Molecular sieve loaded high-entropy alloy nanoparticle material and preparation method thereof

Abstract

The invention discloses a molecular sieve loaded high-entropy alloy nanoparticle material and a preparation method thereof, and belongs to the technical field of nano materials. The preparation method comprises the following steps: adding a metal salt precursor into a mixed polyol solution of polyvinylpyrrolidone and L-ascorbic acid for reaction; then acetone is added, and the high-entropy alloy nano-particles are prepared; then uniformly mixing with a solvent and an alkaline solution, adding tetraethyl orthosilicate, and stirring to prepare high-entropy alloy-coated silicon dioxide powder; and finally, mixing and grinding with tetrapropylammonium hydroxide, adding water, standing, crystallizing, centrifuging and calcining a solid product, thereby obtaining the product. The preparation method comprises the following steps: by taking metal salt as a raw material and polyvinylpyrrolidone as a protective agent, preparing high-entropy alloy nanoparticles by utilizing a polyhydric alcohol reduction method, then preparing high-entropy alloy silicon dioxide by utilizing a Stober method, and finally preparing the high-entropy alloy silicon dioxide through hydrothermal synthesis. The molecular sieve nanoparticles prepared by the method are small in size, large in specific surface area, high in catalytic activity and good in dispersity.

Description

Technical Field

[0001] The present invention relates to the technical field of nanomaterials, and in particular to a molecular sieve-loaded high-entropy alloy nanoparticle material and a preparation method thereof. Background Art

[0002] High entropy alloy is a new type of alloy material composed of five or more elements. The characteristics of multiple elements provide a broad space for material discovery and performance optimization. Although the concept of high entropy alloy has been proposed for a long time, the research on high entropy alloy nanoparticle materials has only recently begun to rise. The biggest challenge in preparing high entropy alloy nanoparticles is the need to integrate multiple elements into a single nanoparticle. Due to the differences in size and properties between different elements, alloy materials are prone to phase separation, resulting in a heterogeneous structure of the material. So far, many synthetic methods have been proposed in academia to prepare high entropy alloy nanoparticles with a single-phase solid solution structure. Including carbon thermal shock method, gas phase spark discharge, rapid radiation heating, chemical synthesis, low-temperature electrochemical reconstruction, sputtering, transient electrosynthesis, plasma heating, microwave heating, laser heating, organic ligand crosslinking and liquid metal fusion and other methods. However, due to the great differences in the physicochemical properties between different constituent elements, how to develop a synthesis method for high entropy alloy nanoparticles that can be applied to all metal elements and obtain ideal structures and properties is full of challenges.

[0003] In order to effectively utilize high-entropy alloy nanoparticles, the nanoparticles need to be loaded on a solid carrier. However, size reduction will cause a surge in the surface energy of the metal, which in turn makes the nanoparticles loaded on an open carrier thermodynamically unstable. Especially when the temperature exceeds the Tamman temperature, the nanoparticles are prone to leaching, sintering, and poisoning, causing the nanoparticles to lose their original structure and properties. In response to these problems, researchers began to try to confine the nanoparticles in the pores or cavities of the solid carrier and fix the nanoparticles through the spatial confinement effect.

[0004] Molecular sieve is a kind of 4 (where T refers to Si, Al or P) An inorganic nanoporous crystalline material composed of tetrahedrons. These tetrahedral structures are interconnected by sharing vertex oxygen atoms to form unique three-dimensional pore structures such as rings, cages, and channels. Its notable features include high specific surface area, uniform and ordered microporous channels, and adjustable acidity and alkalinity. The ordered and adjustable microporous channels give molecular sieves unique selectivity: they can selectively allow specific molecules to enter or leave the channels according to the size, shape and polarity of the molecules. A large number of studies have shown that when molecular sieves are used as carriers of nanoparticles, they can effectively confine nanoparticles in channels or cavities, so molecular sieves have shown extraordinary effects in anchoring nanoparticles.

[0005] The type, size and structure of metal elements in molecular sieves can be adjusted through different synthesis strategies. At present, researchers have developed a variety of synthesis strategies, covering various in-situ synthesis and post-processing synthesis methods. However, the above methods involve the use of a large amount of solvents, which can easily lead to the dissolution of high-entropy alloy nanoparticles and phase segregation, thereby changing the original structure and properties of high-entropy alloy nanoparticles. Summary of the invention

[0006] In order to solve the above technical problems, the purpose of the present invention is to provide a molecular sieve loaded high entropy alloy nanoparticle material and a preparation method thereof, so as to solve the problems of easy phase segregation, poor dispersion effect, easy agglomeration, etc. in the preparation of existing molecular sieve loaded high entropy alloy nanoparticle materials.

