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 Ti3C2Tx MXene flakes modified with hydrazine (HMH) and KOH and with water as the control (HMH‐Ti3C2, KOH‐Ti3C2, and H2O‐Ti3C2, respectively) are experimentally and theoretically studied. Modification greatly increases the dispersibility of Ti3C2Tx 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‐Ti3C2 and KOH‐Ti3C2 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 Ti3C2Tx 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. Dispersibility and photochemical stability of water‐, hydrazine‐, and KOH‐Ti3C2 flakes are experimentally and theoretically studied. The mechanisms underlying the marked improvement in the colloidal dispersibility and photochemical stability by the modifications (especially by hydrazine) are revealed. The findings provide new insight into the environmental transformation and help to design functional MXenes.