An electrochemical method for precision etching of MXene materials from molten salts

Abstract

The application relates to an electrochemical method for preparing MXene material through precise etching of a molten salt, and comprises the following steps: S1, uniformly mixing MAX powder and polyvinyl butyral, pressing into a thin sheet, embedding the thin sheet into a graphite rod to form a MAX working electrode; S2, heating a chloride salt to be molten in a sealed inert environment to obtain a molten salt, and performing a pre-electrolysis purification treatment; S3, placing the MAX working electrode obtained in the step S1 into the molten salt after the pre-electrolysis purification treatment in the step S2, adding a counter electrode and a reference electrode to form a three-electrode system, setting a constant voltage to perform electrochemical etching, stopping electrolysis after the etching is completed, and obtaining an electrolysis product from an anode; and S4, taking out the electrolysis product obtained in the step S3, washing the electrolysis product through centrifugation for multiple times, taking black upper suspension, and performing freeze-drying to obtain an end group modified MXene product, namely a target product. Compared with the prior art, the application can accurately prepare MXene materials with different end groups, the surface end groups are controllable, the types are rich, and the method is simple and clean.

Description

Technical Field

[0001] This invention relates to the field of two-dimensional metal carbide preparation, and in particular to an electrochemical method for preparing MXene materials by precise etching with molten salt. Background Technology

[0002] Due to environmental concerns and the depletion of fossil fuels, the efficient use of renewable and sustainable energy is rapidly increasing. Novel two-dimensional (2D) transition metal carbides or nitrides (MXenes) have attracted widespread attention in recent years as excellent candidate materials for energy conversion and storage applications. MXenes can be represented as M... n+1 XT x (n = 1 to 4), where M represents a transition metal element, X represents carbon and / or nitrogen, and T represents... x These represent surface terminal groups derived from etchants and solutions, typically -O, -F, and -OH.

[0003] Unlike the surfaces of other two-dimensional materials such as graphene and transition metal dihalides, the T in MXene x Chemical modification can significantly impact the stability, electronic structure, and physicochemical properties of MXenes. For example, mainstream etching methods using wet chemical processes, including hydrofluoric acid or fluorides (LiF / HCl, NH4HF2) and fluorine-containing ionic liquids, often introduce -F end groups, negatively affecting certain aspects of MXene performance. Furthermore, the fluorine-containing solutions (HF) in these etchants pose a significant environmental hazard. Using Lewis acidic molten salts (such as CuCl2, CuBr2, and CuI) as etchants, -Cl, -Br, and -I-terminated MXenes can be prepared, which has proven beneficial in many electrochemical applications and is considered advantageous for functional group substitution. However, for subsequent applications and further end-group modification, it is necessary to clean metallic impurities with strong oxidants, followed by hydrothermal treatment or treatment with inorganic molten salts. These steps inevitably oxidize the MXene and introduce -O end groups, complicating surface modification. Therefore, developing a simple and environmentally friendly process for preparing MXenes with controllable end groups is highly significant.

