Method for preparing transition metal chalcogenide crystal or nanosheet
By forming transition metal chalcogenide crystals through high-temperature reaction and rapid cooling, the problems of insufficient safety and long production cycle in existing technologies have been solved, enabling efficient and large-scale preparation of high-purity nanosheets, which are suitable for fields such as batteries, catalysis, supercapacitors and precious metal recycling.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- TSINGHUA SHENZHEN INTERNATIONAL GRADUATE SCHOOL
- Filing Date
- 2026-03-11
- Publication Date
- 2026-05-15
AI Technical Summary
Existing technologies for preparing transition metal chalcogenide nanosheets suffer from safety issues, long production cycles, and difficulties in scaling up production. In particular, traditional methods such as chemical intercalation exfoliation use n-butyllithium, which is self-igniting, limiting the purity of the exfoliated products and resulting in long production cycles.
A high-temperature reaction is used to mix a transition metal source precursor with a chalcogenide, and then rapidly cooling is used to form a transition metal chalcogenide crystal with metal intercalation. The intercalation structure is constructed in a mild ion exchange process, and crystal growth and intercalation are carried out simultaneously, avoiding the use of hazardous reagents and shortening the production cycle.
This method enables the safe and efficient preparation of high-purity transition metal chalcogenide nanosheets, shortening the production cycle and making it suitable for large-scale production with yields ranging from grams to kilograms, suitable for continuous industrial production.
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Figure CN122035951A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of two-dimensional transition metal chalcogenide materials technology, and particularly relates to a method for preparing transition metal chalcogenide crystals or nanosheets. Background Technology
[0002] Transition metal chalcogenides (TMDs) are important two-dimensional materials with excellent physicochemical properties, possessing enormous application potential in electronic devices, energy catalysis, and optoelectronic devices. However, to truly translate their superior properties into engineering and industrial applications, rapid and scalable fabrication of TMD nanosheets is essential. Currently, chemical vapor deposition (CVD) technology can obtain high-quality monolayer or few-layer nanosheets, but its production is limited by growth area and equipment complexity, preventing gram-level yields. Obtaining two-dimensional TMD nanosheets from bulk TMD crystals through exfoliation is considered a scalable technological route.
[0003] However, traditional liquid phase exfoliation and ball milling methods suffer from problems such as low efficiency or long cycle time. In contrast, chemical intercalation exfoliation technology can effectively weaken the interlayer interaction of TMD crystals, thereby achieving efficient exfoliation of nanosheets. However, the thermodynamically stable phase of most TMD materials is the 2H phase, such as MoS2, whose electronic structure is unfavorable to foreign intercalation electrons, and usually requires highly reducing reagents such as butyllithium to achieve intercalation. Chemical intercalation exfoliation technology based on the n-butyllithium / hexane system has been widely adopted, but it still faces three key challenges in the large-scale preparation of TMD nanosheets: (1) n-butyllithium has extremely high self-ignition, which makes it difficult to meet the safety requirements of large-scale production; (2) the exfoliation product is usually a mixture of metallic 1T (T′) phase and semiconductor 2H phase, and the phase purity is limited; (3) the production cycle is long, and the preparation of nanosheets in the tens of milligrams often requires a reaction time of 48-72 hours. In recent years, although electrochemical intercalation and stripping technology has improved safety, it usually relies on pre-coating TMD crystal materials onto the electrode surface before electrochemical intercalation. The intercalation process is limited by the electrode area, which seriously restricts its feasibility in large-scale preparation.
[0004] Therefore, existing transition metal chalcogenide nanosheet preparation technologies typically follow the path of "first synthesizing chalcogenide crystals - then performing post-processing intercalation - finally exfoliating to obtain nanosheets," which faces core challenges such as insufficient safety, long production cycles, and difficulties in scaling up. A new, safe, efficient, and scalable preparation technology needs to be developed. Summary of the Invention
[0005] This invention aims to address the problems of insufficient safety, long production cycles, and difficulties in scaling up existing transition metal chalcogenide nanosheet preparation technologies, and provides a safe, efficient, and scalable method for preparing transition metal chalcogenide crystals or nanosheets. To achieve this goal, this invention breaks through the traditional nanosheet preparation paradigm. Previous methods typically follow a path of "first synthesizing chalcogenide crystals—then performing post-processing intercalation—finally exfoliating to obtain nanosheets," while this invention moves the preparation approach forward, starting from the crystal formation stage, achieving simultaneous crystal growth and intercalation, and redesigning the nanosheet construction strategy. This invention employs the following technical solution: using chalcogenide hydrides as the chalcogenide source, a transition metal source precursor is mixed with it and subjected to a high-temperature reaction. During the high-temperature reaction, the reactants are in a molten or semi-molten state; simultaneously, the metal is intercalated in situ while the transition metal chalcogenide crystal begins to grow, allowing it to grow synchronously with the transition metal-chalcogenide bond, forming an intercalated structure, constructing an intercalated transition metal chalcogenide crystal from bottom to top; subsequently, a mild ion exchange and exfoliation process is used to obtain high-quality transition metal chalcogenide nanosheets.
