  Determining the local coordination of the active site is a pre-requisite for
the reliable modeling of single-atom catalysts (SACs). Obtaining such
information is difficult on powder-based systems, so much emphasis is placed on
density functional theory-based computations based on idealized low-index
surfaces of the support. In this work, we investigate how Pt atoms bind to the
(1-102) facet of Fe2O3, a common support material in SAC. Using a combination
of scanning tunneling microscopy (STM), x-ray photoelectron spectroscopy (XPS),
and an extensive computational evolutionary search, we find that Pt atoms
significantly reconfigure the support lattice to facilitate a pseudo-linear
coordination to surface oxygen atoms. Despite breaking three surface Fe-O
bonds, this geometry is favored by 0.84 eV over the best configuration
involving an unperturbed support. We suggest that the linear O-Pt-O
configuration is common in reactive Pt-based SAC systems because it balances
thermal stability with the ability to adsorb reactants from the gas phase, and
that extensive structural searches are likely necessary to determine realistic
active site geometry in single-atom catalysis.
