1 research outputs found
Mapping Catalytically Relevant Edge Electronic States of MoS<sub>2</sub>
Molybdenum
disulfide (MoS<sub>2</sub>) is a semiconducting transition
metal dichalcogenide that is known to be a catalyst for both the hydrogen
evolution reaction (HER) as well as for hydro-desulfurization (HDS)
of sulfur-rich hydrocarbon fuels. Specifically, the edges of MoS<sub>2</sub> nanostructures are known to be far more catalytically active
as compared to unmodified basal planes. However, in the absence of
the precise details of the geometric and electronic structure of the
active catalytic sites, a rational means of modulating edge reactivity
remain to be developed. Here we demonstrate using first-principles
calculations, X-ray absorption spectroscopy, as well as scanning transmission
X-ray microscopy (STXM) imaging that edge corrugations yield distinctive
spectroscopic signatures corresponding to increased localization of
hybrid Mo 4d states. Independent spectroscopic signatures of such
edge states are identified at both the S L<sub>2,3</sub> and S K-edges
with distinctive spatial localization of such states observed in S
L<sub>2,3</sub>-edge STXM imaging. The presence of such low-energy
hybrid states at the edge of the conduction band is seen to correlate
with substantially enhanced electrocatalytic activity in terms of
a lower Tafel slope and higher exchange current density. These results
elucidate the nature of the edge electronic structure and provide
a clear framework for its rational manipulation to enhance catalytic
activity