Fast and High-Yield Anhydrous Synthesis of Ti3C2Tx MXene with High Electrical Conductivity and Exceptional Mechanical Strength

Abstract

2D transition metal carbides or nitrides (MXenes) have attracted considerable attention from materials scientists and engineers owing to their physicochemical properties. Currently, MXenes are synthesized from MAX-phase precursors using aqueous HF. Here, in order to enhance the production of MXenes, an anhydrous etching solution is proposed, consisting of dimethylsulfoxide as solvent with its high boiling point, NH₄HF₂ as an etchant, CH₃SO₃H as an acid, and NH₄PF₆ as an intercalant. The reaction temperature can be increased up to 100 °C to accelerate the etching and delamination of Ti₃AlC₂ MAX crystals; in addition, the destructive side reaction of the produced Ti₃C₂T_x MXene is suppressed in the etchant. Consequently, the etching reaction is completed in 4 h at 100 °C and produces high-quality monolayer Ti₃C₂T_x with an electrical conductivity of 8200 S cm⁻¹ and yield of over 70%. The Ti₃C₂T_x MXene fabricated via this modified synthesis exhibits different surface structures and properties arising from more F-terminations than those of Ti₃C₂T_x synthesized in aqueous HF₂T. The atypical surface structure of Ti₃C₂T_x MXene results in an exceptionally high ultimate tensile strength (167 ± 8 MPa), which is five times larger than those of Ti₃C₂T_x MXenes synthesized in aqueous HF solution (31.7 ± 7.8 MPa).