A two-dimensional Ti3C2T x Material, method of preparation and use thereof

Abstract

The application discloses a two-dimensional Ti3C2T x material, a preparation method and application thereof, LiF is dissolved in HCl solution A to obtain solution B, Ti3AlC2 is added into the solution B to carry out etching reaction to obtain suspension C, solid-liquid separation is carried out for the first time to obtain a solid, NaBF4 is dissolved in HCl solution D to obtain solution E, the solid is added into the solution E to carry out hydrothermal reaction, and the solid phase obtained through second solid-liquid separation is the two-dimensional Ti3C2T x material. According to the preparation method, HF is generated by dissolving LiF in HCl solution to etch most of the Al layer of Ti3AlC2, then the obtained precipitated powder is added into solution E to carry out hydrothermal reaction, and the gasification water molecules generated under high temperature and high pressure and overflow gas product HF can effectively increase the layer spacing between Mxene materials and further etch the excess Al layer.

Description

TECHNICAL FIELD

[0001] The application relates to a two-dimensional Ti3C2T x material, a preparation method thereof and application, and belongs to the technical field of Mxene material preparation. BACKGROUND

[0002] Ti3C2T x is a kind of Mxene material, and is a kind of two-dimensional material emerging in recent years. It can be prepared by selectively etching the Al layer of the precursor Ti3AlC2. Since -OH, -F, -O and other hydrophilic groups and some defects are generated in the etching process, Ti3C2T x has a hydrophilic surface, abundant pi electrons and a large number of catalytically active sites, so that it has good performance in sensors, batteries, water purification, catalysis and electromagnetic shielding and many other fields.

[0003] At present, the main preparation methods of Ti3C2T x include a “top-down” etching method (HF direct etching method, in-situ HF solution etching method, molten fluorine salt etching method, etc.) and a “bottom-up” synthesis method (chemical vapor deposition, template method, etc.). In terms of maturity of the preparation process, the “top-down” etching method is still the mainstream preparation method of Mxene material. The HF direct etching method is to immerse the MAX phase in the HF solution, etch away the A atom layer, and obtain the layered Mxene. This method often has the following shortcomings: the nanosheets obtained by this method are still closely stacked together, and a special intercalating agent needs to be used to increase the spacing of the sheet layers and reduce the bonding force between the sheet layers, and the introduction of the intercalating agent increases the difficulty of impurity removal and affects the purity of the product. And HF as a strong corrosive agent has certain use hazards.

[0004] The in-situ HF solution method is the most commonly used method for preparing Ti3C2T x at present, which generally uses HF generated by the reaction of a fluorine-containing salt with hydrochloric acid to achieve the purpose of etching the MAX phase. The advantage of this method over the HF direct etching method is that the cations in the solution can act as intercalating agents during the etching process, so that additional intercalating agents do not need to be introduced. However, in this method, the in-situ HF content is low, the etching effect is poor, and the yield is low, so it is not suitable for large-scale industrial production.

[0005] For a material, factors such as preparation temperature, time and yield are necessary conditions for determining whether it can be produced on a large scale and whether it can be widely applied. However, so far, the preparation methods of Ti3C2T x materials reported have harsh conditions, such as long reaction time, poor product uniformity and high cost. The existing preparation methods greatly limit the development speed from the laboratory to the industrial production. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the first objective of this invention is to provide a two-dimensional Ti3C2T material with low energy consumption, high speed, high yield, and large specific surface area. x Material preparation methods.

[0007] The second objective of this invention is to provide a two-dimensional Ti3C2T prepared by the above-described preparation method. x Material.

[0008] A third objective of this invention is to provide a two-dimensional Ti3C2T prepared by the above-described preparation method. x Application of materials.

[0009] The specific technical solution adopted in this invention is as follows:

[0010] This invention provides a two-dimensional Ti3C2T x The material is prepared by dissolving LiF in HCl solution A to obtain solution B. Ti3AlC2 is added to solution B, followed by an etching reaction to obtain suspension C. A first solid-liquid separation yields a solid. NaBF4 is dissolved in HCl solution D to obtain solution E. The solid is added to solution E, followed by a hydrothermal reaction and a second solid-liquid separation. The resulting solid phase is the two-dimensional Ti3C2T. x Material.

