Transition metal sulfide quantum sheets and methods of making, catalytic uses, batteries thereof

Abstract

The application discloses a transition metal sulfide quantum sheet and a preparation method, catalytic use and battery thereof, wherein the preparation method comprises the following steps: synthesizing a multi-metal MAX phase precursor, the M position in the MAX phase precursor containing more than four transition metal elements; performing topological conversion reaction on the MAX phase precursor and a gas containing sulfur elements to generate a transition metal sulfide with an accordion-like shape; and performing peeling treatment on the transition metal sulfide to obtain the transition metal sulfide quantum sheet; and the lateral size of the transition metal sulfide quantum sheet is less than 10 nm. The quantum sheet has excellent catalytic performance, such as high electrocatalytic activity on lithium polysulfide.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of nanomaterial preparation, and particularly relates to a transition metal sulfide quantum sheet, a preparation method thereof, and a catalytic use and a battery. BACKGROUND

[0002] Two-dimensional (2D) atomic layers, represented by graphene, boron nitride, transition metal dichalcogenides (TMDs), and transition metal carbides and nitrides (MXenes), have attracted extensive attention due to their remarkable physical and chemical properties compared with layered materials. Among them, two-dimensional TMDs with a general formula of MX2 are formed by a layer of hexagonally close-packed transition metal (M = V, Nb, Ta, Mo or W) sandwiched between two layers of chalcogen (X = S, Se or Te), forming a typical X-M-X configuration. In two-dimensional TMDs, the coordination mode of transition metal and surrounding chalcogen can be divided into octahedron and prism, and according to the stacking sequence of MX2 monolayer, 1T, 2H and 3R phases can be formed. The diverse composition and polymorphic structure make two-dimensional TMDs exhibit high carrier mobility, variable electronic structure and strong spin-orbit coupling effect, and have broad application prospects in the fields of electronics, catalysis and energy storage.

[0003] Both theoretical calculations and experimental results show that the electrical and electrochemical properties of two-dimensional TMDs are strongly dependent on their lateral size, exposed edges and structural phase. In this regard, two-dimensional TMD quantum sheets (QSs) with a lateral size less than 10 nanometers have emerged, which combine the unique properties of two-dimensional nanosheets and quantum dots, and become an important class of nanomaterials. Quantum sheets are usually prepared by exfoliation (such as ultrasonic treatment or ball milling) or hydrothermal / solvothermal synthesis method, followed by separation treatment. Due to the significant reduction in lateral size, the charge carriers in quantum sheets are confined in all spatial dimensions, and compared with two-dimensional nanosheets, have higher charge carrier concentration and mobility, endowing quantum sheets with high electronic states and strong electric field effect. In addition, two-dimensional TMD quantum sheets have extremely high edge exposure, greatly increasing the number of electrochemically active sites, significantly improving the reaction current density, accelerating the mass transfer process and promoting the reaction kinetics. However, the current quantum sheets usually have semiconductor behavior related to 2H phase, and due to the small lateral size, the basal plane is prone to slip, and it is still a challenge to prepare 1T phase quantum sheets, which limits their application in some fields with specific requirements for phase structure. SUMMARY

[0004] The present application aims to provide a method for preparing transition metal sulfide quantum sheets by a multi-metal strategy, solving the problems of difficult quantum sheet preparation and poor phase stability in the prior art.

[0005] The first aspect of the present application provides a preparation method of a transition metal sulfide quantum sheet, comprising the following steps:

[0006] (a) synthesizing a multi-metal MAX phase precursor, the M site in the MAX phase precursor containing four or more transition metal elements; topologically transforming the MAX phase precursor with a gas containing sulfur element to generate a transition metal sulfide with an accordion-like structure; or, topologically transforming a MXene material with a gas containing sulfur element to generate a transition metal sulfide; the M site in the MXene material containing four or more transition metal elements;

[0007] (b) performing exfoliation treatment on the above transition metal sulfide to obtain a transition metal sulfide quantum sheet; the lateral size of the transition metal sulfide quantum sheet being less than 10 nm.

[0008] In some embodiments, the transition metal elements in the M site of the above MAX phase precursor or the MXene material are selected from Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W, Sc, Y elements.

[0009] In some embodiments, the average atomic radius difference in the M site of the above MAX phase precursor is greater than 8%, preferably greater than 11%.

[0010] In some embodiments, the M site of the above MAX phase precursor contains five or more transition metal elements.

[0011] In some embodiments, the above transition metal sulfide quantum sheet is a single-layer structure.

[0012] In some embodiments, the lateral size of the above transition metal sulfide quantum sheet is 2-10 nm.

[0013] In some embodiments, the thickness of the above transition metal sulfide quantum sheet is 0.5-1.5 nm.

[0014] In some embodiments, the above gas containing sulfur element refers to gaseous sulfur and / or hydrogen sulfide.

[0015] In some embodiments, the above high-entropy transition metal sulfide quantum sheet is a 1T phase or contains a 1T phase.

[0016] In some embodiments, the above MAX phase precursor is a multi-metal in-plane ordered structure.

[0017] In some embodiments, the above MAX phase precursor is an in-plane ordered high-entropy MAX phase material.

[0018] In some embodiments, the reaction temperature of the above topological transformation reaction is between 600 and 1100°C, and the reaction time is 10 min to 10 h.

[0019] In some embodiments, the above-mentioned exfoliation treatment employs a method of ultrasonic liquid exfoliation.

[0020] The second aspect of the present application provides a transition metal sulfide quantum sheet, which is composed of transition metal elements M and chalcogen elements X, the M contains at least four transition metal elements, and the X is sulfur element; the lateral size of the transition metal sulfide quantum sheet is less than 10 nm; the transition metal sulfide quantum sheet is in 1T phase, or contains 1T phase.

[0021] In some embodiments, the above-mentioned transition metal elements M are selected from Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W, Sc, Y elements.

[0022] In some embodiments, the average atomic radius difference value of the above-mentioned transition metal element M site is greater than 8%, preferably, greater than 11%;

[0023] In some embodiments, the above-mentioned transition metal element M site contains more than five transition metal elements.

[0024] In some embodiments, the above-mentioned transition metal sulfide quantum sheet is a single-layer structure.

[0025] In some embodiments, the lateral size of the above-mentioned transition metal sulfide quantum sheet is 2-10 nm.

[0026] In some embodiments, the thickness of the above-mentioned transition metal sulfide quantum sheet is 0.5-1.5 nm.

[0027] The third aspect of the present application provides a use of the above-mentioned transition metal sulfide quantum sheet in the field of catalysis and batteries.

[0028] The fourth aspect of the present application provides a catalytic device containing the above-mentioned transition metal sulfide quantum sheet.

