MXene Prepared by Gas-Phase Etching, and Its Preparation Method and Use

Abstract

The present invention discloses an MXene prepared by gas-phase etching, its method and uses. Among them, this method obtains MXene through an etching reaction between a gaseous etchant and a MAX-phase material. Among them, the etchant is selected from: metal chlorides; or chlorides of boron, carbon, silicon or phosphorus; or one or more of chlorinated hydrocarbons; when the etchant is liquid or solid at room temperature, it further includes heating the etchant to convert the etchant into a gaseous state. The method of the present invention provides a new etchant for preparing MXene, expands the preparation technical route of MXene, does not involve post-treatment processes such as pickling and drying, improves the preparation efficiency, the product MXene has high purity, and is easy to realize industrialized mass production.

Description

Technical Field

[0001] The present invention belongs to the field of new materials, specifically relates to two-dimensional materials, and particularly relates to an MXene prepared by gas-phase etching, and a method and use thereof. Background Art

[0002] MXene is a new type of two-dimensional compound in the field of materials science. These materials are composed of transition metal carbides, nitrides or carbonitrides with a thickness of several atomic layers. Currently, the reported MXene is mainly prepared by selectively etching the A-layer atoms in the MAX-phase material. The molecular formula of the MAX-phase material is expressed as M n+1 AX n , where M is an early transition metal element, A is selected from elements of Group IIIA or Group IVA, X is carbon or nitrogen, and n is 1, 2, 3 or 4. Since MXene was reported, it has attracted wide attention in the scientific community. Its rich compositional structure controllability, unique layered structure, high conductivity and other characteristics are considered to have great application potential in the fields of energy storage, electromagnetic shielding, etc.

[0003] At the present stage, the relatively mature methods for preparing MXene are mainly chemical liquid-phase etching method and molten salt etching method. The chemical liquid-phase method is achieved by etching the weakly bonded A-layer elements in the MAX-phase material with a mixed solution of hydrofluoric acid, fluoride salt and hydrochloric acid or ammonium bifluoride. Usually, the MAX-phase material and the high-concentration acidic solution are stirred at a certain temperature. After a certain period of etching, the A-layer elements in the MAX-phase material dissolve in the acidic solution. Through multiple washings with deionized water and centrifugation, the acidic solution is removed until the pH = 4 - 6, and then ultrasonic exfoliation is carried out to obtain the two-dimensional material MXene. The chemical liquid-phase etching method has cumbersome operations, high danger, and causes serious environmental pollution, greatly limiting the application prospects of MXene; the molten salt etching method is to mix metal chloride salts with the MAX-phase material at a high temperature state, and the metal chloride salts are in a molten state to etch the MAX-phase material. For example, the Ti3AlC2 MAX-phase reacts with the ZnCl2 molten salt, and the Zn 2+ cation acts as a Lewis acid to play the role of H + in HF acid, and the Cl - anion is equivalent to F - and finally coordinates with the M atom to prepare the MXene material. Although the molten salt etching method avoids the use of HF solution, there are still a large number of metal salt impurities in the obtained MXene product. To obtain the MXene powder product, repeated purification steps such as washing, ultrasonic treatment, centrifugation and drying are required, increasing the cost of the MXene material and limiting the application of MXene. Therefore, developing a new type of efficient and pollution-free preparation method helps to promote the industrialization of MXene. Summary of the Invention

[0004] The object of the present invention is to solve the technical problems that the preparation method of MXene materials is complex and it is difficult to achieve mass preparation. On the one hand, a method for preparing two-dimensional material MXene by gas-phase etching is provided. The MXene is obtained by an etching reaction between a gaseous etchant and a MAX-phase material. Among them, the etchant is selected from: metal chlorides; or chlorides of boron, chlorides of carbon, chlorides of silicon or chlorides of phosphorus; or one or more of chlorinated hydrocarbons; when the etchant is liquid or solid at room temperature, it further includes heating the etchant to convert the etchant into a gaseous state.

