Method for preparing au@pdc concave cube in deep eutectic solvent and application thereof

Abstract

The application relates to a method for preparing Au@Pd concave cubes in a eutectic solvent and application, wherein dried choline chloride and ethylene glycol are stirred at 80 DEG C until a uniform colorless liquid is formed to form a eutectic solvent DESs; the DESs is placed in a water bath and heated to 40 DEG C-70 DEG C under stirring; then, HAuCl4 and Na2PdCl4 are added into the DESs; ascorbic acid is added into the mixture; the obtained solution is stirred at 30 DEG C-80 DEG C for 3h; the product is washed with anhydrous ethanol for three times; then, the product is dried in a vacuum oven at 60 DEG C for 24h to obtain Au@Pd concave cubes. The application does not need to add seeds, surfactants, hard templates or soft templates, and does not need complex conditions such as high pressure, calcination, specific pH, etc., and can synthesize Au@Pd concave cubes with uniform morphology and stable structure in one step. The operation is simple, the product is easy to separate, and the Au@Pd concave cubes have excellent catalytic activity and selectivity in the catalytic hydrogenation reaction of p-nitrostyrene.

Description

Technical Field

[0001] This invention relates to the field of bimetallic nanomaterial preparation, specifically to a method and application for preparing Au@Pd concave cubes in a one-step process without adding any template agent or seed crystals in a eutectic solvent formed by choline chloride and ethylene glycol. Background Technology

[0002] Nanomaterials are materials with at least one nanoscale dimension in three-dimensional space or composed of nanoscale components, and they possess immense development potential. Noble metal materials at the nanoscale play a crucial role in hydrogen storage, catalysis, and electronics due to their unique electrical, magnetic, and optical properties. However, in practical applications, the catalytic performance of elemental noble metal nanomaterials is difficult to regulate, especially their selective catalytic performance. Introducing a second metal is an effective method to improve the selective catalytic activity of noble metal nanomaterials. By introducing a second metal, the electronic, geometric, and collective effects between the metals can be controlled, thereby regulating their catalytic activity and selectivity. Currently, the preparation of noble metal nanomaterials mostly requires the introduction of surfactants such as hexadecyltrimethylammonium bromide (CTAB), hexadecyltrimethylammonium chloride (CTAC), and polyvinylpyrrolidone (PVP). These surfactants typically have strong adsorption effects on the nanocrystal surface, leading to the covering of some active sites. Even with methods such as high-temperature calcination, it is difficult to completely remove them, thus reducing their catalytic activity. Therefore, developing a mild, surfactant-free one-pot method to prepare bimetallic nanomaterials with uniform particle size and excellent catalytic activity and selectivity remains a significant challenge.

[0003] AuPd bimetallic nanomaterials have wide applications in catalysis, such as fuel cells, CO2 electroreduction, hydrogenation, coupling reactions, aerobic oxidation, and formic acid decomposition for hydrogen release. Their catalytic performance is closely related to their structure and composition. Currently, many AuPd nanomaterials with different morphologies and compositions have been successfully prepared. For example, Chinese invention patent CN114848815A reports a method for preparing Au@Pd nanoparticles with a sea urchin-like structure: First, an aqueous solution of sodium citrate is heated to 100°C and stirred for 15 min. Then, an aqueous solution of HAuCl4 is added and stirred for 15 min. After cooling to 85°C-95°C, a certain concentration of aqueous solutions of sodium citrate and HAuCl4 is added again, and the mixture is stirred for 30 min to obtain a colloid containing Au nanospheres. This colloid is then added to an aqueous solution containing one or both of hexadecylpyridine chloride and CTAC, stirred until transparent, and mixed thoroughly. Finally, under stirring conditions at 60℃-70℃, Na2PdCl4 aqueous solution and ascorbic acid (AA) aqueous solution were added sequentially to obtain urchin-like Au@Pd nanoparticles. This patented preparation process requires multiple steps and the application of surfactants to control its morphology and structure. It is not only time-consuming and labor-intensive, but the active sites on the nanomaterial surface may be partially covered by surfactants, reducing their activity. Chinese invention patent application CN108355652A reports a method for preparing AuPd nanocatalysts for CO oxidation: TiO2 support, HAuCl4 solution, and H2PdCl4 precursor solution are mixed uniformly, stirred at 25℃ for 4 hours, then centrifuged, dried, and heat-treated at 300℃ in an inert atmosphere to obtain AuPd nanocatalysts. This patented preparation method requires a support and inert gas protection, the steps are relatively cumbersome, high-temperature sintering is required, and energy consumption is high. Therefore, developing a simple and easy one-pot method to prepare AuPd nanomaterials with clean surfaces and high catalytic activity and selectivity is essential. Summary of the Invention

