Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> Nanosheet-Based Electrode with High Capacitance Enabled by Nitrogen Doping and Surface Modification
Yongyong Yao, Xianghui Zhang, Lu Tan, Jing Pan, Chengwei Zhan, Weifeng Liu, Yamin Feng, Haixia Li, Lun Xiong
Abstract
Owing to its high electrical conductivity, unique layered structure, and strong hydrophilicity, two-dimensional nanomaterial titanium carbide (Ti 3 C 2 T x ) has attracted considerable attention as an electrode material for energy storage systems (EESs). However, the applications of Ti 3 C 2 T x in EESs are severely limited by self-restacking and −F surface terminations, which are usually inevitable during the preparation of Ti 3 C 2 T x .To improve the electrochemical performance of Ti 3 C 2 T x, the present authors doped Ti 3 C 2 T x with nitrogen, preparing N–Ti 3 C 2 T x, via thermal decomposition of urea. The interlayer spacing increased from 1.17 nm in Ti 3 C 2 T x to 1.33 nm in N–Ti 3 C 2 T x and the −F surface termination was largely reduced. Benefiting from the synergistic effect of modified surface termination and expanded interlayer spacing, the prepared N–Ti 3 C 2 T x electrode in 1 M H 2 SO 4 delivers a high specific capacitance (390 F g –1 ) at a current density of 1 A g –1 (approximately twice that of pristine Ti 3 C 2 T x ). To demonstrate the effectiveness of the method in other EESs, the Zn 2+ -storage capacity of the N–Ti 3 C 2 T x electrode was tested in 1 M ZnSO 4 . The electrode exhibited a capacitance of 252 F g –1 at 1 A g –1, exceeding that of the pristine Ti 3 C 2 T x electrode (212 F g –1 ). Furthermore, the energy and power densities of the N–Ti 3 C 2 T x // MnO 2 –CNT system reached 26 W h kg –1 and 950 W kg –1, respectively, much larger than those of the Ti 3 C 2 T x // MnO 2 –CNT system (13 W h kg –1 and 550 W kg –1, respectively). The proposed strategy can facilely functionalize Ti 3 C 2 T x for use in different high-performing EESs.