[0029] The fifth aspect of the present application provides a battery containing the above-mentioned transition metal sulfide quantum sheet.

[0030] The present application provides an efficient multi-metal strategy to prepare phase quantum sheets of transition metal sulfides by controllably introducing a plurality of metal atoms with large size differences to slow down basal plane sliding. The key is to transform the multi-metal carbide layer (MAX) topology into a multi-metal transition metal sulfide with high strain, which is easy to break the material into quantum sheets during exfoliation. Due to the stability and highly exposed edges of the quantum sheets, the quantum sheets of the present application exhibit excellent catalytic performance, such as high electrocatalytic activity for lithium polysulfide, and achieve good rate performance and long cycle stability of 744 mAh g -1 at 5C rate in lithium-sulfur batteries. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 Schematic diagram of atomic structure change in the preparation process of transition metal sulfide quantum sheet of the present application.

[0032] Figure 2 X-ray diffraction (XRD) pattern of i-MAX phase containing selected transition metal atoms of W, Mo, V, Sc and Y of the present application, showing sharp and prominent diffraction peaks attributed to i-MAX phase, and the shift of (002) peak with atomic size change. Among them, the XRD pattern of multi-metal i-MAX phase shows sharp and strong characteristic (002), (004) and (110) diffraction peaks attributed to i-MAX phase. For W 4 / 3 (Sc 1 / 2 Y 1 / 2 ) 2 / 3 AlC, the (002) peak is at 12.97°, slightly higher than that of (W 2 / 3 Y 1 / 3 )2AlC (12.93°), which is due to the introduction of Sc with smaller atomic radius than Y , resulting in a decrease in interlayer spacing. Since the atomic radius of Mo is smaller than that of W , the (002) peak of (W 1 / 2 Mo 1 / 2 ) 4 / 3 (Sc 1 / 2 Y 1 / 2 )2 / 3AlC moves to 12.99°. For (W 2 / 5 Mo 2 / 5 V 1 / 5 ) 4 / 3 (Sc 3 / 5 Y 2 / 5 )2 / 3AlC, its (002) peak further moves to 13.08°, which is caused by the introduction of V atoms with the smallest atomic radius .

[0033] Figure 3 X-ray diffraction (XRD) pattern of i-MAX phase a) (W 2 / 5 Mo 2 / 5 V 1 / 5 ) 4 / 3 (Sc 3 / 5 Y 2 / 5 ) 2 / 3 AlC, b) (W 1 / 2 Mo 1 / 2 ) 4 / 3 (Sc 1 / 2Y 1 / 2 )2 / 3AlC, c) W 4 / 3 (Sc 1 / 2 Y1 / 2 ) 2 / 3 AlC and d) (W 2 / 3 Y 1 / 3 SEM image of AlC showing typical layered structure.

[0034] Figure 4 Morphology and structure analysis of high-entropy i-MAX phase (W 2 / 5 Mo 2 / 5 V 1 / 5 ) 4 / 3 (Sc 3 / 5 Y 2 / 5 ) 2 / 3 STEM image (a) and corresponding elemental mapping images of AlC showing coexistence and uniform distribution of W (b), Mo (c), V (d), Sc (e) and Y (f) species. The same phenomenon of multi-element coexistence and uniform distribution was observed for each element in other i-MAX phases according to the test results (figures omitted).

[0035] Figure 5 Morphology and structure analysis of high-entropy i-MAX phase (W 2 / 5 Mo 2 / 5 V 1 / 5 ) 4 / 3 (Sc 3 / 5 Y 2 / 5 ) 2 / 3 Photograph of AlC (a) and its derived accordion-like 1T phase sulfide (HE-(WMoVScY)S2) (b), where the volume of the resulting sulfide is about 4 times that of the i-MAX phase.

[0036] Figure 6 Morphology and structure analysis of high-entropy i-MAX phase (W 2 / 5 Mo 2 / 5 V 1 / 5 ) 4 / 3 (Sc 3 / 5 Y 2 / 5 ) 2 / 3 XRD pattern of 1T phase accordion-like HE-(WMoVScY)S2 generated by topological transformation of AlC under the action of sulfur vapor, showing the disappearance of i-MAX phase peaks and the presence of sulfide characteristic diffraction peaks.

[0037] Figure 7 Schematic diagram of a) the comparative sample of multi-metal sulfide prepared by powder sintering method and b) the XRD pattern of the resulting product, showing that the product is a mixture of sulfides (WS2, MoV2S4, YS and Y2S3), indicating that severe phase separation occurred during the reaction process.

[0038] Figure 8 Morphology and structure analysis of high-entropy 1T phase transition metal sulfide. a) high-entropy i-MAX phase (W2 / 5Mo 2 / 5 V 1 / 5 ) 4 / 3 (Sc 3 / 5 Y 2 / 5 ) 2 / 3 Scanning electron microscopy (SEM) images of the accordion-like 1T phase transition metal sulfide prepared by topotactic transformation of AlC topology, showing highly expanded structure. b) Scanning transmission electron microscopy (STEM) images of the sulfide layer and the corresponding elemental mapping, revealing the presence of Mo, W, V, Sc and Y elements and their uniform dispersion. c) High-resolution transmission electron microscopy (HRTEM) images of the HE-(WMoVScY)S2 layer and the corresponding fast Fourier transform (FFT) pattern (inset), showing clear lattice fringes with crystallographic features. d, e) Strain distribution maps along the e xx (d) and e xy (e) directions, indicating the presence of tensile strain (white-yellow areas) and compressive strain (dark blue areas) in the basal plane. f, g) Atomically resolved STEM images (f) and line intensity profile of line 1 (g), indicating that the transition metals are located at the center of the 1T phase octahedral units. h) Atomic model of the 1T phase high-entropy sulfide, in top view and side view, respectively. i) Atomic fractions of the transition metal atoms W, Mo, V, Sc and Y in the high-entropy sulfide.

[0039] Figure 9 are TEM and HRTEM images of the two-dimensional HE-(WMoVScY)S2 of the present application, showing ultrathin and single-crystalline features (inset).

[0040] Figure 10 are Raman spectra of the HE-(WMoVScY)S2 of the present application, revealing the presence of J1, J2 and J3 vibration modes of the 1T phase.

[0041] Figure 11 are XRD patterns of other accordion-like 1T phase transition metal sulfides prepared by topotactic transformation of different i-MAX phases of the present application, showing no characteristic peaks of the i-MAX phase, demonstrating the complete conversion of the i-MAX phase under sulfur vapor.

[0042] Figure 12 are SEM images of the accordion-like transition metal sulfides prepared in the present application, a) (WMoScY)S2, b) (WScY)S2, c) (WY)S2, showing highly expanded structural features.