[0004] Patent publication number CN107177857A discloses a method for preparing micro / nanoporous multilayer carbon-based materials by electrochemical synthesis and reconstruction of MAX phases. This method integrates molten salt electrochemical reduction with electrochemical assisted etching technology for the first time, achieving the direct preparation of nanoporous multilayer carbon-based materials. The method utilizes metal oxides M... x O y A x O y Using carbon powder as the initial raw material, first mix the uniformly blended metal oxide M x Oy A x O y A porous cathode was fabricated by pressing a mixture of carbon powder and carbon powder. An electrode with a yttrium-stabilized zirconia oxygen-permeable membrane was assembled as the anode, analytical grade anhydrous CaCl2 was used as the molten salt electrolyte, and a corundum crucible was used as the electrolytic cell. First, the metal oxide M was reduced by electrochemical molten salt electrolysis. x O y A x O y A micro / nano ternary carbide MAX phase is synthesized by mixing silica powder and carbon powder. Then, using the obtained ternary carbide MAX phase as the anode and a graphite carbon rod as the cathode, a porous nano-metal carbide or layered porous carbon material is selectively and directly prepared using an electrochemical etching method. Patent publication number CN107119283A discloses a method for preparing mesoporous carbon nanowire materials, characterized by integrating molten salt electrochemical reduction with electrochemically assisted etching technology to achieve direct preparation of mesoporous carbon nanowire materials. Using silica powder and carbon powder as initial raw materials, a uniformly mixed silica / carbon powder mixture is first pressed into a porous electrode. A yttrium oxide-stabilized zirconia oxygen-permeable membrane tube is used as the anode, analytical grade anhydrous CaCl2 as the molten salt electrolyte, and a corundum crucible as the electrolytic cell. First, silica / carbon powder is reduced electrochemically by molten salt to synthesize silicon carbide nanowires. Then, using the obtained silicon carbide nanowires as the anode and a graphite carbon rod as the cathode, a mesoporous carbon nanowire material is directly prepared using an electrochemical etching method. However, the two methods mentioned above differ in their technical fields and principles in the preparation of nano-carbon materials. They involve electrochemical molten salt electrolysis to deoxidize and reduce metal oxides, without involving precise etching of molten salt or structural transformation. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the existing technology by providing an electrochemical method for precisely etching MXene materials with molten salt, which can accurately prepare MXene materials with different end groups, and the functional groups are controllable, diverse, and the method is simple and clean.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] In one aspect, the present invention provides an electrochemical method for precisely etching MXene materials using molten salt, comprising the following steps:

[0008] S1: MAX powder is uniformly mixed with polyvinyl butyral, pressed into a thin sheet, and then embedded in a graphite rod to form the MAX working electrode.

[0009] S2: The chloride salt is heated to melt in a sealed inert environment to obtain molten salt, which is then subjected to pre-electrolytic purification treatment;

[0010] S3: Place the MAX working electrode obtained in step S1 into the molten salt after pre-electrolysis purification in step S2, and add the counter electrode and reference electrode to form a three-electrode system. Set a constant voltage to perform electrochemical etching. After etching is completed, stop electrolysis and obtain the electrolysis product from the anode.

[0011] S4: Take out the electrolysis product obtained in step S3, centrifuge and wash it multiple times, take the upper black suspension, freeze dry it to obtain the end-group modified MXene product, i.e. the target product.

[0012] Furthermore, in step S1, MAX is a general formula M n+1 AX n A ternary layered carbide, where M is a transition metal, A is a main group element, and X is carbon (C) or nitrogen (N), n = 1, 2, 3. Its crystal structure consists of a single M... n+1 X n It is composed of alternating layers of sheets and a single layer of A atomic planes. The MAX includes one or more of the following: titanium aluminum carbon (Ti3AlC2), titanium silicon carbide (Ti3SiC2), titanium aluminum carbide (Ti2AlC), vanadium aluminum carbide (V2AlC), niobium aluminum carbide (Nb2AlC), and titanium aluminum nitride (Ti2AlN).

[0013] Further, in step S1, the mass ratio of the MAX powder to polyvinyl butyral is (90-99):(1-10).

[0014] Further, in step S1, the diameter of the sheet is 6-15 mm and the thickness is 1.5-3 mm, which is set according to the die for pressing the sheet. The graphite rod has a slot, and the sheet is placed in the slot.

[0015] Further, in step S2, the chloride includes any two or three combinations of anhydrous lithium chloride (LiCl), sodium chloride (NaCl), potassium chloride (KCl), and calcium chloride (CaCl2).

[0016] Furthermore, the mass ratio of the chloride to the MAX is (100-120):1, and the chloride serves as an electrolyte for the electrolysis of the electrode.

[0017] Furthermore, in step S2, the heating temperature is 450–650°C.

[0018] Further, in step S2, the pre-electrolysis purification process is as follows: insert two graphite electrodes into the molten salt for pre-electrolysis for 2 to 12 hours.

[0019] Further, in step S3, any one of the following powders, lithium nitride (Li2N), lithium oxide (Li2O), lithium sulfide (Li2S), lithium selenide (Li2Se), and lithium telluride (Li2Te), is added to the molten salt after electrolysis has stopped. After reacting for 4 to 12 hours, the MAX working electrode is removed. The molar ratio of the amount of powder added to MAX is (0.8 to 1.2):1.

