CN112794328B

CN112794328B - Method for preparing MXene material

Info

Publication number: CN112794328B
Application number: CN202110074013.3A
Authority: CN
Inventors: 林紫锋; 刘颖; 马国良; 陈津津
Original assignee: Sichuan University
Current assignee: Sichuan University
Priority date: 2021-01-20
Filing date: 2021-01-20
Publication date: 2021-08-17
Anticipated expiration: 2041-01-20
Also published as: CN112794328A

Abstract

The invention provides a method for preparing MXene materials, which comprises the steps of carrying out alcohol wet mixing on elementary substance powder or alloy powder corresponding to MAX in an agate mortar, then adding NaCl and KCl, and mixing to obtain raw material powder; adding raw material powder to the bottom of a corundum crucible, adding a mixture of NaCl and KCl to cover the raw material powder, and packaging inorganic salt; adding the corundum crucible into a muffle furnace, heating to the synthetic temperature of the corresponding MAX phase, preserving the heat, and then cooling at the same rate as the heating process; when the temperature is reduced, adding an etching agent into the corundum crucible, keeping the temperature for a certain time, and then cooling along with the furnace; and washing off inorganic salt in the product by using deionized water, and washing off a metal element simple substance displaced by an etching agent in the product by using acid. The invention directly uses element powder or alloy powder to directly prepare MXene target product by using a molten salt method, thereby reducing the cost and period of the prior process.

Description

Method for preparing MXene material

Technical Field

The invention belongs to the technical field of new material preparation, and particularly relates to a method for preparing MXene material, namely a method for preparing two-dimensional transition metal carbide, nitride or carbonitride MXene.

Background

The MAX phase material is a material with a compact interlayer lamellar structure, has the common characteristics of metal and ceramic, M is a transition metal element, A is a 3-6 main group element, and X is C or N; MXene is a derivative phase based on an MAX phase, an A atomic layer is removed by an etchant, a unique two-dimensional layered structure and a specific functional group on the surface of the two-dimensional layered structure are obtained, the interlayer spacing is large, and the MXene is a good cathode material. Because of the large variety of MAX materials, such as 211, 312, 413, etc., the variety of MXene materials is large. Functional groups on the surfaces of MXene products obtained by different etching methods are also different, and early-stage more etching modes are etching by hydrofluoric acid, wherein the surfaces of the MXene products are mainly fluorine-containing functional groups; with some chloride etchants, the surface is predominantly some functional groups containing chlorine.

From 2011, MXene is synthesized by selectively etching A layer atoms in a MAX phase, wherein HF and NaOH are contained or in-situ generation methods of HF and NaOH are common. In addition, methods such as molten salt etching, electrochemical etching, and ionic liquid etching are also used. At present, all the synthesis methods use MAX phase as raw material, and obtain two-dimensional MXene through etching reaction. The invention mainly adopts a molten salt method to reduce the molten salt to a proper temperature for subsequent Lewis acid etching on the basis of preparing the MAX at a high temperature, thereby directly obtaining the MXene target product and reducing the cost and the period of the prior process.

Disclosure of Invention

Aiming at the technical problems, the invention provides a method for directly obtaining MXene materials through corresponding elemental elements or alloy raw materials.

The specific technical scheme is as follows:

a method of making an MXene material comprising the steps of:

(1) raw meal preparation

Weighing elementary substance powder or alloy powder of an element corresponding to MAX according to a molar ratio, carrying out alcohol wet mixing in an agate mortar until the alcohol is completely volatilized, then adding two or more halide salts (such as NaCl, KCl and the like), and mixing to obtain raw material powder;

adding raw material powder to the bottom of a corundum crucible, adding a mixture of halide salt to cover the upper part of the raw material powder, and packaging the halide salt;

(2) synthesis process

Covering the corundum crucible, putting the corundum crucible into a muffle furnace, raising the temperature to the synthetic temperature (900-;

(3) product processing

And washing off inorganic salt in the product by using deionized water, and washing off a metal element simple substance displaced by an etching agent in the product by using acid.

Preferably:

in the step (1), the MAX phase comprises MAX phase (Ti) prepared by a molten salt method₃AlC₂、Ti₂AlC、Ti₂SnC、V₂AlC、Ti₃SiC₂、Ti₂SC、Nb₂AlC、Nb₂SnC、Ti₃AlCN、Ta₂AlC、Ti₂AlN, etc.) corresponding to MXene phase, including Ti₃C₂、Ti₂C、Ti₂N、V₂C、Ti₃CN、Nb₂C、Ta₂C and the like.

In the step (1), the halide salt added to the raw material powder is a mixture of two or more halide salts.

In the step (1), the halide salt covering the raw material powder forms molten salt after reaching the eutectic melting point, plays a role in isolating air from reaction products and a reaction process, and is used as a salt bed for mass and heat transfer.

Further:

in the step (2), when the temperature is reduced to 300-900 ℃, an etching agent is added into the corundum crucible.

In the step (2), the etching agent is Lewis acid (CuCl)₂、CoCl₂、ZnCl₂、FeCl₃、NiCl₂、AgCl、FeCl₂、CdCl₂Etc.).

In the step (2), the preparation and etching processes do not need any protective atmosphere.

