Molybdenum disulfide nanosheet and large-scale preparation method thereof

Abstract

The present application relates to a kind of molybdenum disulfide nanosheet and its large-scale preparation method, and the preparation method comprises the following steps: sulfonic acid group precursor is dissolved in water with trinitro-pyrene ultrasonic, hydrothermal reaction is carried out, the initial product is filtered, dialysis and drying, obtain graphene quantum dot powder;Graphene quantum dot powder is mixed with molybdenum disulfide powder and carries out ball milling reaction, centrifugal separation and washing, obtain molybdenum disulfide nanosheet composite sheet.In the ball milling process, graphene quantum dot has abundant surface functional groups, increases the electron density of sulfur atom and molybdenum atom and then controls molybdenum disulfide structure to form nanosheet.Compared with prior art, the preparation method of the present application is simple, low in cost, mild in reaction, small in toxicity and simple in post-processing, can prepare macro (gram level), good quality, colloid state stable molybdenum disulfide nanosheet, the method for preparing nanoscale molybdenum disulfide nanosheet is suitable for both laboratory research and industrial mass production.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of two-dimensional material synthesis, and particularly to a molybdenum disulfide nanosheet and a large-scale preparation method thereof. BACKGROUND

[0002] Molybdenum disulfide (MoS2) is the most representative transition metal dichalcogenide, and has become a promising electrocatalyst for hydrogen evolution applications due to its unique properties, including low cost, high specific surface area and surface reactivity. So far, many preparation strategies for molybdenum disulfide nanosheets have been developed, including solvent-assisted exfoliation, chemical-assisted intercalation exfoliation, solvothermal reaction and chemical vapor deposition. In the liquid-assisted exfoliation technology, the presence of surfactants used to stabilize MoS2 will hinder its electrical conductivity, thereby limiting its electrocatalytic performance. The chemical-assisted intercalation technology is also limited in application due to the prolonged reaction time of several days, and strict reaction conditions. Although the solvothermal method can produce high-quality MoS2 nanosheets, they also have disadvantages, such as uncontrolled product layer number, and the need for high-pressure synthesis conditions. Therefore, it is urgent to explore the large-scale preparation of easily prepared, high-yield MoS2 nanosheets. Due to its inherent simplicity, scalability, cost-effectiveness and environmental compatibility, ball milling has become a widely used technology for large-scale synthesis of catalytic materials, which benefits from the synergy between chemical exfoliation and mechanical shear force to overcome the limitations associated with existing methods. In the ball milling process using N-methyl pyrrolidone as an exfoliating agent, the hindrance of complex post-treatment and crystallization steps leads to reduced efficiency, reduced yield and damaged product quality. Therefore, it is crucial to determine a suitable ball milling exfoliating agent in solving the above challenges.

[0003] Graphene has attracted extensive scientific interest since its discovery due to its unique properties. Specifically, when graphene is reduced to nanometer (nm) size, especially below 10 nm, it behaves as graphene quantum dots (GQDs). GQDs inherit the remarkable properties of both two-dimensional graphene and zero-dimensional quantum dots, and have great application potential. GQDs have become a new star in carbon-based nanomaterials due to their unique properties, such as sufficient active sites and abundant surface functional groups, and have attracted widespread attention in the field of electrocatalysis. In addition, functionalized GQDs have the characteristics of large specific surface energy and small size, which can effectively open the interlayer spacing of two-dimensional layered materials, and are conducive to the formation of nanosheets.

[0004] However, the preparation strategies of MoS2 nanosheets, including solvent-assisted exfoliation, chemical-assisted intercalation exfoliation, solvothermal reaction and chemical vapor deposition, have application limitations such as low yield or poor quality. For example, the presence of surfactants in the liquid-assisted exfoliation technique hinders the conductivity of the product, and the harsh reaction conditions in the chemical-assisted intercalation technique and the high-pressure synthesis conditions in the solvothermal method to some extent limit the large-scale preparation of MoS2 nanosheets.

