Method for synthesizing metastable-phase molybdenum disulfide based on eutectic solvent and water system

Abstract

The invention discloses a method for synthesizing metastable-phase molybdenum disulfide based on a deep eutectic solvent (DES) and a water system, and aims to provide a simple and low-cost method for synthesizing the metastable-phase molybdenum disulfide, and high-quality metastable-phase molybdenum disulfide can be prepared at lower input cost by optimizing reaction conditions and a reaction system. Compared with the traditional method, the process provided by the invention has mild reaction conditions, low raw material cost and simple operation steps, not only effectively reduces the production cost, but also improves the feasibility and repeatability of operation. According to the method, the morphology, the size and the dispersity of the metastable-phase molybdenum disulfide micro-nano sheet layer can be accurately regulated and controlled, and the performance stability of the product in different applications is ensured. By controlling the size and dispersion degree of the lamellas, the dependence on expensive noble metal (such as platinum) catalysts can be reduced to a certain extent, and a more economical and efficient alternative scheme is provided for the fields of catalysis, energy storage and the like.

Description

Technical Field

[0001] The invention belongs to the field of transition metal sulfides, and specifically relates to a method for synthesizing metastable phase molybdenum disulfide based on a low eutectic solvent and water system. Background Art

[0002] With the continuous increase in global fossil fuel consumption, environmental problems and energy crises have become increasingly severe. The development and utilization of renewable energy has become the key to solving global energy problems. Among them, hydrogen is considered to be one of the ideal carriers of future energy due to its high energy density, zero carbon emissions and renewability. Water electrolysis is one of the important ways to obtain hydrogen fuel and an important way to obtain clean and scalable energy alternatives. Water electrolysis can directly produce hydrogen, which involves the hydrogen evolution reaction (HER), and catalysts are required to improve the conversion efficiency. Precious metal and its oxide electrocatalysts such as IrO2, RuO2 and Pt / C are considered to be standard catalysts with excellent performance in HER. However, their small reserves and high costs have greatly hindered their widespread application.

[0003] Two-dimensional molybdenum disulfide (MoS2) has many advantages such as abundant sources and low cost. In particular, the metastable phase MoS2 shows typical metallic properties and has more unsaturated edge sites. As a catalyst for hydrogen evolution in water electrolysis, it is one of the most promising materials that can replace Pt-based precious metal catalysts.

[0004] The currently developed methods for preparing metastable molybdenum disulfide can be divided into two categories: Top-Down and Bottom-Up. However, the Top-Down method often requires the use of low-boiling organic solvents, harsh conditions and complex steps, with low efficiency and poor environmental protection. The liquid phase chemical method in the Bottom-Up method requires harsh conditions, complex steps, and most importantly, a suitable solvent. Low eutectic solvent (DES) green solvent has the characteristics of simple synthesis, low cost, conductivity, and green environmental protection. It is a new type of green solvent and multifunctional material that is widely studied and applied in the chemical industry. It has great potential as a suitable solvent required for liquid phase chemical methods.

[0005] In view of this, the present invention is proposed. Summary of the invention

[0006] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a method for synthesizing metastable phase molybdenum disulfide based on a low eutectic solvent and a water system, thereby solving the problems raised in the above-mentioned background technology.

[0007] In order to solve the above technical problems, the basic concept of the technical solution adopted by the present invention is: A method for synthesizing metastable phase molybdenum disulfide based on a deep eutectic solvent and water system comprises the following steps: S1: selecting at least one hydrogen bond donor (HBD) and at least one hydrogen bond acceptor (HBA), adjusting the ratio of HBD to HBA to form a deep eutectic solvent (DES), and then mixing the DES with deionized water in a predetermined ratio to obtain a DES / water mixed solution, wherein the ratio of the DES / water mixed solution ranges from 0% to 100% of water; S2: dissolving a molybdenum source and a sulfur source in the DES / water mixture prepared in step S1 to obtain a solution; S3: adding a surfactant to the solution in step S2 and stirring it thoroughly to dissolve it; S4: treating the solution through a reaction mechanism to react the molybdenum source and the sulfur source under required temperature and time conditions; S5: After the reaction is completed, the mixture is cooled naturally to room temperature, the product is separated by centrifugation, washed with deionized water and anhydrous ethanol, and finally dried to obtain lamellar metastable phase molybdenum disulfide. The drying method includes but is not limited to natural drying, freeze drying or vacuum drying.

