Browsing by Author "Yaya, Abu"

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    Electronic and Magnetic Properties of Transition Metal-Doped MoS2 Monolayer: First-Principles Calculations
    (PSS, 2023) MARTIN, HENRY; Boakye, Dennis; Labik, Linus K.; Britwum, Akyana; Nunoo, Oswald Ashirifi; Elloh, Van W.; Kwakye-Awuah, Bright; Yaya, Abu; Abavare, Eric K. K.; 0000-0003-0173-1238
    Density functional theory in the framework of generalized gradient approximation (GGA) of Perdew–Burke–Ernzerhof to investigate the effects of some selected transition metal (TM) and rare-earth metal (RE) dopants on the electronic and magnetic properties of a 2D molybdenum disulfide (MoS2) monolayer is reported. The results demonstrate that it is energetically stable to incorporate Ni and Cu in MoS2 structure under Mo-rich conditions. The pristine MoS2 monolayer has a calculated direct bandgap of 1.70 eV and experiences significant reduction in the gap due to the defects. There is observed induced magnetic behavior due to the tight binding effect originating from the localized dopants and the nearest-neighbor Mo atoms, with magnetic moments ranging between 0.82 and 3.00 μB. Some of the dopants result in 100% spin polarization which is useful for engineering spin filter devices on magnetic MoS2 nanostructures.
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    Molybdenum Induced Modifications in the Quantum Capacitance of Graphene-Based Supercapacitor Electrodes: First-Principle Calculations
    (PSS, 2024) MARTIN, HENRY; Ansi, David; Labik, Linus K.; Yaya, Abu; Elloh, Van W.; Abavare, Eric K. K.; 0000-0003-0173-1238
    Herein, spin-polarized calculation is performed based on density-functional theory in the frame of generalized gradient approximation to examine the quantum capacitance (CQ) and surface charge storage of graphene(G)-based supercapacitor electrodes modified with molybdenum, sulfur, nitrogen, and monovacancy. In total, 15 electrode models, including graphitic doping, monovacancy doping, and Mo adsorption on pristine and single-vacancy graphene structures are analyzed. In the results, it is demonstrated that vacancy defects and N/S/Mo doping enhances the CQ of graphene. Among all configurations, pyrrolic-S (d1S) shows the lowest CQ performance due to few states at the Fermi level. Electrodes with Mo adsorption exhibit the highest CQ, particularly when Mo is adsorbed at the top site of graphene. However, formation and adsorption energy calculations suggest that Mo is more likely to adsorb at hollow sites. Optimally, Mo can be most effectively utilized by loading it onto vacancy or N/S-decorated vacancy sites. The significant contribution of Mo’s 4dz2 and 4s states to CQ, along with the charge-redistribution around the Mo complexes, may facilitate proton-coupled electron transfer to enhance pseudocapacitance. In these findings, valuable insights into designing high quantum capacitance of 2D materials with electroactive sites for improved energy storage are offered.