A general method for the preparation of two-dimensional metal nanosheets
Two-dimensional metal nanosheets were prepared by in-situ electrochemical reduction, which solved the problem of easy corrosion and oxidation of metal nanosheets in the existing technology and achieved stable electrocatalytic performance and efficient urea synthesis.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HEFEI UNIV OF TECH
- Filing Date
- 2023-05-17
- Publication Date
- 2026-06-19
AI Technical Summary
Existing technologies struggle to prepare stable and efficient two-dimensional metal nanosheets, especially in electrocatalysis, where conventional methods can easily lead to metal corrosion or oxidation, affecting catalytic performance.
An in-situ electrochemical reduction process was adopted to exfoliate metal tellurides or selenides by cryogenic-ultrasonic liquid phase, followed by the preparation of two-dimensional metal nanosheets in an H-type electrolytic cell using CO2 as a reducing agent. This process avoids the use of additional reducing agents and directly forms stable two-dimensional metal nanosheets on carbon paper.
The obtained two-dimensional metal nanosheets have a stable structure, smooth surface, and uniform size, making them suitable for the electrocatalytic coupling reaction of CO2 and nitrate, thus achieving high efficiency and high yield in urea synthesis.
Abstract
Description
Technical Field
[0001] This invention relates to the fields of materials science and electrocatalysis, specifically to a universal preparation method for obtaining two-dimensional metal nanosheets during an in-situ electrochemical reduction process. Background Technology
[0002] In recent years, with the advancement of science and technology, the development of nanomaterials has become increasingly rapid. Two-dimensional materials, in particular, refer to materials where electrons can move freely only in two dimensions at a non-nanoscale scale (1–100 nm), such as nanosheets and nanofilms. Two-dimensional materials, due to their unique surface interface effects and quantum size effects, typically exhibit special physical and chemical properties, attracting widespread attention. Two-dimensional metallic materials have broad application prospects in the field of new energy conversion and storage, such as their excellent catalytic performance (Cu, Bi, Sn, etc.). In two-dimensional planar structures, due to the greater number of exposed active metal sites, their catalytic behavior can be significantly enhanced. For example, two-dimensional Cu has the ability to adsorb nitrate ions, which can improve CN coupling performance and can be used for the electrochemical synthesis of urea; two-dimensional Bi and Sn have excellent adsorption capacity for CO2 and can be widely used in the field of electrocatalytic CO2 reduction.
[0003] Current methods for preparing two-dimensional materials (such as mechanical exfoliation) are generally only applicable to materials with a layered structure and have very low yields. Previous methods involving repeated mechanical rolling of two metal foils followed by etching away one of the metals have been reported; however, when using acids or alkalis to etch away the sacrificial metal, the more reactive target metal is also corroded or oxidized to varying degrees, ultimately leading to unstable electrocatalytic performance. Therefore, exploring a simple, mild, and controllable method for preparing two-dimensional metal nanosheets to achieve efficient electrocatalytic reduction has become a focus of attention. Summary of the Invention
[0004] Based on the problems existing in the prior art, the purpose of this invention is to provide a universal method for preparing two-dimensional metal nanosheets to obtain two-dimensional metal nanosheets with stable electrocatalytic performance, so that they can be used in reactions such as the co-reduction of CO2 and nitrate to produce urea.
[0005] To achieve its objectives, the present invention employs the following technical solution:
[0006] A universal method for preparing two-dimensional metal nanosheets, wherein the two-dimensional metal nanosheets are obtained through an in-situ electrochemical reduction process: firstly, metal telluride or metal selenide is subjected to freeze-ultrasonic liquid-phase exfoliation to obtain two-dimensional metal telluride nanosheets or two-dimensional metal selenide nanosheets; then, the two-dimensional metal telluride nanosheets or two-dimensional metal selenide nanosheets are reduced in an H-type electrolytic cell system to obtain the two-dimensional metal nanosheets. Specifically, the method includes the following steps:
[0007] Step 1: Freeze the metal telluride or metal selenide in liquid nitrogen, then disperse the frozen sample in a mixture of isopropanol and water and sonicate it. After sonication, centrifuge to obtain two-dimensional metal telluride nanosheets or two-dimensional metal selenide nanosheets.
[0008] Step 2: Disperse the two-dimensional metal telluride nanosheets or two-dimensional metal selenide nanosheets obtained in Step 1 in ethanol, and then spray them onto carbon paper to obtain carbon paper uniformly loaded with two-dimensional metal telluride nanosheets or two-dimensional metal selenide nanosheets.
