A method for preparing ultrathin two-dimensional Pt-based high-entropy alloy nanosheets

Abstract

The present application discloses a method for preparing ultrathin two-dimensional Pt-based high-entropy alloy nanosheets. Diethylene glycol is pretreated in a vacuum oven as a reaction solvent; a platinum salt precursor, a nickel salt precursor, a copper salt precursor, an iron salt precursor, and a surfactant polyvinyl pyrrolidone are dissolved in the reaction solvent to obtain a precursor solution A; the precursor solution A is stirred, and a bismuth precursor salt is heated and dissolved in the solvent on a magnetic stirrer to obtain a precursor solution B, which is added to the previous precursor solution A to obtain a reaction solution C. Reaction solution C is placed in a 50mL hydrothermal kettle and reacted at a temperature of 100°C-220°C for 8-24 hours. After the reaction is completed, the resulting sample is washed and dried at 50°C-100°C for 6-12 hours to obtain an ultrathin two-dimensional Pt-based high-entropy alloy nanosheet.

Description

Technical Field

[0001] The present invention belongs to the technical field of new energy materials, and in particular relates to a method for preparing an ultra-thin two-dimensional Pt-based high-entropy alloy nanosheet. Background Art

[0002] Direct formic acid fuel cells (DFAFCs) have garnered significant research attention in recent years. Due to their numerous advantages, including high theoretical open-circuit voltage, high operational safety, and minimal environmental impact, DFAFCs hold enormous potential for application and development. Pt, due to its excellent physicochemical properties, is currently the most widely used DFAFC anode catalyst. However, Pt's low reserves in the Earth's crust, high cost, and susceptibility to poisoning by formic acid oxidation intermediates (particularly CO) lead to loss of activity, hindering its commercialization. Therefore, understanding the reaction mechanism of formic acid oxidation, CO adsorption on the catalyst, and the role of oxygen-containing species that can remove CO will help inform catalyst synthesis. Currently, catalysts used for formic acid oxidation include pure Pt catalysts, binary alloys, and ternary alloys. High-entropy alloys (HEAs) containing five or more elements are currently the focus of research on fuel cell anode catalysts due to their high efficiency and stability, resulting from four core effects: high entropy effect, cocktail effect, lattice distortion effect, and slow diffusion effect. However, there are currently few reports on high-entropy alloys for formic acid oxidation, and the catalytic mechanisms of some formic acid oxidation reactions remain unclear. The thermodynamic instability of high-entropy alloys and the differences in the reduction potentials of multiple elements present in these alloys. Consequently, the application of high-entropy alloys in formic acid oxidation faces the following challenges: how to precisely design and synthesize high-entropy alloys with ideal morphology and atomic coordination environments; the FAOR intermediate CO readily adsorbs on its surface, occupying active sites on the Pt surface and poisoning the catalyst, leading to loss of catalytic activity; and the unclear mechanism of synergistic interactions among the various elements in Pt-based high-entropy alloy catalysts, which restricts catalyst optimization. Summary of the Invention

[0003] Technical issues solved:

[0004] This application addresses the deficiencies in the prior art and solves the technical problems of low Pt reserves in the earth's crust, high prices, and easy poisoning by formic acid oxidation intermediates (especially CO) and loss of activity. It provides a method for preparing ultra-thin two-dimensional Pt-based high-entropy alloy nanosheets, which can structurally overcome the structural stability defects of traditional alloys, achieve synergy between the size, morphology, and multiple elements of the alloy, improve the coordination environment of the Pt atoms in the Pt-based high-entropy alloy, adjust its d-band center, shift its d-band center downward, and weaken the adsorption of CO, thereby inhibiting CO poisoning, thereby achieving the purpose of increasing the activity and stability of the material on FAOR. At the same time, based on the changes in the electrode surface structure and composition, the structure-activity relationship between Pt-based high-entropy alloys and FAOR is revealed, further guiding the synthesis of new and efficient Pt-based high-entropy alloy catalysts.

