A method for in-situ etching of MXenes at high temperature using organic salts and its preparation and application

Abstract

This invention discloses an MXenes material prepared by high-temperature in-situ etching using organic salts, its preparation method, and its applications. It belongs to the field of two-dimensional metal carbide preparation technology. The preparation method specifically includes the following steps: S1: Mixing MAX phase precursor material and organic Lewis acid salts according to a specified ratio, and grinding the mixture to below 200 mesh using a mortar; S2: Placing the ground mixture from step S1 in a corundum crucible, heating it to melting point in a controllable tube furnace under inert gas protection, holding it at that temperature for a certain time, and then cooling it down; S3: Removing impurities from the etching product obtained in step S2 by water washing, ultrasonic centrifugation, and peeling to obtain pure MXenes material. This MXenes material preparation method is simple to operate, increases yield, and reduces cost. The prepared MXenes material exhibits good chemical stability and electrochemical performance, highly tunable surface end groups and dielectric properties, and has a wide range of applications.

Description

Technical Field

[0001] This invention relates to the preparation of two-dimensional materials, specifically to MXenes prepared by high-temperature in-situ etching with organic salts, and their preparation method and application, belonging to the field of two-dimensional metal carbide preparation technology. Background Technology

[0002] MXenes are two-dimensional materials, and these novel MXenes have attracted widespread attention and extensive research due to their unique chemical, electrochemical, and physical properties. Since Naguib et al. reported the first MXene material in 2011, the MXene family has continued to grow. MXenes, as a class of layered two-dimensional carbides / nitrides, are typically obtained by chemical etching to extract the A-layer atoms from the parent material MAX phase (Mn+1AXn, n=1-3, M is a transition metal, A is a group IIIA or IVA element, X is C or N). MXenes are the largest family of two-dimensional materials to date, containing 3 to 9 thin atomic layers. They are the most numerous, strongest, and most conductive materials among all 2D materials. Furthermore, MXenes possess excellent performance characteristics, including high metallic conductivity, tunable electrical conductivity and work function, high strength and hardness, and ease of integration with various structural materials. Based on this, MXenes materials have shown potential application value in fields such as energy storage and conversion, electromagnetic shielding, gas sensing, catalysis, gas separation, biomedicine, and seawater desalination.

[0003] Recent research has revealed that MXenes preparation involves two main processes: low-temperature hydrofluoric acid etching and high-temperature chloride molten salt etching. Low-temperature hydrofluoric acid etching is highly hazardous (hydrofluoric acid is highly corrosive), has a long reaction time, and can only etch Al-based MAX phases. High-temperature chloride molten salt etching offers shorter etching times and extremely high success rates, but the high temperature and pressure impose stringent equipment requirements. Furthermore, the large amount of chloride molten salt results in numerous impurities in the product, making purification difficult, and the -Cl end groups on the MXenes surface are extremely challenging to control. Currently, the environmental pollution and unavoidable -O end groups during the preparation of MAX phase materials reported in the literature, such as Ti3AlC2, Ti2AlC, V2AlC, Ti3SiC2, Ti3GeC2, Mo2Ga2C, Ti4AlN3, Ti3GeC2, and Nb2AlC, significantly limit the application prospects of MXenes materials. To date, accordion-shaped multilayer MXenes materials can be selectively removed from the A-site of the MAX phase using etching reagents such as acids, bases, or molten salts. However, multilayer MXenes exhibit interlayer interactions, and preventing subsequent exfoliation and dispersion requires the use of different intercalating agents for exfoliation. After years of experimental research, two common etching methods have emerged: low-temperature in-situ synthesis of HF and high-temperature molten salt etching. The in-situ synthesis of HF uses LiCl and HCl to generate HF as the etchant and LiF as the intercalating agent, exfoliating multilayer MXenes materials with few or no layers. The high-temperature molten salt method uses KCl and NaCl as high-temperature molten salts and CuCl2 as the etchant to prepare multilayer MXenes. Simultaneously, the reaction product Cu can act as an intercalating agent, effectively increasing the interlayer spacing of the multilayer product and improving exfoliation efficiency. In summary, existing etching methods suffer from problems such as long reaction times, difficult experimental operation, difficulty in exfoliation, and low yield. These issues have prevented MXenes materials from meeting the demands of commercial production.

