Preparation method of six-element high-entropy alloy nanosheet catalyst

Abstract

The invention discloses a preparation method of a six-element high-entropy alloy nanosheet catalyst, which comprises the following steps: 1) dissolving six metal salts with equal molar ratio or approximate equal molar ratio in a solvent to obtain a metal precursor solution; (2) adding a surfactant into the metal precursor solution, mixing, and carrying out ultrasonic treatment to uniformly disperse the metal precursor solution to obtain a solution A; (3) NaOH is dissolved in water and mixed with a reducing agent sodium borohydride to obtain a reducing solution, then the reducing solution is dropwise added into the solution A while being stirred, after dropwise adding is completed, stirring continues to be conducted, the temperature is increased to the reaction temperature, the temperature is reduced to the room temperature after the reaction is completed, and high-entropy alloy coarse particles are obtained through reduction after the reaction is sufficient; and (4) the high-entropy alloy rough nanosheet is subjected to aftertreatment, and the high-entropy alloy particles are obtained. The preparation method has the advantages that the HEAs type preparation range is wide, the process conditions are mild and friendly, equipment is simple and easy to operate, the HEAs particles are small in particle size and highly uniform in component, and the yield is remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of high-entropy alloys. More specifically, it relates to a method for preparing a six-component high-entropy alloy nanosheet catalyst. Background Art

[0002] The preparation development history of high-entropy alloys (HEAs) can be traced back to several key nodes. In the early exploration stage, a German chemist, Franz Karl Achard, prepared a series of alloys containing 5-7 metals at the end of the 18th century, but this work did not attract extensive attention from researchers. In 1963, the British metallurgist Cyril Stanley Smith noticed Achard's work and reported it in the academic community, but the development of high-entropy alloys did not accelerate significantly as a result.

[0003] In the 1990s, Professor Cantor at the University of Cambridge and Professor Ye Junwei at Tsinghua University conducted research on equiatomic alloys [Cantor B, Chang I, Knight P, et al. Microstructural development in equiatomic multicomponent alloys. Mater Sci Eng-A, 2004, 375–377: 213–218.], and successfully prepared the FeCoNiCrMn high-entropy alloy with an FCC single-phase solid solution structure, laying the foundation for the formation of the concept of high-entropy alloys. In 2004, Professor Ye Junwei officially proposed and defined the concept of high-entropy alloys (HEAs). High-entropy alloys are generally defined as alloys composed of five or more elements, with the percentage of each element between 5% and 35%, and capable of forming a high-entropy solid solution.

[0004] With the in-depth research, researchers found that HEAs have the characteristics of four major effects, namely, the high-entropy effect, the lattice distortion effect, the cocktail effect, and the sluggish diffusion effect, and perform excellently in various fields of application. In the catalytic field, HEAs are formed by five or more metal elements. This combination of multiple elements brings a rich compositional space and a complex atomic structure, and its microstructure has a high degree of tunability, showing significant catalytic performance in catalytic reactions. At the same time, HEAs catalysts have rich active sites and stability, which helps to reduce energy consumption and waste emissions during the catalytic process, conforming to the concepts of green chemistry and sustainable development, and have become a research hotspot in the fields of materials science and electrocatalysis in recent years. However, in the preparation process of HEAs nanosheets, there are problems such as too large differences in the properties of elements, difficult control of phase separation, and easy formation of large particles under high-temperature conditions. Currently, the common preparation methods of HEAs are as follows:

[0005] 1) Carbothermal shock method

[0006] Load at least eight different elemental alloys on carbon nanofibers and anneal them at high temperature to form HEAs nanoparticles. However, this method requires high experimental equipment requirements, high energy consumption and complex processes. [①Xie, P.; Yao, Y.; Huang, Z.; Liu, Z.; Zhang, J.; Li, T.; Wang, G.; Shahbazian-Yassar, R.; Hu, L.; Wang, C. Highly Efficient Decomposition of Ammonia Using High-Entropy Alloy Catalysts. Nat. Commun. 2019, 10, 4011.; ②Yao, Y.; Liu, Z.; Xie, P.; Huang, Z.; Li, T.; Morris, D.; Finfrock, Z.; Zhou, J.; Jiao, M.; Gao, J. Computationally aided, entropy-driven synthesis of highly efficient and durable multi-elemental alloy catalysts. Sci. Adv. 2020, 6, eaaz0510.; ③Yao, Y.; Huang, Z.; Xie, P.; Lacey, S. D.; Jacob, R. J.; Xie, H.; Chen, F.; Nie, A.; Pu, T.; Rehwoldt, M. Carbothermal Shock Synthesis of High-Entropy-Alloy NPs. Science 2018, 359, 1489–1494.].

