A method for preparing high-entropy alloy nanocatalysts by high-temperature liquid phase impact

Abstract

The present invention relates to a method for preparing a high-entropy alloy nanocatalyst by high-temperature liquid-phase impact, comprising the following steps: Step 1: preparing a mixed solution precursor; weighing a metal salt and a carbon black carrier in proportion, and thoroughly mixing them with a surfactant solvent and an auxiliary reducing agent; stirring the mixed solution to obtain a uniformly dispersed mixed solution precursor; Step 2: transferring the mixed solution precursor to a container in a protective atmosphere, fixing it on a heated substrate, and subjecting it to high-temperature liquid-phase impact to obtain a crude high-entropy alloy nanoparticle product; Step 3: separating and washing the crude high-entropy alloy nanoparticle product to obtain a high-entropy alloy nanoparticle catalyst. This method for preparing high-entropy alloy nanoparticle catalytic materials has the following advantages: short preparation time, low energy consumption, easy control of material properties, wide applicability, small particle size, and uniform loading on carbon black. Furthermore, due to the unique liquid-phase direct heating process, it is easy to achieve large-scale industrial production of the catalyst material.

Description

Technical Field

[0001] The present invention relates to the preparation of high entropy alloy nanocatalysts, in particular to a method for preparing high entropy alloy nanocatalysts by high-temperature liquid phase impact. Background Art

[0002] In order to achieve the goals of "carbon peak" and "carbon neutrality" as soon as possible, developing high-energy-density, pollution-free, renewable hydrogen to replace traditional fossil energy is a feasible way. Among the many hydrogen production methods currently available, acidic water electrolysis technology has attracted widespread attention due to its high efficiency, high purity (up to 99.995%), and pollution-free characteristics. However, acidic water electrolysis technology requires efficient and stable catalysts to achieve high current density (>500 or 1000 mA cm -2 ) to improve the sluggish kinetics of water splitting (oxygen evolution reaction, OER, at the anode and hydrogen evolution reaction, HER, at the cathode). Although many non-precious metal catalysts have been developed for HER, these low-cost catalysts are not suitable for long-term, high-current-density acidic water electrolysis. While precious metal catalysts such as Pt and Ru have good HER activity and stability, their high cost limits their further application. Therefore, integrating multiple metal elements with excellent catalytic properties and developing advanced catalysts are of great significance for industrial production.

[0003] High-entropy alloys (HEAs) are solid solutions composed of five or more elements in near-molar ratios, with atomic proportions typically ranging from 5% to 35%. Due to their multi-principal component nature and the synergistic interactions between their components, HEAs exhibit properties distinct from those of single metals or binary alloys. These properties include a thermodynamically high entropy effect, a structural lattice distortion effect, a kinetically slow diffusion effect, and a "cocktail" effect in performance. These four effects contribute to their exceptional activity and stability in catalytic reactions. In particular, the multi-principal component nature of HEAs provides a wide variety of catalytic adsorption active sites, making them suitable for a variety of catalytic reactions, including HER, OER, oxygen reduction, methanol oxidation, CO2 reduction, CO oxidation, and nitrogen reduction. However, HEAs prepared by conventional methods, such as arc melting and vacuum induction casting, typically form large bulk structures with small surface areas and a limited number of active sites, significantly limiting their application in catalysis.

[0004] In order to solve the size problem, new rapid synthesis methods have been used to prepare high-entropy alloy nanostructures, such as carbon thermal reduction, microwave heating, rapid moving bed pyrolysis, etc. However, their size is still above 5nm; although high-entropy alloy catalysts below 5nm can be prepared by traditional liquid oil bath method, it is time-consuming and consumes a lot of energy. Summary of the Invention

[0005] The present invention discloses a method for preparing high-entropy alloy nanocatalysts by high-temperature liquid-phase impact. This method not only overcomes the limitation of new rapid synthesis methods in preparing high-entropy alloys with particle sizes below 5 nm, but also avoids the time-consuming disadvantage of traditional liquid-phase methods for preparing high-entropy alloys. The method uses ultrasound and magnetic stirring to prepare a metal salt / carbon black carrier mixed solution precursor. The precursor is then subjected to high-temperature liquid-phase impact in a protective atmosphere. After separation and washing, a high-entropy alloy nanoparticle catalyst material is finally prepared, uniformly supported on the carbon black surface.

