Preparation and application of a niobium-titanium two-dimensional transition metal carbide

Abstract

The present invention discloses a preparation and application of a niobium-titanium two-dimensional transition metal carbide, belonging to the technical field of two-dimensional materials. The present invention prepares (Nb 1‑y Ti y )4AlC3MAX phase solid solution, which was then crushed, etched and intercalated to obtain niobium-titanium two-dimensional transition metal carbide (Nb 1‑y Ti y )4C3T x , where 0 <y≤0.4,T x As the surface end group, the obtained niobium-titanium two-dimensional transition metal carbide has excellent rate performance.

Description

Technical Field

[0001] The invention relates to preparation and application of niobium-titanium two-dimensional transition metal carbide, belonging to the technical field of two-dimensional materials. Background Art

[0002] Since the discovery of graphene in 2004, two-dimensional (2D) materials have attracted widespread attention in scientific research and industrial applications due to their unique physical and chemical properties. MXene is an emerging two-dimensional transition metal carbonitride, which is usually synthesized by selectively removing the A element layer from the MAX phase precursor. In the nomenclature of MXene, M represents transition metals such as titanium (Ti), vanadium (V), tantalum (Ta), zirconium (Zr), niobium (Nb), molybdenum (Mo), etc., while X represents carbon and / or nitrogen elements. MXene not only has a variety of surface functional groups, but also has high electrical conductivity, which makes it show great application potential in many fields such as energy storage, catalysis, electromagnetic interference shielding, transparent conductive films, and seawater desalination.

[0003] Ti3C2T x As the first member of the MXene family to be synthesized, it is also one of the most widely studied MXene materials. Due to its unique structure, Ti3C2T x MXene has a large specific surface area and its surface can undergo rapid redox reactions, which makes it have the characteristics of double-layer capacitance and pseudocapacitance at the same time, showing a high specific capacitance value, and has significant application prospects in the field of supercapacitors. Niobium has a variety of oxidation states (+2, +3, +4, +5), so MXene containing niobium also exhibits excellent pseudocapacitance performance. For example, Nb4C3T x It exhibits a high specific capacitance, but its rate performance is relatively low. In order to further improve the electrochemical performance of niobium-based MXene, it is a simple and effective method to dope other elements at the M or X position of MXene. Given that niobium (Nb) and titanium (Ti) are close in position in the periodic table and their atomic radii are similar (the atomic radius of Nb is 147 picometers and that of Ti is 146 picometers), the preparation of (Nb 1-y Ti y )4AlC3 MAX phase solid solution, which was then etched to obtain niobium-titanium two-dimensional transition metal carbide (Nb 1-y Ti y )4C3T x It is one of the effective methods to improve the capacitance performance of niobium-based MXene. Summary of the invention

[0004] The present invention provides a method for preparing niobium-titanium two-dimensional transition metal carbide, wherein the method comprises sintering a mixture of niobium powder, titanium powder, aluminum powder and elemental carbon to prepare (Nb 1-yTi y )4AlC3 MAX phase solid solution, which was then crushed, etched and intercalated to obtain niobium-titanium two-dimensional transition metal carbide (Nb 1-y Ti y )4C3T x , where 0 <y≤0.4,T x It is a surface end group, which can be one or more of oxygen, hydroxyl, fluorine, and halogen.

[0005] In one embodiment of the present invention, the preparation (Nb 1-y Ti y )The sintering temperature of 4AlC3 MAX phase solid solution is 1200-1900°C, and the sintering time is 0.5-24h, and further, preferably 2-5h.

[0006] In one embodiment of the present invention, for preparing (Nb 1-y Ti y ) In the raw materials of 4AlC3 MAX phase solid solution, the molar number of titanium powder is 1 to 45% of the sum of the molar numbers of titanium powder and niobium powder, the total molar number of niobium powder and titanium powder is 2.5 to 4.5 times the molar number of aluminum powder, and the molar number of elemental carbon is 1.5 to 3.5 times that of aluminum powder.