[0009] In an H-type electrolytic cell system, a platinum sheet is used as the counter electrode, Ag / AgCl as the reference electrode, and carbon paper uniformly loaded with two-dimensional metal telluride nanosheets or two-dimensional metal selenide nanosheets is used as the working electrode. Potassium nitrate aqueous solution is used as the electrolyte. CO2 is introduced into the electrolytic cell system, and a voltage is applied to carry out the reaction. After the reaction is completed, the carbon paper used as the working electrode is removed, washed with water, and dried to obtain two-dimensional metal nanosheets on the carbon paper.
[0010] Preferably, in step 1, the freezing time is 6-8 hours and the ultrasonic time is 4-8 hours.
[0011] Preferably, in step 2, the concentration of the potassium nitrate aqueous solution is 0.1–0.5 mol / L.
[0012] Preferably, in step 2, the CO2 introduction rate is 20–30 sccm.
[0013] Preferably, the reaction time in step 2 is 1 to 2 hours.
[0014] Preferably, the metal telluride or metal selenide is a telluride or selenide of metals Bi, Sn and / or Cu.
[0015] Compared with the prior art, the beneficial effects of the present invention are reflected in:
[0016] 1. This invention obtains two-dimensional metal nanosheets through an in-situ electrochemical reduction process without the need to add other reducing agents, and the electrolyte does not require any other metal elements. The product has a stable structure, requires little equipment, is simple in method, has mild conditions, short operation time, and is green and environmentally friendly, making it suitable for large-scale production.
[0017] 2. The material prepared by this invention has a novel structure, a smooth surface, and uniform dimensions.
[0018] 3. The two-dimensional metal nanosheets obtained in this invention are located on conductive carbon paper and can be directly used as the working electrode for electrocatalytic CN coupling. Under room temperature conditions, nitrate ions are electrochemically coupled with CO2 to achieve urea synthesis. The urea synthesis yield and efficiency are 0.66 μmol / h. -1cm -1 and 9.97%. Attached Figure Description
[0019] Figure 1 This is a SEM image of the two-dimensional metallic Bi nanosheets obtained in Example 1. Figure 1 XRD patterns of (a) and two-dimensional Bi₂Se₃ nanosheets and two-dimensional metallic Bi nanosheets. Figure 1 (b)
[0020] Figure 2 This is a SEM image of the two-dimensional metallic Sn nanosheets obtained in Example 2. Figure 2 XRD patterns of (a) and two-dimensional SnSe nanosheets and two-dimensional metallic Sn nanosheets (a) Figure 2 (b)
[0021] Figure 3 This is a SEM image of the two-dimensional Cu nanosheets obtained in Example 3. Figure 3 XRD patterns of (a) and two-dimensional CuSe nanosheets and two-dimensional metallic Cu nanosheets (a) Figure 3 (b)
[0022] Figure 4 This is a SEM image of the two-dimensional metallic Bi nanosheets obtained in Example 4. Figure 4 XRD patterns of (a) and two-dimensional Bi₂Te₃ nanosheets and two-dimensional metallic Bi nanosheets. Figure 4 (b)
[0023] Figure 5 This is a SEM image of the two-dimensional Cu nanosheets obtained in Example 5. Figure 5 XRD patterns of (a) and two-dimensional Cu₂Te nanosheets and two-dimensional metallic Cu nanosheets. Figure 5 (b)
[0024] Figure 6 This is a SEM image of the two-dimensional metallic Sn nanosheets obtained in Example 6. Figure 6 XRD patterns of (a) and two-dimensional SnTe nanosheets and two-dimensional metallic Sn nanosheets (a) Figure 6 (b)
[0025] Figure 7 This is a UV spectrum of the two-dimensional metal Cu nanosheets electrocatalyzed CN coupling obtained in Example 5.
[0026] Figure 8 The diagrams show the Faraday efficiency and yield of the two-dimensional metal Cu nanosheets electrocatalyzing CN coupling obtained in Example 5. Detailed Implementation
[0027] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention are described in detail below with reference to examples. The following content is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific examples described, or use similar methods to replace them, as long as they do not depart from the inventive concept or exceed the scope defined in the claims, and all such modifications or additions should fall within the protection scope of the present invention.