[0006] A method for preparing a high-entropy alloy nanocatalyst by high-temperature liquid phase impact, comprising the following steps:

[0007] Step 1: Prepare mixed solution precursor

[0008] First, a carbon black carrier and at least five metal salts are weighed in proportion and mixed with a surfactant solvent and an auxiliary reducing agent. The mixture is then stirred to obtain a uniformly dispersed mixed solution precursor. Different metal salts are taken in equal molar ratios. The mass ratio of the single metal element in the metal salt to the carbon black carrier is 1 to 2:10.

[0009] Step 2: In a protective atmosphere, the mixed solution precursor obtained in step 1 is placed in a container, fixed on a heated substrate, and directly subjected to high-temperature liquid phase impact to obtain a crude product of high-entropy alloy nanoparticles;

[0010] Step 3: Separate and wash the crude high entropy alloy nanoparticle product obtained in step 2 to obtain a high entropy alloy nanoparticle catalyst.

[0011] Furthermore, the metal salts in step 1 belong to the same type of metal salts, specifically acetylacetonate metal salts, halide metal salts, nitrate metal salts, sulfate metal salts or acetate metal salts.

[0012] Furthermore, the acetylacetonate metal salts include: acetylacetonate platinum, acetylacetonate palladium, acetylacetonate rhodium, acetylacetonate cobalt, acetylacetonate nickel, acetylacetonate ruthenium, acetylacetonate iridium, acetylacetonate iron, acetylacetonate copper, acetylacetonate manganese, acetylacetonate zinc; the halide metal salts include: chloroplatinic acid and its derivatives, chloropalladic acid and its derivatives, rhodium chloride, cobalt chloride, ruthenium chloride, nickel chloride, copper chloride; the nitrate metal salts include: nickel nitrate, copper nitrate, cobalt nitrate, zinc nitrate, ferrous nitrate, manganese nitrate; the sulfate metal salts include: nickel sulfate, copper sulfate, cobalt sulfate, zinc sulfate, ferrous sulfate, manganese sulfate; the acetate metal salts include: nickel acetate, copper acetate, cobalt acetate, zinc acetate, ferrous acetate, manganese acetate. The metal salts of the present invention use five or more of the same salts, and some of them can also use different salts.

[0013] Furthermore, the carbon black carrier includes: Vulcan XC-72R, Vulcan XC-72, Vulcan P, BP2000, and ketjen black EC-600JD, which are treated by soaking in 0.2M nitric acid for 12 hours and then washed.

[0014] Furthermore, the surfactant solvent is one or more of oleylamine, oleic acid, and dodecane, and the total amount of the surfactant solvent is 5 to 20 mL; the auxiliary reducing agent is: 37 wt% formaldehyde solution, and the amount is 0.4 to 1.6 mL; the mass volume ratio of the carbon black carrier to the surfactant solvent and the auxiliary reducing agent is 1 mg:1 ml:0.08 ml.

[0015] Furthermore, the protective atmosphere is one or more of helium, neon, argon, krypton, xenon, and nitrogen.

[0016] Furthermore, the amount of the mixed solution precursor is 2-5 mL, which is transferred to a 10-20 mL container, which is an insulating crucible; the heating base is a carbon felt with a size of 5.5 cm × 4 cm × 1 cm; the high temperature liquid phase impact condition is: the current is 30-45 A, and the duration is 60-120 s. Under this condition, the heating rate is 10 3 K / min. After power failure, the temperature drops rapidly under natural conditions. Under normal circumstances, the cooling rate can reach 10 3 K / min.