[0004] Currently, patent CN116969461A discloses a method and application for preparing two-dimensional layered MXene by high-temperature calcination etching. It discloses that the MAX phase material is mixed evenly with an etchant, then calcined at high temperature under inert gas protection, followed by centrifugal washing, peeling and drying to obtain a single-layer MXene material. The reaction path of this method is simply to etch away the Al layer in the MAX phase. The final product is pure phase MXene. Due to the lack of in-situ interlayer support or intercalating agent, the two-dimensional layered structure generated at high temperature is prone to secondary stacking in subsequent processing, resulting in a decrease in specific surface area.

[0005] Patent CN114843510B discloses a method for preparing metal-sulfur in-situ co-doped MXene electrode material. The method involves grinding MAX products, mixing them with Lewis molten salt, calcining them in a tube furnace under an inert atmosphere, and finally washing with deionized water to obtain the metal-sulfur in-situ co-doped MXene material. This method requires the time-consuming and energy-intensive synthesis of a specially prepared S-MAX precursor at 1650℃, which is not only cumbersome but also makes it extremely difficult to ensure the uniformity of sulfur doping. Furthermore, using chlorides as etchants introduces different end groups, resulting in high technical requirements, a long preparation cycle, and the inability to homogenize the end groups.

[0006] Patent CN117303365A describes an MXene material with CF3SO3- as a surface group, its preparation method, and its application. The method involves mixing a MAX phase precursor material with an etching solution containing an organic Lewis acid solution or an organic Lewis salt solution to obtain a mixed dispersion. This dispersion is then reacted in an inert environment, washed, sonicated, and centrifuged to obtain an MXene monolayer nanosheet dispersion. Further processing yields the MXene material. The main purpose of this method is to prepare novel MXenes materials with CF3SO3- as a surface group. However, room temperature / solution preparation is highly corrosive and the waste liquid and materials are difficult to handle.

[0007] Therefore, finding a Lewis salt that can overcome the above defects and be effectively etched at high temperatures, and whose products can be effectively exfoliated, is of great significance for preparing novel MXenes materials and regulating their properties, improving the application prospects of materials in different fields, and expanding new applications in more industries. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide MXenes etched in situ at high temperature using organic salts, as well as their preparation method and application. The preparation method of the MXenes material is simple to operate, improves the yield and reduces the cost. The prepared MXenes material has good chemical stability and electrochemical performance, highly tunable surface end groups and dielectric properties, and has a wide range of applications.

[0009] To address the above technical problems, this invention provides a method for preparing MXenes using high-temperature in-situ etching with organic salts, specifically comprising the following steps: Step S1: Mix the MAX phase precursor material and the organic Lewis acid salt according to the specified ratio, and grind the mixture to below 200 mesh using a mortar and pestle; Step S2: Place the ground mixed raw materials from step S1 into a corundum crucible, heat it to the point of melting in a controllable tube furnace protected by inert gas, hold it at that temperature for a certain period of time, and then cool it down. Step S3: Remove impurities from the etching product obtained in step S2 by water washing and ultrasonic centrifugation to obtain pure MXenes material.

[0010] The technical solution further defined in this invention is: Furthermore, in the aforementioned method for preparing MXenes by high-temperature in-situ etching using organic salts, the organic Lewis acid salt in step S1 is a trifluoromethanesulfonate, which includes one or more combinations of LiCF3SO3, NaCF3SO3, KCF3SO3, Mg(CF3SO3)2, Cu(CF3SO3)2, Zn(CF3SO3)2, Fe(CF3SO3)3, Ni(CF3SO3)2, Co(CF3SO3)2, Mn(CF3SO3)2, and AgCF3SO3.

[0011] The proposed method utilizes trifluoromethanesulfonate as an etchant to achieve effective etching of the MAX phase. Furthermore, in-situ modification of the MXene surface can be achieved during the etching process. Simple high-temperature heating avoids unnecessary oxidation and hydrolysis while preserving the metallic properties of MXene. The preparation method is simple, efficient, and environmentally friendly, avoiding many drawbacks of using highly toxic and hazardous hydrofluoric acid (HF) solutions as etchants for MXene preparation. This etching method can effectively control the physical and chemical properties of MXene materials, and is expected to further promote the functional applications and large-scale preparation of MXenes, such as their applications in catalysis, energy storage, and sensing.

[0012] In the aforementioned method for preparing MXenes by high-temperature in-situ etching using organic salts, the MAX phase precursor material in step S1 includes one or more combinations of Ti3AlC2, Ti3SiC2, Ti2AlC, Ti2AlN, Ti4AlN3, Ti2GaC, V2AlC, V2GaC, Cr2GaN, Cr2AlC, Sc2AlC, Zr2AlC, Zr2SnC, Nb2AlC, Nb4AlC3, Mo2AlC, Mo2GaN, Hf2AlC, Hf2AlN, Ta3AlC2, and Ta4AlC3.

