Transition metal sulfide quantum sheet, preparation method thereof, catalytic application and battery

Abstract

The invention discloses a transition metal sulfide quantum sheet and a preparation method, catalytic application and battery thereof, the preparation method comprises the following steps: synthesizing a multi-metal MAX phase precursor, the M site in the MAX phase precursor containing more than four transition metal elements; carrying out topological conversion reaction on the MAX-phase precursor and a gas containing a sulfur element to generate an accordion-like transition metal sulfide; performing stripping treatment on the transition metal sulfide to obtain a transition metal sulfide quantum sheet; and the transverse size of the transition metal sulfide quantum sheet is less than 10nm. The quantum sheet disclosed by the invention shows excellent catalytic performance, such as high electrocatalytic activity on lithium polysulfide.

Description

Technical Field

[0001] The invention belongs to the technical field of nano material preparation, and specifically relates to a transition metal sulfide quantum sheet and a preparation method, catalytic use, and a battery thereof. Background Art

[0002] Two-dimensional (2D) atomic layers, represented by graphene, boron nitride, transition metal chalcogenides (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, 2D TMDs with the general formula MX2 are composed of a hexagonal close-packed transition metal (M = V, Nb, Ta, Mo or W) layer sandwiched between two chalcogen (X = S, Se or Te) layers, forming a typical XMX configuration. In 2D TMDs, the coordination modes of transition metals and surrounding chalcogens can be divided into octahedral and triangular prisms. According to the stacking order of MX2 monolayers, 1T, 2H and 3R phases can be formed. The diverse compositions and polymorphic structures make 2D TMDs exhibit high carrier mobility, variable electronic structure and strong spin-orbit coupling effect, and have broad application prospects in electronics, catalysis and energy storage.

[0003] Both theoretical calculations and experimental results show that the electrical and electrochemical properties of 2D TMDs strongly depend on their lateral size, exposed edges, and structural phases. In this regard, 2D TMDs quantum sheets (QSs) with lateral sizes less than 10 nm have emerged as an important class of nanomaterials that combine the unique properties of 2D nanosheets and quantum dots. Quantum sheets are usually prepared by exfoliation (such as ultrasonic treatment or ball milling) or hydrothermal / solvothermal synthesis methods, followed by separation treatment. Due to the greatly reduced lateral size, the charge carriers in the quantum sheets are confined in all spatial dimensions, and compared with 2D nanosheets, they have higher charge carrier concentrations and mobility, endowing the quantum sheets with high electronic states and strong electric field effects. In addition, 2D TMDs quantum sheets have extremely high edge exposure, which greatly increases the number of electrochemically active sites, significantly improves the reaction current density, accelerates the mass transfer process, and promotes the reaction kinetics. However, current quantum sheets generally have semiconductor behavior associated with the 2H phase. Due to the small lateral size that causes the basal plane to slide easily, the preparation of 1T phase quantum sheets remains a challenge, limiting their application in some fields with specific requirements for the phase structure. Summary of the invention

[0004] The present invention aims to provide a method for preparing transition metal sulfide quantum sheets through a multi-metal strategy, thereby solving the problems of difficulty in preparing quantum sheets and poor phase stability in the prior art.

[0005] The first aspect of the present invention provides a method for preparing a transition metal sulfide quantum sheet, the steps comprising:

[0006] (a) synthesizing a multi-metallic MAX phase precursor, wherein the M position in the MAX phase precursor contains four or more transition metal elements; subjecting the MAX phase precursor to a topochemical transformation reaction with a gas containing sulfur to generate an accordion-shaped transition metal sulfide; or subjecting a MXene material to a topochemical transformation reaction with a gas containing sulfur to generate a transition metal sulfide; wherein the M position in the MXene material contains four or more transition metal elements;

[0007] (b) exfoliating the transition metal sulfide to obtain a transition metal sulfide quantum sheet; the lateral size of the transition metal sulfide quantum sheet is less than 10 nm.

[0008] In some embodiments, the M-position transition metal element in the above-mentioned MAX phase precursor or the above-mentioned MXene material is selected from Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W, Sc, and Y elements.

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

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

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

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

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

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

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

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

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

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

[0019] In some embodiments, the stripping process is performed by ultrasonic liquid phase stripping.

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

[0021] In some embodiments, the transition metal element M is selected from Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W, Sc, and Y elements.

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

[0023] In some embodiments, the transition metal element M contains five or more transition metal elements.

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

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

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

[0027] The third aspect of the present invention provides a use of the above transition metal sulfide quantum sheet in the fields of catalysis and batteries.

[0028] A fourth aspect of the present invention provides a catalytic device comprising the above-mentioned transition metal sulfide quantum sheet.

[0029] A fifth aspect of the present invention provides a battery comprising the above-mentioned transition metal sulfide quantum sheet.

