Preparation method of nanocrystalline (FeCoNiCrMn)3O4 porous high entropy oxide

Abstract

The present invention discloses a method for preparing a nanocrystalline (FeCoNiCrMn)3O4 porous high-entropy oxide, which belongs to the technical field of high-entropy ceramic material preparation. The method for preparing the nanocrystalline (FeCoNiCrMn)3O4 porous high-entropy oxide disclosed in the present invention is as follows: using dimethylimidazole as a ligand and triethylamine as a precursor crystallization regulator, respectively using nitrates of Fe, Co, Ni, Cr, and Mn as metal ion sources, and stirring the metal organic framework precursor formed at room temperature and calcining it in a muffle furnace air atmosphere to obtain the nanocrystalline (FeCoNiCrMn)3O4 porous high-entropy oxide. The nanocrystalline (FeCoNiCrMn)3O4 porous high-entropy oxide prepared by the present invention has a spinel crystal structure, a grain size of 100nm-200nm, a pore size of 20-50nm, a high specific surface area, and can be used as a chemical catalyst, energy storage material, coating material, high-temperature structural material, etc.

Description

Technical Field

[0001] The invention discloses a preparation method of nanocrystalline (FeCoNiCrMn)3O4 porous high-entropy oxide, belonging to the technical field of high-entropy ceramic material preparation. Background Art

[0002] High-entropy oxides (HEOs) are typically synthesized by solid-solution of five or more oxides in equimolar or near-equimolar ratios to form a single structure. Currently, the main HEOs include single-phase, multi-component compounds with structures such as rock salt, spinel, fluorite, and perovskite. Each of these structures possesses unique properties, but the rapid and simple preparation of these compounds while ensuring a single crystalline phase remains a common challenge.

[0003] The main preparation methods for high-entropy oxides include solid-phase calcination, hydrothermal, sol-gel, and organic precursor methods. Among these methods, the solid-phase calcination method requires a long calcination time, resulting in large and uneven grain sizes; the hydrothermal method requires harsh reaction conditions of high temperature and high pressure, and a long reaction time; the sol-gel method has multiple steps, a long experimental process, and the resulting product has low crystallinity. Compared with the previous methods, the organic precursor method facilitates the formation of a high-entropy phase due to the uniform dispersion of metal ions in the precursor, enabling a uniform grain size distribution. The high-temperature decomposition of the organic ligand facilitates the formation of a porous structure, increasing the specific surface area and the usability of the high-entropy powder. Furthermore, the synthesis steps are simple, the experimental cycle is short, and the cost is low.

[0004] Metal-organic frameworks (MOFs) are prepared by self-assembly of metals / metal clusters with organic ligands. Due to their advantages such as higher surface area, porous structure, and designable composition, they are considered an important new type of porous material and are also known as a new precursor for the synthesis of high-entropy oxides. Patent CN115261921A discloses a method for preparing a FeCoNiMnCr high-entropy alloy / high-entropy oxide heterogeneous phase catalyst, comprising the following steps: dissolving 2,5-dihydroxyterephthalic acid, a ferrous salt, a cobalt salt, a nickel salt, a manganese salt, and a chromium salt in a predetermined molar ratio in a mixed solvent consisting of ethanol, deionized water, and N,N-dimethylformamide; after adding a carbon support, a hydrothermal reaction is carried out and heated at 100-140°C for 20-36 hours to obtain a FeCoNiMnCr five-membered metal-organic framework precursor; and further heat treatment in a reducing atmosphere is performed to obtain a FeCoNiMnCr high-entropy alloy / high-entropy oxide heterogeneous phase nanomaterial supported on carbon. However, this method uses a hydrothermal method that requires relatively harsh high-temperature and high-pressure reaction conditions, a long reaction time, and the product grain size is not clearly stated. Patent CN115710727A discloses a method for preparing a hollow framework high-entropy oxide, comprising the following steps: dropping an organic solution containing dimethylimidazole and acetylacetone metal organic compounds into an organic solution of zinc nitrate hexahydrate and stirring the mixture for 12-36 hours, centrifuging to obtain a high-entropy compound precipitate, and subjecting the precipitate to a carbonization reaction at 300-500°C for 3-5 hours to obtain a carbonized precursor, stirring the carbonized precursor with a ruthenium salt in an aqueous solution for 12-36 hours, centrifuging to obtain ZnFeNiCuCo-Ru, and then placing the precipitate in air at 800-1000°C for 2-4 hours for thermal decomposition to obtain a hollow framework high-entropy oxide. However, this method requires a large amount of toxic methanol as a solvent, a long stirring time, and requires two high-temperature calcinations, making the process complex and energy-intensive.