[0008] Optionally, the combination types of HBD and HBA in step S1 include but are not limited to: The chemical composition of DES is usually represented by the general formula Cat + X - zY indicates that Cat + represents a cation belonging to the ammonium, phosphonium or sulfonium group, X represents a Lewis base, Y represents a Lewis acid, and z represents the stoichiometric ratio between the two.

[0009] Type I DES (Cat + X - MCl X : Metal salts and organic salts, M can be Zn, Sn, Fe, etc.): for example, choline chloride + zinc chloride; Type II DES (Cat + X - MCl X yH2O: metal salt hydrates and organic salts, M can be CONH2, COOH, OH, etc.): for example, choline chloride + cobalt chloride hexahydrate; Type III DES (Cat + X - RZ: HDB and organic salt, Z can be CONH2, COOH, OH, etc.): for example, choline chloride + urea; Type IV DES (MCl X +RZ: metal salt hydrate and HBD, M can be Zn, Al, etc., Z can be CONH2, OH, etc.): for example, zinc chloride + urea; Type V (non-ionic: HBA molecules and HBD molecules): for example, thymol + menthol.

[0010] Optionally, the molybdenum source in step S2 includes but is not limited to: sodium molybdate, ammonium molybdate, ammonium thiomolybdate, molybdenum dioxide, molybdenum trioxide, molybdenum phthalocyanine, molybdenum citrate, and a molybdenum-carbon complex.

[0011] Optionally, the sulfur source in step S2 includes but is not limited to: sodium sulfide, sodium sulfite, thiourea, L-cysteine, sulfur powder, and hydrogen sulfide gas.

[0012] Optionally, in step S3, the surfactant concentration range is 0 to 0.1 g / ml, and the surfactant includes but is not limited to: cationic surfactants, anionic surfactants, nonionic surfactants and amphoteric surfactants, for example: one or a combination of two or more of polyvinyl pyrrolidone, polyvinyl alcohol, Tween-80, Span-60, cetyltrimethylammonium chloride, sodium lauryl sulfate, cocamidopropyl betaine, etc.

[0013] Optionally, the reaction mechanism in step S4 includes but is not limited to: hydrothermal reaction, oil bath reaction or microwave reaction, wherein, when using hydrothermal reaction, first, the solution obtained in step S3 is transferred to a closed polytetrafluoroethylene reactor, and reacted at 180°C to 280°C for 1 hour to 30 hours, with a stirring speed of 0 to 200 rpm.

[0014] Optionally, when using an oil bath reaction, first, transfer the solution obtained in step S3 to a closed reactor equipped with a condensation reflux device, heat in an oil bath to maintain a constant temperature, and react at 80°C to 150°C for 1 to 30 hours with a stirring speed of 0 to 200 rpm.

[0015] Optionally, when using microwave reaction, first, transfer the solution obtained in step S3 to a sealed microwave reaction vessel and heat it at a power of 300 to 1200 W for 1 to 20 minutes. During the reaction, the morphology and crystal form of molybdenum disulfide can be optimized by adjusting the microwave power and time.

[0016] Optionally, in step S5, the particle size of the molybdenum disulfide flake layer ranges from 200 nm to 10 μm, and the thickness ranges from 1 nm to 50 nm.

