Solid-state hydrogen storage composite material and preparation method thereof

Abstract

The application provides a solid-state hydrogen storage composite material and a preparation method thereof, and the solid-state hydrogen storage composite material is MgH2-MnTiO3, which comprises 3wt%-10wt% of MnTiO3 catalyst and 90wt%-97wt% of MgH2. The solid-state hydrogen storage composite material has excellent performance and uniform phase distribution, has the characteristics of rapid hydrogen absorption and release, and has a dehydrogenation activity of 70.5-85.4kJ / mol, which is lower than that of pure MgH2, and excellent cycle stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of magnesium-based solid-state hydrogen storage materials, in particular to a solid-state hydrogen storage composite material and a preparation method thereof. BACKGROUND

[0002] In the prior art, there is no method of adding a material containing Ti elements and Mn elements or a double metal oxide with the two elements into a magnesium-based solid-state hydrogen storage material for catalysis. Meanwhile, the micron-sized hierarchical porous TiNb2O7spheres synthesized in the prior art can reduce the dehydrogenation starting temperature of MgH2 from 300 DEG C to 177 DEG C and the dehydrogenation activation energy to 94 kJ / mol by adding 7 wt.% of TiNb2O7 catalyst. It has also been found that Co2NiO catalyst reacts with Mg during the dehydrogenation process to generate Mg-Co alloy and CoO4 new phase in situ and play a catalytic role in subsequent reactions, and the dehydrogenation activation energy of MgH2 can be reduced to 118 kJ / mol by adding 10 wt.% of Co2NiO catalyst. 1.29 Ni 1.71 O4 new phase, and in subsequent reactions, and the dehydrogenation activation energy of MgH2 can be reduced to 118 kJ / mol by adding 10 wt.% of Co2NiO catalyst. This in-situ formation of new phase also occurs in MgH2-10 wt.% MnMoO4 composite material, and it has been found that the composite material can achieve 6 wt.% dehydrogenation performance within 10 min at 300 DEG C, and the in-situ generated Mn and MgMo2O7 help the dissociation and diffusion of H2, and the dehydrogenation activation energy is reduced to 109.9 kJ / mol.

[0003] The double metal oxide improves the performance of the magnesium-based hydrogen storage material to a certain extent, but the improvement effect is not ideal, especially the improvement degree of the dehydrogenation activation energy is not large, and the dehydrogenation activation energy is about 100 kJ / mol.

[0004] Therefore, a scheme for further improving the dehydrogenation performance of the magnesium-based hydrogen storage material needs to be proposed.

[0005] In view of this, the present application is proposed. SUMMARY

[0006] The purpose of the present application is to provide a solid-state hydrogen storage composite material and a preparation method thereof. The solid-state hydrogen storage composite material has excellent performance and uniform phase distribution, has the characteristics of rapid hydrogen absorption and release, and the dehydrogenation activation energy is reduced to 70.5-85.4 kJ / mol compared with pure MgH2, and has excellent cycle stability.

[0007] In order to achieve the above purpose, the present application provides the following technical scheme:

[0008] The present application provides a solid-state hydrogen storage composite material, which is MgH2-MnTiO3 and comprises 3 wt.%-10 wt.% of MnTiO3 catalyst and 90 wt.%-97 wt.% of MgH2.

[0009] Further, the solid-state hydrogen storage composite material is MgH2-8wt% MnTiO3, which comprises 8wt% MnTiO3 catalyst and 92wt% MgH2.

[0010] Further, the MnTiO3 catalyst is in the shape of nanodisk.

[0011] Further, the nanodisk has a diameter of 200-400nm and a thickness of <100nm.

[0012] Preferably, the nanodisk has a diameter of 200-350nm.

[0013] Preferably, the nanodisk has a thickness of 35nm-85nm.

[0014] More preferably, the nanodisk has a thickness of 45nm.

[0015] Preferably, the MgH2 has a particle size of 100-500nm.

[0016] In addition, the present application further provides a preparation method of the solid-state hydrogen storage composite material, which comprises the following steps:

[0017] S1, preparation of the MnTiO3 catalyst;

[0018] S2, preparation of the MgH2;

[0019] S3, ball-milling mixing of the MnTiO3 catalyst and the MgH2 to obtain the solid-state hydrogen storage composite material;

[0020] Preferably, the MgH2 is prepared by hydrogenation combustion synthesis in the step S2.

[0021] Preferably, the ball-milling is carried out under the protection of inert atmosphere; more preferably, the inert atmosphere is argon.

[0022] Preferably, the ball-milling mixing is carried out for 8-10h, the ball-to-material ratio is 25-35:1, and the rotation speed is 300-500r / min.

