A method for preparing MXene materials by mechanical exfoliation

Abstract

The present invention discloses a method for preparing MXene materials by mechanical exfoliation, comprising the following steps: preparing an MXene suspension; performing ultrasonic exfoliation on the MXene suspension; performing centrifugation on the ultrasonically exfoliated MXene suspension to obtain an MXene dispersion; performing freeze-drying on the MXene dispersion to obtain MXene two-dimensional materials; grinding the MXene two-dimensional materials; performing ball milling on the ground MXene two-dimensional materials; and performing freeze-drying on the ball-milled MXene two-dimensional materials to obtain mechanically exfoliated MXene materials. By means of high-speed ball milling technology, the present invention significantly refines MXene grains and greatly improves the powder activity, such that the prepared novel MXene materials have better capacitance performance.

Description

Technical Field

[0001] The present invention relates to the technical field of nanomaterials, and in particular to a method for preparing MXene materials by mechanical exfoliation. Background Art

[0002] MXene is a newly emerging two-dimensional material similar to graphene in recent years. In 2011, the Gogotsi team synthesized transition metal carbides / nitrides MXene using hydrofluoric acid (HF), providing a new research direction for researchers in various fields.

[0003] MXene is usually prepared by selectively etching the A layer from the Mn+1AXn phase. The structure of the ternary MAX phase can be described as a two-dimensional Mn+1AXn with a sublattice interleaved by the A layer, where M is an early transition metal, A is an element of the third or fourth main group, and X is C or / and N. MAX is a layered structure material with a hexagonal layered structure, composed of alternating MX layers and A atomic layers. The M-X bond mainly has a mixed covalent / metallic bond characteristic, and the M-A bond has a metallic bond characteristic with a weak bond strength. In a specific chemical environment, the A atomic layer can be selectively corroded to form a stable M-X layer with terminal functional groups such as -OH, -O, and -F adsorbed on the surface. This two-dimensional material is MXene.

[0004] Ti3C2Tx is a two-dimensional (2D) MXene material with typical two-dimensional layered structure characteristics. It has a large specific surface area, excellent conductivity, good self-lubricating performance, and rich surface groups. However, there are exposed metal atoms on the surface of MXene, which are extremely easy to be oxidized and damage the structure. MXene is also prone to sheet stacking during the preparation and application processes, and there are problems such as weak capacitance performance. Summary of the Invention

[0005] Aiming at the deficiencies of the above prior art, the purpose of the present invention is to provide a method for preparing MXene materials by mechanical exfoliation. Through high-speed ball milling technology, the present invention significantly refines the MXene grains and greatly improves the powder activity, making the prepared new MXene material have better capacitance performance.

[0006] To achieve the above purpose, the present invention is realized through the following technical solutions:

[0007] The present invention provides a method for preparing MXene materials by mechanical exfoliation, including the following steps:

[0008] S1: Prepare an MXene suspension;

[0009] S2: Perform ultrasonic exfoliation on the MXene suspension;

[0010] S3: Centrifuge the MXene suspension after ultrasonic delamination to obtain a MXene dispersion;

[0011] S4: Freeze-dry the MXene dispersion to obtain MXene two-dimensional material;

[0012] S5: Grind the MXene two-dimensional material;

[0013] S6: Ball-mill the ground MXene two-dimensional material;

[0014] S7: Freeze-dry the ball-milled MXene two-dimensional material to obtain a mechanically exfoliated MXene material.

[0015] Preferably, in step S1, the MXene powder is etched and intercalated under chemical liquid conditions to obtain a MXene suspension.

[0016] Preferably, the MXene powder is Ti3AlC2 or Ti2SiC.

[0017] Preferably, the chemical liquid is at least one of HF / H2O solution, HCl / fluoride mixture, H2SO4 / fluoride mixture, NH4HF2 / H2O solution, organic base, organic solvent, organic amine salt / H2O solution.

[0018] Preferably, the HCl / fluoride mixture includes at least one of HCl / LiF, HCl / NaF, HCl / KF, HCl / CaF2, the H2SO4 / fluoride mixture includes at least one of H2SO4 / LiF, H2SO4 / NaF, H2SO4 / KF, H2SO4 / CaF2, the organic base includes at least one of TMAOH, TMBOH, choline, hydrazine hydrate, urea, the organic solvent includes at least one of DMSO, DMF, and the organic amine salt / H2O solution includes at least one of isopropylamine aqueous solution, n-butylamine aqueous solution.

