Multi-element metal nanosheets, preparation methods and applications thereof

Abstract

The present invention provides a multi-metal nanosheet, a preparation method and application thereof. The multi-metal nanosheet includes rhodium and other metal elements, the other metal elements are selected from precious metal elements and / or copper elements, and the precious metal elements are selected from one or more of the group consisting of palladium, ruthenium and platinum; the thickness of the multi-metal nanosheet is 0.5 to 3 nm, and the weight ratio of rhodium to other metal elements is (1 to 65):1. Compared with nanosheets containing only rhodium elements, the multi-metal nanosheet provided in the present application includes rhodium and other metal elements in the above-mentioned specific ratio, and the other metal elements are selected from precious metal elements and / or copper elements. By adjusting the types and ratios of elements, different reactions can be catalyzed, thereby improving the catalytic activity. The multi-metal nanosheet provided in the present application can catalyze electrochemical reactions and thermochemical reactions, and has a broad application field.

Description

Technical Field

[0001] The present invention relates to the technical field of nanomaterial preparation, and in particular to a multi-element metal nanosheet, a preparation method and application thereof. Background Art

[0002] Nanomaterials, due to their unique physical and chemical properties, have demonstrated significant advantages and enormous application potential in the fields of photochemistry and catalysis. In the field of catalysis, nanomaterials often exhibit one or more of the following characteristics: size effect, surface effect, quantum size effect, and macroscopic quantum tunneling effect, resulting in their catalytic activity and selectivity being significantly superior to those of traditional catalysts. Significant progress has been made in the application of nanocatalysts, particularly in the energy, chemical, and environmental fields. For example, in the oxygen reduction reaction, nanostructured platinum-based catalysts exhibit superior electrochemical performance compared to traditional platinum particles and have been widely studied.

[0003] The morphology control of nanomaterials has a decisive influence on their physical and chemical properties. Fine-tuning the morphology of nanomaterials can significantly improve / change the catalytic activity of nanocatalysts, and research in this field has become a research hotspot. Currently, researchers have successfully prepared nanomaterials with specific morphologies through synthesis methods such as seed growth method and colloidal synthesis method and template technology. These methods can precisely control the size, shape and surface structure of nanomaterials and finely control their physical and chemical properties. For example, by changing the synthesis conditions, researchers can prepare nanomaterials with different crystal surface exposures, and the optical properties or catalytic activities of these materials may vary significantly. In addition, electrochemical methods are also used in the synthesis of nanocatalysts. By regulating electrochemical parameters, precise control of the nanocrystal growth process can be achieved.

[0004] For rhodium-based nanomaterials, morphology control is also crucial for their physical and chemical properties. Precise control of rhodium-based nanomaterials can lead to the development of versatile materials to meet diverse application needs. To this end, a novel method for preparing multi-metal nanosheets is urgently needed. Summary of the Invention

[0005] The main purpose of the present invention is to provide a multi-metal nanosheet, a preparation method and application thereof, so as to solve the problems in the prior art that the morphology of rhodium-based nanomaterials is difficult to control, the utilization rate of metal atoms is low resulting in poor catalytic effect and a relatively single application field.

[0006] In order to achieve the above-mentioned objectives, the present invention provides, on the one hand, a multi-metal nanosheet, which includes rhodium and other metal elements, wherein the other metal elements are selected from precious metal elements and / or copper elements, and the precious metal elements are selected from one or more of the group consisting of palladium, ruthenium and platinum; the thickness of the multi-metal nanosheet is 0.5 to 3 nm, and the weight ratio of rhodium to other metal elements is (1 to 65):1.

[0007] Furthermore, the other metal elements are precious metal elements, and the multi-metal nanosheets include rhodium elements and alloys formed by rhodium elements and precious metal elements; or, the other metal elements are precious metal elements and copper elements, and the multi-metal nanosheets include rhodium elements, alloys formed by rhodium elements and precious metal elements, and alloys formed by rhodium elements and copper elements; or the other metal elements are copper elements, and the multi-metal nanosheets include rhodium elements and alloys formed by rhodium elements and copper elements.

[0008] Further, the multi-metal nanosheet includes rhodium and palladium, and the weight ratio of rhodium to palladium is (2-50):1; or, the multi-metal nanosheet includes rhodium and platinum, and the weight ratio of rhodium to platinum is (5-20):1; or, the multi-metal nanosheet includes rhodium, palladium and copper, and the ratio of the weight of rhodium to the sum of the weights of palladium and copper is (2-60):1, and the weight ratio of palladium to copper is (3-20):1; or, the multi-metal nanosheet includes rhodium, platinum and copper, and the ratio of the weight of rhodium to the sum of the weights of platinum and copper is (2-65):1, and the weight ratio of platinum to copper is (3-25):1.

[0009] Furthermore, the specific surface area of ​​the multi-metal nanosheets is 820 to 2000 cm 2 / g.

[0010] In order to achieve the above-mentioned purpose, another aspect of the present invention also provides a preparation method of the above-mentioned multi-metal nanosheets provided by the present application, which preparation method includes: step S1, mixing a rhodium source, a first metal carbonyl compound and a first organic solvent to obtain a first mixed system; step S2, allowing the first mixed system to undergo a first reaction under heating conditions to obtain a first product system containing rhodium nanosheets, and obtaining rhodium nanosheets after a first solid-liquid separation; step S3, mixing rhodium nanosheets, other metal sources, a second metal carbonyl compound and a second organic solvent to obtain a second mixed system; wherein the other metal sources include precious metal sources and / or copper sources, and the precious metal sources are compounds containing precious metal elements; the weight ratio of the rhodium element in the rhodium nanosheets to the other metal elements in the other metal sources is (1 to 65):1; step S4, allowing the second mixed system to undergo a second reaction under heating conditions to obtain a second product system, and obtaining the multi-metal nanosheets after a second solid-liquid separation and drying treatment.

[0011] Furthermore, in the second mixed system, the mass concentration of rhodium nanosheets is 0.05-0.4 mg / mL.

[0012] Furthermore, in the second mixed system, the molar concentration of the other metal sources is 0.01 to 3 μmol / mL.

[0013] Furthermore, in the first mixed system, the molar concentration of the rhodium source is 0.1 to 5 μmol / mL.

[0014] Furthermore, the molar ratio of the rhodium source to the first carbonyl compound is 1:(1-6).