[0007] 2) Mechanical alloying method

[0008] Through mechanical alloying, Lv et al. successfully synthesized AlCoCrTiZn, AlCoCrFeNi and CoCrFeMnNi powders. However, the alloys synthesized by the solid-phase synthesis method have too large sizes, and the high-energy collision reaction may cause defects inside the alloys, affecting the catalytic performance [Lv, Z. Y.; Liu, X. J.; Jia, B.; Wang, H.; Wu, Y.; Lu, Z. P. Development of a Novel High-Entropy Alloy with Eminent Efficiency of Degrading Azo Dye Solutions. Sci. Rep. 2016, 6, 34213, 7].

[0009] 3) Spray deposition method

[0010] By controlling the spraying parameters, Schuhmann et al. used an Ar plasma to conduct high-energy impact on an elemental target. The metal elements in the target were sputtered and dispersed into an ionic solution, realizing the in-situ generation of nanoparticles in the liquid and synthesizing highly dispersed HEAs nanoparticles T.; Meyer, H.; Savan, A.; Wilde, P.; Garzón Manjón, A.; Chen, Y.-T.; Ventosa, E.; Scheu, C.; Ludwig, A.; Schuhmann, W. Discovery of a Multinary Noble Metal-Free Oxygen Reduction Catalyst. Adv. Energy Mater. 2018, 8, 1802269.]。

[0011] There are also many methods for the preparation of HEAs. For example, the high-entropy alloy powders disclosed in Chinese patent applications CN104646660A, CN104651818A, CN104561990A, and CN104550901A are all prepared by ball milling or mortar grinding methods. Chinese patent application CN104561878A uses a consumable electrode to prepare high-entropy alloy powders. Chinese patent application CN106119663A uses a melting aerosol one-step method to spray high-entropy alloy powder materials on the surface of a cement rotary kiln.

[0012] The above common preparation methods of HEAs have deficiencies such as complex equipment, cumbersome process operations, or too large catalyst particle sizes, and it is necessary to find a better preparation method for HEAs. Summary of the Invention

[0013] The technical problem to be solved by the present invention is to provide a preparation method for a six-component high-entropy alloy nanosheet catalyst; the significant advantages of the preparation method of the present invention include: a wide range of HEAs types can be prepared, the process conditions are mild and friendly, the equipment is simple and easy to operate, the post-treatment is simple, the thickness of the HEAs nanosheets is thin, the composition is highly uniform, and the yield is significantly improved.

[0014] To solve the above technical problems, the technical solution adopted by the present invention is as follows :

[0015] A preparation method for a six-component high-entropy alloy nanosheet catalyst, comprising the following steps:

[0016] 1) Dissolve six metal salts with equimolar ratios or approximate equimolar ratios in a solvent to obtain a metal precursor solution;

[0017] 2) Add the metal precursor solution to the surfactant and mix to prevent the nanosheets from aggregating and settling, which helps to regularize the growth morphology of the nanosheets. Then perform ultrasonic treatment to make it evenly dispersed to obtain Solution A;

[0018] 3) Dissolve NaOH in water, mix it with the reducing agent sodium borohydride to obtain a reducing solution, and then drop it into Solution A while stirring. After the dropping is completed, continue to stir and heat up to the reaction temperature. After the reaction, cool down to room temperature to fully reduce the as-prepared high-entropy alloy nanosheets;

[0019] 4) Perform post-treatment on the as-prepared high-entropy alloy nanosheets to obtain high-entropy alloy nanosheets.

