LAUSR

Mxenes, a new family of two-dimensional (2D) transition-metal carbide and nitride materials, are supposed to be the promising pseudocapacitive materials because of their high electronic conductivity and hydrophilic surfaces. MXenes, prepared by removing the "A" elements of their corresponding MAX phases by hydrofluoric acid (HF) or LiF-HCl etching, possess abundant terminal groups like -F, -OH and -O groups. It has been proven that the MXenes with fewer -F terminal groups and more -O groups showed higher pseudocapacitor performance. And in organic reactions, -OH and -X (X = halogen) groups could turn to ether groups in strong nucleophilic reagent. Inspired by that, herein, we report an n-Butylithium treated method to turn the -F and -OH terminal groups to -O groups on the Ti3C2Tx MXenes. Two types of Ti3C2Tx MXenes prepared by either HF or LiF-HCl etching were systematically investigated, and comparison with the traditional KOH/NaOH/LiOH treated method was also carried out. It is found that most the -F terminal groups on the Ti3C2Tx MXenes can be successfully removed by n-Butylithium, and abundant -O terminal groups were formed. The n-Butylithium treated Ti3C2Tx MXenes show promising application in high performance pseudocapacitors. A record high capacitance of 523 F g-1 at 2 mV s-1 was obtained for the n-Butylithium treated Ti3C2Tx MXenes, and 96% capacity can be remained even after 10000 cycles.