Dispersibility and Photochemical Stability of Delaminated MXene Flakes in Water.

The environmental stability of 2D MXene flakes must be systematically studied before their further application. Herein, the colloidal dispersibility and photochemical stability of delaminated Ti3 C2 Tx MXene flakes modified with hydrazine (HMH) and KOH and with water as the control (HMH-Ti3 C2 , KOH-Ti3 C2 , and H2 O-Ti3 C2 , respectively) are experimentally and theoretically studied. Modification greatly increases the dispersibility of Ti3 C2 Tx flakes. Their critical coagulation concentrations are 28.7, 106, and 49.1 mm NaCl, and their Hamaker constants are 23.7 × 10-21 , 19.1 × 10-21 , and 37.7 × 10-21 J, respectively; the colloidal interaction follows the classical Derjaguin-Landau-Verwey-Overbeek theory. HMH-Ti3 C2 and KOH-Ti3 C2 exhibit higher photochemical stability, as indicated by their stronger resistance to oxidation under UV and visible light irradiation. Changes in their physicochemical properties and the generation of reactive oxygen species (ROS) are assayed. Spin-polarized density functional theory calculations and molecular dynamics simulations are used to determine the mechanisms underlying the differences in the photochemical stability of Ti3 C2 Tx flakes. K+ ions protect the flakes from oxidation by acting as a middle layer to reduce the coupling between Ti3+ and ROS, while HMH provides stronger protection by absorbing photoelectrons or reacting with ROS. These findings provide new insight into the environmental transformation and design of functional MXenes.