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CN-121974351-A - Method for preparing MXene by fluorine-free etching through ultrasonic-assisted supercritical carbon dioxide flash explosion technology

CN121974351ACN 121974351 ACN121974351 ACN 121974351ACN-121974351-A

Abstract

The invention discloses a method for preparing MXene by fluorine-free etching of an ultrasonic-assisted supercritical carbon dioxide flash explosion technology, which relates to the field of MXene preparation, and utilizes the synergistic effect of a high-frequency power ultrasonic technology, a flash explosion technology and a supercritical carbon dioxide fluid medium to finish etching, intercalation and stripping to prepare MXene by a one-pot method, placing a fluorine-free etchant and a MAX phase in a supercritical reaction kettle, introducing carbon dioxide to enable the carbon dioxide to reach a supercritical state, applying continuous or intermittent high-frequency power ultrasonic treatment to carry out supercritical etching reaction, carrying out instantaneous supercritical flash explosion treatment after the reaction is finished, releasing pressure on a flash explosion area and a buffer area, collecting products, centrifuging, washing and drying to obtain MXene products, avoiding the generation of fluorine-containing waste liquid, and obviously improving etching efficiency and product yield by virtue of high permeation and mass transfer characteristics of supercritical carbon dioxide, thereby providing a new way for large-scale preparation of various MXene materials.

Inventors

  • ZHANG HENGYU
  • LONG JIAJIE

Assignees

  • 苏州大学

Dates

Publication Date
20260505
Application Date
20260126

Claims (10)

  1. 1. A method for preparing MXene by fluorine-free etching of an ultrasonic-assisted supercritical carbon dioxide flash explosion technology is characterized by comprising the following specific steps: the first step, uniformly mixing a fluorine-free etching agent and MAX, and then placing the mixture in a supercritical reaction kettle; Introducing carbon dioxide into a supercritical reaction kettle to enable the carbon dioxide to reach a supercritical state, and performing supercritical etching reaction in a stirring mode; Thirdly, performing instantaneous supercritical flash explosion treatment after the supercritical etching reaction is finished; And fourthly, releasing the pressure of the flash explosion area and the buffer area thereof, and collecting the product to obtain the MXene product.
  2. 2. The method for preparing MXene by using fluorine-free etching of the ultrasonic-assisted supercritical carbon dioxide flash explosion technology, which is disclosed in claim 1, is characterized in that the fluorine-free etchant in the first step is a fluorine-free acid etchant or a fluorine-free alkali etchant, in order to accelerate the reaction process and/or increase the interlayer spacing in the first step, an auxiliary agent is selected to be added, the dosage of the auxiliary agent is 15% -80% of the fluorine-free etchant by mass percent, the auxiliary agent is one or more of water, ethanol, methanol, isopropanol, hydrogen peroxide, dimethyl sulfoxide and acetone, and the mass ratio of the fluorine-free etchant to MAX phase is fluorine-free etchant with MAX phase=50:1-10:1.
  3. 3. The method for preparing MXene by using the ultrasonic-assisted supercritical carbon dioxide flash explosion technology according to claim 2, wherein the fluorine-free acid etchant is inorganic acid and/or organic acid, the inorganic acid is one or more of hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid, perchloric acid and carbonic acid, and the organic acid is one or more of oxalic acid, formic acid and acetic acid.
  4. 4. The method for preparing MXene by using the fluorine-free etching of the ultrasonic-assisted supercritical carbon dioxide flash explosion technology according to claim 2, wherein the fluorine-free alkali etching agent is inorganic alkali and/or organic alkali, the inorganic alkali is one or more of sodium hydroxide, potassium hydroxide, lithium hydroxide, ammonium hydroxide, barium hydroxide, magnesium hydroxide, ammonium hydroxide, sodium carbonate and potassium carbonate, and the organic alkali is one or more of tetramethyl ammonium hydroxide, tetrabutyl ammonium hydroxide, tetraethyl ammonium hydroxide, methylamine, ethylamine, dimethylamine, triethylamine, ethylenediamine and hexamethylenediamine.
  5. 5. The method for preparing MXene by fluorine-free etching of an ultrasonic-assisted supercritical carbon dioxide flash explosion technology according to claim 1, wherein the MAX phase in the first step is one or more of Ti 3 AlC 2 、Nb 2 AlC、Ti 2 AlC、Mo 2 GaC、Ti 3 AlCN、V 2 AlC.
  6. 6. The method for preparing MXene by fluorine-free etching of an ultrasonic-assisted supercritical carbon dioxide flash explosion technology according to claim 5, wherein the MXene corresponding to MAX is one or more of Ti 3 C 2 T X 、Nb 2 CT X 、Ti 2 CT X 、Mo 2 CT X 、Ti 3 CN T X 、V 2 CT X , wherein T X is a surface functional group.
  7. 7. The method for preparing MXene by fluorine-free etching by using the ultrasonic-assisted supercritical carbon dioxide flash explosion technology as claimed in claim 6, wherein T X is =O and/or-OH.
  8. 8. The method for preparing MXene by fluorine-free etching by using an ultrasonic-assisted supercritical carbon dioxide flash explosion technology according to claim 1, wherein in the second step, the temperature is regulated at 32-250 ℃ and the pressure is regulated at 7.4-30 Mpa so that carbon dioxide reaches a supercritical state, the stirring speed is 400-10000rpm, the treatment time is 1-72 h, the high-frequency power ultrasonic application time is 1-20h, and the ultrasonic power is 200-800W.
  9. 9. The method for preparing MXene by fluorine-free etching of an ultrasonic-assisted supercritical carbon dioxide flash explosion technology according to claim 1, wherein the flash explosion temperature of the flash explosion treatment in the third step is 32-250 ℃, and the flash explosion pressure is 7.4-30 Mpa.
  10. 10. The method for preparing MXene by using fluorine-free etching of an ultrasonic-assisted supercritical carbon dioxide flash explosion technology as claimed in claim 1, wherein the method is characterized in that after the product is collected in the fourth step, the product is centrifuged, washed and dried, the centrifugation speed is 10000rpm, the centrifugation time is 20min, the washed solvent is ethanol or deionized water for alternate washing until the pH is more than or equal to 6, and the drying condition is freeze drying for 24h.

