Predicting Monolayer Oxide Stability over Low-Index Surfaces of TiO₂ Polymorphs Using ab Initio Thermodynamics

Monolayer metal oxide coatings on metal oxide supports have the possibility of tuning the surface chemical properties of the coated systems. However, the (meta)stability of these structures makes experimental discovery challenging. A computational approach can help to determine properties that make a coating/substrate system stable and evaluate the stability of a variety of combinations. Herein, we use density functional theory (DFT) to study the stability of monolayer transitional metal oxides over different facets of anatase, brookite, and rutile phase of TiO₂. We find that coatings that have a stable polymorph matching that of the support, as well as substrates with higher surface energies, are more likely to form monolayer-coated systems. DFT calculations recommend a number of coating/TiO₂ surface facet combinations that may be stable. Despite these predictive observations, we did not find a significant correlation between monolayer stability and a single atomic, surface, or structural property of the coating/support metal/metal oxide and coating oxide monolayer stability. More complex predictive relationships need future study.