A three-dimensional porous Ti3C2T x Method for preparing MXene

Abstract

A three-dimensional porous Ti3C2T x The MXene preparation method includes step S1, using Ti3AlC2 powder as raw material, employing an alkaline aqueous solution as an etchant, etching at 50–80°C and atmospheric pressure for 3–6 hours, followed by ultrasonic treatment for 1–3 hours to obtain an alkaline-etched Ti3AlC2 powder mixture; step S2, separating the alkaline-etched Ti3AlC2 powder mixture by filtration through a microporous membrane, washing with deionized water to remove impurities, and obtaining alkaline-etched Ti3AlC2 powder; step S3, dispersing the alkaline-etched Ti3AlC2 powder in anhydrous ethanol, ultrasonically treating for 1–3 hours, separating by filtration through a microporous membrane, washing with anhydrous ethanol to remove impurities, and obtaining a three-dimensional porous Ti3C2T. x MXene. This invention involves the direct alkaline etching of Ti3AlC2 powder into a three-dimensional porous Ti3C2T. x MXene, with its covalently bonded end-capped groups –O and –OH and abundant sodium ion intercalation, possesses an excellent three-dimensional micro / nano structure, making it a promising material for electromagnetic wave absorption and energy storage. The preparation process is simple, green, and safe.

Description

TECHNICAL FIELD

[0001] The present application relates to a MXene preparation method, in particular to a three-dimensional porous Ti3C2T x MXene preparation method. BACKGROUND

[0002] MXene material is a kind of metal carbide and metal nitride material with two-dimensional layered structure, and its appearance is similar to that of stacked graphene. Due to the unique structure and performance of MXene, it has been widely used in electromagnetic wave absorption, energy storage, catalyst, ion sieve, photo-thermal conversion, field effect transistor, topological insulator and hydrogen evolution reaction, etc. Many fields have attracted widespread attention all over the world.

[0003] Since 2011, Ti3C2T x MXene was first prepared by Naguib et al. of Yury Gogotsi's group in Drexel University, USA at room temperature by using hydrofluoric acid (HF) to selectively etch Ti3AlC2 powder. In the same etchant HF, various MXene materials have been prepared one after another. Naguib et al. first proposed that after removing the A (Al) layer, MXene (Ti3C2) layer can be separated from MAX phase (Ti3AlC2), and then through ultrasonic treatment, a new two-dimensional Ti3C2 MXene phase is obtained, and the effects of etching time, temperature, particle size and source of Ti3AlC2 on the preparation of two-dimensional Ti3C2 MXene by HF method are systematically studied (Naguib, M.; Mashtalir, O.; Carle, J.; et al.; Two-Dimensional Transition Metal Carbides. ACS Nano 2012, 6, 1322-1331.). In addition, the strength of A bond also determines the etching conditions.

[0004] Because of the use of fluoride-based etchant in the conventional method, the surface of MXene is always covalently bonded to –F, –O and –OH groups. Generally, MXene can be represented as M n+1 X n T xwhere T represents surface termination groups, including -F, -O and -OH. The -OH group is not stable due to the presence of hydrogen atom, which can be replaced by alkali metals (such as Li, Na and K), alkaline earth metals (such as Mg and Ca) or transition metals (such as Pb). In addition, at high temperatures, -OH group can be converted to -O type group. Therefore, the MXene surface can be quite complex combination of one or some -OH, -O and -F and other termination groups, which greatly affect its performance. However, through chemical treatment, thermal annealing and mechanical exfoliation process, MXene can be combined with specific termination groups.

