Preparation method of MXene material with adjustable interlayer spacing through microwave-assisted chemical etching

Abstract

The invention discloses a preparation method of an interlayer spacing adjustable MXene material through microwave-assisted chemical etching, and belongs to the technical field of two-dimensional nano material preparation. Key parameters such as etching agent solution concentration, villiaumite ratio and microwave power are adjusted and controlled through a synergistic effect mechanism of a microwave field and chemical etching; the preparation method realizes accurate and controllable interlayer spacing preparation of the MXene material, has the advantages of high reaction speed, high etching efficiency, accurate and adjustable interlayer spacing, wide range and the like, and provides an efficient and reliable preparation method for performance optimization of the MXene material in the fields of energy storage, catalysis, separation membranes, gas sensitivity and the like.

Description

Technical Field

[0001] This invention belongs to the field of two-dimensional nanomaterial preparation technology, and particularly relates to a method for preparing MXene materials with adjustable interlayer spacing through microwave-assisted chemical etching. Background Technology

[0002] MXene materials, as novel two-dimensional transition metal carbides / nitrides, possess significant application value in energy, catalysis, and other fields due to their excellent physicochemical properties. Traditional methods for preparing MXene materials involve etching the MAX phase precursor using conventional heat sources in hydrofluoric acid or fluoride / hydrochloric acid systems. However, this method suffers from low reaction efficiency and limitations in interlayer spacing control, often resulting in inaccuracies. In particular, the use of high-concentration hydrofluoric acid poses safety risks, while subsequent interlayer spacing control processes are often complex and prone to introducing defects. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention proposes a method for preparing MXene materials with adjustable interlayer spacing via microwave-assisted chemical etching. This method enables precise in-situ control of the MXene interlayer spacing while significantly improving reaction efficiency, providing a new solution for the controllable preparation of high-performance MXene materials.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] This invention provides a method for preparing microwave-assisted chemical etching MXene materials with adjustable interlayer spacing, comprising the following steps:

[0006] A homogeneous fluoride salt solution was prepared by mixing fluoride salt with water.

[0007] The homogeneous fluoride salt solution and the dilute hydrochloric acid solution were mixed to obtain the etching system;

[0008] The MAX phase precursor was added to the etching system and a pre-etching reaction was carried out under magnetic stirring.

[0009] The reaction mixture after pre-etching reaction is placed in a microwave synthesis reaction device for etching reaction. After cleaning and drying, the interlayer spacing adjustable MXene material is obtained.

[0010] Microwave-assisted chemical etching technology, by coupling the thermal effect of the microwave field with the controllability of chemical etching, can achieve in-situ precise control of the interlayer spacing of MXene, while significantly improving reaction efficiency, providing a new solution for the controllable preparation of high-performance MXene materials.

[0011] Furthermore, the ratio of the fluoride salt to the dilute hydrochloric acid solution is (0.05-0.2) mol : (20-200) mL;

[0012] The concentration of the dilute hydrochloric acid solution is (3-9) mol / L.

[0013] For example, the preparation process of the dilute hydrochloric acid solution is as follows: the concentrated hydrochloric acid solution is diluted with deionized water and then prepared into a dilute hydrochloric acid solution by magnetic stirring.

[0014] Furthermore, the fluoride salt is selected from at least one of potassium fluoride (KF), lithium fluoride (LiF), sodium fluoride (NaF), and ammonium fluoride (NH4F).

[0015] Furthermore, the ratio of the fluoride salt to the MAX phase precursor is (0.05-0.2) mol: (1-3) g.

[0016] Furthermore, the MAX phase precursor is selected from one of V2AlC, V3AlC2, Cr2AlC, Cr3AlC2, Ti2AlC, Ti3AlC2, Nb2AlC, Nb3AlC4, Ta2AlC, and Ta4AlC3.

[0017] Furthermore, the particle size of the MAX phase precursor is 200-600 mesh.

[0018] Furthermore, the magnetic stirring speed is 350-550 rpm, and the magnetic stirring time is 30-60 min.

[0019] Furthermore, during the etching reaction, the microwave power is 200-800W, the temperature is 100-160℃, and the time is 12-72h; preferably, the microwave power is 600W, the temperature is 140℃, and the time is 12h.

[0020] The present invention also provides an MXene material with adjustable interlayer spacing prepared according to the above method.