[0028] Example 1
[0029] In this embodiment, two-dimensional metallic Bi nanosheets were prepared according to the following steps:
[0030] Step 1: Freeze Bi2Se3 in liquid nitrogen for 6 hours, then disperse the frozen sample in a mixture of isopropanol and water (volume ratio 1:1) and sonicate for 4 hours. After sonication, centrifuge to obtain two-dimensional Bi2Se3 nanosheets.
[0031] Step 2: Disperse the two-dimensional Bi2Se3 nanosheets obtained in Step 1 in ethanol, and then spray them onto carbon paper to obtain carbon paper uniformly loaded with two-dimensional Bi2Se3 nanosheets.
[0032] In an H-type electrolytic cell system, a platinum sheet was used as the counter electrode, Ag / AgCl as the reference electrode, carbon paper uniformly loaded with two-dimensional Bi₂Se₃ nanosheets was used as the working electrode, and 0.1 mol / L potassium nitrate aqueous solution was used as the electrolyte. CO₂ was introduced into the electrolytic cell system at a flow rate of 20 sccm, and a voltage of -1 V (vs. RHE) was applied for 1 h. After the reaction was completed, the carbon paper used as the working electrode was removed, washed with deionized water, and dried to obtain two-dimensional metallic Bi nanosheets on the carbon paper.
[0033] Figure 1 This is a SEM image of the two-dimensional metallic Bi nanosheets obtained in this embodiment. Figure 1 XRD patterns of (a) and two-dimensional Bi₂Se₃ nanosheets and two-dimensional metallic Bi nanosheets. Figure 1 (b)). XRD pattern confirms that the reaction yielded a Bi elemental phase, and SEM shows that the obtained product has a nanosheet structure.
[0034] Example 2
[0035] In this embodiment, two-dimensional metallic Sn nanosheets are prepared according to the following steps:
[0036] Step 1: Freeze SnSe in liquid nitrogen for 6 hours, then disperse the frozen sample in a mixture of isopropanol and water (volume ratio 1:1) and sonicate for 5 hours. After sonication, centrifuge to obtain two-dimensional SnSe nanosheets.
[0037] Step 2: Disperse the two-dimensional SnSe nanosheets obtained in Step 1 in ethanol, and then spray them onto carbon paper to obtain carbon paper uniformly loaded with two-dimensional SnSe nanosheets.
[0038] In an H-type electrolytic cell system, a platinum sheet was used as the counter electrode, Ag / AgCl as the reference electrode, carbon paper uniformly loaded with two-dimensional SnSe nanosheets as the working electrode, and 0.2 mol / L potassium nitrate aqueous solution was used as the electrolyte. CO2 was introduced into the electrolytic cell system at a flow rate of 20 sccm, and a voltage of -1V (vs. RHE) was applied for 1 h. After the reaction was completed, the carbon paper used as the working electrode was removed, washed with deionized water, and dried to obtain two-dimensional metallic Sn nanosheets on the carbon paper.
[0039] Figure 2 This is a SEM image of the two-dimensional metallic Sn nanosheets obtained in this embodiment. Figure 2 XRD patterns of (a) and two-dimensional SnSe nanosheets and two-dimensional metallic Sn nanosheets (a) Figure 2 (b)). XRD pattern confirms that Sn elemental phase was obtained after the reaction, and SEM shows that the obtained product is a nanosheet structure.
[0040] Example 3
[0041] In this embodiment, two-dimensional Cu nanosheets are prepared according to the following steps:
[0042] Step 1: Freeze CuSe in liquid nitrogen for 7 hours, then disperse the frozen sample in a mixture of isopropanol and water (volume ratio 1:1) and sonicate for 6 hours. After sonication, centrifuge to obtain two-dimensional CuSe nanosheets.
[0043] Step 2: Disperse the two-dimensional CuSe nanosheets obtained in Step 1 in ethanol, and then spray them onto carbon paper to obtain carbon paper uniformly loaded with two-dimensional CuSe nanosheets.
[0044] In an H-type electrolytic cell system, a platinum sheet was used as the counter electrode, Ag / AgCl as the reference electrode, carbon paper uniformly loaded with two-dimensional CuSe nanosheets as the working electrode, and 0.3 mol / L potassium nitrate aqueous solution was used as the electrolyte. CO2 was introduced into the electrolytic cell system at a flow rate of 25 sccm, and a voltage of -1V (vs. RHE) was applied for 1.5 h. After the reaction was completed, the carbon paper used as the working electrode was removed, washed with deionized water, and dried to obtain two-dimensional metallic Cu nanosheets on the carbon paper.
