Cetyltrimethylammonium bromide assisted intercalation and exfoliation for titanium carbide with enlarged interlayer spacing for high-performance supercapacitor

It is well known that the interlayer spacing of two-dimensional (2D) materials is crucial in enhancing their electrochemical performance. However, the interlayer spacing of titanium carbide (Ti3C2Tx) nanosheets prepared by current synthetic methods is either limited or the experimental methods are too complicated. Based on this, we propose a new synthesis method using the mixture of hydrogen fluoride (HF) and cetyltrimethylammonium bromide (CATB) as the etching agent, and the interlayer spacing of the Ti3C2Tx nanosheets obtained by exfoliation is as high as 37.8 Å. The enlarged interlayer spacing not only exposes more active sites but is sufficient to accommodate more insertion and deinsertion of cations, which achieves a significantly improved capacitance value of 322 F/g with scan rate of 5 mV/s in acidic electrolyte and excellent rate performance. In particular, the advantages of the enlarged interlayer spacing in energy storage are more reflected both in neutral electrolyte and alkaline electrolyte. The density functional theory (DFT) analysis indicates that the optimal energy storage performance is achieved only with the optimal interlayer spacing. This work provides a guiding design approach for MXene materials and high-performance supercapacitors.