[0017] Furthermore, the power-on current is 38A and the duration is 60s.

[0018] Furthermore, the separation method is centrifugation or filtration, the centrifugal speed is 8000-10000 rpm / min, and the centrifugal time is 3-5 min; 70mm medium-speed filter paper is used for filtration; and the washing solvent is a mixed solution of n-hexane and ethanol in a volume ratio of 1:1.

[0019] The high-entropy alloy nanoparticles prepared by the present invention can greatly inhibit the secondary agglomeration of the nanoparticles due to the short heating time, fast heating and cooling rates, and the presence of a special liquid phase environment, forming ultrasmall high-entropy alloy nanoparticles with an average particle size of approximately 3 nm and rich catalytic active sites and lattice defects.

[0020] The present invention has the characteristics of short heating time and fast heating and cooling rate, which are all achieved through Joule heating.

[0021] The liquid phase environment mainly composed of a surface active solvent involved in the present invention can play the role of selectively adsorbing organic ligands on the interface and regulating morphology.

[0022] The PtCoNiRuIr high entropy alloy nanoparticle catalyst uniformly loaded on carbon black prepared by the method of the present invention exhibits excellent catalytic activity and stability in hydrogen evolution reaction.

[0023] In 0.5M H2SO4 acidic medium, 10mA cm -2 and 1000mA cm -2 The overpotentials are 18mV and 408mV respectively, and the stability of the chronopotentiometry test is more than 30h and the stability of the cyclic voltammetry test is more than 10,000 cycles.

[0024] As described above, the types of high entropy alloy elements prepared by the method of the present invention include but are not limited to Pt, Co, Ni, Ru, and Ir, and the application scenarios include but are not limited to hydrogen evolution reaction.

[0025] The present invention has the following beneficial effects:

[0026] (1) Compared with other novel methods for rapidly preparing high-entropy alloys, the high-entropy alloy nanoparticles prepared by the present invention have a smaller particle size of approximately 3 nm, and are not agglomerated on the carrier and are uniformly loaded;

[0027] (2) Compared with the traditional liquid phase method for preparing high entropy alloys, the time is greatly improved, which can be shortened from hours to minutes;

[0028] (3) In addition, due to the special liquid phase direct heating process, it is easy to achieve large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic diagram of the mechanism of a method for preparing high-entropy alloy nanocatalysts by ultrafast high-temperature liquid phase impact of the present invention;

[0030] Figure 2 (a) is a low-magnification transmission electron microscope image of the PtCoNiRuIr high entropy alloy nanocatalyst supported on carbon black of the present invention, Figure 2 (b) is a statistical diagram of the particle size distribution of PtCoNiRuIr high entropy alloy nanoparticle catalyst supported on carbon black;

[0031] Figure 3 The high entropy alloy nanocatalyst of the present invention is compared with other methods in terms of particle size, synthesis time dimension, etc. (HTLS: high temperature liquid phase impact method; CTS: carbon thermal shock method; LPI: laser pulse radiation method; MH: microwave heating method; OPOPS: one-pot oil phase synthesis method; CVD FH: chemical vapor deposition furnace heating method);

[0032] Figure 4(a) is a high-resolution transmission electron microscopy image of PtCoNiRuIr high-entropy alloy nanocatalyst (a). Figure 4 (b) is a partial magnified image of the PtCoNiRuIr high entropy alloy nanocatalyst with the lattice spacing marked;

[0033] Figure 5 (a) Stress-strain analysis of the PtCoNiRuIr high-entropy alloy nanocatalyst on the (111) crystal plane. Compressive strain is represented by green to dark blue, and tensile strain is represented by red to bright yellow. Figure 5 (b) Yes Figure 4 (a) Corresponding fast Fourier transform image;

[0034] Figure 6 This is the energy spectrum distribution diagram of each element in the PtCoNiRuIr high entropy alloy nanocatalyst;

