Fast and High-Yield Anhydrous Synthesis of Ti 3 C 2 T x MXene with High Electrical Conductivity and Exceptional Mechanical Strength.

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, NH 4 HF 2 as an etchant, CH 3 SO 3 H as an acid, and NH 4 PF 6 as an intercalant. The reaction temperature can be increased up to 100 °C to accelerate the etching and delamination of Ti 3 AlC 2 MAX crystals; in addition, the destructive side reaction of the produced Ti 3 C 2 T x MXene is suppressed in the etchant. Consequently, the etching reaction is completed in 4 h at 100 °C and produces high-quality monolayer Ti 3 C 2 T x with an electrical conductivity of 8200 S cm -1 and yield of over 70%. The Ti 3 C 2 T x MXene fabricated via this modified synthesis exhibits different surface structures and properties arising from more F-terminations than those of Ti 3 C 2 T x synthesized in aqueous HF 2 T. The atypical surface structure of Ti 3 C 2 T x MXene results in an exceptionally high ultimate tensile strength (167 ± 8 MPa), which is five times larger than those of Ti 3 C 2 T x MXenes synthesized in aqueous HF solution (31.7 ± 7.8 MPa).