Preparation method and application of a two-phase nanorod catalyst

Abstract

The application relates to a preparation method of a two-phase nanorod catalyst and application thereof, and belongs to the field of hydrogen storage material catalysts. The preparation method comprises the following steps: weighing iron trichloride hexahydrate, cobalt acetate tetrahydrate, nickel acetate tetrahydrate, sodium molybdate, ammonium metavanadate and terephthalic acid according to a molar ratio of 6:6:6:6:6:(1-2) to obtain a mixture; stirring the mixture in deionized water to obtain a homogeneous solution, carrying out a hydrothermal reaction to form rod-shaped crystals, and finally obtaining a light yellow precursor powder; the two-phase nanorod catalyst FeCoNiMoV-O / C is obtained through reasonable proportioning, grinding, calcining and cooling of different raw materials, has excellent catalytic performance, and significantly improves the hydrogen absorption and desorption kinetics of MgH2.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of hydrogen energy and the field of hydrogen storage material catalyst, and particularly relates to a preparation method of a two-phase nanorod catalyst and application thereof, and is used for improving the performance of MgH2 solid-state hydrogen storage material. BACKGROUND

[0002] As a secondary clean energy, hydrogen has the great advantages of high energy, no pollution and rich reserves, and is an important part of the energy structure in China.

[0003] A hydrogen energy system is composed of hydrogen production technology, hydrogen storage technology, hydrogen transportation technology and hydrogen utilization technology, and the hydrogen storage technology is a key link. Hydrogen can be stored in the form of low-temperature liquid, high-pressure gas or solid-state material. From the development demand of hydrogen economy, the storage system must be safe, efficient, economical, light and compact. In order to achieve this goal, solid-state hydrogen storage material becomes the research focus. The technical core of solid-state hydrogen storage is hydrogen storage material, which can reversibly absorb and release hydrogen and has high safety. Therefore, improving the absorption and release performance of MgH2 hydrogen storage material and researching catalyst materials for accelerating the adsorption and dissociation of hydrogen on MgH2 become the focus in the field of hydrogen storage technology. SUMMARY

[0004] The technical problem to be solved by the application is how to accelerate the adsorption and dissociation of hydrogen on MgH2, and a preparation method of a two-phase nanorod catalyst and application thereof are provided.

[0005] The technical solution of the application for solving the above technical problem is as follows: a preparation method of a two-phase nanorod catalyst, comprising the following steps:

[0006] Step (1), accurately weighing ferric chloride hexahydrate (FeCl3·6H2O, 99.9%), cobalt acetate tetrahydrate (Co(CH3COO)2·4H2O, 99.95%), nickel acetate tetrahydrate (Ni(CH3COO)2·4H2O, 99.98%), sodium molybdate (Na2MoO4, 99.99%), ammonium metavanadate (NH4VO3, 99.9%) and terephthalic acid (C6H4(CO2H)2, 99.8%) in a molar ratio of 6:6:6:6:6: (1-2) to obtain a mixture;

[0007] Step (2), adding the mixture into deionized water, and placing it on a constant-temperature magnetic stirrer to obtain a wine-red homogeneous solution by stirring at 85±5℃, and the molar solid-liquid mass ratio of the mixture to deionized water is 94-187 mmol / kg;

[0008] Step (3), the homogeneous solution is transferred to a high-pressure reaction kettle, and after being sealed, is placed in a vacuum drying oven to perform a hydrothermal reaction, rod-shaped crystals are formed and grow along crystal faces, and after the reaction is completed, the rod-shaped crystals are naturally cooled at room temperature, and after being separated, washed, and dried in an oven, a light yellow precursor powder is obtained;

[0009] Step (4), the light yellow precursor powder is ground, calcined, and cooled to obtain a black FeCoNiMoV-O / C biphase nanorod catalyst.

[0010] Based on the technical scheme, the application further has the following improvements.

[0011] Further, in the preparation method of the biphase nanorod catalyst, in step (2), the pH value of the wine-red homogeneous solution is controlled to be in the range of 2.5-3.0. Since Mo and V elements are prone to hydrolysis, the pH value is controlled to be in the range of 2.5-3.0, so that the precipitation can be effectively prevented from being formed in advance.