[0043] Figure 13Chemical states of the transition metal and sulfur species of the high-entropy 1T-phase sulfide of the present invention. a-c) W L3-edge (a), Mo K-edge (b), V K-edge (c) XANES spectra of the high-entropy 1T-phase sulfide and corresponding WT analysis (inset), showing similar shape and absorption edge to references and sulfidized state of W, Mo, and V. d, e) Sc K-edge (d) and Y K-edge (e) XANES spectra of the high-entropy 1T-phase sulfide, revealing absorption edge close to sulfide. f) EPR spectrum, showing characteristic signal of S vacancies at g = 2.003.

[0044] Figure 14 Morphology and structure characterization of the transition metal sulfide high-entropy 1T-phase quantum plate of the present invention. a) TEM image and statistical analysis of the lateral size of the obtained quantum plate (inset), showing an average lateral size of 4.5 nanometers. b) Atomically resolved STEM image and corresponding FFT pattern (inset), showing a crystal structure with hexagonally packed transition metal atoms. c) Atomic force microscopy image and statistical analysis of the quantum plate thickness (inset), showing an average thickness of 0.7 nanometers. d) Raman spectrum of the HE-(WMoVScY)S2 quantum plate, revealing the presence of 1T-phase Ji, J2, and J3 vibration modes. e) PL spectrum of the high-entropy 1T-phase quantum plate, showing a clear peak at 320 to 380 nm by using a laser with a wavelength of 230-290 nm and emitting violet light (inset). f) Tacu plot and UV-Vis spectrum (inset) of the high-entropy 1T-phase quantum plate, demonstrating a band gap of 3.94 eV.

[0045] Figure 15 Electrochemical properties of the transition metal sulfide high-entropy 1T-phase quantum plate of the present invention. a, b) CV curves of the Li2S6 symmetric cell (a) and Li2S8 catholyte Li2S precipitation in Li-LiPSs cell (b), showing high electrocatalytic activity of LiPSs and high precipitation capacity of Li2S on the 1T-phase HE-(WMoVScY)S2 quantum plate. c, d) Voltage profiles at different rates of 0.2 to 5 C (c) and rate capability (d), demonstrating typical voltage plateau of the sulfur redox reaction and high rate capability of the high-entropy 1T-phase sulfide quantum plate.

[0046] Figure 16 Cycle performance of the Li-S battery with 1T-phase HE-(WMoVScY)S2 quantum plate of the present invention at 0.2 C, showing a high reversible capacity of 897 mAh g -1 after 200 cycles, with a coulombic efficiency close to 100%.

[0047] Figure 17EIS picture of Li-S battery with 1T phase HE-(WMoVScY)S2 quantum plate, 1T phase (WScY)S2 nanosheet and 2H phase WS2 nanosheet of the application, wherein the HE-(WMoVScY)S2 quantum plate has a small semicircle, indicating that the charge transfer resistance is the lowest (14.4 Ω), and the charge transfer resistances of the 1T phase (WScY)S2 nanosheet and the 2H phase WS2 nanosheet are 32.1 Ω and 49.8 Ω, respectively. DETAILED DESCRIPTION

[0048] The technical solutions of the application are described below through specific examples. It should be understood that one or more steps mentioned in the application do not exclude the existence of other methods and steps before and after the combination steps, or other methods and steps can be inserted between these explicitly mentioned steps. It should also be understood that these examples are only used to illustrate the application and not to limit the scope of the application. Unless otherwise specified, the numbering of each method step is only for the purpose of identifying each method step, and is not intended to limit the arrangement order of each method or to limit the scope of the implementation of the application. Changes or adjustments of the relative relationship can also be considered as the scope of the implementation of the application without substantial technical content changes.

[0049] The raw materials and instruments used in the examples are not specifically limited in source, and can be purchased on the market or prepared according to the conventional methods well known to those skilled in the art.

[0050] Example 1

[0051] This example provides a transition metal sulfide quantum plate and a preparation method thereof, and a preparation process schematic diagram is as shown in Figure 1 The transition metal sulfide quantum plate composition elements include four or five of the transition metal elements W, Mo, V, Sc and Y elements, and the steps include:

[0052] 1) Synthesis of multi-metal i-MAX phase precursor

[0053] The multi-metal i-MAX phase precursor is synthesized by solid phase reaction at high temperature, and the specific synthesis method is as follows:

[0054] i-MAX phase W 4 / 3 (Sc 1 / 2 Y 1 / 2 ) 2 / 3 Synthesis of AlC: tungsten (W), scandium (Sc), yttrium (Y), aluminum (Al) and graphite powder are ball milled according to a molar ratio of 4 / 3:1 / 3:1 / 3:1.3:1, cold-pressed into a shape under a pressure of 10 MPa, and then sintered at 1450℃ for 2 hours in an argon gas stream.

[0055] i-MAX phase (W 2 / 3 Y 1 / 3Synthesis of 2AlC: Tungsten (W), yttrium (Y), aluminum (Al) and graphite powder were ball-milled in a molar ratio of 4 / 3:2 / 3:1.3:1, cold-pressed under 10 MPa pressure, and then sintered at 1450 °C for 2 hours in an argon atmosphere.

[0056] i-MAX phase (W 1 / 2 Mo 1 / 2 )4 / 3(Sc 1 / 2 Y 1 / 2 ) 2 / 3 Synthesis of AlC: Tungsten (W), molybdenum (Mo), scandium (Sc), yttrium (Y), aluminum (Al) and graphite powder were ball-milled in a molar ratio of 2 / 3:2 / 3:1 / 3:1 / 3:1.3:1, cold-pressed under 10 MPa pressure, and then sintered at 1500 °C for 10 hours under argon protection.

[0057] i-MAX phase (V 2 / 3 Sc 1 / 3 Synthesis of 2AlC: Vanadium (V), scandium (Sc), aluminum (Al) and graphite powder were ball-milled in a molar ratio of 4 / 3:2 / 3:1.3:1, cold-pressed under 10 MPa pressure, and then sintered at 1500 °C for 2 hours in an argon atmosphere.

[0058] i-MAX phase (W 2 / 5 Mo 2 / 5 V 1 / 5 ) 4 / 3 (Sc 2 / 5 Y 2 / 5 ) 2 / 3 Synthesis of AlC: by (W 1 / 2 Mo 1 / 2 ) 4 / 2 (Sc 1 / 2Y 1 / 2 ) 2 / 3 AlC and (V 2 / 3 Sc 1 / 3 The 2AlC was synthesized by a solid-state reaction at high temperature. Specifically, (W) was prepared by a 4:1 molar ratio of (W) to (AlC). 1 / 2 Mo 1 / 2 ) 4 / 3 (Sc 1 / 2 Y 1 / 2 ) 2 / 3 AlC and (V 2 / 3 Sc 1 / 3 )2AlC was ground evenly in an agate mortar, cold-pressed under 25 MPa pressure, and then sintered at 1400℃ for 2 hours in an argon atmosphere. The resulting blocky product was ground into powder form (W 2 / 5 Mo 2 / 5 V 1 / 5 ) 4 / 3 (Sc 3 / 5Y2 / 5 ) 2 / 3 AlC.