The MXene target product is prepared by directly using elemental powder or alloy powder by a molten salt method, so that the cost of synthesizing MAX phase to obtain the product and then performing an etching process is reduced, and the experimental period is shortened to 5-7 hours from more than twenty hours.

Drawings

Fig. 1 is an XRD image of the product prepared in example 1.

Fig. 2 is an SEM image of the product prepared in example 1.

Figure 3 is an XRD image of the product prepared in example 2.

Fig. 4 is an SEM image of the product prepared in example 2.

Detailed Description

In order to make the technical scheme and advantages of the method more clearly understood, the invention is further described in detail with reference to the following examples; it should be understood that the specific examples described herein are intended to be illustrative only and are not intended to be limiting; reagents, methods and apparatus used in the present invention are conventional in the art unless otherwise indicated.

Example 1

Ti₃C₂Two-dimensional MXene preparation, comprising the following steps:

s1, preparing raw materials: the method comprises the following steps of weighing simple substance powder of Ti, Al and C with the purity of more than 99%, wet-mixing the simple substance powder with alcohol in an agate mortar for 30min until the alcohol is completely volatilized according to the molar ratio of Ti to Al to C being 3 to 1.2 to 1.9, adding an inorganic salt mixture with the molar ratio of Ti to NaCl to KCl being 3 to 4, and dry-mixing for 10 min.

S2, pretreatment in heat treatment: briquetting the raw materials by using a stainless steel die with the diameter of 20mm, placing the raw materials in a corundum crucible, adding a NaCl and KCl mixture with twice of the mass of the raw materials, covering the raw materials on the raw materials, and packaging the raw materials by using inorganic salt.

S3, heat treatment process: placing the corundum crucible in a muffle furnace, heating to 800 ℃ at a speed of 10 ℃/min, heating to 1300 ℃ at a speed of 5 ℃/min, preserving heat for 1 hour, cooling to 800 ℃ at a speed of 5 ℃/min, cooling to 700 ℃ along with the furnace, and adding CuCl with a molar ratio of 1:6 to MAX₂The etchant is directly cooled along with the furnace.

S4, product treatment: washing with deionized water for 3 times, washing to remove inorganic salts in the product, then carrying out acid washing with 0.5mol/L ammonium persulfate for two hours, washing to remove Cu simple substance in the product, and drying at 60 ℃ in vacuum for 12 hours to obtain loose powder.

S5, product characterization: the phase analysis of the obtained product is shown in FIG. 1, and the microstructure is shown in FIG. 2.

Example 2

Ti₂The preparation of the N two-dimensional MXene comprises the following steps:

s1, preparing raw materials: the preparation method comprises the following steps of weighing simple substance powder with the total weight of 2g by adopting Ti and AlN powder with the purity of more than 99 percent according to the molar ratio of Ti to AlN of 2:1, wet-mixing the simple substance powder with alcohol in an agate mortar for 30min until the alcohol is completely volatilized, adding an inorganic salt mixture with the molar ratio of Ti to NaCl to KCl of 3:4:4, and dry-mixing for 10 min.

S3, heat treatment process: placing the corundum crucible in a muffle furnace, heating to 800 ℃ at a speed of 10 ℃/min, heating to 1250 ℃ at a speed of 5 ℃/min, preserving heat for 1 hour, cooling to 800 ℃ at a speed of 5 ℃/min, cooling to 700 ℃ along with the furnace, and adding CuCl with a molar ratio of 1:6 to MAX₂Etching with etchant, keeping the temperature for 30min, and cooling with the furnace.

S5, product characterization: the phase analysis of the obtained product is shown in FIG. 3, and the microstructure is shown in FIG. 4.

Claims

1. A method of making an MXene material comprising the steps of:

(1) raw meal preparation

Weighing elementary substance powder or alloy powder of an element corresponding to MAX according to a molar ratio, carrying out alcohol wet mixing in an agate mortar until the alcohol is completely volatilized, then adding two or more halide salts, and mixing to obtain raw material powder;

(2) synthesis process

Adding the corundum crucible into a muffle furnace, heating to the synthesis temperature of 900-Keeping the temperature for a certain time, and cooling along with the furnace; the etchant is Lewis acid (CuCl)₂、CoCl₂、ZnCl₂、FeCl₃、NiCl₂、AgCl、FeCl₂、CdCl₂One of (1);

the preparation and etching processes do not need any protective atmosphere;

(3) product processing

And washing away halide in the product by using deionized water, and removing a metal element simple substance displaced by an etching agent in the product by using acid.

2. The method of claim 1, wherein in step (1), the MAX phase comprises MAX Ti phase prepared by a molten salt method₃AlC₂、Ti₂AlC、Ti₂SnC、V₂AlC、Ti₃SiC₂、Ti₂SC、Nb₂AlC、Nb₂SnC、Ti₃AlCN、Ta₂AlC、Ti₂AlN, its corresponding MXene phase, including Ti₃C₂、Ti₂C、Ti₂N、V₂C、Ti₃CN、Nb₂C、Ta₂C。

3. The method of claim 1, wherein in step (1), the halide salt coated on the raw powder acts as a bed of air-barrier, oxidation-prevention and mass transfer salt to the raw powder after reaching eutectic melting point.