[0030] The present invention provides an efficient multi-metal strategy, which slows down the basal plane sliding by controllably introducing multiple metal atoms with large size differences, thereby preparing phase quantum sheets of transition metal sulfides. The key lies in the topological transformation of multi-metal carbide layers (MAX) into multi-metal transition metal sulfides with high strain, which can easily break the material into quantum sheets during the peeling process. Due to the stability of the quantum sheets and the highly exposed edges, the quantum sheets of the present invention exhibit excellent catalytic performance, such as high electrocatalytic activity for lithium polysulfide, and achieve 744mAh g at 5C rate in lithium-sulfur batteries. -1 Good rate performance and long cycle stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a schematic diagram of the atomic structure changes during the preparation of the transition metal sulfide quantum sheet of the present invention.

[0032] Figure 2 The X-ray diffraction (XRD) pattern of the i-MAX phase containing selected transition metal atoms such as W, Mo, V, Sc and Y of the present invention shows sharp and prominent diffraction peaks belonging to the i-MAX phase, and the displacement of the (002) peak with the change of atomic size. Among them, the XRD pattern of the multi-metal i-MAX phase shows sharp and strong characteristic (002), (004) and (110) diffraction peaks belonging to the i-MAX phase. For W 4 / 3 (Sc 1 / 2 Y 1 / 2 ) 2 / 3 AlC, (002) peak is located at 12.97°, slightly higher than (W 2 / 3 Y 1 / 3 )2AlC(12.93°), which is attributed to the introduction of the atomic radius ratio Y Small Sc The interlayer spacing is reduced. Due to the atomic radius of Mo W Small, (W 1 / 2 Mo 1 / 2 ) 4 / 3 (Sc 1 / 2 Y 1 / 2 ) 2 / 3 The (002) peak of AlC shifts up to 12.99°. 2 / 5 Mo 2 / 5 V 1 / 5 ) 4 / 3 (Sc 3 / 5 Y 2 / 5 ) 2 / 3 The (002) peak of AlC further shifts to 13.08°, which is due to the smallest atomic radius. This is caused by the introduction of V atoms.

[0033] Figure 3 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 / 3 AlC, c)W4 / 3 (Sc 1 / 2 Y 1 / 2 ) 2 / 3 AlC and d)(W 2 / 3 Y 1 / 3 )SEM image of 2AlC, showing the typical layered structure.

[0034] Figure 4 is the high entropy i-MAX phase (W 2 / 5 Mo 2 / 5 V 1 / 5 ) 4 / 3 (Sc 3 / 5 Y 2 / 5 ) 2 / 3 The STEM image (a) and corresponding elemental mapping image of AlC show the coexistence and uniform distribution of W (b), Mo (c), V (d), Sc (e) and Y (f) species. According to the test results, the elements in other i-MAX phases also have the phenomenon of multi-element coexistence and uniform distribution (figure omitted).

[0035] Figure 5 This is a photograph of 3.0 g of the high-entropy i-MAX phase (W2 / 5Mo2 / 5V1 / 5)4 / 3(Sc3 / 5Y2 / 5)2 / 3AlC (a) of the present invention and its derived accordion-shaped 1T phase sulfide (HE-(WMoVScY)S2) (b), wherein the volume of the resulting sulfide is approximately 4 times that of the i-MAX phase.

[0036] Figure 6 is the high entropy i-MAX phase (W 2 / 5 Mo 2 / 5 V 1 / 5 ) 4 / 3 (Sc 3 / 5 Y 2 / 5 ) 2 / 3 The XRD pattern of the 1T phase accordion-shaped HE-(WMoVScY)S2 produced by topological transformation of AlC under the action of sulfur vapor shows the disappearance of the i-MAX phase peak and the presence of the characteristic diffraction peak of sulfide.

[0037] Figure 7 a) is a schematic diagram of a comparative polymetallic sulfide prepared by a powder sintering method according to the present invention and b) is an XRD spectrum of the obtained product, showing that the product is a mixture of sulfides (WS2, MoV2S4, YS and Y2S3), indicating that severe phase separation occurs during the reaction process.

[0038] Figure 8 The morphology and structure analysis of the high entropy 1T phase transition metal sulfide of the present invention. a) The high entropy i-MAX phase (W 2 / 5Mo 2 / 5 V 1 / 5 )4 / 3 (Sc 3 / 5 Y 2 / 5 ) 2 / 3 Scanning electron microscopy (SEM) image of the accordion-like disulfide prepared by AlC topomorphic transformation, showing a highly expanded structure. b) Scanning transmission electron microscopy (STEM) image of the sulfide layer and the corresponding element distribution map, revealing the presence and uniform dispersion of Mo, W, V, Sc and Y elements. c) High-resolution transmission electron microscopy (HRTEM) image of the HE-(WMoVScY)S2 layer and the corresponding fast Fourier transform (FFT) map (inset), showing clear lattice fringes with crystalline characteristics. d, e) Along e xx (d) and e xy (e) Strain distribution in the direction, indicating the presence of tensile strain (white-yellow area) and compressive strain (dark blue area) on the basal plane. f, g) Atomic resolution STEM image (f) and line intensity distribution corresponding to line 1 (g), indicating that the transition metal is located at the center of the octahedral unit of the 1T phase. h) Atomic model of 1T phase high entropy sulfide, top view and side view, respectively. i) Atomic fraction of transition metal atoms such as W, Mo, V, Sc and Y in high entropy sulfide.