[0011] The preparation method of the present invention first involves dissolving LiF in an HCl solution to generate HF, which etches away most of the Al layer of Ti3AlC2. Then, the resulting precipitated powder is added to solution E to carry out a hydrothermal reaction. The vaporized water molecules generated by high temperature and high pressure and the overflow gas product HF can effectively increase the interlayer spacing between Mxene materials and further etch away the excess Al layer.

[0012] In existing technologies, Ti3C2T is used. x The preparation of this material typically involves using the supernatant liquid from centrifugation after HF etching, resulting in extremely low yield and incomplete lamellar opening. However, this invention, after the initial etching pretreatment, collects all the solid phase and then performs a second step of hydrothermal etching. This second step further etches away the incompletely etched Ti3AlC2, fully opening the lamellar structure and ultimately obtaining a two-dimensional accordion-like Ti3C2T structure. x Material.

[0013] In a preferred embodiment, the concentration of HCl in the HCl solution A is 9-9.25 mol / L.

[0014] In actual operation, HCl solution A is obtained by dissolving concentrated HCl in deionized water.

[0015] Preferably, the concentration of LiF in solution B is 3-3.25 mol / L.

[0016] Preferably, Ti3AlC2 is added to solution B under stirring.

[0017] Preferably, the solid-liquid mass-volume ratio of Ti3AlC2 to HCl solution A is 0.5-0.55 g:10 mL.

[0018] Preferably, the etching reaction is carried out under stirring, the temperature of the etching reaction is 35-35.2℃, the time of the etching reaction is 12-12.5 h, and the stirring speed during the etching reaction is 300-500 r / min.

[0019] Preferably, the first solid-liquid separation is by centrifugation, and the obtained lower layer is dried to obtain a precipitate powder after the suspension C is washed with deionized water and anhydrous ethanol.

[0020] Preferably, the concentration of HCl in HCl solution D is 1-1.2 mol / L. The inventors have found that controlling the concentration of HCl in the above range can ensure that the etching is complete after two-step processing.

[0021] In actual operation, HCl solution D is obtained by dissolving concentrated HCl in deionized water.

[0022] Preferably, the concentration of NaBF4 in solution E is 0.9-1.1 mmol / L. Controlling the concentration of NaBF4 in the above range can ensure that the second etching is complete, and two-dimensional Ti3C2T x materials with large specific surface area and good morphology are obtained.

[0023] Preferably, the solid is added to solution E under stirring, and after the addition is completed, the stirring is continued at a speed of 300-500 r / min for 1-1.2 h.

[0024] Preferably, the solid-liquid mass-volume ratio of the solid to HCl solution D is 0.45-0.55 g:60 mL.

[0025] Preferably, the temperature of the hydrothermal reaction is 80-120℃, preferably 105-120℃, and the time of the hydrothermal reaction is 12-24 h.

[0026] In the present application, NaBF4 and HCl are used as raw materials, and H2 is generated during the reaction to act as a protective gas to prevent oxidation, so the reaction does not need to be carried out in a protective atmosphere, and can be carried out at a higher temperature. Therefore, during the hydrothermal reaction, on the one hand, the intercalation of NaBF4 to the reactants, and on the other hand, the gasification of water molecules and the overflow of gas product HF generated during the hydrothermal reaction at high temperature and high pressure effectively increase the interlayer spacing between Mxene materials, so that the Ti3C2Tx sheet layer is fully opened, and finally a two-dimensional Ti3C2T x material with a two-dimensional accordion structure is obtained. x Of course, the temperature of the hydrothermal reaction also needs to be effectively controlled. If the temperature is too high, oxidation will still occur, and if the temperature is too low, the Ti3C2T x sheet layer will not be fully opened.

[0027] In a preferred embodiment, the solid phase obtained by the second solid-liquid separation is washed with deionized water and anhydrous ethanol, and then dried at 40-60°C for 6-12h to obtain the two-dimensional Ti3C2T x material.

[0028] The present application also provides a two-dimensional Ti3C2T x material prepared by the above preparation method.

[0029] The present application also provides a two-dimensional Ti3C2T x material prepared by the above preparation method.

[0030] The present application also provides a two-dimensional Ti3C2T x material prepared by the above preparation method. x The two-dimensional Ti3C2T x material has a two-dimensional accordion structure, and the Ti3C2T x sheet layer is fully opened, and exhibits significantly enhanced gas sensitivity to NH3.