[0005] In some embodiments, the above-mentioned metal chlorides are selected from one or more of: aluminum trichloride, zinc dichloride, copper chloride, iron chloride, ferrous chloride; the above-mentioned chlorides of boron are selected from boron trichloride or boron dichloride tetrachloride; the above-mentioned chlorides of carbon are selected from carbon tetrachloride; the above-mentioned chlorides of silicon are selected from one or more of dichlorosilane, trichlorosilane or silicon tetrachloride; the above-mentioned chlorides of phosphorus are selected from phosphorus trichloride; the above-mentioned chlorinated hydrocarbons are selected from one or more of methyl chloride, methylene chloride, chloroform, ethyl chloride, dichloroethane, trichloroethane, propyl chloride, dichloropropane, or trichloropropane.

[0006] In some embodiments, when the etchant is liquid or solid at room temperature, it further includes heating the etchant to convert the etchant into a gaseous state.

[0007] In some embodiments, the temperature of the etching reaction is between 600 °C and 1100 °C; and / or, the time of the etching reaction is between 0.5 h and 12 h.

[0008] In some embodiments, the heating temperature is between 50 °C and 1000 °C.

[0009] In some embodiments, the etchant and the MAX-phase material are placed separately.

[0010] In some embodiments, the method of the present invention further includes a peeling step: placing the obtained MXene in a solvent for ultrasonic treatment, centrifugation and drying to obtain exfoliated MXene powder.

[0011] In some embodiments, the power of the ultrasonic treatment is between 300 W and 1000 W, and the ultrasonic time is between 0.5 h and 6 h; and / or, the rotation speed of the centrifugation is between 1000 rpm and 10000 rpm; and / or, the drying temperature is between 40 °C and 100 °C.

[0012] In some embodiments, the above-mentioned solvent includes: one or more of water, N-methylpyrrolidone, N,N-dimethylformamide, ethanol, isopropanol, methyl ethyl ketone or toluene.

[0013] In some embodiments, the molecular formula of the above MAX phase material is represented as M n+1 AX n , where M includes one or more of the elements scandium, titanium, vanadium, chromium, zirconium, niobium, molybdenum, hafnium, tantalum; A is selected from elements of Group IIIA or Group IVA; X is one or more of the elements carbon, nitrogen, boron; and n is 1, 2, 3, or 4; and / or,

[0014] The MAX phase material is in the form of powder, bulk, or thin film.

[0015] On the other hand, the present invention also provides an MXene material obtained by the above preparation method, which does not require purification treatment, has an accordion-like morphology, and contains -Cl functional groups on its surface.

[0016] On yet another aspect, the present invention also provides an energy storage device containing the MXene material obtained by the above method.

[0017] The present invention also includes the use of the above MXene material in batteries, supercapacitor materials, electromagnetic absorption, thermal barrier coatings and shielding materials, or catalysts.

[0018] The beneficial technical effects of the present invention are as follows:

[0019] 1) The method of the present invention provides new etching agents for preparing MXene, expands the preparation technical route of MXene, and also optimizes the etching conditions of these etching agents, that is, a gas-phase method is used to prepare MXene. When the etching agent is in solid or liquid state, it includes the process of converting the etching agent into gas state, and the obtained product does not contain solid impurities. After the etching reaction is completed, only by circulating inert gas in the tubular furnace, the impurity removal can be completed, without involving post-treatment processes such as pickling and drying, improving the preparation efficiency, and the obtained MXene product has high purity and is easy to realize industrial mass production.

[0020] 2) The method of the present invention obtains MXene with -Cl functional groups without further purification treatment; compared with the -F functional group-containing MXene obtained by chemical liquid-phase etching method (the -F functional group is unstable and is easily hydrolyzed to -OH), the -Cl functional group-containing MXene has better stability, which is beneficial to further functionalization treatment of the MXene material, such as replacing -Cl with other functional groups to realize the functionalization treatment of the MXene material. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 XRD spectra of Ti3C2T x MXene and its precursor Ti3AlC2 MAX phase in Example 1 of the present invention.

[0022] Figure 2 Scanning electron microscope images of the precursor Ti3AlC2 MAX phase (a) and Ti3C2T x MXene (b) in Example 1 of the present invention.

[0023] Figure 3 Transmission electron microscope image of Ti3C2T x MXene in Example 1 of the present invention.