[0015] Further, the rhodium source is selected from one or more of the group consisting of rhodium chloride, rhodium chloride trihydrate, rhodium bromide, rhodium bromide dihydrate and rhodium acetylacetonate.

[0016] Furthermore, the first metal carbonyl compound is selected from one or more of the group consisting of molybdenum hexacarbonyl, iron pentacarbonyl and tungsten hexacarbonyl.

[0017] Furthermore, the first organic solvent is selected from one or more of the group consisting of oleylamine, octadecene, oleic acid and toluene.

[0018] Furthermore, the temperature of the first reaction is 140-200° C., and the time is 2-8 hours.

[0019] Furthermore, the first reaction is carried out in a protective gas and an optional reducing gas, preferably the protective gas is selected from nitrogen and / or argon, and the reducing gas is carbon monoxide.

[0020] Furthermore, step S2 further includes: after the first reaction is completed, cooling to room temperature at a cooling rate of 10 to 40°C / min, and obtaining rhodium nanosheets after a first solid-liquid separation.

[0021] Furthermore, the first solid-liquid separation is performed by centrifugation, preferably at a centrifugal speed of 1500 to 2500 r / min and a time of 1 to 3 minutes.

[0022] Furthermore, the molar ratio of the other metal source to the second carbonyl compound is 1:(1-11).

[0023] Furthermore, the precious metal source is selected from one or more of the group consisting of palladium acetylacetonate, palladium chloride, ruthenium acetylacetonate, ruthenium chloride, platinum acetylacetonate and chloroplatinic acid; and / or one or more of the group consisting of hydrates of palladium chloride, ruthenium chloride and chloroplatinic acid.

[0024] Furthermore, the copper source is selected from copper acetylacetonate and / or copper chloride.

[0025] Furthermore, the second metal carbonyl compound is selected from one or more of the group consisting of molybdenum hexacarbonyl, iron pentacarbonyl and tungsten hexacarbonyl.

[0026] Furthermore, the second organic solvent is selected from oleylamine and / or oleic acid.

[0027] Furthermore, the second reaction is carried out in a mixed atmosphere of protective gas and carbon monoxide. Preferably, in the second reaction, the volume ratio of carbon monoxide to protective gas is (0.5-50):1; preferably, the protective gas in the second reaction is selected from nitrogen and / or argon.

[0028] Furthermore, the temperature of the second reaction is 110 to 190° C., preferably 120 to 140° C., and the time is 1 to 6 hours, preferably 2 to 4 hours.

[0029] Furthermore, step S4 further includes: washing to remove impurities after the second solid-liquid separation, and then drying to obtain multi-element metal nanosheets.

[0030] Furthermore, washing is performed with a mixture of n-hexane and ethanol, preferably three times, with washing speeds of 3000-4000 r / min, 2400-3600 r / min and 1800-2800 r / min, respectively, and the time for each washing is independently 1-3 minutes.

[0031] Furthermore, the second solid-liquid separation is performed by centrifugation, preferably at a centrifugal speed of 2000-4000 r / min and a time of 1-3 min.

[0032] Furthermore, the drying temperature is 70-90° C. and the drying time is 12-24 hours.

[0033] Furthermore, step S4 also includes: after the second heat treatment is completed, the temperature of the second product system is reduced to 80°C at a cooling rate of 10-40°C / min, a second solid-liquid separation is performed using n-hexane, and multi-metal nanosheets are obtained after drying.

[0034] Another aspect of the present invention provides an application of the above-mentioned multi-metal nanosheets provided in this application in water electrolysis, CO2 electroreduction reaction, oxygen reduction reaction, formic acid oxidation reaction, methanol oxidation reaction, CO oxidation reaction, NOx oxidation reaction, and hydrogenation catalytic reaction.

[0035] By applying the technical solution of the present invention, compared to nanosheets containing only rhodium elements, the above-mentioned multi-metal nanosheets provided by this application include the above-mentioned specific ratio of rhodium elements (Rh) and other metal elements, and the other metal elements are selected from precious metal elements (one or more of Pd, Ru and Pt) and / or copper (Cu). By adjusting the type and ratio of elements, different reactions can be catalyzed, thereby improving the catalytic activity. Compared with other ranges, limiting the thickness of the multi-metal nanosheet to the above range can better exert the catalytic effect of the multi-metal nanosheet, thereby facilitating the catalysis of electrochemical reactions (such as electrolysis of water, electroreduction of CO2, oxygen reduction reaction, formic acid oxidation reaction, methanol oxidation reaction) and thermochemical reactions (such as CO oxidation reaction, NOx oxidation reaction, hydrogenation catalytic reaction of organic compounds such as phenol and anthracene), thereby broadening its application field. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0037] Figure 1 The transmission electron microscope image (TEM image) of the multi-element metal nanosheet prepared in Example 1 of the present application is shown;

[0038] Figure 2 The element distribution diagram of the multi-metal nanosheet prepared in Example 1 of the present application is shown. DETAILED DESCRIPTION

[0039] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the embodiments.

[0040] As described in the background art, existing rhodium-based nanomaterials have problems such as difficult to control morphology, low metal atom utilization rate resulting in poor catalytic effect, and relatively limited application areas. In order to solve the above technical problems, the first aspect of the present application provides a multi-metal nanosheet, which includes rhodium and other metal elements, the other metal elements are selected from precious metal elements and / or copper elements, and the precious metal elements are selected from one or more of the group consisting of palladium, ruthenium and platinum; the thickness of the multi-metal nanosheet is 0.5 to 3 nm, and the weight ratio of rhodium to other metal elements is (1 to 65):1.

[0041] Compared to nanosheets containing only rhodium elements, the above-mentioned multi-metal nanosheets provided in the present application include rhodium elements (Rh) and other metal elements in the above-mentioned specific ratio, and the other metal elements are selected from precious metal elements (one or more of Pd, Ru and Pt) and / or copper (Cu). By adjusting the type and ratio of elements, different reactions can be catalyzed, thereby improving the catalytic activity. Compared with other ranges, limiting the thickness of the multi-metal nanosheet to the above range can better exert the catalytic effect of the multi-metal nanosheet, thereby facilitating the catalysis of electrochemical reactions (such as electrolysis of water, electroreduction of CO2, oxygen reduction reaction, formic acid oxidation reaction, methanol oxidation reaction) and thermochemical reactions (such as CO oxidation reaction, NOx oxidation reaction, hydrogenation catalytic reaction of organic compounds such as phenol and anthracene), thereby broadening its application field.