[0059] 2) Topotactic transformation reaction

[0060] The i-MAX phase precursor is subjected to topotactic transformation reaction with sulfur vapor to generate the accordion-like 1T transition metal chalcogenide, and the specific steps include:

[0061] 0.5 g of the i-MAX phase precursor synthesized in step 1) and 2.0 g of sulfur powder are respectively placed in two crucibles and put into a tube furnace. The sulfur powder is heated to 150°C in the upstream region of the furnace, and the i-MAX phase precursor is heated to 1000°C. The i-MAX phase precursor is kept at 1000°C for 2 hours in an argon gas stream to obtain the accordion-like 1T phase transition metal chalcogenide.

[0062] wherein the i-MAX phase (W 2 / 5 Mo 2 / 5 V 1 / 5 ) 4 / 3 (Sc 3 / 5 Y 2 / 5 ) 2 / 3 AlC as raw material to obtain the product marked as HE-(WMoVScY)S2;

[0063] i-MAX phase (W 1 / 2 Mo 1 / 2 )4 / 3(Sc 1 / 2 Y 1 / 2 ) 2 / 3 AlC as raw material to obtain the product marked as (WMoScY)S2;

[0064] i-MAX phase (W 4 / 3 (Sc 1 / 2 Y 1 / 2 ) 2 / 3 AlC as raw material to obtain the product marked as (WScY)S2;

[0065] i-MAX phase (W 2 / 3 Y 1 / 3 )2AlC as raw material to obtain the product marked as (WY)S2.

[0066] 3) Exfoliation treatment

[0067] This step provides an external force to prepare transition metal sulfide quantum sheets by exfoliation treatment. In this embodiment, a classical liquid phase exfoliation method is used for preparation, and the specific steps are as follows: 1.0 g of accordion-like 1T phase transition metal sulfide powder with accordion-like structure is dispersed in 40 mL of isopropanol solvent, and ultrasonic treatment is carried out at 20°C for 5 hours. The dispersion is subjected to centrifugal separation treatment.

[0068] In other embodiments, the solvent in the liquid exfoliation method can also be selected from one or more of water, N-methylpyrrolidone, N,N-dimethylformamide, ethanol, isopropanol, butanone or toluene, the ultrasonic power is 300W to 1000W, and the ultrasonic time is 0.5h to 6h.

[0069] The results show that the transition metal sulfides containing four or more transition metals: HE-(WMoVScY)S2, (WMoScY)S2 can be exfoliated to obtain quantum sheets, which is related to the high stress existing in the multi-metal transition metal sulfide sheet. While other sulfides containing three or fewer transition metal components are exfoliated to obtain two-dimensional nanosheets (non-quantum sheets) with a lateral size of 500nm to several hundred microns. In terms of exfoliation yield of quantum sheets, by high-resolution transmission electron microscopy observation, HE-(WMoVScY)S2 is completely exfoliated to obtain quantum sheets, with a yield close to 100%, while (WMoScY)S2 can only partially exfoliate to obtain quantum sheets.

[0070] Therefore, the more preferred embodiment of the application is to select a high-entropy i-MAX phase precursor or high-entropy MXene with five or more types of transition metal elements as a raw material, to obtain a high-entropy transition metal chalcogenide through a topological transformation reaction, and then to obtain a quantum sheet through exfoliation treatment. The lateral size of the obtained quantum sheet is in the range of 2.0-7.0 nanometers, the average size is about 4.5 nanometers, the thickness is about 0.4-1.5 nanometers, and the average thickness is about 0.7 nanometers Figure 14 c), corresponding to a single layer.

[0071] Preparation of comparative samples: we directly synthesize transition metal sulfides by powder sintering method as comparative samples to illustrate the difference between the transition metal sulfide quantum sheets prepared by the method of the application. The specific synthesis method is as follows: according to the reported method, tungsten (W), molybdenum (Mo), vanadium (V), scandium (Sc), yttrium (Y) and sulfur powder are uniformly mixed in a molar ratio of 4 / 15:4 / 15:2 / 15:1 / 5:2 / 15:2, and the mixture is sealed in a quartz tube and calcined at 800℃ for 72 hours.

[0072] In order to better illustrate the technical features and technical effects of the application, the prepared high-entropy transition metal chalcogenide (HE-(WMoVScY)S2) quantum sheet is taken as the key point, and further analysis and demonstration are made in combination with test characterization.

[0073] The high-entropy transition metal sulfide quantum sheet of the application is prepared by topological transformation of in-plane ordered MAX (i-MAX) phase and subsequent exfoliation treatment Figure 1Typically, the M layer of the i-MAX phase ((M'2 / 3M”1 / 3)2AlC) is wrinkled, with M' and M” sites close to the X and A layers, respectively. The transition metal atoms at the M” sites are much larger than those at the M' sites. This gives the i-MAX phase high tolerance to transition metal atoms with large size differences within the MX sheets. Based on this principle, (V... 2 / 3 Sc 1 / 3 )2AlC and (W 1 / 2 Mo 1 / 2 ) 4 / 3 (Sc 1 / 2 Y 1 / 2 ) 2 / 3 AlC powder was calcined at 1400℃ to synthesize a high-entropy i-MAX phase (W). 3 / 5 Mo 2 / 5 V 1 / 5 )4 / 3(Sc 3 / 5 Y 2 / 5 )2 / 3AlC.

[0074] In this invention, the multimetal i-MAX phase (W 1 / 2 Mo 1 / 2 ) 4 / 3 The use of (Sc1 / 2Y1 / 2)2 / 3AlC is crucial because its relatively increased entropy at the M' and M” sites favors the formation of the target i-MAX phase containing metal atoms with significant size differences. After calcination, the powder color changes from black to gray, similar to reported MAX phases. The target high-entropy i-MAX phase (W...) 2 / 5 Mo 2 / 5 V 1 / 5 ) 4 / 3 (Sc 3 / 5Y 2 / 5 ) 2 / 3 The X-ray diffraction (XRD) pattern of AlC showed strong and sharp diffraction peaks. Figure 2 The peaks at 13.08°, 26.33°, and 18.93° are attributed to the (002), (004), and (100) crystal planes of the i-MAX phase, respectively, due to its layered ordered structure, similar to the reported (W2 / 3Y1 / 3)2AlC and (W2 / 3Sc1 / 3)2AlC. XRD patterns indicate that the obtained (W... 2 / 5 Mo 2 / 5 V 1 / 5 ) 4 / 3 (Sc 3 / 5 Y 2 / 5 )2 / 3AlC exhibits monoclinic (C2 / c) symmetry, identical to the reported i-MAX phase, indicating that the crystal structure remains unchanged with increasing transition metal species. Due to the different sizes of W, Mo, V, Sc, and Y atoms ( See Table 1 below.

