Versatile Model System for Studying Processes Ranging from Heterogeneous to Photocatalysis: Epitaxial RuO₂(110) on TiO₂(110)

The binary model system RuO₂/TiO₂(110) can be prepared with single crystallinity and excellent control of the morphology of the RuO₂(110) nanoislands. The interface of RuO₂/TiO₂(110) is structurally well-defined since RuO₂ grows with the same lattice constants as TiO₂(110). The actual growth of RuO₂ on TiO₂(110) single crystals starts from square-shaped 3–4 ML thick RuO₂ islands with narrow size and thickness distributions. After TiO₂(110) is completely covered by RuO₂, the further growth proceeds via a step flow mechanism, forming very large and flat RuO₂(110) terraces with well-defined thickness. Both the flat RuO₂(110) films and RuO₂(110) nanoislands are very reactive toward CO oxidation, and the RuO₂(110) nanoislands are robust in the redox reactions, i.e., easily recovering their morphology after reoxidation from the reduced state. The RuO₂/TiO₂(110) heterojunction forms a Schottky barrier of 1.4 eV which is important for photocatalysis