Fluorine‐Free Synthesis of High‐Purity Ti3C2Tx (T=OH, O) via Alkali Treatment

Abstract MXenes, 2D compounds generated from layered bulk materials, have attracted significant attention in energy‐related fields. However, most syntheses involve HF, which is highly corrosive and harmful to lithium‐ion battery and supercapacitor performance. Here an alkali‐assisted hydrothermal method is used to prepare a MXene Ti 3 C 2 T x (T=OH, O). This route is inspired from a Bayer process used in bauxite refining. The process is free of fluorine and yields multilayer Ti 3 C 2 T x with ca. 92 wt % in purity (using 27.5 m NaOH, 270 °C). Without the F terminations, the resulting Ti 3 C 2 T x film electrode (ca. 52 μm in thickness, ca. 1.63 g cm −3 in density) is 314 F g −1 via gravimetric capacitance at 2 mV s −1 in 1 m H 2 SO 4 . This surpasses (by ca. 214 %) that of the multilayer Ti 3 C 2 T x prepared via HF treatments. This fluorine‐free method also provides an alkali‐etching strategy for exploring new MXenes for which the interlayer amphoteric/acidic atoms from the pristine MAX phase must be removed.