, and the degassing curve of the sample during the heating process was analyzed by a mass spectrometer. It can be seen from the FIG. 9 that the initial hydrogen release temperature of the sample is 40° C., the peak temperature of hydrogen release in the first step is 115° C., which is lower than that of magnesium hydride samples prepared by conventional methods.

[0086] In addition, for the Ti-catalyzed-doped nano magnesium hydride samples prepared with the molar ratio of Ti catalyst to magnesium chloride of 0.01:1 and 0.05:1, the desorption behavior of the sample during heating was analyzed by a mass spectrometer. The hydrogen release temperature is 35° C. (0.01:1) and 50° C. (0.05:1). The peak temperature of hydrogen release in the first step is 90° C. (0.01:1) and 125° C. (0.05:1) (FIG. 9).

[0087] Control 4

[0088] In a glove box filled with argon, put anhydrous magnesium chloride and lithium hydride (molar ratio 1:2, total 1.2 g) and titanium tetrachloride (32.5 μL) into a ball milling tank, and perform ball milling on a high-energy ball mill. The atmosphere is argon, the speed is 500 r.p.m., the ball-to-powder weight ratio is 120:1, and the ball milling time is 24 hours. The sample after ball milling is placed in tetrahydrofuran under an inert atmosphere and washed twice to remove lithium chloride as the by-product. Then, the solid powder is obtained by centrifugation, and the residual tetrahydrofuran is removed under dynamic vacuum conditions (vacuum degree is 1×10.sup.−3 Torr) to obtain titanium-catalyzed magnesium hydride. In the sample, the molar ratio of titanium catalyst to magnesium chloride is 0.03:1, and then the sample is heated to 400° C. at a heating rate of 2° C./min, and the mass spectrometer is used to record the sample's heating process hydrogen release behavior.

[0089] It can be seen from FIG. 9 that the Ti-catalyzed-doped nano magnesium hydride prepared by the ultrasonic-assisted method has a lower initial temperature of 140° C. than that prepared by the ball milling method, and the peak temperature of the hydrogen release in the first step is reduced by 143° C. The hydrogen desorption performance is significantly better than that prepared by ball milling.

[0090] Control 5

[0091] In a glove box filled with argon, 1 g of magnesium powder was put into a stainless steel tubular reactor, and the reactor was filled with 20 atm of high-purity hydrogen, and then the reactor was heated to 550 and 350° C. for 4 hours each to hydrogenate the magnesium powder in the reactor to form magnesium hydride. Subsequently, the magnesium hydride in the reactor was transferred to a ball milling jar, and after adding 32.5 μL of titanium tetrachloride, it was filled with 50 atmospheres of high-purity hydrogen, the speed is 500 rpm/min, and the ball-to-powder weight ratio is 120:1. After 4 hours of ball milling, the titanium-catalyzed magnesium hydride was obtained.

[0092] It can be seen from FIG. 9 that the Ti-catalyzed doped nano-magnesium hydride prepared by the ultrasonic-assisted method has a lower initial temperature of 120° C. than the Ti-catalyzed magnesium hydride prepared by the heating-ball milling method. The temperature is reduced by 110° C. and the hydrogen release performance is significantly improved.

[0093] Control 6

[0094] Using the same method described in Example 3, ultrasonic treatment was employed to prepare the Ti-catalyzed doped nano magnesium hydride, and the amount of TiCl.sub.4 in it was increased. The molar ratio of Ti catalyst to magnesium chloride is 0.1:1.

[0095] It can be found from FIG. 10 that the performance is significantly worse after increasing the amount of TiCl.sub.4. The main hydrogen release peak shifts to the high temperature region, and there is only weak hydrogen release in the low temperature region. This indicates that the addition of excessive catalyst will have an adverse effect on the ultrasonic promotion of the reaction of MgCl.sub.2 and LiH [MgCl.sub.2+2LiH.fwdarw.MgH.sub.2+2LiCl], resulting in the decrease of the energy barrier of the reaction, the promotion of product crystallization of the excess energy, and the increase of the particle size of MgH.sub.2.

[0096] It can be seen from FIG. 11 that after adding an excessive amount of catalyst, the Mg product of the sample hydrogenation showed a peak similar to that of the sample hydrogenation product of control 2 (traditional method).