[0005] On the other hand, in order to reduce or eliminate the use of harmful etchant HF, researchers are committed to find new ways to prepare more MXene. Currently, Ghidiu et al. (Ghidiu, M.; Lukatskaya, M. R.; Zhao, M.-Q.; et al., Conductive Two-Dimensional Titanium Carbide 'clay' with High Volumetric Capacitance. Nature 2014, 516, 78-81.) reported the use of a mixture of HC1 and LiF to form HF in situ as etchant instead of HF. Compared with HF etchant, the in-situ formed HF selectively etches the "A" layer, which is a relatively simple, safe and fast route. Because of the intercalation of water and cations between the MXene layers, the obtained MXene has a larger interlayer spacing and weaker interaction, and the sheet layer does not have nanoscale defects; compared with HF, LiF and HC1 are much milder. In addition, NaF, KF, CsF, CaF2and other fluorides can replace LiF, and H2SO4can replace HC1, and this method has been successfully applied to prepare a variety of MXene. At the same time, Halim et al. (Halim, J.; Lukatskaya, M. R.; Cook, K. M.; et al.; Transparent Conductive Two-Dimensional Titanium Carbide Epitaxial Thin Films. Chemistry of Materials 2014, 26, 2374-2381.) proposed NH4HF2as a new etchant, because the obtained MXene composition film has ionic interaction with NH3and NH4 + The obtained MXene film is a promising material for transparent conductive electrodes, sensors and other applications.

[0006] Currently, most of the two-dimensional Ti3C2T xMXene nanosheets are prepared by a wet chemical method, by etching its parent MAX phase Ti3AlC2 powder in a fluorine-based etchant (such as HF, in situ formed HF, difluorides such as NH4HF2, etc.) and assembling into three-dimensional Ti3C2T x MXene surfaces covalently bind several end-capping groups, which greatly affect their excellent performance. At the same time, in order to prevent layer-by-layer stacking from affecting their excellent performance, two-dimensional Ti3C2T x MXene nanosheets need to be assembled into three-dimensional Ti3C2T x MXene materials are applied in specific fields (electromagnetic wave absorption, energy storage, etc.). Existing three-dimensional Ti3C2T x The MXene preparation method first etches the parent MAX phase Ti3AlC2 powder into two-dimensional Ti3C2T x MXene nanosheets; then through subsequent related processing, it is assembled into a three-dimensional structure.

[0007] Invention patent with application number 201910885633.8 discloses a self-supporting three-dimensional porous MXene foam material and a preparation method thereof, the preparation thereof comprising: (1) two-dimensional layered MXene preparation; such as Ti3C2T x MXene preparation, in situ formation of HF as etchant by adding LiF into concentrated hydrochloric acid, etching reaction for 24 hours. (2) Stirring and mixing the nanosulfur particle (template) dispersion liquid with the water dispersion liquid of two-dimensional layered MXene material, and filtering the MXene / sulfur composite film under reduced pressure; (3) Removing the sulfur template in the MXene / sulfur composite film. The preparation method disclosed in this patent utilizes a toxic fluorine-based etchant and has a long etching time; high-temperature heating or toxic organic solvent dissolution is required to remove the sulfur template.

[0008] Invention patent with application number 202011057801.3 discloses a high-performance silicon-carbon composite material and a preparation method thereof, wherein the MXene preparation process is as follows: hydrothermal treatment is carried out in a mass fraction 65% sodium hydroxide solution at 270°C to remove Al in Ti2AlC, and a silicon-carbon composite material Si@GE@Ti2C is prepared; or hydrothermal treatment is carried out in a mass fraction 65% sodium hydroxide solution at 200°C to remove Al in Ti3AlC2, and a silicon-carbon composite material Si@GE@Ti3C2 is prepared. This patent obtains Ti2C or Ti3C2 MXene in nanosheet structure instead of three-dimensional porous structure by high-temperature hydrothermal treatment in a mass fraction 65% sodium hydroxide solution.

[0009] Therefore, in order to effectively avoid the toxicity, corrosiveness, and environmental hazards of fluorine-based etchants, reduce or even eliminate the use of harmful etchants, and accelerate the process of large-scale preparation and functional application, it is necessary to explore a simple, safe, and scalable three-dimensional Ti3C2T with controllable surface-capped groups. x The preparation method of MXene is urgently needed and also a major challenge. Summary of the Invention

[0010] This invention addresses the shortcomings of existing technologies by proposing a simple method for directly transforming Ti3C2T using alkaline etching. x The MXene method eliminates the need for toxic fluorine-based etchants, high-temperature heating, or toxic solvents to dissolve and remove the template. It utilizes an alkaline aqueous solution as the etchant to directly etch the raw material Ti3AlC2 powder into three-dimensional porous MXene, resulting in a shorter etching reaction time.