[0023] More preferably, the ball-to-material ratio is 30:1, the rotation speed is 400r / min, the ball-milling is carried out for 10h in the forward and reverse alternating operation mode, and the ball-milling is stopped for 6min every 30min.

[0024] Preferably, the ball-milling mixing is carried out by using a planetary high-energy ball mill.

[0025] Further, the preparation of the MnTiO3 catalyst comprises the following steps:

[0026] S1-1, an appropriate amount of titanium source is measured and added to the stirring solvent, so that the titanium source and the solvent are uniformly mixed to obtain solution A;

[0027] S1-2, the manganese source is weighed and added to the solvent for stirring, so that the manganese source is fully dissolved to obtain solution B;

[0028] S1-3, solution A and solution B are mixed, and deionized water is added and stirred to obtain a mixed solution;

[0029] S1-4, the mixed solution obtained in step S1-3 is subjected to hydrothermal treatment, centrifugation, washing and vacuum drying to obtain MnTiO3 nanodiscs.

[0030] Further, the titanium source in step S1-1 includes tetrabutyl titanate;

[0031] And / or, the solvent in step S1-1 includes ethylene glycol;

[0032] Preferably, the stirring mode in step S1-1 is magnetic stirring, and more preferably, the magnetic stirring time after adding the titanium source is 10-20 min.

[0033] Further, the manganese source in step S1-2 is manganese salt, preferably MnCl2;

[0034] And / or, the solvent in step S1-2 includes ethylenediamine;

[0035] Preferably, the stirring mode in step S1-2 is magnetic stirring, and more preferably, the magnetic stirring time is 30-40 min.

[0036] Further, in the mixed solution, the molar ratio of Mn and Ti in the titanium source and the manganese source is 1:1.

[0037] Further, the reaction temperature during the hydrothermal treatment is 180-200℃;

[0038] Preferably, the reaction time during the hydrothermal treatment is 24-36 h;

[0039] Preferably, the hydrothermal treatment in step 1-4 specifically includes pouring the mixed solution obtained in step S1-3 into a Teflon-lined container, loading it into a reaction kettle, and placing it into a constant temperature oven for hydrothermal reaction. The yellow precipitate C after hydrothermal reaction is subjected to centrifugal treatment, and is repeatedly washed with deionized water and anhydrous ethanol several times to obtain a deep yellow centrifugate, which is vacuum dried to obtain MnTiO3 nanodiscs;

[0040] Preferably, the centrifugal rate of the centrifugal treatment is 6000-8000 rpm;

[0041] Preferably, the temperature of the vacuum drying is 60-80℃;

[0042] Preferably, the vacuum drying time is 8-12h.

[0043] Compared with the prior art, the technical scheme of the present application has at least the following technical effects:

[0044] The present application successfully prepares MnTiO3 nanodiscs by introducing different contents of MnTiO3 catalyst components into MgH2 in a ball milling manner. Due to the synergistic effect of Mn and Ti, MnTiO3 nanodiscs have more excellent catalytic effect than single metal oxides. The Mg-based composite material can well maintain the cycle stability, and has excellent performance and uniform phase distribution. The Mg-based composite material has the characteristics of rapid hydrogen absorption and desorption, and the dehydrogenation activation energy is significantly reduced compared with pure MgH2, such as to 70.5-85.4kJ / mol, and has excellent cycle stability. At the same time, the preparation process of the catalyst is simple.

[0045] In addition, the MnTiO3 catalyst of the present application has the most excellent catalytic effect when the content is 8wt%. By using 8wt% MnTiO3 catalyst, new phases such as magnesium-manganese oxide Mg6MnO8 and titanium dioxide TiO2 are generated in situ during the reaction process, which greatly improves the dehydrogenation activation energy of magnesium hydride (reduced to 72.06kJ / mol) and accelerates the hydrogen absorption and desorption capacity of magnesium hydride. BRIEF DESCRIPTION OF DRAWINGS

[0046] The drawings accompanying the specification of this application form a part thereof, serve to provide further understanding of the present application, and together with the description of the exemplary embodiments of the present application and the explanation thereof, to explain the present application, and do not constitute an improper limitation on the present application. Among them:

[0047] Figure 1 XRD pattern of the nanodisc MnTiO3 catalyst prepared in Example 1;

[0048] Figure 2 SEM image of the MnTiO3 nanodisc prepared in Example 1;

[0049] Figure 3a TEM image of the MnTiO3 nanodisc prepared in Example 1;

[0050] Figure 3b HRTEM image of the MnTiO3 nanodisc prepared in Example 1;

[0051] Figure 4 Representative SEM image of the ball milling sample of MgH2-8wt% MnTiO3 prepared in Example 1 and Mg, Mn and Ti element mapping images obtained by scanning different element components;

