Facile synthesis of 2D Mo₂TiC₂@PDA/MnO₂ composite-based electrode material for clean and efficient energy storage

Owing to their distinctive stacked layered structure, exceptional conductivity, large specific surface area, and abundance of redox active sites, two-dimensional transition carbon nitride, and metal carbides and nitrides efficiently store and transfer charges, thus becoming attractive electrode materials for supercapacitors. MXene-based supercapacitors are, however, seriously hindered by the low specific capacitance driven by severe self-discharge behavior and poor ambient stability due to oxidation. To overcome these limitations, herein, a Mo₂TiC₂@PDA/MnO₂ composite was synthesized to functionalize a glassy carbon electrode (GCE) surface via a two-layer modification strategy, which enabled faster charge transfer and ion diffusion within the electrode material, thus boosting the capacitive performance of Mo₂TiC₂ MXene. The composite's structure and morphology were confirmed by X-ray diffraction, transmission electron microscopy, and scanning electron microscopy. Furthermore, the electrochemical behavior of the functionalized-electrodes was assessed by galvanostatic charge–discharge (GCD), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS), which all revealed that Mo₂TiC₂@PDA/MnO₂ can be a promising electrode material for supercapacitor. The Mo₂TiC₂@PDA/MnO₂ modified electrode delivered a high specific capacitance of 573 Fg⁻¹ at a current density of 1 Ag⁻¹ and demonstrated superior cycling stability with 87.43% capacitance retention over 5000 cycles. This study shows that integrating Mo₂TiC₂, PDA, and MnO₂ can significantly improve the capacitance, stability, and eco-friendly operation in supercapacitors. However, the current work does not evaluate the performance in portable or flexible devices, and future studies may address this limitation through full-cell assembly and real-world testing. Overall, the composite provides a strong foundation for next-generation energy storage applications.