[0005] Therefore, it is urgent to develop a large-scale preparation method of MoS2 nanosheets to realize the rapid, efficient, low-cost and large-scale preparation of MoS2 nanosheets. SUMMARY

[0006] The purpose of the present application is to overcome the defects of the prior art and provide a MoS2 nanosheet and a large-scale preparation method thereof. The preparation method is a graphene quantum dot-assisted ball milling method for synthesizing MoS2 nanosheets. The graphene quantum dots act as an exfoliating agent in the ball milling preparation process to control the electron cloud density of Mo and S atoms of the MoS2 nanosheets and promote the formation of two-dimensional materials, thereby realizing the rapid, low-cost and large-scale preparation of two-dimensional MoS2 nanosheets.

[0007] The purpose of the present application can be achieved by the following technical solutions:

[0008] The first purpose of the present application is to provide a large-scale preparation method of MoS2 nanosheets. The preparation method is a graphene quantum dot-assisted ball milling method. The preparation method comprises the following steps:

[0009] S1, sulfonic acid-based precursor and trinitro-pyrene are ultrasonically dissolved in deionized water to obtain a mixed solution, and the reaction is carried out in a reaction kettle. The primary product is filtered, dialyzed and dried to obtain a solid powder of graphene quantum dots as sulfonic acid-based functionalized graphene quantum dots;

[0010] S2, the sulfonic acid-based functionalized carbon quantum dot powder obtained in step S1 is mixed with MoS2 powder for ball milling reaction, and ethanol is used for centrifugal separation and washing, and finally MoS2 nanosheet material is obtained.

[0011] Further, in step S1, the sulfonic acid-based precursor is selected from one of sodium sulfite, naphthylamine-4-sodium sulfonate, 4-aminobenzenesulfonic acid, 4-hydroxybenzenesulfonic acid and 1-amino-2-naphthol-4-sulfonic acid.

[0012] Further, in step S1, the addition amount of the sulfonic acid-based precursor is 100-1000 mg.

[0013] Further, in step S1, the reaction in the reaction kettle is specifically transferring 20-60 ml of the mixed solution into the reaction kettle for reaction, the heating temperature is 150-300 DEG C, and the heating time is 6-30 h.

[0014] Further, in step S1, the drying temperature of the initial product is not higher than 40-80 DEG C.

[0015] Further, in step S2, the added amount of the molybdenum disulfide precursor is 500-1500 mg.

[0016] Further, in step S2, the added amount of the sulfonic acid functionalized graphene quantum dot is 10-300 mg.

[0017] Further, in step S2, the ball milling reaction is carried out at a rotation speed of 1000-1800 r / min for 6-30 h.

[0018] Further, a dry ball miller can be used for dry milling.

[0019] Further, in step S2, the centrifugal separation is carried out at a rotation speed of 8000-12000 r / min for 1-20 min.

[0020] A second object of the present application is to provide a large-scale preparation method of molybdenum disulfide nanosheets, wherein the MoS2 nanosheet material is obtained by the above preparation method, and the average thickness of the molybdenum disulfide nanosheet material is not more than 20 nm.

[0021] Compared with the prior art, the present application has the following beneficial effects:

[0022] 1) The large-scale preparation method of molybdenum disulfide nanosheet material provided by the present application is based on dry ball milling, which is simple, low-cost, mild, simple to handle, and eliminates the dependence on organic solvents, meeting the needs of scalable mass production.

[0023] 2) In the method of the present application, graphene quantum dots as a peeling agent in the ball milling process are of great significance for opening the interlayer spacing of layered materials and constructing nanosheet structures.

[0024] 3) The molybdenum disulfide nanosheet material provided by the present application has extremely high yield (up to 63%), good quality and stable colloidal state, and the method is suitable for industrialized mass production of MoS2 nanosheet material of nanometer size.

[0025] 4) The molybdenum disulfide nanosheet material provided by the present application is single-layer or few-layer, and has an average thickness of about 4 nm. Compared with MoS2 powder, the near-single-layer molybdenum disulfide nanosheet has better catalytic activity due to its high specific surface area and surface activity, and exhibits excellent performance in HER catalysis, showing a low potential of 270 mV at a current density of 10 mA·cm -2 , and also exhibits excellent long-term durability, maintaining its catalytic activity for nearly 200 hours. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 It is a transmission electron microscope image of the MoS2 nanosheet material in Example 1 of the present application.

