Interaction between Monomeric Vanadium Oxide Clusters Supported on Titania and Its Influence on Their Reactivity

TL;DR: In this article, the authors examined a VOx and a VOy cluster in the same supercell and found that the most stable configuration is obtained when the supercell contains one VO2 and one VO3 cluster.

Abstract: Density functional theory is used to study monomeric vanadium oxide clusters formed by exposing to oxygen a rutile TiO2(110) surface on which vanadium atoms have been preadsorbed. Past calculations examined such systems by using one V atom per supercell. This forces all VOx clusters to be identical and precludes interactions between them. To examine the consequences of this choice, we examine a VOx and a VOy cluster in the same supercell. We find that the most stable configuration is obtained when the supercell contains one VO2 and one VO3 cluster. The stabilization occurs because of a Lewis acid–base interaction: VO2 donates electron charge to VO3 and this lowers the energy substantially. No such interactions were found when the supercell contained VOx clusters with the same number of oxygen atoms. These finding demonstrate that in some cases it is essential to have two clusters in the supercell and that results obtained with one cluster in the supercell can be misleading. We have also studied the reacti...