[0017] It should be noted that the present invention has the following advantages: 1. Raw materials are cheap and readily available: the low eutectic solvents and their hydrogen bond donors and acceptors used are all well available, green and environmentally friendly, and low-cost; 2. The method is simple to operate: the synthesis process is clear and easy to implement; 3. High experimental repeatability: Through precise ratio and process control, high consistency of experimental results can be achieved; 4. Large output and high purity: high-quality metastable phase molybdenum disulfide can be stably obtained, suitable for large-scale application; 5. Wide applicability: The method is not only applicable to the preparation of metastable phase MoS2, but can also be extended to the synthesis of other transition metal sulfides (such as WS2, NbS2, CoS2, etc.), achieving effective regulation of their crystal form, morphology and microstructure. After adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art. Of course, any product implementing the present invention does not necessarily need to achieve all the advantages described below at the same time: 1. The purpose of the present invention is to provide a simple and low-cost method for synthesizing metastable molybdenum disulfide. By optimizing the reaction conditions and reaction system, high-quality metastable molybdenum disulfide can be prepared at a lower investment cost. Compared with the traditional method, the process of the present invention has mild reaction conditions, low raw material costs and simple operation steps, which not only effectively reduces the production cost, but also improves the feasibility and repeatability of the operation. The method can accurately control the morphology, size and dispersity of metastable molybdenum disulfide micro-nano sheets to ensure the performance stability of the product in different applications. By controlling the size and dispersion of the sheets, the present invention can also reduce the dependence on expensive precious metal (such as platinum) catalysts to a certain extent, providing a more economical and efficient alternative for catalysis, energy storage and other fields.

[0018] 2. The present invention provides a method for synthesizing metastable molybdenum disulfide sheets in a deep eutectic solvent (DES) / water system. The method uses a molybdenum source and a sulfur source as reaction raw materials, and synthesizes through a hydrothermal, microwave or oil bath reaction system, and can prepare high-quality metastable molybdenum disulfide micro-nano sheets under controlled conditions. In this process, different types of mixed solutions of DES and water are used to adjust the polarity, reaction rate and solubility of the solvent system, thereby effectively controlling the microscopic morphology of the metastable molybdenum disulfide sheets. By selecting a suitable DES / water ratio and adding a surfactant, the present invention can accurately control the size, dispersibility and interlayer spacing of the molybdenum disulfide sheets. The addition of a surfactant not only promotes the uniform dispersion of the molybdenum disulfide sheets, avoids the agglomeration of particles, but also effectively improves the stability and purity of the product.

[0019] The specific implementation modes of the present invention are further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings described below are only some embodiments. For those skilled in the art, other drawings can be obtained based on these drawings without creative work. In the drawings: Figure 1 It is a scanning electron microscope image of the molybdenum disulfide product obtained in the comparative example of the present invention.

[0021] Figure 2 It is the XRD diffraction pattern of the molybdenum disulfide product obtained in the comparative example of the present invention.

[0022] Figure 3 It is the Raman diffraction pattern of the molybdenum disulfide product obtained in the comparative example of the present invention.

[0023] Figure 4 This is the XRD diffraction pattern of the metastable phase molybdenum disulfide product prepared in Example 1 of the present invention.

[0024] Figure 5 This is the XRD diffraction pattern of the metastable phase molybdenum disulfide product prepared in Example 2 of the present invention.

[0025] Figure 6 This is the XRD diffraction pattern of the metastable phase molybdenum disulfide product prepared in Example 3 of the present invention.

[0026] Figure 7 This is the XRD diffraction pattern of the metastable phase molybdenum disulfide product prepared in Example 4 of the present invention.

[0027] Figure 8 This is a scanning electron microscope image of the metastable phase molybdenum disulfide product prepared in Example 5 of the present invention.

[0028] Fig. 9 This is the XRD diffraction pattern of the metastable phase molybdenum disulfide product prepared in Example 5 of the present invention.

[0029] Fig.10 This is the Raman diffraction pattern of the metastable phase molybdenum disulfide product obtained in Example 5 of the present invention.