[0021] Compared with the prior art, the present invention has the following advantages and technical effects:

[0022] This invention discloses a method for preparing MXene materials with adjustable interlayer spacing through microwave-assisted chemical etching. By controlling key parameters such as etchant concentration, etching time, temperature, fluoride salt ratio, and microwave power through the synergistic mechanism of microwave field and chemical etching, this invention achieves precise and controllable preparation of MXene materials with adjustable interlayer spacing. It has advantages such as fast reaction speed, high etching efficiency, and precise and wide-range adjustable interlayer spacing, providing an efficient and reliable preparation method for optimizing the performance of MXene in energy storage, catalysis, separation membranes, gas sensing and other fields. Attached Figure Description

[0023] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0024] Figure 1 V2CT prepared for some embodiments x Scanning electron microscope images of the materials, where (a) is the V2CT prepared in Example 1. x (b) shows the V2CT prepared in Example 4. x (c) is the V2CT prepared in Example 8. x (d) is the V2CT prepared in Example 13. x (e) is the V2CT prepared in Example 10. x (f) shows the V2CT prepared in Example 9. x ;

[0025] Figure 2 V2CT prepared for Comparative Example 2 x Scanning electron microscope image of the material;

[0026] Figure 3 V2CT prepared for Comparative Example 3 x Scanning electron microscope image of the material;

[0027] Figure 4 The EIS test results are shown for the large-aperture MXene obtained by microwave-assisted chemical etching (microwave hydrothermal) in Example 9 and the MXene prepared by conventional hydrothermal (Comparative Example 1).

[0028] Figure 5 The HER test results are for MXene with large opening size obtained by microwave-assisted chemical etching (microwave hydrothermal) in Example 9 and MXene prepared by conventional hydrothermal (Comparative Example 1). Detailed Implementation

[0029] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0030] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0031] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0032] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0033] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0034] Embodiments of the present invention provide a method for preparing microwave-assisted chemical etching interlayer spacing tunable MXene materials, comprising the following steps:

[0035] (1) Mix fluoride salt with water to prepare a homogeneous fluoride salt solution;

[0036] (2) Mix the homogeneous fluoride salt solution and the dilute hydrochloric acid solution to obtain the etching system;

[0037] (3) Add the MAX phase precursor to the etching system and carry out a pre-etching reaction under magnetic stirring;

[0038] (4) The reaction mixture after pre-etching reaction is placed in a microwave synthesis reaction device for etching reaction. After cleaning and drying, MXene material with adjustable interlayer spacing is obtained.

[0039] The principle of this invention is as follows: Microwave-assisted chemical etching technology, dominated by the polarization effect of coupled microwave fields, combined with the controllability of thermal effects and chemical etching, enables in-situ precise control of MXene interlayer spacing, while significantly improving reaction efficiency, providing a new solution for the controllable preparation of high-performance MXene materials. Compared to existing technologies where the expansion of MXene interlayer spacing mainly relies on ultrasonic exfoliation after etching and does not emphasize precise controllability, this invention uses microwave polarization effect as the dominant mechanism, emphasizing its direct and active control over interlayer ion / molecule intercalation behavior, and synergistically achieving in-situ control with thermal effects and chemical etching. This invention allows for in-situ, active, and precise control of interlayer spacing during the etching process. Furthermore, while focusing on the precise and controllable preparation of interlayer spacing properties, this invention can also rapidly and efficiently prepare MXene.

[0040] In an embodiment of the present invention, the ratio of the amount of fluoride salt in step (1) to the amount of dilute hydrochloric acid solution in step (2) is (0.05-0.2) mol: (20-200) mL; the concentration of the dilute hydrochloric acid solution is (3-9) mol / L.

[0041] The ratio of fluoride salts to dilute hydrochloric acid solution directly affects the amount and concentration of HF generated. Too low a concentration in the etching system leads to incomplete etching, with residual Al blocking interlayer channels, limiting interlayer intercalation, and resulting in small and uneven interlayer spacing. Too high a concentration of dilute hydrochloric acid solution provides more H₂. + H + It readily hydrates to form H3O + H3O + It is an effective interlayer "pillar" that can increase the interlayer spacing, H + Concentration also affects the electric double layer structure and surface charge; high concentrations of fluoride salts provide more cations that can be used for intercalation (such as Li). + This leads to more cations inserting into the interlayer, directly increasing the interlayer spacing. At extremely high etching system concentrations, the high external osmotic pressure may affect the activity and structure of water molecules in the interlayer, and in extreme cases, may even lead to partial dehydration, which is detrimental to ions with large hydration radii (such as Li). + Maintaining a large interlayer spacing. Therefore, there is an optimal concentration range for the etching system. Microwaves accelerate ion diffusion and reactions in high-concentration etching systems, reaching intercalation equilibrium more quickly and utilizing the advantage of more intercalated ions brought about by high concentration more effectively.

[0042] For example, the preparation process of dilute hydrochloric acid solution is as follows: dilute concentrated hydrochloric acid solution (12mol / L) with deionized water and prepare dilute hydrochloric acid solution by magnetic stirring.

[0043] In an embodiment of the present invention, in step (1), the fluoride salt is selected from at least one of potassium fluoride (KF), lithium fluoride (LiF), sodium fluoride (NaF), and ammonium fluoride (NH4F).