[0005] Technical solution:

[0006] To achieve the above objectives, this application is implemented through the following technical solutions:

[0007] A method for preparing ultrathin two-dimensional Pt-based high-entropy alloy nanosheets, wherein the synthesis method comprises the following steps:

[0008] Step 1: 10-200 mL of ethylene glycol and / or diethylene glycol is placed in a vacuum oven at 60° C. for pretreatment as a reaction solvent and reducing agent. The pretreatment time is 10-120 min.

[0009] Step 2: Precursor platinum salt, precursor nickel salt, precursor copper salt, precursor iron salt and 0.25 g of surfactant were dissolved in 2 mL of reaction solvent according to a preset molar ratio, and ultrasonicated for 10 s to obtain precursor solution A;

[0010] Step 3: Add 30-50 mL of reaction solvent as a reducing agent to the precursor solution A and stir at a speed of 500-1000 r / min for 5-15 min.

[0011] Step 4: Dissolve 10-1000 mg of the precursor bismuth salt in 3-100 mL of the reaction solvent on a magnetic stirrer at 50-150° C. for 15 minutes to obtain a bismuth precursor solution B. Then, add 1-5 mL of the bismuth precursor solution B to the precursor solution A stirred in step 3 at a rate of 1-10 mL per second to obtain a reaction solution C.

[0012] Step 5: Place the reaction solution C in a 50 mL reactor liner and continue the reaction in a forced air drying oven. After the reaction is completed, cool it naturally to room temperature, wash the obtained sample, and dry it at 50°C-100°C for 6-12 hours to obtain ultra-thin two-dimensional Pt-based high-entropy alloy nanosheets.

[0013] Furthermore, in the precursor solution A, the concentrations of platinum ions, copper ions, nickel ions, and iron ions are 0.5-2 mmol / L, the preset molar ratios of the precursor platinum salt, the precursor nickel salt, the precursor copper salt, and the precursor iron salt are 1:0.5-2:0.5-1.5:0.5-1.5, the concentration of bismuth ions in the precursor solution C is 0.5-2 mol / L, the surfactant is one or a combination of cyclodextrin, PVP, and CTAB, and the concentration of the surfactant in the reaction solvent is 0.05-1 mol / L.

[0014] Furthermore, the molar ratio of platinum ions to bismuth ions, nickel ions, cobalt ions, and iron ions in the reaction solution C is 1:(1-3):(0.5-1.5):(0.5-1.5):(0.5-1.5).

[0015] Furthermore, the precursor platinum salt is platinum acetylacetonate and / or potassium chloroplatinite; the precursor bismuth salt is bismuth neododecanoate and / or anhydrous bismuth nitrate; the precursor nickel salt is nickel acetylacetonate and / or nickel chloride; the precursor copper salt is copper acetylacetonate and / or copper chloride; and the precursor iron salt is iron acetylacetonate and / or iron chloride.

[0016] Furthermore, in the fifth step, the reaction temperature is 100-220° C., and the reaction time is 8-24 hours.

[0017] Furthermore, the reaction temperature in the fourth step is 80°C.

[0018] Furthermore, the vacuum pretreatment time in the first step is 40 minutes.

[0019] The principle behind this method for preparing ultrathin two-dimensional Pt-based high-entropy alloy nanosheets is that diethylene glycol can be used as a solvent and reducing agent, surfactants can induce the formation of sheet structures, and reducing the metal precursor at a lower temperature slows the rate of metal reduction, thereby forming ultrathin two-dimensional sheet structures. Ethylene glycol and / or diethylene glycol, acting as reducing agents, transfer electrons to metal ions, reducing their charge, achieving the co-reduction of multiple metals and forming alloys. This allows for the precise synthesis of two-dimensional or three-dimensional high-entropy alloys with unique morphologies, which are well-suited for formic acid oxidation reactions.