[0030] It should be noted that these drawings and textual descriptions are not intended to limit the conceptual scope of the present invention in any way, but are intended to illustrate the concept of the present invention for those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0031] The present invention will now be described in further detail with reference to the accompanying drawings.

[0032] See also Figure 1-10 As shown, in this embodiment, a method for synthesizing metastable phase molybdenum disulfide based on a deep eutectic solvent and a water system is provided, comprising the following steps: S1: selecting at least one hydrogen bond donor (HBD) and at least one hydrogen bond acceptor (HBA), adjusting the ratio of HBD to HBA to form a deep eutectic solvent (DES), and then mixing the DES with deionized water in a predetermined ratio to obtain a DES / water mixed solution, wherein the ratio of the DES / water mixed solution ranges from 0% to 100% of water; S2: dissolving a molybdenum source and a sulfur source in the DES / water mixture prepared in step S1 to obtain a solution; S3: adding a surfactant to the solution in step S2 and stirring it thoroughly to dissolve it; S4: treating the solution through a reaction mechanism to react the molybdenum source and the sulfur source under required temperature and time conditions; S5: After the reaction is completed, the mixture is cooled naturally to room temperature, the product is separated by centrifugation, washed with deionized water and anhydrous ethanol, and finally dried to obtain lamellar metastable phase molybdenum disulfide. The drying method includes but is not limited to natural drying, freeze drying or vacuum drying.

[0033] In this embodiment, the combination types of HBD and HBA in step S1 include but are not limited to: The chemical composition of DES is usually represented by the general formula Cat + X - zY indicates that Cat + represents a cation belonging to the ammonium, phosphonium or sulfonium group, X represents a Lewis base, Y represents a Lewis acid, and z represents the stoichiometric ratio between the two.

[0034] Type I DES (Cat + X - MCl X : Metal salts and organic salts, M can be Zn, Sn, Fe, etc.): for example, choline chloride + zinc chloride; Type II DES (Cat + X - MCl X yH2O: metal salt hydrates and organic salts, M can be CONH2, COOH, OH, etc.): for example, choline chloride + cobalt chloride hexahydrate; Type III DES (Cat + X - RZ: HDB and organic salt, Z can be CONH2, COOH, OH, etc.): for example, choline chloride + urea; Type IV DES (MCl X +RZ: metal salt hydrate and HBD, M can be Zn, Al, etc., Z can be CONH2, OH, etc.): for example, zinc chloride + urea; Type V (non-ionic: HBA molecules and HBD molecules): for example, thymol + menthol.

[0035] In this embodiment, the molybdenum source in step S2 includes but is not limited to: sodium molybdate, ammonium molybdate, ammonium thiomolybdate, molybdenum dioxide, molybdenum trioxide, molybdenum phthalocyanine, molybdenum citrate, and molybdenum-carbon complex.

[0036] In this embodiment, the sulfur source in step S2 includes but is not limited to: sodium sulfide, sodium sulfite, thiourea, L-cysteine, sulfur powder, and hydrogen sulfide gas.

[0037] In this embodiment, the surfactant concentration range in step S3 is 0-0.1 g / ml, and the surfactant includes but is not limited to: cationic surfactants, anionic surfactants, nonionic surfactants and amphoteric surfactants, for example: one or a combination of two or more of polyvinyl pyrrolidone, polyvinyl alcohol, Tween-80, Span-60, cetyltrimethylammonium chloride, sodium lauryl sulfate, cocamidopropyl betaine, etc.

[0038] In this embodiment, the reaction mechanism in step S4 includes but is not limited to: hydrothermal reaction, oil bath reaction or microwave reaction, wherein, when using hydrothermal reaction, first, the solution obtained in step S3 is transferred to a closed polytetrafluoroethylene reactor, and reacted at 180°C to 280°C for 1 hour to 30 hours, with a stirring speed of 0 to 200 rpm.