[0005] To improve the synthesis efficiency of the precursor and optimize the preparation process of high-entropy oxides, the present invention introduces five different nitrates as metal sources, uses dimethylimidazole as an organic ligand, and uses triethylamine as a crystallization modifier to promote the deprotonation process of dimethylimidazole. This significantly improves the nucleation and growth rates of the metal-organic framework material serving as a high-entropy oxide precursor, so that the synthesis conditions of the precursor can be quickly obtained by only stirring and aging at room temperature. The high-quality precursor ensures the successful acquisition of nanocrystalline (FeCoNiCrMn)3O4 porous high-entropy oxide after calcination. Summary of the Invention

[0006] The invention discloses a preparation method of nanocrystalline (FeCoNiCrMn)3O4 porous high-entropy oxide.

[0007] In order to achieve the above-mentioned object, the present invention comprises the following steps: (1) weighing 0.01 mol each of Fe(NO3)3·9H2O, Co(NO3)2·6H2O, Ni(NO3)2·6H2O, Cr(NO3)2·9H2O, and Mn(NO3)2·4H2O, dissolving them in 125 mL of deionized water and stirring them at room temperature for 10 min to form a solution A; weighing 0.2 mol of dimethylimidazole and dissolving it in a mixed solution of 500 mL of deionized water and 40-60 mL of triethylamine, stirring them for 10 min to form a solution B; while stirring, adding solution A dropwise to solution B at a rate of 2 mL / min; stirring continuously at room temperature for 1-4 h, aging for 1 h, centrifuging, washing with deionized water three times, and drying at 60°C for 8 h. (2) The dried precursor was ground through a 400-mesh sieve, heated to 800-1000°C at a rate of 5°C / min in an air atmosphere, kept at this temperature for 3 h, and then cooled to room temperature in the furnace to obtain nanocrystalline (FeCoNiCrMn)3O4 porous high-entropy oxide.

[0008] The control of various conditions in the synthesis process of the present invention, the order of addition of raw materials, concentrations and addition ratios thereof will greatly affect whether the final product can be successfully and quickly synthesized.

[0009] The present invention has the following advantages:

[0010] 1. Using triethylamine as a crystallization modifier can promote the deprotonation process of dimethylimidazole, increase the nucleation and growth rate of the metal-organic framework material used as a high-entropy oxide precursor, and effectively control the grain size. It can significantly improve the synthesis efficiency of the precursor while ensuring the uniform dispersion of metal ions in the metal-organic framework material. The obtained (FeCoNiCrMn)3O4 high-entropy oxide has a single structure and uniform composition.

[0011] 2. The high-entropy metal oxide obtained by the method provided by the present invention has a grain size between 100-200nm and a pore size between 20-50nm. It has a high specific surface area and has good application prospects in the fields of chemical catalysts, energy storage materials, coating materials, high-temperature structural materials, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is the XRD spectrum of the sample obtained in Example 1 of the present invention.

[0013] Figure 2 This is a SEM photograph of the sample obtained in Example 1 of the present invention. DETAILED DESCRIPTION

[0014] To better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific examples. It is particularly noted that the examples of the present invention are only used to illustrate the technical effects of the present invention and are not intended to limit the scope of protection of the present invention. The raw materials used in the examples can all be obtained by commercial purchase.

[0015] Example 1

[0016] The preparation method of (FeCoNiCrMn)3O4 in Example 1 includes the following specific steps:

[0017] Step 1. Weigh 0.01 mol of each of Fe(NO3)3·9H2O, Co(NO3)2·6H2O, Ni(NO3)2·6H2O, Cr(NO3)2·9H2O, and Mn(NO3)2·4H2O in equal molar proportions, dissolve them in 125 mL of deionized water, and stir for 10 min to form solution A.

[0018] Step 2: Weigh 0.2 mol of dimethylimidazole and dissolve it in a mixed solution of 500 mL of deionized water and 50 mL of triethylamine, and stir for 10 minutes to form solution B.

[0019] Step 3: Add solution A dropwise to solution B at a rate of 2 mL / min under stirring; stir continuously at room temperature for 1 h, age for 1 h, centrifuge, wash 3 times with deionized water, and dry at 60°C for 8 h.

