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...

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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)

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