[0013] In the aforementioned method for preparing MXenes by high-temperature in-situ etching using organic salts, the molar ratio required for mixing the two raw materials varies depending on the type of organic salt. The molar ratio of Cu salt to the MAX phase is 4:1, and the molar ratio of other organic salts (such as Zn salt) to the MAX phase is 6:1. Specifically, in step S1, the molar ratio of Cu(CF3SO3)2 to MAX phase precursor material is 4:1, and the molar ratio of any component among LiCF3SO3, NaCF3SO3, KCF3SO3, Mg(CF3SO3)2, Zn(CF3SO3)2, Fe(CF3SO3)3, Ni(CF3SO3)2, Co(CF3SO3)2, Mn(CF3SO3)2, and AgCF3SO3 to the MAX phase precursor material is 6:1.

[0014] In the aforementioned method for preparing MXenes by high-temperature in-situ etching using organic salts, the inert gas in step S2 is argon, and the gas flow rate is 50 mL / min.

[0015] In the aforementioned method for preparing MXenes by high-temperature in-situ etching using organic salts, in step S2, the controlled tube furnace is heated to 700°C at a rate of 5°C / min and held at that temperature for 6 hours. Then, the temperature control program is turned off, and the furnace is cooled to room temperature under argon protection.

[0016] In the aforementioned method for preparing MXenes by high-temperature in-situ etching using organic salts, the etching product is a mixture of MXenes and byproducts, wherein the byproducts are AlF3 and metal sulfides. The metal sulfides (such as ZnS or CuS) can bind to the end groups of MXenes, while AlF3 exists alone. The main impurity in the etching product is AlF3, which is removed from the system by repeated peeling using deionized water washing, ultrasonication, centrifugation, and other methods.

[0017] In the aforementioned method for preparing MXenes by high-temperature in-situ etching with organic salts, the MXenes material obtained contains 1.0-99.9 wt% MXenes. After removing impurities in step S3, the MXenes material is vacuum-assisted dried to make the MXenes material into a uniform powder with a particle size between 1-100 μm.

[0018] This invention also relates to an MXenes material, which is prepared by high-temperature in-situ etching of organic salts.

[0019] This invention also relates to the application of MXenes materials in electrochemical energy storage electrode materials, supercapacitor materials, electromagnetic absorption and shielding materials, infrared absorption and shielding materials, and photoelectrocatalysis.

[0020] The beneficial effects of this invention are: Compared with the prior art, this application has the following advantages: (1) the intercalating agent and the etchant are achieved in the decomposition of organic Lewis salts, and the metal sulfide obtained by the reaction can form a heterostructure with MXenes, thereby improving the performance of the product; (2) the conventional MAX phase is directly used to combine sulfidation, etching and metal deposition into one step (700℃) and greatly reduce the preparation cycle, while also ensuring the homogenization of the end groups; (3) the main purpose is to construct a new high-temperature molten salt system and prepare functional composite materials with heterostructures in one step. The process is simple and does not easily generate waste liquid or waste material.

[0021] This invention utilizes trifluoromethanesulfonate to achieve a three-in-one role as a high-temperature molten salt, intercalating agent, and etchant in the system, thereby improving the etching effect of MXenes. The introduction of the intercalating agent increases the interlayer spacing between MXenes layers, which significantly enhances the performance of MXenes as electrode or energy storage materials. The extensive modulation of the -F end groups results in extremely strong electronegativity, low surface energy, and unique chemical affinity, making it highly valuable for applications requiring extremely high capacitance or hydrophilicity. Most importantly, this product enables one-step loading of metal compounds, and the MXenes composite material loaded with metal sulfides exhibits excellent performance in electromagnetic / thermal shielding. Attached Figure Description