[0027] Figure 2 It is an atomic force microscope image of the MoS2 nanosheet material in Example 1 of the present application.

[0028] Figure 3 It is an XRD spectrum of the MoS2 nanosheet in Example 1 of the present application and the original MoS2 powder.

[0029] Figure 4 It is a physical picture of the MoS2 nanosheet (right) in Example 1 of the present application and the original MoS2 powder (left) dissolved in isopropanol solvent for two days.

[0030] Figure 5 It is a transmission electron microscope image of the MoS2 powder in the comparative example.

[0031] Figure 6 It is a polarization curve graph of the MoS2 nanosheet in Example 1 of the present application, the MoS2 powder in the comparative example and the commercial catalyst PtC. DETAILED DESCRIPTION

[0032] The present application will be described in detail below in conjunction with the drawings and specific examples. The following examples will help those skilled in the art to further understand the present application, but do not limit the present application in any form. It should be noted that for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made. These all belong to the protection scope of the present application.

[0033] In the technical solution, if the preparation means, materials, structure or composition ratio and other features are not explicitly stated, they are considered as common technical features disclosed in the prior art.

[0034] In the following examples, the raw materials used are commercially available, wherein the purity of the commercially available molybdenum disulfide powder is 99.9%, and the PtC catalyst is purchased from Aldrich Reagent Co., Ltd.

[0035] In the following examples, the ball milling is performed using a GT300 ball mill.

[0036] The large-scale preparation method of the MoS2 nanosheet in the present application comprises the following steps:

[0037] S1, dissolving sulfonic acid group precursor and trinitro-pyrene in deionized water under ultrasonic wave to obtain a mixed solution, reacting in a reaction kettle, filtering, dialyzing and drying the initial product to obtain a solid powder of graphene quantum dots as sulfonic acid group functionalized graphene quantum dots;

[0038] S2, mixing the sulfonic acid group functionalized graphene quantum dot powder obtained in step S1 with commercially available molybdenum disulfide powder for ball milling reaction, centrifuging and washing with ethanol to finally obtain a molybdenum disulfide nanosheet material.

[0039] The applicant's thought process is as follows: So far, the preparation strategies of molybdenum disulfide nanosheets include solvent-assisted exfoliation, chemical-assisted intercalation exfoliation, solvothermal reaction and chemical vapor deposition, all of which have application limitations such as low yield or poor quality. For example, the presence of surfactants in the liquid-assisted exfoliation technique hinders the conductivity of the product, and the harsh reaction conditions in the chemical-assisted intercalation technique and the high-pressure synthesis conditions in the solvothermal method to some extent limit the large-scale preparation of MoS2 nanosheets. In order to improve this problem, graphene quantum dots are added to assist in the ball milling synthesis of MoS2 nanosheets. Graphene quantum dots act as exfoliating agents in the preparation process, regulate the electron cloud density of molybdenum and sulfur atoms of MoS2 nanosheets, and promote the formation of two-dimensional materials, which can realize the rapid, low-cost and large-scale preparation of two-dimensional MoS2 nanosheets.

[0040] Example 1

[0041] In this embodiment, a MoS2 nanosheet material is provided, and the preparation method thereof comprises the following steps:

[0042] S1, dissolving 500 mg of sulfonic acid group precursor and 200 mg of trinitro-pyrene in deionized water under ultrasonic wave to obtain a mixed solution, reacting in a polytetrafluoroethylene reaction kettle at 160℃ for 12 h, filtering and dialyzing the initial product, and drying the initial product at 60℃ to obtain a solid powder of sulfonic acid group functionalized graphene quantum dots;

[0043] S2, the sulfonic acid group functionalized graphene quantum dots solid powder (100 mg) obtained in step S1 was mixed with commercial molybdenum disulfide powder (1000 mg) for ball milling reaction, the rotation speed of ball milling was 1600 r / min, the reaction time was 10 h, and the ethanol was used for centrifugal separation, the rotation speed of centrifugal separation was 8000 r / min, and the centrifugal separation time was 10 min. Ethanol washing was performed, and finally the molybdenum disulfide nanosheet material was obtained. The mass of the single-layer or few-layer molybdenum disulfide nanosheet material was 630 mg, and the yield was 63%.