[0024] Figure 4 XRD spectra of Ti3C2T x MXene and its precursor Ti3AlC2 MAX phase in Example 2 of the present invention.

[0025] Figure 5 Scanning electron microscope images of the precursor Ti3AlC2 MAX phase (a) and Ti3C2T x MXene (b) in Example 2 of the present invention.

[0026] Figure 6 Transmission electron microscope image of Ti3C2T x MXene in Example 2 of the present invention.

[0027] Figure 7 XRD spectra of Ti3C2T x MXene and its precursor Ti3AlC2 MAX phase in Example 3 of the present invention.

[0028] Figure 8 Scanning electron microscope images of the precursor Ti3AlC2 MAX phase (a) and Ti3C2T x MXene (b) in Example 3 of the present invention.

[0029] Figure 9 Transmission electron microscope image of Ti3C2T x MXene in Example 3 of the present invention.

[0030] Figure 10 Scanning electron microscope image of Ti3C2T x MXene in Example 4 of the present invention.

[0031] Figure 11 Scanning electron microscope image of Ti3C2T x MXene in Example 5 of the present invention.

[0032] Figure 12 Scanning electron microscope image of Ti3C2T x MXene in Example 6 of the present invention.

[0033] Figure 13For Ti3C2T in Embodiment 7 of the present invention x Scanning electron micrograph of MXene.

[0034] Figure 14 For Ti3C2T in Embodiment 8 of the present invention x Scanning electron micrograph of MXene.

[0035] Figure 15 For TiNbCT in Embodiment 9 of the present invention x Scanning electron micrograph of MXene.

[0036] Figure 16 For Ti3C2T in Embodiment 10 of the present invention x Scanning electron micrograph of MXene. Detailed implementation manners

[0037] The technical solutions of the present invention are described below through 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 combined steps, or other methods and steps can be inserted between these clearly mentioned steps. It should also be understood that these examples are only used to illustrate the present invention and not to limit the scope of the present invention. Unless otherwise specified, the numbers of the method steps are only for the purpose of identifying the method steps, rather than limiting the arrangement order of each method or limiting the implementation scope of the present invention. The change or adjustment of their relative relationship can also be regarded as the implementable scope of the present invention under the condition of no substantial change in technical content.

[0038] There is no specific limitation on the sources of the raw materials and instruments used in the embodiments, and they can be purchased in the market or prepared according to the conventional methods well-known to those skilled in the art.

[0039] In the method for preparing MXene by gas-phase etching of the present invention, the etchant is selected from: metal chlorides; or chlorides of boron, carbon, silicon or phosphorus; or one or more of chlorinated hydrocarbons; when the etchant is liquid or solid at room temperature, it further includes heating the etchant to convert the etchant into a gaseous state. For example, at room temperature, metal chlorides such as aluminum trichloride, zinc dichloride, copper chloride, iron chloride, ferrous chloride, etc. are solid etchants; liquid etchants include boron trichloride, diboron tetrachloride, dichloromethane, dichloroethane, chloroform, trichloroethane, carbon tetrachloride, silicon tetrachloride, phosphorus trichloride, 1-chloropropane, 2-chloropropane, 3-chloropropane, etc. Among them, boron trichloride may also be in a gaseous state (when the room temperature is higher than the boiling point of boron trichloride, 12.5 °C); gaseous etchants include chloromethane, chloroethane, etc. The technical feature of the present invention is that it is found that gaseous metal chlorides, chlorides of boron, carbon, silicon or phosphorus, and chlorinated hydrocarbons can also produce an etching effect, react with the MAX phase material by etching, and obtain the MXene material. This will be described in detail through specific examples below.

[0040] Example 1

[0041] This example takes the preparation of Ti3C2T x MXene as an example to illustrate the preparation method of the present invention. Among them, the precursor MAX phase is Ti3AlC2, and the etchant is aluminum trichloride, including the steps of:

[0042] 1) Heating step: Put 100 mg of Ti3AlC2 powder into a porcelain boat and place it in the middle area of the tube furnace. Place a porcelain boat containing an appropriate amount (5 g) of aluminum trichloride upstream of the tube furnace with independent temperature control. Under the condition of introducing a protective gas (argon, purity > 99.999%) into the tube, turn on the switch of the heating device for the part containing aluminum trichloride and heat it to 300 °C to cause the sublimation of aluminum trichloride and enter the middle area of the tube furnace;

[0043] 2) Etching step: When the temperature in the upstream tube reaches the set temperature of 300 °C, start the reaction timing. Raise the temperature in the tube at a rate of 10 °C / min to the reaction temperature of 950 °C, maintain the reaction temperature in the middle area of the tube furnace at 950 °C, and after the reaction time of 0.5 h, terminate the reaction and let it cool naturally.