[0039] In this embodiment, when an oil bath reaction is used, first, the solution obtained in step S3 is transferred to a closed reactor equipped with a condensation reflux device, heated in an oil bath to maintain a constant temperature, and reacted at 80° C. to 150° C. for 1 to 30 hours, with a stirring speed of 200 rpm.

[0040] In this embodiment, when using microwave reaction, first, the solution obtained in step S3 is transferred to a sealed microwave reaction container and heated at a power of 300 to 1200 W for 1 minute to 20 minutes. During the reaction, the morphology and crystal form of molybdenum disulfide can be optimized by adjusting the microwave power and time.

[0041] In this embodiment, the particle size of the molybdenum disulfide flake layer in step S5 is in the range of 200 nm to 10 μm, and the thickness is in the range of 1 nm to 50 nm.

[0042] It should be noted that the above raw materials are all purchased through the existing supply chain.

[0043] Example 1: A method for synthesizing metastable phase molybdenum disulfide based on a type I deep eutectic solvent and water system, comprising the following steps: S1: Choline chloride and zinc chloride are selected as hydrogen bond donors and hydrogen bond acceptors, respectively, and then choline chloride and zinc chloride are mixed in a molar ratio of 1:1, and a type I deep eutectic solvent is obtained after the mixing is completed. After the mixing is completed, the type I deep eutectic solvent is mixed with deionized water in a ratio of 1:4, and a mixed solution A is obtained after the mixing is completed; It should be noted that the proportion of Type I low eutectic solvent is 20%, while the proportion of deionized water is 80%.

[0044] S2: weighing a molybdenum source and a sulfur source in a molar ratio of 1:2 and dissolving them in the mixed solution obtained in step S1, and mixing them evenly to obtain a clear and transparent mixed solution B; S3: adding anionic surfactant sodium dodecyl sulfate (SLS) in a concentration range of 0 to 0.1 g / ml to the mixed solution B prepared in step S2, and stirring to obtain a mixed solution C; S4: transferring the mixed solution C to a polytetrafluoroethylene reactor and reacting at 180° C. for 20 hours; S5: After the reaction is completed, the reaction solution is naturally cooled to room temperature, the reaction container is opened, and deionized water and ethanol are used for centrifugation and washing; S6: The washed product is naturally dried to obtain a black powder.

[0045] Control Example: Type I DES was not used, and only 100% deionized water was used for the reaction. The other steps were the same as those in Example 1.

[0046] Comparative Example 1 shows that Figure 1 This is an electron scanning image of molybdenum disulfide prepared in the control example, showing nanoflowers with a size of 1 μm. Figure 2 This is the XRD diagram of molybdenum disulfide, showing a 1T / 2H mixed crystal phase. Figure 3 The Raman diagram of Example 1 helps illustrate this point. Figure 4 From the XRD diagram of the synthesized molybdenum disulfide with 20% DES addition, it can be observed that the crystal form of the synthesized molybdenum disulfide is transformed into 1T phase and metastable phase, which is a typical 1T phase molybdenum disulfide crystal form, and the 1T phase content is significantly higher than that of the control example.

[0047] Example 2: A method for synthesizing metastable phase molybdenum disulfide based on a type II deep eutectic solvent and water system, comprising the following steps: S1: Choline chloride and cobalt chloride hexahydrate are selected as hydrogen bond donors and hydrogen bond acceptors, respectively, and then choline chloride and cobalt chloride hexahydrate are mixed in a molar ratio of 1:2, and a type II deep eutectic solvent is obtained after the mixing is completed. After the mixing is completed, the type II deep eutectic solvent is mixed with deionized water in a ratio of 1:1, and a mixed solution A is obtained after the mixing is completed; It should be noted that the proportion of type II low eutectic solvent is 50%, and the proportion of deionized water is 50%.

