Bridged Ti₃C₂T_X MXene Film with Superior Oxidation Resistance and Structural Stability for High-Performance Flexible Supercapacitors

Two-dimensional (2D) Ti₃C₂T_X MXene has been a promising nanomaterial in energy storage, electromagnetic shielding, and sensors. However, MXene suffers from major drawbacks of unstable structure and vulnerable oxidation in ambient moisture. Herein, a facile strategy is proposed to address the challenging problems via oxygen-rich molecular bridging. The tannic acid bridging agent with abundant O-containing ligands can self-polymerize and bind at the terminal groups and exposed Ti atom of Ti₃C₂T_X by a synergistic hydrogen bond and coordination bond. The enhanced interlaminar interaction endows the MXene film with resistance to oxidation, swelling, and mechanical fragility. Density functional theory calculations prove that the charge transfer from MXene to oxygen-rich molecules improves the interface electronic structure, thus enlarging the work function of pristine Ti₃C₂T_X, which means increased resistance toward losing electrons and being oxidized. The resultant bridged MXene film achieves 7 times toughness enhancement compared with pristine MXene, stable conductivity during the long-term storage in a humid environment, excellent structural and electrochemical stability during 10 000 cycles in aqueous electrolytes, and a remarkable energy density of 53.3 mW h cm^–3 used for flexible symmetric micro-supercapacitors. This work opens opportunities for the rational design and fabrication of robust 2D MXene assemblies for aqueous energy storage.