[0039] Fig. 9 a) TEM and b) HRTEM images of the two-dimensional HE-(WMoVScY)S2 of the present invention, showing ultrathin and single-crystalline characteristics (inset).

[0040] Fig.10 The Raman spectrum of HE-(WMoVScY)S2 of the present invention reveals the existence of J1, J2 and J3 vibration modes of the 1T phase.

[0041] Fig.11 The XRD patterns of other accordion-shaped 1T phase transition metal sulfides prepared by topological conversion reactions of different i-MAX phases in the present invention show no characteristic peaks of the i-MAX phase, proving the complete conversion of the i-MAX phase under sulfur vapor.

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

[0043] Fig.13The chemical states of transition metals and sulfur species in the high entropy 1T phase sulfide of the present invention. ac) W L3-edge (a), Mo K-edge (b), V K-edge (c) XANES spectra of the high entropy 1T phase sulfide and the corresponding WT analysis (inset), showing similar shapes and absorption edges as those in the reference and the sulfidation states of W, Mo and V. d, e) ScK-edge (d) and Y K-edge (e) XANES spectra of the high entropy 1T phase sulfide, revealing that the absorption edge is close to the sulfide. F) EPR spectrum, showing the characteristic signal of S vacancy at g = 2.003.

[0044] Fig.14 The morphology and structure characterization of the high entropy 1T phase quantum sheet of the transition metal sulfide of the present invention. a) Transmission electron microscope image and statistical analysis of the lateral size of the obtained quantum sheet (inset), showing that the average lateral size is 4.5 nanometers. b) Atomic resolution STEM image and corresponding FFT pattern (inset), showing a crystal structure with hexagonally stacked transition metal atoms. c) Atomic force microscope image and statistical analysis of the thickness of the quantum sheet (inset), showing an average thickness of 0.7 nanometers. d) Raman spectrum of HE-(WMoVScY)S2 quantum sheet, revealing the existence of 1T phase J1, J2 and J3 vibration modes. e) PL spectrum of high entropy 1T phase quantum sheet, by using a laser with a wavelength of 230-290nm and emitting violet light, shows a clear peak at 320 to 380nm (inset). f) Tacu diagram and UV-visible spectrum (inset) of high entropy 1T phase quantum sheet, showing a band gap of 3.94eV.

[0045] Fig.15 The electrochemical properties of the high entropy 1T phase quantum sheets of transition metal sulfides of the present invention. a, b) CV curves of Li2S6 symmetric cells (a) and Li2S precipitation in Li-LiPSs cells with Li2S8 cathode electrolyte (b), showing the high electrocatalytic activity of LiPSs and the high precipitation capacity of Li2S for 1T phase HE-(WMoVScY)S2 quantum sheets. c, d) Voltage distribution (c) and rate performance (d) at different rates from 0.2 to 5C, showing the typical voltage platform of sulfur redox reaction and the high rate performance of high entropy 1T phase sulfide quantum sheets.

[0046] Fig.16 The cycling performance of the Li-S battery with 1T phase HE-(WMoVScY)S2 quantum sheet at 0.2C is shown in Figure 2, which shows 897 mAh g after 200 cycles. -1 The high reversible capacity and Coulombic efficiency are close to 100%.

[0047] Fig.17This is an EIS image of the Li-S battery of the present invention having 1T phase HE-(WMoVScY)S2 quantum sheet, 1T phase (WScY)S2 nanosheet and 2H phase WS2 nanosheet, wherein the HE-(WMoVScY)S2 quantum sheet has a small semicircle, indicating that the charge transfer resistance is the lowest (14.4Ω), and the charge transfer resistances of the 1T phase (WScY)S2 nanosheet and the 2H phase WS2 nanosheet are 32.1Ω and 49.8Ω, respectively. DETAILED DESCRIPTION

[0048] The technical solution of the present invention is described below by specific embodiments. It should be understood that one or more steps mentioned in the present invention do not exclude the existence of other methods and steps before and after the combination step, 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 present invention and are not used to limit the scope of the present invention. Unless otherwise specified, the numbering of each method step is only for the purpose of identifying each method step, and does not limit the order of arrangement of each method or limit the scope of implementation of the present invention. The change or adjustment of the relative relationship thereof can also be regarded as the scope of implementation of the present invention without substantial changes in the technical content.

[0049] The sources of the raw materials and instruments used in the examples are not particularly limited and can be purchased from the market or prepared according to conventional methods known to those skilled in the art.

[0050] Example 1

[0051] This embodiment provides a transition metal sulfide quantum sheet and a preparation method thereof. The preparation process diagram is shown in FIG. Figure 1 As shown, the transition metal sulfide quantum sheet constituent elements include four or five of the transition metal elements W, Mo, V, Sc and Y, and the steps include:

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

[0053] The multi-metal i-MAX phase precursor is synthesized by solid phase reaction at high temperature. 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 powders were ball milled in a molar ratio of 4 / 3:1 / 3:1 / 3:1.3:1, cold pressed under a pressure of 10 MPa, and then sintered at 1450°C for 2 h in an argon gas flow.

