Synthesis of fluorine-free Ti₃C₂T_x MXenes via acidic activation for enhanced electrochemical applications

MXenes are a class of two-dimensional materials composed of carbides and nitrides, which possess tunable properties and thus suitable for electrochemical applications. The etching method of MXene plays an important role in defining the electrochemical properties. Here, a novel hydrothermal acidic etching process was introduced to synthesize fluorine free MXenes by varying etching time and temperature. As a result, highly effective fluorine free Ti₃C₂T_x MXenes with enhanced electrochemical properties were obtained. It is also noted that the synthesized Ti₃C₂T_x MXenes exhibit distinct charge-discharge performance and impressive battery-like characteristics when tested in a 1 M H₂SO₄ electrolyte. Especially, the 6D-160 °C sample shows relatively superior gravimetric capacity of 450 C g⁻¹ with a retention rate of 114 % after 8000 cycles, compared to the HF-etched sample (only 75 % lower capacitance). This novel approach demonstrates a significant improvement in the electrochemical performance of Ti₃C₂T_x MXenes and suggests a highly effective technique for surface modification of MXenes.