[0044] Collect the product Ti3C2T x MXene obtained in step 2), and perform XRD tests on the product Ti3C2T x MXene and the precursor MAX phase Ti3AlC2. The results are as follows Figure 1As shown, after the etching reaction step, the intensity of the (104) diffraction peak of Ti3AlC2 at 39° decreased significantly, and the diffraction peaks of other crystal planes basically disappeared. The XRD pattern was consistent with the product obtained by etching with hydrofluoric acid. The diffraction peaks of (002), (004), (006), (008), etc. shifted significantly to lower angles, and the corresponding lattice parameter c value increased to 22.25 nm, which is higher than the c value of 18.56 nm of Ti3AlC2. XRD pattern analysis showed that the product was single-phase Ti3C2T x MXene, without other metal particle impurities, proving that aluminum trichloride can completely etch Ti3AlC2 MAX to prepare Ti3C2T x MXene has high purity.

[0045] Figure 2 are the scanning electron microscope images of the precursor MAX phase Ti3AlC2 (a) and the product Ti3C2T x MXene (b) obtained in step 2). Comparing with the closely packed layered structure of Ti3AlC2, Ti3C2T x MXene presents the unique "accordion" morphology structure because the Al atoms located between the Ti3C2 layers are removed, and the newly inserted Cl atoms cause the binding between the Ti3C2T x layers to weaken and the layer spacing to increase, thus showing a multi-layer structure.

[0046] Figure 3 is the product Ti3C2T x MXene obtained in step 2). The transmission electron microscope (a), high-resolution transmission electron microscope (b) and elemental surface distribution (c) images of Ti3C2T x MXene clearly show the hexagonal crystal structure characteristic of MXene, proving that the prepared product is Ti3C2T x MXene. Throughout the entire range of Ti3C2T x MXene nanosheets, the four elements of Ti, C, O and Cl are evenly distributed, proving that Ti3C2T

[0047] In some embodiments, the product of the present invention can be further exfoliated to exfoliate the accordion-shaped MXene material into sheets. The exfoliation treatment includes ultrasonic, centrifugal and drying treatments of the product of the present invention in a solvent. Preferably, the power of ultrasonic is between 300 W and 1000 W, and the ultrasonic time is between 0.5 h and 6 h; the rotation speed of the centrifugation is between 1000 rpm and 10000 rpm; the drying temperature is between 40 °C and 100 °C; the optional solvents include: one or more of water, N-methylpyrrolidone, N,N-dimethylformamide, ethanol, isopropanol, methyl ethyl ketone or toluene.

[0048] In this embodiment, the obtained product Ti3C2T x was placed in an isopropanol solvent and ultrasonically treated for 1 h at a power of 1000 W. After centrifugal washing at a rotation speed of 3000 revolutions, the obtained precipitate was dried to obtain MXene powder.

[0049] Example 2

[0050] This embodiment takes the preparation of Ti3C2T x MXene as an example to illustrate the preparation method of the present invention. Among them, the precursor MAX phase is Ti3AlC2, and the etching agent is zinc dichloride, including the steps:

[0051] 1) Heating step: Put 100 mg of Ti3AlC2 powder into a porcelain boat and place it in the middle area of a tube furnace. Place a porcelain boat containing an appropriate amount (5 g) of zinc dichloride upstream of the tube furnace with independently controllable temperature. Under the condition of introducing a protective gas (argon, purity > 99.999%) into the tube, turn on the switch of the heating device for the part containing zinc dichloride and heat it to 800 °C to cause the sublimation of zinc dichloride and enter the middle area of the tube furnace;

[0052] 2) Etching step: When the temperature in the upstream tube reaches the set temperature of 800 °C, start the reaction timing. Raise the temperature in the tube at a rate of 10 °C / min to the reaction temperature of 950 °C, keep the reaction temperature in the middle area of the tube furnace at 950 °C, and after the reaction time of 0.5 h, terminate the reaction and let it cool naturally.

