Augmenting bi-functional catalytic efficiency in vanadium based pseudo-monolayer: Chemical paradigm of functionalization, vacancy and external stimuli

Abstract

Since the exfoliation of graphene, two-dimensional (2D) ultrathin materials have attracted a lot of attention in several applications for energy harvesting for the ongoing quest for green and sustainable environment. One of such ultrathin materials could be envisaged in the form transition metal tri-chalcogenide based 2D pseudo-monolayers. In this theoretical work, we have rigorously investigated the bi-functional catalytic reaction mechanism corresponding to water-splitting on vanadium-based tri-chalcogenide monolayers VS3. The hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are the two main reactions which consist water splitting process, which are being explored in VS3 system from the perspective of first principles electronic structure calculations within the framework of density functional theory (DFT) formalism. We have explored the effect of functionalization, vacancy induced defect and external strain (both bi-axial and uni-axial) on the catalytic activity, which can be reflected from the over-potential corresponding to the reaction coordinate mapping constructed from the adsorption free energy values. We have also determined the projected density of states, work function, charge density distribution and correlated all such electronic structure analysis with the catalytic activity enhancement in the VS3 pseudo monolayer. Overall, we have investigated the competing effect of strain, functionalization, and vacancy induced defect on the bi-functional catalytic activity enhancement, which can be further experimentally validated for efficient hydrogen generation. Our systematic electronic structure calculations reveals the defected and nitrogen doped VS3 as the promising candidate for HER and OER activity respectively, which have been further enhanced under the influence of external strain.