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 TiCT MXene is demonstrated by utilizing a sulfhydryl-containing molecule, β-mercaptoethanol (BME), which can significantly suppress the TiCT oxidation in various environments, including long-term storage of TiCT aqueous dispersions (2 m), single-layer TiCT -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 TiCT . 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 TiCT from 4.70 to 4.39 eV, resulting in improved carrier-transport performances in MoS field-effect transistors owing to band alignment, where BME-TiCT serves as the source electrode. The described methodology can largely contribute to the ultralong service life of 2D TiCT without affecting its excellent properties, thereby promoting the practical application of this emerging material.