[0053] Collect the product Ti3C2T x MXene obtained in step 2), and perform XRD tests on this product Ti3C2T x MXene and the precursor MAX phase Ti3AlC2. The results are as Figure 4 shown. After the etching reaction step, the diffraction peak intensity of Ti3AlC2 at 39° for the (104) plane decreases significantly, and the diffraction peaks of other crystal planes basically disappear. The XRD pattern is consistent with the product obtained by hydrofluoric acid etching. The diffraction peaks such as (002), (004), and (006) shift significantly to lower angles, and the corresponding lattice parameter c value increases to 22.15 nm, which is higher than the c value of 18.56 nm for Ti3AlC2. XRD pattern analysis shows that the product is single-phase Ti3C2T x MXene, without other metal particle impurities, proving that zinc dichloride can completely etch Ti3AlC2 MAX, and the prepared Ti3C2T x MXene has high purity.

[0054] Figure 5 is the precursor MAX phase Ti3AlC2 (a) and the product Ti3C2T obtained in step 2) xScanning electron microscope image of MXene(b). Compared with the closely packed layered structure of Ti3AlC2, Ti3C2T x MXene exhibits its unique "accordion" morphological structure because the Al atoms located between the Ti3C2 layers are removed, and the newly inserted Cl atoms cause Ti3C2T x The bonding between the layers is weakened, and the layer spacing increases, thus showing a multi-layer structure.

[0055] Figure 6 is the product Ti3C2T obtained in step 2) x Transmission electron microscope (a), high-resolution transmission electron microscope (b) and elemental surface distribution (c) images of MXene clearly show the hexagonal crystal structure characteristic of MXene, proving that the prepared product is Ti3C2T x MXene. Throughout the entire Ti3C2T x MXene nanosheets, the four elements Ti, C, O, and Cl are evenly distributed, proving that Ti3C2T x MXene contains -Cl functional groups.

[0056] Optionally, the product of the present invention can be further exfoliated to exfoliate the accordion-shaped MXene material into sheets. The obtained product Ti3C2T x is placed in an isopropanol solvent and ultrasonically treated for 1 h at a power of 500 W, and then centrifuged and washed. The centrifugation speed is 3000 revolutions, and the obtained precipitate is dried to obtain MXene powder.

[0057] In some embodiments, the etchant of this embodiment can also be selected from hydrates of aluminum chloride or zinc dichloride (AlCl3·6H2O or ZnCl2·H2O).

[0058] Example 3

[0059] This example takes the preparation of Ti3C2T x MXene as an example to illustrate the preparation method of the present invention. Among them, the precursor MAX phase is Ti3AlC2, and the etchant is phosphorus trichloride, including the steps:

[0060] 1) Heating step: Put 100 mg of Ti3AlC2 powder into a porcelain boat and place it in the middle area of the tube furnace. Place a porcelain boat containing an appropriate amount (2 ml) of phosphorus trichloride upstream of the independently temperature-controlled tube furnace. Under the condition of introducing a protective gas (argon, purity > 99.999%) into the tube, turn on the switch of the heating device for the part containing phosphorus trichloride and heat to 80 °C to make the phosphorus trichloride volatilize and enter the middle area of the tube furnace;

[0061] 2) Etching reaction step: When the temperature inside the upstream tube reaches the set temperature of 80 °C, start the reaction timing, increase the temperature inside the tube at a rate of 10 °C / min to the reaction temperature of 750 °C, maintain the reaction temperature of 750 °C in the middle area of the tube furnace, and after 0.5 h of reaction time, terminate the reaction and let it cool down naturally.

