Method for preparing MXene two-dimensional material and expanding MAX material by high-energy shock

Abstract

The application belongs to the technical field of two-dimensional materials, and discloses a method for preparing MXene two-dimensional material and expanded MAX material by high-energy electric shock, which comprises the following steps: 1) placing a mother-phase MAX powder in a quartz tube of a high-energy electric shock device, inserting graphite electrodes at both ends of the quartz tube, and compacting the material to make it closely contact with the electrodes; 2) after the capacitor of the high-energy electric shock device is charged, high-energy electric shock is performed, the reaction is completed after a flash phenomenon occurs, and the electric shock is repeated 1-5 times; 3) grinding the product after the electric shock and washing it with acid, washing the product with deionized water until it is neutral, and then standing or centrifuging the product to separate it into layers, so that the MXene two-dimensional material is obtained from the upper layer and the expanded MAX material is obtained from the lower layer. The method can realize the preparation of the MXene two-dimensional material and the expanded MAX material in seconds, has a high reaction speed, has a high etching speed for preparing the MXene two-dimensional material from the expanded MAX material, and reduces the waste of etching raw materials.

Description

Technical Field

[0001] This invention belongs to the field of two-dimensional materials technology, and relates to a method for preparing MXene two-dimensional materials and expanded MAX materials by high-energy electric shock. Background Technology

[0002] Typical two-dimensional layered materials, such as graphene, molybdenum sulfide, and boron nitride, are bonded by interlayer van der Waals forces, allowing for direct exfoliation through ultrasonic vibration and physical cutting. MXene, an emerging two-dimensional material, is obtained by selectively etching the A-layer elements of the MAX phase (where M represents a transition metal such as titanium, niobium, or vanadium, A represents aluminum or silicon, and X represents carbon or nitrogen), followed by ion intercalation and exfoliation. Due to its unique conductivity and elemental diversity, MXene is currently widely used in electrode composites, biomedicine, and electromagnetic shielding.

[0003] Currently, the mainstream preparation methods for MXene (such as Ti3C2T) x The main methods for preparing MXene materials include chemical etching, molten salt etching, and electrochemical etching. Chemical etching uses fluorine-containing solutions or high-concentration alkaline solutions as etchants, requiring a long etching time (24–48 hours) and often resulting in incomplete etching. Molten salt etching uses Lewis acids to etch MXene phase materials; however, due to the susceptibility of MXene to oxidation, it often requires highly airtight equipment, is costly, and easily forms oxidation byproducts. Electrochemical etching uses hydrochloric acid solutions as etchants, often requiring long electrochemical reactions, and may not be feasible for mass production; furthermore, electrolyte loss affects the kinetic efficiency of the etching reaction. Therefore, current methods for preparing MXene materials all suffer from slow selective etching rates and low utilization rates. Summary of the Invention

[0004] This invention addresses the problems of slow selective etching rate and low utilization rate in existing MXene material preparation methods by providing a method for preparing MXene two-dimensional materials and expanded MAX materials using high-energy electrostatic discharge. This method can achieve the preparation of MXene two-dimensional materials and expanded MAX materials in seconds, with a fast reaction speed. The etching speed for preparing MXene two-dimensional materials using expanded MAX materials is fast, reducing the waste of etching materials.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a method for preparing MXene two-dimensional materials and expanded MAX materials by high-energy electric shock, comprising the following steps:

[0007] 1) Place the parent phase MAX powder in the quartz tube of the high-energy electric shock device, insert graphite electrodes at both ends of the quartz tube, and compact the material to make it in close contact with the electrodes.

[0008] 2) After the capacitor of the high-energy electric shock device is fully charged, a high-energy electric shock is performed. The reaction ends after a flash phenomenon occurs. Repeat the electric shock 1 to 5 times.

[0009] 3) The product after electrolysis is ground and washed with acid. After washing with deionized water until neutral, it is allowed to stand or centrifuged to separate into layers. The upper layer is MXene two-dimensional material and the lower layer is expanded MAX material.

[0010] The MAX powder in the technical solution of this invention is selected from titanium aluminum carbide, vanadium aluminum carbide, niobium aluminum carbide, titanium silicon carbide or titanium tin carbide.

[0011] In the technical solution of this invention, the electric shock energy corresponding to 100mg of the parent phase MAX powder is 50-1600J.

