Enhanced pseudocapacitive energy storage and thermal stability of Sn²⁺ ion-intercalated molybdenum titanium carbide...

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 Mo₂TiC₂, was intercalated with Sn ions to study the structural, morphological, optical, and electrochemical energy-storage effects. The Sn²⁺-intercalated modified layered structure, prepared via a facile liquid-phase pre-intercalated cetyltrimethylammonium bromide (CTAB) method, showed a higher surface area of 30 m² g^-1, low band gap of 1.3 eV, and large interlayer spacing of 1.47 nm, as compared to the pristine Mo₂TiC₂. The Sn@Mo₂TiC₂ electrode showed a high specific capacitance of 670 F g^-1, representing a large diffusion control value compared to pure Mo₂TiC₂ (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@Mo₂TiC₂ electrode showed much improved electrocatalytic efficiency, which may open up ways to employ double-transition 2D MXenes in energy-storage devices.