[0052] Figure 5a Representative TEM image of the rehydrogenated sample of MgH2-8 wt% MnTiO3 prepared for Example 1;

[0053] Figure 5b Representative HRTEM image of the rehydrogenated sample of MgH2-8 wt% MnTiO3 prepared for Example 1;

[0054] Figure 5c Representative SAED image of the rehydrogenated sample of MgH2-8 wt% MnTiO3 prepared for Example 1;

[0055] Figure 6a DSC curves (10°C / min) of MgH2doped with different amounts of MnTiO3catalyst;

[0056] Figure 6b Thermal desorption (TPD) curves (5°C / min) of MgH2-8 wt% MnTiO3 prepared for Example 1;

[0057] Figure 6c First decomposition of the thermal desorption (TPD) curves (5°C / min) of MgH2-8 wt% MnTiO3 prepared for Example 1;

[0058] Figure 6d Second decomposition of the thermal desorption (TPD) curves (5°C / min) of MgH2-8 wt% MnTiO3 prepared for Example 1;

[0059] Figure 7a Isothermal hydrogenation curves (3 MPa) of MgH2-8 wt% MnTiO3 prepared for Example 1 at different temperatures;

[0060] Figure 7b Isothermal dehydrogenation curves (0.005 MPa) of MgH2-8 wt% MnTiO3 prepared for Example 1 at different temperatures;

[0061] Figure 8a Isothermal hydrogenation and dehydrogenation cycling kinetics curves of MgH2-8 wt% MnTiO3 prepared for Example 1 at 275°C from the 1stto the 50thcycle;

[0062] Figure 8b Plot of hydrogen uptake / desorption capacity of MgH2-8 wt% MnTiO3 prepared for Example 1 at 275°C from the 1stto the 50thcycle;

[0063] Figure 9aDSC curves of MgH2-8 wt% MnTiO3 prepared for example 1 at different heating rates of 5, 8, 10 and 13 °C / min.

[0064] Figure 9b Kissinger plot of the dehydrogenation activation energy of MgH2-8 wt% MnTiO3 prepared for example 1. DETAILED DESCRIPTION

[0065] In order to make the objects, technical solutions, and advantages of the present application clearer, the following will be combined with embodiments of the present application to make a clear and complete description of the technical solutions in the embodiments of the present application. It should be appreciated by those skilled in the art that the embodiments are only used for understanding the present application and should not be regarded as specific limitations to the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work should fall within the scope of protection of the present application. The process parameters not specified in the following examples are usually carried out under conventional conditions.

[0066] The endpoints of the ranges and any values described in the present disclosure are not limited to the precise values stated. The ranges and values should be construed to be approximations that allow for significant variation. Various

[0067] According to a first aspect of the present application, a solid-state hydrogen storage composite material is provided, the solid-state hydrogen storage composite material is MgH2-MnTiO3, comprising 3 wt%-10 wt% of MnTiO3 catalyst and 90 wt%-97 wt% of MgH2.

[0068] Typically but not limitedly, the solid-state hydrogen storage composite material comprises 3 wt% of MnTiO3 catalyst and 97 wt% of MgH2, 4 wt% of MnTiO3 catalyst and 96 wt% of MgH2, 5 wt% of MnTiO3 catalyst and 95 wt% of MgH2, 6 wt% of MnTiO3 catalyst and 94 wt% of MgH2, 7 wt% of MnTiO3 catalyst and 93 wt% of MgH2, 8 wt% of MnTiO3 catalyst and 92 wt% of MgH2, 9 wt% of MnTiO3 catalyst and 91 wt% of MgH2, 10 wt% of MnTiO3 catalyst and 90 wt% of MgH2, and a numerical range between any two points. When the catalyst content is lower than 3 wt%, the catalytic effect provided is low and the dehydrogenation activation energy and hydrogen storage performance of the solid-state hydrogen storage material cannot be obviously improved; when the catalyst content is higher than 10 wt%, the catalytic effect brought by the catalyst starts to weaken and the content of the solid-state hydrogen storage material decreases, resulting in a decrease in the hydrogen storage performance.

[0069] As a preferred embodiment of the present application, the solid-state hydrogen storage composite material is MgH2-8wt% MnTiO3, comprising 8wt% MnTiO3 catalyst and 92wt% MgH2.

[0070] As a preferred embodiment of the present application, the MnTiO3 catalyst is in the shape of nanodisc.