[0012] Further, in the preparation method of the biphase nanorod catalyst, in step (2), the pH value is adjusted by using 0.1M HCl.

[0013] Further, in the preparation method of the biphase nanorod catalyst, in step (2), the magnetic stirrer is arranged to be stirred at a speed of 80-100 rpm for 45 min.

[0014] Further, in the preparation method of the biphase nanorod catalyst, in step (3), the hydrothermal reaction is performed in a stepwise temperature rising process.

[0015] Further, in the stepwise temperature rising process, the temperature is raised to 120℃ at a speed of 5℃ / min and is kept for 1 h, then the temperature is continuously raised to 160℃ and is kept for 1 h, and finally the reaction is performed at 200℃ for 12 h. The gradient design can promote the growth of rod-shaped crystals along the crystal faces and avoid the morphology unevenness caused by sudden nucleation.

[0016] Further, in the preparation method of the biphase nanorod catalyst, the grinding is performed in an agate mortar, and the calcination is performed in a tube furnace, and after the calcination is completed, the furnace is cooled.

[0017] Further, in the preparation method of the biphase nanorod catalyst, the calcination is performed in a 5%H2 / Ar or Ar protective atmosphere.

[0018] Further, in the preparation method of the biphase nanorod catalyst, the calcination temperature is raised to 550℃ at a speed of 5℃ / min and is kept for 1.5 h. The raising speed and the keeping parameter can effectively prevent the carbon skeleton from being excessively graphitized.

[0019] Further, as described above, in the preparation method of the dual-phase nanorod catalyst, the separation in step (3) is centrifugal separation at 10000 rpm for 5 min, and the washing is washing with deionized water and anhydrous ethanol alternately for 3 times each, so as to completely remove the residual ions.

[0020] The application further provides a composite hydrogen storage material, wherein the dual-phase nanorod catalyst prepared by the preparation method is compounded with MgH2, and the mass ratio of the dual-phase nanorod catalyst to MgH2 ranges from 0.01 wt% to 10 wt%.

[0021] The application has the beneficial effects that: the FeCoNiMoV-O / C dual-phase nanorod catalyst is obtained by hydrothermal synthesis and high-temperature calcination process, and the performance of the MgH2 solid-state hydrogen storage material can be effectively improved.

[0022] The catalyst obtained by the application has a stick-like structure, provides a high surface area, and is a non-high-entropy catalyst with excellent catalytic performance, which significantly improves the hydrogen absorption and desorption kinetics of MgH2. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 FIG. 1 is a picture of the dual-phase nanorod catalyst powder prepared in Example 1.

[0024] Figure 2 FIG. 3 is an XRD of the dual-phase nanorod catalyst powder prepared in Example 1.

[0025] Figure 3 FIG. 5 is an SEM of the dual-phase nanorod catalyst powder prepared in Example 1.

[0026] Figure 4 FIG. 7 is an EDS picture of the dual-phase nanorod catalyst powder prepared in Example 1.

[0027] Figure 5 FIG. 9 is a TEM picture of the dual-phase nanorod catalyst powder prepared in Example 1.

[0028] Figure 6 FIG. 11 is an EDS picture of the dual-phase nanorod catalyst powder prepared in Example 1 compounded with MgH2.

[0029] Figure 7 FIG. 13 is a performance picture of the dual-phase nanorod catalyst powder prepared in Example 1 catalyzing MgH2, wherein (a) is hydrogen absorption performance, and (b) is hydrogen desorption performance. DETAILED DESCRIPTION

[0030] The principles and characteristics of the application are described below in combination with the drawings, and the examples are only used to explain the application and are not used to limit the scope of the application.

