Ti₃C₂T_x Nanosheet-Based Electrode with High Capacitance Enabled by Nitrogen Doping and Surface Modification

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.