[0020] Beneficial effects:

[0021] This application provides a method for preparing ultra-thin two-dimensional Pt-based high-entropy alloy nanosheets, which has the following beneficial effects compared with the existing technology:

[0022] 1. The alloy prepared by this method is mainly composed of Pt and Bi and 3-6 elements among Ni, Co, Cu, Fe, Mo, and Zn transition elements;

[0023] 2. The ultra-thin two-dimensional Pt-based high-entropy alloy nanosheets prepared by this method can structurally overcome the structural stability defects of traditional alloys, achieve synergistic effects on the size, morphology, and multiple elements of the alloy, improve the coordination environment of the Pt atoms in the Pt-based high-entropy alloy, adjust its d-band center to shift downward, weaken the adsorption of CO, and thus inhibit CO poisoning, thereby achieving the purpose of improving the activity and stability of the material on FAOR. At the same time, based on the changes in the electrode surface structure and composition, the structure-activity relationship between Pt-based high-entropy alloys and FAOR is revealed, further guiding the synthesis of new and efficient Pt-based high-entropy alloy catalysts;

[0024] 3. Based on the changes in electrode surface structure and composition, the structure-activity relationship between Pt-based high-entropy alloys and FAOR is revealed, further guiding the synthesis of new and efficient Pt-based high-entropy alloy catalysts;

[0025] 4. During the experimental test, we measured the mass activity of Pt-based high entropy alloy in 0.5M H2SO4+0.5M HCOOH electrolyte solution by cyclic voltammetry and found it to be 1.93Amg -1 The result measured by commercial Pt / C is 0.51Amg -1 The stability results of 10000s measured by chronoamperometry in 0.5M H2SO4+0.5M HCOOH electrolyte solution showed that the residual activity of Pt-based high entropy alloy after 10000s stability test was 0.2Amg -1 It is much higher than commercial Pt / C (approaching 0); therefore, it can be seen that the Pt-based high-entropy alloy nanosheets we prepared have higher activity and stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The PtBi obtained in Example 1 of this application 1.5 Scanning electron microscopy and transmission electron microscopy images of NiCuFe high entropy alloy nanosheets, where a is PtBi 1.5 Scanning electron microscopy image of NiCuFe high entropy alloy nanosheets, b is PtBi 1.5 Transmission electron microscopy image of NiCuFe high entropy alloy nanosheets;

[0027] Figure 2 The PtBi obtained in Example 1 of the present invention 1.5 Atomic force microscopy image of NiCuFe high-entropy alloy nanosheets; a is the atomic force microscopy image, b is the corresponding roughness image, and C is the corresponding thickness image;

[0028] Figure 3 The PtBi obtained in Example 1 of the present invention 1.5X-ray diffraction pattern of NiCuFe high entropy alloy nanosheets;

[0029] Figure 4 The PtBi obtained in Example 1 of the present invention 1.5 X-ray photoelectron spectroscopy of NiCuFe high-entropy alloy nanosheets;

[0030] Figure 5 The PtBi obtained in Example 1 of the present invention 1.5 Cyclic voltammetry curves of the catalytic activity of NiCuFe high-entropy alloy nanosheets and commercial Pt / C catalysts for formic acid oxidation reaction; the small squares in the figure represent PtBi 1.5 The cyclic voltammetry curve of the catalytic activity of NiCuFe high-entropy alloy nanosheets in formic acid oxidation reaction. The small circles represent the cyclic voltammetry curve of the catalytic activity of commercial Pt / C catalyst in formic acid oxidation reaction.