[0007] The technical solution of the present invention to solve the above technical problems is as follows:

[0008] A method for preparing a molecular sieve-loaded high-entropy alloy nanoparticle material comprises the following steps:

[0009] (1) adding a metal salt precursor solution to a mixed polyol solution of polyvinyl pyrrolidone and L-ascorbic acid to react to obtain a high entropy alloy nanoparticle dispersion;

[0010] (2) adding acetone to the dispersion obtained in step (1), centrifuging, and obtaining high entropy alloy nanoparticles;

[0011] (3) uniformly mixing the high entropy alloy nanoparticles obtained in step (2) with a solvent and an alkaline solution, adding tetraethyl orthosilicate, stirring, and drying to obtain a high entropy alloy@silicon dioxide powder;

[0012] (4) The high entropy alloy@silicon dioxide powder obtained in step (3) is first mixed with tetrapropylammonium hydroxide, ground, heated and dried, and then ultrapure water is added, allowed to stand for crystallization, and finally centrifuged and the solid product is calcined to obtain a high entropy alloy@MFI zeolite molecular sieve.

[0013] Furthermore, in step (1), the metal salt is at least five of palladium inorganic salt, platinum inorganic salt, rhodium inorganic salt, ruthenium inorganic salt, iridium inorganic salt, gold inorganic salt, copper inorganic salt, iron inorganic salt, cobalt inorganic salt and nickel inorganic salt; the concentration of each metal salt in the metal salt precursor solution is 0.01-0.015 mmol / mL, and the solvent is ethylene glycol.

[0014] Furthermore, the palladium inorganic salt is PdCl 2 , PdCl 4 、Na 2 PdCl 4 、Na 2 PdCl 6 , K 2 PdCl4 and K 2 PdCl 6 Any of the following:

[0015] Platinum inorganic salt is PtCl 2 , PtCl 4 、Na 2 PtCl 6 、Na 2 PtCl 6 6H 2 O、Na 2 PtCl 4 ·xH 2 O.K 2 PtCl 4 and K 2 PtCl 6 Any of the following;

[0016] Rhodium inorganic salt is RhCl 3 , RhCl 3 ·3H 2 O、RhCl 3 ·xH 2 O and K 3 RhCl 6 Any of the following;

[0017] Ruthenium inorganic salt is RuCl 3 、RuCl 3 ·3H 2 O、RuCl 3 ·xH 2 O.K 2 RuCl 6 and K 3 RuCl 6 One of;

[0018] Iridium inorganic salt is IrCl 3 、IrCl 4 、IrCl 3 ·3H 2 O、IrCl 3 ·xH 2 O、IrCl 4 ·xH 2 O、Na 2 IrCl 6 6H 2 O、Na 3 IrCl 6 ·xH 2 O, H 2 IrCl 6 ·xH 2 O and K 3IrCl 6 Any of the following;

[0019] Gold inorganic salts are AuCl, NaAuCl 4 ·2H 2 O and HAuCl 4 ·3H 2 Any one of O;

[0020] Copper inorganic salts are CuCl, CuCl 2 , CuCl 2 ·H 2 O and CuCl 2 ·2H 2 Any one of O;

[0021] Iron inorganic salt is FeCl 2 、FeCl 3 、FeCl 2 ·2H 2 O, FeCl 2 ·4H 2 O, FeCl 3 6H 2 O and FeCl 2 ·xH 2 Any one of O;

[0022] Cobalt inorganic salt is CoCl 2 、CoCl 2 6H 2 O and CoCl 2 ·xH 2 Any one of O;

[0023] Nickel inorganic salt is NiCl 2 、NiCl 2 6H 2 O and NiCl 2 ·xH 2 Any one of O.

[0024] Furthermore, in step (1), the molecular weight of polyvinyl pyrrolidone is 2500-58000; the concentration of polyvinyl pyrrolidone in the mixed polyol solution of polyvinyl pyrrolidone and L-ascorbic acid is 0.001-0.4 g / mL, the concentration of L-ascorbic acid is 0.001-0.01 g / mL, and the solvent is ethylene glycol.

[0025] Further, the structural formula of L-ascorbic acid is:

[0026] Furthermore, in step (1), the metal salt precursor solution is added to the reaction solution by dropwise injection at an injection rate of 0.005-3 mL / min. The reaction solution is preheated to 150-230° C. before addition. When all the metal salt precursor solution is dropwise injected into the reaction solution, the reaction is stopped.

