Global Satellite Session - Ghana: Advances in Physics: Insights from Ghanaian Scientists

We perform spin-polarized calculation base 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. Several electrode models, including graphitic doping, monovacancy doping, and Mo adsorption on pristine and single-vacancy graphene structures were examined. The results demonstrate that vacancy defects and N/S/Mo doping enhances the CQ of graphene. Among all configurations, pyrrolic-S (d1S) showed 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 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. We similarly examined the effects of some selected transition metal (TM) dopants on the electronic and magnetic properties of a 2D-Molybdenum disulfide (MoS2) monolayer. The results demonstrate that it is energetically stable to incorporate Ni and Cu in MoS2 structure under Mo-rich conditions than others. The pristine MoS2 monolayer has a calculated direct bandgap of 1.70 eV and experiences significant reduction in the gap due to the defects and becoming indirect band gap material. There are observed induced magnetic behaviour due to the tight binding effect originating from the localized dopants and the nearest-neighbour Mo, with magnetic moments ranging between 0.82 and 3.00 µB. Some of the dopants resulted in 100% spin polarization which is useful for engineering spin filter devices on magnetic MoS2nanostructures