A mxene material containing carbon or phosphorus functional groups and uses

Abstract

The application discloses a MXene material containing carbon or phosphorus functional groups and a use thereof, and utilizes a gas (halogenated hydrogen gas or halogen element gas) with etching effect to react with a MAX material, etches A components in the MAX phase material, obtains MX (MXene) containing halogen functional groups, and then performs a functional group substitution reaction with an alkane or phosphorus, so that the MXene material with carbon or phosphorus end-capping is obtained.

Description

[0001] This application is a divisional application, the parent application being the invention patent application filed on December 14, 2020, with application number 202011466046.4 and title "Method and System for Preparing Two-Dimensional Materials by Vapor Phase Method". Technical Field

[0002] This invention belongs to the field of new materials, and in particular relates to an MXene material containing carbon or phosphorus functional groups and its uses. Background Technology

[0003] Two-dimensional transition metal carbides, nitrides, or carbonitrides, also known as MXenes due to their two-dimensional structure similar to graphene, have a single MXene layer thickness of about 1 nm, while their lateral dimensions can reach tens of micrometers or more. This unique structure and surface properties give MXenes unique electrical properties, optical properties, thermal stability, and other excellent characteristics, and they have potential applications in energy storage, catalysis, adsorption, and other fields.

[0004] Currently, the most classic and commonly used method for preparing MXene two-dimensional materials is the hydrofluoric acid (HF) etching method. Using MAX phase materials as raw materials, the A component is etched away by HF to obtain two-dimensional MXene materials. Among them, MAX phase materials are layered ceramic materials, M refers to transition metal elements, including Sc, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, etc.; A mainly refers to elements of Group III and Group IV, such as Al, Ga, In, Tl, Si, Ge, Sn, Pb, etc.; X represents C or N; n=1, 2, or 3. MAX phase materials are a large class of materials, and the types of materials included can be found in the literature (Maxim S, Varun N, Sankalp K, et al. Trends in Chemistry, 2019, 1(2):210-223.).

[0005] Taking the Ti3AlC2MAX phase as an example, Ti3C2 was prepared by immersing Ti3AlC2 in a 50% hydrofluoric acid solution for 2 hours to etch the Al atoms in Ti3AlC2 (Naguib M, Kurtoglu M, Presser V, et al. Advanced Materials, 2011, 23(37): 4248-4253.). Since HF is highly corrosive and toxic, researchers used hydrochloric acid solution + fluoride salt as an etchant to prepare MXene (Ghidiu M, Lukatskaya MR, Zhao MQ, et al. Nature, 2014, 516(7529): 78.). Similar methods were used to prepare MXene two-dimensional materials such as Ti2C, Ta4C3, Ti3CN, and V4C3.

[0006] However, this method for preparing MXene requires the direct or indirect use of highly corrosive and toxic HF acid, making it difficult to guarantee safety during the preparation process. Furthermore, because it is a liquid-phase reaction, the generated MXene is dispersed in a high-concentration acid solution. Obtaining the MXene powder requires repeated washing, ultrasonication, centrifugation, and drying. These complex processes make large-scale production of MXene difficult and result in extremely high costs, severely limiting its application prospects. Currently, the preparation and application of MXene remain in the laboratory research stage. Summary of the Invention

[0007] The purpose of this invention is to provide a novel MXene material with carbon or phosphorus end caps, that is, an MXene material containing carbon or phosphorus functional groups and its preparation method.

[0008] The first aspect of this application provides a method for preparing an MXene material, wherein the MXene material contains carbon or phosphorus functional groups; the method for preparing the MXene material includes: heating a MAX phase material with hydrogen halide gas or halogen elemental gas to a first reaction temperature, and then reacting it with hydrocarbons or phosphorus at a second reaction temperature.

[0009] In some embodiments, in the above MAX phase material, M represents a transition metal element; A represents a main group element and / or a transition metal element; and X represents one or more of carbon, nitrogen, and boron.

[0010] In some embodiments, the above-mentioned hydrocarbons are CH4 or C2H4.

[0011] In some embodiments, the hydrogen halide gas is hydrogen chloride gas, hydrogen bromide gas, or hydrogen iodide gas.

[0012] In some embodiments, the aforementioned halogen gas is bromine or iodine.

[0013] In some embodiments, the hydrogen halide gas is hydrogen chloride gas; the halogen element gas is iodine gas.

[0014] In some embodiments, the first reaction temperature is between 500°C and 1200°C.

[0015] In some embodiments, the second reaction temperature is between 600°C and 1500°C.

[0016] In some embodiments, the first reaction temperature is between 600°C and 800°C.

[0017] A second aspect of the present invention provides an MXene material obtained by the above-described preparation method.

[0018] In some embodiments, MXene materials are characterized by scanning electron microscopy to have an accordion-like morphology or a two-dimensional sheet-like morphology.

[0019] In some embodiments, the chemical formula of MXene material is represented as M n+1 X n T x In this context, M represents one or more transition metal elements, X represents one or more carbon, nitrogen, and boron elements, and T represents carbon or phosphorus.

[0020] In some embodiments, the transition metal element is selected from one or more of scandium, yttrium, titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, and tungsten; and / or, X is carbon and / or nitrogen.

[0021] In some embodiments, the transition metal element is selected from one or more of titanium, molybdenum, yttrium, niobium, and tantalum.

[0022] A third aspect of the present invention provides an application of the above-mentioned MXene material in supercapacitors, metal batteries, catalysis, electromagnetic shielding, microwave absorbing coatings, or as a superconducting material.

[0023] The beneficial technical effects of this invention are as follows: the gas with etching effect (hydrogen halide gas or halogen element gas) reacts with the MAX material to etch the A component in the MAX phase material to obtain MX (MXene) containing halogen functional groups. Then, it undergoes a functional group substitution reaction with alkanes or phosphorus to obtain a novel MXene material with unique carbon or phosphorus end caps.

