paper

Harnessing Layer-Controlled Two-dimensional Semiconductors for Photoelectrochemical Energy Storage via Quantum Capacitance and Band Nesting

arXiv:2502.20107

Abstract

Two-dimensional (2D) transition metal dichalcogenides like molybdenum diselenide (MoSe $_{2}$ ) have shown great potential in optoelectronics and energy storage due to their layer-dependent bandgap. However, producing high-quality 2D MoSe $_{2}$ layers in a scalable and controlled manner remains challenging. Traditional methods, such as hydrothermal and liquid-phase exfoliation, lack precision and understanding at the nanoscale, limiting further applications. Atmospheric pressure chemical vapor deposition (APCVD) offers a scalable solution for growing high-quality, large-area, layer-controlled 2D MoSe $_{2}$ . Despite this, the photoelectrochemical performance of APCVD-grown 2D MoSe $_{2}$ , particularly in energy storage, has not been extensively explored. This study addresses this by examining MoSe $_{2}$ 's layer-dependent quantum capacitance and photo-induced charge storage properties. Using a three-electrode setup in 0.5M H $_{2}$ SO $_{4}$ , we observed a layer-dependent increase in areal capacitance under both dark and illuminated conditions. A six-layer MoSe $_{2}$ film exhibited the highest capacitance, reaching $96 I^¼ F/c m^{2}$ in the dark and $115 I^¼ F/c m^{2}$ under illumination at a current density of $5 I^¼ A/c m^{2}$ . Density Functional Theory (DFT) and Many-Body Perturbation Theory calculations reveal that Van Hove singularities and band nesting significantly enhance optical absorption and quantum capacitance. These results highlight APCVD-grown 2D MoSe $_{2}$ 's potential as light-responsive, high-performance energy storage electrodes, paving the way for innovative energy storage systems.

28 pages, 6 figures (Main Manuscript) 8 figures (Supporting Information)