One‐step Synthesis of Organic Terminal 2D Ti 3 C 2 T x MXene Nanosheets by Etching of Ti 3 AlC 2 in an Organic Lewis Acid Solvent

Abstract The surface and interface chemistry are critical for controlling the properties of two‐dimensional transition metal carbides and nitrides (MXenes). Numerous efforts have been devoted to the functionalization of MXenes with small inorganic ligands; however, few etching methods have been reported on the direct bonding of organic groups to MXene surfaces. In this work, we demonstrated an efficient and rapid strategy for the direct synthesis of 2D Ti 3 C 2 T x MXene nanosheets with organic terminal groups in an organic Lewis acid (trifluoromethanesulfonic acid) solvent, without introducing additional intercalations. The dissolution of aluminum and the subsequent in situ introduction of trifluoromethanesulfonic acid resulted in the extraction of Ti 3 C 2 T x MXene (T=CF 3 SO 3 − ) (denoted as CF 3 SO 3 H−Ti 3 C 2 T x ) flakes with sizes reaching 15 μm and high productivity (over 70 %) of monolayers or few layers. More importantly, the large CF 3 SO 3 H−Ti 3 C 2 T x MXene nanosheets had high colloidal stability, making them promising as efficient electrocatalysts for the hydrogen evolution reaction.