[0022] Figure 1 This is a flowchart illustrating the preparation process of MXenes materials in an embodiment of the present invention. Figure 2 The XRD patterns of MXenes and raw materials in Example 1 of this invention are shown below: (a) XRD curves of Ti3C2Tx MXenes and Zn(CF3SO3)2 obtained by etching Ti3AlC2MAX phase and Zn(CF3SO3)2 with different molar ratios; (b) A partial magnified view of Figure (a); (c) XRD pattern of MAX phase and Zn(CF3SO3)2 with a molar ratio of 1:6 without water washing and filtration. Figure 3 Here are the SEM and EDS images of the MXenes-based composite material in Example 1 of this invention: (ad) SEM images of Ti3C2Tx MXene at different magnifications; (e) EDS image, i.e., the distribution of each element. Figure 4 The images shown are TEM and EDS images of the MXenes-based composite material shown in Example 1 of this invention. Figure 5 The XPS spectrum of MXenes shown in Embodiment 1 of the present invention; Figure 6The infrared and Raman spectra of the MXenes material shown in Example 1 of the present invention are as follows: (a) Fourier transform infrared spectrum of Ti3C2Tx MXene; (b) Raman spectrum of Ti3C2Tx MXene.

[0023] Figure 7 The XRD patterns and magnified views of the Mo2CTx-MXenes, MAX phase and HF etching products in Example 2 of this invention are shown. Figure 8 The SEM images of the MXenes-based composite material in Example 2 of this invention are shown in (ab) and (c) respectively. The SEM images of Mo2CTxMXenes at different magnifications are shown in (b) respectively. The EDS diagram is shown in (c) respectively. Figure 9 The images shown are TEM and EDS images of the MXenes-based composite material in Example 2 of this invention. Figure 10 The XPS spectrum of MXenes shown in Embodiment 2 of the present invention; Figure 11 The infrared and Raman spectra of the MXenes material shown in Example 2 of this invention are shown. Detailed Implementation

[0024] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are implemented based on the technical solutions of the present invention, providing detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments. All other embodiments obtained by those skilled in the art based on the given embodiments without innovative effort are within the scope of protection of this application.

[0025] Unless otherwise specified, the reagents, methods, instruments and equipment used in this invention are all conventional reagents, methods, instruments and equipment in the art.

[0026] In the following embodiments, the MAX phase of the two-dimensional layered material precursor includes Ti3AlC2, Ti3SiC2, Ti2AlC, Ti2AlN, Ti4AlN3, Ti2GaC, V2AlC, V2GaC, Cr2GaN, Cr2AlC, Sc2AlC, Zr2AlC, Zr2SnC, Nb2AlC, Nb4AlC3, Mo2AlC, Mo2GaN, Hf2AlC, Hf2AlN, Ta3AlC2, and Ta4AlC3. One or more combinations of L3; organic Lewis salts (trifluoromethanesulfonates) including one or more combinations of LiCF3SO3, NaCF3SO3, KCF3SO3, Mg(CF3SO3)2, Cu(CF3SO3)2, Zn(CF3SO3)2, Fe(CF3SO3)3, Ni(CF3SO3)2, Co(CF3SO3)2, Mn(CF3SO3)2, and AgCF3SO3, wherein the purity of the above drugs is ≥90%. The wt.% particle size ranges from 0.5 to 25 μm. The reagents were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. Among them, LiCF3SO3, NaCF3SO3, KCF3SO3, Mg(CF3SO3)2, Cu(CF3SO3)2, Zn(CF3SO3)2, Fe(CF3SO3)3, Ni(CF3SO3)2, Co(CF3SO3)2, Mn(CF3SO3)2, and AgCF3SO3 were all of analytical grade and were available for purchase on the market. They were used without purification. Example 1

[0027] This embodiment provides a method for preparing MXenes using high-temperature in-situ etching with organic salts, the process of which is as follows: Figure 1 As shown, the specific steps include: S1: In a glove box protected by inert gas, weigh 0.5g of the precursor MAX phase Ti3AlC2 and 5.63g of the organic Lewis acid Zn(CF3SO3)2, with a molar ratio of 1:6. Grind them thoroughly in an agate mortar to powders below 10μm. Mix them thoroughly and then store them in a disposable test tube to minimize the contact between the mixture and air (trifluoromethanesulfonate is hygroscopic). S2: Transfer the mixed raw materials to a 35 mL corundum crucible and place it in a tube furnace with an adjustable atmosphere (the airtightness of the tube furnace needs to be checked in advance). Use argon gas with a flow rate of 50 mL / min to purge the air from the tube furnace and keep the argon gas flow rate constant throughout the experiment until the end of the experiment. After the tubular furnace has been fully vented, the heating rate is set to 5°C / min. -1After raising the temperature to 700℃, hold it at that temperature for 6 hours, stop the heating program, keep the inert atmosphere flow rate constant, and take the sample out after it cools down to room temperature with the furnace. Then, wash the sample repeatedly with deionized water in a vacuum-assisted filtration device with atmosphere control until the sample is pure. Use filter paper with a pore size of 0.4μm during the filtration process, and use the same filter paper in the repeated filtration process. S3: The washed sample needs to be ultrasonically treated for more than 30 minutes with an ultrasonic power of 50W. After ultrasonic treatment, the sample is centrifuged in a vacuum centrifuge at 3500rpm for 30 minutes to separate impurities. The sample after impurity removal needs to be vacuum-assisted filtered again to remove excess water. S4: The filtered sample needs to be dehydrated in a vacuum drying oven, with a vacuum level of not less than 10. -5 After vacuum drying at room temperature for 12 hours, the prepared sample was ground again in a vacuum glove box to a finished powder of less than 10 μm and collected in disposable test tubes and placed in a storage cabinet protected by inert gas.

