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Adsorption and Dissociation of H2O on Monolayered MoS2 Edges: Energetics and Mechanism from ab Initio Simulations
journal contribution
posted on 2015-03-26, 00:00 authored by Kulbir
Kaur Ghuman, Shwetank Yadav, Chandra Veer SinghThe dissociation of water on 2D monolayer
molybdenum disulfide
(MoS2) edges was studied with density functional theory.
The catalytically active sites for H2O, H, and OH adsorption
on MoS2 edges with 0% (Mo-edge), 50% (S50-edge), and 100%
(S100-edge) sulfur coverage were determined, and the Mo-edge was found
to be the most favorable for adsorption of all species. The water
dissociation reaction was then simulated on all edges using the climbing
image nudged elastic band (CI-NEB) technique. The reaction was found
to be endothermic on the S100-edge and exothermic for the S50- and
Mo-edges, with the Mo-edge having the lowest activation energy barrier.
Water dissociation was then explored on the Mo-edge using metadynamics
biased ab initio molecular dynamics (AIMD) methods
to explore the reaction mechanism at finite temperature. These simulations
revealed that water dissociation can proceed by two mechanisms: the
first by splitting into adsorbed OH and H species produced a particularly
small activation free energy barrier of 0.06 eV (5.89 kJ/mol), and
the second by formation of desorbed H2 and adsorbed O atom
had a higher activation barrier of 0.36 eV (34.74 kJ/mol) which was
nevertheless relatively small. These activation barrier results, along
with reaction rate calculations, suggest that water dissociation will
occur spontaneously at room temperature on the Mo-edge.