[0011] This invention develops a simple and safe porous Ti3C2T x The MXene preparation method involves selectively etching the Al layer in the MAX phase Ti3AlC2 in NaOH aqueous solution, accompanied by the generation of a large number of H2 bubbles and ultrasonic treatment, which significantly accelerates the etching process. Then, filtration, cleaning, and ultrasonic delamination directly transform the Ti3AlC2 powder into a novel three-dimensional porous Ti3C2T with excellent microstructure. x MXene, with its covalently bonded surface-capped groups –O and –OH and a large number of sodium ion intercalation effects, holds promise for applications such as electromagnetic wave absorption and energy storage. Compared to traditional fluorine-based etchants, this invention features a simpler, safer, and faster preparation process, requires no special equipment, and is easily mass-produced. Currently, there are no related literature reports on its application.

[0012] The present invention adopts the following technical solution:

[0013] Three-dimensional porous Ti3C2T prepared using Ti3AlC2 powder x MXene includes the following steps:

[0014] Step 1: Using Ti3AlC2 powder as raw material, alkaline NaOH aqueous solution (6-9 mol / L) is used as etching agent. The etching process is carried out at 50-80℃ and normal pressure for 3-6 hours, accompanied by the generation of a large number of H2 bubbles. The mixture is then ultrasonically treated for 1-3 hours to prepare an alkaline etched Ti3AlC2 powder mixture.

[0015] Step 2: The alkaline etched Ti3AlC2 powder mixture prepared in Step 1 is filtered and separated through a microporous membrane, and washed with deionized water 3 to 5 times to remove impurities, thereby obtaining alkaline etched Ti3AlC2 powder.

[0016] Step three, the alkaline etching treated Ti3AlC2 powder prepared in step two is dispersed in anhydrous ethanol and ultrasonic treated for 1-3 hours to expand the three-dimensional porous Ti3C2T x The interlayer spacing of the MXene is separated by microfiltration membrane filtration and then washed 3-5 times with anhydrous ethanol to remove impurities and obtain the three-dimensional porous Ti3C2T x MXene;

[0017] Step four, the three-dimensional porous Ti3C2T x MXene prepared in step three is dried in a vacuum drying box at 60-90 DEG C for 6-10 hours.

[0018] Advantages of the application:

[0019] 1. The alkaline aqueous solution is used as an etchant to directly etch the raw material Ti3AlC2 powder into three-dimensional porous Ti3C2T x MXene, and the etching reaction time is short; the alkaline NaOH aqueous solution (6-9 mol / L) is used as the etchant, and no toxic and harmful fluorine-based etchant containing fluorine elements is needed, which is green and safe; no template is needed, so no high-temperature heating or toxic solvent is needed to remove the template, and the operation is simple. The three-dimensional porous Ti3C2T x MXene, which covalently bonds groups -O and -OH and has a large number of sodium ions intercalated, thus has an excellent three-dimensional micro-nano structure and is expected to become an ideal material for electromagnetic wave absorption and energy storage.

[0020] 2. In the application, the Ti3AlC2 powder is dispersed in the alkaline NaOH aqueous solution and etched at 50-80 DEG C under normal pressure, a large amount of H2 bubbles is generated, and ultrasonic treatment accelerates the etching process, so that the reaction time is 4-9 hours, while the traditional fluorine-based etchant generally needs 24 hours. The preparation process is simple, the etching reaction time is short, and batch production is easy.

[0021] 3. The three-dimensional porous Ti3C2T x MXene preparation method, the alkaline etching treated Ti3AlC2 powder is dispersed in anhydrous ethanol and ultrasonic treated to obtain the three-dimensional porous Ti3C2T x MXene, which not only can expand the three-dimensional porous Ti3C2T x MXene, without adding an organic intercalating agent, and after ultrasonic treatment, the interlayer spacing is separated by microfiltration membrane filtration, which is conducive to further cleaning and removing impurities; the traditional fluorine-based etchant also needs to add an organic intercalating agent and needs subsequent processing.