[0020] Further, in step 1), the six metal salts are selected from any six of the following substances: copper chloride, manganese chloride, platinum chloride, potassium chloropalladite, cobalt hexanitrate, cobalt chloride, nickel chloride, iron chloride, zinc chloride, bismuth chloride, palladium chloride, molybdate, chromium chloride.

[0021] Further, in step 1), the concentration of each metal salt in the metal precursor solution is 0.02 - 0.08 ml / L; preferably 0.03 - 0.05 mol / L.

[0022] Further, in step 1), the solvent is selected from one or more of the following substances: pure water, ethanol, methanol, ethylene glycol, isopropanol.

[0023] Further, in step 2), the surfactant is PVP; the dosage of the surfactant is 30% - 70% of the total mass of the six metal salts, preferably 40% - 60%.

[0024] Further, in step 2), the ultrasonic treatment time is 0.5 - 2 h, preferably, the ultrasonic treatment time is 1 - 1.5 h.

[0025] Further, in step 3), the molar ratio of the reducing agent to NaOH is 1:0.3 - 0.8, preferably 1:0.4 - 0.6.

[0026] Further, in step 3), the concentration of the reducing agent in the reducing solution is 0.1 - 0.5 mol / L, preferably 0.2 - 0.3 mol / L; the dropping rate of the reducing solution is 5 - 10 ml / min, preferably 5 - 8 ml / min; the reaction temperature is 50°C - 100°C, and the reaction time is 0.5 h - 3 h.

[0027] Further, in step 3), the reaction temperature is 80°C - 100°C, and the reaction time is 1 h - 2 h.

[0028] Further, in step 4), the post-treatment includes centrifugation, washing, and vacuum drying; the washing uses a mixed solution of ethanol and water.

[0029] Any range described in the present invention includes the end values, any numerical value between the end values, and any sub-range formed by any numerical value between the end values or the end values.

[0030] Unless otherwise specified, each raw material in the present invention can be obtained by purchasing from the market, and the equipment used in the present invention can be a conventional equipment in the field or can be referred to the existing technology in the field.

[0031] Compared with the prior art, the present invention has the following beneficial effects :

[0032] 1) Strong universality: The method of the present invention is applicable to the combination of multiple metal elements and can prepare high-entropy alloy nanosheets with various components;

[0033] 2) Simple and easy to operate: The required equipment is simple, the operation process is easy to control, and the reaction conditions are mild (the reaction temperature in the present invention is 100 °C under normal pressure conditions);

[0034] 3) Superior performance: The prepared high-entropy alloy nanosheets are uniform and fine (about between), have high stability and activity, low cost, and are applicable to the catalytic field. Description of the Drawings

[0035] The following further describes in detail the specific embodiments of the present invention with reference to the drawings

[0036] Figure 1 It is the electron microscope image of the PtFeCoNiCuMn six-element high-entropy alloy nanosheets prepared in Example 1 of the present invention;

[0037] Figure 2 It is the atomic ratio distribution diagram of each element of the PtFeCoNiCuMn six-element high-entropy alloy nanosheets prepared in Example 1 of the present invention characterized by ICP-OES / MS;

[0038] Figure 3 It is the STEM image of the PtFeCoNiCuMn six-element high-entropy alloy nanosheets sample prepared in Example 1 of the present invention;

[0039] Figure 4 It is the electron microscope image of the six-element high-entropy alloy nanosheets prepared in Comparative Example 1 of the present invention;

[0040] Figure 5 It is the electron microscope image of the six-element high-entropy alloy nanosheets prepared in Comparative Example 2 of the present invention;

[0041] Figure 6 It is the electron microscope image of the six-element high-entropy alloy nanosheets prepared in Comparative Example 3 of the present invention;

[0042] Figure 7 XRD pattern of the high-entropy alloy PtFeCoNiCuZn six-component high-entropy alloy nanosheets prepared in Example 2 of the present invention. Detailed implementation manners

[0043] To describe the present invention more clearly, the present invention will be further described below in conjunction with preferred embodiments and the accompanying drawings. Similar components in the drawings are denoted by the same reference numerals. Those skilled in the art should understand that the content specifically described below is illustrative rather than restrictive, and should not be used to limit the protection scope of the present invention.