[0075] Table 1. Atomic radii of transition metal elements.

[0076]

[0077] The obtained i-MAX phase ((W 2 / 5 Mo 2 / 5 V 1 / 5 ) 4 / 3 (Sc 3 / 5 Y 2 / 5 ) 2 / 3 AlC, (W 1 / 2 Mo 1 / 2 ) 4 / 3 (Sc 1 / 2 Y 1 / 2 ) 2 / 3 AlC and W 4 / 3 (Sc 1 / 2 Y 1 / 2 ) 2 / 3 AlC) show a shift of the (002) peak related to atomic size ( Figure 2 ). Scanning electron microscope (SEM) images show that the target i-MAX phase has a clear layered structure ( Figure 3 ), which is consistent with the above XRD analysis results. Scanning transmission electron microscope (STEM) and corresponding elemental mapping images clearly reveal the existence and uniform distribution of W, Mo, V, Sc and Y elements ( Figure 4 ).

[0078] In step 2), the target i-MAX phase was reacted under sulfur vapor at 1000℃, during which the Al layers were extracted from the layered structure in the form of gaseous sulfides. At the same time, the MX layers of i-MAX topologically transformed to form two-dimensional transition metal sulfides, which well inherited the layered structure. After the conversion reaction, the sample volume changed about 4 times of the original ( Figure 5 ), and the color also changed from gray to dark blue. The XRD pattern ( Figure 6 ) shows a series of diffraction peaks at 14.3°, 28.9°, 32.8°, 39.6°, 49.7°, 58.5° and 60.5°, corresponding to the (002), (004), (100), (103), (105), (110) and (112) crystal planes of sulfides, respectively, which are similar to WS2(PDF #08-0237). In addition, there are no other sulfide diffraction peaks in the pattern, which is different from the obvious phase separation phenomenon of the sample prepared by direct powder sintering method ( Figure 7 ). SEM images show that the obtained sulfide has a highly expanded accordion-like structure ( Figure 8a) This is likely because the Al layer is rapidly extracted through a gaseous intermediate, similar to expanded graphite, which is significantly different from the i-MAX phase with its compact morphology. Figure 3 Transmission electron microscopy (TEM) images ( Figure 9 ) and high-resolution TEM (HRTEM) images ( Figure 8 c) Further revealed the crystal properties of the layer, with clear lattice fringes spaced at 0.28 nm, corresponding to the spacing of the (100) crystal plane. The hexagonal diffraction spots in the Fast Fourier Transform (FFT) pattern ( Figure 8 The illustration in c further confirms this. STEM and the corresponding elemental mapping image ( Figure 8 b) shows that transition metal species such as W, Mo, V, Sc, and Y are uniformly distributed throughout the sulfide layer. Inductively coupled plasma optical emission spectrometry (ICP-OES) results show that the atomic fractions of W, Mo, V, Sc, and Y are 26.4%, 27.0%, 13.3%, 18.9%, and 14.4%, respectively. Figure 8 i). Based on the calculation of molar configuration entropy, the entropy of the obtained sulfide is 1.57R, satisfying the definition of a high-entropy material with entropy ≥ 1.5R. Therefore, the obtained sulfide is identified as a high-entropy sulfide (HE-(WMoVScY)S2). Notably, the atomic size (atomic radius) difference of this high-entropy sulfide is as high as 11.2% (Table 2 below), which is more than 4 times that of reported transition metal sulfides (δ≤2.8%). The coexistence of such large-size metal atoms in a single plane, as we expected, stems from the high compatibility of the i-MAX phase, which is unattainable by other methods. Such a large size difference results in high strain on the basal surface of the sulfide layer, with the dark blue and white-yellow regions in the strain distribution diagram corresponding to compressive strain and tensile strain, respectively. Figure 8 d, e) highlight this point.

[0079] In other embodiments, by selecting transition metal elements such as W, Mo, Sc, and Y, different elemental compositions of multimetallic i-MAX phases are synthesized, thereby obtaining a series of 1T phase sulfides with large atomic size differences (8.1% ≤ δ ≤ 11.2%). In some embodiments, the transition metal elements can be selected from four or more elements of Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W, Sc, and Y, more preferably five or more. In some embodiments, multimetallic i-MAX phases with atomic size differences > 8% are preferably selected as raw materials, more preferably multimetallic i-MAX phases with atomic size differences > 11% are selected as raw materials.

[0080] Table 2. Atomic size differences (δ) of transition metals calculated based on atomic fractions of W, Mo, V, Sc and Y measured by ICP-OES.

[0081]

[0082] To clearly observe the atomic-scale microstructure of high-entropy sulfides, aberration-corrected scanning transmission electron microscopy (STEM) measurements were performed. Notably, atomic-resolution STEM images show that transition metal atoms are located at the center of octahedral units. Figure 8 f, h), which is consistent with the reported two-dimensional TMDs with a 1T phase. Along Figure 8 Line intensity distribution diagram of the straight line in f ( Figure 8 g) This further confirms the 1T phase, in which the intensity of the metallic sites is much stronger than that of the S sites. Raman spectra at 142.5 cm⁻¹ -1 193.8cm -1 and 372.5cm -1 The three peaks of the J1, J2, and J3 vibration modes of phase 1T are displayed at the locations respectively. Figure 10 Based on the strain analysis above, this 1T phase should be formed by high strain induction from transition metal atoms with large size differences in the crystal lattice. In this way, by selecting transition metal species such as W, Mo, Sc and Y to transform various i-MAX phases, a series of 1T phase sulfides with large atomic size differences (8.1% ≤ δ ≤ 11.2%) can be obtained.