[0022] 4. The three-dimensional porous Ti3C2T xThe MXene preparation method uses an alkaline aqueous solution as an etchant to directly etch a raw material Ti3AlC2 powder into three-dimensional porous MXene, and has excellent three-dimensional micro-nano structure instead of a simple nanosheet structure, without high temperature (200 or 270 DEG C) and high pressure (reaction in a high-pressure reaction kettle). BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a scanning electron microscope image of Ti3AlC2 powder with a magnification of 5000 times;

[0024] Figure 2 is a scanning electron microscope image of Ti3AlC2 powder with a magnification of 30000 times;

[0025] Figure 3 is a scanning electron microscope image of Ti3AlC2 powder treated by alkaline etching with a magnification of 30000 times;

[0026] Figure 4 is a scanning electron microscope image of Ti3AlC2 powder treated by alkaline etching with a magnification of 60000 times;

[0027] Figure 5 is a scanning electron microscope image of three-dimensional porous Ti3C2T x is a scanning electron microscope image of MXene;

[0028] Figure 6 is a scanning electron microscope image of Ti3AlC2 powder and three-dimensional porous Ti3C2T x is an X-ray diffraction pattern of MXene;

[0029] Figure 7 is an X-ray diffraction pattern of Ti3AlC2 powder and three-dimensional porous Ti3C2T x is an infrared spectrum of MXene;

[0030] Figure 8 is an infrared spectrum of Ti3AlC2 powder and three-dimensional porous Ti3C2T x is an X-ray photoelectron spectrum of MXene; DETAILED DESCRIPTION

[0031] In order to make the technical concept and advantages of the present application to realize the purpose of the application more clear and explicit, the technical solutions of the present application are further described in detail below in combination with the drawings. It should be understood that the following examples are only used to explain and illustrate the preferred embodiments of the present application, and should not be regarded as limiting the scope of the patent protection required by the present application.

[0032] Example 1

[0033] The present application uses Ti3AlC2 powder to prepare three-dimensional porous Ti3C2Tx MXene, comprising the following steps:

[0034] First step: using Ti3AlC2 powder (see Figure 1 , Figure 2 ) as raw material, alkali etching treatment of Ti3AlC2 powder mixture was prepared by using NaOH aqueous solution as etchant. The specific process is as follows:

[0035] (1) In a clean 250 mL beaker, add NaOH aqueous solution (6 mol / L) 100 mL, slowly pour 2 g Ti3AlC2 powder into it, and heat the mixture to 60°C using water bath heating.

[0036] (2) Etching treatment for 3 hours under normal pressure, accompanied by a large amount of H2 bubbles, and ultrasonic treatment for 2 hours, to prepare alkali etching treated Ti3AlC2 powder mixture.

[0037] Second step: the alkali etching treated Ti3AlC2 powder mixture prepared in step one was separated by micro porous filter membrane, washed with deionized water for 3 times to remove impurities, and then alkali etching treated Ti3AlC2 powder (see Figure 3 , Figure 4 ) was obtained.

[0038] The micro porous filter membrane is a mixed cellulose ester micro porous filter membrane with a diameter of 80 mm and a pore size of 0.22 μm.

[0039] Third step: the alkali etching treated Ti3AlC2 powder prepared in step two was dispersed in anhydrous ethanol and ultrasonically treated for 2 hours, then separated by micro porous filter membrane, washed with anhydrous ethanol for 3 times to further remove impurities, and then three-dimensional porous Ti3C2T x MXene was obtained. The micro porous filter membrane is a mixed cellulose ester micro porous filter membrane with a diameter of 80 mm and a pore size of 0.22 μm.

[0040] Fourth step: the three-dimensional porous Ti3C2T x MXene prepared in step three was dried in a vacuum drying oven at 70°C for 6 hours.

[0041] Figure 1 , Figure 2 The scanning electron microscope images of the raw material MAX phase Ti3AlC2 powder at different magnifications are shown in the figure, showing that the particle diameter is 0-5 μm.

[0042] Figure 3 , Figure 4The images shown are scanning electron microscope images of Ti3AlC2 powder at different magnifications after alkaline etching, showing that the Ti3AlC2 powder has been etched into a three-dimensional cross-linked structure with excellent microstructure.

[0043] The three-dimensional porous Ti3C2T obtained above x MXene was used to characterize its microstructure and composition.

[0044] like Figure 5 As shown, this is a three-dimensional porous Ti3C2T x MXene scanning electron microscope images show that it consists of countless Ti3C2T x Three-dimensional porous micro / nano structures composed of cross-linked MXene nanosheets or nanoribbons.

