Cost-Effective Fluorine-free Synthesis of Oxygen-Terminated MXenes via High-Pressure Alkali Etching for Ultra-Stable Aqueous Zinc-Ion Batteries

Abstract Transition-metal carbides/nitrides (MXenes) have attracted significant attention for their unique two-dimensional layered structure and diverse applications. However, conventional HF-based etching methods face challenges such as high costs, limited scalability, and detrimental –F functional groups that degrade the electrochemical performance. Herein, we introduce a high-temperature and high-pressure alkali etching strategy using NaOH, offering a cost-effective and scalable route for the synthesis of MXenes. This method yields O–Ti3C2 MXenes with exclusively oxygen-containing surface groups, enhancing its antioxidant capacity and electrochemical stability. DFT simulations reveal that oxygen-containing groups on the MXene surface facilitate local charge redistribution and significantly lower the nucleation barriers for the zinc ions. Consequently, the O–Ti3C2-modified zinc anode exhibits exceptional cycling stability in symmetric battery tests, surpassing Ti3C2 materials prepared via HF or LiF/HCl etching. Moreover, nitrogen-doped N–O–Ti3C2 suppresses zinc dendrite growth, extending the cycle life of aqueous zinc-ion batteries. This work offers a green, scalable, and fluorine-free synthesis route for MXenes, highlighting the potential of oxygen-terminated MXenes in high-performance energy-storage systems.