[0027] The beneficial effects of adopting the above-mentioned further technical scheme are as follows: the present invention controls the reduction rate of different metals in the synthesis process by means of dripping and injection, thereby obtaining high-entropy alloy nanoparticles with uniform elemental composition and stability, and the size of the high-entropy alloy nanoparticles is between 5-20nm, which increases the specific surface area of ​​the high-entropy alloy nanoparticles and provides more metal active sites, which can more effectively exert the synergistic effect between the high-entropy alloy components and greatly enhance the catalytic performance.

[0028] Furthermore, in step (2), the volume ratio of the dispersion to acetone is 1:5-1:10; the centrifugal speed is 8000-12000 rpm, and the time is 30-60 min.

[0029] Furthermore, in step (3), the mass volume ratio of tetraethyl orthosilicate, solvent and alkaline solution is 3-4g:50-100mL:5-7mL, the solvent is ethanol, and the alkaline solution is aqueous ammonia; the stirring time is 6-12h; the drying temperature is 80-100°C, and the drying time is 5-24h.

[0030] Preferably, in step (3), the mass volume ratio of tetraethyl orthosilicate, solvent and alkaline solution is 3.4-3.5 g:80 mL:6 mL.

[0031] Further, the structural formula of tetraethyl orthosilicate is:

[0032] Furthermore, the mass ratio of tetrapropylammonium hydroxide in step (4) to tetraethyl orthosilicate in step (3) is 0.5-1:3-4; the mass volume ratio of tetrapropylammonium hydroxide to water is 0.5-1g:200-1600μL; the temperature of standing crystallization is 120-200°C, and the time is 1-5d; the speed of centrifugation is 8000-12000rpm, and the time is 30-60min; the calcination conditions are: in an air atmosphere, first heating to 500-600°C at a heating rate of 2-10°C / min, then keeping warm for 4-5h, and then cooling to room temperature.

[0033] The beneficial effect of adopting the above further technical solution is: the present invention controls the water content in the hydrothermal synthesis process to avoid the dissolution or agglomeration of high entropy alloy nanoparticles, while reducing the amount of solvent used to improve the safety of hydrothermal synthesis and reduce the generation of waste liquid.

[0034] Preferably, the mass ratio of tetrapropylammonium hydroxide in step (4) to tetraethyl orthosilicate in step (3) is 0.8-0.9:3.4-3.5; the mass volume ratio of tetrapropylammonium hydroxide to water is 0.8-0.9g:200-1600μL; and the calcination conditions are: in an air atmosphere, first heating to 550°C at a heating rate of 2-10°C / min, then keeping the temperature for 4-5h, and then cooling to room temperature.

[0035] Further, the structural formula of tetrapropylammonium hydroxide is:

[0036] A molecular sieve loaded high entropy alloy nanoparticle material is prepared by adopting the above preparation method.

[0037] The present invention has the following beneficial effects:

[0038] (1) The present invention uses a metal salt precursor as a raw material, polyvinyl pyrrolidone as a protective agent, L-ascorbic acid and ethylene glycol reducing agents as modifiers, and adopts a wet chemical method to prepare high entropy alloy nanoparticles. The obtained high entropy alloy nanoparticles are composed of more than five metal elements, and each metal element is evenly dispersed, and the molar percentage of each metal element in the alloy is 5%-35%.

[0039] (2) The present invention adopts the method of dripping and injection to control the reduction rate of different metals in the synthesis process, thereby obtaining high-entropy alloy nanoparticles with uniform elemental composition and stability, and the size of the high-entropy alloy nanoparticles is between 5-20nm, which increases the specific surface area of ​​the high-entropy alloy nanoparticles and provides more metal active sites, which can more effectively exert the synergistic effect between the high-entropy alloy components and greatly enhance the catalytic performance.

[0040] (3) The present invention adopts a solid precursor stabilization method to synthesize molecular sieves, and stabilizes high entropy alloy nanoparticles by silicon dioxide, so that after hydrothermal synthesis, the high entropy alloy nanoparticles can be uniformly confined in the molecular sieve and have ultra-high dispersion.