[0083] To characterize the chemical state of the transition metal atoms in the obtained high-entropy 1T phase sulfide, X-ray absorption spectroscopy (XAS) measurements were performed. Figure 13 In sample a, the edge X-ray absorption near-edge structure (XANES) spectrum of the high-entropy sulfide WL3 is similar in shape and absorption edge to that of the WS2 reference sample, indicating that W is in a sulfidation state. Wavelet transform (WT) analysis of the extended X-ray absorption fine structure (EXAFS) spectrum of the WL3 edge further verifies the coordination of WS in the obtained 1T phase HE-(WMoVScY)S2, with its maximum intensity located at... between( Figure 13 (Illustration). Absorption edges in the XANES spectra of Mo and VK edges ( Figure 13 b) and 13c) and WT analysis can similarly verify the sulfidation state and coordination configuration of Mo and V. In Figure 13 In d and 13e, the absorption edges of the K-edge XANES spectra of Sc and Y in the high-entropy 1T phase sulfides overlap with the absorption edges of Sc2S3 and Y2S3, respectively, indicating that Sc and Y elements exist in the form of sulfides. Electron paramagnetic resonance (EPR) spectroscopy shows that the obtained sulfides have a dominant signal at a g value of 2.003. Figure 13 f), corresponding to the empty S position.

[0084] Based on the above high-entropy 1T-phase sulfide with similar accordion structure, ultrasonic treatment was performed in isopropanol (IPA) solvent for the preparation of two-dimensional layered materials. Surprisingly, the dispersion turned brown immediately after ultrasonic treatment, which is different from the traditional liquid phase exfoliation process in which the color gradually changes to dark green. The brown color should be due to the significant reduction in lateral size, similar to the reported quantum dots. TEM and STEM images Figure 14 a, b) show that the exfoliated layered structure has a crystal structure with a lateral size in the range of 2.0-10.0 nanometers. Atomic force microscope (AFM) images further show that its thickness is about 0.5-1.5 nanometers, with a statistical average thickness of about 0.7 nanometers Figure 14 c), corresponding to a single layer.

[0085] The XRD pattern of the brown product shows a series of non-basal plane diffraction peaks at 14.3°, 28.7°, 44.1° and 60.1°, and no other peaks, corresponding to the (002), (004), (006) and (008) crystal planes of the single-layer sulfide, which further confirms its single-layer structure. Compared with the larger-sized (500 nanometers-10 micrometers) nanosheets prepared by traditional exfoliation methods, our small-sized single-layer quantum sheets should be attributed to the above-mentioned high strain in the sulfide plane Figure 8 d, e), which makes the sulfide layer more prone to break during ultrasonic treatment. Unexpectedly, the 1T phase is also well preserved, which is confirmed by the typical J1, J2 and J3 vibration peaks in the Raman spectrum Figure 14 d), which is quite different from most reported sulfide quantum sheets with 2H phase. The good preservation of the 1T phase should be attributed to the large size difference of the introduced transition metal atoms, which effectively slows down the sliding of the basal plane. When excited by a laser with a wavelength of 230-290 nanometers, our high-entropy 1T-phase quantum sheets show obvious photoluminescence (PL) signals in the range of 320-380 nanometers Figure 14 e). With the gradual increase of the excitation wavelength, the PL peak does not shift significantly, showing PL behavior independent of the excitation wavelength, similar to the reported WS2 quantum dots. Under 245 nanometer laser irradiation, the dispersion of 1T-phase quantum sheets emits a weak purple light Figure 14 e inset). The ultraviolet-visible absorption spectrum of the high-entropy 1T-phase sulfide quantum sheets shows strong light absorption ability with a band gap of 3.94 eV Figure 14 f), which is larger than that of the similar accordion structure of disulfide (1.46 eV), which is due to the size-dependent quantum confinement effect.

[0086] Example 2

[0087] Considering the stability of 1T phase and the highly exposed edges, we evaluate that this transition metal sulfide quantum sheet has excellent catalytic performance, which has practical application effect in fields such as photocatalysis, electrocatalysis and the like. Therefore, the application also provides a use of the transition metal sulfide quantum sheet as a catalyst. In the present embodiment, we apply the high-entropy quantum sheet to the conversion of lithium polysulfides (LiPSs) in lithium-sulfur batteries to evaluate its catalytic performance. Specific embodiments are:

[0088] Electrocatalytic test of lithium polysulfide (LiPSs): The obtained two-dimensional sulfide, super carbon black (super P) and polyvinylidene fluoride (PVDF) were ground in a mass ratio of 7:2:1 in NMP solvent to form a uniform slurry, which was then coated on a carbon-coated aluminum foil with a diameter of 12.0 mm. The obtained electrode was dried in a vacuum environment at 50°C for 12 hours. Two identical electrodes, a polypropylene (PP) separator and 40 μL of Li2S6 (0.2M, prepared by reacting Li2S with S) electrolyte were used to assemble a symmetrical battery. The cyclic voltammetry (CV) curve was collected at a scan rate of 5 mVs -1

[0089] Precipitation test of lithium sulfide (Li2S): Two-dimensional sulfide, super carbon black and polyvinylidene fluoride were prepared into a circular electrode as a working electrode in a mass ratio of 5:4:1, and assembled into a 2032 type button cell with a lithium foil counter electrode. 15 μL of Li2S8 (0.2M) solution was used as the cathode electrolyte, and 15 μL of control electrolyte without Li2S8 was used as the anode electrolyte. The button cell was discharged at a current of 100 μA to 2.06 V, and then discharged at a constant potential of 2.05 V to make Li2S nucleate and grow until the current was less than 10 μA. According to Faraday's law, the nucleation capacity of Li2S was calculated by plotting the integral area of the curve.

[0090] Application test of two-dimensional sulfide in lithium-sulfur batteries: The obtained two-dimensional sulfide was applied to the PP separator of lithium-sulfur batteries. The specific operation is to disperse 50wt% of two-dimensional disulfide, 40wt% of super carbon black and 10wt% of polyvinylidene fluoride in NMP solvent to form a uniform slurry, uniformly coat on a 2400 type Celgard polypropylene (PP) separator, and finally dry in a vacuum environment at 50°C for 12 hours.

[0091] ​Electrochemical performance testing of lithium-sulfur batteries: Electrochemical performance testing was conducted based on CR2025 coin cells, with lithium foil as the negative electrode, a sulfur positive electrode (a 90wt% sulfur / carbon composite material containing 30wt% super carbon black and 10wt% polyvinylidene fluoride) as the positive electrode, and a PP membrane coated with two-dimensional sulfides as the separator. A 1.0M LiTFSI solution dissolved in DOL and DME (volume ratio 1:1) with 1wt% LiNO3 was used as the electrolyte. Cyclic performance and rate performance were tested at room temperature using a LANDCT2001A battery testing system within a voltage window of 1.7–2.8 V. Cyclic voltammetry curves were acquired using a CHI760E electrochemical workstation. Electrochemical impedance spectroscopy (EIS) was recorded with an AC voltage amplitude of 5 mV in the frequency range of 100 kHz to 10 mHz.

