アイテム詳細

要旨

The unique properties of 2D MXenes, such as metal-like electrical conductivity and versatile surface chemistry, make them appealing for various applications, including energy storage. While surface terminations of 2D MXene are expected to have a key influence on their electrochemical properties, the conventional HF-etching method limits the surface functional groups to —F, —OH, and —O. In this study, O-free, Cl-terminated MXenes (noted as Ti₃C₂Cl_x) are first synthesized by a molten salt (FeCl₂) etching route. Then, a substitution of surface termination from Cl— to N— is performed via post-thermal treatment of Ti₃C₂Cl_x in Li₃N containing molten salt electrolytes. While the Cl-terminated pristine material does not show electrochemical activity, the surface-modified, N-containing Ti₃C₂T_x exhibits a unique capacitive-like electrochemical signature in sulfuric acid aqueous electrolyte with rate performance—more than 300 F g^-1 (84 mAh g^-1) at 2 V s^-1. These results show that control of the MXene surface chemistry enables the preparation of high-performance electrodes in a previously not accessed limit of energy storage.