Energy is an essential requirement, which has a growing demand due to the growth of population and the world transformation into electronic. More than 70% of energy resources are fossil-fuel based which has an environmental impact due to the CO2 emissions. Energy hubs for Fossil-fuel to electric energy conversion, controlled CO2 emissions processing units, and energy storage system are key factors for a smooth transition to green energy without lack of energy supplies, where electrical energy storage systems (ESS) are key enablers to achieve that. One of the effective components which determines the ESS efficiency is the electrode material. Two-dimensional (2D) materials have opened new avenues for the fabrication of ultrathin, transparent, and flexible functional devices. However, the conventional inorganic graphene analogues are either semiconductors or insulators with low electronic conductivity, hindering their use as supercapacitor electrode materials, which require high conductivity and large surface area. Recently, 2D charge density wave (CDW) materials, such as 2D chalcogenides, have attracted extensive attention as high performance functional nanomaterials in sensors, energy conversion, and spintronic devices. Herein, TaS2 is investigated as a potential CDW material for supercapacitors. A detailed convergence study is performed for TaS2 and similar vdW material (TaSe2, MoS2, MoSe2, WS2, and WSe2) to land on the optimum ionic convergence algorithm for the rest of the study. Conjugate gradient was found converging with all the materials and in agreement with the experimental values in literature more than RMM-DIIS algorithm. Moreover, an equivalent line search-based convergence algorithm (Three Paraments Simultaneous Convergence Algorithm) is developed and applied to TaS2 as a quality assurance for the achieved results. On other hand the quantum capacitance (CQ) of the different TaS2 polymorphs (1T, 2H, and 3R) was estimated using density functional theory calculations for different number of TaS2 layers and alkali-metal ion (Li, Na and K) intercalants. The results demonstrate the potential of 2H- and 3R- polymorphs as efficient negative electrode materials for supercapacitor devices. The intercalation of K and Na ions in1T-TaS2 led to an increase in the CQ with the intercalation of Li ion resulting in a decrease in the CQ. On contrary, Li ion was found to be the best intercalant for the 2H-TaS2 phase (highest CQ), while K ion intercalation was the best for the 3R-TaS2 phase. Moreover, increasing the number of layers of the1T-TaS2 resulted in the highest CQ. On contrary, CQ increases upon decreasing the number of layers of 2H-TaS2. Both 1T-MoS2 and 2H-TaS2 can be combined to construct a highly performing supercapacitor device as the positive and negative electrodes, respectively.
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MS in Physics
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(2022).Quantum Capacitance Investigation of Different TaS2 Polymorphs for Energy Storage Applications – First Principles Study [Master's Thesis, the American University in Cairo]. AUC Knowledge Fountain.
elAttar, Mahmoud. Quantum Capacitance Investigation of Different TaS2 Polymorphs for Energy Storage Applications – First Principles Study. 2022. American University in Cairo, Master's Thesis. AUC Knowledge Fountain.