A method for preparing accordion-shaped MXene materials under safe and mild reaction conditions

Abstract

A method for preparing accordion-shaped MXene materials under safe and mild reaction conditions belongs to the field of inorganic nanomaterial preparation. A near-neutral etching solution prepared with formic acid and sodium fluoride is used, followed by treatment under water bath heating for a certain period, and then further removal of reaction byproducts and impurities by phosphoric acid. Finally, the supernatant is washed with deionized water until it is neutral, thus successfully preparing the accordion-shaped MXene material. The advantages are that it completely abandons the high-risk etching agents such as hydrofluoric acid used in traditional processes, and innovatively uses a low-toxicity, weakly corrosive composite etching system as the reaction core. This composite system can efficiently etch away the A layer (e.g., aluminum layer) in the MAX phase precursor through synergistic effects, while effectively avoiding the safety risks and environmental pressures brought about by traditional etching agents. It is low-cost, easy to procure, store, and transport, providing strong support for large-scale production.

Description

Technical Field

[0001] This invention belongs to the field of inorganic nanomaterial preparation, specifically relating to a method for preparing accordion-shaped MXene materials under safe and mild reaction conditions. Background Technology

[0002] Layered transition metal carbides / nitrides (MXenes) possess high electrical conductivity, excellent mechanical properties, and tunable interlayer structures, showing broad application prospects in energy storage devices, catalysis, and flexible electronics. MXenes are generally made using M... n+1 X n T x Indicates (n=1~3), where M represents transition metals such as Ti, Hf, Zr, Nb, and Cr; X refers to C or N; T x Represents the OH on its surface - F - O 2- Surface functional groups. MXene materials are generally derived from M n+1 AX n Ceramics (abbreviated as MAX phase, n=1~3), where M represents a transition metal element, A represents a main group element, and X represents C or N. Among them, accordion-shaped MXene, due to its unique wrinkled layered structure, possesses a larger specific surface area and controllable interlayer channels, which can further improve ion transport efficiency and loading capacity, becoming an important direction for the functional optimization of MXene materials. Accordion-shaped MXene materials have shown irreplaceable application potential in energy storage devices, catalytic reactions, sensors, and other fields, and have become a research hotspot in the field of advanced functional materials.

[0003] Currently, the preparation of accordion-shaped MXenes is mostly based on traditional etching processes: using hydrofluoric acid (HF) as an etchant to peel off the A layer (such as Al) in the MAX phase ceramic, and then achieving interlayer separation through ultrasonic dispersion or centrifugation. However, this process poses significant safety and environmental risks: HF is highly corrosive and toxic, easily causing skin burns and respiratory damage to operators, and the waste liquid is difficult to treat, easily causing soil and water pollution, which is inconsistent with the development trend of "green chemistry". Summary of the Invention

[0004] The purpose of this invention is to provide a safe and mild method for preparing accordion-shaped MXene materials. A near-neutral etching solution prepared with formic acid and NaF is used, followed by treatment under water bath heating for a certain period of time, and then further removal of reaction byproducts and impurities by phosphoric acid. Finally, the material is washed with deionized water until the supernatant is neutral, thus successfully preparing the accordion-shaped MXene material.

[0005] The present invention achieves the above-mentioned technical objectives through the following technical solutions.

[0006] A method for preparing accordion-shaped MXene materials under safe and mild reaction conditions includes the following steps: 1. Preparation of MAX precursor: Graphite powder, titanium powder and aluminum powder are uniformly mixed and then sintered at high temperature to prepare atomic solid solution MAX phase. Finally, after further fine grinding and sieving, MAX (Ti3AlC2) precursor is obtained.

[0007] 2. The MAX (Ti3AlC2) precursor was dispersed in a near-neutral etching solution prepared with formic acid (HCOOH) and sodium fluoride (NaF) to remove the Al layer and prepare accordion-shaped MXene (Ti3C2) material.

[0008] 3. Wash the MXene (Ti3C2) material with deionized water 3-5 times to remove the etching solvent.

[0009] 4. Remove reaction byproducts from MXene (Ti3C2) material by passing it through a low concentration of phosphoric acid, and finally remove impurities by washing with water until the supernatant is neutral. Dry the prepared powder to obtain high-purity accordion-shaped MXene (Ti3C2) material.

