Adsorption characteristics of CO and N₂ on RuO₂(110)

Low-energy electron diffraction and density-functional theory calculations are used to examine the adsorption properties of CO and N₂ on RuO₂(110). Both molecules adsorb over the coordinatively unsaturated Ru sites (cus-Ru atoms) with their molecular axes normal to the surface plane. The chemisorption mechanism is well described within a donor-acceptor model, i.e., the Blyholder model. Since N₂ is not reacting with lattice oxygen of RuO₂, quite in contrast to CO, N₂ may serve as a chemical, nondestructive probe to titrate but also to selectively block the cus-Ru atoms; recently, the cus-Ru atoms were shown to be the active centers for the chemisorption of molecules.