[0004] The purpose of this invention is to provide a simple and easy one-pot method for preparing Au@Pd concave cubes in a eutectic solvent and its application. The method utilizes a eutectic solvent (DESs) system formed by choline chloride (ChCl) and ethylene glycol (EG) to prepare Au@Pd concave cubes. This preparation method is simple, green, and operates under mild reaction conditions. It does not require the addition of seeds, surfactants, hard or soft templates, nor does it require complex conditions such as high pressure, calcination, or specific pH. It can prepare uniformly morphologically uniform and clean-surfaced Au@Pd concave cube nanomaterials in one step. These Au@Pd nanomaterials exhibit high stability and a rough surface, which facilitates effective contact and rapid transport of reactants. The intermetallic electronic effect greatly enhances their catalytic activity and selectivity.

[0005] This invention is specifically achieved through the following technical solution: a method for preparing Au@Pd concave cubes in a eutectic solvent according to this invention, which specifically includes the following steps:

[0006] 1) Dry choline chloride in a vacuum oven at 80°C for 8 hours, and then stir choline chloride and ethylene glycol in a water bath at 80°C until a uniform colorless liquid is formed, forming a eutectic solvent DESs.

[0007] 2) Place the newly prepared DESs in a water bath and stir and heat to 40℃-70℃, then add HAuCl4 and Na2PdCl4 to it;

[0008] 3) Add ascorbic acid to the mixture obtained in step 2), and then stir the reaction at 30℃-80℃ for 3h. Wash the product three times with anhydrous ethanol, and then dry it in a vacuum oven at 60℃ for 24h to obtain Au@Pd concave cubes.

[0009] In the aforementioned method for preparing Au@Pd concave cubes in a eutectic solvent, the molar ratio of choline chloride to ethylene glycol in step 1) is 1:2.

[0010] In the aforementioned method for preparing Au@Pd concave cubes in a eutectic solvent, the molar ratio of Au to Pd in ​​step 2) is 3:1, 2:1, 1:1, 1:2, or 1:3.

[0011] Furthermore, the total amount of Au and Pd is 20 mmol.

[0012] Furthermore, in step 2), the amount of DESs used is 10 mL, and in step 3), the amount of ascorbic acid added is 0.1-0.5 g.

[0013] The Au@Pd prepared according to the above method has a concave cubic structure with a side length of 80 nm. The surface of the cubic structure has many rough and dense nanoparticles with a particle size of 10 nm. The nanoparticles are more abundant at the corners of the cubic structure and less abundant at the concave surface. Furthermore, the Au@Pd concave cubic structure has a core-shell structure, with an Au core in the inner layer and a Pd shell in the outer layer.

[0014] This invention also provides an Au@Pd concave cube prepared according to the above method and its application in the catalytic hydrogenation of p-nitrostyrene to p-nitrobenzeneethane. The catalytic hydrogenation reaction of p-nitrostyrene by the Au@Pd concave cube was carried out in an ethanol solution at 25°C and atmospheric pressure, and the reaction was completed in 7.0 min. The conversion rate of p-nitrostyrene was 100%, and the selectivity for p-nitrobenzeneethane was 100%. This indicates that the Au@Pd catalyst prepared by this invention has excellent catalytic activity and selectivity in the catalytic hydrogenation reaction of p-nitrostyrene.