[0045] Figure 3 This is a SEM image of the two-dimensional Cu nanosheets obtained in this embodiment. Figure 3 XRD patterns of (a) and two-dimensional CuSe nanosheets and two-dimensional metallic Cu nanosheets (a) Figure 3(b)). XRD pattern confirms that Cu elemental phase was obtained after the reaction, and SEM shows that the obtained product is a nanosheet structure.
[0046] Example 4
[0047] In this embodiment, two-dimensional metallic Bi nanosheets were prepared according to the following steps:
[0048] Step 1: Freeze Bi2Te3 in liquid nitrogen for 7 hours, then disperse the frozen sample in a mixture of isopropanol and water (volume ratio 1:1) and sonicate for 7 hours. After sonication, centrifuge to obtain two-dimensional Bi2Te3 nanosheets.
[0049] Step 2: Disperse the two-dimensional Bi2Te3 nanosheets obtained in Step 1 in ethanol, and then spray them onto carbon paper to obtain carbon paper uniformly loaded with two-dimensional Bi2Te3 nanosheets.
[0050] In an H-type electrolytic cell system, a platinum sheet was used as the counter electrode, Ag / AgCl as the reference electrode, carbon paper uniformly loaded with two-dimensional Bi2Te3 nanosheets was used as the working electrode, and 0.4 mol / L potassium nitrate aqueous solution was used as the electrolyte. CO2 was introduced into the electrolytic cell system at a flow rate of 25 sccm, and a voltage of -1V (vs. RHE) was applied for 1.5 h. After the reaction was completed, the carbon paper used as the working electrode was removed, washed with deionized water, and dried to obtain two-dimensional metallic Bi nanosheets on the carbon paper.
[0051] Figure 4 This is a SEM image of the two-dimensional metallic Bi nanosheets obtained in this embodiment. Figure 4 XRD patterns of (a) and two-dimensional Bi₂Te₃ nanosheets and two-dimensional metallic Bi nanosheets. Figure 4 (b)). XRD pattern confirms that the reaction yielded a Bi elemental phase, and SEM shows that the obtained product has a nanosheet structure.
[0052] Example 5
[0053] In this embodiment, two-dimensional Cu nanosheets are prepared according to the following steps:
[0054] Step 1: Freeze Cu2Te in liquid nitrogen for 8 hours, then disperse the frozen sample in a mixture of isopropanol and water (volume ratio 1:1) and sonicate for 8 hours. After sonication, centrifuge to obtain two-dimensional Cu2Te nanosheets.
[0055] Step 2: Disperse the two-dimensional Cu2Te nanosheets obtained in Step 1 in ethanol, and then spray them onto carbon paper to obtain carbon paper uniformly loaded with two-dimensional Cu2Te nanosheets.
[0056] In an H-type electrolytic cell system, a platinum sheet was used as the counter electrode, Ag / AgCl as the reference electrode, carbon paper uniformly loaded with two-dimensional Cu2Te nanosheets was used as the working electrode, and 0.5 mol / L potassium nitrate aqueous solution was used as the electrolyte. CO2 was introduced into the electrolytic cell system at a flow rate of 30 sccm, and a voltage of -1V (vs. RHE) was applied for 2 hours. After the reaction was completed, the carbon paper used as the working electrode was removed, washed with deionized water, and dried to obtain two-dimensional metallic Cu nanosheets on the carbon paper.
[0057] Figure 5 This is a SEM image of the two-dimensional Cu nanosheets obtained in this embodiment. Figure 5 XRD patterns of (a) and two-dimensional Cu₂Te nanosheets and two-dimensional metallic Cu nanosheets. Figure 5 (b)). XRD pattern confirms that Cu elemental phase was obtained after the reaction, and SEM shows that the obtained product is a nanosheet structure.
[0058] Example 6
[0059] In this embodiment, two-dimensional metallic Sn nanosheets are prepared according to the following steps:
[0060] Step 1: Freeze SnTe in liquid nitrogen for 8 hours, then disperse the frozen sample in a mixture of isopropanol and water (volume ratio 1:1) and sonicate for 8 hours. After sonication, centrifuge to obtain two-dimensional SnTe nanosheets.
[0061] Step 2: Disperse the two-dimensional SnTe nanosheets obtained in Step 1 in ethanol, and then spray them onto carbon paper to obtain carbon paper uniformly loaded with two-dimensional SnTe nanosheets.