[0031] Figure 6 The PtBi obtained in Example 1 of the present invention 1.5 Chronoamperometric curves of the catalytic activity of NiCuFe high entropy alloy nanosheets and commercial Pt / C catalysts for formic acid oxidation, where the square line represents PtBi 1.5 The chronoamperometric curve of the catalytic activity of NiCuFe high-entropy alloy nanosheets in formic acid oxidation reaction. The circular line is the chronoamperometric curve of the catalytic activity of commercial Pt / C catalyst in formic acid oxidation reaction. DETAILED DESCRIPTION

[0032] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0033] Example 1:

[0034] An ultra-thin two-dimensional PtBi 1.5 A method for preparing NiCuFe high entropy alloy nanosheets, the method specifically comprising the following steps:

[0035] Step 1: 35 mL of diethylene glycol was placed in a vacuum oven at 60°C for 40 min to obtain the reaction solvent and reducing agent;

[0036] Step 2: Platinum acetylacetonate, nickel acetylacetonate, copper acetylacetonate, iron acetylacetonate and 0.25 g of PVP in a molar ratio of 1:1:1:1 were placed in a 50 mL flask, 2 mL of reaction solvent was added and mixed evenly, and ultrasonicated for 10 seconds to obtain a precursor solution A; wherein,

[0037] In precursor solution A, the concentrations of platinum ions, copper ions, nickel ions, and iron ions are 0.001 mol / L, 0.001 mol / L, 0.001 mol / L, and 0.001 mol / L, respectively;

[0038] Step 3: Add another 30 mL of solvent, diethylene glycol, which also serves as a reducing agent, to the precursor solution A and stir, controlling the speed to 500-1000 r / min and the stirring time to 5-15 min; take 20-100 mg of bismuth neododecanoate and add it to 3 mL of the reaction solvent, dissolve it at 80° C. for 15 minutes to obtain a bismuth precursor solution B, and quickly add the bismuth precursor solution B to the precursor solution A at a rate of 1-10 mL per second to obtain a reaction solution C;

[0039] Step 4: Place the reaction solution C in a hydrothermal kettle, and then place it in a forced air drying oven at a temperature of 100-220°C for 8-24 hours;

[0040] Step 5: After the reaction is completed, the mixture is naturally cooled to room temperature, the reaction solution is washed, and dried at 50°C-100°C for 6-12 hours to obtain a black solid powder, which is a Pt-based high entropy alloy nanosheet.

[0041] The Pt-based high entropy alloy nanosheets obtained above were observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Figure 1 As shown in a, the morphology of the obtained Pt-based high entropy alloy nanosheets is a sheet-like structure. Figure 1 As shown in b, the nanosheet has an obvious ultra-thin sheet structure. Figure 2 As shown, PtBi can be seen by atomic force microscopy 1.5 The NiCuFe high-entropy alloy nanosheet catalyst is an ultra-thin sheet structure with a thickness of about 5 nm. (a) is an atomic force microscope image, (b) is the corresponding roughness image, and (c) is the corresponding thickness image.

[0042] The ultra-thin two-dimensional PtBi 1.5 The NiCuFe high entropy alloy nanosheets were scanned using an X-ray diffractometer. Figure 3 As shown in the figure, all XRD peaks correspond to the combination of standard cards of the five elements Pt, Bi, Ni, Cu, and Fe, proving that all five elements have been reduced. Among them, the diffraction peaks 2θ = 39.9°, 46.4°, 67.7°, and 81.6° can be indexed to the (111), (200), (220), and (311) planes of pure Pt.

[0043] X-ray photoelectron spectroscopy was further used to detect ultrathin two-dimensional PtBi 1.5NiCuFe high entropy alloy nanosheets. From the XPS spectrum, we can see that all five elements are reduced, proving that the ultra-thin nanosheets we prepared are ultra-thin two-dimensional PtBi 1.5 NiCuFe high-entropy alloy nanosheets.

[0044] Formic acid oxidation reaction (FAOR) catalytic activity test:

[0045] (1) Preparation of catalytic electrode

[0046] The ultrathin two-dimensional PtBi prepared above 1.5 NiCuFe high-entropy alloy nanosheets and Vulcan XC-72 carbon (accounting for 40% of the Pt catalyst) were dispersed in 1 mL of water and Nafion solution (V water / V Nafion solution = 1:0.03), and then sonicated for 30 minutes to form a uniform ink. The amount of Pt in the catalyst was controlled based on ICP test data, and the Pt loading was maintained at 35 μg / cm 2 3.3 μL of ink was dropped onto a glassy carbon electrode with an area of ​​3 mm and then dried at room temperature for later use.

