Hydrofluoric Acid-Free Synthesis of Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> MXene Nanostructures for Energy Applications
I‐Wen Peter Chen, Anil A. Kashale, Yuhan Pan
Abstract
The preparation of titanium carbide (Ti 3 C 2 T x ) thin sheets (T represents surface termination), an emerging class of two-dimensional materials, heavily relies on the etching of interlayered aluminum (Al) of MAX (M, A, and X represent transition metals, Al, and carbon, respectively) using concentrated hydrofluoric acid (HF). However, HF is an acutely toxic chemical. Herein, for the first time, we propose a dissolution-driven delamination method to prepare Ti 3 C 2 T x MXene thin sheets using an HF-free solvent to remove the interlayers of Al. Bis(trifluoromethanesulfonyl)imide (TFSI) is a delaminating agent that can directly and effectively dissolve the Al interlayers of MAX. The role of TFSI in this delamination process, i.e., the preferential formation of the surface of a Ti 3 C 2 T x thin sheet, is a key parameter for superior supercapacitor application. The prepared Ti 3 C 2 T x sheets were loaded on Ni foam (NF) via a hydrothermal reaction to form a Ti 3 C 2 T x MXene/NF-4 h composite electrode. This Ti 3 C 2 T x MXene/NF-4 h composite electrode exhibits the highest unprecedented capacitance of 3090 F/g at a current density of 10 A/g in a 1 M KOH electrolyte. It also exhibits excellent rate capabilities at different current densities (from 10 to 30 A/g) while maintaining 76.4% capacity retention after long life cycles. This study provides fundamental insights into the effect of the dissolution of interlayered Al of Ti 3 AlC 2 on the preparation of Ti 3 C 2 T x thin sheets as well as sheds light on the development of next-generation flexible and simple integrated supercapacitors with excellent gravimetric performance.