NiFe / CoFe nano-catalyst for solid hydrogen storage as well as preparation method and application of NiFe / CoFe nano-catalyst

Abstract

The invention discloses a NiFe / CoFe nano-catalyst for solid hydrogen storage as well as a preparation method and application of the NiFe / CoFe nano-catalyst. The NiFe / CoFe nano-catalyst comprises 25-50wt% of ferronickel and 75-50wt% of ferrocobalt. The particle size of the NiFe / CoFe nano-catalyst is 50-100 nm, the proportion of NiFe / CoFe is 3-15 wt%, and the balance is MgH2. According to the magnesium-based composite hydrogen storage material, MgH2 is subjected to synergistic catalytic modification by using NiFe / CoFe ternary transition metal nanoparticles loaded on the surface of the MgH2, so that the dynamic performance of the MgH2 is remarkably improved, the thermodynamic performance can be improved to a certain extent, and the magnesium-based composite hydrogen storage material with rapid hydrogen absorption and desorption characteristics is obtained.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid-state hydrogen storage, and in particular relates to a NiFe / CoFe nanocatalyst for solid-state hydrogen storage, a preparation method thereof and an application thereof. Background Art

[0002] At present, hydrogen storage technology can be divided into three main types: high-pressure gas, low-temperature liquid and metal hydride solid. Although the first two technologies perform well under specific conditions, they are limited by efficiency, cost or safety issues. It is difficult to meet the future human demand for energy use in scenarios that cannot be used. Metal hydride hydrogen storage, especially magnesium-based solid hydrogen storage materials (Mg / MgH2), has attracted widespread attention in the field of solid-state hydrogen storage due to its high hydrogen storage density (7.6wt.%), abundant resources and low cost.

[0003] Nevertheless, magnesium-based materials still face challenges such as high operating temperature, strong Mg-H bonds and surface passivation layer, which seriously limit their wide-scale promotion and application. To this end, researchers are working on developing catalysts to optimize the hydrogen adsorption / desorption performance of magnesium-based materials.

[0004] The commercial catalysts currently used for magnesium-based solid-state hydrogen storage materials are too rough in structure and lack special structure and high activity. Laboratory-made catalysts have problems such as high cost, complicated process and long preparation cycle, which are not enough to meet the stringent requirements of fuel cell vehicles and the civilian hydrogen energy market. Summary of the invention

[0005] In order to overcome the above problems in the prior art, the purpose of the present invention is to provide a NiFe / CoFe nanocatalyst and a preparation method and application thereof. The method is simple and easy, has a short experimental cycle and the size of the obtained material can reach nanometer level.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A NiFe / CoFe nanocatalyst for solid-state hydrogen storage, which is an amorphous irregular nanoparticle with a large specific surface area and uniform and abundant active sites, with 25-50wt.% nickel-iron and 75-50wt.% cobalt-iron;

[0008] The particle size of NiFe / CoFe nanocatalyst is 50-100nm, with a large specific surface area and uniform and abundant active sites.

[0009] A method for preparing a NiFe / CoFe nanocatalyst for solid-state hydrogen storage comprises the following steps:

[0010] Step 1: Preparation of multi-component metal ion composite precursor solution

[0011] Weigh sodium nitrate (C5H4FeN6Na2O3), nickel nitrate hexahydrate (Ni(NO3)2·6H2O) and cobalt nitrate hexahydrate (Co(NO3)2·6H2O); dissolve them in deionized water in turn, stir, and the metal particles are combined and precipitated to obtain a light pink opaque mixed solution;

[0012] Step 2: Salt-induced precipitation and solidification

[0013] Add NaCl to the light pink opaque solution, continue stirring to fully dissolve it, seal the container containing the turbid solution with plastic wrap, and let it stand to obtain a NiFe / CoFe nanoparticle precursor;

[0014] Step 3: Liquid phase high temperature purification of precursor

[0015] The NiFe / CoFe nanoparticle precursor is centrifugally washed in an alternating manner of anhydrous ethanol and deionized water to completely remove liquid impurities in the NiFe / CoFe nanoparticle precursor, and the obtained colloidal NiFe / CoFe nanoparticle precursor is dried in a vacuum drying oven, and then the obtained opaque precursor clot is ground using an agate mortar to facilitate subsequent heat treatment, and finally it is placed in a high-temperature tubular furnace for calcination to obtain NiFe / CoFe nanoparticle powder, i.e., NiFe / CoFe nanocatalyst.