[0028] The above reaction product powder was subjected to X-ray diffraction (XRD) analysis, such as... Figure 2 As shown in the figure, by comparison, it can be seen that after the reaction, the characteristic peaks of Zn(CF3SO3)2 disappear as follows: Figure 2 In Figure a, the reaction product shows the characteristic (002) peak of the Ti3C2TxMXenes phase at 7°, as shown in Figure a. Figure 2 Figure b in the image demonstrates that the MXenes phase was successfully etched using this method, compared to the unwashed and unfiltered phase. Figure 2 Figure c in the middle; The microstructure of the prepared MXenes samples was analyzed using scanning electron microscopy (SEM), such as... Figure 3 As shown in the mid-AD image, the sample exhibits a distinct accordion shape, and the interlayer spacing between the multiple MXenes is relatively large; Figure 3 As shown in Figure e, ZnS particles are uniformly distributed on the surface of MXenes, and strong bonds are formed between ZnS and MXenes, constituting a heterostructure that effectively enhances the performance of MXenes-based functional materials. (MXenes are two-dimensional materials with good physicochemical properties and can be used as functional materials on their own. The purpose of loading MXenes-based materials with other compounds is to improve their performance as functional materials. Here, "functional materials" refers to any material with certain application value that can achieve a specific function.) Using a projection electron microscope (TEM) such as Figure 4Figure a shows further microstructure and micro / nanostructure analysis of the above MXenes-based composite material. High-resolution transmission electron microscopy (HRTEM) images reveal that the lattice spacing of the (101) plane is 0.227 nm. Figure 4 Figure b, and at the same time Figure 4 The lattice spacing of the (002) plane of the ZnS material loaded in the d-plot is 0.31 nm. Figure 4 As shown in Figure c.

[0029] The atomic structure and bonding of MXenes and ZnS were analyzed using X-ray photoelectron spectroscopy (XPS), such as... Figure 5 The spectra of Ti 2p, Zn 2p, and S 2p show that Ti and Zn have a bonding relationship, thus proving that MXenes and ZnS form a heterostructure.

[0030] Further analysis of the chemical bond composition in the product was performed using Fourier transform infrared spectroscopy (FITR), such as... Figure 6 The diagram shows the characteristic peaks of MXenes and their -O and -F end groups. Example 2

[0031] This embodiment provides a method for preparing MXenes using high-temperature in-situ etching with organic salts, the process of which is as follows: Figure 1 As shown, the specific steps include: S1: In a glove box protected by inert gas, weigh 1.0 g of the precursor MAX phase Mo2Ga2C and 4.20 g of the organic Lewis acid Cu(CF3SO3)2, with a molar ratio of 1:4. Grind them thoroughly in an agate mortar to powders below 10 μm. Mix them thoroughly and then store them in a disposable test tube to minimize the contact between the mixture and air (trifluoromethanesulfonate is hygroscopic). S2: Transfer the mixed raw materials to a 35 mL corundum crucible and place it in a tube furnace with an adjustable atmosphere (the airtightness of the tube furnace needs to be checked in advance). Use argon gas with a flow rate of 50 mL / min to purge the air from the tube furnace and keep the argon gas flow rate constant throughout the experiment until the end of the experiment. After the tubular furnace has been fully vented, the heating rate is set to 5°C / min. -1 After raising the temperature to 700℃, hold it at that temperature for 6 hours, stop the heating program, keep the inert atmosphere flow rate constant, and take the sample out after it cools down to room temperature with the furnace. Then, wash the sample repeatedly with deionized water in a vacuum-assisted filtration device with atmosphere control until the sample is pure. Use filter paper with a pore size of 0.4μm during the filtration process, and use the same filter paper in the repeated filtration process. S3: The washed sample needs to be ultrasonically treated for more than 30 minutes with an ultrasonic power of 50W. After ultrasonic treatment, the sample is centrifuged in a vacuum centrifuge at 3500rpm for 30 minutes to separate impurities. The sample after impurity removal needs to be vacuum-assisted filtered again to remove excess water. S4: The filtered sample needs to be dehydrated in a vacuum drying oven, with a vacuum level of not less than 10. -5 After vacuum drying at room temperature for 12 hours, the prepared sample was ground again in a vacuum glove box to a finished powder of less than 10 μm and collected in disposable test tubes and placed in a storage cabinet protected by inert gas.

