CVD-Grown 2D MoSe 2 Nanolayers for Energy Storage

Two-dimensional (2D) transition metal dichalcogenides such as molybdenum diselenide (MoSe2) have emerged as promising materials for optoelectronics, quantum devices, and energy storage due to their layer-dependent bandgap and stable excitons. However, the scalable and controlled synthesis of high-quality 2D MoSe2 remains challenging. Traditional hydrothermal and liquid-phase exfoliation methods, commonly used in energy storage, lack precision in controlling atomic layers and their exact role, limiting further applications. Chemical vapor deposition (CVD) provides a scalable alternative, enabling the controlled growth of high-quality 2D MoSe2 layers. However, the photoelectrochemical performance and energy storage potential of CVD-grown 2D MoSe2 remain largely unexplored. This work investigates the MoSe2 layer-dependent unique quantum capacitance and photoinduced charge storage properties. Under light illumination, the trilayer MoSe2-based device exhibited a significant increase in drain current from 5 μA (dark) to 300 μA (light), demonstrating its potential for light-assisted charge storage. Electrochemical measurements in 0.5 M H2SO4 reveal a layer-dependent increase in areal capacitance under both dark and illumination conditions, with six-layer MoSe2 achieving 37 μF/cm2 in the dark and 52 μF/cm2 under illumination at a current density of 5 μA/cm2. The fabricated symmetric supercapacitor device with multilayer MoSe2 Film electrode exhibits an energy density of 0.0018 μW·h/cm2 with a power density of 8 μW/cm2. The excellent durability of the device is confirmed by retaining ∼ 91% capacitance after 4000 charge–discharge cycles at 1 μA/cm2. First-principles calculations using Density Functional Theory and Many-Body Perturbation Theory attribute this enhancement to Van Hove singularities and band nesting, boosting optical absorption and quantum capacitance. These findings highlight the potential of CVD-grown 2D MoSe2 layers as light-responsive electrochemical energy storage materials, paving the way for next-generation energy storage systems.