[0042] In a preferred embodiment, the other metal elements are noble metal elements, and the multinary metal nanosheets include rhodium element and an alloy formed by rhodium element and noble metal element; or, the other metal elements are noble metal elements and copper element, and the multinary metal nanosheets include rhodium element, an alloy formed by rhodium element and noble metal element, and an alloy formed by rhodium element and copper element; or the other metal element is copper element, and the multinary metal nanosheets include rhodium element and an alloy formed by rhodium element and copper element. Compared with metal rhodium nanosheets, the multinary metal nanosheets provided in this application include the above-mentioned rhodium element and an alloy formed by rhodium element and noble metal element and / or copper element, which is conducive to regulating the adsorption characteristics of different reactants and intermediates on the surface of the multinary metal nanosheets, thereby specifically improving the catalytic activity and expanding the application range of rhodium-based catalysts.

[0043] In a preferred embodiment, the multi-metal nanosheets include rhodium and palladium, with a weight ratio of rhodium to palladium of (2-50):1; or the multi-metal nanosheets include rhodium and platinum, with a weight ratio of rhodium to platinum of (5-20):1. Compared to other ranges, limiting the above elements and their weight ratios within the above ranges facilitates full alloying of Rh with the other metal elements, improves metal atom utilization, and thus enhances catalytic activity, thereby broadening its application areas.

[0044] In a preferred embodiment, the multi-element metal nanosheets include rhodium, palladium, and copper, with the ratio of the weight of rhodium to the sum of the weights of palladium and copper being (2-60):1, and the weight ratio of palladium to copper being (3-20):1; or, the multi-element metal nanosheets include rhodium, platinum, and copper, with the ratio of the weight of rhodium to the sum of the weights of platinum and copper being (2-65):1, and the weight ratio of platinum to copper being (3-25):1. Compared to other ranges, limiting the above elements and their weight ratios within the above ranges facilitates full alloying of Rh with the other metal elements, improves metal atom utilization, and thus improves catalytic activity, thereby broadening its application areas.

[0045] In order to further improve the catalytic activity and catalytic effect of the multi-metal nanosheets, preferably, the specific surface area of ​​the multi-metal nanosheets is 820 to 2000 cm 2 / g.

[0046] The second aspect of the present application provides a preparation method of the above-mentioned multinary metal nanosheets provided by the present application, and the preparation method includes: step S1, mixing a rhodium source, a first metal carbonyl compound and a first organic solvent to obtain a first mixed system; step S2, allowing the first mixed system to undergo a first reaction under heating conditions to obtain a first product system containing rhodium nanosheets, and obtaining rhodium nanosheets after a first solid-liquid separation; step S3, mixing rhodium nanosheets, other metal sources, a second metal carbonyl compound and a second organic solvent to obtain a second mixed system; wherein the other metal sources include precious metal sources and / or copper sources, and the precious metal sources are compounds containing precious metal elements; the weight ratio of the rhodium element in the rhodium nanosheets to the other metal elements in the other metal sources is (1 to 65):1; step S4, allowing the second mixed system to undergo a second reaction under heating conditions, and obtaining the multinary metal nanosheets after a second solid-liquid separation and drying treatment.

[0047] A rhodium source, a first metal carbonyl compound, and a first organic solvent are mixed and subjected to a first reaction. During this process, the first metal carbonyl compound acts as a surface capping agent to control the micromorphology of the rhodium nanosheets, resulting in sheet-like rhodium nanosheets after the first reaction. The rhodium nanosheets, another metal source, a second metal carbonyl compound, and a second organic solvent are mixed and subjected to a second reaction. This allows the other metal source to react with the surface of the rhodium nanosheets and grow to form an alloy of a noble metal source and / or a copper source with rhodium, thereby obtaining multi-metal nanosheets with a high catalytic reaction. Furthermore, during the second reaction, the second metal carbonyl compound acts as a surface capping agent to control the micromorphology of the multi-metal nanosheets, forming a sheet-like two-dimensional material containing rhodium and the aforementioned specific types of other metal elements. Furthermore, the first metal carbonyl compound and the second metal carbonyl compound can also exert a reducing effect, reducing the high-valent noble metal in the noble metal source to a low-valent state, thereby forming an alloy with rhodium.

[0048] Compared with other ranges, limiting the weight ratio of rhodium elements in rhodium nanosheets to other metal elements in other metal sources within the above range is conducive to better exerting the catalytic effect of the multi-metal nanosheets, thereby facilitating the catalysis of electrochemical reactions (such as water electrolysis, CO2 electroreduction reaction, oxygen reduction reaction, formic acid oxidation reaction, methanol oxidation reaction) and thermochemical reactions (such as CO oxidation reaction, NOx oxidation reaction, hydrogenation catalytic reaction), thereby broadening its application fields.

[0049] In a preferred embodiment, the mass concentration of the rhodium nanosheets in the second mixed system is 0.05 to 0.4 mg / mL. The mass concentration of the rhodium nanosheets includes, but is not limited to, the above range, and limiting it to the above range facilitates alloying with other metal elements to form multi-metal nanosheets.

[0050] In order to improve the dispersibility of other metal sources and further increase the generation rate of multi-element metal nanosheets, preferably, in the second mixed system, the molar concentration of other metal sources is 0.01 to 3 μmol / mL.

[0051] In a preferred embodiment, the molar concentration of the rhodium source in the first mixed system is 0.1 to 5 μmol / mL. The molar concentration of the rhodium source includes, but is not limited to, the aforementioned range. Limiting the molar concentration of the rhodium source within this range is beneficial for increasing the yield of rhodium nanosheets, facilitating the formation of ultrathin rhodium nanosheets, and inhibiting agglomeration of the rhodium nanosheets, thereby facilitating the subsequent second reaction.

[0052] In a preferred embodiment, the molar ratio of the rhodium source to the first carbonyl compound is 1:(1-6). The molar ratio of the rhodium source to the first carbonyl compound includes, but is not limited to, the above range. Limiting the molar ratio of the rhodium source to the first carbonyl compound within the above range is beneficial for improving the utilization rate of the raw materials and for better controlling the formation of flaky rhodium nanosheets.

[0053] In order to form sheet-like rhodium nanosheets, preferably, the rhodium source includes, but is not limited to, one or more of the group consisting of rhodium chloride, rhodium chloride trihydrate, rhodium bromide, rhodium bromide dihydrate and rhodium acetylacetonate.