[0035] Figure 7 This is the X-ray diffraction spectrum of the PtCoNiRuIr high entropy alloy nanocatalyst supported on carbon black;

[0036] Figure 8 X-ray photoelectron spectra of PtCoNiRuIr high-entropy alloy nanocatalysts supported on carbon black: (a) full-range scan spectrum, (b) Pt 4f high-resolution scan spectrum, (c) Co 2p high-resolution scan spectrum, (d) Ni 2p high-resolution scan spectrum, (e) Ru 3p high-resolution scan spectrum, (f) Ir 4f high-resolution scan spectrum;

[0037] Figure 9 Electrocatalytic hydrogen evolution performance of PtCoNiRuIr high entropy alloy nanocatalyst in 0.5M H2SO4: (a) HER LSV curve corrected by iR; (b) at 10 mA cm -2 and 500mA cm -2 Overpotential histogram at 10000 cycles; (c) Tafel slope; (d) EIS at -0.02 V; (e) specific activity at -0.07 V; (f) HER LSV curves at initial and after 10,000 cycles; (g) stability at different current densities; (h) comparison with other noble metal-based high entropy material catalysts at 10 mA cm -2 Overpotential comparison under ;

[0038] Figure 10 The morphology and particle size distribution statistics of PtCoNiRuFe high entropy alloy nanocatalysts;

[0039] Figure 11 This is the energy spectrum distribution diagram of each element in the PtCoNiRuFe high entropy alloy nanocatalyst;

[0040] Figure 12 It is the morphology and particle size distribution statistics of PtCoNiRuZn high entropy alloy nanocatalyst. DETAILED DESCRIPTION

[0041] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the specific implementation methods, structures, features and effects of the present invention are described in detail below in conjunction with the accompanying drawings and preferred embodiments.

[0042] Example 1

[0043] The high entropy alloy nanoparticle catalyst was prepared by high temperature liquid phase impact, according to the following steps:

[0044] Step 1: Disperse equimolar ratios of acetylacetonate (8.0 mg platinum (II) acetylacetonate, 5.2 mg cobalt (II) acetylacetonate, 5.9 mg nickel (II) acetylacetonate dihydrate, 8.1 mg ruthenium (III) acetylacetonate, 9.9 mg iridium (III) acetylacetonate) and 10.0 mg Vulcan XC-72R carbon black in a mixed solution of 9.0 mL oleylamine, 1.0 mL oleic acid, and 0.8 mL 37 wt% formaldehyde. Ultrasonic stirring was performed for 30 min and magnetic stirring was performed for 2 h. During the stirring process, the mixture was sealed to prevent formaldehyde from volatilizing to obtain a uniform mixed solution precursor.

[0045] Step 2: Transfer 2.5 mL of the uniform mixed solution precursor to an insulating crucible (10 mL) fixed on carbon felt (5.5 cm × 4 cm × 1 cm). Connect the carbon felt to the two electrodes of a DC power supply. In an Ar atmosphere, maintain a current of 38 A for 60 s. After cooling, a crude product of high-entropy alloy nanoparticles can be obtained.

[0046] Step 3: The crude high-entropy alloy nanoparticle product is washed multiple times by high-speed centrifugation. The washing solvent is a mixed solvent of n-hexane and anhydrous ethanol in a volume ratio of 1:1. The centrifugal speed is 10,000 rpm / min and the centrifugal time is 3 minutes. The solvent is washed until it is transparent and colorless to remove impurities and organic residues, and the high-entropy alloy nanoparticle catalyst product is collected.