[0071] As a preferred embodiment of the present application, the diameter of the nanodisc is 200-400nm and the thickness is <100nm; the MnTiO3 catalyst prepared in the present application has unique advantages compared to single-metal catalysts, most notably the coordinated catalysis between multiple metals, which will have different catalytic effects on magnesium during the reaction, and the coordination of the two is more advantageous than single-metal catalysts; on the other hand, the catalytic performance of catalysts with different morphologies is not the same, the MnTiO3 catalyst in the present application is in the shape of nanodisc, with uniform size and good structure design, which is uniformly dispersed in MgH2 by ball milling, promoting the hydrogen storage performance of MgH2; compared to powder catalysts or catalysts with other morphologies, the nanodisc morphology exposes different crystal face characteristics, which also improves the catalytic performance. In addition, the diameter and thickness of the nanodisc catalyst of the present application also have a certain influence on the catalytic performance, and the catalyst morphology is smaller, which will be more uniformly dispersed on the surface of the magnesium-based material after ball milling, thus providing more effective and intuitive catalytic performance.

[0072] Preferably, the diameter of the nanodisc is 200-350nm;

[0073] Preferably, the thickness of the nanodisc is 35nm-85nm;

[0074] More preferably, the thickness of the nanodisc is 45nm;

[0075] Preferably, the particle size of MgH2 is 100-500nm;

[0076] Typically but not limitedly, the diameter of the nanodisc is 200nm, 250nm, 300nm, 350nm and 400nm, and any numerical range between any two of them.

[0077] Typically but not limitedly, the thickness of the nanodisc is 30nm, 35nm, 40nm, 45nm, 50nm, 55nm, 60nm, 65nm, 70nm, 75nm, 80nm, 85nm and 90nm, and any numerical range between any two of them.

[0078] Typically but not limited to, the particle size of MgH2 is 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm and 500 nm, and any numerical range between any two of the above values.

[0079] According to the second aspect of the present application, there is also provided a method for preparing the solid-state hydrogen storage composite material as described above, comprising the following steps:

[0080] S1, preparation of MnTiO3 catalyst;

[0081] S2, preparation of MgH2;

[0082] S3, ball-milling mixing of MnTiO3 catalyst and MgH2 to obtain the solid-state hydrogen storage composite material;

[0083] Preferably, the hydrogenation combustion synthesis method is used to prepare MgH2 in the step S2;

[0084] Preferably, the ball-milling is carried out under the protection of inert atmosphere; more preferably, the inert atmosphere is argon;

[0085] Preferably, the ball-milling mixing is carried out for 8-10h (including 8h, 8.5h, 9h, 9.5h and 10h, and any numerical range between any two of the above values), the ball-to-material ratio is 25-35:1 (including 25:1, 26:1, 27:1, 28:1, 29:1, 30:1, 32:1, 33:1, 34:1 and 35:1, and any numerical range between any two of the above values), and the rotation speed is 300-500r / min (including 300r / min, 310r / min, 350r / min, 400r / min, 450r / min, 490r / min and 500r / min, and any numerical range between any two of the above values);

[0086] More preferably, the ball-to-material ratio is 30:1, the rotation speed is 400r / min, the ball-milling is carried out for 10h in the forward and reverse alternating operation mode, wherein the ball-milling is stopped for 6min every 30min; the ball-milling process generates heat, and overheating can cause the alloy to be cold-welded, so appropriate stopping can dissipate heat, and the forward and reverse alternating operation means that the ball-milling tank driven by the motor is rotated in the forward and reverse directions alternately, i.e. from clockwise to counterclockwise, and then from counterclockwise to clockwise. This rotation mode can make the materials in the ball-milling machine be better mixed and uniform. It can be understood that the ball-milling mixing time, rotation speed and specific ball-milling mode of the present application can make the catalyst be better compounded with the solid-state hydrogen storage material, thereby better improving the dehydrogenation activation energy of magnesium hydride.

[0087] Preferably, the ball-milling mixing uses a planetary high-energy ball mill.

[0088] As a preferred embodiment of the present application, the preparation of the MnTiO3 catalyst specifically comprises the following steps:

[0089] S1-1, an appropriate amount of titanium source is measured and added to the stirring solvent, so that the titanium source and the solvent are uniformly mixed to obtain solution A;

[0090] S1-2, weigh the manganese source and add it to the solvent for stirring, so that the manganese source is fully dissolved to obtain solution B;

[0091] S1-3, mix solution A and solution B, continue to stir after adding deionized water to obtain a mixed solution;

[0092] S1-4, the mixed solution obtained in step S1-3 is subjected to hydrothermal treatment, centrifugation, washing and vacuum drying to obtain MnTiO3 nanodiscs.

[0093] In S1-1, since the titanium source such as tetrabutyl titanate will hydrolyze when it comes into contact with air, the titanium source needs to be added to the stirring solvent, while stirring, so that it can be more uniformly dispersed therein to ensure the phase performance.

[0094] In S1-3, the volume ratio of deionized water to the total amount of solution A and solution B is 1:4-3:8.

[0095] The addition of an appropriate amount of deionized water can promote the hydrolysis of the metal precursor and promote the formation of disc-shaped morphology with uniform size and good size.