[0047] (2) FAOR test

[0048] FAOR measurements were performed in Ar-saturated 0.5 mol / L HSO + 0.5 mol / L HCOOH at a scan rate of 50 mV / s. The long-term stability of the prepared samples was determined by chronoamperometry at 0.23 V (vs. saturated calomel electrode, SCE) in a 0.5 mol / L HSO solution containing 0.5 mol / L HCOOH. For comparison, commercial Pt / C (20 wt% Pt nanoparticles supported on Vulcan XC-72 carbon, Aladdin) was prepared and tested using the same procedures.

[0049] Ultra-thin two-dimensional PtBi obtained in Example 1 1.5 The FAOR performance of NiCuFe high-entropy alloy nanosheets was tested in a three-electrode battery system using a Coster workstation. In the three-electrode system, a saturated calomel electrode and a Pt mesh were used as the reference electrode and counter electrode, respectively.

[0050] Figure 5 The ultra-thin two-dimensional PtBi of Example 1 1.5 Cyclic voltammetry curve of NiCuFe high entropy alloy nanosheets in 0.5mol / L H2SO4 solution containing 0.5mol / L HCOOH, with a potential range of -0.2V to 1V (relative to saturated calomel electrode, SCE) and a scan rate of 50mV / s. The small squares in the figure represent ultra-thin two-dimensional PtBi 1.5The cyclic voltammetry curve of the catalytic activity of NiCuFe high entropy alloy nanosheets in formic acid oxidation reaction, and the small circles represent the cyclic voltammetry curve of the catalytic activity of commercial Pt / C catalyst in formic acid oxidation reaction; Figure 5 It can be concluded that ultra-thin two-dimensional PtBi 1.5 The FAOR activity of NiCuFe high-entropy alloy nanosheets is 1.93 A mg -1 In contrast, the activity of commercial Pt / C is only 0.51Amg -1 .

[0051] Figure 6 The ultra-thin two-dimensional PtBi of Example 1 1.5 Potential change of NiCuFe high entropy alloy nanosheets in 0.5 mol / L H2SO4 solution containing 0.5 mol / L HCOOH at a potential of 0.23 V (relative to saturated calomel electrode, SCE) after 10,000 s, where the square line is an ultra-thin two-dimensional PtBi 1.5 The current curve of NiCuFe high entropy alloy nanosheets as the catalytic active agent for formic acid oxidation reaction, and the circular line is the current curve of commercial Pt / C catalyst as the catalytic active agent for formic acid oxidation reaction. Figure 6 It can be concluded that after 10000s stability test, the ultra-thin two-dimensional PtBi 1.5 The activity of NiCuFe high entropy alloy nanosheets is still maintained at 0.2 A mg -1 In contrast, the activity of commercial Pt / C approaches 0 after 10,000s stability test, indicating that it loses its activity.

[0052] Example 2:

[0053] An ultra-thin two-dimensional PtBi 1.5 A method for preparing NiCuFe high entropy alloy nanosheets, the method specifically comprising the following steps:

[0054] Step 1: 35 mL of diethylene glycol was placed in a vacuum oven at 60°C for 40 min to obtain the reaction solvent and reducing agent;

[0055] Step 2: Platinum acetylacetonate with nickel acetylacetonate, copper acetylacetonate, iron acetylacetonate and 0.25

[0056] 100 g of PVP was placed in a 50 mL flask, 2 mL of reaction solvent was added, and the mixture was mixed evenly. The mixture was ultrasonicated for 10 s to obtain a precursor solution A. The concentrations of platinum ions, copper ions, nickel ions, and iron ions in the precursor solution A were 0.001 mol / L, 0.0015 mol / L, 0.0015 mol / L, and 0.0015 mol / L, respectively. Another 30 mL of diethylene glycol, which also served as a reducing agent, was added to the precursor solution A and stirred at a speed of 500-1000 r / min for 5-15 min.

