Two-dimensional Nb₂C MXene thin films for electro-ionic actuation

Nb₂CT_x MXene was synthesized through a Lewis acid-assisted molten salt etching process using silver chloride, providing a fluoride-free and safer alternative to conventional HF-based etching methods for converting the Nb₂AlC MAX phase into layered Nb₂CT_x sheets. Structural and surface analyses confirm the effective removal of the Al layer and the successful formation of conductive Nb₂CT_x, with preserved morphology and controlled surface terminations. The synthesized MXene was subsequently incorporated into a PEDOT:PSS (PP) matrix to fabricate flexible composite thin films for electromechanical actuation. Electrochemical characterization performed at various scan rates demonstrates stable capacitive behavior, delivering an areal capacitance of 206.62 mF cm⁻². Compared with conventional PP films, the Nb₂C–PP composite exhibits enhanced electroactive response and improved bending deformation, achieving a maximum displacement of 10.44 mm under low-amplitude alternating voltage input. To support the experimental findings, first-principles density functional theory (DFT) calculations were conducted to investigate the electronic structure and interfacial characteristics of Nb₂CT_x, providing insight into the improved charge transport and actuation performance. The combined experimental and theoretical results highlight molten salt-derived Nb₂CT_x MXene as a scalable and efficient material platform for next-generation soft actuator applications.