[0096] As a preferred embodiment of the present application, the titanium source in step S1-1 includes tetrabutyl titanate;

[0097] And / or, the solvent in step S1-1 includes ethylene glycol;

[0098] Preferably, the tetrabutyl titanate is 5 mmol, and the content of the ethylene glycol solvent is 60-70 mL to form solution A;

[0099] Preferably, the stirring mode in step S1-1 is magnetic stirring, and more preferably, the time of magnetic stirring is 10-20 min.

[0100] Typical but not limited time is 10 min, 12 min, 14 min, 16 min, 18 min and 20 min, and any value range between any two points.

[0101] As a preferred embodiment of the present application, the manganese source in step S1-2 is a manganese salt, preferably MnCl2; more preferably MnCl2·4H2O;

[0102] And / or, the solvent in the step S1-2 comprises ethylenediamine;

[0103] Preferably, the amount of MnCl2·4H2O is 5 mmol, and the content of the ethylenediamine solvent is 15-20 mL, to form solution B;

[0104] Preferably, the stirring mode in the step S1-2 is magnetic stirring, and more preferably, the time for magnetic stirring after adding the titanium source is 30-40 min.

[0105] Typically but not limitedly, the time is 30 min, 32 min, 34 min, 36 min, 38 min, and 40 min, and any numerical range between any two points.

[0106] As a preferred embodiment of the present application, in order to keep the formed nanodisc phase uniform, the molar ratio of Mn and Ti in the titanium source and manganese source in the mixed solution is 1:1.

[0107] As a preferred embodiment of the present application, the temperature of the hydrothermal reaction is 180-200℃ (including 180℃, 185℃, 190℃, 195℃, and 200℃, and any numerical range between any two points).

[0108] Preferably, the time of the hydrothermal reaction is 24-36h (including 24h, 26h, 28h, 30h, 32h, 34h, and 36h, and any numerical range between any two points); under the conditions of the preferred hydrothermal reaction temperature and hydrothermal reaction time set in the present application, the crystallinity of MnTiO3 is higher.

[0109] Preferably, the hydrothermal treatment in the step 1-4 specifically comprises pouring the mixed solution obtained in the step S1-3 into a Teflon-lined container, loading into a reaction kettle, and placing into a constant-temperature oven for hydrothermal reaction; the yellow precipitate C after the hydrothermal reaction is subjected to centrifugal treatment, and repeatedly washed with deionized water and anhydrous ethanol respectively for multiple times to obtain a deep yellow centrifugate, which is vacuum dried to obtain MnTiO3 nanodiscs;

[0110] Preferably, the centrifugal rate of the centrifugal treatment is 6000-8000rpm (including 6000rpm, 6500rpm, 7000rpm, 7500rpm, and 8000rpm, and any numerical range between any two points).

[0111] Preferably, the temperature of the vacuum drying is 60-80℃ (including 60℃, 65℃, 70℃, 75℃, and 80℃, and any numerical range between any two points).

[0112] Preferably, the vacuum drying time is 8-12h (including 8h, 9h, 10h, 11h and 12h and any numerical range between any two of these values).

[0113] The application will be further described in detail below in connection with specific examples and comparative examples.

[0114] Example 1

[0115] The present example provides a method for preparing a solid-state hydrogen storage composite material, comprising the following steps:

[0116] S1: Preparation of MnTiO3 catalyst

[0117] S1-1: 1.7mL of tetrabutyl titanate was weighed with a pipette and added to 64mL of ethylene glycol solvent being magnetically stirred, and the tetrabutyl titanate and ethylene glycol solvent were uniformly mixed by magnetic stirring for 15min to obtain solution A;

[0118] S1-2: 0.991g of MnCl2·4H2O solid was weighed and added to 16mL of ethylenediamine for magnetic stirring for 30min, so that the MnCl2·4H2O was fully dissolved to obtain solution B;

[0119] S1-3: The above solution B was slowly poured into solution A and magnetically stirred for 30min; 30mL of deionized water was added to the mixed solution and continued to be stirred;

[0120] S1-4: The mixed solution in step S3 was poured into a Teflon-lined container and loaded into a reaction kettle, which was placed in a constant temperature oven for hydrothermal treatment at 180℃ for 36h. The yellow precipitate C after hydrothermal reaction was centrifuged at 8000rmp for 6min, and washed repeatedly with deionized water and anhydrous ethanol for three times each to obtain a deep yellow centrifugate. After vacuum drying at 60℃ for 10h, MnTiO3 nanodiscs were obtained;