[0044] LiF provides Li + With high hydration energy and a large hydration radius, it can form strong interactions with the oxygen-containing end groups (-O, -OH) on the MXene surface, enabling MXene to achieve a larger interlayer spacing. NaF provides Na... + The hydration energy and hydration radius are both at a moderate level, and the interaction with the end groups is weak. Therefore, the interlayer spacing of the resulting MXene is usually smaller than that of Li. + Intercalation system. KF provides K + With low hydration energy and small hydration radius, although its ionic radius is relatively large, it is easier for it to directly insert into narrow interlayer gaps; at the same time, its interaction with end groups is the weakest. Therefore, K +Intercalated MXenes may have the smallest interlayer spacing. Using mixed fluoride salts introduces multiple cation co-intercalation processes, such as NaF / LiF mixed fluoride salts, where Na is used first. + Pre-intercalation was performed to obtain a medium-sized interlayer spacing; subsequently, Li... + Stronger end-group interactions and intercalation capabilities can further increase interlayer spacing.

[0045] In an embodiment of the present invention, in step (1), the ratio of fluoride salt to water is (0.05-0.2) mol: (20-200) mL.

[0046] In an embodiment of the present invention, the ratio of the amount of fluoride salt in step (1) to the amount of MAX phase precursor in step (3) is (0.05-0.2) mol: (1-3) g.

[0047] In an embodiment of the present invention, in step (3), the MAX phase precursor is selected from one of V2AlC, V3AlC2, Cr2AlC, Cr3AlC2, Ti2AlC, Ti3AlC2, Nb2AlC, Nb3AlC4, Ta2AlC and Ta4AlC3.

[0048] In an embodiment of the present invention, in step (3), the particle size of the MAX phase precursor is 200-600 mesh.

[0049] In an embodiment of the present invention, in step (3), the magnetic stirring rate is 350-550 rpm and the magnetic stirring time is 30-60 min.

[0050] In an embodiment of the present invention, in step (4), the microwave power is 200-800W, the temperature is 100-160℃, and the time is 12-72h during the etching reaction; preferably, the microwave power is 600W, the temperature is 140℃, and the time is 12h.

[0051] Insufficient etching time leads to residual Al layers and incomplete opening of interlayer channels. This not only hinders the effective preparation of MXene materials but also impedes cation insertion, resulting in non-MXene materials and smaller interlayer spacing. Therefore, sufficient etching time is crucial not only for the effective preparation of MXene materials but also for the selection of target cations (such as Li). + Na + This is a necessary condition for MXene to fully diffuse and insert into the interlayer, achieving the maximum (or equilibrium) interlayer spacing. However, excessively long etching times can lead to over-etching at the edges of the MXene layers, resulting in increased defect density, altered surface end groups, and compromised layer structure integrity. These structural damages may manifest as interlayer collapse or, in extreme cases, accelerated oxidative degradation of the material.

[0052] Too low an etching temperature severely restricts etching kinetics and cation diffusion, resulting in incomplete Al removal and insufficient opening of interlayer channels. This is detrimental to MXene synthesis. Increasing the etching temperature accelerates etching kinetics and promotes cation diffusion and insertion into the interlayer. However, increasing the temperature weakens cation hydration. For ions with high hydration energy and large hydration radius (such as Li), this is particularly problematic. + High temperatures reduce the effective hydration radius of the material, allowing it to enter previously confined narrow spaces, but at the same time, they also make the interlayer spacing smaller.

[0053] Microwave power affects the process not only through thermal effects (temperature), but its polarization effect can also influence the chemical bond properties and interlayer cation migration of materials. Firstly, the MXene surface end groups (-O, -OH, and -F) and etchants (such as HF / H) influence the process. + Under the influence of a microwave field, bond energies can be weakened, the activation energy of the reaction can be reduced, and etching can be accelerated; secondly, the microwave field can directly act on interlayer cations (Li). + Na + Microwave etching (e.g., [etc.]) enables cations to migrate more rapidly and intercalate more deeply along the direction of the electric field. At the same temperature, microwave etching is more efficient than conventional heating etching and yields larger interlayer spacing. Since different cations respond differently to microwave fields, it can be used to control intercalation selectivity or co-intercalation behavior in mixed salt systems. However, selecting the appropriate microwave power is crucial for achieving successful etching and intercalation. Excessive power can lead to localized overheating, overly vigorous reactions, over-etching, increased defects, and even structural damage, ultimately resulting in interlayer collapse or overall oxidative degradation of the material.

[0054] In an embodiment of the present invention, the cleaning step (4) is as follows: alternately cleaned with anhydrous ethanol and deionized water (anhydrous ethanol / deionized water) until neutral.

[0055] In an embodiment of the present invention, in step (4), the drying temperature is 60-80°C and the drying time is 7-12 hours.

[0056] In an embodiment of the present invention, in step (4), the reaction mixture system after pre-etching reaction is first transferred to a polytetrafluoroethylene high-pressure reactor, and then placed in a microwave synthesis reaction device for etching reaction.