[0020] Furthermore, in step S2, the inert environment is obtained by continuously introducing nitrogen (N2) and argon (Ar).

[0021] Further, in step S3, the counter electrode is a graphite electrode, the reference electrode is a graphite electrode or an Ag / AgCl electrode, the constant voltage is 0.2 to 0.8 V, and the etching time is 12 to 24 h.

[0022] Furthermore, in step S4, the centrifugation speed is 3000-5000 rpm, the washing liquid used is deionized water, the freeze-drying temperature is -80 to -40°C, and the time is 12-48 hours.

[0023] Further, in step S4, the end-group modified compounds include calcium nitride (Ca3N2), nitrous oxide (N2O), potassium oxide (K2O), sodium sulfide (Na2S), ferrous sulfide (FeS), potassium sulfide (K2S), sodium selenide (Na2Se), and potassium selenide (K2Se).

[0024] In another aspect, the present invention also provides an Mxene, which is prepared by the above-described electrochemical method for preparing MXene materials by precise etching with molten salt.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] (1) This invention uses the cleanest electrons as the etching agent, which is clean and environmentally friendly. The redox reaction is carried out at the anode and cathode respectively, so there are no other metal impurities in the MXene etched at the anode. The mechanism of electrochemical etching is as follows: During the etching process, the potential is selectively controlled to oxidize and remove the A-site elements in the MAX phase (such as the oxidation etching of Al in Ti3AlC2). Due to the removal of the intermediate layer elements, the MAX phase morphology is transformed into a melodica shape.

[0027] (2) This invention utilizes a wide variety of molten salts, enabling one-step modification of MXene surface end groups, such as -N, -O, -S, -Se, and -Te, thus avoiding oxidation while enriching the variety of MXenes. The purpose of adding small amounts of Li3N and Li2O salts to the molten salt is to allow them to react with MXene (Ti3C2T). x T xThis invention involves nucleophilic substitution reactions of MXenes (with end groups) to obtain MXenes with different end groups. In existing technologies, end group substitution typically involves first preparing MXenes using other methods such as HF etching or Lewis acid etching, and then reacting them using the aforementioned methods to obtain MXenes with different end groups. However, MXenes prepared using other chemical etching methods (HF, HCl / HF) are inevitably oxidized in air or during post-processing, resulting in uneven end group substitution. This invention, however, achieves MXene etching and end group modification in one step through electrochemical etching in molten salt and synergistic end group substitution, with the addition of salts such as Li3N, Li2O, and Li2S as modifiers. This avoids oxidation and enriches the variety of MXenes. Furthermore, the molten salt can be recycled for a long period, ensuring no waste liquid is generated during the entire reaction. Attached Figure Description

[0028] Figure 1 The etching product Ti3C2Cl shown in Example 1 x -MXene's XRD pattern;

[0029] Figure 2 The etching product Ti3C2Cl shown in Example 1 x - SEM image of MXene;

[0030] Figure 3 The etching product Ti3C2Cl shown in Example 1 x -MXene's EDS plot;

[0031] Figure 4 The etching product Ti3C2Cl shown in Example 2 x -MXene's XRD pattern;

[0032] Figure 5 The etching product Ti3C2Cl shown in Example 2 x - SEM image of MXene;

[0033] Figure 6 The etching product Ti3C2Cl shown in Example 2 x -MXene's EDS plot;

[0034] Figure 7 The etching product Ti3C2S shown in Example 3 x - SEM image of MXene;

[0035] Figure 8 The etching product Ti3C2S shown in Example 3 x -MXene's EDS plot;

[0036] Figure 9The etching product Ti3C2Se shown in Example 4 x - SEM image of MXene;

[0037] Figure 10 The etching product Ti3C2Se shown in Example 4 x -MXene's EDS plot;

[0038] Figure 11 The XRD patterns of the product shown in Comparative Example 1 and Ti3AlC2 before the reaction are shown.