[0041] (4) The present invention controls the water content in the hydrothermal synthesis process to avoid dissolution or agglomeration of high entropy alloy nanoparticles, while reducing the amount of solvent used, which helps to improve the safety of hydrothermal synthesis and reduce the generation of waste liquid. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 is the HADDF-STEM image of the high entropy alloy nanoparticles in Example 1;

[0043] Figure 2 is a size distribution diagram of high entropy alloy nanoparticles in Example 1;

[0044] Figure 3is a composition statistical diagram of high entropy alloy nanoparticles in Example 1;

[0045] Figure 4 This is the HADDF-STEM image of the high entropy alloy@silicon dioxide in Example 1;

[0046] Figure 5 This is the HADDF-STEM of the high entropy alloy@MFI zeolite molecular sieve in Example 1;

[0047] Figure 6 This is the HADDF-STEM image of the high entropy alloy / MFI zeolite molecular sieve in Comparative Example 1. DETAILED DESCRIPTION

[0048] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples are only used to explain the present invention and are not used to limit the scope of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0049] Embodiment 1:

[0050] A method for preparing a molecular sieve-loaded high-entropy alloy nanoparticle material comprises the following steps:

[0051] (1) First, Na 2 PdCl 4 , K 2 PtCl 4 , RhCl 3 ·xH 2 O, H 2 IrCl 6 ·xH 2 O and RuCl 3 ·xH 2 O is added to 3 mL of ethylene glycol to prepare a metal salt precursor solution, wherein the concentration of each metal salt is 0.011 mmol / mL, and then 0.5 g of polyvinyl pyrrolidone and 0.05 g of L-ascorbic acid are added to 7 mL of ethylene glycol to prepare a reaction solution;

[0052] (2) slowly adding the metal salt precursor solution obtained in step (1) into the reaction solution preheated to 180° C. through a syringe pump at a dropping speed of 0.05 mL / min, and continuously stirring the reaction at 180° C. until all the metal salt precursor is added dropwise to the reaction solution, stopping the reaction, and obtaining a high entropy alloy nanoparticle dispersion;

[0053] (3) Add acetone to the high entropy alloy nanoparticle dispersion obtained in step (2) at a volume ratio of 1:5, then centrifuge at 8000 rpm for 30 min, remove the supernatant, and obtain high entropy alloy nanoparticles. Figure 1 HAADF-STEM image of the prepared high entropy alloy nanoparticles. As shown in the figure, the prepared high entropy alloy nanoparticles have a three-dimensional dendrite morphology. Figure 2 The size distribution diagram of high entropy alloy nanoparticles. The size of the prepared high entropy alloy nanoparticles is about 11nm. Figure 3 The composition (Pt, Pd, Ir, Ru, Rh) of high entropy alloy nanoparticles is statistically shown. The elements of the synthesized high entropy alloy nanoparticles are evenly distributed, and the atomic percentage of all elements is about 20%;

[0054] (4) The high entropy alloy nanoparticles obtained in step (3) were uniformly mixed with 80 mL of ethanol and 6 mL of aqueous ammonia, 3.47 g of tetraethyl orthosilicate was added, and the mixture was stirred at room temperature for 8 h, and then rotary evaporated at 60 ° C to remove the solvent, and vacuum dried at 100 ° C overnight to obtain high entropy alloy @silicon dioxide powder. Figure 4 This is the HADDF-STEM image of high entropy alloy@silica. The high entropy alloy nanoparticles are wrapped by silica to form high entropy alloy@silica microspheres, which are about 80nm in size;

[0055] (5) The high entropy alloy @silica powder was mixed with 0.83 g of tetrapropylammonium hydroxide, ground, heated and dried to remove moisture, and the mixture was transferred to a high-pressure reactor. 400 μL of ultrapure water was added to the reactor, and the mixture was placed in an oven at 180°C for 3 days to crystallize. The mixture was then centrifuged at 10,000 rpm for 30 min, the supernatant was removed, and the product was repeatedly washed 3 times with ultrapure water, dried and ground. The molecular sieve powder loaded with high entropy alloy nanoparticles was placed in an air atmosphere, first heated to 550°C at a heating rate of 5°C / min, maintained for 4 hours, and then cooled to room temperature to obtain the high entropy alloy @MFI zeolite molecular sieve powder. Figure 5 This is the HADDF-STEM image of high entropy alloy@MFI. The white bright spots in the image are high entropy alloy nanoparticles. It can be seen from the image that the particles are evenly distributed.