[0007] In one embodiment of the present invention, for preparing (Nb 1-y Ti y ) In the raw materials of 4AlC3 MAX phase solid solution, when y>0.3, 1-10% of the molar mass of Nb powder needs to be added to replace the corresponding proportion of Nb powder.

[0008] In one embodiment of the present invention, hydrofluoric acid, a mixture of hydrofluoric acid and an inorganic protonic acid, a mixture of a fluoride salt and an inorganic protonic acid, ammonium bifluoride, or a molten salt is used as an etchant for etching the MAX phase.

[0009] In one embodiment of the present invention, the inorganic protonic acid is one or more of hydrochloric acid, sulfuric acid, nitric acid, fluoroboric acid, and phosphoric acid.

[0010] In one embodiment of the present invention, the mass concentration of the etchant is ≥20%.

[0011] In one embodiment of the present invention, the intercalant used is an aqueous solution of tetraalkylammonium hydroxide, and the alkyl group of the tetraalkylammonium hydroxide is methyl, ethyl, propyl, butyl or a combination thereof.

[0012] In one embodiment of the present invention, the mass concentration of tetraalkylammonium hydroxide in the aqueous solution of the intercalant is 5 to 80 wt %.

[0013] The present invention provides niobium-titanium two-dimensional transition metal carbide prepared by the above method.

[0014] The present invention also provides the application of the above-mentioned niobium-titanium two-dimensional transition metal carbide in the fields of supercapacitors, lithium-ion batteries, electromagnetic shielding and electrocatalysis.

[0015] Beneficial effects of the present invention:

[0016] The present invention provides a method for simply and effectively preparing niobium-titanium 413 phase MAX solid solution and corresponding MXene. The MAX phase solid solution can be prepared by high-temperature sintering, and then niobium-titanium two-dimensional transition metal carbide is prepared by etching and intercalation. Compared with pure niobium carbide MXene, niobium-titanium two-dimensional transition metal carbide has better rate performance when used as a supercapacitor electrode material. It can be used in the preparation of supercapacitors, lithium-ion batteries, electromagnetic shielding and electrocatalysis, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 XRD patterns of all MAX phases obtained in Examples 1, 2 and Comparative Example 1.

[0018] Figure 2 XRD patterns of all MXenes obtained in Examples 1, 2 and Comparative Example 1.

[0019] Figure 3 The (Nb obtained in Example 1 0.7 Ti 0.3 )4C3T x Cyclic voltammetry curves of MXene.

[0020] Figure 4 is obtained in Example 2 (Nb 0.6 Ti 0.4 )4C3T x Cyclic voltammetry curves of MXene.

[0021] Figure 5 Nb4C3T obtained in Comparative Example 1 x Cyclic voltammetry curves of MXene. DETAILED DESCRIPTION

[0022] The technical solution of the present invention is described in detail below through specific embodiments.

[0023] Example 1

[0024] (Nb 0.7 Ti 0.3) Preparation of 4AlC3 MAX phase: The raw materials were sealed and ball-milled in a polyethylene jar at a molar ratio of (Nb+Ti):Al:C=4:1.5:2.7 for 24 hours, wherein the molar ratio of Nb to Ti was 0.7:0.3. The ball-milled powder was placed in an alumina crucible and then in a tubular furnace, where argon was passed for 1 hour. Subsequently, the temperature was raised to 1650°C at a rate of 5°C / min under flowing Ar and maintained for 5 hours, then cooled to room temperature. The black matter on the surface of the obtained sample was removed and the sample was crushed into powder. The powder was poured into 9mol / LHCl (1mL / g) and stirred at room temperature for 8 hours. The powder was washed to neutrality by centrifugation at 5000r / min for 5 minutes and then transferred to a vacuum ball mill for 24 hours after drying. The powder was characterized by XRD, and its spectrum is shown in Figure 1 There are basically no 312 phase and 211 phase impurities in the figure, indicating that a relatively pure 413 phase MAX phase solid solution has been successfully synthesized.