[0039] Figure 12 The XRD patterns of the product shown in Comparative Example 1 and Ti3SiC2 before the reaction are shown. Detailed Implementation

[0040] 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 solution 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 creative effort are within the scope of protection of this application.

[0041] Unless otherwise specified, the reagents, methods, instruments and equipment used in this invention are conventional reagents, methods, instruments and equipment in the art.

[0042] In the following embodiments, Ti3AlC2 was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., CAS No. T302678, 98%, 200 mesh; Ti3SiC2 was purchased from YiYi Technology Co., Ltd., CAS No. 12202-82-3, 200 mesh; polyvinyl butyral was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., CAS No. P294391; the programmable pit furnace was purchased from Shanghai Yuzhi Technology Co., Ltd., model YJL-1412; the graphite electrode was purchased from Tianjin Zhongnuo Carbon Co., Ltd., diameter 4-12mm, purity spectrally pure; the corundum tube was purchased from Meichen Electric Heating Instrument Co., Ltd., corundum 95 material, diameter 8mm; the silver electrode wire was purchased from Kunshan Guangjiayuan New Material Co., Ltd., diameter 1.5mm, length 0.5m.

[0043] The Ag / AgCl electrode was prepared in the laboratory. The preparation process is as follows: (1) Take an 8mm diameter corundum tube and polish the sealed end of the corundum tube to transparency using 800 mesh, 1000 mesh, 1500 mesh and 2000 mesh sandpaper respectively. Then rinse with ethanol and dry for later use; (2) Weigh 1g of anhydrous LiCl-KCl (mass 1:1) eutectic salt and grind it together with 0.02g of AgCl into powder to obtain LiCl-KCl-AgCl powder for later use; (3) Take a 1.5mm diameter silver electrode wire, place one end of it at the bottom of the corundum tube, and lead the other end out from the opening of the corundum tube; (4) Slowly add the ground LiCl-KCl-AgCl powder into the corundum tube, and then seal and fix it with high temperature tape to obtain the Ag / AgCl electrode, which is used as a reference electrode.

[0044] Example 1

[0045] 0.95g of Ti3AlC2 powder with a particle size of 200 mesh was uniformly mixed with 0.05g of polyvinyl butyral (mass ratio 95:5) and pressed into a sheet with a diameter of 15mm and a thickness of 3mm using a tablet press. The sheet was then embedded into a graphite rod with a slot to form the MAX working electrode. 100g of anhydrous LiCl and anhydrous KCl were mixed in a molar ratio of 1:1 and placed in an alumina crucible. The crucible was then placed in a sealable quartz tube and heated to 500℃ in a programmable well furnace with Ar continuously introduced to melt the LiCl-KCl salt. Two graphite electrodes were then inserted into the molten salt for pre-electrolytic purification for 12h. The MAX working electrode was placed in a pre-electrolytically purified molten salt. A graphite electrode was selected as the counter electrode, and an Ag / AgCl electrode as the reference electrode, also added to the pre-electrolytically purified molten salt to form a three-electrode system. Electrochemical etching was performed at a constant potential of 0.4V, and electrolysis was stopped after 24 hours. The electrolytic product obtained from the MAX working electrode was immersed in deionized water, repeatedly centrifuged and washed at 4000 rpm, and the supernatant black suspension was collected and freeze-dried at -60℃ to obtain the MXene product Ti3C2Cl. x -MXene, its phase X-ray energy dispersive spectroscopy (XRD) pattern, scanning electron microscopy (SEM) image, and scanning electron microscopy energy dispersive spectroscopy (EDS) pattern are as follows: Figures 1-3 As shown in the XRD pattern, after electrochemical etching, the (002) and (004) peaks of Ti3AlC2 powder shifted to the left, and the peaks around 40° basically disappeared, indicating that MXene was successfully prepared. Furthermore, during the electrochemical etching process, Al elements in Ti3AlC2 were selectively etched, and Cl in the molten salt was removed. - It was introduced into both ends of Ti3C2 and combined, thus obtaining a two-dimensional mezzanine-shaped Ti3C2Cl x-MXene, and the corresponding results are shown in the scanning electron microscope and EDS spectra.