[0006] The specific plan is as follows: On one hand, the present invention provides a method for preparing metal-intercalated transition metal chalcogenide crystals, comprising the following steps: Transition metal source precursor and A(HX) n The mixture undergoes a high-temperature reaction, followed by rapid cooling to obtain metal-intercalated transition metal chalcogenide crystals. The transition metal source precursor is a precursor containing transition metal M, selected from at least one of transition metal oxides and transition metal salts; A(HX) n In this context, A represents a metal selected from at least one of alkali metals and alkaline earth metals; X represents a chalcogenide element. The transition metal chalcogenide of the metal intercalation is transition metal chalcogenide A of metal A intercalation. x MX2; The temperature of the high-temperature reaction is ≥400℃.
[0007] In the technical solution of this invention, A(HX) n It provides chalcogens and metallic A atoms for high-temperature reactions and also plays a reducing role.
[0008] In the technical solution of this invention, crystal growth and intercalation are carried out simultaneously during the high-temperature reaction process.
[0009] In a preferred embodiment, the chalcogen elements are selected from at least one of sulfur, tellurium, and selenium.
[0010] Preferably, A is selected from at least one of sodium, lithium, potassium, and calcium.
[0011] Preferably, A(HX) n It is selected from at least one of sodium hydrosulfide (NaHS), lithium hydrosulfide (LiHS), potassium hydrosulfide (KHS), calcium hydrosulfide (Ca(HS)2), sodium selenide, and sodium telluride, preferably at least one of sodium hydrosulfide and lithium hydrosulfide.
[0012] Preferably, the transition metal oxide is selected from at least one of molybdenum trioxide, molybdenum dioxide, tungsten trioxide, titanium dioxide, and tantalum pentoxide; and the transition metal salt is selected from at least one of ammonium molybdate, sodium molybdate, and ammonium tungstate.
[0013] Preferably, the transition metal source precursor contains a transition metal that reacts with A(HX). n The molar ratio of chalcogens contained therein is 1:2 to 20, preferably 1:4 to 8, for example 1:4, 1:6 or 1:8.
[0014] In the technical solution of this invention, the transition metal source precursor and A(HX) are modified. n The molar ratio can tune the phase structure when the transition metal source precursor and A(HX) are mixed. n When the molar ratio of the two is greater than or equal to 1:4, the resulting transition metal chalcogenide crystals and nanosheets exhibit a 1T phase structure with a phase purity of nearly 90% to 100%; when the molar ratio is less than or equal to 1:3, the resulting crystals and nanosheets mainly exhibit a 2H phase structure with a phase purity of about 80% to 100%. Generally, the 1T phase structure is preferably prepared using the present invention.
[0015] In a preferred embodiment, the high-temperature reaction temperature is 400~1500℃, preferably 700~1000℃, for example 700℃, 800℃, 900℃, or 1000℃. Within this temperature range, the transition metal source precursor and A(HX)... n It is in a molten or semi-molten state, which can promote the rapid progress of the reaction.
[0016] Preferably, the high-temperature reaction time is 10 seconds to 60 minutes, more preferably 1 to 10 minutes, for example 1 minute, 5 minutes or 10 minutes.
[0017] Preferably, the high-temperature reaction is carried out in a vacuum or inert atmosphere.
[0018] Preferably, the reaction apparatus for the high-temperature reaction is preheated.
[0019] Preferably, the rapid cooling rate is 30~60℃ / min.
[0020] In some specific embodiments, the preheating and rapid cooling are achieved using a portable tube furnace. Considering the heating and cooling time, 0.1-100 kg can be produced on a large scale within 2 hours, yielding A. x MX2 crystals have a large lateral dimension, ranging from 5 to 100 micrometers.
[0021] In some specific embodiments, the rapid cooling process further includes a washing process; the washing is ethanol washing.
[0022] In another aspect, the present invention provides a transition metal chalcogenide crystal with metal intercalation obtained by the above preparation method.
[0023] In another aspect, the present invention provides a method for preparing transition metal chalcogenide crystals, comprising the following steps: soaking and washing the above-mentioned metal-intercalated transition metal chalcogenide crystals in water to remove the intercalated metal, thereby obtaining the transition metal chalcogenide crystal MX2.