[0019] Preferably, in step S2, an ultrasonic cleaner or a cell disruption ultrasonic machine is used to ultrasonically delaminate the MXene suspension, and the ultrasonic power of the ultrasonic delamination is 50 - 1000 W, and the ultrasonic time is 5 - 600 min.

[0020] Preferably, in step S3, the rotation speed of the centrifuge used in the centrifugation process of the suspension is 1000 - 15000 rpm, and the centrifugation time is 5 - 120 min.

[0021] Preferably, in step S5, the MXene two-dimensional material is ground to a particle size of less than 3 mm.

[0022] Preferably, the ball milling medium in step S6 is ethanol, the ball-to-material ratio is (15-40):1, the rotation speed is 600-700 rpm, and the ball milling time is 2-6 hours.

[0023] Preferably, the drying step in step S7 is specifically vacuum freeze drying, the drying temperature is -30 °C, and the drying time is 12 h.

[0024] The beneficial effects of the present invention are as follows:

[0025] The present invention first obtains MXene two-dimensional materials through chemical etching and ultrasonic exfoliation, then grinds the MXene two-dimensional materials to create conditions for the destruction of the crystal structure. Then, based on the high-speed ball milling technology, mechanical impact and local energy accumulation are utilized to significantly refine the MXene grains, greatly improve the activity of the product, improve the particle distribution uniformity and interface bonding ability, and promote solid-state ion diffusion, thereby realizing the preparation of MXene materials.

[0026] The special structure composed of alternating carbon layers and transition metal layers endows MXene with good electrical conductivity and pseudocapacitance characteristics. The MXene material prepared by the method of the present invention has more sufficient contact between the carbon layer and the transition metal layer, a larger contact specific surface area, and more active sites due to the destruction of its crystal structure, which is more conducive to electron transport, and thus has more excellent electrical conductivity and higher capacitance volume. Description of the Drawings

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings of the embodiments will be briefly introduced below.

[0028] Figure 1 is the preparation flow chart of the MXene material prepared by mechanical exfoliation of the present invention;

[0029] Figure 2 is the XRD pattern of the Ti3C2 material prepared in the embodiment of the present invention;

[0030] Figure 3 is the XRD pattern of the Ti3C2 material prepared in the comparative example;

[0031] Figure 4 is the CV diagram of the Ti3C2 material prepared in the embodiment of the present invention. Detailed Embodiments

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0033] As Figure 1 shown, the present invention provides a method for preparing MXene material by mechanical exfoliation, comprising the following steps:

[0034] S1: Etch and intercalate the MXene powder under chemical liquid conditions to obtain a MXene suspension.

[0035] Among them, the MXene powder includes but is not limited to Ti3AlC2, Ti2SiC; the chemical liquid is at least one of HF / H2O solution, HCl / fluoride mixture (including but not limited to HCl / LiF, HCl / NaF, HCl / KF, HCl / CaF2), H2SO4 / fluoride mixture (including but not limited to H2SO4 / LiF, H2SO4 / NaF, H2SO4 / KF, H2SO4 / CaF2), NH4HF2 / H2O solution, organic base (including but not limited to TMAOH, TMBOH, choline, hydrazine hydrate, urea), organic solvent (including but not limited to DMSO, DMF), organic amine salt / H2O (including but not limited to isopropylamine aqueous solution, n-butylamine aqueous solution).

[0036] S2: Use an ultrasonic cleaner or a cell crusher ultrasonic machine to ultrasonically exfoliate the MXene suspension. The ultrasonic power of the ultrasonic exfoliation is 50 - 1000W, and the ultrasonic time is 5 - 600min.

[0037] S3: Centrifuge the ultrasonically exfoliated MXene suspension to obtain a MXene dispersion; among them, the rotation speed of the centrifuge used is 1000 - 15000rpm, and the centrifugation time is 5 - 120min.

[0038] S4: Perform vacuum freeze-drying on the MXene dispersion to obtain monolayer / few-layer MXene two-dimensional material; the freeze-drying temperature is -30°C, and the drying time is 12h.