[0057] For example, the microwave synthesis reaction apparatus in step (4) is a microwave reactor.

[0058] In an embodiment of the present invention, the volume of the polytetrafluoroethylene high-pressure reactor is 100-500 mL.

[0059] The present invention also provides an MXene material with adjustable interlayer spacing prepared according to the above method.

[0060] This invention discloses a method for preparing MXene materials with adjustable interlayer spacing via microwave-assisted chemical etching, specifically comprising: (1) preparing a fluoride salt etchant solution of a specific concentration; (2) optimizing the molar concentration of the hydrochloric acid solution; (3) mixing the fluoride salt etchant solution with the hydrochloric acid solution to prepare an etching system, mixing the MAX phase precursor with the etching system and performing a pre-etching reaction; and (4) implementing a controllable etching process in a microwave reactor. This invention, through the synergistic mechanism of microwave field and chemical etching, regulates key parameters such as the etchant solution concentration, fluoride salt ratio, and microwave power, achieving precise and controllable preparation of MXene materials with adjustable interlayer spacing. It possesses advantages such as fast reaction speed, high etching efficiency, and precise and wide-range adjustable interlayer spacing, providing an efficient and reliable preparation method for optimizing the performance of MXene materials in energy storage, catalysis, separation membranes, and gas sensing.

[0061] All raw materials used in the embodiments of this invention were obtained through commercial purchase.

[0062] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0063] The technical solution of the present invention will be further illustrated by the following embodiments.

[0064] Example 1

[0065] This embodiment provides a method for preparing MXene materials with adjustable interlayer spacing via microwave-assisted chemical etching, the steps of which are as follows:

[0066] (1) Preparation of homogeneous etchant solution:

[0067] Accurately weigh 0.05 mol of high-purity lithium fluoride powder (LiF, purity ≥99%), dissolve it in 40 mL of ultrapure water, and continuously disperse it for 30 min under constant magnetic stirring at 350 rpm to obtain a uniform and stable lithium fluoride etchant solution.

[0068] (2) Preparation of acidic etching medium:

[0069] 20 mL of concentrated hydrochloric acid (12 mol / L) was accurately measured using a pipette and added dropwise to 20 mL of ultrapure water. The mixture was stirred evenly for 30 min under constant magnetic stirring at 350 rpm to obtain a 6 mol / L dilute hydrochloric acid solution.

[0070] (3) Pretreatment of MAX phase precursor:

[0071] Mix 40 mL of the lithium fluoride etchant solution obtained in step (1) with 40 mL of the 6 mol / L dilute hydrochloric acid solution obtained in step (2) to obtain a mixed etching system; add 1.0 g of high-purity V2AlC powder (200 mesh, purity 99.9%) to the above mixed etching system, and carry out a pre-etching reaction for 60 min under strong stirring at 500 rpm to ensure that the MAX phase precursor (i.e. V2AlC) is fully wetted and undergoes preliminary etching;

[0072] (4) Microwave-assisted controlled etching:

[0073] The reaction system from step (3) was transferred to a 200 mL polytetrafluoroethylene-lined high-pressure reactor, and then placed in a microwave reactor. The microwave reaction parameters were set as follows: output power of 400 W, reaction temperature of 140 ± 2 °C, and etching time of 12 h. After the reaction was completed, the mixture was centrifuged (6000 rpm, 3 min, 7 times, the same below), washed (alternating washing with anhydrous ethanol / deionized water until neutral), and dried (dried at 70 °C for 10 h) to finally obtain V2CT with precise controllable interlayer spacing. x Material.

[0074] The V2CT prepared in this embodiment x The material has an average interlayer spacing of 0.37 μm and is lamellar.

[0075] Example 2

[0076] This embodiment provides a method for preparing MXene materials with adjustable interlayer spacing via microwave-assisted chemical etching, the steps of which are as follows:

[0077] (1) Preparation of homogeneous etchant solution:

[0078] Accurately weigh 0.05 mol of high-purity lithium fluoride powder (LiF, purity ≥99%) and 0.05 mol of high-purity sodium fluoride powder (NaF, purity ≥99%), dissolve them in 40 mL of ultrapure water, and continuously disperse them for 30 min under constant magnetic stirring at 350 rpm to obtain a uniform and stable mixed etchant solution of lithium fluoride and sodium fluoride.

[0079] (2) Preparation of acidic etching medium:

[0080] 20 mL of concentrated hydrochloric acid (12 mol / L) was accurately measured using a pipette and added dropwise to 20 mL of ultrapure water. The mixture was stirred evenly for 30 min under constant magnetic stirring at 350 rpm to obtain a 6 mol / L dilute hydrochloric acid solution.