Example 3 Preparation of Nano Magnesium Hydride Doped with V Catalyst

[0097] The preparation method is the same as in example 2, but the difference is that the transition metal catalyst used is vanadium trichloride. Table 1 lists the corresponding raw material ratio and key processes. The sample is named nano-MgH.sub.2-0.03V.

TABLE-US-00001 TABLE 1 Nano-MgH.sub.2-0.03 V sample preparation process and raw material ratio Ultrasonic power (W) Ultrasound time (h) MgCl.sub.2 + LiH (mg) VCl.sub.3 (mg) 210 6 600 24

[0098] It can be seen from FIG. 12a that the sample contains only magnesium and vanadium. The weak oxygen and carbon signals come from carbon and oxygen pollution in the air or residual trace organic solvents, indicating that the main phase of the sample is magnesium hydride and a small amount of vanadium as the catalyst. It can be seen from FIG. 12b that the V2p.sub.3/2-Vp.sub.1/2 spin-orbit peaks in the obtained sample are located at 512.5 and 519.7 eV, respectively, indicating that VCl.sub.3 has been completely reduced to V element by this method.

[0099] The dehydrogenation curve (2° C./min) of the sample was analyzed by a mass spectrometer (FIG. 13). The hydrogen desorption performance parameters of the sample in this example are summarized in Table 4. The dehydrogenation temperature of the sample was lower than that of the conventional method.

[0100] Control 7

[0101] The preparation method is the same as in control 4, but the difference is that the transition metal catalyst used is vanadium trichloride. Table 2 lists the corresponding raw material ratio and key processes.

TABLE-US-00002 TABLE 2 Preparation process of the sample in control 7 and raw material ratio Rotational ball-to-powder Ball milling MgCl.sub.2 + LiH VCl.sub.3 speed (r.p.m.) weight ratio time (h) (mg) (mg) 500 120:1 24 1200 47

[0102] In the samples, the molar ratio of V catalyst to MgH.sub.2 is 0.03:1. FIG. 13 shows the comparison of the hydrogen release curve of the sample of Example 3 and the sample of this control example. The relevant hydrogen release parameters are summarized in Table 4.

[0103] Control 8

[0104] The preparation method is the same as in control 5, but the difference is that the transition metal catalyst used is vanadium trichloride. Table 3 lists the corresponding raw material ratio and key processes.

TABLE-US-00003 TABLE 3 Preparation process of the sample in control 8 and raw material ratio Rotational ball-to-powder Ball milling Magnesium VCl.sub.3 speed (r.p.m.) weight ratio time (h) powder (mg) (mg) 500 120:1 24 1000 200

[0105] In the samples, the molar ratio of V catalyst to MgH.sub.2 is 0.03:1. FIG. 13 shows the comparison of the hydrogen release curve of the sample of Example 3 and the sample of this control. The relevant hydrogen release performance parameters are summarized in Table 4.

TABLE-US-00004 TABLE 4 Performance comparison of V catalyzed MgH.sub.2 samples Initial dehydrogenation Peak temperature Sample name temperature (° C.) (° C.) nano-MgH.sub.2-0.03 V  70 163 Control 7 245 293 Control 8 220 263

[0106] It can be seen from the performance comparison of the samples summarized in Table 4 that the samples prepared by the ultrasound-assisted method have better hydrogen desorption kinetics than those prepared by the traditional method.

Example 4 Preparation of Nano Magnesium Hydride Doped with Zr Catalyst

[0107] The preparation method is the same as in example 2, but the difference is that the transition metal catalyst used is zirconium tetrachloride. Table 4 lists the corresponding raw material ratio and key processes. The sample is named nano-MgH.sub.2-0.03Zr.

TABLE-US-00005 TABLE 5 Nano-MgH.sub.2-0.03 Zr preparation process and raw material ratio Ultrasonic power Ultrasound time MgCl.sub.2 + LiH ZrCl.sub.4 (W) (h) (mg) (mg) 210 10 600 35

[0108] FIG. 14a shows the energy dispersive spectrometer data (EDS) of the sample. It can be seen from the FIG. 14a that the sample contains only magnesium and zirconium. The weak oxygen and carbon signals come from carbon and oxygen pollution in the air or residual trace organic solvent, indicating that the main phase of the sample is magnesium hydride, and a small amount of zirconium is used as a catalyst. FIG. 14 shows the X-ray photoelectron spectroscopy (XPS) of titanium in the sample. It can be seen that the Zr3d.sub.5/2-3d.sub.3/2 spin orbit peaks in the sample are located at: 177.6 and 181.1 eV, indicating that using this method, ZrCl.sub.4 has been completely reduced to zirconium.