[0016] In step 1:

[0017] The masses of C5H4FeN6Na2O3, Ni(NO3)2·6H2O and Co(NO3)2·6H2O are 0.2-0.6 g, 0.2-0.9 g and 0.2-0.6 g respectively; they are dissolved in 80-120 ml of deionized water in turn and stirred vigorously at 800-1000 rpm on a magnetic stirrer for 1-5 min. The metal ions combine and precipitate, and the color of the solution changes from the initial orange transparent to light pink opaque.

[0018] In the step 2, 3.5-7 wt.% NaCl is added as a precipitant to the light pink opaque mixed solution obtained in step 1, and stirring is continued at 800-1000 rpm for 1-5 min to fully dissolve it, thereby accelerating the rate at which the multiphase metal ions in the solution form a precipitate mixture and precipitate. The container containing the turbid solution is sealed with plastic wrap, and is kept at 20-40° C. in the dark for 8-12 h to ensure that the precipitate mixture in the solution is completely precipitated and precipitated, thereby obtaining a NiFe / CoFe nanoparticle precursor.

[0019] In step 3:

[0020] The NiFe / CoFe nanoparticle precursor obtained in step 2 is poured into a 100 ml centrifuge tube, and centrifuged and washed 4 to 6 times at 8000 to 12000 rpm using anhydrous ethanol and deionized water alternately, with each washing time being 3 to 8 minutes, to ensure that the liquid impurities in the NiFe / CoFe nanoparticle precursor are completely removed; the colloidal NiFe / CoFe nanoparticle precursor is vacuum dried for 6 to 12 hours in a vacuum drying oven at a pressure of 0 to -40 bar and a temperature of 50 to 90° C., to ensure that the water in the precursor and the unremoved liquid impurities are completely evaporated and to avoid oxidation of the NiFe / CoFe nanoparticle precursor in contact with air. Subsequently, the obtained opaque precursor agglomerate is ground for 5 to 10 minutes using an agate mortar to convert the block into powder to facilitate subsequent heat treatment. Finally, it is placed in a high-temperature tubular furnace and calcined at 600 to 900° C. in an Ar atmosphere for 2 to 6 hours to obtain NiFe / CoFe nanoparticle powder.

[0021] The NiFe / CoFe nanocatalyst is applied to MgH2 modification to improve the hydrogen absorption and desorption kinetics of magnesium-based solid hydrogen storage materials.

[0022] By using MgH2 catalyzed by NiFe / CoFe nanocatalyst at 350°C, 6.0wt.% of hydrogen can be absorbed in 2 minutes and 6.5wt.% of hydrogen can be released in 30 minutes, and its hydrogen storage capacity can reach 92.8% of the theoretical hydrogen storage capacity. Under this condition, ball-milled MgH2 absorbs 5.6wt.% of hydrogen and releases only 2.3wt.%.

[0023] Beneficial effects of the present invention:

[0024] The present invention proposes a NiFe / CoFe nanocatalyst for improving the hydrogen absorption and desorption kinetics of magnesium-based solid hydrogen storage materials and a preparation method thereof. The method uses different transition metal salts to prepare a uniformly mixed multi-component transition metal ion solution by coprecipitation, and uses cheap NaCl as a precipitant to accelerate the precipitation degradation of the precursor mixture, significantly shortening the preparation cycle.