[0044] The obtained MoS2 nanosheet material can be applied in the field of electrochemical hydrogen production.

[0045] The test analysis is as follows:

[0046] The field emission transmission electron microscope was used to measure the MoS2 nanosheet material map prepared in step S2 in this embodiment 1, and it was found that the MoS2 nanosheet was thin and the lattice fringe was clear, which proved the successful synthesis of the MoS2 nanosheet material, as shown in Figure 1 As shown in Figure 2 , the AFM image of the product obtained in step S2 in Example 1 was tested by atomic force microscope, and it was found that the average thickness of the two-dimensional MoS2 nanosheet material was 4 nm. Figure 3 The XRD pattern of the MoS2 nanosheet material obtained in Example 1 was shown, and it was found that the characteristic peaks of the obtained product had good coincidence with the characteristic peaks of the standard card JCPDS No. 037-1492, which proved the successful synthesis of MoS2. Figure 4 The physical map of the MoS2 nanosheet (right) in Example 1 and the original MoS2 powder (left) dissolved in isopropanol solvent for two days was shown, and the obvious Tyndall effect proved the uniform dispersion in the solution, in addition, compared with the MoS2 powder, the stability of the synthesized MoS2 nanosheet in isopropanol solvent was significantly enhanced. As shown in Figure 5 The transmission electron microscope map showed that the MoS2 powder synthesized without adding sulfonic acid group functionalized graphene quantum dots was in the form of nanosheet stacking. Figure 6 The polarization curve map of the MoS2 nanosheet in Example 1, the MoS2 powder in the comparative example and the commercial catalyst PtC in the present application was shown. The synthesized MoS2 nanosheet showed excellent HER activity, and had an overpotential of about 270 mV at 10 mA cm -2

[0047] Comparative example

[0048] This comparative example is basically the same as the above-mentioned Example 1, the difference is that:

[0049] ​In the synthesis of MoS2 material, no functionalized graphene quantum dots are added to the ball milling reaction, and finally MoS2 powder material is prepared.

[0050] Example 2

[0051] In this embodiment, a MoS2 nanosheet material is provided, and the preparation method thereof comprises the following steps:

[0052] S1, 100 mg of sulfonic acid precursor and 500 mg of trinitro-pyrene are ultrasonically dissolved in deionized water to obtain a mixed solution, and the initial product is filtered and dialyzed in a polytetrafluoroethylene reaction kettle at 180°C for 20h, and the initial product is dried at 60°C to obtain a solid powder of graphene quantum dots as sulfonic acid functionalized carbon quantum dots;

[0053] S2, the functionalized graphene quantum dot powder (200 mg) obtained in step S1 is mixed with commercial molybdenum disulfide powder (1500 mg) for ball milling reaction, the ball milling speed is 1600 r / min, the reaction time is 10h, and the ethanol is centrifuged, wherein the centrifugal speed is 10000 r / min, and the centrifugal time is 15 min. Washing, finally obtain MoS2 nanosheet material.

[0054] Example 3

[0055] In this embodiment, a carbon quantum dot / MoS2 nanosheet composite material is provided, and the preparation method thereof comprises the following steps:

[0056] S1, 1000 mg of sulfonic acid precursor and 100 mg of trinitro-pyrene are ultrasonically dissolved in deionized water to obtain a mixed solution, and the initial product is filtered and dialyzed in a polytetrafluoroethylene reaction kettle at 180°C for 20h, and the initial product is dried at 60°C to obtain a solid powder of graphene quantum dots as sulfonic acid functionalized carbon quantum dots;

[0057] S2, the functionalized carbon quantum dot powder (300 mg) obtained in step S1 is mixed with commercial molybdenum disulfide powder (2000 mg) for ball milling reaction, the ball milling speed is 1000 r / min, the reaction time is 8h, and the ethanol is centrifuged, wherein the centrifugal speed is 12000 r / min, and the centrifugal time is 20 min. Washing, finally obtain MoS2 nanosheet material.