[0109] From the above analysis, it can be seen that the Zr-catalyzed nano-magnesium hydride sample can be successfully prepared by this method. The dehydrogenation curve (2° C./min) of the sample was analyzed by a mass spectrometer (FIG. 15). The hydrogen desorption parameters of the sample are summarized in Table 8. The sample has a lower hydrogen desorption temperature than the magnesium hydride sample prepared by the conventional method.

[0110] Control 9

[0111] The preparation method is the same as in control 4, but the difference is that the transition metal catalyst used is zirconium tetrachloride. Table 6 lists the corresponding raw material ratio and key processes.

TABLE-US-00006 TABLE 6 Preparation process of the sample in control 9 and raw material ratio Rotational ball-to-powder Ball milling MgCl.sub.2 + LiH ZrCl.sub.4 speed (r.p.m.) weight ratio time (h) (mg) (mg) 500 120:1 24 1200 70

[0112] FIG. 15 shows the comparison diagram of the hydrogen release curve of the sample of example 4 and the sample of this control example. The performance parameters of the sample of this control example are summarized in Table 8.

[0113] Control 10

[0114] The preparation method is the same as in control 5, but the difference is that the transition metal catalyst used is zirconium tetrachloride. Table 7 lists the corresponding raw material ratio and key processes.

TABLE-US-00007 TABLE 7 Preparation process of the sample in control 10 and raw material ratio Rotational ball-to-powder Ball milling Magnesium ZrCl.sub.4 speed (r.p.m.) weight ratio time (h) powder (mg) (mg) 500 120:1 24 1000 270

[0115] In the samples, the molar ratio of Zr catalyst to MgH.sub.2 is 0.03:1. FIG. 15 shows the hydrogen release curves of the sample of Example 4 and the sample of this control. The relevant hydrogen release parameters are summarized in Table 8.

TABLE-US-00008 TABLE 8 Performance comparison of V catalyzed MgH.sub.2 samples Initial dehydrogenation Peak temperature Sample name temperature (° C.) (° C.) nano-MgH.sub.2-0.03 V  70 163 Control 9  245 293 Control 10 220 263

[0116] It can be seen from Table 8 that the samples prepared by the ultrasound-assisted method have better hydrogen desorption kinetics than those prepared by the traditional method.

Example 5 Preparation of Nano Magnesium Hydride Doped by Nb Catalysis

[0117] The preparation method is the same as in example 2, but the difference is that the transition metal catalyst used is niobium pentachloride. Table 9 lists the corresponding raw material ratio and key processes. The sample is named nano-MgH.sub.2-0.03Zr.

TABLE-US-00009 TABLE 9 Nano-MgH.sub.2-0.03 Nb preparation process and raw material ratio Ultrasonic power Ultrasound time MgCl2 + LiH NbCl.sub.5 (W) (h) (mg) (mg) 210 10 600 40

[0118] FIG. 16 shows the dehydrogenation curve (2° C./min) of the sample during heating. The hydrogen desorption parameters of the sample are summarized in Table 11. Compared with the magnesium hydride sample prepared by the conventional method, the hydrogen desorption temperature is better.

[0119] Control 11

[0120] The preparation method is the same as in control 4, but the difference is that the transition metal catalyst used is niobium pentachloride. Table 10 lists the corresponding raw material ratio and key processes.

TABLE-US-00010 TABLE 10 Preparation process of the sample in control 11 and raw material ratio Rotational ball-to-powder Ball milling MgCl.sub.2 + LiH NbCl.sub.5 speed (r.p.m.) weight ratio time (h) (mg) (mg) 500 120:1 24 1200 80

[0121] In the samples, the molar ratio of Nb catalyst to MgH.sub.2 is 0.03:1. FIG. 16 shows the comparison of the hydrogen release curve of the sample of Example 5 and the sample of this control. The relevant hydrogen release performance parameters are summarized in Table 11.