[0012] It is worth noting that the high-energy electric shock device used in this invention is a device for regenerating lithium-ion battery electrode materials disclosed in application publication number CN 113258159 A. The dimensions of the quartz tube are adjusted as follows: diameter 4mm, wall thickness 2mm, and length 60mm. Through experiments, this device can be used to perform high-energy electric shock on the parent phase MAX material, obtaining MXene two-dimensional material while unexpectedly obtaining a large amount of expanded MAX material.

[0013] Secondly, the present invention provides a method for preparing MXene two-dimensional materials using the expanded MAX material obtained by the above method, wherein the expanded MAX material is rapidly etched by chemical etching to obtain the MXene two-dimensional material.

[0014] Normal MAX phase requires 40 hours to achieve complete etching when chemically etching to prepare MXene two-dimensional materials, while the expanded MAX obtained by high-energy electric shock in this invention can achieve complete etching in only 15 hours, reducing the etching time by more than 60%.

[0015] The technical features of this invention are as follows:

[0016] 1. The environment in which instantaneous high-energy voltage alters chemical bonds

[0017] Whether using chemical etching or molten salt etching, the goal is to break the MA chemical bonds in the MAX phase, thereby achieving the subsequent separation of two-dimensional sheets. However, a high-voltage DC electric field can damage or even break the chemical bonds in the material. The destruction of MA metallic bonds can be controlled by adjusting the appropriate energy output.

[0018] 2. Instantaneous high temperature alters the interlayer environment of the material.

[0019] Without introducing intercalating agents, instantaneous expansion is achieved within the material through the principle of thermal expansion and contraction. Simultaneously, due to the energy absorption method similar to blackbody radiation during high-energy electric shock, the residual stress inside the material is released during cooling, further weakening the effect of interlayer van der Waals forces. At the same time, the overall heating area is relatively uniform. Due to the drastic temperature change inside the material, some MXenes that have lost the MA bond constraint can break and peel off, while the remaining material generates an expanded MAX material with a larger interlayer spacing.

[0020] 3. The instantaneous high-energy electric shock reaction can be carried out in an atmospheric pressure air environment without the need for an oxygen-free environment protection. In the instantaneous (second-level) reaction process, due to the presence of instantaneous high temperature and high voltage electric field, the material cannot react with oxygen in the air, so there will be no high-temperature oxidation and deterioration of the product.

[0021] 4. Instantaneous high-energy electric shock reduces energy consumption compared to molten salt etching. Since the reaction is completed instantaneously (on the order of seconds) and the heat is mainly transferred in the material in the form of blackbody radiation, this method has ultra-low energy consumption compared to traditional high-temperature reactions, which often require a long time to heat up and hold.

[0022] 5. Expansion MAX has advantages in etching kinetics.

[0023] Through kinetic studies of etching MAX phase materials, conventional etchants often need to etch the A layer little by little from the outside, slowly penetrating and eroding the interior until the van der Waals forces and MA bonds between the layers can no longer support the connection between the layers. However, when etching the expanded MAX, the etchant can penetrate into the interlayer through the larger interlayer and broken edges, increasing the contact between the MAX phase material and the etchant, and can achieve etching behavior that is carried out simultaneously inside and outside, thereby improving etching efficiency.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] 1. Compared with molten salt etching, the method of the present invention has a shorter reaction time, lower energy consumption, and the product is not easily oxidized under high temperature environment, which saves related costs and is easier to industrialize.

[0026] 2. This invention uses instantaneous high-energy electric shock to break the MA chemical bonds. The instantaneous high temperature generated affects the interlayer van der Waals forces. When the internal stress is released, a small amount of MXene is detached from the edge. The remaining MA chemical bonds of the expanded MAX material are also damaged to a certain extent. The larger interlayer spacing is more conducive to the penetration of etchant during subsequent etching.

[0027] 3. The method of the present invention is relatively safe and has a fast reaction speed. Since the Joule heat generated during the high-energy electric shock process is generated inside the material, the overall heating area is relatively uniform.

[0028] 4. This invention can match different MAX materials by adjusting the input energy, which has better utilization prospects and improves the material etching conversion rate, reducing the waste of raw materials during etching. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the material manufacturing process of the present invention.

[0030] Figure 2 The images show SEM images of the MXene two-dimensional material and the expanded MAX material obtained in Example 1.

[0031] Figure 3 The images shown are transmission electron microscope (TEM) and atomic force microscope (AFM) images of the MXene two-dimensional material obtained in Example 1.