[0032] The above reaction product powder was subjected to X-ray diffraction (XRD) analysis, such as... Figure 7 As shown in the figure, by comparison, it can be seen that after the reaction, the reaction product showed the (002) characteristic peak of the Mo2CTx MXenes phase at 6° and 41°, which proves that the Mo2CTx MXenes phase was successfully etched by this method. Compared with the MXenes prepared by HF etching, the characteristic peak shifted slightly to the left.

[0033] The microstructure of the prepared MXenes samples was analyzed using scanning electron microscopy (SEM), such as... Figure 8 As shown in the figure, the sample exhibits a distinct accordion shape, with a large interlayer spacing between the multiple Mo2CTx MXenes layers. The figure also shows that CuS particles are uniformly distributed on the surface of the Mo2CTx MXenes.

[0034] Further microstructure and micro / nanostructure analysis of the above Mo2CTx MXenes-based composite material was performed using transmission electron microscopy (TEM). Figure 9 As shown in the high-resolution projection (HRTEM) images, the size of the Mo2CTx MXenes nanosheets (9a) is around 500 nm. 9b shows the interlayer spacing of MXenes, which is approximately 0.91 nm. 9c is a HRTEM image of CuS loaded with a metal compound, with a lattice spacing of 0.26 nm. Figure 9 Energy spectrum surface scan results for d=9a.

[0035] The atomic structure and bonding of MXenes and ZnS nanomaterials were analyzed using X-ray photoelectron spectroscopy (XPS). Figure 10 As shown in the diagram, the Mo 3d, Cu 2p and S 2p spectra reveal that MXenes possess multiple end groups -O and -F, as well as supported CuS metal sulfides.

[0036] The chemical bond composition of the product was further analyzed using Fourier transform infrared spectroscopy (FITR). For example... Figure 11 As shown, the characteristic peaks of Mo2CTx MXenes and their corresponding composite end groups can be observed. Example 3

[0037] This embodiment provides a method for preparing MXenes using high-temperature in-situ etching with organic salts, the process of which is as follows: Figure 1 As shown, the specific steps include: S1: In a glove box protected by inert gas, weigh 0.5g of the precursor MAX phase V2AlC and 5.13g of the organic Lewis acid Cu(CF3SO3)2, with a molar ratio of 1:4. Grind them thoroughly in an agate mortar to powders below 10μm. Mix them thoroughly and then store them in a disposable test tube to minimize the contact between the mixture and air (trifluoromethanesulfonate is hygroscopic). S2: Transfer the mixed raw materials to a 35 mL corundum crucible and place it in a tube furnace with an adjustable atmosphere (the airtightness of the tube furnace needs to be checked in advance). Use argon gas with a flow rate of 50 mL / min to purge the air from the tube furnace and keep the argon gas flow rate constant throughout the experiment until the end of the experiment. After the tubular furnace has been fully vented, the heating rate is set to 5°C / min. -1 After raising the temperature to 700℃, hold it at that temperature for 6 hours, stop the heating program, keep the inert atmosphere flow rate constant, and take the sample out after it cools down to room temperature with the furnace. Then, wash the sample repeatedly with deionized water in a vacuum-assisted filtration device with atmosphere control until the sample is pure. Use filter paper with a pore size of 0.4μm during the filtration process, and use the same filter paper in the repeated filtration process. S3: The washed sample needs to be ultrasonically treated for more than 30 minutes with an ultrasonic power of 50W. After ultrasonic treatment, the sample is centrifuged in a vacuum centrifuge at 3500rpm for 30 minutes to separate impurities. The sample after impurity removal needs to be vacuum-assisted filtered again to remove excess water. S4: The filtered sample needs to be dehydrated in a vacuum drying oven, with a vacuum level of not less than 10. -5 After vacuum drying at room temperature for 12 hours, the prepared sample was ground again in a vacuum glove box to a finished powder of less than 10 μm and collected in disposable test tubes and placed in a storage cabinet protected by inert gas.