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

[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 powders were ball milled in a molar ratio of 2 / 3:2 / 3:1 / 3:1 / 3:1.3:1, cold pressed at a pressure of 10 MPa, and then sintered at 1500°C for 10 hours under argon protection.

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

[0058] i-MAX phase (W 2 / 5 Mo 2 / 5 V 1 / 5 ) 4 / 3 (Sc 3 / 5 Y 2 / 5 ) 2 / 3 Synthesis of AlC: 1 / 2 Mo 1 / 2 ) 4 / 3 (Sc 1 / 2Y 1 / 2 ) 2 / 3 AlC and (V 2 / 3 Sc 1 / 3 )2AlC is synthesized by solid phase reaction at high temperature. Specifically, (W 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 at 25 MPa, and then sintered at 1400 °C for 2 h in an argon gas stream. The block product was ground to obtain powder (W 2 / 5 Mo 2 / 5 V 1 / 5 ) 4 / 3 (Sc 3 / 5Y2 / 5 ) 2 / 3 AlC.

[0059] 2) Topological transformation reaction

[0060] The i-MAX phase precursor is subjected to a topological conversion reaction with sulfur vapor to generate an accordion-like 1T transition metal chalcogenide compound. The specific steps include:

[0061] 0.5 g of the i-MAX phase precursor synthesized in step 1) above and 2.0 g of sulfur powder were placed in two crucibles respectively and placed in a tube furnace. The sulfur powder was heated to 150°C in the upstream area of ​​the furnace, and the i-MAX phase precursor was heated to 1000°C. In an argon gas flow, the i-MAX phase precursor was kept at 1000°C for 2 hours to obtain an accordion-like 1T phase transition metal chalcogenide compound.

[0062] Among them, i-MAX phase (W 2 / 5 Mo 2 / 5 V 1 / 5 ) 4 / 3 (Sc 3 / 5 Y 2 / 5 ) 2 / 3 The product obtained by using AlC as the raw material is labeled as HE-(WMoVScY)S2;

[0063] i-MAX phase (W 1 / 2 Mo 1 / 2 )4 / 3(Sc 1 / 2 Y 1 / 2 ) 2 / 3 The product obtained by using AlC as the raw material is labeled as (WMoScY)S2;

[0064] i-MAX Phase W 4 / 3 (Sc 1 / 2 Y 1 / 2 ) 2 / 3 The product obtained by using AlC as the raw material is labeled 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) Peeling treatment

[0067] This step provides external force by exfoliation to prepare transition metal sulfide quantum sheets. In this embodiment, the classic 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 an accordion-like structure is dispersed in 40 mL of isopropanol solvent, ultrasonically treated at 20° C. for 5 hours, and the dispersion is centrifuged.

[0068] In other embodiments, the solvent in the liquid phase stripping 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 transition metal sulfides containing four or more transition metals: HE-(WMoVScY)S2 and (WMoScY)S2 can be stripped to obtain quantum sheets, which is related to the high stress in the multi-metal transition metal sulfide layers. The products obtained by stripping other sulfides containing three or fewer transition metal components are two-dimensional nanosheets (non-quantum sheets) with lateral dimensions ranging from 500nm to hundreds of microns. From the perspective of the stripping yield of quantum sheets, through high-resolution transmission electron microscopy observation, HE-(WMoVScY)S2 was completely stripped to obtain quantum sheets with a yield close to 100%, while (WMoScY)S2 could only be partially stripped to obtain quantum sheets.

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

[0071] Preparation of control samples: We directly synthesized transition metal sulfides by powder sintering method as control samples to illustrate the difference between transition metal sulfide quantum sheets prepared by the method of the present invention. The specific synthesis method is as follows: According to the reported method, tungsten (W), molybdenum (Mo), vanadium (V), scandium (Sc), yttrium (Y) and sulfur powders 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°C for 72 hours.

[0072] In order to better illustrate the technical features and effects of the present invention, the prepared high entropy transition metal sulfide (HE-(WMoVScY)S2) quantum sheet is taken as the focus, and further analyzed and demonstrated in combination with test characterization.

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

[0074] The use of the multimetallic i-MAX phase (W1 / 2Mo1 / 2)4 / 3(Sc1 / 2Y1 / 2)2 / 3AlC in the present invention is crucial because its relatively increased entropy at the M' and M" sites is conducive to the formation of the target i-MAX phase containing metal atoms with large size differences. The color of the powder changes from black to gray after calcination, which is similar to the reported MAX phase. The X-ray diffraction (XRD) pattern of the target high-entropy i-MAX phase (W2 / 5Mo2 / 5V1 / 5)4 / 3(Sc3 / 5Y2 / 5)2 / 3AlC shows 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, which is due to its layered ordered structure, similar to the reported (W2 / 3Y1 / 3)2AlC and (W2 / 3Sc1 / 3)2AlC. The XRD spectrum results show that the obtained (W2 / 5Mo2 / 5V1 / 5)4 / 3(Sc3 / 5Y2 / 5)2 / 3AlC has a monoclinic (C2 / c) symmetry, which is the same as the reported i-MAX phase, indicating that the crystal structure does not change with the increase of transition metal species. Due to the different sizes of W, Mo, V, Sc and Y atoms ( Please 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 The (002) peak of AlC) shows a shift related to the atomic size ( Figure 2 ). Scanning electron microscopy (SEM) images show that the target i-MAX phase has a distinct layered structure ( Figure 3 ), which is consistent with the above XRD analysis results. Scanning transmission electron microscopy (STEM) and the corresponding elemental mapping images clearly reveal the presence and uniform distribution of W, Mo, V, Sc and Y elements ( Figure 4 ).