[0025] Subsequent processes include alternating centrifugal washing with deionized water and anhydrous ethanol, vacuum drying, and high-temperature calcination under inert gas protection, which effectively purify the precursor and remove impurities. The oxygen-free environment created during the vacuum drying process and the inert gas protection measures used during high-temperature calcination avoid contact between transition metal nanoparticles and oxygen, thereby preventing the occurrence of oxidation and ensuring the high purity of the final product.

[0026] The process of the present invention is simple, low-cost and easy to control, and has the potential for commercial and industrial promotion and application. By introducing nano-scale catalysts, the number of active sites on the surface of the MgH2 material can be effectively increased. At the same time, the multi-component transition metal can form an intermediate phase of magnesium-nickel and magnesium-cobalt in the continuous absorption and desorption of hydrogen, and α-Fe provides a channel and path for the diffusion and transmission of hydrogen, thereby significantly improving the absorption and desorption kinetics of MgH2.

[0027] In summary, the present invention provides an efficient, low-cost and easy-to-implement preparation method, and the obtained NiFe / CoFe nanocatalyst has a significant effect on improving the hydrogen absorption and desorption performance of magnesium-based solid hydrogen storage materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The present invention is a flow chart of a method for preparing NiFe / CoFe nanocatalyst for solid-state hydrogen storage.

[0029] Figure 2 The XRD spectrum of the NiFe / CoFe nanocatalyst of the present invention is shown in FIG.

[0030] Figure 3 This is the SEM spectrum of the NiFe / CoFe nanocatalyst of the present invention.

[0031] Figure 4 This is the hydrogen absorption curve of MgH2 modified by NiFe / CoFe nanocatalyst at 350°C of the present invention.

[0032] Figure 5 This is the dehydrogenation curve of MgH2 modified by NiFe / CoFe nanocatalyst at 350°C of the present invention. DETAILED DESCRIPTION

[0033] The present invention will be further described in detail below in conjunction with the accompanying drawings.

[0034] Example 1

[0035] Step 1, preparation of multi-component metal ion composite precursor solution: weigh 0.3g, 0.43g and 0.43g of sodium nitrate (C5H4FeN6Na2O3), nickel nitrate hexahydrate (Ni(NO3)2·6H2O) and cobalt nitrate hexahydrate (Co(NO3)2·6H2O) respectively. Dissolve them in 100ml of deionized water in turn, place them in a magnetic stirrer and stir vigorously at 800rpm for 1min. The metal ions combine and precipitate, and the color of the solution changes from the initial orange transparent to light pink opaque;

[0036] Step 2, salt-induced precipitation and solidification: Add 3.5wt.% NaCl as a precipitant to the light pink opaque mixed solution obtained in step 1 and continue stirring at 800rpm for 1min to fully dissolve it, thereby accelerating the rate at which the multiphase metal ions in the solution form a precipitate mixture and precipitate. Seal the container containing the turbid solution with plastic wrap and place it at 25°C in the dark for 10h to ensure that the precipitate mixture in the solution is completely precipitated and precipitated, thereby obtaining a NiFe / CoFe nanoparticle precursor;

[0037] Step 3, high temperature liquid phase impurity removal and purification of the precursor: Pour the NiFe / CoFe nanoparticle precursor obtained in step 2 into a 100 ml centrifuge tube, and use anhydrous ethanol and deionized water to centrifuge and wash 6 times at 10000 rpm, each washing time is 5 minutes, to ensure that the liquid phase impurities in the NiFe / CoFe nanoparticle precursor are completely removed. The colloidal NiFe / CoFe nanoparticle precursor obtained is vacuum dried for 10 hours in a vacuum drying oven at a pressure of -20 bar and a temperature of 80°C to ensure that the moisture in the precursor and the unremoved liquid phase impurities are completely evaporated and the NiFe / CoFe nanoparticle precursor is prevented from contacting and oxidizing with air. Subsequently, the obtained opaque precursor agglomerate is ground for 5 minutes using an agate mortar to convert the block into powder to facilitate subsequent heat treatment. Finally, it is placed in a high temperature tube furnace and calcined at 800°C for 4 hours under an Ar atmosphere to obtain NiFe / CoFe nanoparticle powder.

