Computational analysis of 1T-MoS2: Probing the interplay of layer-dependent electronic structure, quantum capacitance, charge density and mechanical properties

Abstract

To meet the high energy demand of society, a conversion to renewable energy sources has become essential and energy should be appropriately stored for future use. This has led to the development of energy-storing devices such as supercapacitors (SCs). To enhance capacitive behavior, the concept of quantum capacitance ($C_Q)$ is unveiled, which results from the confinement of electrons in their energy states. In this work, 1T phase of MoS₂ is studied as it has received a lot of attention because of its wide applications in the energy storage devices and electronics. Here, the electronic structure, $C_Q$ and surface charge density (σ) of one, two and three-layered structures of 1T phase is studied using Density Functional Theory. No bandgap is obtained in the Density of States (DOS) and the bands plot of 1T structure indicates their metallic character and the DOS is continuous in all three layers. The $C_Q$ of three-layered structure dominates over the other two layers throughout the potential window. The larger $C_Q$ and σ values are obtained as 1718.06 μF cm⁻² and -1299.50 μC cm⁻² for three-layered structure at −0.27 V and −1 V respectively. For analyzing the mechanical strength, Young's modulus is evaluated for optimized structure by applying uni-axial strain. The value is obtained as 177.37 GPa, which is a measure of elastic deformation behavior. The results suggest that the capacitive performance of 1T MoS₂ for SC applications is better and it can function as flexible cathode material for asymmetric SC applications.