[0081] (3) Pretreatment of MAX phase precursor:

[0082] The lithium fluoride and sodium fluoride mixed etchant solution obtained in step (1) was mixed with the 6 mol / L dilute hydrochloric acid solution obtained in step (2) to obtain a mixed etching system; 1.0 g of high-purity Ti3AlC2 powder (200 mesh, purity 99.9%) was added to the above mixed etching system, and a pre-etching reaction was carried out under strong stirring at 500 rpm for 60 min to ensure that the MAX phase precursor (i.e. Ti3AlC2) was fully wetted and preliminary etching occurred;

[0083] (4) Microwave-assisted controlled etching:

[0084] The reaction system from step (3) was transferred to a 200 mL polytetrafluoroethylene-lined high-pressure reactor, and then placed in a microwave reactor. The microwave reaction parameters were set as follows: output power of 400 W, reaction temperature of 140 ± 2 °C, and etching time of 12 h. After the reaction was completed, the mixture was centrifuged, washed (alternating between anhydrous ethanol and deionized water until neutral), and dried (dried at 70 °C for 10 h) to finally obtain Ti3C2T with precisely controllable interlayer spacing. x Material.

[0085] The Ti3C2T prepared in this embodiment x The material has an average interlayer spacing of 0.36 μm and is lamellar.

[0086] Example 3

[0087] This embodiment provides a method for preparing MXene materials with adjustable interlayer spacing via microwave-assisted chemical etching, the steps of which are as follows:

[0088] (1) Preparation of homogeneous etchant solution:

[0089] Accurately weigh 0.05 mol of high-purity lithium fluoride powder (LiF, purity ≥99%), dissolve it in 40 mL of ultrapure water, and continuously disperse it for 30 min under constant magnetic stirring at 350 rpm to obtain a uniform and stable lithium fluoride etchant solution.

[0090] (2) Preparation of acidic etching medium:

[0091] 20 mL of concentrated hydrochloric acid (12 mol / L) was accurately measured using a pipette and added dropwise to 6.67 mL of ultrapure water. The mixture was stirred evenly for 30 min under constant magnetic stirring at 350 rpm to obtain a 9 mol / L dilute hydrochloric acid solution.

[0092] (3) Pretreatment of MAX phase precursor:

[0093] The lithium fluoride etchant solution obtained in step (1) was mixed with the 9 mol / L dilute hydrochloric acid solution obtained in step (2) to obtain a mixed etching system; 1.0 g of high-purity V2AlC powder (200 mesh, purity 99.9%) was added to the above mixed etching system, and a pre-etching reaction was carried out under strong stirring at 500 rpm for 60 min to ensure that the MAX phase precursor (i.e. V2AlC) was fully wetted and preliminary etching occurred;

[0094] (4) Microwave-assisted controlled etching:

[0095] The reaction system from step (3) was transferred to a 200 mL polytetrafluoroethylene-lined high-pressure reactor, and then placed in a microwave reactor. The microwave reaction parameters were set as follows: output power of 200 W, reaction temperature of 100 ± 2 °C, and etching time of 12 h. After the reaction was completed, the mixture was centrifuged, washed (alternating between anhydrous ethanol and deionized water until neutral), and dried (drying at 70 °C for 10 h) to finally obtain V2CT with precisely controllable interlayer spacing. x Material.

[0096] The V2CT prepared in this embodiment x The material has an average interlayer spacing of 0.38 μm and is lamellar.

[0097] Example 4

[0098] This embodiment provides a method for preparing MXene materials with adjustable interlayer spacing via microwave-assisted chemical etching, the steps of which are as follows:

[0099] (1) Preparation of homogeneous etchant solution:

[0100] Accurately weigh 0.05 mol of high-purity lithium fluoride powder (LiF, purity ≥99%) and 0.05 mol of high-purity sodium fluoride powder (NaF, purity ≥99%), dissolve them in 40 mL of ultrapure water, and continuously disperse them for 30 min under constant magnetic stirring at 350 rpm to obtain a uniform and stable mixed etchant solution of lithium fluoride and sodium fluoride.

[0101] (2) Preparation of acidic etching medium:

[0102] 20 mL of concentrated hydrochloric acid (12 mol / L) was accurately measured using a pipette and added dropwise to 60 mL of ultrapure water. The mixture was stirred evenly for 30 min under constant magnetic stirring at 350 rpm to obtain a 3 mol / L dilute hydrochloric acid solution.

