Surface-engineered Ti <sub>3</sub> C <sub>2</sub> T <i> <sub>x</sub> </i> MXene enabling rapid sodium/potassium ion storage
Yingying Zhao, Guangsheng Dong, Man Zhang, Dashuai Wang, Yujin Chen, Dianxue Cao, Kai Zhu, Guohua Chen
Abstract
Abstract MXene with expanding interlayer and tunable terminations emerge as promising candidates for metal ion storage. Herein, we develop a facile urea decomposition strategy to obtain ultrathin nitrogen-modified Ti 3 C 2 T x (N-UT-Ti 3 C 2 T x ) with optimized terminations as anode for sodium/potassium ion storage. Experimental results have shown that NH 3 molecules produced by urea pyrolysis could introduce two types of nitrogen modifications in Ti 3 C 2 , function substitution for –OH (FS) and surface absorption on –O (SA). During subsequent hydrothermal and heating processes, the nitrogen atoms in situ substitute the lattice carbon in Ti 3 C 2 (LS). Further, the effects of these nitrogen modifications in Ti 3 C 2 on diffusion kinetics of Na + and K + are investigated by first-principles calculations. The superior Na + storage performances of the N-UT-Ti 3 C 2 T x anode are the main attribute of the nitrogen modification of LS in Ti 3 C 2 , while the excellent K + storage performances come from the synergistic effects of the nitrogen modifications of FS and LS in Ti 3 C 2 . This work emphasizes the effectiveness of surface engineering of nitrogen modifications and optimized terminations for improving the electrochemical performances of Ti 3 C 2 T x and inspires the design of heteroatom modified MXenes for energy storage.