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

Abstract

<p>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 Ti3C2Tx MXene is demonstrated by utilizing a sulfhydryl-containing molecule, β-mercaptoethanol (BME), which can significantly suppress the Ti3C2Tx oxidation in various environments, including long-term storage of Ti3C2Tx aqueous dispersions (2 m), single-layer Ti3C2Tx-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 Ti3C2Tx. 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 Ti3C2Tx from 4.70 to 4.39 eV, resulting in improved carrier-transport performances in MoS2 field-effect transistors owing to band alignment, where BME–Ti3C2Tx serves as the source electrode. The described methodology can largely contribute to the ultralong service life of 2D Ti3C2Tx without affecting its excellent properties, thereby promoting the practical application of this emerging material.</p>