Insights
from Arsenate Adsorption on Rutile (110):
Grazing-Incidence X‑ray Absorption Fine Structure Spectroscopy
and DFT+U Study
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Abstract
Insights into the bonding of As(V)
at the metal oxide/aqueous interface
can further our understanding of its fate and transport in the environment.
The motivation of this work is to explore the interfacial configuration
of As(V) on single crystal rutile (110) using grazing-incidence X-ray
absorption fine structure spectroscopy (GI-XAFS) and planewave density
functional calculations with on-site repulsion (DFT+U). In contrast
to the commonly considered corner-sharing bidentate binuclear structure,
tetrahedral As(V) binds as an edge/corner-sharing tridentate binuclear
complex on rutile (110), as evidenced by observation of three As–Ti
distances at 2.83, 3.36, and 4.05 Å. In agreement with the GI-XAFS
analysis, our DFT+U calculations for this configuration resulted in
the lowest adsorption energy among five possible alternatives. In
addition, the electron density difference further demonstrated the
transfer of charge between surface Ti atoms and O atoms in AsO<sub>4</sub>. This charge transfer consequently induced the formation
of a chemical bond, which is also confirmed by the partial density
of states analysis. Our results may shed new light on coupling the
GI-XAFS and DFT approaches to explore molecular-scale adsorption mechanisms
on single crystal surfaces