[0024] The etching and substitution reactions of this invention are carried out in a gas phase environment, which avoids the repeated washing, sonication, centrifugation, and drying steps required in the liquid phase method for preparing MXene. This greatly simplifies the preparation process, reduces the preparation cost, and enables the industrial-scale preparation of MXene materials, laying the foundation for the application of MXene in different fields.

[0025] The preparation method of the present invention is also applicable to MAX raw materials where X is CN or N element, and MXenes where X is CN or N element are obtained by etching. This type of MXene is difficult to obtain by conventional liquid phase method. Attached Figure Description

[0026] Figures 1-5 This is a schematic diagram of the system for preparing two-dimensional materials by vapor phase method in Embodiment 2 of the present invention;

[0027] Figure 6 The Ti3C2T prepared by reacting (a) bulk Ti3AlC2 and (b) HCl gas with Ti3AlC2 in Example 3 of this invention x SEM photos;

[0028] Figure 7 The Ti3C2T prepared by reacting Ti3AlC2 with HCl gas in Example 3 of this invention x And the XRD pattern of Ti3AlC2;

[0029] Figure 8 The Ti3C2T in Embodiment 3 of the present invention x (a) STEM image, (b) Ti, (c) C and (d) Cl elemental distribution map;

[0030] Figure 9 The Ti3CNT prepared by reacting HCl gas with Ti3AlCN in Example 4 of this invention. x SEM photos;

[0031] Figure 10 The Ti3CNT prepared by reacting Ti3AlCN with HCl gas in Example 4 of this invention. x And the XRD pattern of Ti3AlCN;

[0032] Figure 11 The Ti3CNT in Embodiment 4 of the present invention x (a) STEM image, (b) Ti, (c) C, (d) N and (e) Cl elemental distribution diagrams;

[0033] Figure 12 In embodiment 5 of the present invention, (a) the block (Mo) 2 / 3 Y 1 / 3 )2AlC and (b)HCl gas with (Mo2 / 3 Y 1 / 3 (Mo) prepared by reaction of 2AlC 2 / 3 Y 1 / 3 )2CT x SEM photos;

[0034] Figure 13 In Embodiment 5 of the present invention (Mo) 2 / 3 Y 1 / 3 (Mo) prepared by reacting AlC with HCl gas 2 / 3 Y 1 / 3 )2CT x and (Mo 2 / 3 Y 1 / 3 XRD pattern of 2AlC;

[0035] Figure 14 In Embodiment 5 of the present invention (Mo) 2 / 3 Y 1 / 3 )2CT x (a) STEM image, (b) Mo, (c) Y, (d) C and (e) Cl elemental distribution diagrams;

[0036] Figure 15 The Ti4N3T prepared by reacting (a) bulk Ti4AlN3 and (b) Ti4AlN3 with HCl gas in Example 6 of this invention. x (c) SEM images of Ti4N3-O2 prepared by reacting Ti4AlN3 with HCl gas and O2;

[0037] Figure 16 The Ti4N3T in Example 6 of this invention is prepared by reacting Ti4AlN3 with HCl gas. x XRD pattern of Ti4N3-O2 prepared by reacting Ti4AlN3 with HCl gas and O2;

[0038] Figure 17 The preparation of Ti4N3T by reacting Ti4AlN3 with HCl gas in Example 6 of this invention x High-resolution Cl 2p XPS spectra;

[0039] Figure 18 The Ti4N3T in Embodiment 6 of the present invention x (a) STEM image of (T=O), (b) elemental distribution of Ti, (c) N and (d) O;

[0040] Figure 19 These are SEM images of (a) TiNbAlC, (b) TiNbC-Cl2 and (c) TiNbC-S2 in Example 7 of the present invention;

[0041] Figure 20 The XRD patterns of TiNbAlC, TiNbC-Cl2 and TiNbC-S2 in Example 7 of this invention;

[0042] Figure 21 The images show (a) STEM image of TiNbC-Cl2 in Example 7 of this invention, (b) elemental distribution diagrams of Ti, (c) Nb, (d) C and (e) Cl.

[0043] Figure 22 The images shown are (a) STEM image and (b) S element distribution diagram of TiNbC-S2 in Example 7 of this invention.

[0044] Figure 23 In Embodiment 8 of the present invention, (a) Ta2AlC and (b) Ta2C-T x SEM photos;

[0045] Figure 24 In Embodiment 9 of the present invention, (a) Nb2AlC and (b) Nb2C-T x SEM photos;

[0046] Figure 25 These are SEM images of (a) Nb2AlC and (b) Nb2C-Cl2 in Example 10 of the present invention;

[0047] Figure 26 SEM images of (a) Mo2C-S in Example 11 of the present invention and (b) MoS2 in Example 12 of the present invention;

[0048] Figure 27 The image shows the XRD pattern of MoS2 in Embodiment 12 of the present invention.

[0049] Explanation of symbols in the attached diagram:

[0050] 100 Etching gas; 10 Reaction apparatus; 11 Raw material layer; 20 Absorption device; 30 First gas device; 31 Gas generating device; 311 Acid container; 312 Reactor; 313 Control device; 40 Carrier gas device; 50 Tail gas recovery device; 60 Second gas device. Detailed Implementation

[0051] The technical solution of the present invention is illustrated below through specific embodiments. It should be understood that one or more steps mentioned in the present invention do not preclude the existence of other methods and steps before or after the combined steps, or that other methods and steps may be inserted between these explicitly mentioned steps. It should also be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the invention. Unless otherwise stated, the numbering of each method step is only for the purpose of identifying each method step, and not for limiting the order of each method or limiting the scope of the invention. Changes or adjustments to their relative relationships, without substantial changes to the technical content, can also be considered as within the scope of the invention. The raw materials and instruments used in the embodiments are not specifically limited in their source; they can be purchased from the market or prepared according to conventional methods well known to those skilled in the art.