[0054] In order to better play the role of the surface capping agent and better regulate the micromorphology of the rhodium nanosheets, preferably, the first metal carbonyl compound includes but is not limited to one or more of the group consisting of molybdenum hexacarbonyl, iron pentacarbonyl and tungsten hexacarbonyl.

[0055] In a preferred embodiment, the first organic solvent includes, but is not limited to, one or more of the group consisting of oleylamine, octadecene, oleic acid, and toluene. Compared to other types, the use of these first organic solvents improves the dispersibility and compatibility of the rhodium source and the first carbonyl compound, thereby increasing the yield of the rhodium nanosheets.

[0056] In a preferred embodiment, the temperature of the first reaction is 140-200°C, and the reaction time is 2-8 hours. The temperature and time of the first reaction include, but are not limited to, the aforementioned ranges. Limiting the reaction time to these ranges helps improve the yield of the rhodium nanosheets and facilitates the subsequent second reaction. Furthermore, controlling the thickness of the rhodium nanosheets within an appropriate range facilitates the subsequent formation of multi-metal nanosheets of a specific thickness.

[0057] In a preferred embodiment, the first reaction is carried out in a protective gas and an optional reducing gas, preferably the protective gas is selected from nitrogen and / or argon, and the reducing gas is carbon monoxide. The first carbonyl compound can also provide a partial reducing effect. At the same time, in order to carry out the first reaction process in a reducing atmosphere, carbon monoxide is preferably introduced.

[0058] In a preferred embodiment, step S2 further comprises: after the first reaction is completed, cooling the temperature to room temperature at a rate of 10-40°C / min, followed by a first solid-liquid separation to obtain rhodium nanosheets. This cooling process, followed by the first solid-liquid separation, can improve the yield and purity of the rhodium nanosheets.

[0059] Common solid-liquid separation methods can be used in this application. In a preferred embodiment, the first solid-liquid separation is performed by centrifugation, preferably at a centrifugal speed of 1500-2500 r / min and a time of 1-3 minutes. Limiting the centrifugal speed and time within the above ranges is beneficial for improving the separation efficiency of the rhodium nanosheets, thereby increasing their yield, compared to other ranges.

[0060] In a preferred embodiment, the molar ratio of the other metal source to the second carbonyl compound is 1:(1-11). The molar ratio of the other metal source to the second carbonyl compound includes, but is not limited to, the above range. Limiting the molar ratio within the above range is beneficial to improving the utilization rate of raw materials, promoting the formation of alloy phases, and suppressing the formation of impurity phases, thereby improving the production rate and purity of multi-element nanometal sheets.

[0061] In a preferred embodiment, the noble metal source includes, but is not limited to, one or more of the group consisting of palladium acetylacetonate, palladium chloride, ruthenium acetylacetonate, ruthenium chloride, platinum acetylacetonate, and chloroplatinic acid; and / or one or more of the group consisting of hydrates of palladium chloride, ruthenium chloride, and chloroplatinic acid. Compared to other types, the use of the aforementioned noble metal sources improves their dispersibility in the second organic solvent, thereby facilitating the second reaction.

[0062] In a preferred embodiment, the copper source includes but is not limited to copper acetylacetonate and / or copper chloride. Compared with other types, the use of the above types of noble metal sources is conducive to improving their dispersibility in the second organic solvent, thereby facilitating the second reaction.

[0063] In a preferred embodiment, the second metal carbonyl compound includes, but is not limited to, one or more of the group consisting of molybdenum hexacarbonyl, iron pentacarbonyl, and tungsten hexacarbonyl. Compared to other types, the use of these second metal carbonyl compounds facilitates better surface capping and control of the micromorphology of the rhodium nanosheets.

[0064] In order to improve the dispersibility and compatibility of the noble metal source and the second metal carbonyl compound, preferably, the second organic solvent includes but is not limited to oleylamine and / or oleic acid.

[0065] In a preferred embodiment, the second reaction is conducted in a mixed atmosphere of a protective gas and carbon monoxide, preferably nitrogen and / or argon. Conducting the second reaction in this mixed atmosphere advantageously provides a reducing atmosphere for the reaction system, thereby facilitating the alloying growth of the other metal sources with the rhodium nanosheets, inhibiting the formation of nanostructures such as particles, and thereby increasing the yield and purity of the sheet-like multi-metal nanosheets.

[0066] In order to further effectively control the two-dimensional morphology of the multi-element metal nanosheets, preferably, in the second reaction, the volume ratio of carbon monoxide to the protective gas is (0.5-50):1.

[0067] In a preferred embodiment, the temperature of the second reaction is 110-190° C., and the time is 1-6 hours. The temperature and time of the second reaction include, but are not limited to, the above ranges. Limiting them to the above ranges is beneficial to improving the efficiency of the second reaction, thereby improving the yield of the multinary metal nanosheets, and also facilitating the formation of multinary metal nanosheets with uniform thickness.

[0068] In order to further improve the efficiency of the second reaction and increase the yield and thickness uniformity of the multi-element metal nanosheets, preferably, the temperature of the second reaction is 120-140° C. and the time is 2-4 hours.

[0069] In a preferred embodiment, step S4 further comprises: washing to remove impurities after the second solid-liquid separation, followed by drying to obtain the multinary metal nanosheets. The washing treatment facilitates the removal of other impurities, and the drying treatment facilitates the removal of the solvent, thereby obtaining multinary metal nanosheets of higher purity.

[0070] In order to improve the impurity removal rate and thus improve the purity of the multi-element metal nanosheets, preferably, a mixture of n-hexane and ethanol is used for washing.

[0071] In order to improve the impurity removal rate and thus improve the purity of the multi-metal nanosheets, preferably, the washing times are 3 times, the washing speeds are 3000-4000 r / min, 2400-3600 r / min and 1800-2800 r / min respectively, and the time of each washing is independently 1-3 minutes.

[0072] The second solid-liquid separation in this application can be performed using centrifugation methods commonly used in the art. In a preferred embodiment, the second solid-liquid separation is performed using centrifugation, preferably at a centrifugal speed of 2000-4000 r / min and a time of 1-3 minutes. Limiting the centrifugal speed and time within the above ranges is beneficial for improving the separation efficiency of the multi-element metal nanosheets, thereby improving their yield and purity, compared to other ranges.