[0039] S5: Grind the MXene two-dimensional material with a mortar until the particle size is less than 3mm.

[0040] S6: Ball-mill the ground MXene two-dimensional material; among them, the ball-milling medium is ethanol, the ball-to-material ratio is (15 - 40):1, which can be 15:1, 30:1; 40:1, etc., the rotation speed is 600 - 700rpm, for example, it can be 600, 650, 700rpm, and the ball-milling time is 2 - 6 hours, such as 2h, 4h, 6h.

[0041] S7: Perform vacuum freeze-drying on the ball-milled MXene two-dimensional material at a drying temperature of -30°C and a drying time of 12h to obtain the mechanically exfoliated MXene material.

[0042] Compared with other chemical etching methods, ultrasonic exfoliation and ball milling techniques are relatively simple and fast. The MXene suspension obtained after etching / intercalation treatment of the layered MAX phase powder in a chemical environment mainly contains residual MAX particles that have not been completely etched / intercalated and multi-layer MXene nanosheets. Under the action of ultrasonic treatment with a certain intensity, the multi-layer MXene nanosheets delaminate to form single-layer or few-layer MXene; after grinding treatment, the particle size of the single-layer or few-layer MXene becomes smaller, which helps with uniform dispersion in the next step. Then, it is ball milled by a high-speed ball mill, and the MXene grains are further refined by mechanical impact and local energy accumulation. Finally, after freeze-drying, a novel mechanically exfoliated MXene material is obtained.

[0043] The following further elaborates on the technical solutions of the present invention in combination with specific embodiments to clarify the purpose and advantages of the present invention.

[0044] Example 1

[0045] Take 1.0 g of Ti3AlC2 powder and place it in 40 ml of an HF aqueous solution with a mass concentration of 40% and stir and soak it at a constant temperature for 36 h. After centrifugal washing with deionized water, the obtained precipitate is placed in a reaction kettle, dimethyl sulfoxide (DMSO) is added, and then it is placed in a 60 °C vacuum oven for intercalation treatment. After 12 h, a Ti3C2T x suspension is obtained; the Ti3C2T x suspension is ultrasonically treated in ice water for 2 h and then centrifuged in a centrifuge for 5 min to obtain a Ti3C2T x dispersion. Subsequently, the dispersion is freeze-dried at -30 °C for 12 h to obtain Ti3C2 powder; the Ti3C2 powder is poured into a mortar and ground for 30 min to obtain a Ti3C2 mixture with a particle size less than 3 mm; then it is placed in a ball milling tank, grinding balls are added to control the ball-to-material ratio to 30:1, ethanol is added and stirred evenly, and it is ball milled at a speed of 700 rpm for 2 h to obtain a Ti3C2 dispersion. Finally, the dispersion is freeze-dried at -30 °C for 12 h to obtain the novel Ti3C2-2h-30 powder.

[0046] Example 2

[0047] Take 1.0 g of Ti3AlC2 powder and place it in 40 ml of an HF aqueous solution with a mass concentration of 40% and stir and soak it at a constant temperature for 36 h. After centrifugal washing with deionized water, the obtained precipitate is placed in a reaction kettle, dimethyl sulfoxide (DMSO) is added, and then it is placed in a 60 °C vacuum oven for intercalation treatment. After 12 h, a Ti3C2T x suspension is obtained; the Ti3C2T x suspension is ultrasonically treated in ice water for 2 h and then centrifuged in a centrifuge for 5 min to obtain a Ti3C2T xThe dispersion liquid was then freeze-dried at -30°C for 12 h to obtain Ti3C2 powder. The Ti3C2 powder was poured into a mortar and ground for 30 min to obtain Ti3C2 mixture with a particle size less than 3 mm. Subsequently, it was put into a ball mill jar, grinding balls were added, the ball-to-material ratio was controlled at 15:1, ethanol was added and stirred evenly, and ball milling was carried out at a speed of 700 rpm for 2 h to obtain Ti3C2 dispersion liquid. Finally, the dispersion liquid was freeze-dried at -30°C for 12 h to obtain novel Ti3C2-2h-15 powder.