[0044] Various cross-sectional views according to the disclosed embodiments of the present invention are shown in the drawings. These figures are not drawn to scale, where for the purpose of clear illustration, some details are enlarged and some details may be omitted. The shapes of various regions and layers shown in the figures, as well as their relative sizes and positional relationships, are merely exemplary and may deviate in practice due to manufacturing tolerances or technical limitations. And those skilled in the art can design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0045] As an aspect of the present invention, a method for preparing a six-component high-entropy alloy nanosheet catalyst of the present invention includes the following steps:

[0046] 1) Dissolve six metal salts in an equimolar ratio or an approximate equimolar ratio in a solvent to obtain a metal precursor solution;

[0047] 2) Add the metal precursor solution to a surfactant and mix to prevent the nanosheets from aggregating and help regulate the growth morphology of the nanosheets. Then, perform ultrasonic treatment to make it uniformly dispersed to obtain Solution A;

[0048] 3) Dissolve NaOH in water and mix it with the reducing agent sodium borohydride to obtain a reducing solution, and then drop it into Solution A while stirring. After the dropping is completed, continue to stir and heat up to the reaction temperature. After the reaction, cool down to room temperature to fully reduce the high-entropy alloy crude nanosheets;

[0049] 4) Post-treat the high-entropy alloy crude sheets to obtain high-entropy alloy nanosheets.

[0050] According to certain embodiments of the present invention, in step 1), the six metal salts are selected from any six of the following substances: copper chloride, manganese chloride, platinum chloride, potassium chloropalladite, cobalt hexanitrate, cobalt chloride, nickel chloride, iron chloride, zinc chloride, bismuth chloride, palladium chloride, molybdate, chromium chloride.

[0051] According to certain embodiments of the present invention, in step 1), the concentration of various metal salts in the metal precursor solution is 0.02 - 0.08 ml / L; preferably 0.03 - 0.05 mol / L.

[0052] According to certain embodiments of the present invention, in step 1), the solvent is selected from one or more of the following substances: pure water, ethanol, methanol, ethylene glycol, isopropanol.

[0053] According to certain embodiments of the present invention, in step 2), the surfactant is PVP; the dosage of the surfactant is 30% - 70% of the total mass of the six metal salts, preferably 40% - 60%.

[0054] According to certain embodiments of the present invention, in step 2), the ultrasonic time is 0.5 - 2 h, preferably, the ultrasonic time is 1 - 1.5 h.

[0055] According to certain embodiments of the present invention, in step 3), the molar ratio of the reducing agent to NaOH is 1:0.3 - 0.8, preferably 1:0.4 - 0.6.

[0056] According to certain embodiments of the present invention, in step 3), the concentration of the reducing agent in the reducing solution is 0.1 - 0.5 mol / L, preferably 0.2 - 0.3 mol / L; the dropping rate of the reducing solution is 5 - 10 ml / min, preferably 5 - 8 ml / min; the reaction temperature is 50°C - 100°C, and the reaction time is 0.5 h - 3 h.

[0057] According to certain embodiments of the present invention, in step 3), the reaction temperature is 80°C - 100°C, and the reaction time is 1 h - 2 h.

[0058] It was unexpectedly found in this application that in step 3), if the metal precursor is injected into the reducing agent, the obtained nanosheets are likely to aggregate together, and injecting the reducing agent into the metal precursor is a more preferred method.

[0059] According to certain embodiments of the present invention, in step 4), the post-treatment includes centrifugation, washing, and vacuum drying.