[0047] The mechanism of preparing high entropy alloy nanoparticle catalysts by high temperature liquid phase impact method is as follows Figure 1As shown, acetylacetonate serves as a metal donor, carbon black serves as a metal carrier, and formaldehyde serves as an auxiliary reducing agent, dispersed in a mixed solution of oleylamine and oleic acid. Oleylamine and oleic acid act as both surfactants and solvents, providing the high-temperature liquid phase environment required for high-temperature liquid phase shock. Through ultrasonic and magnetic stirring, the acetylacetonate decomposes into metal cations and acetylacetonate ions in the solution. Due to the charge interaction, the metal cations undergo electrostatic adsorption on the carbon black surface. Subsequently, after 60 seconds of high-temperature liquid phase shock (HTLS) treatment in an argon atmosphere, the metal cations aggregate and nucleate on the carbon black surface, accompanied by the dispersion and thin layer coating of organic molecules at the alloy interface. Finally, rapid cooling forms uniformly sized, well-dispersed single-crystalline high-entropy alloy nanoparticle catalysts.

[0048] Figure 2-9 This is the relevant characterization of high entropy alloy nanoparticle catalyst (PtCoNiRuIr / C) uniformly loaded on carbon black prepared by high-temperature liquid phase impact method.

[0049] Figure 2 (a) is a low-magnification transmission electron microscope (TEM) image of PtCoNiRuIr / C. Figure 2 (b) shows the corresponding particle size distribution. This indicates that the average particle size of the high-entropy alloy nanoparticles is approximately 3 nm, and they are uniformly supported on the carbon black substrate with no apparent agglomeration. The ultra-small size and excellent uniformity of the high-entropy alloy nanoparticles are attributed to the liquid phase environment and the dispersion and coating effects of the organic matter. Liquid-phase methods allow for precise control of the chemical composition, making it easier to manipulate the size, morphology, crystal phase, and defects of the nanomaterials.

[0050] Figure 3 Table 1 summarizes the particle size statistics and reaction time of high-entropy alloy nanocatalysts prepared by different methods. Compared with millisecond-level laser pulse irradiation (LPI) and carbon thermal shock method (CTS), and second-level microwave heating method (MH), the high-entropy alloy prepared by the high-temperature liquid phase impact method of the present invention has a smaller particle size, and compared with high-entropy alloys of similar particle size prepared by one-pot oil phase synthesis method (OPOPS), the high-temperature liquid phase impact method can greatly save time and reduce costs. In other words, the high-temperature liquid phase impact method of the present invention for preparing high-entropy alloys has great advantages in optimizing particle size and shortening reaction time.

[0051] Figure 4 (a) is a high-resolution transmission electron microscopy (HRTEM) image of PtCoNiRuIr / C and its local magnification (b). The image clearly shows that the high-entropy alloy nanoparticle catalyst is uniformly sized and dispersed on the carbon black surface without aggregation, with a lattice spacing of 0.21 nm, corresponding to the (111) crystal plane of the fcc phase.

[0052] Figure 5 (a) is the stress-strain analysis of high-entropy alloy nanoparticles on the (111) crystal plane. It can be seen that due to the different radii of metal atoms in PtCoNiRuIr high-entropy alloy nanoparticles, a lattice distortion effect is produced, causing them to have certain microscopic strains. This also indirectly proves that the prepared high-entropy alloy nanoparticles are a multi-metal element solid solution structure.

[0053] Figure 5 (b) Yes Figure 4 (a) The corresponding fast Fourier transform image shows clearly the presence of two diffraction rings, corresponding to the (200) and (111) crystal planes of the fcc phase, respectively.

[0054] Figure 6 It is the energy spectrum surface scan distribution diagram of the corresponding elements. It can be seen from the figure that the five elements Pt, Ni, Co, Ru and Ir are evenly distributed without obvious phase segregation, which further confirms the single-phase polycrystalline solid solution structure of high-entropy alloy nanoparticles.

[0055] Figure 7 The X-ray diffraction (XRD) pattern of PtCoNiRuIr / C shows that due to the ultra-small size structure (3.24 nm) of the high-entropy alloy nanoparticles, good dispersion on the carbon black surface and low loading, no obvious diffraction peaks of metal elements were detected. Only the characteristic peak at 42.9° was enhanced to a certain extent, corresponding to the (111) crystal plane of the fcc phase, indicating that the (111) crystal plane is dominant in the sample, which is consistent with the Figure 5 The conclusion of the fast Fourier transform of (b) is consistent.