[0048] Example 3

[0049] Take 1.0 g of Ti3AlC2 powder and place it in 40 ml of HF aqueous solution with a mass concentration of 40% and stir and soak it at a constant temperature for 36 h. After centrifugal washing with deionized water, the obtained precipitate was placed in a reaction kettle, dimethyl sulfoxide (DMSO) was added, and then it was placed in a 60°C vacuum oven for intercalation treatment. After 12 h, Ti3C2T x suspension; Ti3C2T x The suspension was ultrasonically treated in ice water for 2 h and then centrifuged in a centrifuge for 5 min to obtain Ti3C2T x dispersion liquid. Then the dispersion liquid was freeze-dried at -30°C for 12 h to obtain Ti3C2 powder. The Ti3C2 powder was poured into a mortar and ground for 30 min to obtain Ti3C2 mixture with a particle size less than 3 mm. Subsequently, it was put into a ball mill jar, grinding balls were added, the ball-to-material ratio was controlled at 30:1, ethanol was added and stirred evenly, and ball milling was carried out at a speed of 700 rpm for 4 h to obtain Ti3C2 dispersion liquid. Finally, the dispersion liquid was freeze-dried at -30°C for 12 h to obtain novel Ti3C2-4h-30 powder.

[0050] Example 4

[0051] Take 1.0 g of Ti3AlC2 powder and place it in 40 ml of HF aqueous solution with a mass concentration of 40% and stir and soak it at a constant temperature for 36 h. After centrifugal washing with deionized water, the obtained precipitate was placed in a reaction kettle, dimethyl sulfoxide (DMSO) was added, and then it was placed in a 60°C vacuum oven for intercalation treatment. After 12 h, Ti3C2T x suspension; Ti3C2T x The suspension was ultrasonically treated in ice water for 2 h and then centrifuged in a centrifuge for 5 min to obtain Ti3C2T xThe dispersion liquid was then freeze-dried at -30°C for 12 h to obtain Ti3C2 powder; the Ti3C2 powder was poured into a mortar and ground for 30 min to obtain Ti3C2 mixture with a particle size less than 3 mm; then it was put into a ball mill tank, grinding balls were added to control the ball-to-material ratio to 15:1, ethanol was added and stirred evenly, and ball-milled at a speed of 700 rpm for 4 h to obtain Ti3C2 dispersion liquid. Finally, the dispersion liquid was freeze-dried at -30°C for 12 h to obtain novel Ti3C2-4h-15 powder.

[0052] Example 5

[0053] 1.0 g of Ti3AlC2 powder was placed in 40 ml of 40% HF aqueous solution and stirred at a constant temperature for 36 h, centrifugally washed with deionized water, and then the obtained precipitate was placed in a reaction kettle, dimethyl sulfoxide (DMSO) was added, and then placed in a 60°C vacuum oven for intercalation treatment. After 12 h, Ti3C2T x suspension was obtained; the Ti3C2T x suspension was ultrasonically treated in ice water for 2 h and then centrifuged in a centrifuge for 5 min to obtain Ti3C2T x dispersion liquid. Then the dispersion liquid was freeze-dried at -30°C for 12 h to obtain Ti3C2 powder; the Ti3C2 powder was poured into a mortar and ground for 30 min to obtain Ti3C2 mixture with a particle size less than 3 mm; then it was put into a ball mill tank, grinding balls were added to control the ball-to-material ratio to 15:1, ethanol was added and stirred evenly, and ball-milled at a speed of 700 rpm for 6 h to obtain Ti3C2 dispersion liquid. Finally, the dispersion liquid was freeze-dried at -30°C for 12 h to obtain novel Ti3C2-6h-15 powder.

[0054] Comparative example

[0055] 1.0 g of Ti3AlC2 powder was placed in 40 ml of 40% HF aqueous solution and stirred at a constant temperature for 36 h, centrifugally washed with deionized water, and then the obtained precipitate was placed in a reaction kettle, dimethyl sulfoxide (DMSO) was added, and then placed in a 60°C vacuum oven for intercalation treatment. After 12 h, Ti3C2T x suspension was obtained; the Ti3C2T x suspension was ultrasonically treated in ice water for 2 h and then centrifuged in a centrifuge for 5 min to obtain Ti3C2T x dispersion liquid. Then the dispersion liquid was freeze-dried at -30°C for 12 h to obtain Ti3C2 powder.

