Preparation method and application of tungsten diselenide nanomaterial

Abstract

The application relates to a preparation method and application of a tungsten diselenide nanomaterial. The method adopts a direct current arc plasma discharge method, tungsten powder and selenium powder are uniformly mixed according to a certain material molar ratio, pressed into a block, placed in an anode graphite pot of a reaction chamber, and a cathode tungsten rod is horizontally arranged opposite to the anode graphite pot. The discharge reaction is carried out in a water cooling system and an argon atmosphere protection, and after cooling and passivation, WSe2 nanomaterial is obtained at a condensing wall sleeve and a graphite pot. Meanwhile, the WSe2 nanomaterial is used for Li2S6 solution adsorption capacity test. The preparation process is simple, the material consumption is small, the repeatability is high, the sample yield and purity are ensured, and the method is suitable for large-scale industrial production. In addition, as a strong adsorption material of polysulfide, the WSe2 nanomaterial has good application prospect in the battery field.

Description

Technical Field

[0001] This invention relates to a method for preparing tungsten diselenide (WSe2) nanomaterials and its application, belonging to the technical field of inorganic nanomaterial preparation. Background Technology

[0002] Tungsten diselenide (WSe2), a typical transition metal chalcogenide (TMD), has important applications in industrial manufacturing, optoelectronic devices, new energy sources, and aerospace due to its graphene-like layered structure. Because the WSe2 molecules are bound by Se-W-Se covalent bonds within their layers and by weak van der Waals bonds between layers, it readily exhibits interlayer lateral slip under shear stress, making it suitable as a high-performance solid lubricant additive and widely used in industrial production. Since WSe2 has a band gap in the visible light region, it can be used to develop novel solar cells. WSe2's thermal conductivity is approximately one hundred-thousandth that of diamond, the material with the highest thermal conductivity, making it the material with the lowest thermal conductivity in the world. Studies by CatalinChiritescu et al. (Science, 2007, 315:351-353) have shown that its thermal conductivity exhibits anisotropy in both horizontal and vertical directions; therefore, WSe2 can be used as a special thermal insulation material in aerospace and other fields. Furthermore, elemental tungsten has a high melting point, the highest among all alloys / metals, making it difficult to form compounds with low-melting-point selenium. Therefore, current methods for preparing WSe2 suffer from several problems, such as complex processes, cumbersome steps, long production cycles, poor reproducibility, expensive equipment, demanding conditions, high preparation difficulty, and excessive costs. These issues hinder the acquisition and practical application of WSe2 nanomaterials. Summary of the Invention

[0003] This invention provides a simple, rapid, stable, reproducible, and environmentally friendly preparation method. WSe2 nanomaterials are prepared using a direct current arc plasma discharge method and applied to polysulfide adsorbent materials, overcoming the shortcomings of existing preparation methods.

[0004] The preparation method has the following advantages: First, the preparation of WSe2 nanomaterials using DC arc plasma discharge is simple, convenient, and has a short preparation cycle, enabling large-scale production; second, the prepared WSe2 nanomaterials have high purity, high crystallinity, and uniform dispersion; finally, the preparation method is stable and has good repeatability, ensuring the consistency of the quality and performance of the prepared WSe2 nanomaterials, and exhibiting strong adsorption of polysulfides.

[0005] The specific technical solution of this invention is as follows:

[0006] 1. Mix high-purity tungsten (W) powder and selenium (Se) powder evenly according to a molar ratio of 1:2.

[0007] 2. The above mixture is placed in a tablet press and pressed into cylindrical blocks with a height of 1-3 mm and a diameter of 10 mm.

[0008] 3. Embed the block material into the anode graphite pot. The cathode tungsten rod is positioned to the left of the horizontally placed reaction chamber, coinciding with the horizontal axis of the center of the anode graphite pot on the right. Adjust the distance between the anode and cathode to an appropriate position. Place a double-layered cylindrical condenser wall sleeve inside the reaction chamber, covering the cathode tungsten rod and the anode graphite pot. Circulate cooling water through the condenser wall sleeve.

[0009] 4. Injecting circulating cooling water into the anode and cathode and the condenser sleeve of the water-cooling system can effectively reduce the temperature inside the reaction chamber and prevent damage to the equipment caused by the high temperatures generated during the reaction. Simultaneously, closing the sealed door of the reaction chamber, evacuating the chamber pressure to below 10 Pa, and purging the gas at least twice before introducing argon protective gas can effectively remove oxygen and water vapor from the reaction chamber, avoiding their influence on the reaction products. During DC arc plasma discharge, high temperatures are generated inside the reaction chamber. Due to the effect of the circulating cooling water in the condenser sleeve, a temperature gradient is created between various parts of the reaction chamber and the arc discharge region, which is crucial for the preparation of WSe2 nanomaterials.

[0010] 5. Set the current range to 60A-140A, and after the arc discharge reaction lasts for 5-10 minutes, cut off the power supply and continue cooling and passivation for 2-6 hours to room temperature. WSe2 nanomaterials are obtained at the condenser wall sleeve and graphite pot.