[0073] In a preferred embodiment, the drying temperature is 70-90°C and the drying time is 12-24 hours. The drying temperature and time include, but are not limited to, the above ranges. Limiting them to the above ranges is beneficial to improving the removal rate of residual solvent, thereby reducing the amount of solvent in the multi-metal nanosheets.

[0074] In a preferred embodiment, step S4 further comprises: after the second heat treatment, cooling the second product system to 80°C at a cooling rate of 10-40°C / min, performing a second solid-liquid separation using n-hexane, and drying to obtain the multinary metal nanosheets. Compared to performing the second solid-liquid separation at room temperature, performing the second solid-liquid separation on the second product system while it is hot improves the separation efficiency of the multinary metal nanosheets, thereby increasing their yield and purity.

[0075] The third aspect of the present application also provides an application of the above-mentioned multi-metal nanosheets provided by the present application in water electrolysis, CO2 electroreduction reaction, oxygen reduction reaction, formic acid oxidation reaction, methanol oxidation reaction, CO oxidation reaction, NOx oxidation reaction, and hydrogenation catalytic reaction. The above-mentioned multi-metal nanosheets provided by the present application have a wide range of applications in electrochemical reactions and thermochemical reactions, especially in water electrolysis, CO2 electroreduction reaction, oxygen reduction reaction, formic acid oxidation reaction, methanol oxidation reaction, CO oxidation reaction, NOx oxidation reaction, and hydrogenation catalytic reaction. The catalytic activity of the above-mentioned multi-metal nanosheets can be exerted, the catalytic efficiency can be improved, and thus the reaction efficiency can be improved.

[0076] The present application is further described in detail below with reference to specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in this application.

[0077] (1) Preparation Example

[0078] Example 1

[0079] (1) 8.2 mg and 39.2 μmol of rhodium chloride were added to 10 mL of oleylamine, and ultrasonic dispersion was performed until the rhodium chloride was completely dissolved to form a golden solution. Then, 55 mg and 208.33 μmol of molybdenum hexacarbonyl were added under magnetic stirring, and ultrasonic dispersion was performed (the temperature was controlled below 10°C) to form a uniform solution, i.e., the first mixed system; then, argon gas was passed through the reaction vessel for 10 minutes, the reaction vessel was sealed, and the reaction was transferred to an oil bath at 160°C for the first reaction, and the reaction was carried out for 5 hours. Then, the temperature was lowered to 25°C at a rate of 25°C / min, and the mixture was centrifuged at 2000 r / min for 2 minutes to obtain rhodium nanosheets;

[0080] (2) 3.6 mg of rhodium nanosheets prepared in step (1) were added to 10 mL of oleylamine / oleic acid mixed solvent (the volume ratio of oleylamine to oleic acid was 19:1), and low-temperature ultrasonic dispersion (≤10°C) was performed to form a black solution. Then, 3.1 mg and 10.17 μmol of palladium acetylacetonate were added under magnetic stirring. After using a shaking table, 28 mg and 106.06 μmol of molybdenum hexacarbonyl were added and ultrasonic dispersion was performed to form a uniform solution, i.e., the second mixed system. Subsequently, argon gas was passed through the reaction vessel for 10 min, and carbon monoxide (CO) gas (5 sccm) was passed through the reaction vessel for 5 min. The reaction vessel was sealed and transferred to an oil bath at 125°C for a second reaction. After reacting for 3 h, the temperature was lowered to 80°C, 10 mL of n-hexane was added and the mixture was centrifuged. The solid phase product was washed 3 times with a n-hexane / ethanol mixed solution and dried in a vacuum oven at 80°C for 18 h to obtain rhodium palladium (Rh-Pd) metal nanosheets.

[0081] like Figure 1 As shown in Figure 2, the RhPd metal nanosheets have a sheet-like microstructure and a thickness of 1.1 nm. Figure 2 As shown, the Rh element and the Pd element are uniformly dispersed in the rhodium-palladium metal nanosheets prepared in Example 1, which indicates that a Rh-Pd alloy is formed, and the weight ratio of the Rh element to the Pd element is 5:1.

[0082] Example 2

[0083] (1) 12.3 mg, 58.8 μmol of rhodium chloride was added to 15 mL of oleylamine, and ultrasonic dispersion was performed until the rhodium chloride was completely dissolved to form a golden solution. Then, 84 mg, 318.18 μmol of molybdenum hexacarbonyl was added under magnetic stirring, and ultrasonic dispersion was performed (temperature was controlled below 10°C) to form a uniform solution, i.e., the first mixed system; then, argon was passed through the reaction vessel for 10 minutes, the reaction vessel was sealed, and the reaction was transferred to an oil bath at 160°C for the first reaction, and the reaction was carried out for 5 hours. Then, the temperature was lowered to 25°C at a rate of 25°C / min, and the mixture was centrifuged at 2000 r / min for 2 minutes to obtain rhodium nanosheets;

[0084] (2) 6 mg of rhodium nanosheets prepared in step (1) were added to 15 mL of oleylamine / oleic acid mixed solvent (the volume ratio of oleylamine to oleic acid was 19:1), and after low-temperature ultrasonic dispersion (≤10°C) to form a black solution, 3.1 mg, 10.17 μmol of acetylacetonate palladium and 1.9 mg, 4.83 μmol of acetylacetonate platinum were added under magnetic stirring. After using a shaking table, 42 mg, 159.09 μmol of hexacarbonyl molybdenum were added and ultrasonic dispersion was performed to form a uniform solution. , i.e. the second mixed system; subsequently, argon gas was passed into the reaction vessel for 10 minutes, carbon monoxide (CO) gas (5 sccm) was passed into the reaction vessel for 5 minutes, the reaction vessel was sealed, and transferred to an oil bath at 130°C for a second reaction. After the reaction for 3 hours, the temperature was lowered to 80°C, 10 mL of n-hexane was added and the mixture was centrifuged. The solid phase product was washed three times with a n-hexane / ethanol mixed solution and dried in a vacuum oven at 80°C for 18 hours to obtain rhodium palladium platinum (Rh-Pd-Pt) metal nanosheets.

[0085] Example 3

[0086] The difference from Example 1 is that in the second mixed system, the mass concentration of rhodium nanosheets is 0.05 mg / mL, and the molar concentration of palladium acetylacetonate is 0.01 μmol / mL.

[0087] Example 4

[0088] The difference from Example 1 is that in the second mixed system, the mass concentration of rhodium nanosheets is 0.4 mg / mL, and the molar concentration of palladium acetylacetonate is 3 μmol / mL.