[0078] In step 2), the target i-MAX phase reacts under sulfur vapor at 1000°C, during which the Al layer is extracted from the layered structure in the form of gaseous sulfides. At the same time, the MX layer of i-MAX undergoes a topological transformation to form a two-dimensional transition metal sulfide that inherits its layered structure well. After the conversion reaction, the sample volume changes by about 4 times ( Figure 5 ), the color also changes from gray to dark blue. XRD spectrum ( 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 sulfide, respectively, which is similar to WS2 (PDF#08-0237). In addition, there are no diffraction peaks of other sulfides in the spectrum, which is different from the obvious phase separation phenomenon of the samples prepared by direct powder sintering method ( Figure 7 ). SEM images show that the resulting sulfide has a highly expanded accordion-like structure ( Figure 8 a), which should be due to the rapid extraction of the Al layer through the gaseous intermediate, similar to expanded graphite, which is significantly different from the i-MAX phase with a compact morphology ( Figure 3 ). Transmission electron microscopy (TEM) image ( Fig. 9 ) and high-resolution TEM (HRTEM) images ( Figure 8c) further reveals the crystalline nature of the layer, with clear lattice fringes and a spacing of 0.28 nm, corresponding to the spacing of the (100) crystal plane. The hexagonal arrangement of diffraction spots in the Fast Fourier Transform (FFT) spectrum ( Figure 8 This is further confirmed by STEM and corresponding elemental mapping images ( 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 spectrometer (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). According to the calculation of molar configurational entropy, the entropy of the obtained sulfide is 1.57R, which meets the definition of high entropy material with entropy ≥ 1.5R. Therefore, the obtained sulfide was determined to be a high entropy sulfide (HE-(WMoVScY)S2). It is worth noting that the atomic size (atomic radius) of this high entropy sulfide differs by as much as 11.2% (Table 2 below), which is more than 4 times that of the reported transition metal sulfides (δ≤2.8%). The coexistence of metal atoms with such large size differences in one plane is, as we expected, due to the high compatibility of the i-MAX phase, which cannot be achieved by other methods. Such a large size difference causes high strain on the basal plane of the sulfide layer. The dark blue and white-yellow areas in the strain distribution diagram correspond to compressive strain and tensile strain, respectively ( Figure 8 d, e), highlighting this point.

[0079] In other embodiments, by selecting transition metal elements such as W, Mo, Sc and Y, different elements are synthesized to form a multi-metal i-MAX phase, 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 of the elements Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W, Sc, and Y, and more preferably, five or more. In some embodiments, a multi-metal i-MAX phase with an atomic size difference of >8% is preferably used as a raw material, and more preferably, a multi-metal i-MAX phase with an atomic size difference of >11% is selected as a raw material.

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

[0081]

[0082] In order to clearly observe the atomic-scale microstructure of high-entropy sulfides, spherical aberration-corrected scanning transmission electron microscopy measurements were performed. Notably, atomic-resolution STEM images show that transition metal atoms are located at the center of the octahedral unit ( Figure 8 f, h), which is consistent with the reported 2D TMDs with 1T phase. Figure 8 Line intensity distribution diagram of the straight line in f ( Figure 8 g) Further confirmation of the 1T phase, where the intensity of the metal site is much stronger than that of the S site. Raman spectrum at 142.5 cm -1 、193.8cm -1 and 372.5cm -1 The three peaks of the J1, J2 and J3 vibration modes of the 1T phase are shown at Fig.10 ). Combined with the above strain analysis, this 1T phase should be induced by the high strain produced by transition metal atoms with large size differences in the lattice. In this way, by selecting transition metal species such as W, Mo, Sc and Y, and transforming a variety of i-MAX phases, a series of 1T phase sulfides with large atomic size differences (8.1%≤δ≤11.2%) can be obtained.