[0025] In a 500 mL polytetrafluoroethylene bottle, a polytetrafluoroethylene-coated magnet, 54 mL of deionized water, 120 mL of 36% HCl solution, and 26 mL of 40% HF solution were added in sequence and stirred at room temperature for 24 hours. 0.7 Ti 0.3 )4AlC3 powder was uniformly and slowly added to the above etching solution at room temperature, and stirred for 5 min with a magnetic bar coated with polytetrafluoroethylene, and then placed in a 50°C oil bath and stirred for 96 hours, and then washed with deionized water and centrifuged (each washing was 5 minutes at 6500 rpm) until the pH reached about 7. The centrifugal precipitation was multilayer (Nb 0.7 Ti 0.3 )4C3T x .

[0026] The multilayer (Nb 0.7 Ti 0.3 )4C3T x Place it in 20mL 25wt% TMAOH solution and stir at 35℃ for 24h. Then divide the product evenly into 12 portions and pour them into 50mL centrifuge tubes. Add deionized water and wash by centrifugation until the pH value is close to 7. Then add deionized water to the centrifugal precipitate and concentrate it in a centrifuge tube and place it in an ultrasonic machine for ice bath ultrasonication for 6min. Finally, centrifuge the ultrasonicated sample at 3500r / min for 20min and collect the upper black liquid, i.e., the few-layer Nb4C3Tx dispersion.

[0027] The single layer (Nb 0.7 Ti 0.3 )4C3T x The MXene dispersion was vacuum filtered and dried at room temperature to obtain (Nb 0.7 Ti 0.3 )4C3Tx MXene film. The film was characterized by XRD, and its spectrum is shown in Figure 2 After etching, the characteristic peaks of the MAX phase and most of the diffraction peaks disappeared, indicating that the Al layer was successfully selectively etched and transformed into a 2D layered structure. The (002) peak of the sample is obvious, indicating that the obtained material is a two-dimensional material.

[0028] Dilute the shaken 60wt% PTFE emulsion with deionized water to a 5wt% emulsion. Then, take 1000mg of 5wt% PTFE emulsion in a beaker, add 100mg acetylene black and 100mg graphite, and stir at room temperature for 4 hours on a stirring table. Place the stirred sample in a 100℃ beaker and dry for 6 hours. Take out the sample, place it on a clean and smooth HDPE plate and add a small amount of ethanol, roll and fold it with a glass rod, and wait for the sample to become a flexible film, which is a carbon film, used as a counter electrode in electrochemical testing.

[0029] The flexibility (Nb 0.7 Ti 0.3 )4C3T x The MXene film was cut into discs for electrochemical testing. The overcapacitive activated carbon membrane was used as the counter electrode, the Hg / Hg2SO4 electrode was used as the reference electrode, Celgard3501 was used as the diaphragm, and the electrolyte was 3 mol / L H2SO4. The three-electrode Swagelok cell was assembled for cyclic voltammetry (CV) testing. The CV curves are shown in Figure 3 From the figure, we can calculate that at 5mV / s, (Nb 0.7 Ti 0.3 )4C3T x The capacitance is 299.7F / g. When the scan rate increases to 1000mV / s, the capacitance retention rate is 62.92%, which is much higher than that of Nb4C3T in Comparative Example 1. x 13.88%.

[0030] Example 2

[0031] (Nb 0.6 Ti 0.4 )4AlC3 MAX phase was prepared in the same manner as in Example 1, except that the raw material molar ratio was as follows: Nb:Nb2O5:Ti:Al:C=2.85:0.075:2:1.2:3.5. MAX phase powder was prepared in the same manner as in Example 1, and its XRD pattern is shown in FIG. Figure 1 , and MXene film was prepared, XRD spectrum is shown in Figure 2 There are basically no 312 phase and 211 phase impurities in the figure, indicating that a relatively pure 413 phase MAX phase solid solution has been successfully synthesized. The electrochemical test was carried out under the same conditions as in Example 1, and the CV curve is shown in FIG. Figure 4 From the figure, we can calculate that at 5mV / s, (Nb 0.6 Ti 0.4 The capacitance of 4C3Tx is 244.9F / g. When the scan rate is increased to 1000mV / s, its capacitance retention rate is 68.38%, which is much higher than that of Nb4C3T in the comparative example. x 13.88%.