[0031] The present application has the following advantages and effects:

[0032] (1) In the preparation process: the combination of solution etching pretreatment and hydrothermal reaction is the key preparation process flow in the present application. The solution etching pretreatment can etch away most of the Al layer, and the gasification of water molecules and the overflow of gas product HF generated during the hydrothermal reaction at high temperature and high pressure can effectively increase the interlayer spacing between Mxene materials and further etch away the excess Al layer. Compared with other preparation methods, this method has the advantages of simple process, high yield, controllable cost, etc. And the Ti3C2Tx prepared by the present application has a clear layered structure, high purity, large specific surface area, many surface active groups, and good crystal structure, and has considerable application prospects in the fields of batteries, photocatalysis, gas sensors, etc. The present application will help to promote the development of Ti3C2T x(1) The development from laboratory to industrial production application. (2) In the gas sensing performance: under the condition of 100 ppm gas concentration and 25℃, the Ti3C2T x In the response sensitivity test of different gases (including NH3, C7H8, CH3OH, C3H6O, CH3CHO, C2H5OH), the sensitivity to NH3 was obviously enhanced (31.4%), and the response / recovery time to NH3 was 45 / 357s. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 XRD patterns of pure Ti3AlC2, Ti3C2Tx and all examples and comparative examples of the present application.

[0034] Figure 2 Ti3C2T x SEM images of the materials.

[0035] Figure 3 Ti3C2T x Comparison chart of response values of the materials to 100 ppm different gases at 25℃ and 40% relative humidity;

[0036] Figure 4 Ti3C2T x Response / recovery curves of the materials to 100 ppm ammonia at 25℃ and 40% relative humidity. DETAILED DESCRIPTION

[0037] The Ti3C2T x The preparation of functional materials is further illustrated.

[0038] Example 1

[0039] (1) First, 7.5 ml of concentrated HCl was dissolved in 2.5 ml of deionized water to obtain 10 ml (9M HCl) of clear solution A;

[0040] (2) Then, 0.8 g of LiF was weighed and dissolved in solution A to prepare colorless transparent solution B;

[0041] (3) 0.5 g of Ti3AlC2 was weighed and added to the above solution B within 10 min, and constant temperature stirring was carried out at 35℃ and 350 r / min for 24 h to obtain suspension C;

[0042] (4) Suspension C was centrifuged with a large amount of deionized water and anhydrous ethanol at a rotation speed of 3500 r / min, and then the obtained solid was transferred to a vacuum drying box at 60℃ for drying for 24 h to obtain solid A;

[0043] (5) 5.0 ml of concentrated HC1 was dissolved in 55.0 ml of deionized water to obtain 60 ml (1 M HC1) of clear solution D;

[0044] (6) 0.64 g of NaBF4 was added to solution D to prepare colorless transparent solution E;

[0045] (7) 0.5 g of solid A was taken into solution E, and stirred for 1 h. The whole precursor solution was transferred into a 100 ml high-pressure reactor, and reacted at 80 °C for 12 h. After the hydrothermal reaction was completed, it was cooled to room temperature, and centrifuged with a large amount of deionized water and anhydrous ethanol. The centrifuged sample was transferred to a vacuum drying box at 60 °C for drying for 24 h. The solid sample was then fully ground to obtain Ti3C2T x powder.

[0046] Example 2

[0047] (1) First, 7.5 ml of concentrated HC1 was dissolved in 2.5 ml of deionized water to obtain 10 ml (9 M HC1) of clear solution A;

[0048] (2) Then, 0.8 g of LiF was weighed and dissolved in solution A to prepare colorless transparent solution B;

[0049] (3) 0.5 g of Ti3AlC2 was weighed and added to the above solution B within 10 min, and stirred at 35 °C and 350 r / min for 24 h to obtain suspension C;

[0050] (4) Suspension C was centrifuged with a large amount of deionized water and anhydrous ethanol at a speed of 3500 r / min, and then the obtained solid was transferred to a vacuum drying box at 60 °C for drying for 24 h to obtain solid A;

[0051] (5) 5.0 ml of concentrated HC1 was dissolved in 55.0 ml of deionized water to obtain 60 ml (1 M HC1) of clear solution D;

[0052] (6) 0.64 g of NaBF4 was added to solution D to prepare colorless transparent solution E;

[0053] (7) 0.5 g of solid A was taken into solution E, and stirred for 1 h. The whole precursor solution was transferred into a 100 ml high-pressure reactor, and reacted at 100 °C for 12 h. After the hydrothermal reaction was completed, it was cooled to room temperature, and centrifuged with a large amount of deionized water and anhydrous ethanol. The centrifuged sample was transferred to a vacuum drying box at 60 °C for drying for 24 h. The solid sample was then fully ground to obtain Ti3C2T x powder.