[0048] S2: weighing a molybdenum source and a sulfur source in a molar ratio of 1:4 and dissolving them in the mixed solution A obtained in step S1, and mixing them evenly to obtain a clear and transparent mixed solution B; S3: adding a cationic surfactant, cetyltrimethylammonium chloride (CTAB), in a concentration range of 0 to 0.1 g / ml to the mixed solution B prepared in step S2, and stirring to obtain a mixed solution C; S4: Transfer the mixed solution C to a beaker and heat the reaction at 1000 W (microwave oven) for 2 minutes; S5: After the reaction is completed, the reaction solution is naturally cooled to room temperature, the reaction container is opened, and deionized water and ethanol are used for centrifugation and washing; S6: The washed product is naturally dried to obtain a black powder.

[0049] It can be observed from Example 2 that Figure 5 This is the XRD pattern of molybdenum disulfide prepared in Example 2. Compared with the XRD patterns of solution 1 and solution 2, there are obvious differences, and its crystal form is transformed into metastable phase molybdenum disulfide.

[0050] Example 3: A method for synthesizing metastable phase molybdenum disulfide based on a type III deep eutectic solvent and a water system, comprising the following steps: S1: Choline chloride and urea are selected as hydrogen bond donors and hydrogen bond acceptors, respectively, and then choline chloride and urea are mixed in a molar ratio of 1:4, and a type III deep eutectic solvent is obtained after the mixing is completed. After the mixing is completed, the type III deep eutectic solvent is mixed with deionized water in a ratio of 6.5:3.5, and a mixed solution A is obtained after the mixing is completed; It should be noted that the proportion of type III low eutectic solvent is 65%, while the proportion of deionized water is 35%.

[0051] S2: weighing a molybdenum source and a sulfur source in a molar ratio of 1:6 and dissolving them in the mixed solution A obtained in step S1, and mixing them evenly to obtain a clear and transparent mixed solution B; S3: adding a nonionic surfactant, Tween-80, in a concentration range of 0 to 0.1 g / ml to the mixed solution B prepared in step S2, and stirring to obtain a mixed solution C; S4: reacting the mixed solution C in an oil bath at 120° C. for 30 hours, wherein the stirring speed is 200 rpm; S5: After the reaction is completed, the reaction solution is naturally cooled to room temperature, the reaction container is opened, and deionized water and ethanol are used for centrifugation and washing; S6: The washed product is naturally dried to obtain a black powder.

[0052] It can be observed from Example 3 that Figure 6 The XRD pattern of the molybdenum disulfide prepared in the above embodiment is significantly different from that of the control example, embodiment 1 and embodiment 2, and its crystal form is further transformed into the metastable phase molybdenum disulfide. Figure 4and Figure 5 There has been a decrease.

[0053] Example 4: A method for synthesizing metastable phase molybdenum disulfide based on a type IV deep eutectic solvent and a water system, comprising the following steps: S1: Select zinc chloride and urea as a hydrogen bond donor and a hydrogen bond acceptor, respectively, and then mix the zinc chloride and urea in a molar ratio of 1:6, and obtain a type IV low eutectic solvent after mixing evenly. After mixing, mix the type IV low eutectic solvent with deionized water in a ratio of 8:2, and obtain a mixed solution A after mixing evenly; It should be noted that the proportion of type IV low eutectic solvent is 80%, while the proportion of deionized water is 20%.

[0054] S2: weighing a molybdenum source and a sulfur source in a molar ratio of 1:8 and dissolving them in the mixed solution A obtained in step S1, and mixing them evenly to obtain a clear and transparent mixed solution B; S3: adding an amphoteric surfactant, cocamidopropyl betaine (CAPB), in a concentration range of 0 to 0.1 g / ml to the mixed solution B prepared in step S2, and stirring to obtain a mixed solution C; S4: transferring the mixed solution C to a polytetrafluoroethylene reactor and reacting at 200° C. for 18 hours; S5: After the reaction is completed, the reaction solution is naturally cooled to room temperature, the reaction container is opened, and deionized water and ethanol are used for centrifugation and washing; S6: The washed product is naturally dried to obtain a black powder.