[0038] The average particle size of the NiFe / CoFe nanoparticles prepared in this embodiment is 78.8 nm.

[0039] Example 2

[0040] Step 1, preparation of multi-component metal ion composite precursor solution: weigh 0.3g, 0.43g and 0.43g of (C5H4FeN6Na2O3), nickel nitrate hexahydrate (Ni(NO3)2·6H2O) and cobalt nitrate hexahydrate (Co(NO3)2·6H2O) respectively. Dissolve them in 100ml of deionized water in turn, place them in a magnetic stirrer and stir vigorously at 1000rpm for 5min, the metal ions combine and precipitate, and the color of the solution changes from the initial orange transparent to light pink opaque;

[0041] Step 2, salt-induced precipitation and solidification: Add 3.5wt.% NaCl as a precipitant to the light pink opaque mixed solution obtained in step 1 and continue stirring at 1000rpm for 5min to fully dissolve it, thereby accelerating the rate at which the multiphase metal ions in the solution form a precipitate mixture and precipitate. Seal the container containing the turbid solution with plastic wrap and place it at 25°C in the dark for 12h to ensure that the precipitate mixture in the solution is completely precipitated and precipitated, thereby obtaining a NiFe / CoFe nanoparticle precursor;

[0042] Step 3, high temperature liquid phase impurity removal and purification of the precursor: Pour the NiFe / CoFe nanoparticle precursor obtained in step 2 into a 100ml centrifuge tube, and use anhydrous ethanol and deionized water to centrifuge and wash 6 times at 8000rpm, each washing time is 5min, to ensure that the liquid phase impurities in the NiFe / CoFe nanoparticle precursor are completely removed. The colloidal NiFe / CoFe nanoparticle precursor obtained is vacuum dried for 12h in a vacuum drying oven at a pressure of -20bar and a temperature of 60°C to ensure that the moisture in the precursor and the unremoved liquid phase impurities are completely evaporated and to avoid the NiFe / CoFe nanoparticle precursor from contacting and oxidizing with air. Subsequently, the obtained opaque precursor clot is ground for 5min using an agate mortar to convert the block into powder to facilitate subsequent heat treatment. Finally, it is placed in a high temperature tube furnace and calcined at 750°C for 4h under an Ar atmosphere to obtain NiFe / CoFe nanoparticle powder.

[0043] The average particle size of the NiFe / CoFe nanoparticles prepared in this embodiment is 80.2 nm.

[0044] Example 3

[0045] Step 1, preparation of multi-component metal ion composite precursor solution: weigh 0.3g, 0.43g and 0.43g of (C5H4FeN6Na2O3), nickel nitrate hexahydrate (Ni(NO3)2·6H2O) and cobalt nitrate hexahydrate (Co(NO3)26H2O) respectively. Dissolve them in 100ml of deionized water in turn, place them in a magnetic stirrer and stir vigorously at 800rpm for 5min, the metal ions combine and precipitate, and the color of the solution changes from the initial orange transparent to light pink opaque;

[0046] Step 2, salt-induced precipitation and solidification: add 7wt.% NaCl as a precipitant to the light pink opaque mixed solution obtained in step 1 and continue stirring at 800rpm for 5min to fully dissolve it, thereby accelerating the rate at which the multiphase metal ions in the solution form a precipitate mixture and precipitate. Seal the container containing the turbid solution with plastic wrap and place it at 25°C in the dark for 12h to ensure that the precipitate mixture in the solution is completely precipitated and precipitated, thereby obtaining a NiFe / CoFe nanoparticle precursor;