[0052] Example 1

[0053] This embodiment provides a method for preparing two-dimensional materials using a vapor phase method, including:

[0054] Vapor phase etching step: The gas with etching effect reacts with the MAX phase material at a first predetermined temperature to etch component A in the MAX phase material, thereby obtaining a two-dimensional material containing MX (MXene).

[0055] It should be noted that the raw material MAX phase of the present invention has the general chemical formula M. n+1 AX n M is selected from one or more transition metal elements, A is selected from at least one element selected from group VIIB, VIII, IB, IIB, IIIA, IVA, VA and VIA, and X is at least one element selected from carbon, nitrogen or boron.

[0056] In some embodiments, the M transition metal element is selected from one or more elements of Group IIIB, IVB, VB, and VIB. Typically, the M element includes, but is not limited to, one or more of the following: scandium, yttrium, titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, and lanthanides (lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, or lutetium). The A element includes, but is not limited to, one or more of the following: aluminum, silicon, phosphorus, sulfur, manganese, iron, cobalt, nickel, copper, zinc, gallium, germanium, arsenic, selenium, ruthenium, rhodium, palladium, cadmium, indium, tin, antimony, osmium, iridium, platinum, gold, mercury, thallium, lead, bismuth, polonium, or astatine. MAX phase materials are a broad class of materials. MAX phase materials discovered before or after the date of this application, and MXene materials obtained using the methods of this invention, are all within the scope of protection of the claims of this invention.

[0057] The etching gases in this invention include one or more of the following: halogens, halide hydrides, or nitrogen hydrides. These elemental or hydride gases can react with component A in the MAX phase material under certain reaction conditions to generate gaseous products, which are then removed from the reaction system, thereby achieving partial or complete etching of component A to obtain two-dimensional materials containing MX. These MX two-dimensional materials are free of solid impurities and possess excellent high purity. Preferably, the halogens include Br2 or I2; the halide hydrides include HF, HCl, HBr, or HI; and the nitrogen hydrides include NH3 or H3P.

[0058] In some embodiments, during the vapor phase etching step, the first predetermined temperature is between 500°C and 1200°C. The reaction temperature is related to the bonding energy between element A and elements M and X in the MAX phase material. The higher the bonding energy, the higher the required reaction temperature. Preferably, the reaction temperature is between 600°C and 800°C.

[0059] In some embodiments, the gas in the vapor phase etching step also includes a carrier gas, which is an inert gas that does not participate in the vapor phase etching reaction, including one or more of helium, neon, argon, krypton, xenon, or nitrogen. Adding a carrier gas can dilute the content of the etching-active gas in the gas mixture, thereby controlling the rate of the vapor phase etching reaction.

[0060] In some embodiments, the etching gas is generated by the thermal decomposition or sublimation of a solid, or by the vaporization of a liquid. Preferably, the solid includes a halide ammonium compound; for example, halide hydrides can be generated by the thermal decomposition of solid halide ammonium compounds (such as NH4F, NH4Cl, NH4Br, NH4I, etc.). When the halide ammonium compounds thermally decompose, ammonia and halide hydride gases are produced, without introducing new solid impurities into the gas-phase reaction. Optionally, it may also include: solid elemental iodine, which sublimates into the gas phase upon heating; or liquid halide acid solutions that vaporize to generate elemental iodine or halide hydride gases.

[0061] In some embodiments, the etching gas is generated by a chemical reaction between a compound and an acid solution. For example, halide gas is generated by a chemical reaction between a halide metal salt and an acid solution. Optionally, the chemical reaction includes, but is not limited to: NaCl + H₂SO₄ = NaHSO₄ + HCl↑, NaBr + H₃PO₄ = NaH₂PO₄ + HBr↑, CaF₂ + H₂SO₄ = CaSO₄ + 2HF, NaI + H₃PO₄ = NaH₂PO₄ + HI↑, etc.

[0062] In some embodiments, the present invention further includes a conditioning step: reacting a two-dimensional material containing MX with a functional gas at a second predetermined temperature, wherein the functional gas includes an element or hydride of a Group 4, Group 5, or Group 6 main element, to obtain a two-dimensional material containing an element of a Group 4, Group 5, or Group 6 main element, thereby achieving modification of the two-dimensional material. Preferably, the Group 4 main element includes C, Si, or Ge; the Group 4 main hydride includes CH4, C2H8, C2H4, H4Ge, or H4Si; the Group 5 main element includes P; the Group 5 main hydride includes NH3 or PH3; the Group 6 main element includes O2, S, Se, or Te; and the Group 6 main hydride includes H2S, H2Se, or H2Te.

[0063] In some embodiments, the gas in the vapor phase etching step also includes a functional gas, which includes elements or hydrides of Group 4, Group 5, or Group 6 elements. This allows the MAX phase material to undergo a vapor phase etching reaction with the etching gas. Simultaneously, the MX-containing two-dimensional material undergoes a functional group adjustment reaction and / or a conversion reaction with the functional gas. The vapor phase etching step yields a two-dimensional material containing elements of Group 4, Group 5, or Group 6. That is, the vapor phase etching step simultaneously achieves the purpose of the adjustment step. Preferably, the reaction temperature is set between 500°C and 700°C, primarily for functional group adjustment reactions to obtain MX two-dimensional materials containing functional groups of elements from Group 4, Group 5, or Group 6. Preferably, the reaction temperature is set between 700°C and 1200°C, primarily for conversion reactions to obtain novel two-dimensional materials containing elements from Group 4, Group 5, or Group 6.