[0103] (3) Pretreatment of MAX phase precursor:

[0104] The lithium fluoride and sodium fluoride mixed etchant solution obtained in step (1) was mixed with the 3 mol / L dilute hydrochloric acid solution obtained in step (2) to obtain a mixed etching system; 1.0 g of high-purity V2AlC powder (200 mesh, purity 99.9%) was added to the above mixed etching system, and a pre-etching reaction was carried out under strong stirring at 500 rpm for 60 min to ensure that the MAX phase precursor (i.e. V2AlC) was fully wetted and preliminary etching occurred;

[0105] (4) Microwave-assisted controlled etching:

[0106] The reaction system from step (3) was transferred to a 200 mL polytetrafluoroethylene-lined high-pressure reactor, and then placed in a microwave reactor. The microwave reaction parameters were set as follows: output power of 400 W, reaction temperature of 140 ± 2 °C, and etching time of 48 h. After the reaction was completed, the mixture was centrifuged, washed (alternating between anhydrous ethanol and deionized water until neutral), and dried (drying at 70 °C for 10 h) to finally obtain V2CT with precisely controllable interlayer spacing. x Material.

[0107] The V2CT prepared in this embodiment x The material has an average interlayer spacing of 0.3 μm and is lamellar.

[0108] Example 5

[0109] This embodiment provides a method for preparing MXene materials with adjustable interlayer spacing via microwave-assisted chemical etching, the steps of which are as follows:

[0110] (1) Preparation of homogeneous etchant solution:

[0111] Accurately weigh 0.05 mol of high-purity potassium fluoride powder (KF, purity ≥99%) and 0.05 mol of high-purity sodium fluoride powder (NaF, purity ≥99%), dissolve them in 100 mL of ultrapure water, and continuously disperse them for 50 min under constant magnetic stirring at 550 rpm to obtain a homogeneous and stable mixed etchant solution of potassium fluoride and sodium fluoride.

[0112] (2) Preparation of acidic etching medium:

[0113] 20 mL of concentrated hydrochloric acid (12 mol / L) was accurately measured using a pipette and added dropwise to 60 mL of ultrapure water. The mixture was stirred evenly for 30 min under constant magnetic stirring at 350 rpm to obtain a 3 mol / L dilute hydrochloric acid solution.

[0114] (3) Pretreatment of MAX phase precursor:

[0115] The potassium fluoride and sodium fluoride mixed etchant solution obtained in step (1) was mixed with the 3 mol / L dilute hydrochloric acid solution obtained in step (2) to obtain a mixed etching system; 3.0 g of high-purity Cr2AlC powder (600 mesh, purity 99.9%) was added to the above mixed etching system, and a pre-etching reaction was carried out under strong stirring at 350 rpm for 50 min to ensure that the MAX phase precursor (i.e. Cr2AlC) was fully wetted and preliminary etching occurred;

[0116] (4) Microwave-assisted controlled etching:

[0117] The reaction system from step (3) was transferred to a 500 mL polytetrafluoroethylene-lined high-pressure reactor, and then placed in a microwave reactor. The microwave reaction parameters were set as follows: output power of 800 W, reaction temperature of 150 ± 2 °C, and etching time of 72 h. After the reaction was completed, the mixture was centrifuged, washed (alternating between anhydrous ethanol and deionized water until neutral), and dried (dried at 60 °C for 12 h) to finally obtain Cr2CT with precisely controllable interlayer spacing. x Material.

[0118] The Cr2CT prepared in this embodiment x The material has an average interlayer spacing of 0.63 μm and is lamellar.

[0119] Example 6

[0120] This embodiment provides a method for preparing MXene materials with adjustable interlayer spacing via microwave-assisted chemical etching, the steps of which are as follows:

[0121] (1) Preparation of homogeneous etchant solution:

[0122] Accurately weigh 0.2 mol of high-purity ammonium fluoride powder (NH4F, purity ≥99%), dissolve it in 200 mL of ultrapure water, and continuously disperse it for 60 min under constant magnetic stirring at 450 rpm to obtain a uniform and stable ammonium fluoride etchant solution.

[0123] (2) Preparation of acidic etching medium:

[0124] Same as Example 1;

[0125] (3) Pretreatment of MAX phase precursor:

[0126] The ammonium fluoride etchant solution obtained in step (1) was mixed with the 6 mol / L dilute hydrochloric acid solution obtained in step (2) to obtain a mixed etching system; 3.0 g of high-purity Nb2AlC powder (400 mesh, purity 99.9%) was added to the above mixed etching system, and a pre-etching reaction was carried out under strong stirring at 450 rpm for 30 min to ensure that the MAX phase precursor (i.e. Nb2AlC) was fully wetted and preliminary etching occurred;

[0127] (4) Microwave-assisted controlled etching:

[0128] The reaction system from step (3) was transferred to a 300 mL polytetrafluoroethylene-lined high-pressure reactor, and then placed in a microwave reactor. The microwave reaction parameters were set as follows: output power of 600 W, reaction temperature of 110 ± 2 °C, and etching time of 12 h. After the reaction was completed, the mixture was centrifuged, washed (alternating between anhydrous ethanol and deionized water until neutral), and dried (drying at 80 °C for 7 h) to finally obtain Nb2CT with precisely controllable interlayer spacing. x Material.