[0047] Step 3, high temperature liquid phase impurity removal and purification of the precursor: Pour the NiFe / CoFe nanoparticle precursor obtained in step 2 into a 100ml centrifuge tube, and use anhydrous ethanol and deionized water to centrifuge and wash 6 times at 10000rpm, each washing time is 5min, to ensure that the liquid phase impurities in the NiFe / CoFe nanoparticle precursor are completely removed. The colloidal NiFe / CoFe nanoparticle precursor obtained is vacuum dried for 11h in a vacuum drying oven at a pressure of -20bar and a temperature of 70°C to ensure that the moisture in the precursor and the unremoved liquid phase impurities are completely evaporated and the NiFe / CoFe nanoparticle precursor is prevented from contacting and oxidizing with the air. Subsequently, the obtained opaque precursor clot is ground for 5min using an agate mortar to convert the block into powder to facilitate subsequent heat treatment. Finally, it is placed in a high temperature tube furnace and calcined at 850°C for 4h under an Ar atmosphere to obtain NiFe / CoFe nanoparticle powder.

[0048] The average particle size of the NiFe / CoFe nanoparticles prepared in this embodiment is 82.1 nm.

[0049] Explanation of the drawings of the present invention

[0050] Figure 1 The flowchart is a method for preparing NiFe / CoFe nanocatalysts for solid-state hydrogen storage. The method can be divided into the following steps: (1) dissolving metal nitrate in ethanol - preparation of multi-component metal ion composite precursor solution; (2) adding NaCl to adjust the pH of the solution - salt-induced precipitation and solidification; (3) centrifugal washing, vacuum drying and high-temperature calcination - high-temperature liquid-phase impurity removal and purification of the precursor.

[0051] Figure 2 The XRD spectrum of the NiFe / CoFe nanocatalyst of the present invention is shown in Figure 1. It can be confirmed that the NiFe / CoFe nanocatalyst is successfully prepared in the present invention.

[0052] Figure 3 The SEM image of the NiFe / CoFe nanocatalyst of the present invention is shown in Figure 1. It can be seen that the NiFe / CoFe nanocatalyst is composed of amorphous irregular nanoparticles, and the particle size thereof is between 50 and 100 nm.

[0053] Figure 4 The figure is a comparison of hydrogen absorption performance before and after the modification of MgH2 by the NiFe / CoFe nanocatalyst of the present invention. As can be seen from the figure, under the same experimental conditions, the hydrogen absorption of ball-milled magnesium hydride in 10 minutes is only 3.9wt.%, while the hydrogen absorption of magnesium hydride modified by the NiFe / CoFe nanocatalyst in 10 minutes can quickly reach 6.0wt.%, which is much higher than that of ball-milled magnesium hydride. And after absorbing hydrogen for 60 minutes, the final hydrogen absorption of ball-milled magnesium hydride is about 4.0wt.%. The final hydrogen absorption of magnesium hydride modified by the NiFe / CoFe nanocatalyst is 6.3wt.%, which is about 92% of the theoretical hydrogen storage capacity.

[0054] Figure 5 The figure is a comparison of the dehydrogenation performance before and after the modification of MgH2 using the NiFe / CoFe nanocatalyst of the present invention. It can be seen from the figure that under the same experimental conditions, the dehydrogenation rate of ball-milled magnesium hydride is slower than that of the sample modified by NiFe / CoFe catalysis. The sample modified by catalysis can dehydrogenate 2.5wt.% in 10min, while the dehydrogenation amount of ball-milled magnesium hydride in 10min is negligible. The magnesium hydride modified by catalysis can dehydrogenate 5.0wt.% in 60min, while the dehydrogenation amount of ball-milled magnesium hydride is only half of the dehydrogenation amount of the sample modified by catalysis, about 2.5wt.%.

[0055] In summary, the NiFe / CoFe nanocatalyst prepared by the present invention can significantly improve the hydrogen absorption and desorption performance of MgH2. The preparation method of the catalyst is simple, low-cost and short-cycle. These characteristics provide a solid theoretical support and experimental basis for the catalyst development and subsequent research of magnesium-based solid hydrogen storage materials.

Claims

1. A NiFe / CoFe nanocatalyst for solid-state hydrogen storage, characterized in that: Amorphous irregular nanoparticles, 25-50wt.% nickel-iron, 75-50wt.% cobalt-iron; The particle size of the NiFe / CoFe nanocatalyst is 50 to 100 nm.