[0045] Figure 6 The image shows Ti3AlC2 powder and three-dimensional porous Ti3C2T. x The X-ray diffraction pattern of MXene shows that, relative to Ti3AlC2 powder, the three-dimensional porous Ti3C2T x The X-ray diffraction (002) peak of MXene is smaller, and the interlayer spacing is correspondingly larger;

[0046] Figure 7 The image shows Ti3AlC2 powder and three-dimensional porous Ti3C2T. x The infrared spectrum of MXene shows that, relative to Ti3AlC2 powder, the three-dimensional porous Ti3C2T x The intensity of oxygen-containing groups (OH, C=O, COC, Ti-O) in MXene is enhanced, and a new peak (CH) appears;

[0047] Figure 8 The image shows Ti3AlC2 powder and three-dimensional porous Ti3C2T. x X-ray photoelectron spectroscopy of MXene; showing that, relative to Ti3AlC2 powder, Ti3C2T is a three-dimensional porous Ti3C2T x In MXene, the intensity of the Ti2p peak increases (increased Ti content), while the intensity of the Al2p peak decreases (decreased Al content). In particular, a new peak, Na1s, appears (sodium ion intercalation).

[0048] Example 2

[0049] The three-dimensional porous Ti3C2T in this embodiment x The main difference between the MXene preparation method and Example 1 is that the concentration of the etching agent NaOH aqueous solution is adjusted to 9 mol / L; and the mixture is heated to 70°C by water bath heating.

[0050] First step: Ti3AlC2 powder as raw material, using alkaline NaOH solution as etchant for etching reaction, preparation of alkaline etching treatment of Ti3AlC2 powder mixture. Specifically as follows:

[0051] (1) in a clean 250ml beaker, add NaOH aqueous solution (9mol / L) 100ml, slowly pour 2g Ti3AlC2 powder into it, heat the mixture to 70℃ by water bath heating.

[0052] (2) etching treatment for 3 hours under normal pressure, accompanied by a large amount of H2 bubble generation, and ultrasonic treatment for 2 hours, preparation of alkaline etching treatment of Ti3AlC2 powder mixture.

[0053] Second step: the alkaline etching treatment of Ti3AlC2 powder mixture prepared in step one, through microporous filter membrane filtration separation, washed with deionized water for 3 times, remove impurities, obtain alkaline etching treatment of Ti3AlC2 powder. Microporous filter membrane is mixed cellulose ester microporous filter membrane, diameter is 80mm, pore size is 0.45μm.

[0054] Third step: the alkaline etching treatment of Ti3AlC2 powder prepared in step two is dispersed in anhydrous ethanol and ultrasonic treated for 2 hours, separated by microporous filter membrane, washed with anhydrous ethanol for 3 times, further cleaning to remove impurities, obtain three-dimensional porous Ti3C2T x MXene. Microporous filter membrane is mixed cellulose ester microporous filter membrane, diameter is 80mm, pore size is 0.45μm.

[0055] Fourth step: the three-dimensional porous Ti3C2T x MXene prepared in step three is dried in a vacuum drying oven at 80℃ for 6 hours.

[0056] The three-dimensional porous Ti3C2T x MXene prepared above is characterized in microstructure and composition, the micro-morphology and structure of the obtained three-dimensional porous Ti3C2T x MXene are basically the same as example 1.

[0057] Example 3

[0058] The preparation method of three-dimensional porous Ti3C2T x MXene in this example is mainly different from example 1 in that the etching reaction time of NaOH aqueous solution is adjusted to 6 hours, and the ultrasonic treatment time is 3 hours.

[0059] The preparation method of three-dimensional porous Ti3C2T x MXene using Ti3AlC2 powder, including the following steps:

[0060] First step: Ti3AlC2 powder as raw material, using alkaline NaOH aqueous solution as etchant for etching reaction, preparation of alkaline etching treatment Ti3AlC2 powder mixture. Specifically as follows:

[0061] (1) In a clean 250mL beaker, add NaOH aqueous solution (6mol / L) 100mL, slowly pour 2g Ti3AlC2 powder into it, heat the mixture to 60℃ by water bath heating.