[0129] The Nb2CT prepared in this embodiment x The material has an average interlayer spacing of 0.45 μm and is lamellar.

[0130] Example 7

[0131] This embodiment provides a method for preparing MXene materials with adjustable interlayer spacing via microwave-assisted chemical etching, the steps of which are as follows:

[0132] (1) Preparation of homogeneous etchant solution:

[0133] Accurately weigh 0.1 mol of high-purity ammonium fluoride powder (NH4F, purity ≥99%), dissolve it in 200 mL of ultrapure water, and continuously disperse it for 40 min under constant magnetic stirring at 450 rpm to obtain a uniform and stable ammonium fluoride etchant solution.

[0134] (2) Preparation of acidic etching medium:

[0135] Same as Example 1;

[0136] (3) Pretreatment of MAX phase precursor:

[0137] The ammonium fluoride etchant solution obtained in step (1) was mixed with the 6 mol / L dilute hydrochloric acid solution obtained in step (2) to obtain a mixed etching system; 2.0 g of high-purity Ta4AlC3 powder (300 mesh, purity 99.9%) was added to the above mixed etching system, and a pre-etching reaction was carried out under strong stirring at 500 rpm for 50 min to ensure that the MAX phase precursor (i.e. Ta4AlC3) was fully wetted and preliminary etching occurred;

[0138] (4) Microwave-assisted controlled etching:

[0139] The reaction system from step (3) was transferred to a 300 mL polytetrafluoroethylene-lined high-pressure reactor, and then placed in a microwave reactor. The microwave reaction parameters were set as follows: output power of 500 W, reaction temperature of 120 ± 2 °C, and etching time of 24 h. After the reaction was completed, the mixture was centrifuged, washed (alternating between anhydrous ethanol and deionized water until neutral), and dried (drying at 70 °C for 8 h) to finally obtain Ta4C3T with precisely controllable interlayer spacing. x Material.

[0140] The Ta4C3T prepared in this embodiment x The material has an average interlayer spacing of 0.49 μm and is lamellar.

[0141] Example 8

[0142] This embodiment provides a method for preparing MXene materials with adjustable interlayer spacing through microwave-assisted chemical etching, which is the same as in Embodiment 1, except that:

[0143] The fluoride salt in step (1) is 0.05 mol lithium fluoride + 0.05 mol sodium fluoride;

[0144] The microwave reaction parameters in step (4) are: output power of 500W, reaction temperature of 130±2℃, and etching time of 24h.

[0145] The V2CT prepared in this embodiment x The material has an average interlayer spacing of 2.38 μm and is lamellar.

[0146] Example 9

[0147] This embodiment provides a method for preparing MXene materials with adjustable interlayer spacing through microwave-assisted chemical etching, which is the same as in Embodiment 1, except that:

[0148] The fluoride salt in step (1) is 0.1 mol lithium fluoride + 0.1 mol sodium fluoride;

[0149] The microwave reaction parameters in step (4) are: output power of 600W, reaction temperature of 140±2℃, and etching time of 12h.

[0150] The V2CT prepared in this embodiment x The material has an average interlayer spacing of 5.75 μm. What is its morphology and structure?

[0151] Example 10

[0152] This embodiment provides a method for preparing MXene materials with adjustable interlayer spacing through microwave-assisted chemical etching, which is the same as in Embodiment 1, except that:

[0153] The fluoride salt in step (1) is 0.1 mol lithium fluoride + 0.1 mol potassium fluoride;

[0154] The microwave reaction parameters in step (4) are: output power of 600W, reaction temperature of 130±2℃, and etching time of 12h.

[0155] The V2CT prepared in this embodiment x The material has an average interlayer spacing of 3.31 μm. What is its morphology and structure?

[0156] Example 11

[0157] This embodiment provides a method for preparing MXene materials with adjustable interlayer spacing by microwave-assisted chemical etching, which is the same as in embodiment 1, except that the microwave reaction parameters in step (4) are: the output power is 500W.

[0158] The V2CT prepared in this embodiment x The material has an average interlayer spacing of 0.47 μm and is lamellar.

[0159] Example 12

[0160] This embodiment provides a method for preparing MXene materials with adjustable interlayer spacing by microwave-assisted chemical etching, which is the same as that in embodiment 1, except that the microwave reaction parameters in step (4) are: the output power is 600W.

[0161] The V2CT prepared in this embodiment x The material has an average interlayer spacing of 1.49 μm and is lamellar.

[0162] Example 13

[0163] This embodiment provides a method for preparing MXene materials with adjustable interlayer spacing by microwave-assisted chemical etching, which is the same as that in embodiment 1, except that the microwave reaction parameters in step (4) are: the output power is 800W.

[0164] The V2CT prepared in this embodiment x The material has an average interlayer spacing of 2.38 μm and is lamellar.