[0062] In an H-type electrolytic cell system, a platinum sheet was used as the counter electrode, Ag / AgCl as the reference electrode, carbon paper uniformly loaded with two-dimensional SnTe nanosheets as the working electrode, and 0.5 mol / L potassium nitrate aqueous solution was used as the electrolyte. CO2 was introduced into the electrolytic cell system at a flow rate of 30 sccm, and a voltage of -1V (vs. RHE) was applied for 2 hours. After the reaction was completed, the carbon paper used as the working electrode was removed, washed with deionized water, and dried to obtain two-dimensional metallic Sn nanosheets on the carbon paper.
[0063] Figure 6 This is a SEM image of the two-dimensional metallic Sn nanosheets obtained in this embodiment. Figure 6 XRD patterns of (a) and two-dimensional SnTe nanosheets and two-dimensional metallic Sn nanosheets (a) Figure 6 (b)). XRD pattern confirms that Sn elemental phase was obtained after the reaction, and SEM shows that the obtained product is a nanosheet structure.
[0064] The electrocatalytic CN-coupling synthesis performance of the two-dimensional Cu nanosheets prepared in Example 5 was tested in an H-cell electrolytic cell: In the H-cell system, a platinum sheet was used as the counter electrode, Ag / AgCl as the reference electrode, carbon paper uniformly loaded with two-dimensional Cu nanosheets as the working electrode, and a 0.1 mol / L potassium nitrate aqueous solution was used as the electrolyte. CO2 was introduced into the electrolytic cell system at a flow rate of 20 sccm, and different voltages (-0.1, -0.2, -0.3, -0.4, -0.5 V (vs. RHE)) were applied for 1 h. The electrolyte after the cathode reaction was collected, and the electrolyte was quantitatively analyzed by a UV spectrophotometer. The results are as follows: Figure 7 and Figure 8 As shown in the figure, the urea synthesis yield and efficiency reach their highest values at -0.2V (vs. RHE), which are 0.66 μmol h⁻¹, respectively. -1 cm -1 The results showed that the obtained material had the ability to efficiently electrocatalyze the CN-coupling synthesis of urea, with a yield of 9.97%.
[0065] The above description is merely an example and illustration of the concept of the present invention. Various modifications or additions to the specific embodiments described by those skilled in the art, or substitutions using similar methods, shall fall within the protection scope of the present invention as long as they do not deviate from the inventive concept or exceed the scope defined in the claims.
Claims
1. A general method for the preparation of two-dimensional metal nanosheets, characterized in that, The two-dimensional metal nanosheets were prepared by an in-situ electrochemical reduction process, including the following steps: Step 1: Freeze the metal telluride or metal selenide in liquid nitrogen for 6-8 hours. Then, disperse the frozen sample in a mixture of isopropanol and water and sonicate for 4-8 hours. After sonication, centrifuge to obtain two-dimensional metal telluride nanosheets or two-dimensional metal selenide nanosheets. The metal telluride or metal selenide is a telluride or selenide of metals Bi, Sn and / or Cu. Step 2: Disperse the two-dimensional metal telluride nanosheets or two-dimensional metal selenide nanosheets obtained in Step 1 in ethanol, and then spray them onto carbon paper to obtain carbon paper uniformly loaded with two-dimensional metal telluride nanosheets or two-dimensional metal selenide nanosheets. In an H-type electrolytic cell system, a platinum sheet is used as the counter electrode, Ag / AgCl as the reference electrode, and carbon paper uniformly loaded with two-dimensional metal telluride nanosheets or two-dimensional metal selenide nanosheets as the working electrode. Potassium nitrate aqueous solution is used as the electrolyte. CO2 is introduced into the electrolytic cell system, and a voltage of -1V (vs. RHE) is applied for 1-2 hours. After the reaction is completed, the carbon paper used as the working electrode is removed, washed with water, and dried to obtain two-dimensional metal nanosheets on the carbon paper. The two-dimensional metal nanosheets are nanosheets of two-dimensional metal Bi, Sn, and / or Cu elemental phases.
2. The method of claim 1, wherein: In step 2, the concentration of the potassium nitrate aqueous solution is 0.1~0.5 mol / L.
3. The method of claim 1, wherein: In step 2, the CO2 introduction rate is 20~30 sccm.
4. Two-dimensional metal nanosheets prepared by a universal preparation method of any one of claims 1 to 3.
5. The application of the two-dimensional metal nanosheets of claim 4 in the electrocatalytic CN-coupling synthesis of urea, wherein the two-dimensional metal nanosheets are two-dimensional Cu nanosheets.