[0056] Figure 8 This is the X-ray photoelectron spectrum of PtCoNiRuIr / C, showing the presence of the five elements Pt, Co, Ni, Ru, and Ir. Due to the alloying effect and high entropy stability, Pt, Co, Ni, Ru, and Ir are all primarily present in a zero-valent state.

[0057] Figure 9 The excellent electrocatalytic hydrogen evolution performance of PtCoNiRuIr high entropy alloy nanoparticles in 0.5M H2SO4 was demonstrated. A 20wt% commercial Pt / C catalyst was selected as a reference, and all potentials were calibrated using a reversible hydrogen electrode (RHE).

[0058] Figure 9 (ac) It can be seen that PtCoNiRuIr / C at 10mA cm -2 and 500mA cm -2 When the overpotential of PtCoNiRuIr / C is only 18mV and 223mV, it has an extremely low Tafel slope of only 34.2mV dec.-1 , which are far superior to commercial Pt / C.

[0059] It is worth noting that PtCoNiRuIr / C has a -2 The overpotential is only 408 mV at a high current density, making it a potential acidic industrial water electrolysis catalyst.

[0060] Figure 9 (d) and (e) show that PtCoNiRuIr / C has higher charge transfer rate and intrinsic activity than commercial Pt / C.

[0061] Figure 9 (f) and (g) show that PtCoNiRuIr / C has long-term working stability in acidic medium.

[0062] Figure 9 (h) PtCoNiRuIr / C and other noble metal-based high entropy material catalysts at a current density of 10 mA cm -2 From the comparison of the overpotentials at , it can be seen that among the current catalysts of the same type, PtCoNiRuIr / C has relatively excellent electrocatalytic hydrogen evolution activity.

[0063] Example 2

[0064] Step 1: Disperse equimolar ratios of acetylacetonate (16.0 mg platinum (II) acetylacetonate, 10.4 mg cobalt (II) acetylacetonate, 10.18 mg nickel (II) acetylacetonate dihydrate, 16.2 mg ruthenium (III) acetylacetonate, and 12.6 mg ferrous (II) acetylacetonate) and 20.0 mg Vulcan XC-72R carbon black in a mixed solution of 18.0 mL oleylamine, 2.0 mL oleic acid, and 1.6 mL 37 wt% formaldehyde. Ultrasonic stirring was performed for 30 min and magnetic stirring was performed for 2 h. During the stirring process, sealing was performed to prevent formaldehyde from volatilizing to obtain a uniform mixed solution precursor.

[0065] Step 2: Transfer 5 mL of the uniform mixed solution precursor to an insulating crucible (20 mL) fixed on a carbon felt (5.5 cm × 4 cm × 1 cm). Connect the carbon felt to the two electrodes of a DC power supply. In an Ar atmosphere, maintain a current of 45 A for 120 s. After cooling, a crude product of high-entropy alloy nanoparticles can be obtained.

[0066] Step 3: The crude high-entropy alloy nanoparticle product is washed multiple times by high-speed centrifugation. The washing solvent is a mixed solvent of n-hexane and anhydrous ethanol in a volume ratio of 1:1. The centrifugal speed is 8000 rpm / min and the centrifugal time is 5 minutes. The solvent is washed until it is transparent and colorless to remove impurities and organic residues, and the high-entropy alloy nanoparticle catalyst product is collected.

[0067] Figure 10 (a) is a transmission electron microscope image of PtCoNiRuFe high entropy alloy. Figure 10 (b) is the corresponding particle size statistical distribution; Figure 11 This is the energy spectrum distribution diagram of each element in PtCoNiRuFe high entropy alloy nanoparticles. Figure 10 and 11 The product prepared in this example was characterized by TEM and EDS, which proved that the particle size was ultra-small and the carbon black was evenly loaded on the surface.