[0056] Embodiment 2:

[0057] A method for preparing a molecular sieve-loaded high-entropy alloy nanoparticle material comprises the following steps:

[0058] (1) First, PdCl 4 , PtCl 4 , RhCl 3 、IrCl 4 and RuCl 3Add to 5 mL of ethylene glycol to prepare a metal salt precursor solution, wherein the concentration of each metal salt is 0.011 mmol / mL, and then add 2 g of polyvinyl pyrrolidone and 0.1 g of L-ascorbic acid to 9 mL of ethylene glycol to prepare a reaction solution;

[0059] (2) slowly adding the metal salt precursor solution obtained in step (1) into the preheated reaction solution at a drop rate of 3 mL / min through a syringe pump, and continuously stirring the reaction at 230° C. until all the metal salt precursor is added dropwise into the reaction solution, stopping the reaction, and obtaining a high entropy alloy nanoparticle dispersion;

[0060] (3) adding acetone to the high entropy alloy nanoparticle dispersion obtained in step (2) at a volume ratio of 1:10, then centrifuging at a centrifugal speed of 12000 rpm for 60 min, removing the supernatant, and obtaining high entropy alloy nanoparticles;

[0061] (4) 80 mL of ethanol and 6 mL of ammonia water were mixed evenly to obtain the high entropy alloy nanoparticles obtained in step (3), 3.5 g of tetraethyl orthosilicate was added, and the mixture was stirred at room temperature for 12 h, and then the mixture was rotary evaporated at 80 ° C to remove the solvent, and vacuum dried at 100 ° C overnight to obtain high entropy alloy@silicon dioxide powder;

[0062] (5) The high entropy alloy @silicon dioxide powder obtained in step (4) is mixed with 0.9 g of tetrapropylammonium hydroxide, ground, heated and dried to remove moisture, and the mixture is transferred to a high-pressure reactor, and 1600 μL of ultrapure water is added to the reactor. The mixture is placed in an oven at 120°C for 5 days to crystallize, and then centrifuged at a centrifugal speed of 12000 rpm for 60 min, the supernatant is removed, and the product is repeatedly washed 3 times with ultrapure water, dried and ground, and the molecular sieve powder loaded with high entropy alloy nanoparticles is placed in an air atmosphere, first heated to 550°C at a heating rate of 10°C / min, and then maintained for 4 hours, and then cooled to room temperature, and the high entropy alloy @MFI zeolite molecular sieve powder is collected.

[0063] Embodiment 3:

[0064] A method for preparing a molecular sieve-loaded high-entropy alloy nanoparticle material comprises the following steps:

[0065] (1) First, AuCl 4 , CuCl 4 、FeCl 3 、CoCl 2 and NiCl 2 Add to 1 mL of ethylene glycol to prepare a metal salt precursor solution, wherein the concentration of each metal salt is 0.011 mmol / mL, then add 0.01 g of polyvinyl pyrrolidone and 0.01 g of L-ascorbic acid to 5 mL of ethylene glycol to prepare a reaction solution;

[0066] (2) slowly adding the metal salt precursor solution obtained in step (1) into the preheated reaction solution through a syringe pump at a drop rate of 0.005 mL / min, and continuously stirring the reaction at 150° C. until all the metal salt precursor is added dropwise into the reaction solution, stopping the reaction, and obtaining a high entropy alloy nanoparticle dispersion;

[0067] (3) adding acetone to the high entropy alloy nanoparticle dispersion obtained in step (2) at a volume ratio of 1:5, then centrifuging at a centrifugal speed of 8000 rpm for 30 minutes, removing the supernatant, and obtaining high entropy alloy nanoparticles;

[0068] (4) The high entropy alloy nanoparticles obtained in step (3) were uniformly mixed with 80 mL of ethanol and 6 mL of ammonia water, 3.4 g of tetraethyl orthosilicate was added, and the mixture was stirred at room temperature for 6 h, and then rotary evaporated at 60 ° C to remove the solvent, and vacuum dried at 80 ° C overnight to obtain high entropy alloy @ silicon dioxide powder;

[0069] (5) The high entropy alloy @silicon dioxide powder obtained in step (4) is mixed with 0.8 g of tetrapropylammonium hydroxide, ground, heated and dried to remove moisture, and the mixture is transferred to a high-pressure reactor, and 200 μL of ultrapure water is added to the reactor. The mixture is placed in a 200°C oven and allowed to stand for 1 day for crystallization, and then centrifuged at 8000 rpm for 30 min. The supernatant is removed, and the product is repeatedly washed 3 times with ultrapure water, dried and ground. The molecular sieve powder loaded with high entropy alloy nanoparticles is placed in an air atmosphere, first heated to 550°C at a heating rate of 2°C / min, then maintained for 4 hours, and then cooled to room temperature to obtain a high entropy alloy @MFI zeolite molecular sieve powder.