[0057] Step 3: Add 20-100 mg of bismuth neododecanoate to 3 mL of reaction solvent and dissolve at 80°C for 15 minutes to obtain a bismuth precursor solution B. Rapidly add the bismuth precursor solution B to the precursor solution A at a rate of 1-10 mL per second to obtain a reaction solution C.

[0058] Step 4: Place the reaction solution C in a hydrothermal kettle, and then place it in a forced air drying oven at a temperature of 100-220°C for 8-24 hours;

[0059] Step 5: After the reaction is completed, the mixture is naturally cooled to room temperature, the reaction solution is washed, and dried at 50°C-100°C for 6-12 hours to obtain a black solid powder, which is a Pt-based high entropy alloy nanosheet.

[0060] The Pt-based high entropy alloy nanosheets obtained above were observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Figure 1 As shown in a, the morphology of the obtained Pt-based high entropy alloy nanosheets is a sheet-like structure. Figure 1 As shown in b, the nanosheet has an obvious ultra-thin sheet structure. Figure 2 As shown, PtBi can be seen by atomic force microscopy 1.5 The NiCuFe high entropy alloy nanosheet catalyst has an ultra-thin sheet structure with a thickness of about 5 nm.

[0061] The ultra-thin two-dimensional PtBi 1.5 The NiCuFe high entropy alloy nanosheets were scanned using an X-ray diffractometer. Figure 3 As shown in the figure, all XRD peaks correspond to the combination of standard cards of the five elements Pt, Bi, Ni, Cu, and Fe, proving that all five elements have been reduced. Among them, the diffraction peaks 2θ = 39.9°, 46.4°, 67.7°, and 81.6° can be indexed to the (111), (200), (220), and (311) planes of pure Pt.

[0062] X-ray photoelectron spectroscopy was further used to detect ultrathin two-dimensional PtBi 1.5NiCuFe high entropy alloy nanosheets. From the XPS spectrum, we can see that all five elements are reduced, proving that the ultra-thin nanosheets we prepared are ultra-thin two-dimensional PtBi 1.5 NiCuFe high-entropy alloy nanosheets.

[0063] Example 3:

[0064] An ultra-thin two-dimensional PtBi 1.5 A method for preparing NiCuFe high entropy alloy nanosheets, the method specifically comprising the following steps:

[0065] Step 1: Place 35 mL of diethylene glycol in a vacuum oven for vacuum pretreatment for 40 min to obtain the reaction solvent and reducing agent;

[0066] Step 2: Platinum acetylacetonate, nickel acetylacetonate, copper acetylacetonate, iron acetylacetonate and 0.25 g of PVP in a molar ratio of 1:1.5:1.5:1.5 were placed in a 50 mL flask, 2 mL of reaction solvent was added and mixed evenly, and ultrasonicated for 10 seconds to obtain a precursor solution A; wherein, the concentrations of platinum ions, copper ions, nickel ions and iron ions in the precursor solution A were 0.001 mol / L, 0.0015 mol / L and 0.0025 mol / L, respectively.

[0067] 0.0015mol / L, 0.0015mol / L;

[0068] Step 3: Add another 30 mL of solvent, diethylene glycol, which also serves as a reducing agent, to the precursor solution A and stir, controlling the speed to 500-1000 r / min and the stirring time to 5-15 min; take 20-100 mg of bismuth neododecanoate and add it to 3 mL of the reaction solvent, dissolve it at 80° C. for 15 minutes to obtain a bismuth precursor solution B, and quickly add the bismuth precursor solution B to the precursor solution A at a rate of 1-10 mL per second to obtain a reaction solution C;

[0069] Step 4: Place the reaction solution C in a hydrothermal kettle, and then place it in a forced air drying oven at a temperature of 100-220°C for 8-24 hours;

[0070] Step 5: After the reaction is completed, the mixture is naturally cooled to room temperature, the reaction solution is washed, and dried at 50°C-100°C for 6-12 hours to obtain a black solid powder, which is a Pt-based high entropy alloy nanosheet.