[0068] Example 3

[0069] Step 1: Disperse chloroplatinic acid, acetate (4.1 mg chloroplatinic acid hydrate (H2PtCl6·xH2O), 2.5 mg cobalt acetate tetrahydrate (C4H6CoO4·4H2O), 2.5 mg nickel acetate tetrahydrate (NiC4H6O4·4H2O), 2.9 mg ruthenium acetate (C6H9O6Ru), 1.9 mg zinc acetate (C4H6O4Zn)) and 5.0 mg ketjen black EC-600JD carbon black in an equal molar ratio in a mixed solution of 4.5 mL oleylamine, 0.5 mL oleic acid and 0.4 mL 37 wt% formaldehyde, ultrasonically stir for 30 min, magnetically stir for 2 h, and seal during the stirring process to prevent formaldehyde from volatilizing to obtain a uniform mixed solution precursor.

[0070] Step 2: Transfer 2 mL of the uniform mixed solution precursor to an insulating crucible (10 mL) fixed on a carbon felt (5.5 cm × 4 cm × 1 cm). Connect the carbon felt to the two electrodes of a DC power supply. In an Ar atmosphere, maintain a current of 38 A for 60 s. After cooling, a crude product of high-entropy alloy nanoparticles can be obtained.

[0071] Step 3: Wash the crude high-entropy alloy nanoparticle product multiple times by filtering, using a mixed solvent of n-hexane and anhydrous ethanol in a volume ratio of 1:1, and filtering using 70mm medium-speed filter paper; washing until the solvent is transparent and colorless, removing impurities and organic residues, and collecting the high-entropy alloy nanoparticle catalyst product.

[0072] Figure 12 (a) is a transmission electron microscope image of PtCoNiRuZn high entropy alloy. Figure 12 (b) is the corresponding particle size statistical distribution. Figure 12 The product prepared in this example was characterized by TEM, which proved that the particle size was ultra-small and the carbon black was evenly loaded on the surface.

[0073] Table 1 Comparison of high temperature liquid phase impact method with other methods

[0074]

[0075] Table 2 Element content of PtCoNiRuIr high entropy alloy

[0076]

[0077] Comparative Example

[0078] Comparison of a solid-phase rapid thermal shock method for preparing high-entropy alloys (Carbon Thermal Shock Method, CTS, Reference: Science 359, 2018, 1489)

[0079] Step 1: Dissolve the chloride metal salt solution in ethanol in an equal molar ratio to prepare a precursor solution with a concentration of 0.05 nmol / L, where n is the total number of elements; the metal salt used is MCl x H y (M is five or more of Pt, Pd, Ni, Fe, Co, Au, Cu, and Sn).

[0080] Step 2: Drop the precursor solution obtained in step 1 onto a carbon support and dry it at room temperature; the carbon support is a homemade carbon nanofiber, and the precursor solution loading is 120 μL / cm 2 .

[0081] Step 3: Connect the carrier obtained in step 2 to an external power supply and perform Joule thermal shock treatment in an argon atmosphere; the external power supply used for thermal shock is Keithley 2425, the thermal shock temperature is 2000K, and the time is 55ms.

[0082] The particle size of the high-entropy alloy nanoparticle catalyst prepared by this carbon thermal shock method is about 5nm, and the amount of sample prepared is small. Compared with the high-entropy alloy nanoparticles prepared by high-temperature liquid phase shock, at the macroscopic level, due to the lack of regulation of the liquid phase environment, there are differences in large particle size, small product and not easy industrial production; in the preparation research of nano-scale high-entropy alloys, breaking through the particle size to below 5nm is a very challenging task. The high-entropy alloy particle size prepared by high-temperature liquid phase shock of the present invention is only 3nm, which is 40% higher than that of solid-phase thermal shock. This is of great significance for increasing the specific surface area of ​​the catalyst, increasing the number of catalytic active sites, and improving atomic utilization efficiency; in addition, at the microscopic level, due to the extremely short (millisecond level) thermal shock time of the solid-phase thermal shock method, it also brings certain challenges to the in-situ characterization technology (such as in-situ electron microscopy, electron diffraction) and mechanism exploration during the synthesis process.