[0015] Compared with existing technologies, this invention has significant advantages and beneficial effects. Through the above technical solution, this invention achieves considerable technological advancement and practicality, and has broad application value, possessing at least the following advantages:

[0016] (1) This invention utilizes a eutectic solvent (DESs) system formed by choline chloride (ChCl) and ethylene glycol (EG) to prepare Au@Pd concave cubic nanomaterials. DESs are characterized by low vapor pressure, non-toxicity, biodegradability, and good stability, making them a green and relatively inexpensive solvent. ChCl and EG are both inexpensive, readily available, and biodegradable industrial raw materials. The preparation process of DESs is simple, requiring only a certain amount of stirring time. This invention is simple to operate, green, and uses mild reaction conditions. It does not require the addition of seeds, surfactants, hard or soft templates, nor does it require complex conditions such as high pressure, calcination, or specific pH. Only the precursors HAuCl4 and Na2PdCl4 need to be added to DESs, followed by the addition of AA, to prepare Au@Pd concave cubic nanomaterials with uniform morphology and stable structure in one step. The operation is simple, and the product is easy to separate.

[0017] (2) The Au@Pd prepared in this invention has a cubic structure with a side length of approximately 80 nm and a distinct concave structure. The surface of the cubic structure has many rough and dense nanoparticles, with more nanoparticles at the corners and fewer at the concave surfaces. The Au@Pd concave cubic nanomaterial has high stability, and the rough surface is conducive to the effective contact and rapid transport of reactants. Furthermore, the Au@Pd concave cubic structure has a core-shell structure, with an Au core and a Pd shell. The electronic effect between the metals greatly enhances its catalytic activity and selectivity. When used as a catalyst for the catalytic hydrogenation of p-nitrostyrene, the reaction can be completed in just 7.0 min in an ethanol solution at 25 °C and atmospheric pressure, with a 100% conversion rate of p-nitrostyrene and a 100% selectivity for p-nitrobenzeneethane, and it also exhibits good stability in use. Attached Figure Description

[0018] Figure 1 This is a SEM image of the Au@Pd concave cube prepared in Example 1, magnified 50,000 times.

[0019] Figure 2 This is a SEM image of the Au@Pd concave cube prepared in Example 1, magnified 200,000 times.

[0020] Figure 3 This is a TEM image of the Au@Pd concave cube prepared in Example 1;

[0021] Figure 4These are HAADF-STEM images and elemental line scans of the Au@Pd concave cube prepared in Example 1;

[0022] Figure 5 The conversion rate and selectivity of p-nitrostyrene over time were measured using Au@Pd concave cubes prepared in Example 1 as catalysts for the hydrogenation reaction of p-nitrostyrene.

[0023] Figure 6 The figure shows the cyclic stability of the hydrogenation reaction of p-nitrostyrene catalyzed by Au@Pd concave cubes prepared in Example 1 as catalyst. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Example 1:

[0026] 1) Dry ChCl in a vacuum oven at 80°C for 8 hours. In a water bath at 80°C, stir ChCl and EG (the molar ratio of ChCl to EG is 1:2) until a uniform colorless liquid is formed, forming a eutectic solvent (DESs).

[0027] 2) Place 10 mL of the freshly prepared DESs from step 1) in a water bath and stir and heat to 40 °C. Then add HAuCl4 and Na2PdCl4 to it. The molar ratio of Au to Pd is 3:1, and the total amount of Au and Pd is 20 mmol.

[0028] 3) Add 0.1g of AA to the mixture obtained in step 2), and stir the resulting solution at 30℃ for 3h. Wash the product three times with anhydrous ethanol, and then dry it in a vacuum oven at 60℃ for 24h to prepare Au@Pd concave cubes.