[0064] It should be noted that two types of reactions can occur in the adjustment step. One type involves elements from Group 4, Group 5, or Group 6 partially or completely replacing the functional groups of the MX-containing two-dimensional material, resulting in an MX two-dimensional material containing functional groups from Group 4, Group 5, or Group 6 elements. Preferably, this type of reaction mainly occurs at relatively low reaction temperatures (between 100°C and 600°C). The other type involves elements from Group 4, Group 5, or Group 6 partially or completely replacing the X component in the MX-containing two-dimensional material, resulting in a novel two-dimensional material containing elements from Group 4, Group 5, or Group 6 elements. Preferably, this type of reaction mainly occurs at relatively high reaction temperatures (between 600°C and 1500°C).

[0065] It should also be noted that the two-dimensional material containing MX obtained by the vapor phase etching step of the present invention has functional groups on its surface. These functional groups are introduced by a gas with etching effect (such as -F, -Cl, -Br, -I, -P, -N, etc.). After the vapor phase etching step, the reaction temperature can be directly adjusted to a second predetermined temperature and a functional gas can be introduced to carry out the functional group adjustment reaction. The functional groups on the two-dimensional material containing MX can directly react with the functional gas to achieve the technical effect of specific functional group adjustment. In the prior art, the surface of MX materials prepared by liquid phase method has -F, -OH, and -O functional groups, which are easily oxidized or hydrolyzed into transition metal oxides, making it difficult to achieve the purpose of functional group adjustment of MX materials.

[0066] Preferably, the gas in the vapor phase etching step and the conditioning step of the present invention includes a carrier gas, wherein the volume content of the carrier gas is between 20% and 80%. The vapor phase etching step of the present invention can control the etching rate of the MAX phase material through the reaction time. In the conditioning step, the degree of substitution of functional groups or the degree of substitution of element X can be controlled through the reaction time. Generally, the reaction time of the vapor phase etching step and the conditioning step is between 5 min and 6 h. Preferably, in the vapor phase etching step, a reaction time between 20 min and 40 min can achieve complete etching, and in the conditioning step, a reaction time between 20 min and 60 min can achieve complete substitution or replacement. The present invention uses conventional techniques with a heating rate between 2°C / min and 20°C / min, and the experimental reaction is carried out at atmospheric pressure.

[0067] Example 2

[0068] This embodiment provides a system for preparing two-dimensional materials using a vapor phase method, such as... Figure 1 As shown, the device includes a reaction apparatus 10, an exhaust gas absorption apparatus 20, and a first gas apparatus 30. The reaction apparatus 10 is used to react an etching gas 100 with the MAX phase material at a predetermined temperature, so that the etching gas 100 etches the A component therein to obtain a two-dimensional material containing MX. The exhaust gas absorption apparatus 20 is used to absorb excess gas that has not participated in the reaction in the reaction apparatus. The gas apparatus 30 is used to supply the etching gas 100 into the reaction apparatus 10.

[0069] The reaction apparatus 10 contains a sealable reaction chamber, within which at least one raw material layer 11 is disposed for holding the MAX phase material. An etching gas 100 is introduced into the reaction space within the reaction apparatus 10 to allow the etching gas in the gas phase to react with the MAX phase material at a predetermined temperature. Figure 1In the example, the raw material layer has four layers, but the present invention is not limited to this. Setting multiple layers of raw material layer 11 in the reaction space can accommodate more MAX phase material, enabling a single vapor-phase etching reaction to produce more MX material, thus achieving mass production of MX material and significantly reducing the preparation cost of MX material. Excess gas from the vapor-phase reaction is absorbed by the tail gas absorption device 20. In some embodiments, the tail gas absorption device 20 contains an alkaline liquid, such as NaOH or KOH solution, which absorbs the excess gas from the vapor-phase reaction through a neutralization reaction.

[0070] The gas device 30 can be a gas storage device, such as a high-pressure gas tank; or it can be a gas generating device 31, that is, a device that can generate gas with an etching effect.

[0071] Optionally, the gas generating device 31 is a device that generates gas using a solid thermal decomposition reaction. Preferably, the solid is a halide ammonium compound (such as NH4F, NH4Cl, NH4Br, NH4I, etc.). When the halide ammonium compound thermally decomposes, it produces ammonia and halide hydride gases, which do not introduce new solid impurities into the gas phase etching reaction. Excess ammonia and halide hydrides in the reaction are absorbed by the tail gas absorption device 20. Optionally, it also includes the sublimation of solid iodine into the gas phase by heating, which can avoid introducing new solid impurities in the gas phase etching step.

[0072] In another embodiment, such as Figure 2 As shown, the gas generating device 31 is installed inside the reaction chamber of the reaction device 10 so that the solid thermal decomposition reaction is carried out by the heating energy of the reaction device 10 to generate the etching gas. The etching gas does not need to go through the pipe and can directly enter the reaction chamber of the reaction device 10.

[0073] In another embodiment, the gas generating device 31 generates gas through a chemical reaction between a compound and an acid solution. For example, a halide metal salt reacts with an acid solution to generate halide hydride gas. Optionally, the chemical reaction includes, but is not limited to: NaCl + H₂SO₄ = NaHSO₄ + HCl↑, NaBr + H₃PO₄ = NaH₂PO₄ + HBr↑, CaF₂ + H₂SO₄ = CaSO₄ + 2HF, NaI + H₃PO₄ = NaH₂PO₄ + HI↑, etc. Figure 3 As shown, the gas generating device 31 includes an acid container 311, a reactor 312, and a control device 313. The metal salt of the halogen element is placed in the reactor 312. The acid solution in the acid container is dripped into the reactor 312 by the control device 313. The halogen metal salt reacts with the acid solution to generate hydride gas.

[0074] In the gas-phase method for preparing two-dimensional materials of the present invention, the advantage of the gas device 30 being a gas generator 31 is that it can be prepared on-site when needed, avoiding safety issues such as leakage caused by storage and transportation of halohydride gases during the production process.