[0121] S2: Preparation of MgH2

[0122] MgH2was synthesized by hydrogenation combustion synthesis (HCS). First, Mg powder was heated from room temperature to 580℃ and kept for 2h, with a heating rate of 10℃ / min. Then the heating system was turned off and naturally cooled to 340℃ and kept for 8h. The pressure was adjusted during the reaction to maintain a hydrogen pressure of 2.0MPa at all times. Finally, the heating and hydrogen input were stopped, and the system was naturally cooled to room temperature to obtain MgH2;

[0123] S3: Preparation of MgH2-8wt% MnTiO3

[0124] MnTiO3 was added to MgH2 according to the mass percentage formula, and the MgH2-8wt%MnTiO3 composite material was obtained by ball milling. The ball-to-material ratio was 30:1, the rotation speed was 400 rpm, the ball milling time was 10 h, and the milling was stopped for 6 min every 30 min. The ball milling was carried out under an argon atmosphere.

[0125] Example 2

[0126] Except for the mass percentage of MnTiO3 added in step S3, which differs from that in Example 1, everything else is the same as in Example 1. In this example, a composite material MgH2-3wt%MnTiO3 with a mass percentage of 3% MnTiO3 was prepared. The dehydrogenation activation energy of MgH2-3wt%MnTiO3 is 85.4 kJ / mol.

[0127] Example 3

[0128] Except for the mass percentage of MnTiO3 added in step S3, which is different from that in Example 1, everything else is the same as in Example 1. In this example, a composite material MgH2-5wt%MnTiO3 with a mass percentage of 5% MnTiO3 is prepared.

[0129] Example 4

[0130] Except for the mass percentage of MnTiO3 added in step S3, which differs from that in Example 1, everything else is the same as in Example 1. In this example, a composite material MgH2-10wt%MnTiO3 with a mass percentage of 10% MnTiO3 is prepared. The dehydrogenation activation energy of MgH2-10wt%MnTiO3 is 70.5 kJ / mol.

[0131] Experimental Example 1

[0132] The structure and properties of the MgH2-8wt%MnTiO3 composite material prepared in Example 1 were analyzed, such as... Figures 1-9b As shown:

[0133] Figure 1 The XRD pattern of the nanodisc MnTiO3 catalyst prepared in Example 1 is shown below. Figure 1 It can be observed that the MnTiO3 nanodiscs have high crystallinity and correspond to the peak position of the standard PDF card PDF#77-1858, indicating that the sample was successfully prepared.

[0134] Figure 2 SEM image of the MnTiO3 nanodiscs prepared in Example 1, from... Figure 2 As can be seen from the data, the prepared MnTiO3 has a good disk shape, with a disk diameter of 200-400 nm, an average thickness of about 45 nm, and is evenly distributed in size and well dispersed.

[0135] Figure 3 is a TEM (a) and HRTEM (b) image of the MnTi03nanodisks prepared in Example 1. Figure 3a ) and HRTEM image (b). Figure 3b The microstructure of the single nanodisk is given, which is consistent with the shape and size of the nanodisk, and the lattice fringes in the HRTEM image (b) further prove the successful preparation of the MnTi03nanodisk. Figure 3a Figure 2 The microstructure of the single nanodisk is given, which is consistent with the shape and size of the nanodisk, and the lattice fringes in the HRTEM image (b) further prove the successful preparation of the MnTi03nanodisk. Figure 3b

[0136] Figure 4 Figure 4 is a representative SEM image of the MgH2-8 wt% MnTi03ball-milled sample prepared in Example 1 and Mg, Mn and Ti element mapping images obtained by performing different element composition scanning, wherein Figure 4(a) is a representative SEM image of the MgH2-8 wt% MnTi03ball-milled sample prepared in Example 1, Figure 4(b) is a Mg element mapping image, Figure 4(c) is a Mn element mapping image, and Figure 4(d) is a Ti element mapping image. Figure 4 It can be seen that the MnTi03is uniformly dispersed on the surface of the MgH2under the stress action of ball milling, and there is no obvious aggregation, which provides uniform active sites for subsequent catalysis.

[0137] Figure 5 is a representative TEM image (a), HRTEM image (b) and SAED image (c) of the rehydrogenated MgH2-8 wt% MnTi03sample prepared in Example 1, wherein Figure 5(a) is a representative TEM image of the rehydrogenated MgH2-8 wt% MnTi03sample prepared in Example 1, Figure 5(b) is a HRTEM image, and Figure 5(c) is a SAED image. Figure 5a It can be seen that the specific characteristics of the microstructure of the prepared MgH2-8 wt% MnTi03, Figure 5b the lattice fringes prove that the phase of the sample after rehydrogenation changes, and new phases such as magnesium manganese oxide Mg6Mn08and titanium dioxide Ti02are generated, Figure 5c the diffraction ring also proves the generation of the phase. Figure 5a Figure 5b Figure 5c