[0062] Collect the product Ti3C2T obtained in step 2) x MXene, and perform XRD tests on this product Ti3C2T x MXene and the precursor MAX phase Ti3AlC2. The results are as Figure 7 shown. After the etching reaction step, the intensity of the (104) diffraction peak of Ti3AlC2 at 39° decreases significantly, and the diffraction peaks of other crystal planes basically disappear. This XRD pattern is consistent with the product obtained by etching with hydrofluoric acid. The diffraction peaks of (002), (004), (006), (008), etc. shift significantly to lower angles, and the corresponding lattice parameter c value increases to 22.10 nm, which is higher than the c value of 18.56 nm of Ti3AlC2. XRD pattern analysis shows that the product is single-phase Ti3C2T x MXene, without other impurities, proving that phosphorus trichloride can completely etch Ti3AlC2 MAX, and the prepared Ti3C2T x MXene has high purity.

[0063] Figure 8 are the scanning electron microscope pictures of the precursor MAX phase Ti3AlC2 (a) and the product Ti3C2T x MXene (b) obtained in step 2). Comparing with the closely packed layered structure of Ti3AlC2, Ti3C2T x MXene presents the unique "accordion" morphology structure. This is because the Al atoms located between the Ti3C2 layers are removed, and the newly embedded Cl atoms cause the bonding between the Ti3C2T x layers to weaken and the layer spacing to increase, thus showing a multi-layer structure.

[0064] Figure 9 is the transmission electron microscope (a), high-resolution transmission electron microscope (b) and elemental surface distribution (c) pictures of the product Ti3C2T x MXene obtained in step 2). It clearly presents the hexagonal crystal structure characteristic of MXene, proving that the prepared product is Ti3C2T x MXene. Throughout the entire Ti3C2T x MXene nanosheets, the four elements of Ti, C, O and Cl are evenly distributed, proving that Ti3C2T x MXene contains -Cl functional groups.

[0065] Example 4

[0066] In this example, Ti3C2T x Taking MXene as an example, the preparation method of the present invention is described, wherein the precursor MAX phase is Ti3AlC2, and the etchant is dichloromethane, comprising the steps of:

[0067] 1) Heating step: 100 mg of Ti3AlC2 powder was placed in a porcelain boat in the middle area of ​​the tube furnace, and a porcelain boat containing an appropriate amount (2 ml) of dichloromethane was placed upstream of the tube furnace with independent temperature control. Under the condition of passing protective gas (argon, purity> 99.999%) into the tube, the switch of the heating device containing the dichloromethane was turned on and heated to 40°C so that the dichloromethane was heated and volatilized and entered the middle area of ​​the tube furnace;

[0068] 2) Etching reaction step: When the temperature in the upstream tube reaches the set temperature of 40°C, the reaction timing starts, and the temperature in the tube is increased at a rate of 10°C / min to a reaction temperature of 750°C. The reaction temperature in the middle area of ​​the tubular furnace is maintained at 750°C. After a reaction time of 0.5h, the reaction is terminated and the temperature is cooled naturally.

[0069] Collect the product Ti3C2T obtained in step 2) x Scanning electron microscopy test (such as Figure 10 As shown), it can be seen that the product presents a unique "accordion" morphology, indicating that dichloromethane has an etching effect.

[0070] Example 5

[0071] In this example, Ti3C2T x Taking MXene as an example, the preparation method of the present invention is described, wherein the precursor MAX phase is Ti3AlC2, and the etchant is gaseous boron trichloride, comprising the steps of:

[0072] 1) Heating step: 100 mg of Ti3AlC2 powder was placed in a porcelain boat in the middle area of ​​a tube furnace;

[0073] 2) While introducing boron trichloride and protective gas (argon, purity > 99.999%) into the tube, the temperature in the tube was raised to the reaction temperature of 750°C at a rate of 10°C / min, and kept at that temperature for 1 hour. The reaction was terminated and the temperature was lowered naturally.

[0074] Collect the product Ti3C2T obtained in step 2) x Scanning electron microscopy test (such as Figure 11 As shown), it can be seen that the product presents a unique "accordion" morphology, indicating that boron trichloride has an etching effect.

[0075] Example 6

[0076] In this embodiment, taking the preparation of Ti3C2T x MXene as an example, the preparation method of the present invention is described. Among them, the precursor MAX phase is selected as Ti3AlC2, and the etchant is gaseous methyl chloride, including the steps:

[0077] 1) Heating step: Put 100 mg of Ti3AlC2 powder into a porcelain boat and place it in the middle area of the tubular furnace;

[0078] 2) Under the condition of introducing methyl chloride and a protective gas (argon, purity > 99.999%) into the tube, raise the temperature in the tube to the reaction temperature of 750 °C at a rate of 10 °C / min, keep it warm for 1 h, and stop the reaction and let it cool naturally.

