β-Mercaptoethanol-Enabled Long-Term Stability and Work Function Tuning of MXene

The oxidation degradation by unsaturated metal atoms or dangling bonds at MXene edges and defects severely hinders the practical application of MXene. Herein, a passivation scheme for Ti₃C₂T _x MXene is demonstrated by utilizing a sulfhydryl-containing molecule, β-mercaptoethanol (BME), which can significantly suppress the Ti₃C₂T _x oxidation in various environments, including long-term storage of Ti₃C₂T _x aqueous dispersions (2 m), single-layer Ti₃C₂T _x -based devices in humid air (2 m), and high-temperature environment (12 h). Notably, the nonionic BME does not cause aggregation but maintains the 2D morphology of Ti₃C₂T _x . A comprehensive investigation of the protection mechanism through density functional theory (DFT) calculations and experimental characterizations reveals that BME is adsorbed especially at the edges and surface defects of MXene (binding energy -1.70 and -1.05 eV), where the degradation starts. Further, the electron-donating effect of sulfhydryl groups tunes the work function of Ti₃C₂T _x from 4.70 to 4.39 eV, resulting in improved carrier-transport performances in MoS₂ field-effect transistors owing to band alignment, where BME-Ti₃C₂T _x serves as the source electrode. The described methodology can largely contribute to the ultralong service life of 2D Ti₃C₂T _x without affecting its excellent properties, thereby promoting the practical application of this emerging material.