Freeing Fluoride Termination of Ti₃C₂T_x via Electrochemical Etching for High-Performance Capacitive Deionization

Ti₃C₂T_x MXene is a promising Faradic capacitive deionization (CDI) electrode for high salt removal in future desalination, whereas the surface termination group of fluoride (-F) significantly impedes ion access to Ti₃C₂ and charge-transfer efficiency. Herein, we propose an electrochemically etched strategy to synthesize -F-free Ti₃C₂T_x through three-electrode cyclic voltammetry scanning within a narrowed potential window in an alkaline electrolyte. The resulting assembly of an asymmetric electrochemical-etched Ti₃C₂T_x//activated carbon CDI device can deliver an excellent salt removal capacity of 20.27 mg·g^-1 with an adsorption rate of 1.01 mg g^-1 min^-1 owing to the enhanced hydrophilicity and ion transport. The tiny CDI device is demonstrated, which can generate an electric current during the electrosorption of salt ions, thus facilitating the powering of a red light-emitting diode. This study opens a new avenue for the surface chemistry of Ti₃C₂T_x and is expected to achieve future applications in desalination and renewable energy.