[0089] Example 5

[0090] The difference from Example 1 is: the addition amount of rhodium chloride is changed so that the molar concentration of rhodium chloride in the first mixed system is 0.1 μmol / mL.

[0091] Example 6

[0092] The difference from Example 1 is: the addition of rhodium chloride is changed so that the molar concentration of rhodium chloride in the first mixed system is 5 μmol / mL.

[0093] Example 7

[0094] The difference from Example 1 is: the addition amount of rhodium chloride is changed so that the molar concentration of rhodium chloride in the first mixed system is 8 μmol / mL.

[0095] Example 8

[0096] The difference from Example 1 is that in the second mixed system, the amount of molybdenum hexacarbonyl added is 10.3 mg, and the molar ratio of palladium acetylacetonate to molybdenum hexacarbonyl is 1:1.

[0097] Example 9

[0098] The difference from Example 1 is that in the second mixed system, the amount of molybdenum hexacarbonyl added is 103.5 mg, and the molar ratio of palladium acetylacetonate to molybdenum hexacarbonyl is 1:10.

[0099] Example 10

[0100] The difference from Example 1 is that in the second mixed system, the amount of molybdenum hexacarbonyl added is 5.2 mg, and the molar ratio of palladium acetylacetonate to molybdenum hexacarbonyl is 1:0.5.

[0101] Example 11

[0102] The difference from Example 1 is that the temperature of the first reaction is 140° C. and the time is 8 hours.

[0103] Example 12

[0104] The difference from Example 1 is that the temperature of the first reaction is 200° C. and the time is 2 h.

[0105] Example 13

[0106] The difference from Example 1 is that the temperature of the first reaction is 130° C. and the time is 1.5 h.

[0107] Example 14

[0108] The difference from Example 1 is that in the first mixed system, the amount of molybdenum hexacarbonyl added is 2.7 mg, and the molar ratio of rhodium chloride to molybdenum hexacarbonyl is 1:1.

[0109] Example 15

[0110] The difference from Example 1 is that in the first mixed system, the amount of molybdenum hexacarbonyl added is 27.0 mg, and the molar ratio of rhodium chloride to molybdenum hexacarbonyl is 1:10.

[0111] Example 16

[0112] The difference from Example 1 is that in the first mixed system, the amount of molybdenum hexacarbonyl added is 1.4 mg, and the molar ratio of rhodium chloride to molybdenum hexacarbonyl is 1:0.5.

[0113] Example 17

[0114] The difference from Example 1 is that the temperature of the second reaction is 110° C. and the time is 6 hours.

[0115] Example 18

[0116] The difference from Example 1 is that the temperature of the second reaction is 190° C. and the time is 1 hour.

[0117] Example 19

[0118] The difference from Example 1 is that the temperature of the second reaction is 120° C. and the time is 4 hours.

[0119] Example 20

[0120] The difference from Example 1 is that the temperature of the second reaction is 140° C. and the time is 2 h.

[0121] Example 21

[0122] The difference from Example 1 is that the temperature of the second reaction is 200° C. and the time is 0.5 h.

[0123] Example 22

[0124] The difference from Example 1 is that 1.7 mg of copper chloride is further added in step (2) to obtain rhodium-palladium-copper (Rh-Pd-Cu) metal nanosheets.

[0125] Example 23

[0126] The difference from Example 1 is that 1.7 mg of copper chloride is used to replace 3.1 mg of palladium acetylacetonate in step (2) to obtain rhodium-copper (Rh-Cu) metal nanosheets.

[0127] Comparative Example 1

[0128] The difference from Example 1 is that in the second mixed system, the mass concentration of rhodium nanosheets is 0.02 mg / mL, and the molar concentration of palladium acetylacetonate is 5 μmol / mL.

[0129] Comparative Example 2

[0130] The difference from Example 2 is that in the second mixed system, the mass concentration of rhodium nanosheets is 2 mg / mL, and the molar concentration of palladium acetylacetonate is 0.005 μmol / mL.

[0131] Comparative Example 3

[0132] The difference from Example 1 is that: 8.2 mg of rhodium chloride, 83 mg of molybdenum hexacarbonyl, and 3.1 mg of palladium acetylacetonate are dispersed in 20 mL of a mixed solvent of oleylamine and oleic acid to form a precursor solution; a one-step reaction is carried out in an oil bath at 125° C., and after the reaction is completed, the temperature is lowered to 80° C., 10 mL of n-hexane is added and centrifuged, and the solid phase product is washed three times with a n-hexane / ethanol mixed solution and dried in a vacuum oven at 80° C. for 18 h to obtain rhodium palladium (Rh-Pd) metal nanosheets.

[0133] Comparative Example 4

[0134] The difference from Example 22 is that in the second mixed system, the mass concentration of rhodium nanosheets is 0.04 mg / mL, and the molar concentration of copper chloride is 7 μmol / mL.

[0135] Comparative Example 5

[0136] The difference from Example 23 is that in the second mixed system, the mass concentration of rhodium nanosheets is 1 mg / mL, and the molar concentration of copper chloride is 0.004 μmol / mL.

[0137] The thickness and specific surface area test results of the multi-element metal nanosheets prepared in all the above examples and comparative examples of the present application are shown in Table 1. The thickness is measured by atomic force microscopy (AFM), and the specific surface area is measured by nitrogen isothermal adsorption-desorption curve method.

[0138] Table 1

[0139]

[0140] (2) Application Examples

[0141] (1) CO2 electroreduction reaction

[0142] Application Examples 1, 3 to 21

[0143] A three-electrode system was used for CO2 electroreduction, wherein 1 mol / L KOH was used as the electrolyte, Hg / HgO was used as the reference electrode, and a platinum wire was used as the counter electrode. The diaphragm included an anode catalyst layer, an anion exchange membrane layer, and a cathode catalyst layer stacked in sequence. The rhodium palladium (Rh-Pd) metal nanosheets prepared in Preparation Examples 1, 3 to 21 were used as the material for the cathode catalyst layer, the material for the anode catalyst layer was platinum wire, the thickness of the AEM membrane layer was 60 μm, and the thickness of the cathode catalyst layer was 500 nm.

[0144] Application Example 22

[0145] The difference from Application Example 1 is that the rhodium palladium copper (Rh—Pd—Cu) metal nanosheets prepared in Preparation Example 22 are used as the material for the cathode catalyst layer.