Description

Method for preparing MXene by fluorine-free etching through ultrasonic-assisted supercritical carbon dioxide flash explosion technology Technical Field The application relates to the technical field of MXene preparation, in particular to a method for preparing MXene by fluorine-free etching of an ultrasonic-assisted supercritical carbon dioxide flash explosion technology. Background MXene is a two-dimensional transition metal carbon/nitrogen compound with high conductivity, hydrophilicity and adjustable surface chemical characteristics, and has great application potential in the fields of energy storage, environmental management, flexible electronics and the like. However, the current mainstream preparation method seriously depends on fluorine-containing etchants such as hydrofluoric acid, ammonium bifluoride, ammonium fluoride, lithium fluoride and the like, and has the inherent defects of high toxicity, high corrosiveness, high environmental risk and the like. The method is dangerous in the production process, a large number of fluorine terminals are introduced on the surface of the material, so that the conductivity of the material is reduced, the electrochemical performance is attenuated, the material is easy to oxidize and lose efficacy in aqueous solution, and the intrinsic performance and the application of the material are severely restricted. Therefore, it is important to develop a safe and green fluorine-free preparation technology. In the prior art, some fluorine-free routes such as electrochemical etching, an alkali thermal method, a molten salt method and the like have been explored, but the methods still have respective limitations, patent CN 114477181A discloses a method for preparing MXenes rapidly and massively, the method is proposed to prepare MXenes massively in a supercritical carbon dioxide system, but the etchant used is ammonium bifluoride and still generates fluorine-containing byproducts, patent CN 114031078B discloses a preparation method of fluorine-free MXene two-dimensional nano sheets, CN116588940B discloses a green preparation method of fluorine-free MXenes and application of the fluorine-free MXenes in lithium sulfur batteries, solid alkali is proposed to obtain molten salt to prepare fluorine-free MXenes, the reaction is required to be carried out at a high temperature of more than 300 ℃, and CN 114316971B discloses a preparation method of fluorine-free MXenes quantum dots, but intrinsic characteristics of MXenes are destroyed. Therefore, developing a low-cost and scalable fluorine-free preparation technology becomes a key requirement for promoting the green production industrialization of MXene. Disclosure of Invention The invention provides a method for preparing MXene by fluorine-free etching of an ultrasonic-assisted supercritical carbon dioxide flash explosion technology, which solves the technical problems of high toxicity, high corrosiveness, high environmental risk, dangerous production process, reduced conductivity, reduced electrochemical performance, easy oxidation and failure in aqueous solution and serious restriction on intrinsic performance and application of materials caused by introducing a large number of fluorine terminals on the surface of the materials in the prior art. The invention aims to provide a method for preparing MXene by adopting supercritical carbon dioxide fluid, ultrasonic vibration and flash explosion technology to etch, intercalate and strip MXene, utilizing the strong permeability of supercritical carbon dioxide to carry a fluorine-free etchant to act on the surface and interlayer of MXene, accelerating the reaction process under the ultrasonic vibration and realizing fluorine-free high-efficiency preparation of MXene by cooperating with the dissociation effect of the flash explosion technology. The technical scheme is that the method for preparing MXene by fluorine-free etching of the ultrasonic-assisted supercritical carbon dioxide flash explosion technology comprises the following specific steps: the first step, uniformly mixing a fluorine-free etching agent and MAX, and then placing the mixture in a supercritical reaction kettle; Introducing carbon dioxide into a supercritical reaction kettle to enable the carbon dioxide to reach a supercritical state, and performing supercritical etching reaction in a stirring mode; Thirdly, performing instantaneous supercritical flash explosion treatment after the supercritical etching reaction is finished; And fourthly, releasing the pressure of the flash explosion area and the buffer area thereof, and collecting the product to obtain the MXene product. Further, the fluorine-free etchant in the first step is a fluorine-free acid etchant or a fluorine-free alkali etchant, in order to accelerate the reaction process and/or increase the interlayer spacing in the first step, an auxiliary agent is selected, the auxiliary agent is 15% -80% of the fluorine-free etchant in mass percent, the auxiliary agen