[0070] Embodiment 4:

[0071] A method for preparing a molecular sieve-loaded high-entropy alloy nanoparticle material comprises the following steps:

[0072] (1) First, Na 2 PdCl 4 , K 2 PtCl 4 、Na 2 AuCl 4 ·2H 2 O, CuCl 2 ·2H 2 O and NiCl 2 ·xH 2O is added to 3 mL of ethylene glycol to prepare a metal salt precursor solution, wherein the concentration of each metal salt is 0.011 mmol / mL, and then 0.05 g of polyvinyl pyrrolidone and 0.05 g of L-ascorbic acid are added to 7 mL of ethylene glycol to prepare a reaction solution;

[0073] (2) slowly adding the metal salt precursor solution obtained in step (1) into the preheated reaction solution through a syringe pump at a dropping speed of 0.5 mL / min, and continuously stirring the reaction at 180° C. until all the metal salt precursor is added dropwise into the reaction solution, stopping the reaction, and obtaining a high entropy alloy nanoparticle dispersion;

[0074] (3) adding acetone in a volume ratio of 1:5 to the high entropy alloy nanoparticle dispersion obtained in step (2), then centrifuging at a centrifugal speed of 8000 rpm for 30 min, removing the supernatant, and obtaining high entropy alloy nanoparticles;

[0075] (4) The high entropy alloy nanoparticles obtained in step (3) were uniformly mixed with 80 mL of ethanol and 6 mL of ammonia water, 3.4 g of tetraethyl orthosilicate was added, and the mixture was stirred at room temperature for 8 h, and then rotary evaporated at 60 ° C to remove the solvent, and vacuum dried at 100 ° C overnight to obtain high entropy alloy @ silicon dioxide powder;

[0076] (5) The high entropy alloy @silicon dioxide powder obtained in step (4) is mixed with 0.83 g of tetrapropylammonium hydroxide, ground, heated and dried to remove moisture, and the mixture is transferred to a high-pressure reactor, and 400 μL of ultrapure water is added to the reactor. The mixture is placed in an oven at 180°C for 3 days to crystallize, and then centrifuged at a centrifugal speed of 10,000 rpm for 30 minutes. The supernatant is removed, and the product is repeatedly washed 3 times with ultrapure water, dried and ground. The molecular sieve powder loaded with high entropy alloy nanoparticles is placed in an air atmosphere, first heated to 550°C at a heating rate of 5°C / min, maintained for 4 hours, and then cooled to room temperature to obtain a high entropy alloy @MFI zeolite molecular sieve powder.

[0077] Embodiment 5:

[0078] A method for preparing a molecular sieve-loaded high-entropy alloy nanoparticle material comprises the following steps:

[0079] (1) First, Na 2 PdCl 4 , K 2 PtCl 4 , RhCl 3 ·xH 2 O、HAuCl 4 ·3H 2 O, H 2 IrCl 6 ·xH2 O、RuCl 3 ·xH 2 O, CuCl 2 ·2H 2 O、NiCl 2 6H 2 O, FeCl 2 ·xH 2 O and CoCl 2 ·xH 2 O is added to 3 mL of ethylene glycol to prepare a metal salt precursor solution, wherein the concentration of each metal salt is 0.011 mmol / mL, and then 0.05 g of polyvinyl pyrrolidone and 0.05 g of L-ascorbic acid are added to 7 mL of ethylene glycol to prepare a reaction solution;

[0080] (2) slowly adding the metal salt precursor solution obtained in step (1) into the preheated reaction solution through a syringe pump at a dropping speed of 0.05 mL / min, and continuously stirring the reaction at 200° C. until all the metal salt precursor is added dropwise into the reaction solution, stopping the reaction, and obtaining a high entropy alloy nanoparticle dispersion;

[0081] (3) adding acetone to the high entropy alloy nanoparticle dispersion obtained in step (2) at a volume ratio of 1:6, then centrifuging at a centrifugal speed of 8000 rpm for 30 minutes, removing the supernatant, and obtaining high entropy alloy nanoparticles;

[0082] (4) The high entropy alloy nanoparticles obtained in step (3) were uniformly mixed with 80 mL of ethanol and 6 mL of ammonia water, 3.47 g of tetraethyl orthosilicate was added, and the mixture was stirred at room temperature for 7 h, and then rotary evaporated at 80 ° C to remove the solvent, and vacuum dried at 100 ° C overnight to obtain high entropy alloy @ silicon dioxide powder;