[0054] Example 3

[0055] (1) First, 7.5 ml of concentrated HCl was dissolved in 2.5 ml of deionized water to obtain a clear solution A of 10 ml (9M HCl);

[0056] (2) Then, 0.8 g of LiF was weighed and dissolved in solution A to prepare a colorless and transparent solution B;

[0057] (3) 0.5 g of Ti3AlC2 was weighed and added to the above-mentioned solution B within 10 min, and constant temperature stirring was carried out at 350 r / min at 35°C for 24 h to obtain a suspension C;

[0058] (4) The suspension C was washed by centrifugation with a large amount of deionized water and anhydrous ethanol at a rotation speed of 3500 r / min, and then the obtained solid was transferred to a vacuum drying oven at 60°C for drying for 24 h to obtain a solid A;

[0059] (5) 5.0 ml of concentrated HCl was dissolved in 55.0 ml of deionized water to obtain a clear solution D of 60 ml (1M HCl);

[0060] (6) 0.64 g of NaBF4 was added to solution D to prepare a colorless and transparent solution E;

[0061] (7) 0.5 g of solid A was added to solution E, and stirred thoroughly for 1 h, and then all the precursor solution was transferred to a 100 ml high-pressure reaction kettle for reaction at 120°C for 12 h. After the hydrothermal reaction was completed, it was cooled to room temperature, washed by centrifugation with a large amount of deionized water and anhydrous ethanol, and then the centrifuged sample was transferred to a vacuum drying oven at 60°C for drying for 24 h. The solid sample was thoroughly ground to obtain Ti3C2T x powder.

[0062] Example 4

[0063] (1) First, 7.5 ml of concentrated HCl was dissolved in 2.5 ml of deionized water to obtain a clear solution A of 10 ml (9M HCl);

[0064] (2) Then, 0.8 g of LiF was weighed and dissolved in solution A to prepare a colorless and transparent solution B;

[0065] (3) 0.5 g of Ti3AlC2 was weighed and added to the above-mentioned solution B within 10 min, and constant temperature stirring was carried out at 350 r / min at 35°C for 24 h to obtain a suspension C;

[0066] (4) The suspension C was washed by centrifugation with large amount of deionized water and absolute ethanol at 3500 r / min, and then the obtained solid was transferred into a vacuum drying oven at 60°C for drying for 24 h to obtain solid A;

[0067] (5) 5.0 ml of concentrated HCl was dissolved in 55.0 ml of deionized water to obtain 60 ml (1M HCl) of clear solution D;

[0068] (6) 0.64 g of NaBF4 was added to solution D to prepare colorless transparent solution E;

[0069] (7) 0.5 g of solid A was taken and added to solution E, and stirred for 1 h, and then the whole precursor solution was transferred into a 100 ml high-pressure reactor for reaction at 140°C for 12 h. After the hydrothermal reaction was completed, it was cooled to room temperature, and then washed by centrifugation with large amount of deionized water and absolute ethanol, and then the centrifuged sample was transferred into a vacuum drying oven at 60°C for drying for 24 h, and then the solid sample was fully ground to obtain Ti3C2T x powder.

[0070] Comparative Example 1

[0071] (1) First, 7.5 ml of concentrated HCl was dissolved in 2.5 ml of deionized water to obtain 10 ml (9M HCl) of clear solution A;

[0072] (2) Then, 0.8 g of LiF was weighed and dissolved in solution A to prepare colorless transparent solution B;

[0073] (3) 0.5 g of Ti3AlC2 was weighed and slowly added to the above solution B, and then stirred at 25°C at a rotation speed of 350 r / min for 24 h to obtain suspension C;

[0074] (4) The suspension C was washed by centrifugation with large amount of deionized water and absolute ethanol at 3500 r / min, and then the obtained solid was transferred into a vacuum drying oven at 60°C for drying for 24 h to obtain solid mixture Ti3C2T x / Ti3AlC2.

[0075] Performance detection

[0076] Figure 1 For the XRD patterns of pure Ti3AlC2, Ti3C2Tx and all examples and comparative examples of the present application, the diffraction peak at 9.3° can be indexed as the (002) crystal face of Ti3C2T x (JCPDS #52-0875). It can be seen from the figure that the (002) diffraction peak of the material has high intensity, indicating that Al is etched off and the interlayer spacing is increased, which confirms the high-purity Ti3C2T xSuccessful preparation.