[0055] It can be observed from Example 4 that Figure 7 The XRD pattern of molybdenum disulfide prepared in solution 5 is significantly different from that of the control example, embodiment 1, embodiment 2 and embodiment 3. The crystal form is further transformed into the metastable phase molybdenum disulfide, and the crystallinity is higher than that of the control example, embodiment 1, embodiment 2 and embodiment 3. Figure 4 , Figure 5 and Figure 6 There was a further decline.

[0056] Example 5: A method for synthesizing metastable phase molybdenum disulfide based on a type V deep eutectic solvent and a water system, comprising the following steps: S1: Choline chloride and cobalt chloride hexahydrate are selected as hydrogen bond donors and hydrogen bond acceptors, respectively, and then thymol and menthol are mixed in a molar ratio of 1:8, and after mixing evenly, a type V deep eutectic solvent is obtained. After the mixing is completed, the type V deep eutectic solvent is added to obtain a mixed solution A; It should be noted that the proportion of type V low eutectic solvent is 100%, while the proportion of deionized water is 0%.

[0057] S2: weighing a molybdenum source and a sulfur source in a molar ratio of 1:10 and dissolving them in the mixed solution A obtained in step S1, and mixing them evenly to obtain a clear and transparent mixed solution B; S3: adding a nonionic surfactant, polyvinyl alcohol, in a concentration range of 0 to 0.1 g / ml to the mixed solution B prepared in step S2, and stirring to obtain a mixed solution C; S4: reacting the mixed solution C in an oil bath at 150° C. for 10 hours, wherein the stirring speed is 200 rpm; S5: After the reaction is completed, the reaction solution is naturally cooled to room temperature, the reaction container is opened, and deionized water and ethanol are used for centrifugation and washing; S6: The washed product is naturally dried to obtain a black powder.

[0058] It can be observed from Example 5 that Figure 8 This is an electron scanning image of the prepared molybdenum disulfide, showing a layered stacking structure. Fig. 9 The XRD pattern of molybdenum disulfide shows a metastable phase. Fig.10 The Raman diagram of the embodiment 1, embodiment 2, embodiment 3 and embodiment 4 shows obvious difference in that the crystal form is further transformed into the metastable phase of molybdenum disulfide, and the crystallinity is higher than that of the embodiment 1. Figure 4 , Figure 5 , Figure 6 and Figure 7 The lowest, and the crystal plane is wider, which is a typical metastable phase MoS2 structure.

[0059] The present invention is not limited to the above-mentioned embodiments. Anyone should be aware that any structural changes made under the enlightenment of the present invention, and any technical solutions that are the same or similar to the present invention, fall within the protection scope of the present invention. The technology, shape, and structural parts not described in detail in the present invention are all well-known technologies.

Claims

1. A method for synthesizing metastable phase molybdenum disulfide based on a deep eutectic solvent and water system, characterized in that: The following steps are involved: S1: selecting at least one hydrogen bond donor (HBD) and at least one hydrogen bond acceptor (HBA), adjusting the ratio of HBD to HBA to form a deep eutectic solvent (DES), and then mixing the DES with deionized water in a predetermined ratio to obtain a DES / water mixed solution, wherein the ratio of the DES / water mixed solution ranges from 0% to 100% of water; S2: dissolving a molybdenum source and a sulfur source in the DES / water mixture prepared in step S1 to obtain a solution; S3: adding a surfactant to the solution in step S2 and stirring it thoroughly to dissolve it; S4: treating the solution through a reaction mechanism to react the molybdenum source and the sulfur source under required temperature and time conditions; S5: After the reaction is completed, the mixture is naturally cooled to room temperature, the product is separated by centrifugation, and washed with deionized water and anhydrous ethanol. Finally, lamellar metastable phase molybdenum disulfide is obtained by drying.