[0032] Comparative Example 1

[0033] The preparation method of Nb4AlC3 MAX phase is the same as that of Example 1, except that the molar ratio of the raw materials during its preparation is Nb:Al:C=4:1.5:2.7. The MAX phase and MXene film are prepared by the same method as in Example 1, and their XRD spectra are shown in FIG. Figure 1 and 2 The electrochemical test was carried out under the same conditions as in Example 1, and the CV curve is shown in Figure 5 From the figure, we can calculate that at 5mV / s, (Nb 0.6 Ti 0.4 )The capacitance of 4C3Tx is 295.8F / g, and its capacitance retention rate is 13.88% when the scan rate increases to 1000mV / s.

Claims

1. A method for preparing niobium-titanium two-dimensional transition metal carbide, characterized in that: The mixture of niobium powder, titanium powder, aluminum powder and elemental carbon was sintered to prepare (Nb 1-y Ti y )4AlC3 MAX phase solid solution, which was then crushed, etched and intercalated to obtain niobium-titanium two-dimensional transition metal carbide (Nb 1-y Ti y )4C3T x ; Among them, 0 <y≤0.4,T x Surface end groups.

2. The method for preparing niobium-titanium two-dimensional transition metal carbide according to claim 1, characterized in that: Preparation (Nb 1-y Ti y )The sintering temperature of 4AlC3 MAX phase solid solution is 1200-1900℃, and the sintering time is 0.5-24h.

3. The method for preparing niobium-titanium two-dimensional transition metal carbide according to claim 1, characterized in that: For the preparation of (Nb 1-y Ti y ) In the raw materials of the 4AlC3 MAX phase solid solution, the molar number of titanium powder is 1 to 45% of the sum of the molar numbers of titanium powder and niobium powder; the total molar number of niobium powder and titanium powder is 2.5 to 4.5 times the molar number of aluminum powder; and the molar number of elemental carbon is 1.5 to 3.5 times that of aluminum powder.

4. The method for preparing niobium-titanium two-dimensional transition metal carbide according to claim 1, characterized in that: For the preparation of (Nb 1-y Ti y ) In the raw material of 4AlC3 MAX phase solid solution, when y>0.3, 1-10% of the molar mass of niobium powder needs to be added to replace the corresponding proportion of Nb powder.

5. The method for preparing niobium-titanium two-dimensional transition metal carbide according to claim 1, characterized in that: Hydrofluoric acid, a mixture of hydrofluoric acid and an inorganic protonic acid, a mixture of a fluoride salt and an inorganic protonic acid, ammonium bifluoride, or a molten salt is used as an etchant for etching the MAX phase.

6. The method for preparing niobium-titanium two-dimensional transition metal carbide according to claim 5, characterized in that: The inorganic protonic acid is one or more of hydrochloric acid, sulfuric acid, nitric acid and fluoroboric acid.

7. The method for preparing niobium-titanium two-dimensional transition metal carbide according to claim 5, characterized in that: The mass concentration of the etchant used is ≥20%.

8. The method for preparing niobium-titanium two-dimensional transition metal carbide according to claim 1, characterized in that: The intercalation agent used for intercalation is a tetraalkylammonium hydroxide aqueous solution, the alkyl group of the tetraalkylammonium hydroxide is methyl, ethyl, propyl, butyl or a combination thereof; the mass concentration of the tetraalkylammonium hydroxide aqueous solution is 5-80%.

9. The niobium-titanium two-dimensional transition metal carbide prepared by the method according to any one of claims 1 to 8.

10. Application of the niobium-titanium two-dimensional transition metal carbide according to claim 9 in the fields of supercapacitors, lithium-ion batteries, electromagnetic shielding and electrocatalysis.

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