[0122] Control 12

[0123] The preparation method is the same as in control 5, but the difference is that the transition metal catalyst used is niobium pentachloride. Table 11 lists the corresponding raw material ratio and key processes.

TABLE-US-00011 TABLE 11 Preparation process of the sample in control 12 and raw material ratio Rotational ball-to-powder Ball milling Magnesium NbCl.sub.5 speed (r.p.m.) weight ratio time (h) powder (mg) (mg) 500 120:1 24 1000 310

[0124] In the samples, the molar ratio of Nb catalyst to MgH.sub.2 is 0.03:1. FIG. 16 shows the comparison of the hydrogen release curve of the sample of Example 5 and the sample of this control. The relevant hydrogen release parameters are summarized in Table 12.

TABLE-US-00012 TABLE 12 Performance comparison of Nb catalyzed MgH.sub.2 samples Initial dehydrogenation Peak temperature Sample name temperature (° C.) (° C.) nano-MgH.sub.2-0.03 Nb  65 137 Control 11 205 267 Control 12 210 247

[0125] It can be seen from Table 12 that the samples prepared by the ultrasound-assisted method have better hydrogen evolution kinetics than those prepared by the traditional method.

Example 6 Preparation of Ni-Catalyzed Nano Magnesium Hydride Sample

[0126] The preparation method is the same as in example 2, but the difference is that the transition metal catalyst used is nickel dichloride. Table 13 lists the corresponding raw material ratio and key processes. The sample is named nano-MgH.sub.2-0.03Ni.

TABLE-US-00013 TABLE 13 Nano-MgH2-0.03 Ni preparation process and raw material ratio Ultrasonic Ultrasound MgCl.sub.2 + LiH NiCl.sub.2 power (W) time (h) (mg) (mg) 210 10 600 20

[0127] FIG. 17 shows the SEM and TEM pictures of the nano-MgH.sub.2-0.03Ni sample. It can be seen that the sample presents a layered structure similar to graphene. From the TEM picture, it can be seen that each layer of the sample contains a large number of magnesium hydride nanoparticles, the particle size is maintained at about 3 nanometers. It can be seen that by changing the composition of the additives, the morphology of the product can be adjusted to a certain extent.

[0128] FIG. 18 shows the dehydrogenation curve (2° C./min) of the sample during heating. The hydrogen desorption parameters of the sample are summarized in Table 16. Compared with the magnesium hydride sample prepared by the conventional method, the hydrogen desorption temperature is lower.

[0129] Control 13

[0130] The preparation method is the same as in control 4, but the difference is that the transition metal catalyst used is nickel dichloride. Table 14 lists the corresponding raw material ratio and key processes.

TABLE-US-00014 TABLE 14 Preparation process of the sample in control 13 and raw material ratio Rotational ball-to-powder Ball milling MgCl.sub.2 + LiH NiCl.sub.2 speed (r.p.m.) weight ratio time (h) (mg) (mg) 500 120:1 24 1200 80

[0131] In the samples, the molar ratio of Ni catalyst to MgH.sub.2 is 0.03:1. FIG. 18 shows the hydrogen release curves of the sample of Example 6 and the sample of this control. The relevant hydrogen release parameters are summarized in Table 16.

[0132] Control 14

[0133] The preparation method is the same as in control 5, but the difference is that the transition metal catalyst used is nickel dichloride. Table 15 lists the corresponding raw material ratio and key processes.

TABLE-US-00015 TABLE 15 Preparation process of the sample in control 14 and raw material ratio Rotational ball-to-powder Ball milling Magnesium NiCl.sub.2 speed (r.p.m.) weight ratio time (h) powder (mg) (mg) 500 120:1 24 1000 150

[0134] In the samples, the molar ratio of Ni catalyst to MgH.sub.2 is 0.03:1. FIG. 18 shows the hydrogen release curves of the sample of Example 6 and the sample of this control. The relevant hydrogen release parameters are summarized in Table 16.

TABLE-US-00016 TABLE 16 Performance comparison of Ni catalyzed MgH.sub.2 samples Initial dehydrogenation Peak temperature Sample name temperature (° C.) (° C.) nano-MgH.sub.2-0.03 Ni  55 175 Control 13 210 245 Control 14 210 254

[0135] It can be seen from Table 12 that the samples prepared by the ultrasound-assisted method have better hydrogen evolution kinetics than those prepared by the traditional method.