[0060] Example 1

[0061] A method for preparing PtFeCoNiCuMn six - element high - entropy alloy nanosheets, comprising the following steps:

[0062] 1) Take potassium chloroplatinate, ferric chloride, cobalt hexacarbonyl, nickel chloride, copper chloride, and manganese chloride and mix them in equal proportions of 0.1 mmol, and dissolve them in 40 ml of water to obtain metal precursor solution 1;

[0063] 2) Take 100 mg of polyvinylpyrrolidone (PVP) and dissolve it in the metal precursor solution 1, and ultrasonicate it for 1 h to obtain solution 2;

[0064] 3) Inject the alkaline sodium borohydride solution (sodium borohydride: metal = 3:1) into the metal precursor solution 2 at a rate of 5 ml / min, heat it to 100 °C, react for 1 h, and cool it to room temperature after the reaction to obtain the catalyst flakes in the aqueous phase;

[0065] 4) Wash and centrifuge the catalyst nanosheets with the ethanol and water mixture multiple times, collect them by centrifugation, and dry them under vacuum at 80 °C to obtain the PtFeCoNiCuMn high-entropy alloy nanosheets.

[0066] Figure 1 This is the electron microscopy image of the PtFeCoNiCuMn six-component high-entropy alloy nanosheets prepared in Example 1;

[0067] Figure 2 This is the atomic ratio distribution diagram of each element of the PtFeCoNiCuMn six-component high-entropy alloy nanosheets prepared in Example 1 characterized by ICP-OES / MS;

[0068] Figure 3 This is the STEM image of the PtFeCoNiCuMn six-component high-entropy alloy nanosheet sample prepared in Example 1;

[0069] The PtFeCoNiCuMn six-component high-entropy alloy nanosheets prepared in this example have a nanosheet size of 1 nm - 50 nm; the atomic ratio of each element is Pt:Fe:Co:Ni:Cu:Mn = 16.85%:16.92%:18.69%:14.52%:16.03%:17%; the yield is 98%.

[0070] Comparative Example 1

[0071] Repeat Example 1: The difference is only that the metal precursor solution is injected into the alkaline sodium borohydride solution.

[0072] The results show that: compared with the high-entropy alloy catalyst nanosheets in Example 1, the nanosheets in this comparative example agglomerate together. This is because during the injection process, the alloy is reduced quickly, the nanosheets aggregate quickly, and agglomeration occurs, resulting in the adhesion of the nanosheets.

[0073] Figure 4 This is the electron microscopy image of the six-component high-entropy alloy nanosheets prepared in this comparative example.

[0074] Comparative Example 2

[0075] Repeat Example 1: The difference is only that the amount of polyvinylpyrrolidone (PVP) is 150 mg.

[0076] The results show that there are problems of uneven distribution and agglomeration in the high-entropy alloy catalyst in this comparative example. This is mainly because the addition ratio of the flocculant is too high, which accelerates the aggregation process between the nanosheets, resulting in the adhesion and uneven distribution of the high-entropy alloy nanosheets.

[0077] Figure 5 This is the electron microscopy image of the six-component high-entropy alloy nanosheets prepared in this comparative example.

[0078] Comparative Example 3

[0079] Repeat Example 1: The only difference is that the injection rate of the reducing agent into the metal precursor solution is 10 ml / min.

[0080] In this comparative example, the high-entropy alloy catalyst has problems of too large particle size (50 nm - 200 nm) and difficult-to-control morphology change. The main reason is that the reducing agent is injected into the metal precursor solution too quickly, resulting in too fast local reduction of the metal solution, causing agglomeration and leading to the aggregation of the nanosheets.

[0081] Figure 6 This is the electron microscopy image of the six-component high-entropy alloy nanosheets prepared in this comparative example.

[0082] Example 2

[0083] A preparation method of a PtFeCoNiCuZn high-entropy alloy nanosheet catalyst includes the following steps:

[0084] 1) Take potassium chloroplatinate, ferric chloride, hexa-cobaltate, nickel chloride, copper chloride, and zinc chloride and mix them in equal proportions of 0.05 mmol, and dissolve them in 30 ml of solution to obtain metal precursor solution 1;

[0085] 2) Take 80 mg of polyvinylpyrrolidone (PVP) and dissolve it in metal precursor solution 1, and ultrasonicate it for 1 h to obtain solution 2;

[0086] 3) Inject the alkaline sodium borohydride solution (sodium borohydride: metal = 3:1) into metal precursor solution 2 at a rate of 5 ml / min, and heat it to 100 °C, with a reaction time of 1 h. After the reaction, cool it to room temperature to obtain the aqueous-phase catalyst;

[0087] 4) Wash and centrifuge the catalyst with a mixed solution of ethanol and water multiple times. After centrifugal collection, dry it under vacuum at 80 °C to obtain the PtFeCoNiCuZn high-entropy alloy.