[0079] Collect the product Ti3C2T obtained in step 2) x Perform a scanning electron microscope test (as Figure 12 shown), it can be seen that the product presents the unique "accordion" morphology structure, indicating that methyl chloride has an etching effect.

[0080] The etchant in this embodiment can also be replaced with gaseous chloroethane.

[0081] Example 7

[0082] This embodiment has the same experimental conditions as Example 4, the difference is that: in the heating step, the etchant is replaced with chloroform, turn on the switch of the heating device for the part containing chloroform, heat it to 65 °C, and make the chloroform vaporize and enter the middle area of the tubular furnace; in the etching step, the reaction temperature is 800 °C. Collect the product Ti3C2T x Perform a scanning electron microscope test (as Figure 13 shown), it can be seen that the product presents the unique "accordion" morphology structure, indicating that chloroform has an etching effect.

[0083] Example 8

[0084] This embodiment has the same experimental conditions as Example 4, the difference is that: in the heating step, the etchant is replaced with carbon tetrachloride, turn on the switch of the heating device for the part containing carbon tetrachloride, heat it to 70 °C, and make the carbon tetrachloride vaporize and enter the middle area of the tubular furnace; in the etching step, the reaction temperature is 900 °C. Collect the product Ti3C2T x Perform a scanning electron microscope test (as Figure 14 shown), it can be seen that the product presents the unique "accordion" morphology structure, indicating that carbon tetrachloride has an etching effect.

[0085] Example 9

[0086] This example has the same experimental conditions as Example 4, except that: the precursor MAX phase is TiNbAlC, the etchant is aluminum trichloride, and it includes the steps:

[0087] In the heating step, replace the etchant with silicon tetrachloride, turn on the switch of the heating device for the part containing silicon tetrachloride, heat to 60 °C, and allow the silicon tetrachloride to vaporize and enter the middle area of the tube furnace; in the etching step, the reaction temperature is 1100 °C. The obtained product TiNbCT is collected. x Perform scanning electron microscopy tests (as Figure 15 shown), it can be seen that the product presents the unique "accordion" morphology structure, indicating that silicon tetrachloride has an etching effect.

[0088] Example 10

[0089] This example has the same experimental conditions as Example 4, except that: in the etching step, the reaction temperature is 600 °C, and after 12 h of reaction time. The obtained product Ti3C2T is collected. x Perform scanning electron microscopy tests (as Figure 16 shown), the product presents the unique "accordion" morphology structure, indicating that when the temperature is reduced and the etching time is extended, a good etching effect can also be achieved.

[0090] Example 11

[0091] Taking the preparation of Ti2CT x MXene as an example, the preparation method of the present invention is illustrated. Among them, the precursor MAX phase is Ti2AlC, and the etchant is copper chloride, including the steps:

[0092] Place 100 mg of Ti2AlC powder and (5 g) of copper chloride in different porcelain boats respectively, place them in the middle area of the tube furnace, and under the condition of introducing a protective gas (argon, purity > 99.999%) into the tube, turn on the switch of the heating device, heat to 1000 °C, keep warm for 3 h, and then terminate the reaction and cool down naturally.

[0093] Copper chloride sublimes into a gaseous state at a temperature of 1000 °C, and at the same time, the etching step is carried out to obtain Ti2CT x MXene.

[0094] Example 12

[0095] This example is similar to Example 1, except that the etchant is iron chloride. In the heating step, heat the porcelain boat containing iron chloride to 400 °C to allow the iron chloride to sublime and enter the middle area of the tube furnace.

[0096] The etchant in this example can also be replaced with ferrous chloride.

[0097] Example 13

[0098] This example is similar to Example 4, except that the etchant is dichloroethane. In the heating step, the porcelain boat containing dichloroethane is heated to 100 °C, causing the dichloroethane to vaporize and enter the middle region of the tube furnace.

