Method for preparing fluoride-free MXene by adopting electrochemical etching method

Abstract

The invention discloses a method for preparing fluorine-free MXene by adopting an electrochemical etching method, the method comprises the following steps: immersing two MAX blocks serving as a working electrode and a counter electrode into a mixed aqueous solution of hydroxide and chloride respectively, applying voltage, and stirring; collecting black precipitates in the solution through centrifugal washing, and then carrying out ultrasonic treatment under ice-water bath and inert gas protection conditions; and centrifuging and washing for multiple times until the supernatant becomes black, and then freeze-drying the black supernatant to obtain few-layer or single-layer MXene. The obtained MXene, the nanocellulose and the carbon nanofiber are subjected to suction filtration to form a film, and the specific capacitance can reach 249.9 F / g, which is obviously superior to that of a contrast sample obtained by etching a fluorine-containing reagent.

Description

technical field [0001] The invention relates to a method for preparing inorganic non-metallic materials, in particular to a method for preparing fluorine-free MXene by electrochemical etching. Background technique [0002] MXene is a general term for two-dimensional transition metal carbides, nitrides and carbonitrides with a graphene-like structure. It was first reported in 2011 by the research group of Professor Y. Gogotsi of Drexel University. MXene is usually obtained by selectively etching the A component (usually Al) in the MAX phase of the ternary layered ceramics by hydrofluoric acid or other fluorine-containing reagents, and the general chemical formula is M n+1 x n T x (n=1~3), wherein M represents an early transition metal (Ti, Mo, Nb, V, Sc, Zr, Hf, Ta, Cr, etc.), X represents C or / and N, and T represents an attached surface functional group, x represents the number of surface functional groups in each chemical formula. This kind of material has some excellen...

AI Technical Summary

Problems solved by technology

However, in the concentrated alkali hydrothermal method, 27.5M NaOH solution needs to be used, and the hydrothermal temperature is as high as 270°C. These conditions are too harsh (Angew.Chem.Int.Ed., 2018, 57:6115-6119)

In the molten salt method, heat treatment at a high temperature of 750°C for 24 hours is required, and an overpowering oxidizing agent, ammonium persulfate, is required to remove the by-product copper, which is time-consuming and cumbersome, and increases the requirements for equipment (Nat.Mater., 2020 , 19:894-899)

In several reports on the electrochemical etching method, some etching time is too long (5 days), some need heating and the output is too low; Concentration of toxic organic intercalants (such as tetramethylammonium hydroxide) to strip the etched multilayer MXene, and the stripping process is quite time-consuming (usually ≥ 12h)

In the iodine organic solution etching method, it is necessary to use toxic and flammable acetonitrile solvent, and it needs to be etched at 100°C for 4 days, which is quite unfavorable (Angew.Chem.Int.Ed., 2021, 60:8689- 8693)

Images