[0011] 6. The preparation of the sulfur-containing Li₂S₆ solution was carried out entirely in an argon-protected glove box. First, 1,2-dimethoxyethane (DME) and 1,3-dioxolane (DOL) were mixed at a volume ratio of 1:1. Then, sulfur powder and lithium sulfide (Li₂S) were added to the DOL / DME mixture at a molar ratio of 5:1. After sealing, the mixture was stirred at 60°C for 12 hours to obtain the Li₂S₆ solution. This solution was used as the adsorption testing environment for WSe₂ nanomaterials.

[0012] The preparation method provided by this invention has advantages such as simple preparation process, high stability, rapid reaction, and good reproducibility. Compared with the prior art, this invention can obtain WSe2 nanomaterials in one step, avoiding the cumbersome multiple processing and subsequent steps required in traditional preparation methods, thus improving preparation efficiency and the feasibility of large-scale production of WSe2 nanomaterials. Furthermore, adsorption tests show that WSe2 nanomaterials have a strong adsorption capacity for polysulfides. Therefore, this invention has significant progressive effects and broad application prospects. Attached Figure Description

[0013] Figure 1Schematic diagram of a DC arc plasma discharge device.

[0014] Figure 2 X-ray diffraction (XRD) spectrum of WSe2 nanomaterials.

[0015] Figure 3 Scanning electron microscope (SEM) images of different collection sites under the same experimental conditions.

[0016] Figure 4 Selected area electron spectroscopy (EDS) analysis of WSe2 nanomaterials.

[0017] Figure 5 Scanning electron microscope (SEM) images of the same collection site under different experimental conditions.

[0018] Figure 6 Polysulfide adsorption test of WSe2 nanomaterials. Detailed Implementation

[0019] To make the essential features of the present invention easier to understand, the embodiments are further described in detail with reference to the following drawings and descriptions. However, the following descriptions and explanations of the embodiments do not constitute any limitation on the scope of protection of the present invention.

[0020] Figure 1 This is a schematic diagram of a DC arc plasma discharge device. Except for the cathode tungsten rod and the anode graphite pot, 1 is the outer cavity of the reaction chamber, 2 and 3 are the inlet and outlet of the outer cavity circulating cooling water, 4 is the inner condenser wall sleeve, 5 and 6 are the inlet and outlet of the inner condenser wall sleeve, and 7 and 8 are the inlet and outlet of the anode system cooling water.

[0021] Example 1: Preparation of WSe2 nanomaterials with different micromorphologies from different collection sites under the same experimental conditions

[0022] High-purity tungsten (W) powder and selenium (Se) powder were uniformly mixed at a molar ratio of 1:2. The mixture was placed in a tablet press and pressed into cylindrical blocks with a height of 2.5 mm and a diameter of 10 mm. The blocks were embedded in the anode graphite pot, with the cathode tungsten rod positioned horizontally to the left of the reaction chamber, coinciding with the horizontal axis of the anode graphite pot on the right. The distance between the anode and cathode was adjusted to approximately 20 mm. A double-layered cylindrical condenser sleeve was placed inside the reaction chamber, covering the cathode tungsten rod and the anode graphite pot. Circulating cooling water was circulated inside the double-layered cylinder. Circulating cooling water was introduced into the water-cooling system, the airtight door of the reaction chamber was closed, and the gas pressure inside the chamber was evacuated to below 10 Pa. After purging at least twice, argon gas was introduced to raise the gas pressure to 30 kPa and maintain it at that level. The operating current was set to 100 A, and the arc discharge reaction was initiated for 5 minutes. The power was then cut off, and the chamber was allowed to continue cooling and passivation for 2 hours to room temperature. Pure WSe2 nanomaterials were obtained above the cathode tungsten rod at the condenser sleeve and the graphite pot.

[0023] In order to characterize the structure and physical properties of the product obtained in this invention, Figure 2 X-ray diffraction (XRD) spectra of WSe2 nanomaterials prepared at the condenser wall sleeve under 30 kPa-100 A conditions are presented. All diffraction peak positions of the sample perfectly match those of the JCPDS No. 38-1388 standard spectrum. The diffraction crystal planes are marked in the figure, indicating a hexagonal crystal system. The slightly broadened full width at half maximum (FWHM) of the diffraction peaks indicates a small sample size. Simultaneously, the symmetrical and smooth peak shapes and straight baselines indicate good crystallinity of the obtained sample. No other impurity peaks are visible in the diffraction pattern, indicating that the obtained sample is pure and uncontaminated.