[0032] Figure 4 The images show transmission electron microscopy (TEM) images of the expanded MAX phase obtained in Example 1 and the conventional MAX phase material (aluminum carbide).

[0033] Figure 5 This is a transmission electron microscope (TEM) image of the MAX material obtained in Example 2.

[0034] Figure 6 This is a transmission electron microscope (TEM) image of the MAX material obtained in Example 3.

[0035] Figure 7 These are the XRD patterns of the MAX phase materials obtained in Examples 1-3.

[0036] Figure 8 This is a SEM image of the MAX phase material obtained in Example 4.

[0037] Figure 9 This is a SEM image of the MAX phase material obtained in Example 5.

[0038] Figure 10 This is a SEM image of the expanded MAX material of Example 6 after 15 hours of etching.

[0039] Figure 11 The aluminum content in MXene materials obtained by inductively coupled plasma atomic emission testing of the expanded MAX material of Example 6 and the MAX material of Comparative Example 1 at different etching times is shown.

[0040] Figure 12 The XRD patterns are of the MXene materials obtained after etching the expanded MAX material of Example 6 and the MAX material of Comparative Example 1 for 15 hours.

[0041] Figure 13The graph shows the rate and cycle performance of the electrodes prepared from the expanded MAX material of Example 6 (etched for 15 hours) and the MAX material of Comparative Example 1 (etched for 40 hours) as lithium-ion anode materials.

[0042] Figure 14 Cyclic voltammetry curves of electrodes prepared from the expanded MAX material of Example 6 (etched for 15 h) and the MXene material of Comparative Example 1 (etched for 40 h) as lithium-ion anode materials are shown.

[0043] Figure 15 Impedance maps of MXene materials prepared as lithium-ion anode materials, obtained by etching the expanded MAX material for 15 hours in Example 6 and the MAX material for 40 hours in Comparative Example 1. Detailed Implementation

[0044] The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of protection of the present invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the test methods in the following embodiments are conventional methods.

[0045] It is worth noting that the energy required for the reaction during a high-energy electric shock is calculated based on the energy required for the mass of the reactants, using the formula... Set the charging voltage and the number of capacitors. The high-energy electric shock device can select n capacitors to adjust the reaction voltage in series or parallel. When the amount of reactant increases, a larger reactor can be selected for the reaction. Since high temperature can easily cause the MAX phase to decompose and change, in order to prevent the reactor from breaking due to instantaneous high temperature and the occurrence of uncontrollable side reactions, the energy should be controlled below 1600J.

[0046] Example 1

[0047] like Figure 1The diagram shows the material preparation process of this invention. 100 mg of aluminum titanate carbide (Ti3AlC2) was placed into a quartz tube (4 mm in diameter, 2 mm in wall thickness, and 60 mm in length) of a high-energy electric shock device. Conductive graphite rods were inserted into both ends to seal the tube, and the material was compacted using external force to ensure close contact with the electrodes. The quartz tube was placed in a reactor, and both ends were fixed with grooved copper rods. The input voltage was adjusted to 200 V, and five capacitors (Hitachi HCGHA series 400V 5600UF 5600MFD 400VDC) were activated, with an electric shock energy of 560 J. The discharge button was turned on, and a noticeable flash phenomenon occurred during the reaction. After the reaction was completed, the sample was removed, ground, and washed in dilute hydrochloric acid (20 ml, 1 mol / L), followed by washing with deionized water until neutral. Through ultrasonic dispersion and static separation, a small amount of MXene two-dimensional material (7 mg) was obtained in the upper layer, and a large amount of expanded MAX material (72 mg) was obtained in the lower layer.

[0048] Figure 2 SEM images of the MXene two-dimensional material and the expanded MAX material obtained in Example 1. From... Figure 2 It can be seen that the sheet area of ​​the MXene two-dimensional material obtained by this invention is relatively large. Figure 2 -a); The expanded MAX material obtained by this invention has a distinct layered structure and a larger interlayer spacing ( Figure 2 -b).

[0049] Figure 3 These are transmission electron microscope (TEM) and atomic force microscope (AFM) images of the MXene two-dimensional material obtained in Example 1. Figure 3 It can be seen that the MXene two-dimensional material obtained by this invention has relatively complete layers. Figure 3 -a), the sheet thickness is about 5nm ( Figure 3 -b).