[0092] Test results show that, in the cyclic voltammetry (CV) curve ( Figure 15 In a), there are two distinct reduction peaks, corresponding to the conversion of S8 to soluble LiPSs (peak 1) and the conversion of LiPSs to solid Li2S2 / Li2S (peak 2), respectively. Conversely, the two oxidation peaks represent the conversion of Li2S2 / Li2S back to S8. The peak spacing between the first cathode peak and the first anodic peak of the high-entropy 1T phase quantum sheet is 37 mV, much lower than that of the 1T phase sulfide nanosheets (411 mV) and the 2H phase WS2 nanosheets (1291 mV). During the conversion of liquid LiPSs to solid Li2S, the Li2S precipitation capacity corresponding to the high-entropy 1T phase quantum sheet at 200 s is 263.7 mAh g. -1 Superior to 1T phase disulfide nanosheets (121.9 mAh g) -1 ,451s) and 2H phase WS2 nanosheets (92.2 mAh g -1 Based on the excellent electrocatalytic properties of the high-entropy 1T phase quantum sheet, a lithium-sulfur battery was assembled, which operated at 0.2C (1C = 1675 mAh g⁻¹). -1 During the initial cycle, the battery had a capacity of 1618 mAh g. -1 It exhibits high discharge capacity and near 100% coulombic efficiency within 200 cycles, demonstrating excellent cycle stability and structural stability. Even when the current rate increases to 1C and 3C, the reversible capacity remains as high as 951 mAh g⁻¹. -1 and 824mAhg -1 Even at a high rate of 5C, it can achieve a capacity of 744mAh. -1 The reversible capacity is far higher than that of 1T phase sulfide nanosheets (413mAh g). -1 ), 2H phase WS2 nanosheets (182mAh g) -1) and reported two-dimensional TMDs materials. Such high rate performance should be related to the 1T phase structure and highly exposed edges, which can facilitate the redox reaction kinetics of sulfur, as evidenced by the low charge transfer resistance and fast lithium ion diffusion rate Figure 17

[0093] Example 3

[0094] The precursor of the topological transformation reaction can also be a MXene material. A two-dimensional transition metal sulfide is generated by performing a topological transformation reaction on a two-dimensional MXene material with a gas containing a sulfur family element, and the two-dimensional transition metal sulfide is also subjected to exfoliation treatment, and a quantum sheet can also be prepared. This embodiment provides an implementation manner taking a MXene material as a raw material, and the steps include:

[0095] 1) Synthesis of high-entropy MXene material

[0096] The i-MAX phase (W 2 / 5 Mo 2 / 5 V 1 / 5 ) 4 / 3 (Sc 3 / 5 Y 2 / 5 ) 2 / 3 AlC etching Al phase, obtaining high-entropy MXene (W 2 / 5 Mo 2 / 5 V 1 / 5 ) 4 / 3 (Sc 3 / 5 Y 2 / 5 ) 2 / 3 CT x , and the specific implementation steps are as follows: the i-MAX phase is placed in a tube furnace, a mixed gas of etching gas and inert gas is introduced into the tube furnace, heated to a predetermined temperature and kept for a period of time, and then cooled to room temperature and taken out, obtaining a powder product. In this embodiment, the etching gas is HCl gas with a volume fraction of 10%, the heating degree is 600 degrees Celsius, and the temperature is kept for 0.5 hours.

[0097] 2) Topological transformation reaction

[0098] The high-entropy MXene prepared in step 1) is subjected to a topological transformation reaction with sulfur vapor to generate a two-dimensional 1T transition metal chalcogenide, and the specific steps include: the atmosphere in the above-mentioned tube furnace is changed to H2S gas, and heated to 1000℃ and kept for 2 hours, obtaining a two-dimensional 1T phase transition metal chalcogenide.

[0099] 3) Exfoliation treatment

[0100] The two-dimensional 1T phase transition metal chalcogenide obtained after exfoliation treatment is subjected to exfoliation treatment by the same liquid phase exfoliation method as in Example 1, obtaining a quantum sheet. ​

[0101] Although MXene can also be prepared as a precursor to quantum sheets, the technical route of using i-MAX phase as a precursor (Example 1) is more preferred in terms of the process of preparation, because the layered etching has been achieved during the topological transformation reaction process, and the preparation process is more simplified.

[0102] Example 4

[0103] In this embodiment, the sulfur vapor is replaced by H2S gas, and the i-MAX phase and the H2S gas are reacted at 1000°C for 2h. After cooling to room temperature, the 1T phase transition metal chalcogenide is obtained, and the quantum sheet is obtained after exfoliation.

[0104] Example 5

[0105] The technical concept of the present application is to construct atomic-level high stress in the transition metal sulfide sheet layer by a multi-metal strategy, and to obtain quantum sheets by exfoliating the sheet layer to produce strain rupture. The high-entropy transition metal sulfide with five or more transition elements is preferably used for exfoliation, that is, the high-entropy MAX phase is preferably used as a precursor in the present application; more preferably, the high-entropy MAX phase precursor with in-plane order is used, which is beneficial to produce stronger stress and strain in the sheet layer, and is more easily to obtain high yield of quantum sheets.

[0106] Another embodiment of the present application, the steps include:

[0107] 1) Synthesis of high-entropy MAX phase precursor:

[0108] Batching step: according to the stoichiometric ratio (molar ratio) of high-entropy two-dimensional material (Ti 0.2 Nb 0.2 Ta 0.2 Zr 0.2 V 0.2 )2AlC is Ti:Nb:Ta:Zr:V:Al:C=0.4:0.4:0.4:0.4:0.4:1:1, the required amount of each element raw material is Ti:Nb:Ta:Zr:V:Al:C=0.4:0.4:0.4:0.4:0.4:1.2:1, and the titanium powder, niobium powder, tantalum powder, zirconium powder, vanadium powder, aluminum powder and graphite are weighed; the above raw materials are mixed by ball milling, wherein the ball-to-material mass ratio is 1:1, the ball milling speed is 600 rpm, and the ball milling time is 20h; the ball-milled powder is transferred to a corundum crucible, heated to 1500°C at 5°C / min under Ar atmosphere, and cooled with the furnace after 1h of heat preservation. The obtained loose bulk after cooling is ground to obtain a high-entropy MAX phase (Ti 0.2 Nb 0.2 Ta 0.2 Zr 0.2 V 0.2)2AlC powder.

[0109] 2) Topotactic transformation reaction

[0110] 0.5 g of the high-entropy MAX phase precursor synthesized in step 1) above and 2.0 g of sulfur powder were placed in two crucibles, respectively, into a tube furnace. The sulfur powder was heated to 150 °C in the upstream region of the furnace, and the high-entropy MAX phase precursor was heated to 1000 °C. The high-entropy MAX phase precursor was kept at 1000 °C for 2 hours in an argon gas stream to obtain accordion-like transition metal sulfide.