[0010] Furthermore, in step 1, the molar ratio of graphite powder, titanium powder, and aluminum powder is 1:1.5:(0.5~0.65).

[0011] Furthermore, in step 1, the high-temperature sintering temperature is 1300~1450℃, and the holding time is 3~4 hours.

[0012] Further, in step 1, fine grinding and sieving yield MAX(Ti3AlC) 2） The precursor particle size is 400~600 mesh.

[0013] Furthermore, in step 2, the mass concentration of HCOOH is 99%.

[0014] Further, in step 2, the molar ratio of formic acid (HCOOH) and sodium fluoride (NaF) is 1:1, and 0.6g of MAX precursor is added to 42~45mL of the mixture of formic acid and sodium fluoride, and the mixture is etched at 50~65℃ for 36~72 hours to remove Al layer atoms and prepare accordion-shaped MXene material.

[0015] Further, in step 3, the accordion-shaped MXene material is dispersed in 170-200 mL of deionized water to remove the mixture of formic acid and sodium fluoride; the method for removing reaction byproducts from the washed accordion-shaped MXene material includes: washing with 50-65% phosphoric acid solution, the amount of phosphoric acid solution being 170-200 mL, and washing with water until the pH is 6.6-7.

[0016] Furthermore, in step 4, the mass concentration of phosphoric acid is 50-65%.

[0017] Furthermore, in step 4, the drying technique includes freeze drying for 24 to 36 hours or vacuum drying at 60 to 75°C for 24 hours.

[0018] Effects of the invention: Compared with the prior art, the present invention has the following beneficial technical effects: Etching agent innovation: Environmentally compatible organic weak acid is used as the core etchant. The protons (H⁺) of the organic weak acid react slowly and selectively with the A-site (such as Al) element in the MAX phase (such as Ti3AlC2), avoiding the excessive corrosion of the MXene host layer (such as Ti3C2) by traditional strong acids (such as HF).

[0019] Mild reaction conditions: The reaction process of the organic weak acid system does not produce violent exothermic reactions or toxic gases, and the waste liquid contains only organic acid salts (such as acetates), which can be recovered through simple neutralization, evaporation and crystallization, significantly reducing environmental treatment costs and equipment corrosion risks, and possessing industrial scale-up potential. Attached Figure Description

[0020] Figure 1 This is a scanning electron microscope image of Ti3AlC2 prepared in Example 1 of the present invention.

[0021] Figure 2 This is a scanning electron microscope image of the accordion-shaped Ti3C2 prepared in Example 1 of the present invention.

[0022] Figure 3 The image shows the XRD pattern of Ti3AlC2 prepared in Example 1 of this invention.

[0023] Figure 4 The image shows the XRD pattern of the accordion-shaped Ti3C2 prepared in Example 1 of this invention.

[0024] Figure 5 XPS spectra of Ti3AlC2 and accordion-shaped Ti3C2 prepared in Example 1 of the present invention. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments: A method for preparing an accordion-shaped MXene material under safe and mild reaction conditions includes the following steps: Step 1: Mix graphite powder, titanium powder and aluminum powder uniformly in a molar ratio of 1:1.5:(0.5~0.65), and then sinter at 1300~1450℃ for 3~4 hours to prepare an atomic MAX phase precursor. Finally, after fine grinding and sieving, a MAX precursor with a particle size of 400~600 mesh is obtained.

[0026] Step 2: Disperse the MAX precursor in a near-neutral etching solution prepared with HCOOH and NaF, wherein the molar ratio of HCOOH to NaF is 1:1, and add 0.6g of MAX precursor to every 42~45mL of etching solution. Etch for 36-72 hours at 50~65℃ with stirring in a water bath to remove Al layer atoms and prepare accordion-shaped MXene material.

[0027] Step 3: Disperse the etched accordion-shaped MXene material into 170~200mL of deionized water and sonicate for 10 minutes. Then centrifuge and repeat the process 3~6 times to remove the etchant.