[0075] In another embodiment, the system for preparing two-dimensional materials by gas phase method of the present invention further includes a carrier gas device 40, such as... Figure 4 As shown, the carrier gas is mixed with the etching gas through a pipeline to form a mixed gas, which is then introduced into the reaction device 10 to participate in the reaction. The carrier gas refers to a gas that does not participate in the gas phase etching reaction, including but not limited to helium, neon, argon, krypton, and xenon. By mixing the etching gas with the carrier gas and adjusting the content of the etching gas in the mixed gas, the rate of the gas phase etching reaction can be controlled.

[0076] In another embodiment, the system for preparing two-dimensional materials by gas phase method of the present invention further includes a tail gas recovery device 50, such as... Figure 4 As shown, the gas is connected to the exhaust port of the reaction device 10 via a pipeline to recover and store excess exhaust gas from the vapor phase etching reaction, or to transport excess exhaust gas from the vapor phase etching reaction back to the gas inlet of the reaction device 10 via a pipeline, so that the gas 100 with etching effect can be recycled, thereby improving the gas utilization rate, reducing the processing capacity of the exhaust gas treatment device 20, and thus reducing the preparation cost of MX material.

[0077] In another embodiment, the system for preparing two-dimensional materials by gas phase method of the present invention further includes a second gas device 60, such as... Figure 4 and Figure 5 As shown, a second gas is introduced into the reaction apparatus 10, wherein the second gas reacts with the two-dimensional material containing MX obtained in the vapor phase etching step, thereby adjusting the type of functional groups on the surface of the MX material or replacing all or part of the X element in MX, thereby changing the properties of the material.

[0078] The method and system of this invention can directly obtain powdered MX material (MXene) free of any solid impurities, avoiding the repeated washing, ultrasonication, centrifugation, and drying steps required in the liquid-phase method for MXene preparation. This greatly simplifies the preparation process and reduces the preparation cost. During the entire vapor-phase etching reaction, excess gas can be completely absorbed by the tail gas absorption device 20, thus the entire reaction device does not generate environmental pollution and meets the environmental protection requirements of industrial production.

[0079] Example 3

[0080] To better illustrate the technical features of this invention, the following example uses Ti3AlC2 as the MAX phase material and commercially available liquefied HCl as the halide gas to describe the gas-phase method for preparing two-dimensional materials according to this invention. The reaction system used is as described in Example 2. Figure 1 As shown, the reaction apparatus 10 is a tube furnace, and the first gas device 30 is a high-pressure gas cylinder containing HCl gas, including the following steps:

[0081] 1) Place powdered Ti3AlC2 inside the reaction apparatus 10;

[0082] 2) Introduce HCl gas into the reaction device 10 for a period of time until the reaction chamber inside the reaction device 10 is filled with HCl gas, and then seal the reaction chamber.

[0083] 3) The internal temperature of the reaction apparatus 10 is raised to 700°C and held for 10 minutes to induce a vapor phase etching reaction and obtain the target product.

[0084] After the reaction apparatus cooled naturally to room temperature, the target product was removed. Scanning electron microscopy (SEM) was performed on the MAX phase material Ti3AlC2 and the target product, respectively. The results are as follows: Figure 6 As shown in figures a and b, a comparison reveals that Ti3AlC exhibits a three-dimensional blocky structure, while the target product displays a distinct accordion-like layered structure. X-ray diffraction (XRD) analysis was performed on the MAX phase material Ti3AlC2 and the target product, and the results are as follows... Figure 7 As shown, by comparison, the (002) peak in the raw material Ti3AlC2 appears at 9.5°, while the (002) peak in the target product after reaction with hydrogen chloride shifts to a lower angle of 7.9°. This indicates that HCl gas etches the Al element in Ti3AlC2 during the gas-phase etching reaction, generating a layered MX material (MXene), leading to an increase in interlayer spacing. This is consistent with the effect of Ti3C2T x The results are consistent with the scanning electron microscope images. Target product Ti3C2T x The scanning transmission electron microscope (STEM) image of the transmission electron microscope (TEM), as shown below. Figure 8 As shown in figure a, it contains a large number of two-dimensional ultrathin nanosheets, indicating that the accordion is made of Ti3C2T. x Two-dimensional nanosheets with a uniform distribution of Ti and C elements can be obtained by simple exfoliation. Figure 8 b and c), and the nanosheet also contains Cl element ( Figure 8 d) indicates that the target product obtained is an MX material (Ti3C2-Cl2) containing Cl functional groups.

[0085] It should be noted that in this embodiment, after HCl gas is introduced into the reaction device, the gas phase etching reaction is reversed in the sealed reaction chamber. However, in the large-scale preparation process of this invention, halide gas can be continuously introduced into the reaction chamber, and the excess gas can be absorbed by the tail gas absorption device or recycled by the tail gas circulation device.

[0086] Example 4

[0087] In this embodiment, Ti3AlCN is used as the MAX phase material and HCl gas is used as the etching gas. The preparation method is the same as in Example 3. The difference is that the gas phase etching reaction of HCl gas and Ti3AlCN is set to 800℃ and held for 30 min to obtain the target product.

[0088] After the reaction apparatus has cooled naturally to room temperature, the target product is removed. SEM analysis is performed on the target product; SEM images are shown below. Figure 9 The presence of numerous expanded accordion structures in the Ti3AlCN powder, which differs from the bulk layered morphology of the MAX phase powder, indicates that the Al between the Ti3AlCN layers was etched by the HCl reaction to obtain Ti3CNT. x (MXene). XRD analysis was performed on the MAX phase Ti3AlCN and the target product, and the results are as follows: Figure 10 As shown, by comparison, the (002) peak in the raw material Ti3AlCN appears at 9.5°, while the (002) peak in the target product after reaction with hydrogen chloride shifts to a lower angle of 8°. Furthermore, a new (004) peak appears in the reaction product, representing the accordion-like layered structure. This indicates that HCl gas etches the Al element in Ti3AlCN during the gas-phase reaction, generating a layered MX material (MXene), leading to an increase in interlayer spacing. This is consistent with Ti3CNT. x The expanded accordion structure is consistent with that shown in the scanning electron microscope images. Target product Ti3CNT x The STEM images show a large number of two-dimensional ultrathin nanosheets, such as Figure 11 As shown in figure a, it indicates the Ti3CNT of the accordion. x Two-dimensional nanosheets with a uniform distribution of Ti, C, and N elements can be obtained through simple exfoliation. Figure 11 b, c, and d), and the nanosheet also contains the element Cl ( Figure 11 e) indicates that the target product obtained is an MX material (Ti3CN-Cl2) containing Cl functional groups.