[0146] Application Example 23

[0147] The difference from Application Example 1 is that the rhodium-copper (Rh-Cu) metal nanosheets prepared in Preparation Example 22 are used as the material for the cathode catalyst layer.

[0148] Comparative Application Example 1

[0149] The difference from Application Example 1 is that the rhodium-palladium (Rh—Pd) metal nanosheets prepared in Preparation Comparative Example 1 are used as the material for the cathode catalyst layer.

[0150] Application Comparative Example 3

[0151] The difference from Application Example 1 is that the rhodium-palladium (Rh—Pd) metal nanosheets prepared in Preparation Comparative Example 3 are used as the material for the cathode catalyst layer.

[0152] Comparative Application Example 4

[0153] The difference from Application Example 1 is that the rhodium palladium copper (Rh—Pd—Cu) metal nanosheets prepared in Preparation Comparative Example 4 are used as the material for the cathode catalyst layer.

[0154] Application Comparative Example 5

[0155] The difference from Application Example 1 is that the rhodium-copper (Rh—Cu) metal nanosheets prepared in Preparation Comparative Example 5 are used as the material for the cathode catalyst layer.

[0156] The test results are shown in Table 2.

[0157] Table 2

[0158]

[0159]

[0160] (2) Oxygen reduction reaction

[0161] Application Example 2

[0162] The oxygen reduction reaction was carried out using a three-electrode system, wherein oxygen-saturated 1 mol / L HClO4 was used as the electrolyte, a platinum wire was used as the counter electrode, and a saturated calomel electrode (SCE) was used as the reference electrode. The test was carried out in a five-necked flask, and a rotating disk electrode loaded with rhodium palladium platinum (Rh-Pd-Pt) metal nanosheets prepared in Preparation Example 2 of the present application was used as the working electrode, and the platinum wire was used as the counter electrode. The loading amount of the working electrode was 1 mg / cm 2 .

[0163] Application Comparative Example 2

[0164] The difference from Application Example 2 is that the rhodium palladium platinum (Rh—Pd—Pt) metal nanosheets prepared in Preparation Comparative Example 2 are used as the material for the cathode catalyst layer.

[0165] The test results are shown in Table 3.

[0166] Table 3

[0167] Half-wave potential (V) Application Example 2 0.87V Application Comparative Example 2 0.82V

[0168] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0169] A rhodium source, a first metal carbonyl compound, and a first organic solvent are mixed and subjected to a first reaction. During this process, the first metal carbonyl compound acts as a surface capping agent to regulate the micromorphology of the rhodium nanosheets, so that rhodium nanosheets with a sheet-like structure are obtained after the first reaction. The rhodium nanosheets, other metal sources, a second metal carbonyl compound, and a second organic solvent are mixed and subjected to a second reaction. The other metal sources react with the surface of the rhodium nanosheets and grow to form an alloy of a noble metal source and / or a copper source and metallic rhodium, thereby obtaining multi-metal nanosheets with a higher catalytic reaction. Moreover, during the second reaction, the second metal carbonyl compound acts as a surface capping agent to regulate the micromorphology of the multi-metal nanosheets, forming a two-dimensional material containing rhodium elements and other metal elements of the above-mentioned specific types with a sheet-like structure. In addition, the first metal carbonyl compound and the second metal carbonyl compound can also play a reducing role, reducing the high-valent noble metal in the noble metal source to a low-valent state, thereby forming an alloy with rhodium.

[0170] Compared to nanosheets containing only rhodium elements, the above-mentioned multi-metal nanosheets provided in the present application include the above-mentioned specific ratio of rhodium elements (Rh) and other metal elements, and the other metal elements are selected from precious metal elements (one or more of Pd, Ru and Pt) and / or copper elements. By adjusting the type and ratio of elements, different reactions can be catalyzed, thereby improving the catalytic activity. Compared with other ranges, limiting the thickness of the multi-metal nanosheet to the above range can better exert the catalytic effect of the multi-metal nanosheet, thereby facilitating the catalysis of electrochemical reactions (such as electrolysis of water, electroreduction of CO2, oxygen reduction reaction, formic acid oxidation reaction, methanol oxidation reaction) and thermochemical reactions (such as CO oxidation reaction, NOx oxidation reaction, hydrogenation catalytic reaction of organic compounds such as phenol and anthracene), thereby broadening its application field.

[0171] It should be noted that the terms "first," "second," and the like in the specification and claims of this application are used to distinguish similar objects, and are not necessarily used to describe a specific order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate, so that the embodiments of the application described herein can, for example, be implemented in an order other than that described herein.

[0172] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A multi-element metal nanosheet, characterized in that: The multi-metal nanosheet comprises rhodium and other metal elements, wherein the other metal elements are selected from noble metal elements and / or copper elements, and the noble metal elements are selected from palladium and / or platinum; the thickness of the multi-metal nanosheet is 0.5 to 3 nm, wherein the multi-metal nanosheet comprises rhodium and palladium, and the weight ratio of the rhodium element to the palladium element is (2 to 50):1; or, the multi-metal nanosheet comprises rhodium and platinum, and the weight ratio of the rhodium element to the platinum element is (5 to 20):1; or , the multi-element metal nanosheet includes rhodium, palladium and copper, and the ratio of the weight of the rhodium element to the sum of the weights of the palladium element and the copper element is (2-60):1, and the weight ratio of the palladium element to the copper element is (3-20):1; or, the multi-element metal nanosheet includes rhodium, platinum and copper, and the ratio of the weight of the rhodium element to the sum of the weights of the platinum element and the copper element is (2-65):1, and the weight ratio of the platinum element to the copper element is (3-25):1; The preparation method of the multi-element metal nanosheets comprises: Step S1, mixing a rhodium source, a first metal carbonyl compound, and a first organic solvent to obtain a first mixed system; wherein, in the first mixed system, the molar concentration of the rhodium source is 0.1 to 5 μmol / mL, and the molar ratio of the rhodium source to the first metal carbonyl compound is 1:(1 to 6); Step S2, subjecting the first mixed system to a first reaction under heating conditions to obtain a first product system containing rhodium nanosheets, and obtaining the rhodium nanosheets after a first solid-liquid separation; Step S3, mixing the rhodium nanosheets, other metal sources, a second metal carbonyl compound, and a second organic solvent to obtain a second mixed system; wherein the other metal sources include a noble metal source and / or a copper source, and the noble metal source is selected from one or more of the group consisting of palladium acetylacetonate, palladium chloride, platinum acetylacetonate, and chloroplatinic acid; the copper source is selected from copper acetylacetonate and / or copper chloride; in the second mixed system, the mass concentration of the rhodium nanosheets is 0.05 to 0.4 mg / mL, and the molar concentration of the other metal sources is 0.01 to 3 μmol / mL; Step S4, allowing the second mixed system to undergo a second reaction under heating conditions to obtain a second product system, and obtaining the multi-element metal nanosheets after a second solid-liquid separation and drying treatment.