[0020] Step 4: Grind the dried precursor through a 400-mesh sieve, heat it to 1000°C at a rate of 5°C / min in an air atmosphere, keep it warm for 3 hours, and cool it to room temperature in the furnace to obtain nanocrystalline (FeCoNiCrMn)3O4 porous high-entropy oxide.

[0021] The (FeCoNiCrMn)3O4 synthesized in the preferred embodiment 1 was subjected to X-ray diffraction analysis. Figure 1 This is the XRD spectrum of (FeCoNiCrMn)3O4, from which it can be seen that the characteristic diffraction peaks of (FeCoNiCrMn)3O4 synthesized by the present invention are highly consistent with those of Fe3O4 (JCPDS: PDF#75-0449), and the high peak intensity and narrow peak width indicate that the material has good crystallinity, obvious characteristic peaks, and no obvious impurity peaks are generated, indicating that (FeCoNiCrMn)3O4 was successfully synthesized rapidly at low temperature.

[0022] The morphology of (FeCoNiCrMn)3O4 synthesized in the preferred embodiment 1 was observed using a scanning electron microscope. Figure 2 This is a SEM photo of (FeCoNiCrMn)3O4. The material grains are 100nm-200nm, and there are 20-50nm mesopores between the grains.

[0023] Example 2

[0024] This embodiment is compared with Example 1, except that the content of triethylamine in step 2 is changed to 40 mL, and the rest are the same.

[0025] Example 3

[0026] This embodiment is compared with Example 1, except that the content of triethylamine in step 2 is changed to 60 mL, and the rest are the same.

[0027] Example 4

[0028] Compared with Example 1, this example is the same as Example 1 except that the room temperature stirring in step 3 is changed to 2 hours and the aging time is changed to 1 hour.

[0029] Example 5

[0030] Compared with Example 1, this example is the same as Example 1, except that the room temperature stirring in step 3 is changed to 3 hours and the aging time is changed to 1 hour.

[0031] Example 6

[0032] Compared with Example 1, this example is the same as Example 1 except that the room temperature stirring in step 3 is changed to 4 hours and the aging time is changed to 1 hour.

[0033] Example 7

[0034] Compared with Example 1, this embodiment is the same as Example 1 except that the holding temperature of the muffle furnace in step 4 is changed to 900° C.

[0035] Example 8

[0036] Compared with Example 1, this embodiment is the same as Example 1 except that the holding temperature of the muffle furnace in step 4 is changed to 800° C.

Claims

1. A method for preparing nanocrystalline (FeCoNiCrMn)3O4 porous high entropy oxide, characterized by: Using dimethylimidazole as an organic ligand, triethylamine as a precursor crystallization regulator, and nitrates of Fe, Co, Ni, Cr, and Mn elements as metal ion sources, the precursor is first obtained by stirring at room temperature and aging. The precursor is then washed, dried, and calcined to obtain nanocrystalline (FeCoNiCrMn)3O4 porous high-entropy oxide. The specific preparation steps are as follows: (1) Weigh 0.01 mol each of Fe(NO3)3·9H2O, Co(NO3)2·6H2O, Ni(NO3)2·6H2O, Cr(NO3)2·9H2O, and Mn(NO3)2·4H2O and dissolve them in 125 mL of deionized water. Stir at room temperature for 10 min to form solution A. Weigh 0.2 mol of dimethylimidazole and dissolve it in a mixed solution of 500 mL of deionized water and 40-60 mL of triethylamine. Stir for 10 min to form solution B. While stirring, add solution A dropwise to solution B at a rate of 2 mL / min. Stir continuously at room temperature for 1-4 h. After aging for 1 h, separate the solid and liquid. Wash the solid product with deionized water three times and dry it at 60 °C for 8 h. (2) The dried precursor was ground through a 400-mesh sieve, and the sieve residue was placed in a crucible. The temperature was raised to 800-1000 °C at a rate of 5 °C / min in an air atmosphere of a muffle furnace, kept at this temperature for 3 h, and then cooled to room temperature with the furnace to obtain nanocrystalline (FeCoNiCrMn)3O4 porous high-entropy oxide.

2. The method for preparing a nanocrystalline (FeCoNiCrMn)3O4 porous high entropy oxide according to claim 1, characterized in that: The nanocrystalline (FeCoNiCrMn) 3 O 4 porous high entropy oxide has a grain size of 100-200 nm and a pore size of 20-50 nm.

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