[0058] The preparation method in the above-mentioned examples 1-3 and comparative examples can prepare MoS2 nanosheet material, that is, the graphene quantum dot assisted synthesis of two-dimensional MoS2 nanosheet, and belongs to the technical field of novel two-dimensional material synthesis. The comparative examples do not prepare composite materials containing graphene quantum dots, and cannot play the role of graphene quantum dots as a peeling agent and a structure regulator in the use process, which is not conducive to promoting the formation of two-dimensional materials. The above-mentioned example 1 uses a molecular fusion method to synthesize graphene quantum dots, and uses the graphene quantum dots as an auxiliary peeling agent to prepare two-dimensional MoS2 nanosheet (MoS2 nanosheet material) with a thickness of 4 nm at room temperature with MoS2 powder. The synthesis method of the above-mentioned examples is simple and easy to operate, the reaction is mild, the toxicity is small, the post-treatment is simple, the yield of the prepared molybdenum disulfide is high, the quality is good, and the structure is stable. This safe and low-cost nanosheet large-scale synthesis strategy has an enlightening significance for the industrialized preparation of layered materials for energy conversion systems.

[0059] The above description of the examples is for the purpose of enabling and using the invention for those of ordinary skill in the art. Those skilled in the art can easily make various modifications to the examples, and apply the general principles described herein to other examples without creative labor. Therefore, the present application is not limited to the above-mentioned examples, and the improvements and modifications made by those skilled in the art according to the disclosure of the present application without departing from the scope of the present application should be within the scope of protection of the present application.

Claims

1. A method for large-scale preparation of molybdenum disulfide nanoplatelets, characterized in that, The preparation method comprises the following steps: S1, dissolving sulfonic acid group precursor and trinitro-pyrene in deionized water by ultrasonic, obtaining a mixed solution, reacting in a reaction kettle, filtering, dialysis and drying the initial product to obtain a solid powder of graphene quantum dots, as sulfonic acid group functionalized graphene quantum dots; S2, mixing and ball-milling the sulfonic acid group functionalized graphene quantum dots powder obtained in step S1 with molybdenum disulfide powder, centrifuging with ethanol, washing, and finally obtaining molybdenum disulfide nanosheet material.

2. The method of claim 1, wherein the method is characterized by, In step S1, the sulfonic acid group precursor is selected from one of 4-aminobenzenesulfonic acid and 1-amino-2-naphthol-4-sulfonic acid.

3. The method of claim 1, wherein the method is characterized by, In step S1, the addition amount of the sulfonic acid group precursor is 100-1000 mg.

4. The method of claim 1, wherein the method is characterized by, In step S1, the reaction in the reaction kettle is specifically transferring 20-60 ml of the mixed solution to the reaction kettle for reaction, the heating temperature is 150-300℃, and the heating time is 6-30 h.

5. The method of claim 1, wherein the method is characterized by, In step S1, the drying temperature is 40-80℃.

6. The method of claim 1, wherein the method is characterized by, In step S2, the addition amount of the molybdenum disulfide precursor is 500-1500 mg. 7.The method of claim 1, wherein the molybdenum disulfide nanoplatelets are prepared in a large scale. In step S2, the addition amount of the sulfonic acid group functionalized graphene quantum dots is 10-300 mg. 8.The method of claim 1, wherein the method is characterized by, In step S2, the ball-milling reaction, the ball-milling rotation speed is 1000-1800 r / min, and the reaction time is 6-30 h. 9.The method of claim 1, wherein the molybdenum disulfide nanoplatelets are prepared in a large scale. In step S2, the centrifugal separation rotation speed is 8000-12000 r / min, and the centrifugal separation time is 1-20 min.

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