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

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

[0085] The XRD pattern of the brown product shows a series of non-basal 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 monolayer sulfide, which further confirms its monolayer structure. Compared with the nanosheets with larger lateral sizes (500 nanometers-10 microns) prepared by traditional exfoliation methods, the small size of the monolayer quantum sheets prepared by us should be attributed to the high strain in the sulfide plane observed above ( Figure 8 d, e), this high strain makes the sulfide layer more susceptible to fracture during ultrasonic treatment. Unexpectedly, the 1T phase is also well preserved, as confirmed by the typical J1, J2, and J3 vibration peaks in the Raman spectrum ( Fig.14 d), which is very different from most reported sulfide quantum sheets with 2H phase. The good retention of 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 with laser light with a wavelength of 230-290 nm, our high-entropy 1T phase quantum sheets show obvious photoluminescence (PL) signals in the range of 320-380 nm ( Fig.14 e). As the excitation wavelength gradually increases, the PL peak does not shift significantly, showing PL behavior that is independent of the excitation wavelength, similar to the reported WS2 quantum dots. Under 245 nm laser irradiation, the dispersion of 1T phase quantum sheets emits a faint purple light ( Fig.14 e illustration). The UV-visible absorption spectrum of the high-entropy 1T phase sulfide quantum sheet shows strong light absorption ability and a band gap of 3.94 eV ( Fig.14 f), which is larger than that of the accordion-like disulfide (1.46 eV), which is due to the size-related quantum confinement effect.

[0086] Example 2

[0087] Considering the stability of the 1T phase and the highly exposed edges, we evaluate that this transition metal sulfide quantum sheet has excellent catalytic performance and has practical application effects in fields such as photocatalysis and electrocatalysis. Therefore, the present invention also provides a use of a transition metal sulfide quantum sheet as a catalyst. In this example, we applied high entropy quantum sheets to the conversion of polysulfides (LiPSs) in lithium-sulfur batteries to evaluate their catalytic performance. The specific implementation plan is:

[0088] Electrocatalytic test of lithium polysulfide (LiPSs): The obtained two-dimensional sulfide, super carbon black (super P) and polyvinylidene fluoride (PVDF) were ground in NMP solvent at a mass ratio of 7:2:1 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 under vacuum at 50°C for 12 hours. A symmetric cell was assembled using two identical electrodes, a polypropylene (PP) diaphragm and 40 μL Li2S6 (0.2M, prepared by the reaction of Li2S and S) electrolyte. In the voltage range of -1V to 1V, the electrocatalytic performance was 5mVs -1 Cyclic voltammetry (CV) curves were collected at a scan rate of .

[0089] Precipitation test of lithium sulfide (Li2S): Two-dimensional sulfide, super carbon black and polyvinylidene fluoride were made into circular electrodes in a mass ratio of 5:4:1 as working electrodes, and assembled into 2032 button cells with lithium foil counter electrodes. 15μL Li2S8 (0.2M) solution was used as the cathode electrolyte, and 15μL control electrolyte without Li2S8 was used as the anode electrolyte. The button cell was discharged at a constant current of 100μA to 2.06V, and then discharged at a constant potential of 2.05V to allow Li2S to nucleate and grow until the current was less than 10μA. 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 battery: The obtained two-dimensional sulfide is applied to the PP separator of lithium-sulfur battery. 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, evenly coat it on 2400 type Celgard polypropylene (PP) separator, and finally dry it at 50℃ vacuum environment for 12 hours.

[0091] Electrochemical performance test of lithium-sulfur battery: Electrochemical performance test was carried out based on CR2025 button cell, in which lithium foil was used as negative electrode, sulfur positive electrode (90wt% sulfur / carbon composite material containing 30wt% super carbon black and 10wt% polyvinylidene fluoride) was used as positive electrode, and PP diaphragm coated with two-dimensional sulfide was used as diaphragm. A 1.0MLiTFSI solution dissolved in DOL and DME (volume ratio 1:1) and added with 1wt% LiNO3 was used as the electrolyte. At room temperature, the cycle performance and rate performance of the battery were tested in the 1.7-2.8V voltage window using the LANDCT2001A battery test system. The cyclic voltammetry curve was collected by the CHI760E electrochemical workstation. Electrochemical impedance spectroscopy (EIS) was recorded with an AC voltage amplitude of 5mV in the frequency range of 100kHz to 10mHz.

[0092] The test results show that in the cyclic voltammetry (CV) curve ( Fig.15In a), there are two obvious reduction peaks, corresponding to the conversion of S8 into soluble LiPSs (peak 1) and the conversion of LiPSs into solid Li2S2 / Li2S (peak 2). In contrast, the two oxidation peaks represent the conversion of Li2S2 / Li2S back to S8. The peak spacing between the first cathode peak and the first anode peak of the high-entropy 1T phase quantum sheet is 37 mV, which is much lower than that of 1T phase sulfide nanosheets (411 mV) and 2H phase WS2 nanosheets (1291 mV). During the conversion of liquid LiPSs into solid Li2S, the Li2S precipitation capacity corresponding to the high-entropy 1T phase quantum sheet at 200 s is 263.7 mAh g -1 , which is better than 1T phase disulfide nanosheets (121.9 mAhg -1 , 451s) and 2H phase WS2 nanosheets (92.2mAhg -1 Based on the good electrocatalytic properties of the high entropy 1T phase quantum sheet, a lithium-sulfur battery was assembled. -1 ) in the initial cycle, the battery has 1618 mAhg -1 The high discharge capacity of the battery is close to 100% within 200 cycles, showing good cycle stability and good structural stability. When the current rate is increased to 1C and 3C, the reversible capacity is still as high as 951mAhg -1 and 824mAhg -1 Even at a high rate of 5C, it can achieve 744mAhg -1 The reversible capacity is much higher than that of 1T phase sulfide nanosheets (413 mAh g -1 ), 2H phase WS2 nanosheets (182 mAhg -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 promote the redox reaction kinetics of sulfur, as evidenced by the low charge transfer resistance and fast lithium ion diffusion rate ( Fig.17 ).