[0031] Example 1

[0032] The preparation method of the dual-phase nanorod catalyst comprises the following steps:

[0033] Step (1), 3 mmol of FeCl3·6H2O, 3 mmol of Co(CH3COO)2·4H2O, 3 mmol of Ni(CH3COO)2·4H2O, 3 mmol of Na2MoO4, 3 mmol of NH4VO3 and 0.6 mmol of terephthalic acid are dissolved in 100 mL of deionized water to obtain a mixture;

[0034] Step (2), the mixture is added to deionized water and placed on a constant-temperature magnetic stirrer, and stirred at a speed of 80-100 rpm for 45 min, and a wine-red homogeneous solution is obtained by stirring at 85±5°C. The pH value is adjusted to 2.5-3.0 by using 0.1M HCl, and the molar solid-liquid mass ratio of the mixture to deionized water is 94 mmol / kg;

[0035] Step (3), the homogeneous solution is transferred to a high-pressure reaction kettle, sealed and placed in a vacuum drying box for hydrothermal reaction. In the process of stepwise temperature rise, the rod-shaped crystals grow along the crystal face. In the process of stepwise temperature rise, the temperature is raised to 120°C at a rate of 5°C / min and kept for 1 h, then the temperature is continuously raised to 160°C and kept for 1 h, and finally the reaction is carried out at 200°C for 12 h. The reaction is naturally cooled to room temperature, centrifuged at 10000 rpm for 5 min, washed with deionized water and anhydrous ethanol alternately for 3 times each, and the residual ions are completely removed. After drying in an oven, a light yellow precursor powder is obtained;

[0036] Step (4), the light yellow precursor powder is ground in a marver mortar and placed in a tube furnace. Under the protection of 5% H2 / Ar or Ar, the temperature is raised to 550°C at a rate of 5°C / min and kept for 1.5 h. After the calcination is completed, the furnace is cooled to obtain a black FeCoNiMoV-O / C dual-phase nanorod catalyst.

[0037] Figure 1 The macroscopic morphology and physical state of the dual-phase nanorod catalyst powder obtained in Example 1 are shown. The color is black powder. The powder morphology is composed of rod-shaped or nanorod-shaped particles, rather than agglomerated particles or powder, which directly reflects the morphology characteristics of the hydrothermal synthesis.

[0038] The XRD pattern is a core tool for analyzing the crystal structure and phase composition of a material. Through the position (2θ angle) and intensity of the diffraction peak, it can be accurately judged which crystal phases exist in the powder. As shown in Example 1, the XRD of the dual-phase nanorod catalyst powder prepared in Example 1 is shown. Figure 2 Figure 2 ​Two distinct clusters of diffraction peaks appear. First phase (Fe3O4): its diffraction peaks should be consistent with those of the standard PDF card (e.g., JCPDS 19-0629). Second phase (FeNi3): its diffraction peaks should be consistent with those of the FeNi3 alloy metallic phase in the standard PDF card.

[0039] Crystallinity can also be determined by peak shape: the sharpness and intensity of the peaks reflect the degree of crystallinity of the material. A sharper peak indicates good crystallinity; a wider peak indicates that the material has nanoscale grain size. Figure 2 The biphase nanorod catalyst powder shown has sharp peaks, indicating good crystallinity.

[0040] Phase purity: based on Figure 2 The biphase nanorod catalyst powder shown has no diffraction peaks from other impurity phases (such as unreacted precursors), proving that the biphase nanorod catalyst powder was successfully synthesized.

[0041] SEM images are used to characterize the surface morphology and particle size of materials, and are the most direct way to observe the microstructure of nanomaterials. For example... Figure 3 SEM image of the biphase nanorod catalyst powder prepared in Example 1 shown. Figure 3 A large number of one-dimensional rod-shaped or nanorod-shaped particles are clearly visible in the sample, which are relatively uniformly dispersed with slight agglomeration.

[0042] EDS plots are used for elemental analysis to confirm whether the material contains the expected elements. For example... Figure 4 The EDS image of the biphase nanorod catalyst powder prepared in Example 1 shows uniform cross-sectional scans of elements such as Fe, Co, Ni, Mo, V, and O, confirming that all of them contain the expected elements.