2. The multi-element metal nanosheet according to claim 1, characterized in that The specific surface area of ​​the multi-element metal nanosheet is 820 to 2000 cm 2 / g.

3. A method for preparing the multi-element metal nanosheets according to claim 1, characterized in that: The preparation method comprises: Step S1, mixing a rhodium source, a first metal carbonyl compound, and a first organic solvent to obtain a first mixed system; wherein, in the first mixed system, the molar concentration of the rhodium source is 0.1 to 5 μmol / mL, and the molar ratio of the rhodium source to the first metal carbonyl compound is 1:(1 to 6); Step S2, subjecting the first mixed system to a first reaction under heating conditions to obtain a first product system containing rhodium nanosheets, and obtaining the rhodium nanosheets after a first solid-liquid separation; Step S3, mixing the rhodium nanosheets, other metal sources, a second metal carbonyl compound, and a second organic solvent to obtain a second mixed system; wherein the other metal sources include a noble metal source and / or a copper source, and the noble metal source is selected from one or more of the group consisting of palladium acetylacetonate, palladium chloride, platinum acetylacetonate, and chloroplatinic acid; the copper source is selected from copper acetylacetonate and / or copper chloride; in the second mixed system, the mass concentration of the rhodium nanosheets is 0.05 to 0.4 mg / mL, and the molar concentration of the other metal sources is 0.01 to 3 μmol / mL; Step S4, allowing the second mixed system to undergo a second reaction under heating conditions to obtain a second product system, and obtaining the multi-element metal nanosheets after a second solid-liquid separation and drying treatment.

4. The method for preparing multi-element metal nanosheets according to claim 3, wherein: The rhodium source is selected from one or more of the group consisting of rhodium chloride, rhodium chloride trihydrate, rhodium bromide, rhodium bromide dihydrate and rhodium acetylacetonate; and / or, the first metal carbonyl compound is selected from one or more of the group consisting of molybdenum hexacarbonyl, iron pentacarbonyl and tungsten hexacarbonyl; and / or, the first organic solvent is selected from one or more of the group consisting of oleylamine, octadecene, oleic acid and toluene.

5. The method for preparing multi-element metal nanosheets according to claim 3, wherein: The temperature of the first reaction is 140-200° C., and the time is 2-8 hours.

6. The method for preparing multi-element metal nanosheets according to claim 3, wherein: The first reaction is carried out in a protective gas, or in a protective gas and a reducing gas, the protective gas is selected from nitrogen and / or argon, and the reducing gas is carbon monoxide.

7. The method for preparing multi-element metal nanosheets according to claim 3, wherein: The step S2 further comprises: after the first reaction is completed, cooling the temperature to room temperature at a cooling rate of 10 to 40° C. / min, and performing the first solid-liquid separation to obtain the rhodium nanosheets.

8. The method for preparing multi-element metal nanosheets according to claim 7, wherein: The first solid-liquid separation is performed by centrifugation.

9. The method for preparing multi-element metal nanosheets according to claim 8, wherein: During the first solid-liquid separation, the centrifugal speed is 1500-2500 r / min and the time is 1-3 minutes.

10. The method for preparing multi-element metal nanosheets according to any one of claims 3 to 9, characterized in that: The molar ratio of the other metal source to the second metal carbonyl compound is 1:(1-11).

11. The method for preparing multi-element metal nanosheets according to claim 10, characterized in that: The second metal carbonyl compound is selected from one or more of the group consisting of molybdenum hexacarbonyl, iron pentacarbonyl and tungsten hexacarbonyl; and / or the second organic solvent is selected from oleylamine and / or oleic acid.

12. The method for preparing multi-element metal nanosheets according to claim 3, wherein: The second reaction is carried out in a mixed atmosphere of protective gas and carbon monoxide.

13. The method for preparing multi-element metal nanosheets according to claim 12, wherein: In the second reaction, the volume ratio of the carbon monoxide to the protective gas is (0.5-50):1; the protective gas in the second reaction is selected from nitrogen and / or argon.

14. The method for preparing multi-element metal nanosheets according to claim 12, wherein: The temperature of the second reaction is 110-190° C., and the time is 1-6 hours.

15. The method for preparing multi-element metal nanosheets according to claim 14, characterized in that: The temperature of the second reaction is 120-140° C., and the time is 2-4 hours.

16. The method for preparing multi-element metal nanosheets according to any one of claims 3 to 9, characterized in that: The step S4 further includes: washing to remove impurities after the second solid-liquid separation, and then performing the drying process to obtain the multi-element metal nanosheets.

17. The method for preparing multi-element metal nanosheets according to claim 16, wherein: The washing is performed using a mixture of n-hexane and ethanol, the washing times are 3 times, the washing speeds are 3000-4000 r / min, 2400-3600 r / min and 1800-2800 r / min, and the washing time for each washing is independently 1-3 minutes.

18. The method for preparing multi-element metal nanosheets according to claim 16, wherein: The second solid-liquid separation is performed by centrifugation, with a centrifugal speed of 2000-4000 r / min and a time of 1-3 minutes.

19. The method for preparing multi-element metal nanosheets according to claim 16, wherein: The drying process is performed at a temperature of 70 to 90° C. and for a time of 12 to 24 hours.

20. The method for preparing multi-element metal nanosheets according to any one of claims 3 to 9, characterized in that: The step S4 further includes: after the second reaction is completed, lowering the temperature of the second product system to 80° C. at a cooling rate of 10-40° C. / min, performing the second solid-liquid separation using n-hexane, and obtaining the multi-element metal nanosheets after the drying process.

21. Use of the multi-element metal nanosheet according to claim 1 or 2 in water electrolysis, CO2 electroreduction reaction, oxygen reduction reaction, formic acid oxidation reaction, methanol oxidation reaction, CO oxidation reaction, NOx oxidation reaction or hydrogenation catalytic reaction.

Images