[0093] Example 3

[0094] The precursor of the topochemical transformation reaction can also be a MXene material. A two-dimensional MXene material and a gas containing a chalcogen element undergo a topochemical transformation reaction to generate a two-dimensional transition metal sulfide, and then the two-dimensional transition metal sulfide is stripped to obtain a quantum sheet. This embodiment provides an implementation method using a MXene material as a raw material, and the steps include:

[0095] 1) Synthesis of high entropy MXene materials

[0096] The i-MAX phase (W 2 / 5Mo 2 / 5 V 1 / 5 ) 4 / 3 (Sc 3 / 5 Y 2 / 5 ) 2 / 3 AlC etches Al phase to obtain high entropy MXene (W 2 / 5 Mo 2 / 5 V 1 / 5 ) 4 / 3 (Sc 3 / 5 Y 2 / 5 ) 2 / 3 CT x , the specific implementation steps are: placing the i-MAX phase in a tube furnace, introducing a mixed gas of etching gas and inert gas into the furnace, heating to a predetermined temperature and keeping the temperature for a period of time, and then cooling to room temperature and taking it out to obtain a powder product. In this embodiment, the etching gas is HCl gas with a volume fraction of 10%, heating to 600 degrees Celsius, and keeping the temperature 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 compound. The specific steps include: changing the atmosphere in the above-mentioned tube furnace to H2S gas, and heating to 1000°C for 2 hours to obtain a two-dimensional 1T phase transition metal chalcogenide compound.

[0099] 3) Peeling treatment

[0100] The quantum sheet is obtained by exfoliating the 1T-phase transition metal sulfide compound using the same liquid phase exfoliation method as in Example 1.

[0101] Although MXene can also be used as a precursor to prepare quantum chips, from the perspective of the preparation process, it is more preferred to adopt the technical route using the i-MAX phase as a precursor (Example 1), because layered etching has been achieved during the topological transformation reaction process, and the preparation process is simpler.

[0102] Example 4

[0103] This embodiment is similar to embodiment 1, except that sulfur vapor is replaced by H2S gas, and the i-MAX phase and H2S gas are kept at 1000°C for 2 hours, cooled to room temperature and then taken out, and 1T phase transition metal chalcogenide compounds are also obtained, and quantum sheets are obtained after exfoliation treatment.

[0104] Example 5

[0105] The technical concept of the present invention is to construct high stress at the atomic level in the transition metal sulfide layer through a multi-metal strategy, and to produce strain fracture by exfoliating the layer to obtain quantum sheets. It is preferred that a high-entropy transition metal sulfide composed of 5 or more transition elements is exfoliated, that is, the present invention preferably uses a high-entropy MAX phase as a precursor; more preferably, an in-plane ordered high-entropy MAX phase precursor is used, which is conducive to generating stronger stress and strain in the layer, and it is easier to obtain a high-yield quantum sheet.

[0106] In another implementation manner of this embodiment, the steps include:

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

[0108] Preparation steps: According to the chemical formula of high entropy two-dimensional materials (Ti 0.2 Nb 0.2 Ta 0.2 Zr 0.2 V 0.2 )2AlC has a stoichiometric ratio (molar ratio) of Ti:Nb:Ta:Zr:V:Al:C=0.4:0.4:0.4:0.4:0.4:1:1, and the required amount of raw materials of each element is according to Ti:Nb:Ta:Zr:V:Al:C=0.4:0.4:0.4:0.4:0.4:1.2:1. Titanium powder, niobium powder, tantalum powder, zirconium powder, vanadium powder, aluminum powder and graphite are weighed; the above raw materials are ball-milled and mixed, wherein the ball-to-material mass ratio is 1:1, the ball milling speed is 600rpm, and the ball milling time is 20h; the ball-milled powder is transferred to a corundum crucible, and the temperature is increased to 1500℃ at 5℃ / min under Ar atmosphere, and after keeping warm for 1h, it is cooled with the furnace, and the loose block obtained after cooling is taken out and 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) Topological 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 and placed in a tube furnace. The sulfur powder was heated to 150° C. in the upstream area of ​​the furnace, and the high entropy MAX phase precursor was heated to 1000° C. In an argon gas flow, the high entropy MAX phase precursor was kept at 1000° C. for 2 hours to obtain an accordion-like transition metal sulfide.

[0111] 3) Peeling treatment

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

[0113] Additional notes on experimental testing and result characterization:

[0114] Preparation of transmission electron microscopy (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 added dropwise to a 200-mesh porous carbon net to obtain a TEM sample of a two-dimensional nanosheet. For high entropy 1T phase transition metal sulfide quantum sheets, the accordion-like sample was dispersed in isopropanol and ultrasonically treated. The dispersion was centrifuged and then added dropwise to a 200-mesh porous carbon net to obtain a TEM sample of a quantum sheet.