[0043] TEM images can provide more detailed microstructure information than SEM, allowing observation of the internal structure, lattice fringes, and phase interfaces of individual nanorods. Figure 5 This is a TEM image of the biphase nanorod catalyst powder prepared in Example 1. Figure 5 The internal lattice fringes of a single nanorod can be clearly seen, which is direct evidence that the material has a crystalline structure.

[0044] Example 2

[0045] Preparation of composite hydrogen storage materials

[0046] The biphase nanorod catalyst prepared by the method in Example 1 was combined with MgH2, and the mass ratio of the biphase nanorod catalyst to MgH2 was 5 wt%.

[0047] like Figure 6The EDS images of the biphase nanorod catalyst powder of embodiment 1 before / after hydrogen absorption of MgH2, the uniform surface scanning images of Mg, Fe, Co, Ni, Mo, V, O, C and other elements appear in the images, confirming that the material contains the expected elements.

[0048] As Figure 7 The performance chart of the biphase nanorod catalyst powder of embodiment 1 for catalyzing MgH2, (a) is the hydrogen absorption performance and (b) is the hydrogen release performance, from Figure 7 (a) is the kinetic hydrogen absorption chart of MgH2 and MgH2 compounded biphase nanorod catalyst at 300℃, and (b) is the kinetic hydrogen release chart of MgH2 and MgH2 compounded biphase nanorod catalyst at 300℃, it can be seen that the hydrogen absorption and release kinetics of MgH2 is significantly improved.

[0049] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a bi-phase nanorod catalyst, characterized in that, The first phase of the two-phase is Fe3O4, and the second phase is FeNi3, comprising the following steps: Step (1), weighing ferric chloride hexahydrate, cobalt acetate tetrahydrate, nickel acetate tetrahydrate, sodium molybdate, ammonium metavanadate, and terephthalic acid according to a molar ratio of 6:6:6:6:6: (1-2) to obtain a mixture; Step (2), adding the mixture to deionized water and stirring at 85±5°C to obtain a homogeneous solution, wherein the molar solid-liquid mass ratio of the mixture to deionized water is 94-187 mmol / kg; Step (3), subjecting the homogeneous solution to a hydrothermal reaction to form rod-shaped crystals, and obtaining a precursor powder after cooling, separation, washing, and drying after the reaction is completed; the hydrothermal reaction is carried out in a stepwise heating process, wherein the stepwise heating process is to increase the temperature to 120°C at a rate of 5°C / min and keep it for 1h, then continue to increase the temperature to 160°C and keep it for 1h, and finally react at 200°C for 12h; Step (4), grinding, calcining, and cooling the precursor powder to obtain a black FeCoNiMoV-O / C two-phase nanorod catalyst; The calcination is carried out in a 5% H2 / Ar or Ar protective atmosphere, and the calcination temperature is increased to 550°C at a rate of 5°C / min and kept for 1.5h.

2. The method for preparing the biphase nanorod catalyst according to claim 1, characterized in that, In step (2), the pH value of the homogeneous solution is controlled in the range of 2.5-3.

0.

3. The method for preparing the biphase nanorod catalyst according to claim 1, characterized in that, In step (2), the stirring is carried out at a magnetic stirrer speed of 80-100 rpm for 45 min.

4. The method for preparing the biphase nanorod catalyst according to claim 1, characterized in that, In step (4), the grinding is carried out in an agate mortar, and the calcination is carried out in a tube furnace, and the sample is cooled in the furnace after the calcination is completed.

5. The method of claim 1 to 4, wherein the preparation of the bi-phase nanorod catalyst is characterized by, In step (3), the separation is carried out by centrifugation at 10000 rpm for 5 min, and the washing is carried out by using deionized water and anhydrous ethanol alternately until the residual ions are completely removed.

6. The application of the two-phase nanorod catalyst obtained by the preparation method of any one of claims 1 to 5 in a MgH2 hydrogen storage system.

7. A composite hydrogen storage material, characterized by, The two-phase nanorod catalyst prepared by the preparation method of any one of claims 1 to 5 is compounded with MgH2, and the mass ratio of the two-phase nanorod catalyst to MgH2 is in the range of 0.01wt% to 10wt%.

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