[0089] Example 5

[0090] In this embodiment, the MAX phase material is (Mo) 2 / 3 Y 1 / 3The preparation method of the present invention is illustrated using 2AlC and HCl gas as an example, wherein the reaction system selected is as shown in Example 1. Figure 2 As shown, a gas generating device 31 is disposed inside the reaction apparatus 10. The gas generating device 31 has a channel for gas to enter the reaction chamber of the reaction apparatus, including the following steps:

[0091] 1) Place powdered (Mo) inside the reaction apparatus. 2 / 3 Y 1 / 3 )2AlC, and solid NH4Cl placed inside the gas generating device 31, and the reaction chamber sealed;

[0092] 2) Heat the inside of the reaction apparatus to 350°C and hold for 30 minutes to decompose NH4Cl into NH3 and HCl gases. Then heat to 650°C and hold for 30 minutes to allow a gas-phase reaction to occur and generate the target product.

[0093] After the reaction apparatus has cooled naturally to room temperature, the target product is removed. (Mo) 2 / 3 Y 1 / 3 The target product after the reaction of AlC with hydrogen chloride was analyzed by SEM, and the results are as follows: Figure 12 As shown, the target product after the reaction exhibits a distinct accordion-like layered structure, which is significantly different from its raw material (Mo). 2 / 3 Y 1 / 3 Bulk morphology of 2AlC. (Mo) 2 / 3 Y 1 / 3 XRD analysis was performed on 2AlC and the target product, and the results are as follows: Figure 13 As shown, through comparison, the raw material (Mo) 2 / 3 Y 1 / 3 The (002) peak in 2AlC appears at 12.9°, while the (002) peak in the target product after reaction with hydrogen chloride shifts to a lower angle of 7.8°. This indicates that HCl gas etched (Mo) during the gas-phase reaction. 2 / 3 Y 1 / 3 The Al element in 2AlC generates a layered MX material (MXene), leading to an increased interlayer spacing, consistent with the scanning electron microscope (SEM) results. The target product (Mo) 2 / 3 Y 1 / 3 )2CT x The STEM images show a large number of two-dimensional ultrathin nanosheets, such as Figure 14 As shown in a, it indicates the accordion's (Mo) 2 / 3 Y 1 / 3 )2CT x A large number of two-dimensional nanosheets with uniform distribution of Mo, Y, and C elements can be obtained by simple exfoliation. Figure 14b, c, and d), and the nanosheet also contains the element Cl ( Figure 14 e), indicating that the target product obtained is an MX material containing Cl functional groups ((Mo) 2 / 3 Y 1 / 3 )2C-Cl2).

[0094] Example 6

[0095] This embodiment uses Ti4AlN3 as the MAX phase material and HCl gas as the halide gas to prepare two-dimensional materials. The reaction system used is as described in Example 1. Figure 5 As shown, reaction device 10 is a tube furnace, gas device 30 is a gas generating device 31, which uses the chemical reaction of halide metal salts with acid solution to generate halide gas NaCl + H2SO4 = NaHSO4 + HCl↑. Gas device 60 is a high-pressure gas cylinder containing O2 gas. The difference is that the target product Ti4N3T obtained by the reaction of Ti4AlN3 with HCl is Ti4N3T. x Furthermore, the two-dimensional material Ti4N3T can be treated using a second gas, O2. x Modulation of surface functional groups includes the following steps:

[0096] 1) Place powdered Ti4AlN3 inside the reaction apparatus;

[0097] 2) Add NaCl and H2SO4 into the gas generating device 31, control the H2SO4 to maintain a certain dropping rate so that it continuously reacts with NaCl to generate HCl gas, and continuously pass HCl into the reaction chamber;

[0098] 3) The internal temperature of the reaction apparatus is raised to 650℃ and held for 30 minutes to induce a gas-phase reaction, yielding the target product Ti4N3T. x Or continue to take the next step;

[0099] 4) After the hydrogen chloride reaction is complete, turn off the gas generator and stop the HCl flow. Then, continuously introduce O2 from the second gas device into the reaction chamber.

[0100] 5) Adjust the internal temperature of the reaction apparatus to 500℃ and maintain this temperature for 10 minutes to allow a gas-phase reaction to occur, yielding Ti4N3T with oxygen-containing functional groups on its surface. x (T=O);

[0101] After the reaction apparatus cooled naturally to room temperature, the target products were removed. SEM analysis was performed on the two target products resulting from the reaction of Ti4AlN3 with hydrogen chloride; the results are as follows. Figure 15As shown, the target product after the reaction exhibits a distinct accordion-like layered structure, characterized by a clearly stacked, expanded structure, which is significantly different from the bulk morphology of its raw material, Ti4AlN3. XRD analysis of Ti4AlN3 and the two target products yielded the following results: Figure 16 As shown, by comparison, the (002) peak in the raw material Ti4AlN3 appears at 7.5°, while the (002) peak in the target product after reaction with HCl and the target product after subsequent O2 treatment shifts to a lower angle of 6.1°. This indicates that HCl gas etches the Al element in Ti4AlN3 during the gas-phase reaction, generating a layered MX material (MXene), leading to an increase in interlayer spacing. Furthermore, the subsequent O2 treatment did not change the crystal structure of Ti4N3, which is consistent with the results of scanning electron microscopy. X-ray photoelectron spectroscopy (XPS) was used to analyze the Ti4N3 obtained from the reaction of Ti4AlN3 with HCl. x The surface functional groups were characterized, such as Figure 17 As shown, in Ti4N3T x A significant Cl elemental signal was detected on the material surface, corresponding to Ti4N3T x The Ti-Cl bonds on the surface and the presence of Cl in the nanosheet indicate that the target product is an MX material (Ti4N3-Cl2) containing Cl functional groups. Target product Ti4N3T x The STEM image of (T=O) shows a large number of two-dimensional ultrathin nanosheets, such as Figure 18 As shown in figure a, it indicates that the accordion's Ti4N3T x A large number of two-dimensional nanosheets with uniform distribution of Ti, N, and O elements can be obtained by simple exfoliation. Figure 18 (b, c, and d) indicates that the target product obtained is an MX material (Ti4N3-O2) containing O functional groups.