[0165] V2CT prepared in some embodiments x Scanning electron microscope image of the material as follows Figure 1 As shown, (a) is the V2CT prepared in Example 1. x (b) shows the V2CT prepared in Example 4. x (c) is the V2CT prepared in Example 8. x (d) is the V2CT prepared in Example 13. x (e) is the V2CT prepared in Example 10.x (f) shows the V2CT prepared in Example 9. x It can be seen that the method of the present invention can successfully prepare MXene materials, and the interlayer spacing can be controlled.

[0166] Comparative Example 1

[0167] This comparative example provides a method for preparing MXene material, which differs from Example 1 in that: a forced-air drying oven is used instead of a microwave reactor in the preparation process, and etching is performed at 120°C for 168 hours to obtain V2CT. x Material.

[0168] Comparative Example 2

[0169] This comparative example provides a method for preparing MXene material, which differs from Example 1 in that a forced-air drying oven is used instead of a microwave reactor in the preparation process, while the time and temperature are the same as in Example 1.

[0170] V2CT prepared in this comparative example x Scanning electron microscope image of the material as follows Figure 2 As shown, the etching of the MAX phase precursor using a conventional heat source is incomplete.

[0171] Comparative Example 3

[0172] This comparative example provides a method for preparing MXene material, which differs from Example 4 in that hydrofluoric acid (mass concentration of 38%) is used instead of fluorine salt to etch the MAX phase precursor.

[0173] V2CT prepared in this comparative example x Scanning electron microscope image of the material as follows Figure 3 As shown, under the same conditions, the etching of the MAX phase precursor with hydrofluoric acid is excessive, and V2CT... x The material is easily oxidized into V2O5.

[0174] The large-aperture MXene obtained by microwave-assisted chemical etching in Example 9 (microwave hydrothermal) and conventional hydrothermal etching (Comparative Example 1) were subjected to EIS and HER tests. The test results are shown in the figures below. Figure 4 and Figure 5 It was found that compared with conventional hydrothermal etching, microwave-assisted chemical etching yielded MXene materials with larger opening sizes, resulting in significantly reduced impedance, while at 10 mA cm⁻¹... -2 The overpotential is as low as 193mV, which is better than the 223mV of conventional hydrothermal.

[0175] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing MXene materials with adjustable interlayer spacing via microwave-assisted chemical etching, characterized in that, Includes the following steps: A homogeneous fluoride salt solution is prepared by mixing fluoride salt with water; The homogeneous fluoride salt solution and the dilute hydrochloric acid solution were mixed to obtain the etching system; The MAX phase precursor was added to the etching system and a pre-etching reaction was carried out under magnetic stirring. The reaction mixture after pre-etching reaction is placed in a microwave synthesis reaction device for etching reaction. After cleaning and drying, the interlayer spacing adjustable MXene material is obtained.

2. The method for preparing microwave-assisted chemical etching interlayer spacing controllable MXene material according to claim 1, characterized in that, The ratio of the fluoride salt to the dilute hydrochloric acid solution is (0.05-0.2) mol : (20-200) mL; And / or, the concentration of the dilute hydrochloric acid solution is (3-9) mol / L.

3. The method for preparing microwave-assisted chemical etching interlayer spacing controllable MXene material according to claim 2, characterized in that, The fluoride salt is selected from at least one of potassium fluoride, lithium fluoride, sodium fluoride, and ammonium fluoride.

4. The method for preparing microwave-assisted chemical etching interlayer spacing controllable MXene material according to claim 1, characterized in that, The ratio of the amount of fluoride salt to the amount of the MAX phase precursor is (0.05-0.2) mol: (1-3) g.

5. The method for preparing microwave-assisted chemical etching interlayer spacing controllable MXene material according to claim 4, characterized in that, The MAX phase precursor is selected from one of V2AlC, V3AlC2, Cr2AlC, Cr3AlC2, Ti2AlC, Ti3AlC2, Nb2AlC, Nb3AlC4, Ta2AlC and Ta4AlC3.

6. The method for preparing microwave-assisted chemical etching interlayer spacing controllable MXene material according to claim 5, characterized in that, The particle size of the MAX phase precursor is 200-600 mesh.

7. The method for preparing microwave-assisted chemical etching interlayer spacing controllable MXene material according to claim 1, characterized in that, The magnetic stirring speed is 350-550 rpm, and the magnetic stirring time is 30-60 min.

8. The method for preparing microwave-assisted chemical etching interlayer spacing controllable MXene material according to claim 1, characterized in that, During the etching reaction, the microwave power is 200-800W, the temperature is 100-160℃, and the time is 12-72h.

9. The method for preparing microwave-assisted chemical etching interlayer spacing controllable MXene material according to claim 8, characterized in that, During the etching reaction, the microwave power was 600W, the temperature was 140℃, and the time was 12h.

10. An MXene material with adjustable interlayer spacing, characterized in that, It is prepared according to any one of claims 1-9.

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