[0138] Figure 6a Figure 6 is a DSC curve (10℃ / min) of MgH2doped with different contents of MnTi03catalyst; Figure 6b Figure 7 is a thermal desorption (TPD) curve (5℃ / min) of the MgH2-8 wt% MnTi03prepared in Example 1, wherein Deh01is the first thermal desorption, Deh02is the second thermal desorption, and Deh03is the third thermal desorption; it can be seen from Figure 7 that the dehydrogenation peak temperature of the magnesium-based composite material after adding 3 wt% MnTi03decreases by 38℃ compared with that without adding the catalyst, which indicates that MnTi03has catalytic properties for the dehydrogenation of MgH2, and the entire reaction process is one-step dehydrogenation, which indicates that the catalyst is uniformly dispersed; with the increase of the amount of MnTi03added, the dehydrogenation peak temperature of MgH2continuously decreases, and when 8 wt% MnTi03is doped, the dehydrogenation performance (326.1℃) and the hydrogen storage capacity tend to be optimal. Figure 6a Figure 6b ​​​​​​It can be seen that MgH2-8 wt. % MnTiO3 has a lower initial dehydrogenation temperature and the performance is further improved from the second thermal desorption, indicating that the catalytic performance is further enhanced after the first thermal desorption, which can be attributed to the new phase of magnesium manganese oxide Mg6MnO8 and titanium dioxide TiO2 generated in Figure 5. Figure 6b It can be seen that the curves of the second thermal desorption and the third thermal desorption are nearly coincident, indicating that the new phase such as magnesium manganese oxide Mg6MnO8 and titanium dioxide TiO2 generated after the first dehydrogenation improves the dehydrogenation performance in subsequent cycles and can be maintained.

[0139] Figure 6c It is further shown on the basis of Figure 6b the curve relationship between the first thermal desorption and the second thermal desorption; Figure 6d It is further shown on the basis of Figure 6b the curve relationship between the first thermal desorption and the third thermal desorption.

[0140] Figure 7 is an isothermal hydrogenation curve of MgH2-8 wt. % MnTiO3 prepared in Example 1 at different temperatures, and an isothermal dehydrogenation curve of MgH2-8 wt. % MnTiO3 at different temperatures, the initial hydrogen pressure for absorption is 3 MPa, and the initial hydrogen pressure for desorption is 0.005 MPa. It can be seen from Figure 7 that MgH2-8 wt. % MnTiO3 can absorb 3.52 wt. % H2( Figure 7a ) within 25 s at 100°C and release 5.71 wt. % H2( Figure 7b ) within 500 s at 300°C, having very excellent hydrogen absorption and desorption kinetics.

[0141] Figure 8a Figure 8 is an isothermal hydrogenation and dehydrogenation cycle kinetics curve of MgH2-8 wt. % MnTiO3 prepared in Example 1 from the 1st to the 50th cycle at 275°C; Figure 8b Figure 9 is a graph of the relationship between hydrogen absorption / desorption capacity of MgH2-8 wt. % MnTiO3 prepared in Example 1 from the 1st to the 50th cycle at 275°C, from Figure 8a , 8b It can be found that the capacity and kinetics of MgH2-8 wt. % MnTiO3 do not change significantly after 50 hydrogen absorption and desorption cycles, and the composite system has stable hydrogen absorption and desorption cycle, and the hydrogen storage amount is still nearly 94.4% after 50 cycles, which indicates that the composite sample still has a high capacity retention rate after a long time of cycle.

[0142] Figure 9a Figure 10 is a DSC curve of MgH2-8 wt. % MnTiO3 prepared in Example 1 at different heating rates of 5, 8, 10 and 13°C / min;Figure 9b The Kissinger plot of the dehydrogenation activation energy of MgH2-8 wt% MnTiO3 prepared in Example 1 was fitted from the DSC dehydrogenation data at different heating rates, and the dehydrogenation activation energy of MgH2-8 wt% MnTiO3 at different heating rates was 72.06 kJ / mol, which was much lower than that of pure MgH2 (160 kJ / mol), indicating that the dehydrogenation performance of the composite sample was improved. Figure 9a The Kissinger plot of the dehydrogenation activation energy of MgH2-8 wt% MnTiO3 prepared in Example 1 was fitted from the DSC dehydrogenation data at different heating rates, and the dehydrogenation activation energy of MgH2-8 wt% MnTiO3 at different heating rates was 72.06 kJ / mol, which was much lower than that of pure MgH2 (160 kJ / mol), indicating that the dehydrogenation performance of the composite sample was improved.