[0077] Figure 2 The high-purity Ti3C2T obtained in Example 3 x SEM image of the material. The image shows that the material has a two-dimensional accordion-like structure, approximately 6 μm in size, with a lamellar spacing of 100-200 nm. The material exhibits clear layering and a relatively smooth surface.

[0078] Figure 3 This is a gas selectivity test for Example 3. The material obtained in Example 3 was ground into a paste by adding ethanol, and then coated onto finger electrodes to form a gas-sensitive element. The gas-sensitive performance of the sample was evaluated using a high-precision gas-sensitive testing instrument (WS-30B). The test voltage in this patent is 5V. The operating temperature is 25°C, which can be changed by adjusting the heating voltage. The gas concentration is 100ppm, controlled by the amount of gas injected. This can be expressed using the formula S = I... a / I g =R g / R a The sensor's response value is calculated using the following methods: Ig is the current passing through the sensor in the target gas, Ia is the current passing through the sensor in the air, Ra is the sensor's resistance in the air, and Rg is the sensor's resistance in the target gas. After the target gas is added, the response time is defined as the time required for the initial response value to reach 90% of the stable response, and the recovery time is defined as the time required for the sensor to recover to 90% of its initial value. Figure 3 It can be seen that, among the six gases tested at room temperature (100 ppm each of ammonia, toluene, acetone, ethanol, methanol, and acetaldehyde), the material exhibits excellent selectivity for ammonia.

[0079] Figure 4 The figure shows the response / recovery curves of Example 3 to 100 ppm ammonia. As can be seen from the figure, the response / recovery times of the material are 45 / 357 s, respectively.

[0080] Finally, it should be noted that the above examples are merely specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments and many variations are possible. All variations that can be directly derived or conceived by those skilled in the art from the disclosure of this invention should be considered within the scope of protection of this invention.

Claims

1. A two-dimensional Ti3C2T x Method for the preparation of a material, characterized in that: Dissolving LiF in HCl solution A to obtain solution B, adding Ti3AlC2 into solution B, etching reaction to obtain suspension C, first solid-liquid separation to obtain solid, dissolving NaBF4 in HCl solution D to obtain solution E, adding the solid into solution E, hydrothermal reaction, second solid-liquid separation, and the obtained solid phase is two-dimensional Ti3C2T x material; The etching reaction is carried out under stirring, the temperature of the etching reaction is 35-35.2℃, the time of the etching reaction is 12-12.5h, and the stirring speed during the etching reaction is 300-500r / min; In the HCl solution D, the concentration of HCl is 1-1.2mol / L; In the solution E, the concentration of NaBF4 is 0.9-1.1mmol / L; The temperature of the hydrothermal reaction is 80-120℃, and the time of the hydrothermal reaction is 12-24h.

2. A two-dimensional Ti3C2T x Method for the preparation of a material, characterized in that: In the HCl solution A, the concentration of HCl is 9-9.25mol / L; In the solution B, the concentration of LiF is 3-3.25mol / L.

3. A two-dimensional Ti3C2T x Method for the preparation of a material, characterized in that: The Ti3AlC2 is added into the solution B under stirring; The solid-liquid mass-volume ratio of the Ti3AlC2 to the HCl solution A is 0.5-0.55g:10mL.

4. A two-dimensional Ti3C2T x Method for the preparation of a material, characterized in that: The first solid-liquid separation is carried out by centrifugation, and the obtained lower layer is dried to obtain a precipitate powder.

5. A two-dimensional Ti3C2T x Method for the preparation of a material, characterized in that: The solid is added into the solution E under stirring, and after the addition is completed, the stirring is continued at a speed of 300-500r / min for 1h-1.2h; The solid-liquid mass-volume ratio of the solid to the HCl solution D is 0.45-0.55g:60mL.

6. A two-dimensional Ti3C2T x Method for the preparation of a material, characterized in that: The solid phase obtained by the second solid-liquid separation is washed by deionized water and anhydrous ethanol, and then dried at 40-60°C for 6-12h to obtain two-dimensional Ti3C2T x Material.

7. The two-dimensional Ti3C2T x material produced by the method of any one of claims 1-6. x material.

8. The two-dimensional Ti3C2T x prepared by the preparation method according to any one of claims 1-6. x Use of the material, characterized in that: The two-dimensional Ti3C2T x The material was made into a gas sensitive element for detecting NH3.

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