[0046] Example 2

[0047] 0.95g of Ti3SiC2 powder with a particle size of 200 mesh was uniformly mixed with 0.05g of polyvinyl butyral (mass ratio 95:5) and pressed into a sheet with a diameter of 15mm and a thickness of 1.5mm using a tablet press. The sheet was then embedded into a graphite rod with a slot to form the MAX working electrode. 100g of anhydrous LiCl and anhydrous CaCl2 were mixed in a molar ratio of 1:1 and placed in an alumina crucible. The crucible was then placed in a sealable quartz tube and heated to 650℃ in a programmable well furnace with Ar continuously introduced to melt the LiCl-CaCl2 salt. Two graphite electrodes were then inserted into the molten salt for pre-electrolytic purification treatment for 12h. The MAX working electrode was placed in the pre-electrolytically purified molten salt. A graphite electrode was selected as the counter electrode, and an Ag / AgCl electrode as the reference electrode, also added to the pre-electrolytically purified molten salt to form a three-electrode system. Electrochemical etching was performed at a constant potential of 0.55V, and electrolysis was stopped after 24 hours of etching. The electrolytic product obtained from the MAX working electrode was immersed in deionized water, and after repeated centrifugation and washing at 4000 rpm, the supernatant black suspension was collected and freeze-dried at -60℃ to obtain the MXene product Ti3C2Cl. x -MXene, its phase XRD pattern, SEM image and EDS pattern are as follows: Figures 4-6 As shown, XRD reveals that the characteristic peaks of Ti3SiC2 basically disappeared after electrochemical etching, leaving only Ti3C2Cl. x -MXene characteristic peaks. Additionally, during the electrochemical etching process of Ti3SiC2, Si elements are selectively etched, and Cl in the molten salt... - It was introduced into both ends of Ti3C2 and combined, thus obtaining a two-dimensional mezzanine-shaped Ti3C2Cl x -MXene, and the corresponding results are shown in the scanning electron microscope and EDS spectra.

[0048] Example 3

[0049] 0.95g of Ti3AlC2 powder with a particle size of 300 mesh was uniformly mixed with 0.05g of polyvinyl butyral (95:5) and pressed into a sheet with a diameter of 15mm and a thickness of 1.5mm using a tablet press. The sheet was then embedded into a graphite rod with a slot to form the MAX working electrode. 60g of anhydrous LiCl and anhydrous KCl were mixed in a molar ratio of 1:1 and placed in an alumina crucible. This crucible was then placed in a sealable quartz tube and heated to 550℃ in a programmable well furnace under continuous N2 flow to melt the LiCl-KCl salt, obtaining a molten salt. Two graphite electrodes were then inserted into the molten salt for pre-electrolytic purification for 12 hours. The MAX working electrode was placed in the pre-electrolytically purified molten salt. A graphite electrode was selected as the counter electrode, and an Ag / AgCl electrode as the reference electrode, also added to the pre-electrolytically purified molten salt to form a three-electrode system. Electrochemical etching was performed at a constant potential of 0.35V, and electrolysis was stopped after 24 hours of etching. 0.5g of Li₂S powder was added to the stopped molten LiCl-KCl salt through a quartz funnel. Li₂S acts as a solute, dissolving in the molten salt to form S. 2- Anions, and Ti3C2Cl prepared by electrolithography x The Cl end group in MXene undergoes nucleophilic substitution to form Ti3C2S. x After reacting with MXene for 8 hours, the anode was removed, and the electrolytic product obtained from the anode was soaked in deionized water. After repeated centrifugation and washing at 4000 rpm, the upper black suspension was collected and freeze-dried at -60℃ to obtain the MXene product Ti3C2S. x Its phase SEM images and EDS spectra are as follows: Figure 7 , 8 As shown, after electrochemical etching, the intermediate Al atomic layer is selectively etched, and the Cl in the molten salt... - It is introduced and bonded to both ends of Ti3C2, thus the morphology is a classic two-dimensional melodica-shaped Ti3C2Cl x Because Li2S was subsequently added to the molten salt, Ti3C2Cl x The Cl in MXene was replaced, thus ultimately yielding Ti3C2S. x -MXene.