[0028] Step 4: Disperse the washed accordion-shaped MXene material into a 50-65% (w / w) phosphoric acid solution, adding 0.6g of the accordion-shaped MXene material to each 170-200mL of phosphoric acid solution to remove the etching agent. Stir at 25-40℃ for 7-10 minutes to remove reaction byproducts. Then wash with deionized water until the pH of the supernatant is 6.6-7. Finally, centrifuge to collect the sample and dry it to obtain high-purity accordion-shaped MXene material. The drying methods include freeze-drying for 24-36 hours or vacuum drying at 60-75℃ for 24 hours. Example

[0029] Step 1: Mix graphite powder, titanium powder and aluminum powder uniformly in a molar ratio of 1:1.5:0.5, then sinter at 1300℃ for 3 hours, and finally obtain the MAX precursor by fine grinding and sieving.

[0030] Step 2: Disperse the synthesized MAX precursor into an etching solution with a molar ratio of 1:1 of HCOOH and NaF. Disperse 0.6g of the MAX precursor into 42mL of etching solution and etch for 36 hours at 50℃ with stirring in a water bath. The accordion-shaped MXene material is prepared by gently etching the Al layer atoms.

[0031] Step 3: Disperse the etched accordion-shaped MXene material into 170 mL of deionized water and sonicate for 10 minutes. Then centrifuge and repeat the process 3 times to remove the etchant.

[0032] Step 4: The washed accordion-shaped MXene material was dispersed in a 50% (w / v) phosphoric acid solution and stirred at 25°C for 7 minutes at a (w / v) ratio of 0.6 g / 200 mL. The mixture was then washed with water and centrifuged until the pH of the supernatant reached 6.6. Finally, the powder was collected by centrifugation and freeze-dried for 36 hours to obtain high-purity accordion-shaped MXene material. In this example, the yield of the accordion-shaped MXene (Ti3C2) material was 78%. Example

[0033] Step 1: Mix graphite powder, titanium powder and aluminum powder uniformly in a molar ratio of 1:1.5:0.55, then sinter at 1400℃ for 4 hours, and finally obtain the MAX precursor by fine grinding and sieving.

[0034] Step 2: The synthesized MAX precursor was dispersed in an etching solution with a molar ratio of 1:1 of HCOOH and NaF. 0.6 g of MAX precursor was dispersed in 43 mL of etching solution, and the solution was etched at 55 °C in a water bath for 48 hours with stirring. Accordion-shaped MXene material was prepared by gently etching the Al layer atoms.

[0035] Step 3: Disperse the etched accordion-shaped MXene material into 180 mL of deionized water and sonicate for 10 minutes. Then centrifuge and repeat the process 4 times to remove the etchant.

[0036] Step 4: The washed accordion-shaped MXene material was dispersed in a 55% (w / v) phosphoric acid solution and stirred at 30°C for 8 minutes at a (w / v) ratio of 0.6 g / 190 mL. After washing with water and centrifugation until the pH of the supernatant reached 6.7, the powder was collected by centrifugation and then vacuum-dried at 60°C for 24 hours to obtain high-purity accordion-shaped MXene material. In this example, the yield of the accordion-shaped MXene (Ti3C2) material was 77%. Example

[0037] Step 1: Mix graphite powder, titanium powder and aluminum powder uniformly in a molar ratio of 1:1.5:0.6, then sinter at 1350℃ for 3 hours, and finally obtain the MAX precursor by fine grinding and sieving.

[0038] Step 2: The synthesized MAX precursor was dispersed in an etching solution with a molar ratio of 1:1 of HCOOH and NaF. 0.6 g of MAX precursor was dispersed in 44 mL of etching solution, and the solution was etched for 60 hours under water bath stirring and heating at 60 °C. Accordion-shaped MXene material was prepared by gently etching the Al layer atoms.

[0039] Step 3: Disperse the etched accordion-shaped MXene material into 190 mL of deionized water and sonicate for 10 minutes. Then centrifuge and repeat 5 times to remove the etchant.

[0040] Step 4: The washed accordion-shaped MXene material was dispersed in a 60% (w / v) phosphoric acid solution and stirred at 35°C for 9 minutes at a (w / v) ratio of 0.6 g / 180 mL. After washing with water and centrifugation until the pH of the supernatant reached 6.8, the powder was collected by centrifugation and then vacuum-dried at 70°C for 24 hours to obtain high-purity accordion-shaped MXene material. In this example, the yield of the accordion-shaped MXene (Ti3C2) material was 75%. Example

[0041] Step 1: Mix graphite powder, titanium powder and aluminum powder uniformly in a molar ratio of 1:1.5:0.65, then sinter at 1450℃ for 4 hours, and finally obtain the MAX precursor by fine grinding and sieving.

