Digging its own Site: Linear Coordination Stabilizes a Pt1/Fe2O3 Single-Atom Catalyst

TL;DR

This study combines experimental and computational methods to reveal that Pt atoms on Fe2O3 support reconfigure the lattice to form a stable linear O-Pt-O coordination, challenging idealized models and emphasizing the importance of structural searches.

Contribution

It demonstrates the importance of extensive structural searches and experimental validation in accurately determining active site geometries in single-atom catalysts.

Findings

Pt atoms reconfigure the Fe2O3 support to form a linear O-Pt-O coordination.

The linear coordination is energetically favored by 0.84 eV over unperturbed configurations.

The linear O-Pt-O structure balances stability and reactivity in SAC systems.

Abstract

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.