Vanadium oxide nanostructures on another oxide: The viewpoint from model catalysts studies

• Model catalysts studies on vanadium oxide nanostructures on another oxide are reviewed.
• Surface science and theoretical results are reported and compared.
• Electronic and structural effects on the catalytic sites are outlined.
• Exotic nanostructures induced by the interface with the oxide support are singled out.

An overview of the current research in the field of vanadium oxide (VOx) monolayer catalysts on oxide supports based on a Surface Science approach applied to model catalysts is reported. These systems are usually prepared in ultra-high-vacuum by depositing the VOx catalysts on planar supports that mimic the oxide supports used in real catalysts. The model catalysts are then characterized by a range of spectroscopic/microscopic tools capable of relating the structure and reactivity of the active sites. Such a methodology also benefits from parallel theoretical investigations that can provide information to interpret the experimental data and vice versa use the experimental data to validate the theoretical models.The systems taken into consideration are VOx/TiO2 and VOx/CeO2, as prototypical examples of catalysts supported on reducible oxides, and VOx/Al2O3 and VOx/SiO2 for non-reducible supports. Such a methodology allows outlining the existence of several unusual surface stabilized nanostructures, which can be identified as the main players for the specific activities of the VOxmonolayer catalysts. Some general trends and basic factors that influence the structure and activity of the VOx catalysts are discussed, i.e. the role of the support, whose interaction with VOx can influence the catalyst reactivity, the vanadia loading, which allows to obtain different nanostructures, and the hybridization at the interface between the oxides, often leading to charge transfer.