[0062] (2) Etching treatment for 6 hours under normal pressure, accompanied by a large amount of H2 bubble generation, and ultrasonic treatment for 3 hours, preparation of alkaline etching treatment Ti3AlC2 powder mixture.

[0063] Second step: The alkaline etching treatment Ti3AlC2 powder mixture prepared in step one is filtered and separated by a microporous filter membrane, washed with deionized water for 3 times to remove impurities, and alkaline etching treatment Ti3AlC2 powder is obtained. The microporous filter membrane is a mixed cellulose ester microporous filter membrane with a diameter of 80mm and a pore size of 0.22μm.

[0064] Third step: The alkaline etching treatment Ti3AlC2 powder prepared in step two is dispersed in anhydrous ethanol and ultrasonic treated for 3 hours, filtered and separated by a microporous filter membrane, washed with anhydrous ethanol for 3 times to further remove impurities, and three-dimensional porous Ti3C2T x MXene is obtained. The microporous filter membrane is a mixed cellulose ester microporous filter membrane with a diameter of 80mm and a pore size of 0.22μm.

[0065] Fourth step: The three-dimensional porous Ti3C2T x MXene prepared in step three is dried in a vacuum drying box at 80℃ for 6 hours.

[0066] The three-dimensional porous Ti3C2T x MXene prepared above is characterized in microstructure and composition, and the micro-morphology and structure of the three-dimensional porous Ti3C2T x MXene are basically the same as those of Example 1.

[0067] The alkaline NaOH aqueous solution is used as the etchant in the present application, and no etchant containing fluorine element and organic intercalation agent is needed. The preparation method is simple, green and safe, and the operation is under normal pressure without special equipment and high temperature. The preparation time is greatly shortened, and batch production is easy. No two-dimensional Ti3C2T x MXene needs to be prepared first, and then assembled into three-dimensional Ti3C2T x MXene through a complex subsequent treatment process. Importantly, the Ti3AlC2 powder is directly converted into three-dimensional porous Ti3C2Tx MXene, surface covalent linkage with end groups –O and –OH, no group –F, while a large number of sodium ions intercalation, the three-dimensional porous structure has excellent microstructure and structure, is expected to become the ideal nanomaterials applied to electromagnetic wave absorption and energy storage carrier.

Claims

1. A three-dimensional porous Ti3C2T x MXene preparation method characterized by, The application relates to a method for preparing Ti3AlC2 powder, which comprises the following steps: S1, taking Ti3AlC2 powder as raw material, using 6-9 mol / L alkaline NaOH aqueous solution as etching agent, etching treatment is carried out at 50-80 DEG C under normal pressure for 3-6 hours, a large amount of H2 bubbles are generated, and ultrasonic treatment is carried out for 1-3 hours, thereby obtaining an alkaline etching treated Ti3AlC2 powder mixture; S2, the alkaline etching treated Ti3AlC2 powder mixture obtained in the step S1 is filtered and separated through a microporous filter membrane, is washed with deionized water for 3-5 times, and impurities are removed, thereby obtaining alkaline etching treated Ti3AlC2 powder; Step S3, the alkaline etching treated Ti3AlC2 powder obtained in step S2 is dispersed in anhydrous ethanol and ultrasonically treated for 1-3 hours, filtered and separated through a microporous filter membrane, washed with anhydrous ethanol for 3-5 times, impurities are removed, and three-dimensional porous Ti3C2T x Mxene; Step S4, drying the three-dimensional porous Ti3C2T MXene obtained in step S3 in a vacuum drying box at 60-90℃ for 6-10 hours to obtain a three-dimensional porous Ti3C2T MXene solid powder. x MXene, in a vacuum drying box at 60-90℃ for 6-10 hours to obtain a three-dimensional porous Ti3C2T MXene solid powder. x MXene, in a vacuum drying box at 60-90℃ for 6-10 hours to obtain a three-dimensional porous Ti3C2T MXene solid powder.

2. The three-dimensional porous Ti3C2T x The method for preparing MXene is characterized in that: In the step S3, the microporous filter membrane is a mixed cellulose ester microporous filter membrane, the diameter is 60-90 mm, and the pore size is 0.22 mu m or 0.45 mu m.

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