[0056]

Performance test

[0057] 1. XRD

[0058] Figure 2 and Figure 3XRD patterns of the embodiments and comparative examples of the present invention are shown respectively. It can be seen that compared with the comparative example, the peak positions of the Ti3C2 material after ball milling in the present invention increase, and the position of the highest peak shifts to the left, indicating that its structure has changed, thus proving that the present invention has changed the original structure of Ti3C2 through the novel mechanical exfoliation method.

[0059] 2. CV test

[0060] Figure 4 CV diagrams of the Ti3C2 two-dimensional materials prepared in Examples 2 to 5 of the present invention are shown. The capacitance of the Ti3C2 material is obtained through the capacitance calculation formula. It can be seen that the present invention can prepare MXene materials with excellent capacitance performance through the mechanical exfoliation method. The capacitance of the Ti3C2 material prepared at a ball milling time of 4 h and a ball-to-material ratio of 15:1 is the largest, which is 481.18 F / g.

[0061] It should be noted that the above embodiments all belong to the same inventive concept. The descriptions of the embodiments have their own emphases. For the parts not described in detail in individual embodiments, reference can be made to the descriptions in other embodiments.

[0062] The above embodiments only represent the implementation manners of the present invention. The descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be pointed out that for those of ordinary skill in the art, without departing from the inventive concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A method for preparing MXene materials by mechanical exfoliation, characterized in that, It includes the following steps: S1: Prepare an MXene suspension; S2: Perform ultrasonic exfoliation on the MXene suspension; S3: Centrifuge the ultrasonically exfoliated MXene suspension to obtain an MXene dispersion; S4: Freeze-dry the MXene dispersion to obtain MXene two-dimensional material; S5: Grind the MXene two-dimensional material to a particle size less than 3 mm; S6: Ball-mill the ground MXene two-dimensional material; the ball-milling medium for the ball-milling is ethanol, the ball-to-material ratio is (15 - 40):1, the rotation speed is 600 - 700 rpm, and the ball-milling time is 2 - 6 hours; S7: Freeze-dry the ball-milled MXene two-dimensional material to obtain a mechanically exfoliated MXene material.

2. The method for preparing MXene material by mechanical exfoliation according to claim 1, wherein, In step S1, the MXene powder is etched and intercalated under chemical liquid conditions to obtain an MXene suspension.

3. The method for preparing MXene material by mechanical exfoliation according to claim 2, wherein, The MXene powder is Ti3AlC2 or Ti2SiC.

4. The method for preparing MXene material by mechanical exfoliation according to claim 2, wherein The chemical liquid is at least one of HF / H2O solution, HCl / fluoride mixture, H2SO4 / fluoride mixture, NH4HF2 / H2O solution, organic base, organic solvent, organic amine salt / H2O solution.

5. A method for preparing MXene material by mechanical exfoliation according to claim 4, characterized in that, The HCl / fluoride mixture includes at least one of HCl / LiF, HCl / NaF, HCl / KF, HCl / CaF2, the H2SO4 / fluoride mixture includes at least one of H2SO4 / LiF, H2SO4 / NaF, H2SO4 / KF, H2SO4 / CaF2, the organic base includes at least one of TMAOH, TMBOH, choline, hydrazine hydrate, urea, the organic solvent includes at least one of DMSO, DMF, and the organic amine salt / H2O solution includes at least one of isopropylamine aqueous solution, n-butylamine aqueous solution.

6. A method for preparing MXene material by mechanical exfoliation according to claim 1, characterized in that, In step S2, an ultrasonic cleaner or a cell disruptor ultrasonic machine is used to perform ultrasonic exfoliation on the MXene suspension, and the ultrasonic power for the ultrasonic exfoliation is 50 - 1000 W, and the ultrasonic time is 5 - 600 min.

7. A method for preparing MXene material by mechanical exfoliation according to claim 1, characterized in that, In step S3, the rotation speed of the centrifuge used in the centrifugation step of the suspension is 1000 - 15000 rpm, and the centrifugation time is 5 - 120 min.

8. The method for preparing MXene material by mechanical exfoliation according to claim 1, wherein The freeze-drying step in step S7 is specifically vacuum freeze-drying, the drying temperature is -30 °C, and the drying time is 12 h.

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