[0050] Figure 4 The images show transmission electron microscopy (TEM) images of the expanded MAX phase obtained in Example 1 and the conventional MAX phase material (aluminum carbide). From... Figure 4 It can be seen that the interlayer spacing of the expanded MAX material obtained by this invention is 1.26 nm, which is a significant improvement over the conventional MAX interlayer spacing of 0.93 nm.

[0051] Example 2

[0052] This embodiment is basically the same as embodiment 1, except that the charging voltage is 250V, the number of activated capacitors is 5, and the energy of the high-energy electric shock is 875J.

[0053] Figure 5 This is a transmission electron microscope (TEM) image of the MAX material obtained in Example 2. From... Figure 5It can be seen that the MAX material obtained in Example 2 shows a situation where graphene is loaded with some titanium carbide.

[0054] Example 3

[0055] This embodiment is basically the same as embodiment 1, except that the charging voltage is 240V and the number of activated capacitors is 10, that is, the energy of the high-energy electric shock is 1600J.

[0056] Example 4

[0057] This embodiment is basically the same as embodiment 1, except that the charging voltage is 250V and the number of activated capacitors is 10, that is, the energy of the high-energy electric shock is 1750J.

[0058] Figure 6 This is a transmission electron microscope (TEM) image of the MAX material obtained in Example 4. From... Figure 6 It can be seen that the MAX material obtained in Example 4 underwent severe decomposition and showed a distinct graphene structure.

[0059] Figure 7 These are the XRD patterns of the MAX phase materials obtained in Examples 1-4. From... Figure 7 As can be seen, the proportion of titanium carbide in the MAX phase material obtained when the input voltage is 250V and the electric shock energy is 875J (Example 2) increases; the proportion of titanium carbide in the MAX phase material obtained when the input voltage is 250V and the electric shock energy is 1600J (Example 3) continues to increase, and a graphene structure appears; the MAX phase material obtained when the input voltage is 250V and the electric shock energy is 1750J (Example 4) has almost completely transformed into titanium carbide and a partial graphene structure. Therefore, the electric shock energy for 100mg of aluminum carbide should be controlled below 1600J.

[0060] Example 5

[0061] This embodiment is basically the same as Embodiment 2, except that the aluminum titanate carbide (Ti3AlC2) material is replaced with vanadium aluminum carbide (V2AlC). The upper layer yields MXene two-dimensional material (3 mg), and the lower layer yields a large amount of expanded MAX material (80 mg).

[0062] Figure 8 This is a SEM image of the MAX phase material obtained in Example 5. It can be seen that even after changing the parent phase material, MAX materials with edge expansion can still be obtained.

[0063] Example 6

[0064] This embodiment is basically the same as Embodiment 2, except that the aluminum titanate carbide (Ti3AlC2) material is replaced with niobium aluminum carbide (Nb2AlC). The upper layer yields MXene two-dimensional material (4 mg), and the lower layer yields a large amount of expanded MAX material (85 mg).

[0065] Figure 9 This is a SEM image of the MAX phase material obtained in Example 6. It can be seen that even after changing the parent phase material, MAX materials with edge expansion can still be obtained.

[0066] Example 7

[0067] The expanded MAX material obtained in Example 1 was etched using a conventional chemical etching method. Lithium fluoride (1 g) was added to dilute hydrochloric acid (20 ml, 9 mol / L) and mixed thoroughly in a plastic container. The expanded MAX material was then added and heated and stirred in a 45°C water bath for 5, 10, 15, and 20 hours, respectively. After centrifuging and washing the product until neutral, the precipitate was dispersed in deionized water and ultrasonically dispersed for 30 minutes. Vacuum freeze-drying was then performed to obtain MXene powder (Ti3C2T) corresponding to different etching times. x ).

[0068] Comparative Example 1: Preparation of MXene by Traditional Chemical Etching

[0069] Lithium fluoride (1g) was added to dilute hydrochloric acid (20ml, 9mol / L) and mixed thoroughly in a plastic container. Aluminum carbide (Ti3AlC2, 100mg) was then added and heated in a 45℃ water bath, followed by magnetic stirring for 5, 10, 15, 20, and 40 hours. The resulting solution was centrifuged multiple times until it approached neutral. The precipitate was then dispersed in an aqueous solution and ultrasonically dispersed for 30 minutes, followed by freeze-drying to obtain MXene powder (Ti3C2T) corresponding to different etching times. x ).