[0115] Calculation of entropy: The entropy of disulfide prepared by topo-conversion method is calculated by the following formula:

[0116]

[0117] Where R is the molar gas constant, x i is the atomic fraction of the ith metal species.

[0118] Calculation of atomic size differences: Based on reported studies, the atomic size differences of sulfides were 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 ith metal species, r i is the atomic radius of the ith metal (Table 1). represents the average atomic radius of the transition metal in the obtained two-dimensional sulfide calculated by the following formula:

[0121]

[0122] Characterization method: XRD test was carried out on a Rigaku UltimaIV diffractometer equipped with a Cu Kα radiation source with a scanning speed of 8°min -1. The morphology, microstructure and crystal structure of the samples were characterized by scanning electron microscopy (HITACHI SU3500), transmission electron microscopy equipped with X-ray spectrometer (FEI Tecnai F30) and spherical aberration corrected scanning transmission electron microscopy (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. Sample thickness was measured using a Bruker Dimension Icon atomic force microscope. Photoluminescence (PL) spectra were recorded using a HITACHI F-700 fluorescence spectrophotometer. UV-visible absorption spectra were collected using a Shimadzu UV-3600 analyzer in diffuse reflectance mode. X-ray absorption spectroscopy (XAS) data were collected at the BL1W1B and BL4B7A beamlines at the Beijing Synchrotron Radiation Facility. Electron paramagnetic resonance spectra were measured using a Bruker A300-10 / 12 instrument.

[0123] The foregoing description of specific exemplary embodiments of the present invention is for the purpose of illustration and demonstration. These descriptions are not intended to limit the present invention to the precise form disclosed, and it is clear that many changes and variations can be made based on the above teachings. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical application, so that those skilled in the art can realize and utilize various different exemplary embodiments of the present invention and various different selections and changes. The scope of the present invention is intended to be limited by the claims and their equivalents.

Claims

1. A method for preparing a transition metal sulfide quantum sheet, characterized in that the steps include: (a) synthesizing a multi-metal MAX phase precursor, wherein the M position in the MAX phase precursor contains four or more transition metal elements; subjecting the MAX phase precursor to a topological transformation reaction with a gas containing sulfur to generate an accordion-shaped transition metal sulfide; Or, a MXene material is subjected to a topological transformation reaction with a gas containing sulfur element to generate a transition metal sulfide; the M position in the MXene material contains four or more transition metal elements; (b) exfoliating the transition metal sulfide to obtain a transition metal sulfide quantum sheet; the lateral size of the transition metal sulfide quantum sheet is less than 10 nm.

2. The preparation method according to claim 1 or 2, characterized in that: The M-position transition metal element in the MAX phase precursor or the MXene material is selected from Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W, Sc, and Y elements; and / or, the average atomic radius difference in the M positions is greater than 8%, preferably greater than 11%; And / or, the M position contains five or more transition metal elements; And / or, the transition metal sulfide quantum sheet is a single-layer structure; And / or, the lateral size of the transition metal sulfide quantum sheet is 2-10 nm; And / or, the transition metal sulfide quantum sheet has a thickness of 0.5-1.5 nm.

3. The preparation method according to claim 1, characterized in that: The gas containing sulfur element refers to gaseous sulfur and / or hydrogen sulfide.

4. The preparation method according to claim 1, characterized in that: The high entropy transition metal sulfide quantum sheet is a 1T phase, or contains a 1T phase; Alternatively, the MAX phase precursor has a multi-metal in-plane ordered structure; more preferably, the MAX phase precursor is an in-plane ordered high-entropy MAX phase material.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The reaction temperature of the topo conversion reaction is between 600 and 1100° C., and the reaction time is between 10 min and 10 h. And / or, the stripping treatment adopts ultrasonic liquid phase stripping method.

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

7. The transition metal sulfide quantum sheet according to claim 6, characterized in that: The M is selected from Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W, Sc, and Y elements; and / or, the difference in average atomic radius of the M positions is greater than 8%, preferably greater than 11%; And / or, the M position contains five or more transition metal elements; And / or, the transition metal sulfide quantum sheet is a single-layer structure; And / or, the lateral size of the transition metal sulfide quantum sheet is 2-10 nm; And / or, the transition metal sulfide quantum sheet has a thickness of 0.5-1.5 nm.

8. A transition metal sulfide quantum sheet obtained by the preparation method according to any one of claims 1 to 5, or use of the transition metal sulfide quantum sheet according to claim 6 or 7 in the field of catalysis and batteries.

9. A catalytic device, characterized in that: Contains a transition metal sulfide quantum sheet obtained by the preparation method according to any one of claims 1 to 5, or a transition metal sulfide quantum sheet according to claim 6 or 7.

10. A battery, characterized in that: The transition metal sulfide quantum sheet is obtained by the preparation method according to any one of claims 1 to 5, or the transition metal sulfide quantum sheet according to claim 6 or 7.

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