2. A method for synthesizing metastable phase molybdenum disulfide based on DES and water system according to claim 1, characterized in that: The combination types of HBD and HBA in step S1 include but are not limited to: The chemical composition of DES is usually represented by the general formula Cat + X - zY indicates that Cat + represents a cation belonging to the ammonium, phosphonium or sulfonium group, X represents a Lewis base, Y represents a Lewis acid, and z represents the stoichiometric ratio between the two.

3. Type I DES (Cat + X - MCl X : Metal salts and organic salts, M can be Zn, Sn, Fe, etc.): for example, choline chloride + zinc chloride; Type II DES (Cat + X - MCl X yH2O: metal salt hydrates and organic salts, M can be CONH2, COOH, OH, etc.): for example, choline chloride + cobalt chloride hexahydrate; Type III DES (Cat + X - RZ: HDB and organic salt, Z can be CONH2, COOH, OH, etc.): for example, choline chloride + urea; Type IV DES (MCl X +RZ: metal salt hydrate and HBD, M can be Zn, Al, etc., Z can be CONH2, OH, etc.): for example, zinc chloride + urea; Type V (non-ionic: HBA molecules and HBD molecules): for example, thymol + menthol.

4. The method for synthesizing metastable phase molybdenum disulfide based on DES and water system according to claim 1, characterized in that: The molybdenum source in step S2 includes but is not limited to: sodium molybdate, ammonium molybdate, ammonium thiomolybdate, molybdenum dioxide, molybdenum trioxide, molybdenum phthalocyanine, molybdenum citrate, and molybdenum-carbon complex.

5. The method for synthesizing metastable phase molybdenum disulfide based on DES and water system according to claim 1, characterized in that: The sulfur source in step S2 includes but is not limited to: sodium sulfide, sodium sulfite, thiourea, L-cysteine, sulfur powder, and hydrogen sulfide gas.

6. The method for synthesizing metastable phase molybdenum disulfide based on DES and water system according to claim 1, characterized in that: In step S3, the surfactant concentration range is 0 to 0.1 g / ml, and the surfactant includes but is not limited to: cationic surfactants, anionic surfactants, nonionic surfactants and amphoteric surfactants, for example: one or a combination of two or more of polyvinyl pyrrolidone, polyvinyl alcohol, Tween-80, Span-60, cetyltrimethylammonium chloride, sodium lauryl sulfate, cocamidopropyl betaine, etc.

7. The method for synthesizing metastable phase molybdenum disulfide based on DES and water system according to claim 1, characterized in that: The reaction mechanism in step S4 includes but is not limited to: hydrothermal reaction, oil bath reaction or microwave reaction. When using hydrothermal reaction, first, the solution obtained in step S3 is transferred to a closed polytetrafluoroethylene reactor and reacted at 180° C. to 280° C. for 1 to 30 hours with a stirring speed of 0 to 200 rpm.

8. The method for synthesizing metastable phase molybdenum disulfide based on DES and water system according to claim 7, characterized in that: When using an oil bath reaction, first, transfer the solution obtained in step S3 to a closed reactor equipped with a condensation reflux device, heat in an oil bath to maintain a constant temperature, react at 80°C to 150°C for 1 to 30 hours, and stir at a speed of 0 to 200 rpm.

9. The method for synthesizing metastable phase molybdenum disulfide based on DES and water system according to claim 7, characterized in that: When using microwave reaction, first, the solution obtained in step S3 is transferred to a sealed microwave reaction container and heated at a power of 300 to 1200 W for 1 to 20 minutes. During the reaction, the morphology and crystal form of molybdenum disulfide can be optimized by adjusting the microwave power and time.

10. The method for synthesizing metastable phase molybdenum disulfide based on DES and water system according to claim 1, characterized in that: In step S5, the particle size of the molybdenum disulfide flake layer ranges from 200 nm to 10 μm, and the thickness ranges from 1 nm to 50 nm.

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