Structure, Stability, and Activity of Titania-Supported VO x in the Presence of Oxygen Vacancies and Adsorbed Water or Atomic Oxygen

The computational complexity required to find the low energy structures for large oligomers of supported metal oxides remains a barrier to understanding their reactivity at intermediate to high coverages. To circumvent this challenge, we use machine learning potentials (MLP) to perform high throughput screening of vanadium oxide clusters supported on titanium dioxide for intermediate coverages up to a monolayer. The most stable structures obtained from an MLP are then optimized with density functional theory to examine their electronic properties. We find that even at coverages up to 3/4 of a monolayer, it is possible to form highly active monomeric species when there is a vacancy in the TiO2 support and an oxygen atom adsorbed on the surface. The extent of dissociation of supported oligomeric vanadia and hence the concentration of monomeric vanadium oxide species depend on the concentration of oxygen vacancy-oxygen adatom pairs.