[0111] 3) Exfoliation treatment

[0112] 1.0 g of the accordion-like transition metal sulfide powder with accordion-like structure was dispersed in 40 mL of isopropanol solvent and ultrasonically treated at 20 °C for 5 hours. The dispersion was treated by centrifugal separation to obtain transition metal sulfide quantum sheets.

[0113] Supplementary notes on experimental tests and result characterization:

[0114] Preparation of TEM samples: For high-entropy 1T phase transition metal sulfide nanosheets, the accordion-like sample was first dispersed in isopropanol solvent and manually shaken for a few seconds. The diluted dispersion was dropped onto a 200-mesh carbon-coated grid to prepare the TEM sample of two-dimensional nanosheets. For high-entropy 1T phase transition metal sulfide quantum sheets, the accordion-like sample was dispersed in isopropanol and ultrasonically treated. The dispersion was dropped onto a 200-mesh carbon-coated grid after centrifugation to obtain the TEM sample of quantum sheets.

[0115] Calculation of entropy: The entropy of the disulfide prepared by the topotactic transformation method was calculated by the following formula:

[0116]

[0117] where R is the molar gas constant, x i is the atomic fraction of the i-th metal species.

[0118] Calculation of atomic size difference: According to the reported research, the atomic size difference of the sulfide was calculated based on the following formula:

[0119]

[0120] where N is the number of transition metal species, c i represents the atomic fraction of the i-th metal species, r i is the atomic radius of the i-th metal (Table 1). represents the average atomic radius of the transition metal in the obtained two-dimensional sulfide, which is calculated by the following formula:

[0121]

[0122] Characterization methods: XRD tests were performed on a Rigaku Ultima IV diffractometer equipped with a Cu Ka radiation source at a scan speed of 8° min -1 The morphology, microstructure, and crystal structure of the samples were characterized by a scanning electron microscope (HITACHI SU3500), a transmission electron microscope (FEI Tecnai F30) equipped with an X-ray energy spectrometer, and a spherical aberration-corrected scanning transmission electron microscope (FEI Titan Cubed G2 300). Raman spectra were measured on a LabRAM HR Evolution Raman spectrometer using a 633 nm excitation laser. Inductively coupled plasma optical emission spectrometer (ICP-OES) tests were performed on an Agilent ICP-OES 730 spectrometer. The sample thickness was measured using a Bruker Dimension Icon atomic force microscope. Photoluminescence (PL) spectra were recorded with a HITACHI F-700 fluorescence spectrophotometer. Ultraviolet-visible absorption spectra were collected in a diffuse reflectance mode using a Shimadzu UV-3600 analyzer. X-ray absorption spectroscopy (XAS) data were collected at the BL1W1B and BL4B7A beamlines of the Beijing Synchrotron Radiation Facility. Electron paramagnetic resonance spectra were measured by a Bruker A300-10 / 12 instrument.

[0123] The foregoing description of specific exemplary embodiments of the application has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the application to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The exemplary embodiments were chosen and described in order to explain the principles of the application and its practical application and to thereby enable others skilled in the art to best utilize the application and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the application be defined by the claims and their equivalents.

Claims

1. A method of preparing transition metal sulfide quantum sheets, characterized by the steps of Comprising: (a) synthesizing a multi-metal MAX phase precursor, the M site in the MAX phase precursor containing four or more transition metal elements; topologically transforming the MAX phase precursor with a gas containing sulfur elements to generate accordion-like transition metal sulfides; Or, topologically transforming a MXene material with a gas containing sulfur elements to generate transition metal sulfides; the M site in the MXene material containing four or more transition metal elements; (b) exfoliating the above transition metal sulfides to obtain transition metal sulfide quantum sheets; the lateral size of the transition metal sulfide quantum sheets being less than 10 nm.

2. The production method according to claim 1, wherein The transition metal elements in the M site of the MAX phase precursor or the MXene material are selected from Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W, Sc, Y elements; And / or, the average atomic radius difference value in the M site is greater than 8%; And / or, the M site contains five or more transition metal elements; And / or, the transition metal sulfide quantum sheets are single-layer structures; And / or, the lateral size of the transition metal sulfide quantum sheets is 2-10 nm; And / or, the thickness of the transition metal sulfide quantum sheets is 0.5-1.5 nm.

3. The production method according to claim 2, wherein The average atomic radius difference value in the M site is greater than 11%.

4. The production method according to claim 1, wherein The gas containing sulfur elements refers to gaseous sulfur and / or hydrogen sulfide.

5. The production method according to claim 1, wherein The transition metal sulfide quantum sheets are 1T phase or contain 1T phase.

6. The production method according to claim 1, wherein The MAX phase precursor is a multi-metal in-plane ordered structure.

7. The production method according to claim 6, wherein The MAX phase precursor is an in-plane ordered high-entropy MAX phase material.

8. The production method according to any one of claims 1 to 7, wherein The reaction temperature of the topological transformation reaction is between 600 and 1100°C, and the reaction time is 10 minutes to 10 hours; And / or, the exfoliation treatment uses ultrasonic liquid phase exfoliation method.

9. A transition metal sulfide quantum sheet, characterized in that, The transition metal sulfide quantum sheets are composed of transition metal elements M and sulfur elements X, the M contains at least four transition metal elements, and the X is sulfur element; the lateral size of the transition metal sulfide quantum sheets is less than 10 nm; the transition metal sulfide quantum sheets are 1T phase or contain 1T phase.

10. The transition metal sulfide quantum sheet of claim 9, wherein, The M is selected from Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W, Sc, Y elements; And / or, the average atomic radius difference value in the M site is greater than 8%; And / or, the M site contains five or more transition metal elements; And / or, the transition metal sulfide quantum sheets are single-layer structures; And / or, the lateral size of the transition metal sulfide quantum sheets is 2-10 nm; And / or, the thickness of the transition metal sulfide quantum sheets is 0.5-1.5 nm.

11. The transition metal sulfide quantum sheet of claim 10, wherein, The average atomic radius difference value in the M site is greater than 11%.

12. Use of the transition metal sulfide quantum sheets prepared by the preparation method of any one of claims 1 to 8, or the transition metal sulfide quantum sheets of any one of claims 9 to 11 in the field of catalysis, batteries.

13. A catalytic device characterized by, Containing the transition metal sulfide quantum sheets prepared by the preparation method of any one of claims 1 to 8, or the transition metal sulfide quantum sheets of any one of claims 9 to 11.

14. A battery, characterized by A composition comprising the transition metal sulfide quantum plate obtained by the production method according to any one of claims 1 to 8, or the transition metal sulfide quantum plate according to any one of claims 9 to 11.

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