[0029] Figure 1 This is a SEM image of the Au@Pd concave cube prepared in this embodiment, magnified 50,000 times. Figure 2 It's an SEM image magnified 200,000 times. Figure 1 and Figure 2 It is evident that the prepared Au@Pd generally has a cubic structure. Figure 2It is evident that the sample cube has a side length of approximately 80 nm and exhibits a distinct concave structure. Furthermore, the cube surface contains numerous rough and dense small particles, with a particle size of approximately 10 nm. These small particles are more abundant at the corners of the cube and less so at the concave surfaces.

[0030] Figure 3 This is a TEM image of the Au@Pd concave cube prepared in this embodiment, which confirms the cubic configuration of Au@Pd and clearly shows the nanoparticles on the surface of the cube.

[0031] Figure 4 The images show the HAADF-STEM image and elemental line scan of the Au@Pd concave cube prepared in this embodiment. It can be clearly seen that the sample has a concave cube Au core and an outer Pd shell, proving that the prepared bimetallic sample has a core-shell structure. In addition, it can be seen that the small nanoparticles on the surface of these concave cubes are mainly Pd nanoparticles.

[0032] Using the Au@Pd concave cubic catalyst prepared in this invention, the catalytic hydrogenation reaction of p-nitrostyrene was carried out in an ethanol solution at 25°C and atmospheric pressure. Under mild conditions, the reaction was completed in only 7.0 min, converting p-nitrostyrene to p-nitrobenzeneethane with a conversion rate of 100% and a selectivity of 100% for p-nitrostyrene. Figure 5 As shown, the Au@Pd catalyst prepared in this invention exhibits excellent catalytic activity and selectivity in the catalytic hydrogenation of p-nitrostyrene.

[0033] Using the Au@Pd concave cubic catalyst prepared in this invention as a catalyst, the catalytic hydrogenation reaction of p-nitrostyrene was carried out in an ethanol solution at 25°C and atmospheric pressure. After the catalyst was recycled 5 times, the conversion rate of p-nitrostyrene to p-nitrobenzeneethane still reached over 90%, and the selectivity for p-nitrobenzeneethane was 100% after 5 cycles. Figure 6 As shown, the Au@Pd catalyst prepared in this invention has good stability.

[0034] Example 2:

[0035] 1) Dry ChCl in a vacuum oven at 80°C for 8 hours. In a water bath at 80°C, stir ChCl and EG (the molar ratio of ChCl to EG is 1:2) until a uniform colorless liquid is formed, forming a eutectic solvent (DESs).

[0036] 2) Place 10 mL of the freshly prepared DESs from step 1) in a water bath and stir and heat to 50 °C. Then add HAuCl4 and Na2PdCl4 to it. The molar ratio of Au to Pd is 2:1, and the total amount of Au and Pd is 20 mmol.

[0037] 3) Add 0.2g of AA to the mixture obtained in step 2), and stir the resulting solution at 40℃ for 3h. Wash the product three times with anhydrous ethanol, and then dry it in a vacuum oven at 60℃ for 24h to prepare Au@Pd concave cubes.

[0038] Example 3:

[0039] 1) Dry ChCl in a vacuum oven at 80°C for 8 hours. In a water bath at 80°C, stir ChCl and EG (the molar ratio of ChCl to EG is 1:2) until a uniform colorless liquid is formed, forming a eutectic solvent (DESs).

[0040] 2) Place 10 mL of the freshly prepared DESs from step 1) in a water bath and stir and heat to 60 °C. Then add HAuCl4 and Na2PdCl4 to it. The molar ratio of Au to Pd is 1:1, and the total amount of Au and Pd is 20 mmol.

[0041] 3) Add 0.3g of AA to the mixture obtained in step 2), and stir the resulting solution at 50℃ for 3h. Wash the product three times with anhydrous ethanol, and then dry it in a vacuum oven at 60℃ for 24h to prepare Au@Pd concave cubes.

[0042] Example 4:

[0043] 1) Dry ChCl in a vacuum oven at 80°C for 8 hours. In a water bath at 80°C, stir ChCl and EG (the molar ratio of ChCl to EG is 1:2) until a uniform colorless liquid is formed, forming a eutectic solvent (DESs).