[0024] In another aspect, the present invention provides a method for preparing transition metal chalcogenide nanosheets, comprising the following steps: The metal A is Li: The above-mentioned metal intercalation is performed using a transition metal chalcogenide crystal (A). x MX2) was obtained by washing to remove the intercalated metal and then ultrasonically dispersing it in water to obtain a nanosheet dispersion of MX2; Alternatively, the metal A is not Li: the transition metal chalcogenide crystal (A) intercalated with the above metal is used. x MX2 was immersed in a lithium-ion solution for ion exchange, then residual metal impurities were removed by washing, and finally ultrasonically dispersed in water to obtain a nanosheet dispersion of MX2.
[0025] Preferably, the concentration of the lithium ion solution is 1~8 mol / L.
[0026] Preferably, the lithium-ion solution used is selected from at least one of lithium chloride solution and lithium nitrate solution, and more preferably lithium chloride solution.
[0027] Preferably, the soaking time is 0.5 to 24 hours, and more preferably 1 to 3 hours.
[0028] Preferably, the power of the ultrasound is 100~400 W and the duration is 10~60 minutes.
[0029] In the technical solution of this invention, the lateral dimensions of the transition metal chalcogenide nanosheets are 2-50 micrometers. After exfoliation, the nanosheets no longer contain alkali metals or alkaline earth metals and have extremely high exfoliation yield and monolayer ratio, with an exfoliation yield of 50%-95% and a monolayer ratio of 40%-80%. The nanosheets have a 1T phase structure, high crystallinity, and low defect density.
[0030] The crystals and nanosheets prepared by the method of this invention have lateral dimensions of micrometers to tens of micrometers, complete lattices and low defect density, and have broad application prospects in fields such as batteries, catalysis, supercapacitors, electromagnetic shielding and precious metal recycling.
[0031] Compared with the prior art, the present invention has the following advantages and effects: 1) It does not require the use of dangerous organic lithium reagents such as n-butyllithium, making it highly safe.
[0032] 2) The reaction time is short, crystal growth and intercalation are completed simultaneously, which significantly shortens the preparation cycle and the entire process can be completed in minutes.
[0033] 3) The crystals and nanosheets have few defects, and the intercalation is completed in the early stage of crystal formation, effectively avoiding the defects introduced by strong intercalation in the later stage.
[0034] 4) It is easy to scale up, and can achieve output from gram level to kilogram level or above, making it suitable for continuous industrial production. Attached Figure Description
[0035] Figure 1 This is a photograph of the 100-gram-scale MoS2 crystal synthesized in Example 1 of this invention.
[0036] Figure 2 The image shows the XRD pattern of the MoS2 crystal prepared in Example 1 of this invention.
[0037] Figure 3 An optical photograph of the MoS2 nanosheets prepared in Example 2 of this invention. Detailed Implementation
[0038] The following embodiments are merely some, not all, of the embodiments of the present invention. Therefore, the detailed descriptions of the embodiments provided below are not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.
[0039] In this invention, unless otherwise specified, all equipment and raw materials are commercially available or commonly used in the industry. The methods described in the following embodiments are conventional methods in the art, unless otherwise specified.
[0040] Example 1 MoO3 powder and sodium hydrosulfide powder were thoroughly mixed at a 1:6 molar ratio at room temperature. The mixture was then placed in a tube furnace and preheated to 1000°C at a rate of 30°C / min under an argon atmosphere with a flow rate of 100 sccm. The mixture was then pushed into the heating zone (1000°C) and held for 1 minute. The end containing the sample was then moved to the cooling end of the furnace to obtain Na. x MoS2 crystal powder (cooling rate approximately 50 °C / min). The obtained Na x MoS2 crystal powder was washed repeatedly with ethanol to remove impurities, and then purified Na was added. x MoS2 crystal powder was soaked in water for 24 hours, followed by multiple water washes to achieve sodium deintercalation, ultimately yielding deintercalated MoS2 crystals. Figure 1 Photographs of 100-gram-scale MoS2 crystals synthesized using this method are shown. Figure 2 The image shows the X-ray diffraction (XRD) pattern of the MoS2 crystal. The diffraction peak at 14.6° corresponds to the (002) crystal plane of the molybdenum disulfide crystal, proving that it is a molybdenum disulfide crystal.
[0041] Na prepared in this embodiment x The lateral dimensions of MoS2 crystals are 10-40 micrometers.
[0042] The molybdenum disulfide crystals prepared in this embodiment have a lateral dimension of approximately 10-40 micrometers. Deintercalation does not significantly change the crystal size, and the phase structure is a 1T phase.
