Method for catalytically synthesizing MXene two-dimensional material with target terminal

Abstract

The invention discloses a method for catalytically synthesizing an MXene two-dimensional material with a target terminal, and belongs to the technical field of novel two-dimensional materials. The invention provides a method for obtaining an MXene two-dimensional material with a target terminal by a one-step catalytic synthesis method. The method comprises the following steps: placing MAX phase powder, a catalyst precursor and a target terminal precursor in a vacuum sealed ampoule tube according to a certain molar ratio; placing one end filled with the MAX phase powder, the catalyst precursor and the target terminal precursor in a high-temperature area, placing the other end in a low-temperature area, and naturally cooling to room temperature after the reaction is finished; cutting the cooled ampoule tube, and collecting to obtain the MXene two-dimensional material with the target terminal.The method has universality, is suitable for large-scale production and application and is an efficient and economical synthesis method, and the MXene material prepared through the method can also be applied to multiple technical fields.

Description

Technical Field

[0001] The present invention belongs to the technical field of novel two-dimensional materials, and specifically relates to a method for catalytically synthesizing a MXene two-dimensional material with a target terminal. Background Art

[0002] As an emerging two-dimensional material with adjustable surface functional groups, MXene has very broad application prospects and is widely used in batteries, supercapacitors, biology, electromagnetic shielding, catalysis and other fields. It is mainly prepared by etching the precursor MAX phase. The MX elements and the A-layer elements are alternately combined to form a layered structure, where M represents early transition metal elements (such as Ti, Nb, V, Mo, etc.), A represents main group elements (such as Al, Si, Ga, Sn, etc.) and some transition elements (such as Zn, Cd, etc.), and X represents C and N. Since the "MA" metal bond is often weaker than the "MX" covalent bond, the A-layer elements can be selectively etched to obtain a general formula of M n+1 X n T x (n = 1, 2, 3) two-dimensional MXene, where T x Represents the surface termination, the specific element depends on the etching environment. x It has a great influence on the properties of MXene and directly determines the application potential of MXene. Traditional surface terminals of MXene (such as -O, -F, -Cl, -Br, -I) cannot meet the application requirements of MXene well (such as the lower capacitance of supercapacitors), which requires the exploration of other surface terminals. In addition to the introduction of halogen terminations, MXenes terminated by nitrogen and chalcogen elements, such as -S, -Se, -N and -P, have properties that are significantly different from traditional terminals. For example, MXenes terminated by pnictogens (such as -N, -P) are crucial for energy harvesting applications due to their lower electronegativity, rich valence changes and other properties that cannot be achieved by traditional terminations. However, due to the compounds formed at the end of the A element (such as Al) in the MAX phase (such as AlP x 、AlS x) due to their low solubility, high melting point, high boiling point and other properties, make the one-step direct synthesis of such MXenes materials a huge challenge. In addition, their diffusivity in solutions, molten salts and gas phases is extremely low, which hinders the direct formation of terminals. In traditional methods, MXenes with these terminals (-S, -Se, -N, -P, etc.) usually involve two-step replacement. In the first step, MXenes with -Cl / -Br terminals are preferentially synthesized. In this step, Al(Cl / Br)3 will diffuse into the solvent / flux / gas phase, achieve A etching in the MAX phase, and form -Cl / -Br terminals. Currently, many solution-based methods are not effective in forming -Cl / -Br because of the generation of strong dissociation energy -O that is difficult to replace. In the second step, the target element (such as P) / compound (such as H2S) will react with -Cl / -Br and replace -Cl / -Br. For example, in the gas phase method, the reaction between P and -Br forms PBr3 gas, which can diffuse in the gas phase, while the exposed Ti combines with P to form -P termination. In the molten salt method, Li2S, Li2Se react with -Cl / -Br to form LiCl / LiBr and -S, -Se terminations through the replacement effect. In addition to the complicated process of the two-step synthesis method, the traditional strategy usually involves other disadvantages, such as the use of harmful gases (such as H2S in the gas phase method), the removal of molten salt flux (molten salt method), and subsequent treatment processes. Therefore, it is necessary to develop a simple and safe method to directly obtain MXenes with such target terminations (-S, -Se, -N, -P, etc.). Summary of the invention

[0003] In view of the prior art, the present invention provides a one-step catalytic synthesis method for obtaining MXene two-dimensional materials with phosphorus, sulfur or selenium terminals. The present invention has universal applicability and is suitable for large-scale production applications. It is an efficient and economical synthesis method. The MXene material prepared by the present invention can also be applied in multiple technical fields.