[0050] Example 4

[0051] 0.6 g of Ti3AlC2 powder with a particle size of 300 mesh was uniformly mixed with 0.03 g of polyvinyl butyral (mass ratio 90:7.5) and pressed into a sheet with a diameter of 15 mm and a thickness of 1.8 mm using a tablet press. The sheet was then embedded into a graphite rod with a slot to form the MAX working electrode. 100 g of anhydrous LiCl and anhydrous KCl were mixed in a molar ratio of 1:1 and placed in an alumina crucible. The crucible was then placed in a sealable quartz tube and heated to 550 °C in a programmable well furnace under continuous N2 flow to melt the LiCl-KCl salt, obtaining a molten salt. Two graphite electrodes were then inserted into the molten salt for pre-electrolytic purification treatment for 12 h. The MAX working electrode was placed in the pre-electrolytically purified molten salt. A graphite electrode was selected as the counter electrode, and an Ag / AgCl electrode as the reference electrode, also added to the pre-electrolytically purified molten salt to form a three-electrode system. Electrochemical etching was performed at a constant potential of 0.4V, and electrolysis was stopped after 24 hours of etching. 0.6g of Li₂Se powder was added to the stopped molten LiCl-KCl salt through a quartz funnel. Li₂Se acts as a solute, dissolving in the molten salt to form S. 2- Anions, and Ti3C2Cl prepared by electrolithography x The Cl end group in MXene undergoes nucleophilic substitution to form Ti3C2Se. x After reacting with MXene for 8 hours, the anode was removed, and the electrolytic product obtained from the anode was immersed in deionized water. After repeated centrifugation and washing at 4000 rpm, the upper black suspension was collected and freeze-dried at -60℃ to obtain the MXene product Ti3C2Se. x Its phase SEM images and EDS spectra are as follows: Figure 9 , 10 As shown, after electrochemical etching, the intermediate Al atomic layer is selectively etched, and the Cl in the molten salt... - It is introduced and bonded to both ends of Ti3C2, thus the morphology is a classic two-dimensional mezzanine-shaped Ti3C2Cl x Because Li2Se was subsequently added to the molten salt, Ti3C2Cl x The Cl in -MXene was replaced, thus ultimately yielding Ti3C2Se. x -MXene.

[0052] Example 5

[0053] Compared with Example 1, most of them are the same, except that the mass of the MAX powder and polyvinyl butyral is adjusted to 0.9g and 0.1g respectively (mass ratio 90:10).

[0054] Example 6

[0055] Compared with Example 1, most of them are the same, except that the mass of the MAX powder and polyvinyl butyral is adjusted to 0.99g and 0.01g respectively (mass ratio 99:1).

[0056] Example 7

[0057] Compared to Example 1, most of the results are the same, except that a programmable well furnace is used to heat the LiCl-KCl salt to 450°C while Ar is continuously introduced, so as to melt the LiCl-KCl salt and obtain molten salt.

[0058] Example 8

[0059] Compared to Example 1, most of them are the same, except that the constant voltage is adjusted to 0.2V.

[0060] Example 9

[0061] Compared to Example 1, most of them are the same, except that the constant voltage is adjusted to 0.8V.

[0062] Comparative Example 1

[0063] 0.95 g of Ti3AlC2 powder with a particle size of 200 mesh was uniformly mixed with 0.05 g of polyvinyl butyral (mass ratio 95:5) and then pressed into thin sheets with a diameter of 15 mm and a thickness of 3 mm using a tablet press. The sheets were placed in a 50 mm diameter corundum crucible. 100 g of anhydrous LiCl and anhydrous KCl were mixed in a 1:1 molar ratio and added to the corundum crucible. The mixture was then placed in a sealable quartz tube and heated to 600 °C in a programmable well furnace under continuous Ar flow to melt the LiCl-KCl salt. The reaction was continued for 24 h. After deionization soaking, the sheets were removed, and their corresponding XRD patterns are shown below. Figure 11 As shown. Obviously, without electrolysis, Ti3AlC2 immersed only in molten salt will not be etched, and the XRD phases before and after the reaction are basically the same.