[0024] Figure 3 Scanning electron microscope (SEM) images of WSe2 nanomaterials prepared under the same experimental conditions of 30 kPa-100 A, obtained in a condenser wall sleeve and a graphite pot, are presented. Figure a shows the WSe2 nanomaterials prepared in the condenser wall sleeve, whose structural unit is a multilayer of WSe2 hexagonal nanosheets with uniform morphology, good dispersion, and smooth surface. The sheet thickness is approximately 20 nm, with the thinnest part only a few nanometers. Figure b shows the WSe2 nanomaterials prepared in the graphite pot, which mostly consist of hexagonal sheet structural units with significantly increased sheet thickness. The overall structure is granular, with an average particle size of approximately 103 nm.

[0025] Figure 4 Table 1 shows the selected area electron spectroscopy (EDS) spectra and test results of the WSe2 nanomaterials. As can be seen from the figures, the WSe2 nanomaterials are composed of only W and Se elements, with an atomic ratio close to 1:2, which is in good agreement with the data obtained from XRD.

[0026] Table 1. Selected Area Electron Spectroscopy (EDS) Analysis and Results of WSe2 Nanomaterials

[0027] element Line type Apparent concentration k ratio Atomic percentage W M-line system 191.14 1.91139 40.65 Se L-line system 155.99 1.55988 59.35 Total 100

[0028] Example 2: Preparation of WSe2 nanomaterials with different micromorphologies from the same collection sites under different experimental conditions

[0029] Under the conditions of a reaction pressure of 10 kPa and an operating current of 140 A, with other experimental parameters remaining unchanged, WSe2 nanomaterials were obtained in a graphite pot. Figure 5 Scanning electron microscope (SEM) images of WSe2 nanomaterials prepared in a graphite pot under different experimental conditions are presented. Figure 3 After comparison, it can be clearly seen that the prepared WSe2 nanomaterials are rice-grain shaped, about 200 nm long and about 50 nm in diameter, with an aspect ratio of about 4:1.

[0030] WSe2 nanomaterials with different microstructures can be obtained under argon gas pressure of 10kPa-50kPa and working current of 60A-140A.

[0031] Example 3: Polysulfide Adsorption Test of WSe2 Nanomaterials

[0032] When 20 mg of WSe2 nanomaterials obtained in a graphite pot under 30 kPa-100 A conditions were added to a 0.02 M Li2S6 solution and allowed to stand for 24 h, the solution containing WSe2 nanomaterials was significantly lighter in color than the pure Li2S6 solution. Figure 6 The comparison images and corresponding UV-Vis absorption spectra of Li₂S₆ solutions with and without WSe₂ nanomaterials after 24 h are shown. The experimental results indicate that the Li₂S₆ content in the solution containing WSe₂ nanomaterials is lower, suggesting that WSe₂ nanomaterials have a strong adsorption capacity for Li₂S₆ molecules and can effectively suppress the shuttle effect of polysulfides. This provides important guidance for the application of WSe₂ nanomaterials in the battery field.

[0033] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, all modifications and improvements made by those skilled in the art to the technical solutions within the scope of the present invention or equivalent to the scope of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing a tungsten diselenide nanomaterial, characterized in that: The WSe2 nanomaterial is prepared by a direct current arc plasma method, a mixture of high-purity tungsten powder and selenium powder with a molar ratio of 1:2 is used as raw material, the anode graphite pot and the cathode tungsten rod are horizontally placed and the axes are coincided, under the protection of water cooling system and argon atmosphere, the reaction gas pressure is 10-50 kPa, the working current is 60-140 A, after the arc reaction and cooling passivation, the WSe2 nanomaterial is obtained at the condensing wall sleeve and the graphite pot.

2. The method for preparing a tungsten diselenide nanomaterial according to claim 1, characterized in that: The WSe2 nanomaterial prepared by the direct current arc plasma method is directly used for the adsorption capacity test of the sulfur-containing Li2S6 solution, and the result shows that the WSe2 nanomaterial has strong adsorption to polysulfides.

3. The method for preparing a tungsten diselenide nanomaterial according to claim 1, characterized in that: In the reaction chamber under the protection of inert gas, the anode graphite pot and the cathode tungsten rod are horizontally placed and the axes are coincided.

4. The method for preparing a tungsten diselenide nanomaterial according to claim 1, characterized in that: When the direct current arc plasma is discharged, high temperature is generated in the reaction chamber, and due to the effect of the circulating cooling water in the condensing wall sleeve, a temperature gradient is generated between the reaction chamber and the arc electrodes, which is the key to prepare the WSe2 nanomaterial.

5. The method for preparing a tungsten diselenide nanomaterial according to claim 1, characterized in that: The purity of the tungsten powder, the selenium powder and the argon gas is kept above 99.99%.

6. The use of a tungsten diselenide nanomaterial according to claim 1, characterized in that: The preparation of the sulfur-containing Li2S6 solution is carried out in the glove box under the protection of argon, 1,2-dimethoxyethane (DME) and 1,3-dioxolane (DOL) are mixed in a volume ratio of 1:1, then sulfur powder and lithium sulfide (Li2S) are added into the mixed solution of DOL / DME in a molar ratio of 5:1, after being sealed, the mixture is stirred at 60 ℃ for 12 h to obtain the Li2S6 solution.

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