[0004] In order to solve the above technical problems, the present invention relates to a method for one-step catalytic synthesis of MXene two-dimensional materials with phosphorus or sulfur or selenium terminals, comprising the following steps:

[0005] Step 1: Place the MAX phase (e.g., Ti3AlC2 powder), catalyst precursor (e.g., Br2 catalyst precursor CuBr2), and target terminal precursor (e.g., P / S / Se) in a sealed ampoule tube according to a certain molar ratio (Al: Br: P / S / Se = 1: 3: 2), wherein the catalyst precursor CuBr2 and the target terminal precursor (P / S / Se) need to be additionally placed in an inner-lined ampoule tube to isolate the MAX phase powder, the catalyst precursor, and the target terminal precursor, and vacuum seal the ampoule tube equipped with the inner-lined ampoule tube, and the vacuum degree is less than 5 Pa when sealing the tube;

[0006] Step 2: Place the vacuum-sealed ampoule tube of step 1 in a two-stage temperature-controlled tubular furnace, and place one end of the ampoule tube containing MAX phase Ti3AlC2 powder, Br2 catalyst precursor CuBr2 and target terminal precursor P / S / Se in the high temperature zone (600°C) and the other end in the low temperature zone (500°C). The heating rate is 10°C / min, the synthesis time is 6 hours, and the temperature is naturally lowered to room temperature after the reaction is completed.

[0007] Step 3: Cut the cooled ampoule tube obtained in step 2 to collect the MXene-P / S / Se powder with P / S / Se terminals obtained by synthesizing MAX phase Ti3AlC2 powder using Br2 catalyst.

[0008] The catalyst includes but is not limited to Br2, Cl2, HBr, HCl, the target terminal includes but is not limited to P, S, Se, the MAX phase includes but is not limited to Ti3AlC2, Ti2AlC, Ti3SiC2, Ti3GeC2, Ti3GaC2, Ti3InC2, Ti3SnC2 and non-Ti-based MAX phase.

[0009] Compared with the prior art, the present invention has the following beneficial effects:

[0010] The method for catalytic synthesis of MXene can directly obtain MXene powder with P / S / Se terminals from MAX phase powder without secondary reaction and subsequent treatment steps. Unlike the traditional two-step synthesis method (the first step is to synthesize MXene-Br / Cl with Br or Cl terminals by molten salt or gas phase, and the second step is to use salt containing target terminals, such as Li3P, Li2S, or gas phase method using P, H2S gas to replace terminal-Br / Cl to obtain the target product), this method directly converts MAX phase powder into MXene powder with target terminal by one-step catalysis, breaking through the limitation that the traditional method requires two steps, and its by-products are deposited in the low temperature zone through gas phase transportation, without the need to separate MXene and by-products, while simplifying the synthesis steps, avoiding the steps of removing by-products in other methods and the use of dangerous gases in traditional gas phase methods. This method is universal, and its essential principle is to use the difference in thermodynamic Gibbs free energy of reactions between different elements to drive different catalysts to catalyze different MAX phases to generate MXene with target terminals. The simple synthesis steps and wide application range make this method suitable for large-scale preparation, production and application of MXene with specific terminals. At the same time, different surface terminals will give MXene different properties, broadening the application range of MXene. This method provides a new catalytic synthesis concept and new insights into the synthesis strategy of MXene, which is universal. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 XRD patterns of MXene-P / S / Se powder and its precursor MAX phase Ti3AlC2 powder;