[0042] Step 2: The synthesized MAX precursor was dispersed in an etching solution with a molar ratio of 1:1 of HCOOH and NaF. 0.6 g of MAX precursor was dispersed in 45 mL of etching solution, and the solution was etched at 65 °C in a water bath for 72 hours with stirring. Accordion-shaped MXene material was prepared by gently etching the Al layer atoms.

[0043] Step 3: Disperse the etched accordion-shaped MXene material into 200 mL of deionized water and sonicate for 10 minutes. Then centrifuge and repeat the process 6 times to remove the etchant.

[0044] Step 4: The washed accordion-shaped MXene material was dispersed in a 65% (w / v) phosphoric acid solution and stirred at 40°C for 10 minutes at a (w / v) ratio of 0.6 g / 170 mL. The mixture was then washed with water and centrifuged until the pH of the supernatant reached 7. Finally, the powder was collected by centrifugation and freeze-dried for 24 hours to obtain high-purity accordion-shaped MXene material. In this example, the yield of the accordion-shaped MXene (Ti3C2) material was 80%.

[0045] The preferred embodiments of the present invention have been described in detail above. However, the scope of protection of the present invention is not limited thereto. Any modifications, variations, or substitutions made by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing accordion-shaped MXene materials under safe and mild reaction conditions, characterized in that, Includes the following steps: (1) Graphite powder, titanium powder and aluminum powder are uniformly mixed and then sintered at high temperature to form the MAX phase. Finally, Ti3AlC2 precursor is obtained by further fine grinding and sieving. (2) The Ti3AlC2 precursor was dispersed in a mixture of formic acid and sodium fluoride and the Al layer was etched away to prepare an accordion-shaped Ti3C2 material. (3) Wash the Ti3C2 material with deionized water 3 to 5 times to remove the etching solvent; (4) The Ti3C2 material is treated with low-concentration phosphoric acid to remove reaction byproducts, and then washed with water to remove impurities until the supernatant is neutral. The prepared powder is dried to obtain high-purity accordion-shaped Ti3C2 material.

2. The method for preparing accordion-shaped MXene material under safe and mild reaction conditions according to claim 1, characterized in that, In step (1), the molar ratio of graphite powder, titanium powder and aluminum powder is 1:1.5:(0.5~0.65).

3. The method for preparing accordion-shaped MXene material under safe and mild reaction conditions according to claim 1, characterized in that, In step (1), the sintering temperature is 1300~1450℃, and the holding time is 3~4 hours.

4. The method for preparing accordion-shaped MXene material under safe and mild reaction conditions according to claim 1, characterized in that, In step (1), the particle size of the Ti3AlC2 precursor obtained by fine grinding and sieving is 400~600 mesh.

5. The method for preparing accordion-shaped MXene material under safe and mild reaction conditions according to claim 1, characterized in that, Step (2) The molar ratio of formic acid and sodium fluoride is 1:1, and 0.6 g of MAX precursor is added to 42~45 mL of the mixture of formic acid and sodium fluoride. The mixture is then etched at 50~65℃ for 36~72 hours to remove Al layer atoms and prepare accordion-shaped MXene material.

6. The method for preparing accordion-shaped MXene material under safe and mild reaction conditions according to claim 1, characterized in that, Step (3) Disperse the accordion-shaped MXene material into a mixture of 170-200 mL of deionized water to remove formic acid and sodium fluoride; The method for removing reaction byproducts from the washed accordion-shaped MXene material includes: washing with a 50-65% phosphoric acid solution (170-200 mL) and washing with water until the pH reaches 6.6-7.

7. The method for preparing accordion-shaped MXene material under safe and mild reaction conditions according to claim 1, characterized in that, In step (4), the mass concentration of phosphoric acid is 50-65%, and it is dried under vacuum at 60-75°C for 24 hours or freeze-dried for 24-36 hours.

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