[0043] Example 2 Na obtained in Example 1 x MoS2 crystal powder was immersed in a 6 mol / L lithium chloride aqueous solution and allowed to stand for 1 hour to achieve the exchange reaction of lithium and sodium ions. The product was then washed three times with deionized water to remove residual lithium and sodium salts. Next, the sample was ultrasonically treated in water for 15 minutes (120W) to obtain a molybdenum disulfide nanosheet dispersion. The obtained nanosheets were dispersed and transferred onto a Si / SiO2 substrate, and their morphology was observed under an optical microscope (e.g., ...). Figure 3 (As shown). The nanosheets have a lateral dimension of approximately 10 μm and exhibit distinct monolayer / few-layer nanosheet contrast characteristics.
[0044] The molybdenum disulfide nanosheets prepared in this embodiment have a 1T phase structure.
[0045] The present invention also uses the method in Examples 1-2 to prepare molybdenum disulfide crystals and nanosheets with different molar ratios of MoO3 powder and sodium hydrosulfide powder. Experimental characterization revealed that when the molar ratio of MoO3 powder to sodium hydrosulfide powder is ≥1:4, the obtained transition metal chalcogenide crystals and nanosheets all exhibit a 1T phase structure with a phase purity of nearly 90%~100%; when the molar ratio is ≤1:3, the obtained crystals and nanosheets mainly exhibit a 2H phase structure with a phase purity of about 80%~100%.
[0046] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for preparing metal-intercalated transition metal chalcogenide crystals, characterized in that, Includes the following steps: Transition metal source precursor and A(HX) n The mixture undergoes a high-temperature reaction, followed by rapid cooling to obtain metal-intercalated transition metal chalcogenide crystals. The transition metal source precursor is a precursor containing transition metal M, selected from at least one of transition metal oxides and transition metal salts; A(HX) n In this context, A represents a metal selected from at least one of alkali metals and alkaline earth metals; X represents a chalcogenide element. The transition metal chalcogenide of the metal intercalation is transition metal chalcogenide A of metal A intercalation. x MX2; The temperature of the high-temperature reaction is ≥400℃.
2. The method according to claim 1, characterized in that, The chalcogen elements are selected from at least one of sulfur, tellurium, and selenium; Preferably, A is selected from at least one of sodium, lithium, potassium, and calcium; Preferably, A(HX) n It is selected from at least one of sodium hydrosulfide, lithium hydrosulfide, potassium hydrosulfide, calcium hydrosulfide, sodium selenide, and sodium telluride, preferably at least one of sodium hydrosulfide and lithium hydrosulfide; Preferably, the transition metal oxide is selected from at least one of molybdenum trioxide, molybdenum dioxide, tungsten trioxide, titanium dioxide, and tantalum pentoxide; and the transition metal salt is selected from at least one of ammonium molybdate, sodium molybdate, and ammonium tungstate.
3. The method according to claim 1, characterized in that, The transition metal source precursor contains transition metals and A(HX). n The molar ratio of chalcogens contained in it is 1:2 to 20, preferably 1:4 to 8.
4. The method according to claim 1, characterized in that, The high-temperature reaction temperature is 400~1500℃, preferably 700~1000℃; Preferably, the high-temperature reaction time is 10 seconds to 60 minutes, more preferably 1 to 10 minutes; Preferably, the high-temperature reaction is carried out in a vacuum or inert atmosphere; Preferably, the reaction apparatus for the high-temperature reaction is preheated; Preferably, the rapid cooling rate is 30~60℃ / min.
5. The method according to claim 1, characterized in that, The rapid cooling process also includes a washing process; the washing is ethanol washing.
6. The metal-intercalated transition metal chalcogenide crystal obtained by any of the preparation methods described in claims 1-5.
7. A method for preparing transition metal chalcogenide crystals, characterized in that, The process includes the following steps: soaking and washing the metal-intercalated transition metal chalcogenide crystal of claim 6 in water to remove the intercalated metal, thereby obtaining the transition metal chalcogenide crystal MX2.
8. A method for preparing transition metal chalcogenide nanosheets, characterized in that, The method includes the following steps: The metal A is Li: The metal-intercalated transition metal chalcogenide crystal of claim 6 is washed to remove the intercalated metal, and then ultrasonically dispersed in water to obtain an MX2 nanosheet dispersion. Alternatively, the metal A is not Li: the transition metal chalcogenide crystal of the metal intercalation described in claim 6 is immersed in a lithium ion solution for ion exchange, then residual metal impurities are removed by washing, and finally ultrasonically dispersed in water to obtain an MX2 nanosheet dispersion.
9. The method according to claim 8, characterized in that, The concentration of the lithium-ion solution is 1~8 mol / L; Preferably, the lithium-ion solution used is selected from at least one of lithium chloride solution and lithium nitrate solution, and is preferably a lithium chloride solution.
10. The method according to claim 8, characterized in that, The soaking time is 0.5 to 24 hours, preferably 1 to 3 hours; Preferably, the power of the ultrasound is 100~400 W and the duration is 10~60 minutes.