[0012] Figure 2 SEM image (a) and EDS analysis result (b) of MXene-P powder;

[0013] Figure 3 SEM image (a) and EDS analysis result (b) of MXene-S powder;

[0014] Figure 4 SEM image (a) and EDS analysis result (b) of MXene-Se powder;

[0015] Figure 5 Atomic-scale image of MXene-S. DETAILED DESCRIPTION

[0016] In order to further illustrate the present invention, the technical solutions provided by the present invention are described in detail below in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0017] Embodiment 1:

[0018] Br2 catalyst vapor-phase etching of MAX phase Ti3AlC2 powder to synthesize P-terminated MXene-P powder, the preparation steps are as follows:

[0019] Step 1: Place the MAX phase (e.g., Ti3AlC2 powder), the catalyst precursor (e.g., Br2 catalyst precursor CuBr2), and the target terminal precursor (e.g., P) in a sealed ampoule tube according to a certain molar ratio (Al:Br:P=1:3:2), wherein the catalyst precursor CuBr2 and the target terminal precursor (e.g., P) need to be additionally placed in an inner-lined ampoule tube to isolate the MAX phase powder, the catalyst precursor, and the target terminal precursor, and vacuum seal the ampoule tube equipped with the inner-lined ampoule tube, and the vacuum degree is less than 5Pa when sealing the tube;

[0020] Step 2: Place the vacuum-sealed ampoule tube of step 1 in a two-stage temperature-controlled tubular furnace, and place one end of the ampoule tube containing MAX phase Ti3AlC2 powder, Br2 catalyst precursor CuBr2 and target terminal precursor P in the high temperature zone (600°C) and the other end in the low temperature zone (500°C). The heating rate is 10°C / min, the synthesis time is 6 hours, and the temperature is naturally lowered to room temperature after the reaction is completed;

[0021] Step 3: Cut the cooled ampoule tube obtained in step 2 to collect the MXene-P powder with P terminal obtained by catalyzing the synthesis of MAX phase Ti3AlC2 powder using Br2 catalyst.

[0022] Embodiment 2:

[0023] The preparation process is basically the same as that in Example 1, the only difference is that in step one, the target terminal precursor is S; in step two, the MAX phase Ti3AlC2 powder, the Br2 catalyst precursor CuBr2 and one end of the target terminal precursor S are placed in a high temperature zone (600°C); in step three, the MXene-S powder with S terminal obtained by catalyzing the synthesis of the MAX phase Ti3AlC2 powder by the Br2 catalyst is collected.

[0024] Embodiment 3:

[0025] The preparation process is basically the same as that in Example 1, the only difference is that in step one, the target terminal precursor is Se; in step two, one end containing MAX phase Ti3AlC2 powder, Br2 catalyst precursor CuBr2 and target terminal precursor Se is placed in a high temperature zone (600°C); in step three, the MXene-Se powder with Se terminal obtained by catalyzing the synthesis of MAX phase Ti3AlC2 powder by Br2 catalyst is collected.

[0026] The MXene-P / S / Se powders prepared in Examples 1, 2, and 3 are Figure 1 The XRD patterns of MXene-P / S / Se powder and its precursor MAX phase Ti3AlC2 powder are shown. The XRD characteristic peaks of MAX phase Ti3AlC2 powder disappear after etching, indicating that the Al element is completely etched, and the (0002), (10-11), and (11-20) peaks of MXene-P / S / Se powder shift relative to Ti3AlC2, indicating that the presence of P / S / Se surface terminations changes the interlayer spacing between MXenes. Figure 2-4 In the microscopic SEM images and EDS analysis, MXene-P / S / Se presents a classic "accordion"-shaped separated layered structure. EDS elemental analysis shows the presence of P / S / Se elements, proving that P / S / Se successfully forms terminals. Figure 5 An atomic-scale image of MXene-S is shown, demonstrating the successful synthesis of MXene-S.

