Enhanced pseudocapacitive energy storage and thermal stability of Sn 2+ ion-intercalated molybdenum titanium carbide (Mo 2 TiC 2 ) MXene.

Electrochemical energy-storage (EES) devices are a major part of energy-storage systems for industrial and domestic applications. Herein, a two-dimensional (2D) transition metal carbide MXene, namely Mo 2 TiC 2 , was intercalated with Sn ions to study the structural, morphological, optical, and electrochemical energy-storage effects. The Sn 2+ -intercalated modified layered structure, prepared via a facile liquid-phase pre-intercalated cetyltrimethylammonium bromide (CTAB) method, showed a higher surface area of 30 m 2 g -1 , low band gap of 1.3 eV, and large interlayer spacing of 1.47 nm, as compared to the pristine Mo 2 TiC 2 . The Sn@Mo 2 TiC 2 electrode showed a high specific capacitance of 670 F g -1 , representing a large diffusion control value compared to pure Mo 2 TiC 2 (212 F g -1 ) at a scan rate of 2 mV s -1 . The modified electrode also presented long-term cyclic performance, high-capacity retention and coulombic efficiency measured over 10 000 cycles. The Sn@Mo 2 TiC 2 electrode showed much improved electrocatalytic efficiency, which may open up ways to employ double-transition 2D MXenes in energy-storage devices.