2. The method for preparing a NiFe / CoFe nanocatalyst for solid-state hydrogen storage according to claim 1, characterized in that: The following steps are involved: Step 1: Preparation of multi-component metal ion composite precursor solution Weigh sodium nitrate (C5H4FeN6Na2O3), nickel nitrate hexahydrate (Ni(NO3)2·6H2O) and cobalt nitrate hexahydrate (Co(NO3)2·6H2O); dissolve them in deionized water in turn, stir, and the metal particles are combined and precipitated to obtain a light pink opaque mixed solution; Step 2: Salt-induced precipitation and solidification Add NaCl to the light pink opaque solution, continue stirring to fully dissolve it, seal the container containing the turbid solution with plastic wrap, and let it stand to obtain a NiFe / CoFe nanoparticle precursor; Step 3: Liquid phase high temperature purification of precursor The NiFe / CoFe nanoparticle precursor is centrifugally washed in an alternating manner of anhydrous ethanol and deionized water to completely remove liquid impurities in the NiFe / CoFe nanoparticle precursor, and the obtained colloidal NiFe / CoFe nanoparticle precursor is dried in a vacuum drying oven, and then the obtained opaque precursor clot is ground using an agate mortar to facilitate subsequent heat treatment, and finally placed in a high-temperature tubular furnace for calcination to obtain NiFe / CoFe nanoparticle powder, i.e., NiFe / CoFe nanocatalyst.

3. The method for preparing a NiFe / CoFe nanocatalyst for solid-state hydrogen storage according to claim 2, characterized in that: In step 1: The masses of C5H4FeN6Na2O3, Ni(NO3)2·6H2O and Co(NO3)2·6H2O are 0.2-0.6 g, 0.2-0.9 g and 0.2-0.6 g respectively; they are dissolved in 80-120 ml of deionized water in turn and stirred vigorously at 800-1000 rpm on a magnetic stirrer for 1-5 min. The metal ions combine and precipitate, and the color of the solution changes from the initial orange transparent to light pink opaque.

4. The method for preparing a NiFe / CoFe nanocatalyst for solid-state hydrogen storage according to claim 2, characterized in that: In the step 2, 3.5-7 wt.% NaCl is added as a precipitant to the light pink opaque mixed solution obtained in step 1, and stirring is continued at 800-1000 rpm for 1-5 min to fully dissolve it. The container containing the turbid solution is sealed with plastic wrap and placed in a dark place at 20-40° C. for 8-12 h to ensure that the precipitate mixture in the solution is completely precipitated and precipitated, thereby obtaining a NiFe / CoFe nanoparticle precursor.

5. The method for preparing a NiFe / CoFe nanocatalyst for solid-state hydrogen storage according to claim 2, characterized in that: In step 3: The NiFe / CoFe nanoparticle precursor obtained in step 2 is poured into a centrifuge tube, and centrifuged and washed 4 to 6 times at 8000 to 12000 rpm using anhydrous ethanol and deionized water alternately, with each washing time being 3 to 8 minutes; the colloidal NiFe / CoFe nanoparticle precursor is vacuum dried in a vacuum drying oven at a pressure of 0 to -40 bar and a temperature of 50 to 90° C. for 6 to 12 hours, and then the opaque precursor clot is ground using an agate mortar for 5 to 10 minutes to convert the block into powder to facilitate subsequent heat treatment, and finally placed in a high-temperature tubular furnace under an Ar atmosphere at 600 to 900° C. for calcination for 2 to 6 hours to obtain NiFe / CoFe nanoparticle powder.

6. The use of a NiFe / CoFe nanocatalyst for solid-state hydrogen storage according to any one of claims 1 to 5, characterized in that: The NiFe / CoFe nanocatalyst is applied to MgH2 modification to improve the hydrogen absorption and desorption kinetics of magnesium-based solid hydrogen storage materials.

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