[0083] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can, without departing from the scope of the technical solution of the present invention, make some changes or modifications to equivalent embodiments using the technical contents disclosed above. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for preparing high entropy alloy nanocatalysts by high-temperature liquid phase impact, characterized in that: The following steps are involved: Step 1: Prepare mixed solution precursor First, a carbon black carrier and at least five metal salts are weighed in proportion and mixed with a surfactant solvent and an auxiliary reducing agent. The mixture is then stirred to obtain a uniformly dispersed mixed solution precursor. Different metal salts are taken in equal molar ratios. The mass ratio of the single metal element in the metal salt to the carbon black carrier is 1 to 2:

10. Step 2: In a protective atmosphere, the mixed solution precursor obtained in step 1 is placed in a container, fixed on a heated substrate, and directly subjected to high-temperature liquid phase impact to obtain a crude product of high-entropy alloy nanoparticles; Step 3: Separating and washing the crude high entropy alloy nanoparticles obtained in step 2 to obtain a high entropy alloy nanoparticle catalyst; The surfactant solvent is one or more of oleylamine, oleic acid, and dodecane, and the total amount of the surfactant solvent is 5 to 20 mL; the auxiliary reducing agent is a 37 wt% formaldehyde solution, and the amount is 0.4 to 1.6 mL; the mass volume ratio of the carbon black carrier to the surfactant solvent and the auxiliary reducing agent is 1 mg:1 ml:0.08 ml; The mixed solution precursor is used in an amount of 2-5 mL and transferred to a 10-20 mL container, which is an insulating crucible; the heating substrate is a 5.5 cm × 4 cm × 1 cm carbon felt; the high-temperature liquid phase impact conditions are: the current is 30-45 A, and the duration is 60-120 s.

2. The method according to claim 1, characterized in that The metal salts in step 1 belong to the same type of metal salts, specifically acetylacetonate metal salts, halide metal salts, nitrate metal salts, sulfate metal salts or acetate metal salts.

3. The method according to claim 2, characterized in that The acetylacetonate metal salts include: platinum acetylacetonate, palladium acetylacetonate, rhodium acetylacetonate, cobalt acetylacetonate, nickel acetylacetonate, ruthenium acetylacetonate, iridium acetylacetonate, iron acetylacetonate, copper acetylacetonate, manganese acetylacetonate, and zinc acetylacetonate; the halide metal salts include: chloroplatinic acid and its derivatives, chloropalladic acid and its derivatives, rhodium chloride, cobalt chloride, ruthenium chloride, nickel chloride, and copper chloride; the nitrate metal salts include: nickel nitrate, copper nitrate, cobalt nitrate, zinc nitrate, ferrous nitrate, and manganese nitrate; the sulfate metal salts include: nickel sulfate, copper sulfate, cobalt sulfate, zinc sulfate, ferrous sulfate, and manganese sulfate; the acetate metal salts include: nickel acetate, copper acetate, cobalt acetate, zinc acetate, ferrous acetate, and manganese acetate.

4. The method according to claim 1, wherein The carbon black supports include Vulcan XC-72R, Vulcan XC-72, Vulcan P, BP 2000, and ketjen black EC-600JD, which are treated by soaking in 0.2 M nitric acid for 12 hours and then washed.

5. The method according to claim 1, wherein The protective atmosphere is one or more of helium, neon, argon, krypton, xenon and nitrogen.

6. The method according to claim 1, characterized in that The current is 38 A and the duration is 60 s.

7. The method according to claim 1, characterized in that The separation method is centrifugation or filtration, the centrifugal speed is 8000-10000 rpm / min, and the centrifugal time is 3-5 min; 70 mm medium-speed filter paper is used for filtration; and the washing solvent is a mixed solution of n-hexane and ethanol in a volume ratio of 1:1.

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