Highly boosted energy storage performance of few-layered MoS₂ utilized for improved electrode fabrication: experimental and theoretical studies

Few-layer two-dimensional (2D) molybdenum disulfide (MoS₂) has great potential in designing high-performance supercapacitors due to its high theoretical specific capacity, tunable bandgap, and fascinating 2D layered structure. However, the lack of efficient synthesis methods, cost-effectiveness, and mass production of few-layered MoS₂ hindered its practical applications. Moreover, a large gap between theoretical specific capacitance and the experiment comes from the traditional manufacturing approaches involving polymer binders to prepare the electrode for electrochemical testing. We report an accessible and efficient approach to liquid-phase exfoliation of bulk MoS₂ into high-quality, few-layered MoS₂ using the green method. We have constructed few layered MoS₂ on a Ni-foam as an electrode for electrochemical analysis without any polymer binder or black carbon, which exhibits significant improvements in supercapacitor performance compared to the bulk. The highest specific capacitance achieved is 985 F g⁻¹ at 8 A g⁻¹. The 2D layered structure provides stable channels that facilitate K⁺ intercalation/desorption during charging and discharging processes, helping to prevent the deposition and accumulation of ions. Finally, theoretical calculations were performed to calculate the electronic structure, adsorption energy, diffusion barrier, and charge transfer of K intercalated and adsorbed bulk and monolayer 2H-MoS₂, respectively. The calculated migration energy of the K atom diffusion on monolayer MoS₂ (0.05 eV) is considerably lower than that of the bulk (0.8 eV), demonstrating a significant enhancement in electrochemical performance with reducing layer thickness.