[0099] The etchant in this example can also be replaced with trichloroethane.

[0100] Example 14

[0101] This example is similar to Example 4, except that the etchant is boron dichloride. In the heating step, the porcelain boat containing boron dichloride is heated to 70 °C, causing the boron dichloride to vaporize and enter the middle region of the tube furnace.

[0102] Example 15

[0103] This example provides a use of MXene in a coating. The powder of MXene obtained by ultrasonic exfoliation in Example 1 is added to the coating and mixed. The two-dimensional MXene material can form an ultrathin protective film in the coating and can be used as a thermal barrier coating, an anti-corrosion coating, or an electromagnetic shielding coating, etc.

[0104] The MXene material of the present invention can also be added as a modifying material to other matrices to form composite materials, such as being compounded with polymer materials.

[0105] Example 16

[0106] This example provides an energy storage device, which is a battery. The negative electrode material therein contains metallic lithium and the multi-component MXene material of the present invention. By doping the multi-component MXene material of the present invention, the surface tension of molten metallic lithium can be reduced, and then a composite material of ultrathin metallic lithium can be obtained and used as the negative electrode material of the battery. The MXene material of the present invention can also be applied to other types of energy storage devices, such as supercapacitors.

[0107] The foregoing description of specific exemplary embodiments of the present invention is for purposes of illustration and exemplification. These descriptions are not intended to limit the invention to the precise forms disclosed, and it is obvious that many changes and variations are possible in light of the above teaching. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical applications, so that those skilled in the art can implement and utilize various different exemplary embodiments of the present invention as well as various different selections and changes. The scope of the present invention is intended to be defined by the claims and their equivalents.

Claims

1. A method for preparing MXene by gas-phase etching, characterized in that, The MXene is obtained by an etching reaction of a gaseous etchant with a MAX phase material, wherein the etchant is selected from: metal chlorides; or, chlorides of boron, chlorides of silicon or chlorides of phosphorus; or, one or more of chloroalkanes; When the etchant is in a liquid or solid state at room temperature, it further includes placing the etchant separately from the MAX phase material and heating the etchant to convert it into a gaseous state.

2. The method according to claim 1, characterized in that, The metal chlorides are selected from one or more of aluminum trichloride, zinc dichloride, copper chloride, iron chloride, ferrous chloride; The chlorides of boron are selected from boron trichloride or dichlorodiborane; The chlorides of silicon are selected from one or more of dichlorosilane, trichlorosilane or silicon tetrachloride; The chlorides of phosphorus are selected from phosphorus trichloride; The chloroalkanes are selected from one or more of chloromethane, dichloromethane, trichloromethane, carbon tetrachloride, chloroethane, dichloroethane, trichloroethane, chloropropane, dichloropropane or trichloropropane.

3. The method according to claim 1, wherein The temperature of the etching reaction is between 600 °C and 1100 °C; and / or, The time of the etching reaction is between 0.5 h and 12 h.

4. The method according to any one of claims 1 to 3, characterized in that, The temperature of the heating is between 50 °C and 1000 °C.

5. The method according to any one of claims 1 to 3, characterized in that It further includes a peeling step: placing the obtained MXene in a solvent for ultrasonic treatment, centrifugation and drying to obtain exfoliated MXene powder.

6. The method according to claim 5, wherein The power of the ultrasonic treatment is between 300 W and 1000 W, and the ultrasonic time is between 0.5 h and 6 h; and / or, The rotation speed of the centrifugation is between 1000 rpm and 10000 rpm; and / or, The temperature of the drying is between 40 °C and 100 °C; and / or, The solvent includes one or more of water, N-methylpyrrolidone, N,N-dimethylformamide, ethanol, isopropanol, methyl ethyl ketone or toluene.

7. The method according to any one of claims 1 to 3, characterized in that The molecular formula of the MAX phase material described is expressed as M n+1 AX n , where M contains one or more of the elements scandium, titanium, vanadium, chromium, zirconium, niobium, molybdenum, hafnium, tantalum, A is selected from elements of Group IIIA or Group IVA, X is one or more of the elements carbon, nitrogen, boron, and n is 1, 2, 3, or 4; and / or, The morphology of the MAX phase material is powder, bulk or film.

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