[0143] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. The present application can have various modifications and changes for those skilled in the art. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A solid-state hydrogen storage composite material, characterized in that, The solid-state hydrogen storage composite material is MgH2-MnTiO3, which comprises 3wt%-10wt% of MnTiO3 catalyst and 90wt%-97wt% of MgH2. The MnTiO3 catalyst is in the shape of nanodisc. The diameter of the nanodisc is 200-400nm, and the thickness is <100nm.

2. The solid-state hydrogen storage composite of claim 1, wherein, The solid-state hydrogen storage composite material is MgH2-8wt% MnTiO3, which comprises 8wt% of MnTiO3 catalyst and 92wt% of MgH2.

3. The solid-state hydrogen storage composite material according to claim 1, wherein, The diameter of the nanodisc is 200-350nm.

4. The solid-state hydrogen storage composite of claim 1, wherein, The thickness of the nanodisc is 35nm-85nm.

5. The solid-state hydrogen storage composite of claim 1, wherein, The thickness of the nanodisc is 45nm.

6. The solid-state hydrogen storage composite of claim 1, wherein, The particle size of MgH2 is 100-500nm.

7. A method of producing a solid-state hydrogen storage composite material as claimed in any one of claims 1 to 6, characterized in that, The method comprises the following steps: S1, preparation of MnTiO3 catalyst; S2, preparation of MgH2; S3, ball milling of the MnTiO3 catalyst and MgH2 to obtain the solid-state hydrogen storage composite material.

8. The preparation method according to claim 7, characterized in that, The MgH2 is prepared by hydrogenation combustion synthesis in step S2.

9. The preparation method according to claim 7, characterized in that, The ball milling is performed under protection of inert atmosphere.

10. The method of claim 9, wherein, The inert atmosphere is argon.

11. The preparation method according to claim 7, characterized in that, The ball milling is performed for 8-10h, the ball-to-material ratio is 25-35:1, and the rotation speed is 300-500r / min.

12. The method of claim 7, wherein, The ball milling is performed for 10h with the ball-to-material ratio of 30:1, the rotation speed of 400r / min, and the forward and reverse alternating operation mode, wherein the ball milling is stopped for 6min every 30min.

13. The preparation method according to claim 7, characterized in that, The ball milling is performed by using a planetary high-energy ball mill.

14. The preparation method according to claim 7, characterized in that, The preparation of the MnTiO3 catalyst specifically comprises the following steps: S1-1, a proper amount of titanium source is measured and added into a stirring solvent to uniformly mix the titanium source and the solvent to obtain solution A; S1-2, a manganese source is weighed and added into a solvent to stir and fully dissolve the manganese source to obtain solution B; S1-3, solution A and solution B are mixed, and deionized water is added to continue stirring to obtain a mixed solution; S1-4, the mixed solution obtained in step S1-3 is subjected to hydrothermal treatment, centrifugation, cleaning, and vacuum drying to obtain MnTiO3 nanodisc.

15. The method of claim 14, wherein, The titanium source in step S1-1 comprises tetrabutyl titanate. And / or, the solvent in step S1-1 comprises ethylene glycol.

16. The method of claim 14, wherein, The stirring mode in step S1-1 is magnetic stirring.

17. The preparation method according to claim 14, characterized in that, The magnetic stirring time after adding the titanium source in step S1-1 is 10-20min.

18. The method of claim 14, wherein, The manganese source in step S1-2 is manganese salt.

19. The method of claim 14, wherein, The manganese source in step S1-2 is MnCl2. And / or, the solvent in step S1-2 comprises ethylenediamine.

20. The method of claim 14, wherein, The stirring mode in step S1-2 is magnetic stirring.

21. The method of claim 20, wherein, The magnetic stirring time is 30-40min.

22. The method of claim 14, wherein, In the mixed solution, the molar ratio of Mn and Ti in the titanium source and the manganese source is 1:

1.

23. The preparation method according to claim 14, wherein, The reaction temperature during the hydrothermal treatment is 180-200℃.

24. The method of claim 14, wherein, The reaction time during the hydrothermal treatment is 24-36h.

25. The method of claim 14, wherein, The hydrothermal treatment in steps 1-4 specifically comprises pouring the mixed solution obtained in step S1-3 into a Teflon-lined container, loading the container into a reaction kettle, and placing the reaction kettle in a constant-temperature oven for hydrothermal reaction; the yellow precipitate C after the hydrothermal reaction is subjected to centrifugal treatment, and repeatedly washed with deionized water and anhydrous ethanol for multiple times, respectively, to obtain a deep yellow centrifugate, and vacuum drying the centrifugate to obtain MnTiO3 nanodiscs.

26. The method of claim 25, wherein, The centrifugal rate of the centrifugal treatment is 6000-8000 rpm.

27. The method of claim 25, wherein The temperature of the vacuum drying is 60-80 DEG C.

28. The preparation method according to claim 25, characterized in that, The vacuum drying time is 8-12 h.

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