[0070] Figure 10 This is a SEM image of the expanded MAX material from Example 7 after 15 hours of etching. It can be seen that the MXene material obtained by etching the expanded MAX material of this invention has a large sheet size, and its rough surface provides more electrochemical active sites.

[0071] Figure 11 The aluminum content in MXene materials obtained by inductively coupled plasma atomic emission testing (ICP-AES) at different etching times is shown for the expanded MAX material of Example 7 and the MAX material of Comparative Example 1. Figure 11 As can be seen from the above, the expanded MAX material obtained by high-energy electric shock in this invention removes aluminum from the material faster during etching, resulting in higher etching efficiency.

[0072] Figure 12The images show the XRD patterns of MXene materials obtained after etching the expanded MAX material of Example 7 and the MAX material of Comparative Example 1 for 15 hours. From... Figure 12 As can be seen from the above, the expanded MAX material obtained by high-energy electric shock in this invention has been completely etched and transformed after 15 hours, while conventional MAX materials have some parts that are not completely etched.

[0073] Take 50 mg each of the MXene materials obtained from etching the expanded MAX material of Example 7 for 15 h and the MAX material of Comparative Example 1 for 40 h, and mix them with the binder polyvinylidene fluoride (PVDF) and conductive carbon black (SuperP) in a ratio of 8:1:1. Prepare a slurry using N-methylpyrrolidone (NMP) as the solvent, stir evenly, coat it onto copper foil, and place it in an oven at 80°C for 10 h. After drying, cut it into circular active material electrodes with a diameter of 12 mm. Assemble a CR2032 button-type lithium-ion half-cell in an argon-filled glove box in the following order: negative electrode shell, active material electrode, separator, lithium sheet, gasket, and spring sheet. Use lithium hexafluorophosphate (LiPF6) as the electrolyte.

[0074] Figure 13 The graph shows the rate and cycle performance of the electrodes prepared from the expanded MAX material of Example 7 (etched for 15 hours) and the MAX material of Comparative Example 1 (etched for 40 hours) as lithium-ion anode materials. Figure 14 Cyclic voltammetry curves of electrodes prepared from the expanded MAX material of Example 7 (etched for 15 h) and the MXene material of Comparative Example 1 (etched for 40 h) as lithium-ion anode materials are shown. Figure 15 Impedance maps of MXene materials prepared as lithium-ion anode materials, obtained by etching the expanded MAX material of Example 7 for 15 hours and the MAX material of Comparative Example 1 for 40 hours. Figure 13-15 As can be seen, the MXene material obtained by the expansion MAX etching of this invention has excellent electrochemical performance, with more lithium ion insertion space and smaller bulk diffusion and solution transport resistance.

[0075] The embodiments described above are merely preferred embodiments of the present invention and are only used to explain the present invention. They are not intended to limit the scope of the present invention. For those skilled in the art, other implementation methods can be easily made by substitution or modification based on the technical content disclosed in this specification. Therefore, all changes and improvements made on the principle of the present invention should be included within the scope of the patent application of the present invention.

Claims

1. A method for preparing MXene two-dimensional materials and expanded MAX materials by high-energy electric shock, characterized in that, Includes the following steps: 1) Place the parent phase MAX powder in the quartz tube of the high-energy electric shock device, insert graphite electrodes at both ends of the quartz tube, and compact the material to make it in close contact with the electrodes; 2) After the capacitor of the high-energy electric shock device is fully charged, a high-energy electric shock is performed. The reaction ends after a flash phenomenon occurs. The electric shock is repeated 1 to 5 times. The electric shock energy corresponding to each 100mg of the parent phase MAX powder is 50 to 1600J. 3) The product after electrolysis is ground and washed with acid. After washing with deionized water until neutral, it is allowed to stand or centrifuged to separate into layers. The upper layer is MXene two-dimensional material and the lower layer is expanded MAX material.

2. The method according to claim 1, characterized in that, The parent phase MAX powder is selected from titanium aluminum carbide, vanadium aluminum carbide, niobium aluminum carbide, titanium silicon carbide or titanium tin carbide.

3. A method for preparing MXene two-dimensional materials using the expanded MAX material obtained by the method according to any one of claims 1 to 2, characterized in that, The expanded MAX material was rapidly etched using a chemical etching method to obtain MXene two-dimensional material.

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