[0071] In summary, the ultra-thin two-dimensional PtBi prepared by the preparation method of the present invention 1.5 NiCuFe high-entropy alloy nanosheets have good catalytic activity for formic acid oxidation reaction, that is, good FAOR activity, and excellent stability. The preparation process is simple, low-cost, and easy to produce on an industrial scale.

[0072] The above description fully discloses the specific embodiments of the present invention. It should be noted that any modifications made by those skilled in the art to the specific embodiments of the present invention do not depart from the scope of the claims. Accordingly, the scope of the claims of the present invention is not limited solely to the foregoing specific embodiments.

Claims

1. A method for preparing ultrathin two-dimensional Pt-based high-entropy alloy nanosheets, characterized in that: The specific steps include: Step 1: 10-200 mL of ethylene glycol and / or diethylene glycol is placed in a vacuum oven at 60° C. for pretreatment as a reaction solvent and reducing agent. The pretreatment time is 10-120 min. Step 2: Precursor platinum salt, precursor nickel salt, precursor copper salt, precursor iron salt and 0.25 g of surfactant were dissolved in 2 mL of reaction solvent according to a preset molar ratio, and ultrasonicated for 10 s to obtain precursor solution A; Step 3: Add 30-50 mL of reaction solvent as a reducing agent to the precursor solution A and stir at a speed of 500-1000 r / min for 5-15 min. Step 4: Dissolve 10-1000 mg of the precursor bismuth salt in 3-100 mL of the reaction solvent under heating at 50-150° C. on a magnetic stirrer for 15 minutes to obtain a bismuth precursor solution B. Then, add 1-5 mL of the bismuth precursor solution B to the precursor solution A stirred in step 3 at a rate of 1-10 mL per second to obtain a reaction solution C. Step 5: Place the reaction solution C in a 50 mL reactor and continue the reaction in a forced air drying oven. After the reaction is completed, cool it naturally to room temperature, wash the sample, and dry it at 50°C-100°C for 6-12 hours to obtain ultrathin two-dimensional Pt-based high-entropy alloy nanosheets. In the precursor solution A, the concentrations of platinum ions, copper ions, nickel ions, and iron ions are 0.5-2 mmol / L, the preset molar ratios of the precursor platinum salt, the precursor nickel salt, the precursor copper salt, and the precursor iron salt are 1:0.5-2:0.5-1.5:0.5-1.5, the surfactant is one or a combination of several of cyclodextrin, PVP, and CTAB, and the concentration of the surfactant in the reaction solvent is 0.05-1 mol / L.

2. The method for preparing the ultra-thin two-dimensional Pt-based high-entropy alloy nanosheet according to claim 1, characterized in that: The molar ratio of platinum ions to bismuth ions, nickel ions, cobalt ions, and iron ions in the reaction solution C is 1:(1-3):(0.5-1.5):(0.5-1.5):(0.5-1.5).

3. The method for preparing the ultra-thin two-dimensional Pt-based high-entropy alloy nanosheet according to claim 1, characterized in that: The precursor platinum salt is platinum acetylacetonate and / or potassium chloroplatinite; the precursor bismuth salt is bismuth neododecanoate and / or anhydrous bismuth nitrate; the precursor nickel salt is nickel acetylacetonate and / or nickel chloride; the precursor copper salt is copper acetylacetonate and / or copper chloride; the precursor iron salt is iron acetylacetonate and / or iron chloride.

4. The method for preparing ultra-thin two-dimensional Pt-based high-entropy alloy nanosheets according to claim 1, characterized in that: In the fifth step, the reaction temperature is 100-220° C., and the reaction time is 8-24 hours.

5. The method for preparing ultrathin two-dimensional Pt-based high-entropy alloy nanosheets according to claim 1, characterized in that: The vacuum pretreatment time in the first step is 40 minutes.

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