[0083] (5) The high entropy alloy @silicon dioxide powder obtained in step (4) is mixed with 0.8 g of tetrapropylammonium hydroxide, ground, heated and dried to remove moisture, and the mixture is transferred to a high-pressure reactor, and 1600 μL of ultrapure water is added to the reactor. The mixture is placed in an oven at 200°C for 5 days to crystallize, and then centrifuged at a centrifugal speed of 8000 rpm for 30 minutes. The supernatant is removed, and the product is repeatedly washed 3 times with ultrapure water, dried and ground. The molecular sieve powder loaded with high entropy alloy nanoparticles is placed in an air atmosphere, first heated to 550°C at a heating rate of 5°C / min, and then maintained for 4 hours, and then cooled to room temperature to collect and obtain high entropy alloy @MFI zeolite molecular sieve powder.

[0084] Comparative Example 1:

[0085] A method for preparing a molecular sieve-loaded high-entropy alloy nanoparticle material comprises the following steps:

[0086] (1) First, Na 2 PdCl 4 , K 2 PtCl 4 , RhCl 3 ·xH 2 O, H 2 IrCl 6 ·xH 2 O and RuCl 3 ·xH 2 O is added to 3 mL of ethylene glycol to prepare a metal salt precursor solution, wherein the concentration of each metal salt is 0.011 mmol / mL, and then 0.5 g of polyvinyl pyrrolidone and 0.05 g of L-ascorbic acid are added to 7 mL of ethylene glycol to prepare a reaction solution;

[0087] (2) slowly adding the metal salt precursor solution obtained in step (1) into the preheated reaction solution through a syringe pump at a dropping speed of 0.05 mL / min, and continuously stirring the reaction at 180° C. until all the metal salt precursor is added dropwise into the reaction solution, stopping the reaction, and obtaining a high entropy alloy nanoparticle dispersion;

[0088] (3) adding acetone to the high entropy alloy nanoparticle dispersion obtained in step (2) at a volume ratio of 1:5, then centrifuging at a centrifugal speed of 8000 rpm for 30 minutes, removing the supernatant, and obtaining high entropy alloy nanoparticles;

[0089] (4) 80 mL of ethanol and 6 mL of ammonia water were mixed evenly, 3.47 g of tetraethyl orthosilicate was added, and the mixture was stirred at room temperature for 8 h, and then the solvent was removed by rotary evaporation at 60 ° C., and the mixture was vacuum dried at 100 ° C. overnight to obtain silicon dioxide powder;

[0090] (5) The silica powder is mixed with the high entropy alloy nanoparticles obtained in step (3) and 0.83 g of tetrapropylammonium hydroxide, ground, heated and dried to remove moisture, and the mixture is transferred to a high-pressure reactor, and 400 μL of ultrapure water is added to the reactor, and the mixture is placed in an oven at 180°C for 3 days to crystallize, and then centrifuged at a centrifugal speed of 10,000 rpm for 30 minutes, the supernatant is removed, and the product is repeatedly washed 3 times with ultrapure water, dried and ground, and the molecular sieve powder loaded with metal nanoparticles is placed in an air atmosphere, first heated to 550°C at a heating rate of 5°C / min and maintained for 4 hours, and then cooled to room temperature, and the high entropy alloy / MFI zeolite molecular sieve powder is collected. Figure 6 This is the HADDF-STEM image of high entropy alloy / MFI. The white bright spots in the image are high entropy alloy nanoparticles. As can be seen from the figure, the particles are unevenly distributed, severely agglomerated, and distributed outside the MFI zeolite molecular sieve.

[0091] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a molecular sieve-loaded high entropy alloy nanoparticle material, characterized in that: The following steps are involved: (1) adding a metal salt precursor solution to a mixed polyol solution of polyvinyl pyrrolidone and L-ascorbic acid to react to obtain a high entropy alloy nanoparticle dispersion; (2) adding acetone to the dispersion obtained in step (1), centrifuging, and obtaining high entropy alloy nanoparticles; (3) uniformly mixing the high entropy alloy nanoparticles obtained in step (2) with a solvent and an alkaline solution, adding tetraethyl orthosilicate, stirring, and drying to obtain a high entropy alloy@silicon dioxide powder; (4) The high entropy alloy@silicon dioxide powder obtained in step (3) is first mixed with tetrapropylammonium hydroxide, ground, heated and dried, and then ultrapure water is added, allowed to stand for crystallization, and finally centrifuged and the solid product is calcined to obtain.