[0038] The microstructure of the prepared MXenes samples was analyzed using scanning electron microscopy (SEM). The multilayer V2CTxMXenes also exhibited an accordion-like morphology with large interlayer spacing, while CuS metal compounds were loaded in the form of particles between the multilayers of MXenes. Example 4

[0039] Compared with Example 1, the precursor MAX phase was replaced with Mo2GaN, the molar ratio of MAX phase to Zn(CF3SO3)2 was kept at 1:6, and the experimental conditions and operations remained unchanged. Example 5

[0040] Compared with Example 1, the precursor MAX phase was replaced with V2AlC, the molar ratio of MAX phase to Zn(CF3SO3)2 was kept at 1:6, and the experimental conditions and operations remained unchanged. Example 6

[0041] Compared with Example 1, the precursor MAX phase was replaced with V2GaC, the molar ratio of MAX phase to Zn(CF3SO3)2 was kept at 1:6, and the experimental conditions and operations remained unchanged. Example 7

[0042] Compared with Example 1, the precursor MAX phase was replaced with Cr2GaN, the molar ratio of MAX phase to Zn(CF3SO3)2 was kept at 1:6, and the experimental conditions and operations remained unchanged. Example 8

[0043] Compared with Example 1, the precursor MAX phase was replaced with Cr2AlC, the molar ratio of MAX phase to Zn(CF3SO3)2 was kept at 1:6, and the experimental conditions and operations remained unchanged. Example 9

[0044] Compared with Example 1, the precursor MAX phase was replaced with Sc2AlC, the molar ratio of MAX phase to Zn(CF3SO3)2 was kept at 1:6, and the experimental conditions and operations remained unchanged. Example 10

[0045] Compared with Example 1, the precursor MAX phase was replaced with Zr2AlC, the molar ratio of MAX phase to Zn(CF3SO3)2 was kept at 1:6, and the experimental conditions and operations remained unchanged. Example 11

[0046] Compared with Example 1, the precursor MAX phase was replaced with Zr2SnC, the molar ratio of MAX phase to Zn(CF3SO3)2 was kept at 1:6, and the experimental conditions and operations remained unchanged. Example 12

[0047] Compared with Example 1, the precursor MAX phase was replaced with Nb2AlC, the molar ratio of MAX phase to Zn(CF3SO3)2 was kept at 1:6, and the experimental conditions and operations remained unchanged. Example 13

[0048] Compared with Example 2, the precursor MAX phase was replaced with Ti2AlC, and the molar ratio of MAX phase to Cu(CF3SO3)2 was kept to 1:6. The experimental conditions and operations remained unchanged. Example 14

[0049] Compared with Example 3, the precursor MAX phase was replaced with V2GaC, the molar ratio of MAX phase to Cu(CF3SO3)2 was kept at 1:4, and the experimental conditions and operations remained unchanged. Example 15

[0050] Compared with Example 3, the precursor MAX phase was replaced with Cr2GaN, the molar ratio of MAX phase to Cu(CF3SO3)2 was kept at 1:4, and the experimental conditions and operations remained unchanged. Example 16

[0051] Compared with Example 3, the precursor MAX phase was replaced with Cr2AlC, the molar ratio of MAX phase to Cu(CF3SO3)2 was kept at 1:4, and the experimental conditions and operations remained unchanged. Example 17

[0052] Compared with Example 2, the precursor MAX phase was replaced with Sc2AlC, the molar ratio of MAX phase to Cu(CF3SO3)2 was kept at 1:4, and the experimental conditions and operations remained unchanged. Example 18

[0053] Compared with Example 1, the precursor MAX phase was replaced with Zr2AlC, the molar ratio of MAX phase to Cu(CF3SO3)2 was kept at 1:6, and the experimental conditions and operations remained unchanged. Example 19

[0054] Compared with Example 1, the precursor MAX phase was replaced with Zr2SnC, the molar ratio of MAX phase to Cu(CF3SO3)2 was kept at 1:4, and the experimental conditions and operations remained unchanged. Example 20

[0055] Compared with Example 1, the precursor MAX phase was replaced with Nb2AlC, the molar ratio of MAX phase to Cu(CF3SO3)2 was kept at 1:4, and the experimental conditions and operations remained unchanged.