[0088] Figure 7 This is the XRD pattern of the high-entropy alloy PtFeCoNiCuZn six-component high-entropy alloy prepared in this example.

[0089] Example 3

[0090] A preparation method of a PtFeCoNiCuBi high-entropy alloy nanosheet catalyst, comprising the following steps:

[0091] 1) Potassium chloroplatinate, iron chloride, cobalt hexacarbonate, nickel chloride, copper chloride, and bismuth chloride are mixed in an equal proportion of 0.1 mmol and dissolved in 40 ml of a solution to obtain a metal precursor solution 1;

[0092] 2) 100 mg of polyvinylpyrrolidone (PVP) is dissolved in the metal precursor solution 1 and ultrasonicated for 1 h to obtain a solution 2;

[0093] 3) An alkaline sodium borohydride solution (sodium borohydride: metal = 3:1) is injected into the metal precursor solution 2 at a rate of 5 ml / min, heated to 100 °C, reacted for 1 h, and cooled to room temperature after the reaction to obtain an aqueous-phase catalyst;

[0094] 4) The catalyst is washed and centrifuged multiple times with a mixed solution of ethanol and water, centrifuged and collected, and then vacuum-dried at 80 °C to obtain a PtFeCoNiCuBi high-entropy alloy.

[0095] Example 4

[0096] A preparation method of a PtFeCoNiCuPd high-entropy alloy nanosheet catalyst, comprising the following steps:

[0097] 1) Potassium chloroplatinate, iron chloride, cobalt hexacarbonate, nickel chloride, copper chloride, and palladium chloride are mixed in an equal proportion of 0.1 mmol and dissolved in 40 ml of a solution to obtain a metal precursor solution 1;

[0098] 2) 100 mg of polyvinylpyrrolidone (PVP) is dissolved in the metal precursor solution 1 and ultrasonicated for 1 h to obtain a solution 2;

[0099] 3) An alkaline sodium borohydride solution (sodium borohydride: metal = 3:1) is injected into the metal precursor solution 2 at a rate of 5 ml / min, heated to 100 °C, reacted for 1 h, and cooled to room temperature after the reaction to obtain an aqueous-phase catalyst nanosheet;

[0100] 4) The catalyst nanosheet is washed and centrifuged multiple times with a mixed solution of ethanol and water, centrifuged and collected, and then vacuum-dried at 80 °C to obtain a PtFeCoNiCuPd high-entropy alloy nanosheet.

[0101] Comparative Example 4

[0102] A preparation method of a PdPtRuRhAu high-entropy alloy nanoparticle catalyst, comprising the following steps:

[0103] 1) Dissolve 35 mg of AuCl 3 , 20.5 mg of RhCl 3 , 20.5 mg of RuCl 3 , 41.5 mg of K 2 PtCl 4 , 32.5 mg of K 2 PdCl 4 in 10 mL of H 2 O to prepare a metal precursor solution;

[0104] 2) Preheat 160 mg of polyvinylpyrrolidone (PVP) and 80 mL of triethylene glycol (TEG) in an oil bath at 150 °C for the preparation of the preheated reduction phase;

[0105] 3) Drop the metal precursor solution into the preheated reducing agent at a rate of 2.5 mL·min-1, and cool to room temperature after the reaction to obtain catalyst particles in the oil phase;

[0106] 4) Extract the catalyst flakes in the oil phase with a mixed solution of ethanol and ether for 8 hours, then wash the catalyst particles multiple times with a mixed solution of water and ether, collect by centrifugation and vacuum dry at room temperature to obtain PdPtRuRhAu high-entropy alloy nanoparticles.

[0107] This comparative example compares the method of preparing PdPtRuRhAu quinary high-entropy alloy by the existing publicly disclosed patent method (202410058910.9) with the method of preparing PdFeCoNiCuMn high-entropy alloy in Example 1 of the present invention.