2. The method for preparing the molecular sieve-loaded high entropy alloy nanoparticle material according to claim 1, characterized in that: In the step (1), the metal salt is at least five of palladium inorganic salt, platinum inorganic salt, rhodium inorganic salt, ruthenium inorganic salt, iridium inorganic salt, gold inorganic salt, copper inorganic salt, iron inorganic salt, cobalt inorganic salt and nickel inorganic salt; the concentration of each metal salt in the metal salt precursor solution is 0.01-0.015 mmol / mL, and the solvent is ethylene glycol.

3. The method for preparing the molecular sieve-loaded high-entropy alloy nanoparticle material according to claim 2, characterized in that: The palladium inorganic salt is any one of PdCl2, PdCl4, Na2PdCl4, Na2PdCl6, K2PdCl4 and K2PdCl6; The platinum inorganic salt is any one of PtCl2, PtCl4, Na2PtCl6, Na2PtCl6·6H2O, Na2PtCl4·xH2O, K2PtCl4 and K2PtCl6; The rhodium inorganic salt is any one of RhCl3, RhCl3·3H2O, RhCl3·xH2O and K3RhCl6; The ruthenium inorganic salt is one of RuCl3, RuCl3·3H2O, RuCl3·xH2O, K2RuCl6 and K3RuCl6; The iridium inorganic salt is any one of IrCl3, IrCl4, IrCl3·3H2O, IrCl3·xH2O, IrCl4·xH2O, Na2IrCl6·6H2O, Na3IrCl6·xH2O, H2IrCl6·xH2O and K3IrCl6; The gold inorganic salt is any one of AuCl, NaAuCl4·2H2O and HAuCl4·3H2O; The copper inorganic salt is any one of CuCl, CuCl2, CuCl2·H2O and CuCl2·2H2O; The inorganic iron salt is any one of FeCl2, FeCl3, FeCl2·2H2O, FeCl2·4H2O, FeCl3·6H2O and FeCl2·xH2O; The cobalt inorganic salt is any one of CoCl2, CoCl2·6H2O and CoCl2·xH2O; The nickel inorganic salt is any one of NiCl2, NiCl2·6H2O and NiCl2·xH2O.

4. The method for preparing the molecular sieve-loaded high-entropy alloy nanoparticle material according to claim 1, characterized in that: The molecular weight of polyvinyl pyrrolidone in step (1) is 2500-58000; the concentration of polyvinyl pyrrolidone in the mixed polyol solution of polyvinyl pyrrolidone and L-ascorbic acid is 0.001-0.4 g / mL, the concentration of L-ascorbic acid is 0.001-0.01 g / mL, and the solvent is ethylene glycol.

5. The method for preparing the molecular sieve-loaded high-entropy alloy nanoparticle material according to claim 1, characterized in that: In the step (1), the metal salt precursor solution is added to the reaction solution by dropwise injection at an injection rate of 0.005-3 mL / min. The reaction solution is preheated to 150-230° C. before addition. When all the metal salt precursor solution is dropwise injected into the reaction solution, the reaction is stopped.

6. The method for preparing the molecular sieve-loaded high-entropy alloy nanoparticle material according to claim 1, characterized in that: In the step (2), the volume ratio of the dispersion to acetone is 1 / 5-1 / 10; the centrifugal speed is 8000-12000 rpm, and the time is 30-60 min.

7. The method for preparing the molecular sieve-loaded high-entropy alloy nanoparticle material according to claim 1, characterized in that: In the step (3), the mass volume ratio of tetraethyl orthosilicate, solvent and alkaline solution is 3-4g:50-100mL:5-7mL, the solvent is ethanol, and the alkaline solution is ammonia water; the stirring time is 6-12h; the drying temperature is 80-100°C and the drying time is 5-24h.

8. The method for preparing molecular sieve-loaded high entropy alloy nanoparticle material according to claim 1, characterized in that: The mass ratio of tetrapropylammonium hydroxide in step (4) to tetraethyl orthosilicate in step (3) is 0.5-1:3-4; the mass volume ratio of tetrapropylammonium hydroxide to water is 0.5-1g:200-1600μL; the temperature of standing crystallization is 120-200°C, and the time is 1-5d; the speed of centrifugation is 8000-12000rpm, and the time is 30-60min; the calcination conditions are: in an air atmosphere, first heating to 500-600°C at a heating rate of 2-10°C / min, then keeping warm for 4-5h, and then cooling to room temperature.

9. A molecular sieve loaded high entropy alloy nanoparticle material, characterized in that: The method is prepared by the method according to any one of claims 1 to 8.

Images