[0056] The above embodiments are divided into two categories, namely, the etchant is Zn salt or Cu salt. Each type of salt etched three types of MAX phases, namely Ti3AlC2, V2AlC, and Mo2Ga2C. A total of six sets of experiments were conducted. The data performance of Examples 1 and 2 in the prior art is shown in Table 1. Table 1 Performance data of Mxenes materials prepared in Examples 1 and 2

[0057] The method for preparing MXenes materials in this invention is simple to operate, improves yield, and reduces cost. As shown in Table 1, the prepared MXenes materials have good antioxidant properties, etching yield, etching time, exfoliation yield, and nanosheet size. They also have good chemical stability and electrochemical performance, highly tunable surface end groups and dielectric properties, and have a wide range of applications.

[0058] In addition to the embodiments described above, the present invention may have other implementations. All technical solutions formed by equivalent substitution or equivalent transformation fall within the protection scope claimed by the present invention.

Claims

1. A method for preparing Mxenes by high-temperature in-situ etching using organic salts, characterized in that, Specifically, the following steps are included: Step S1: Mix the MAX phase precursor material and the organic Lewis acid salt according to the specified ratio, and grind the mixture to below 200 mesh using a mortar and pestle; Step S2: Place the ground mixed raw materials from step S1 into a corundum crucible, heat it to the point of melting in a controllable tube furnace protected by inert gas, hold it at that temperature for a certain period of time, and then cool it down. Step S3: Remove impurities from the etching product obtained in step S2 by water washing and ultrasonic centrifugation to obtain pure MXenes material.

2. The method for preparing MXenes by high-temperature in-situ etching with organic salts according to claim 1, characterized in that: In step S1, the organic Lewis acid salt is a trifluoromethanesulfonate, which includes one or more combinations of LiCF3SO3, NaCF3SO3, KCF3SO3, Mg(CF3SO3)2, Cu(CF3SO3)2, Zn(CF3SO3)2, Fe(CF3SO3)3, Ni(CF3SO3)2, Co(CF3SO3)2, Mn(CF3SO3)2, and AgCF3SO3.

3. The method for preparing MXenes by high-temperature in-situ etching with organic salts according to claim 1, characterized in that: The MAX phase precursor material in step S1 includes one or more combinations of Ti3AlC2, Ti3SiC2, Ti2AlC, Ti2AlN, Ti4AlN3, Ti2GaC, V2AlC, V2GaC, Cr2GaN, Cr2AlC, Sc2AlC, Zr2AlC, Zr2SnC, Nb2AlC, Nb4AlC3, Mo2AlC, Mo2GaN, Hf2AlC, Hf2AlN, Ta3AlC2, and Ta4AlC3.

4. The method for preparing MXenes by high-temperature in-situ etching with organic salts according to claim 2, characterized in that: In step S1, the molar ratio of Cu(CF3SO3)2 to MAX phase precursor material is 4:1, and the molar ratio of any one of the components LiCF3SO3, NaCF3SO3, KCF3SO3, Mg(CF3SO3)2, Zn(CF3SO3)2, Fe(CF3SO3)3, Ni(CF3SO3)2, Co(CF3SO3)2, Mn(CF3SO3)2, and AgCF3SO3 to the MAX phase precursor material is 6:

1.

5. The method for preparing MXenes by high-temperature in-situ etching with organic salts according to claim 1, characterized in that: In step S2, the inert gas is argon, and the gas flow rate is 50 mL / min.

6. The method for preparing MXenes by high-temperature in-situ etching with organic salts according to claim 1, characterized in that: In step S2, the controllable tube furnace is heated to 700°C at a rate of 5°C / min and held at that temperature for 6 hours. Then, the temperature control program is turned off, and the furnace is cooled to room temperature under argon protection.

7. The method for preparing MXenes by high-temperature in-situ etching with organic salts according to claim 1, characterized in that: The etching product is a mixture of MXenes and byproducts, the byproducts being AlF3 and metal sulfides.

8. The method for preparing MXenes by high-temperature in-situ etching with organic salts according to claim 1, characterized in that: The prepared MXenes material contains 1.0-99.9 wt% MXenes. After removing impurities in step S3, the MXenes material is vacuum-assisted dried to make the MXenes material into a uniform powder with a particle size between 1-100 μm.

9. An MXenes material, obtained by the high-temperature in-situ etching method using organic salts as described in claim 1.

10. The application of the MXenes material as described in claim 9 in electrochemical energy storage electrode materials, supercapacitor materials, electromagnetic absorption and shielding materials, infrared absorption and shielding materials, and photoelectrocatalysis.

Images