[0064] Comparative Example 2

[0065] 0.95 g of Ti3SiC2 powder with a particle size of 200 mesh was uniformly mixed with 0.05 g of polyvinyl butyral (mass ratio 95:5) and then pressed into thin sheets with a diameter of 15 mm and a thickness of 3 mm using a tablet press. The sheets were placed in a 50 mm diameter corundum crucible. 100 g of anhydrous NaCl and anhydrous CaCl2 were mixed in a 1:1 molar ratio and added to the corundum crucible. The crucible was then placed in a sealable quartz tube and heated to 900 °C in a programmable well furnace under continuous Ar flow to melt the NaCl-CaCl2 salt. The reaction was continued for 24 h. After deionization soaking, the sheets were removed, and their corresponding XRD patterns are shown below. Figure 12As shown. Obviously, without electrolysis, Ti3SiC2 immersed only in molten salt will not be etched, and the XRD phases before and after the reaction are basically the same.

[0066] Although the present invention has been described in detail above with general descriptions, specific embodiments, and experiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. An electrochemical method for the precision lithography of MXene materials from molten salts, characterized in that, Includes the following steps: S1: Mix MAX powder with polyvinyl butyral evenly, press it into a thin sheet, and embed it into a graphite rod to form the MAX working electrode. S2: The chloride salt is heated to melt in a sealed inert environment to obtain molten salt, which is then subjected to pre-electrolytic purification treatment; S3: Place the MAX working electrode obtained in step S1 into the molten salt after pre-electrolytic purification in step S2, and add a counter electrode and a reference electrode to form a three-electrode system. Set a constant voltage for electrochemical etching. After etching is completed, stop electrolysis. Take any one of the powders of Li2N, Li2O, Li2S, Li2Se and Li2Te and add it to the molten salt after stopping electrolysis. After reacting for a period of time, take out the MAX working electrode and obtain the electrolysis product from the anode. The constant voltage is 0.2~0.8V. S4: Take out the electrolysis product obtained in step S3, centrifuge and wash it multiple times, take the upper black suspension, freeze dry it to obtain the MXene product with end group modification, i.e. the target product, wherein the end group is -Cl, -S or -Se.

2. The electrochemical method for the precision etching of MXene materials from molten salts according to claim 1, wherein, In step S1, the MAX includes one or more of the following: Ti3AlC2, Ti3SiC2, Ti2AlC, V2AlC, Nb2AlC, Gr2AlC, Mo2AlC, MoTiC2, Ta2AlC, and W2AlC.

3. The electrochemical method for the precision etching of MXene materials from molten salts according to claim 1, wherein, In step S1, the mass ratio of the MAX powder to polyvinyl butyral is (90~99):(1~10).

4. The electrochemical method for the precision etching of MXene materials from molten salts according to claim 1, wherein, In step S1, the graphite rod has a slot, and the sheet is placed in the slot.

5. The electrochemical method for preparing MXene materials by precise etching with molten salt according to claim 1, characterized in that, In step S2, the chloride includes any two or three combinations of anhydrous LiCl, NaCl, KCl and CaCl2.

6. The electrochemical method for preparing MXene materials by precise molten salt etching according to claim 1, characterized in that, In step S2, the heating temperature is 450~900℃; The pre-electrolysis purification process is as follows: two graphite electrodes are inserted into molten salt for pre-electrolysis for 2-12 hours.

7. The electrochemical method for preparing MXene materials by precise molten salt etching according to claim 1, characterized in that, In step S3, the molar ratio of the amount of powder added to MAX is (0.8~1.2):

1.

8. The electrochemical method for preparing MXene materials by precise etching with molten salt according to claim 1, characterized in that, In step S3, the counter electrode is a graphite electrode, and the reference electrode is a graphite electrode or an Ag / AgCl electrode.

9. An MXene material, prepared by an electrochemical method for preparing MXene materials by molten salt precision etching as described in any one of claims 1 to 8.

Images