Ar plasma modification of 2D MXene Ti₃C₂T_x nanosheets for efficient capacitive desalination

MXenes are a new class of two-dimensional (2D) layered materials with excellent electrical conductivities, high specific surface areas and are overall environmentally benign. In terms of its structure, MXenes can be thought of as a stack of nanosheets with tunable interlayer spacings capable of rapid ion intercalation. As such, MXenes have been successfully employed as electrode materials in aqueous supercapacitors, Li-ion batteries and Na-ion hybrid supercapacitors in non-aqueous solutions. Herein, we report the novel application of MXenes Ti₃C₂T_x in a completely new field as capacitive water desalination. Interestingly, we found that the interlayer distance for the Mxenes Ti₃C₂T_x is able to be increased for efficient sodium ion transport by Ar plasma. To evaluate its desalination capabilities, the Ar plasma modified Ti₃C₂T_x was used as electrode materials and assembled in a capacitive deionization (CDI) cell. A high salt removal rate of 9.4 mg g⁻¹ min⁻¹ and an overall increased removal capacity of 26.8 mg g⁻¹ was obtained when an external power of 1.2 V was applied. The desalination performance of Ar plasma modified Ti₃C₂T_x marks the foray of MXene materials in water desalination.