[0102] Example 7

[0103] In this embodiment, TiNbAlC is used as the MAX phase material and HCl is used as the halide gas. Hydrogen sulfide (H2S) is used as the second gas to adjust the surface functional groups. The preparation method is the same as in Example 6, except that the target product obtained by reacting TiNbAlC with HCl is TiNbC-Cl2. The reaction occurs at 700°C and is held for 30 min. Subsequently, after H2S treatment, the target product TiNbC-S2 with S surface functional group is obtained. The reaction occurs at 500°C and is held for 10 min.

[0104] After the reaction apparatus cooled naturally to room temperature, the target product was removed. SEM analysis was performed on TiNbAlC and the two target products (TiNbC-Cl2 and TiNbC-S2) after the reaction with hydrogen chloride. The results are as follows: Figure 19 As shown in a, b, and c, the target product after the reaction exhibits a distinct accordion-like layered structure. This accordion structure has a clearly stacked, expanded structure, which is significantly different from the bulk morphology of its raw material TiNbAlC. Figure 19 a). XRD analysis was performed on TiNbAlC and the two target products, and the results are as follows: Figure 20 As shown, by comparison, the (002) peak in the raw material TiNbAlC appears at 12.7°, while the (002) peak in the target product after reaction with hydrogen chloride and the subsequent target product after H2S treatment shifts to a lower angle of 9.8°. This indicates that HCl gas etches the Al element in TiNbAlC during the gas-phase reaction, generating a layered MX material (MXene), leading to an increase in interlayer spacing. The subsequent H2S treatment did not change the crystal structure of TiNbC and did not produce sulfide phase separation, which is consistent with the results of the scanning electron microscope (SEM) images. The STEM image of the target product TiNbC-Cl2 shows ultrathin two-dimensional nanosheets, such as... Figure 21 As shown in Figure a, it indicates that the TiNbC-Cl2 of the accordion can be easily exfoliated to obtain a large number of two-dimensional nanosheets, which have a uniform distribution of Ti, Nb, and C elements. Figure 21 b, c, and d), and the nanosheet also contains the element Cl ( Figure 21 e), indicating that the target product obtained is an MX material (TiNbC-Cl2) containing Cl functional groups. The TiNbC-S2 material surface after H2S gas treatment exhibits a uniform S element distribution, such as... Figure 22 As shown, the functional groups on the surface of the target product can be replaced with S after subsequent processing to obtain MX material (TiNbC-S2) with S functional groups.

[0105] It should be noted that in this embodiment, the reaction of the MX surface functional groups using gas is preferably carried out in the temperature range of 100℃ to 600℃, which is related to the type of MX surface functional groups and the reaction time. Highly active functional groups are more likely to react at low temperatures. Through limited experiments, the optimal temperature and reaction time for different types of MX materials with different functional groups to react can be determined.

[0106] Example 8

[0107] This embodiment uses Ta2AlC as the MAX phase material and HI gas as the halide gas. The preparation method is the same as in Example 3, except that the reaction temperature is set to 900℃ and held for 20 min. The target product Ta2CT is obtained by reacting Ta2AlC with HI. x .

[0108] After the reaction apparatus has cooled naturally to room temperature, the target product is removed. SEM analysis is performed on the target product; SEM images are shown below. Figure 23 b) shows a large number of inflated accordion structures, which is different from the blocky layered morphology of the traditional MAX phase. Figure 23 a) indicates that the Al between the Ta2AlC layers was etched by the hydrogen iodide reaction to obtain Ta2C-I.

[0109] Example 9

[0110] In this embodiment, Nb2AlC is used as the MAX phase material, and PH3 gas is used for etching. The preparation method is the same as in Example 3, except that the reaction temperature is set to 1500℃ and held for 10 min. The target product Nb2CT is obtained by reacting Nb2AlC with PH3 gas. x .

[0111] After the reaction apparatus has cooled naturally to room temperature, the target product is removed. SEM analysis is performed on the target product; SEM images are shown below. Figure 24 b) shows a large number of expanded accordion structures, which is different from the blocky layered morphology of Nb2AlC ( Figure 24 a) indicates that the Al between the Nb2AlC layers was etched by the PH3 reaction to obtain Nb2CT. x .

[0112] Example 10

[0113] In this embodiment, Nb₂AlC is used as the MAX phase material and HCl is used as the halide gas. The preparation method is the same as in Example 3, except that the reaction temperature is set to 500℃ and held for 2 hours. The target product Nb₂CT is obtained by reacting Nb₂AlC with HCl. x .

[0114] After the reaction apparatus has cooled naturally to room temperature, the target product is removed. SEM analysis is performed on the target product; SEM images are shown below. Figure 25 b) shows a large number of inflated accordion structures, which is different from the blocky layered morphology of the MAX phase ( Figure 25 a) indicates that the Al between the Nb2AlC layers was etched by the reaction of hydrogen chloride to obtain Nb2C-Cl2.