[0108] The present invention prepares high-entropy alloy nanosheets with high yield by adjusting the reaction sequence of the metal precursor solution with the reducing agent and the surfactant and reducing the reaction temperature. Moreover, in this comparative example, it is necessary to use a mixed solution of ethanol and ether for extraction for 8 hours, and the operation process is time-consuming. The ether solution is toxic, has certain safety hazards, and has high production costs. In the present invention, organic solvent extraction is not required, and it has the advantages of high efficiency, high product yield, and environmental friendliness.

[0109] Obviously, the above-mentioned embodiments of the present invention are merely examples for clearly explaining the present invention, rather than limiting the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is impossible to enumerate all the implementation manners here. Any obvious changes or modifications derived from the technical solutions of the present invention still fall within the protection scope of the present invention.

Claims

1. A method for preparing a hexavalent high entropy alloy nanosheet catalyst, characterized in that: The steps include: 1) dissolving six metal salts in an equal molar ratio or a nearly equal molar ratio in a solvent to obtain a metal precursor solution; 2) adding a surfactant to the metal precursor solution and mixing the mixture, and then ultrasonicating the mixture to make it evenly dispersed, thereby obtaining a solution A; 3) dissolving NaOH in water and mixing it with reducing agent sodium borohydride to obtain a reducing solution, then dropping it into solution A while stirring. After the dropping is completed, continue stirring and heat it to the reaction temperature. After the reaction, cool it to room temperature to allow the reaction to fully reduce the crude high entropy alloy nanosheets. 4) Post-processing the crude high entropy alloy nanosheets to obtain high entropy alloy nanosheets.

2. The method for preparing the hexavalent high entropy alloy nanosheet catalyst according to claim 1, characterized in that: In step 1), the six metal salts are selected from any six of the following substances: copper chloride, manganese chloride, platinum chloride, potassium chloropalladate, hexacobalt nitrate, cobalt chloride, nickel chloride, iron chloride, zinc chloride, bismuth chloride, palladium chloride, molybdate, and chromium chloride.

3. The method for preparing the hexavalent high entropy alloy nanosheet catalyst according to claim 1, characterized in that: In step 1), the concentration of each metal salt in the metal precursor solution is 0.02-0.08 ml / L, preferably 0.03-0.05 mol / L.

4. The method for preparing the hexavalent high entropy alloy nanosheet catalyst according to claim 1, characterized in that: In step 1), the solvent is selected from one or more of the following substances: purified water, ethanol, methanol, ethylene glycol, and isopropanol.

5. The method for preparing the hexavalent high entropy alloy nanosheet catalyst according to claim 1, characterized in that: In step 2), the surfactant is PVP; the amount of the surfactant used is 30% to 70% of the total mass of the six metal salts, preferably 40% to 60%.

6. The method for preparing the hexavalent high entropy alloy nanosheet catalyst according to claim 1, characterized in that: In step 2), the ultrasonic time is 0.5 to 2 hours; preferably, the ultrasonic time is 1 to 1.5 hours.

7. The method for preparing the hexavalent high entropy alloy nanosheet catalyst according to claim 1, characterized in that: In step 3), the molar ratio of the reducing agent to NaOH is 1:0.3-0.8; preferably 1:0.4-0.

6.

8. The method for preparing the hexavalent high entropy alloy nanosheet catalyst according to claim 1, characterized in that: In step 3), the concentration of the reducing agent in the reducing solution is 0.1-0.5 mol / L, preferably 0.2-0.3 mol / L; the dropping speed of the reducing solution is 5-10 ml / min, preferably 5-8 ml / min; the reaction temperature is 50° C.-100° C., and the reaction time is 0.5 h-3 h.

9. The method for preparing the hexavalent high entropy alloy nanosheet catalyst according to claim 8, characterized in that: In step 3), the reaction temperature is 80°C to 100°C, and the reaction time is 1h to 2h.

10. The method for preparing the hexavalent high entropy alloy nanosheet catalyst according to claim 1, characterized in that: In step 4), the post-treatment includes centrifugation, washing and vacuum drying; the washing uses a mixture of ethanol and water.

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