[0027] Embodiment 4:

[0028] The preparation process is basically the same as that in Example 1, the only difference is that in step 1, the catalyst is Cl2; in step 2, one end containing MAX phase Ti3AlC2 powder, Cl2 catalyst and target terminal precursor P or S or Se is placed in a high temperature zone (600°C); in step 3, MXene-P / S / Se powder with P or S or Se terminals is obtained by collecting MAX phase Ti3AlC2 powder and synthesizing it by Cl2 catalyst.

[0029] Embodiment 5:

[0030] The preparation process is basically the same as that in Example 1, the only difference is that in step 1, the catalyst is HCl; in step 2, one end containing MAX phase Ti3AlC2 powder, HCl catalyst and target terminal precursor P or S or Se is placed in a high temperature zone (600°C); in step 3, MXene-P / S / Se powder with P or S or Se terminals is obtained by collecting MAX phase Ti3AlC2 powder and synthesizing it by HCl catalyst.

[0031] Embodiment 6:

[0032] The preparation process is basically the same as that in Example 1, except that: in step 1, the catalyst is HBr; in step 2, one end containing MAX phase Ti3AlC2 powder, HBr catalyst and target terminal precursor P or S or Se is placed in a high temperature zone (600°C); in step 3, MXene-P / S / Se powder with P or S or Se terminal obtained by catalytic synthesis of MAX phase Ti3AlC2 powder by HBr catalyst is collected.

[0033] It can be concluded from the above embodiments that when prepared according to the process shown in the claims, MXene materials with different terminals can be synthesized by catalysis of different catalysts. The above embodiments mainly list different catalysts, mainly including Br2, Cl2, HBr, HCl, the target terminal includes but is not limited to P, As, S, Se, the precursor MAX phase includes but is not limited to Ti3AlC2, Ti3SiC2, and also includes Ti2AlC, Ti3GeC2, Ti3GaC2, Ti3InC2, Ti3SnC2 and non-Ti-based MAX phases.

[0034] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for catalytically synthesizing a MXene two-dimensional material having a target terminal, characterized in that: The following steps are involved: Step 1: placing the MAX phase, the catalyst precursor and the target terminal precursor in a vacuum-sealed ampoule tube according to a certain molar ratio, wherein the catalyst precursor and the target terminal precursor are placed in the inner-lined ampoule tube; Step 2: Control the temperature of both ends of the vacuum-sealed ampoule tube in step 1, wherein one end containing the MAX phase, the catalyst precursor and the target terminal precursor is set to 600°C, and the other end is set to 500°C; and the heating rate is set to 10°C / min, the synthesis time is 6 hours, and the temperature is naturally lowered to room temperature after the reaction is completed; Step 3: Cut the cooled ampoule tube obtained in step 2 to collect the catalytically synthesized MXene two-dimensional material with the target terminal.

2. The method according to claim 1, characterized in that: The MAX phase in step 1 includes a Ti-based MAX phase or a non-Ti-based MAX phase.

3. The method according to claim 2, characterized in that: The Ti-based MAX phase includes Ti3AlC2, Ti2AlC, Ti3SiC2, Ti3GeC2, Ti3GaC2, Ti3InC2 or Ti3SnC2.

4. The method according to claim 1, characterized in that: The catalyst in step 1 includes Br2, Cl2, HBr or HCl.

5. The method according to claim 1, characterized in that: The target terminal precursor in step 1 includes P, S, Se or As.

6. A MXene two-dimensional material with a target terminal prepared by the method according to any one of claims 1 to 5.

7. The MXene two-dimensional material with a target terminal according to claim 6, characterized in that: The MXene two-dimensional material with a target terminal includes: MXene-P with a P terminal, MXene-S with an S terminal, MXene-Se with a Se terminal, or MXene-As with an As terminal.

8. Application of the MXene two-dimensional material with target terminal according to claim 6 or 7 in battery electrodes, supercapacitor electrodes, magnetic shielding or catalytic materials.

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