[0115] Example 11

[0116] This embodiment uses Mo2GeC as the MAX phase material and elemental HCl gas as the etching gas, and includes the following steps:

[0117] 1) Place powdered Mo2GeC inside the reaction apparatus 10;

[0118] 2) Simultaneously introduce HCl and H2S gases with a volume ratio of 1:1 into the reaction apparatus 10, raise the temperature inside the apparatus 10 to 600℃, and maintain this temperature for 40 min. The HCl gas undergoes a vapor-phase etching reaction with Mo2GeC to generate Mo2C-Cl2. Simultaneously, the generated Mo2C-Cl2 reacts with H2S gas to regulate functional groups, ultimately yielding a two-dimensional material Mo2C-S containing S functional groups in a single step. Its SEM analysis is shown below. Figure 26 As shown in a. Preferably, this embodiment can also react at 500°C to 600°C.

[0119] Example 12

[0120] This embodiment is similar to Embodiment 11, except that the reaction temperature is controlled at 1200℃ and held for 40 min. HCl gas undergoes a vapor-phase etching reaction with Mo2GeC to generate Mo2C-Cl2. Simultaneously, the generated Mo2C-Cl2 reacts with H2S gas in a conversion reaction, where sulfur replaces carbon in Mo2C-Cl2. The final one-step reaction yields a novel two-dimensional material, MoS2. Its SEM and XRD tests are as follows: Figure 26 b and Figure 27 As shown, the SEM images demonstrate that the product maintains a layered accordion structure, and the characteristic peaks of MoS2 such as (002), (100), (103), and (110) in the XRD pattern indicate that MoS2 was prepared. Preferably, this embodiment can also be reacted at 900℃~1200℃.

[0121] As can be seen from Examples 11 and 12, by adjusting the reaction temperature, two-dimensional materials Mo2C-S containing S functional groups, or novel two-dimensional materials MoS2, can be obtained in one step, simplifying the reaction steps.

[0122] Another inventive aspect of this invention lies in the discovery that MX-containing two-dimensional materials primarily undergo functional group regulation reactions at relatively low reaction temperatures (100℃~600℃), reacting with functional gases to regulate the functional groups on the MX surface; while at relatively high temperatures (600℃~1200℃), they mainly undergo conversion reactions with functional gases to obtain novel two-dimensional materials. This characteristic can be seen through the comparison of Examples 11 and 12, and the optimal reaction conditions for different gases to undergo functional group regulation or conversion reactions can be obtained through limited experiments.

[0123] Another inventive aspect of this invention lies in its ability to etch MAX phase materials where X is CN or N using the vapor-phase etching reaction of this invention. In these MAX phase materials, the presence of N at the position of the X component enhances the interaction between the A and X components, making it difficult to etch the A component quickly using liquid-phase etching (requiring more than 5 days). The vapor-phase etching step of this invention utilizes the stronger etching power of gas, enabling complete etching of the A component within a short time (within 30 minutes), thereby preparing novel MX materials where X is CN or N, significantly improving preparation efficiency. This characteristic can be seen in Examples 4 and 6, and the optimal reaction conditions for different types of MAX materials to undergo etching with gas can be obtained through limited experiments.

[0124] The above embodiments are merely some implementation methods provided to illustrate the technical features of the present invention. The present invention is not limited thereto. Several modifications and improvements can be made without departing from the inventive concept of the present invention. The scope of protection of the present invention is defined in the claims.

Claims

1. A method for preparing MXene material, characterized in that, The MXene material contains carbon or phosphorus functional groups; the preparation method of the MXene material includes: heating a MAX phase material with hydrogen halide gas or a halogen element gas to a first reaction temperature to obtain an MXene intermediate with halogen functional groups on its surface; reacting the MXene intermediate with a hydrocarbon or phosphorus at a second reaction temperature, such that the carbon or phosphorus in the hydrocarbon replaces the halogen functional groups to obtain an MXene material containing carbon or phosphorus functional groups; the hydrogen halide gas is hydrogen chloride gas, hydrogen bromide gas, or hydrogen iodide gas; the halogen element gas is bromine gas or iodine gas.

2. The method for preparing MXene material as described in claim 1, characterized in that, In the MAX phase material, M represents a transition metal element; A represents a main group element and / or a transition metal element; and X represents one or more of carbon, nitrogen, and boron. And / or, the hydrocarbon is CH4 or C2H4.

3. The method for preparing MXene material as described in claim 2, characterized in that, The hydrogen halide gas is hydrogen chloride gas; the halogen element gas is iodine gas.

4. The method for preparing the MXene material according to any one of claims 1 to 3, characterized in that, The first reaction temperature is between 500°C and 1200°C; And / or, the second reaction temperature is between 600°C and 1500°C.

5. The method for preparing MXene material as described in claim 4, characterized in that, The first reaction temperature is between 600°C and 800°C.

6. An MXene material obtained by the preparation method according to any one of claims 1 to 5.

7. The MXene material as described in claim 6, characterized in that, The MXene material was characterized by scanning electron microscopy to have an accordion-like morphology or a two-dimensional sheet-like morphology.

8. The MXene material as described in claim 6 or 7, characterized in that, The chemical formula of the MXene material is represented by M. n+ 1X n T x In this context, M represents one or more transition metal elements, X represents one or more carbon, nitrogen, and boron elements, and T represents carbon or phosphorus.

9. The MXene material as described in claim 8, characterized in that, The transition metal element is selected from one or more of scandium, yttrium, titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, and tungsten; And / or, X is carbon and / or nitrogen.

10. The MXene material as described in claim 9, characterized in that, The transition metal element is selected from one or more of titanium, molybdenum, yttrium, niobium, and tantalum.

11. An application of the MXene material as described in any one of claims 6 to 10 in supercapacitors, metal batteries, catalysis, electromagnetic shielding, microwave absorbing coatings, or as a superconducting material.

Images