[0044] 2) Place 10 mL of the freshly prepared DESs from step 1) in a water bath and stir and heat to 70 °C. Then add HAuCl4 and Na2PdCl4 to it. The molar ratio of Au to Pd is 1:2, and the total amount of Au and Pd is 20 mmol.

[0045] 3) Add 0.4g of AA to the mixture obtained in step 2), and stir the resulting solution at 60℃ for 3h. Wash the product three times with anhydrous ethanol, and then dry it in a vacuum oven at 60℃ for 24h to prepare Au@Pd concave cubes.

[0046] Example 5:

[0047] 1) Dry ChCl in a vacuum oven at 80°C for 8 hours. In a water bath at 80°C, stir ChCl and EG (the molar ratio of ChCl to EG is 1:2) until a uniform colorless liquid is formed, forming a eutectic solvent (DESs).

[0048] 2) Place 10 mL of the freshly prepared DESs from step 1) in a water bath and stir and heat to 70 °C. Then add HAuCl4 and Na2PdCl4 to it. The molar ratio of Au to Pd is 1:3, and the total amount of Au and Pd is 20 mmol.

[0049] 3) Add 0.5g of AA to the mixture obtained in step 2), and stir the resulting solution at 30℃ for 3h. Wash the product three times with anhydrous ethanol, and then dry it in a vacuum oven at 60℃ for 24h to prepare Au@Pd concave cubes.

[0050] The above description is merely an embodiment of the present invention and is not intended to limit the present invention in any way. The present invention can also have other embodiments based on the above structure and function, which will not be listed hereafter. Therefore, any simple modifications, equivalent changes, and alterations made by those skilled in the art to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing Au@Pd concave cubes in deep eutectic solvents, characterized by: Includes the following steps: 1) Dry choline chloride in a vacuum oven at 80°C for 8 h, and then stir choline chloride and ethylene glycol in a water bath at 80°C until a uniform colorless liquid is formed, forming a eutectic solvent DESs. The molar ratio of choline chloride to ethylene glycol in this step is 1:

2. 2) Place the newly prepared DESs in a water bath and stir and heat to 40℃-70℃, then add HAuCl4 and Na2PdCl4 to it; 3) Add ascorbic acid to the mixture obtained in step 2), and then stir the reaction at 30℃-80℃ for 3 h. Wash the product three times with anhydrous ethanol, and then dry it in a vacuum oven at 60℃ for 24 h to obtain Au@Pd concave cubes with a side length of 80 nm. The surface of the cube has many rough and dense nanoparticles with a particle size of 10 nm. There are more nanoparticles at the corners of the cube and fewer at the concave surface. The Au@Pd concave cube has a core-shell structure with an Au core and a Pd shell on the outside.

2. The method for preparing Au@Pd concave cube in deep eutectic solvent according to claim 1, characterized in that: In step 2), the molar ratio of Au to Pd is 3:1, 2:1, 1:1, 1:2, or 1:

3.

3. The method for preparing Au@Pd concave cubes in a eutectic solvent as described in claim 2, characterized in that: In step 2), the total amount of Au and Pd is 20 mmol.

4. The method for preparing Au@Pd concave cubes in a eutectic solvent as described in claim 2, characterized in that: In step 2), the amount of DESs used is 10 mL, and in step 3), the amount of ascorbic acid added is 0.1-0.5 g.

5. The Au@Pd concave cube obtained by the method described in any one of claims 1-4.

6. The application of the Au@Pd concave cube obtained by the method of any one of claims 1-4 in the catalytic hydrogenation of p-nitrostyrene to p-nitrosyl ethane.

7. The application as described in claim 6, characterized in that: The catalytic hydrogenation reaction of Au@Pd concave cubes on p-nitrostyrene was carried out in an ethanol solution at 25°C and atmospheric pressure. The reaction was completed in 7.0 min, with a conversion rate of 100% for p-nitrostyrene and a selectivity of 100% for p-nitrobenzeneethane.

Images