NO restructuring of surface Ir and bond formation to preadsorbed O on Ir{1Â 0Â 0} at 95Â K

RAIRS experiments and density functional theory calculations have been performed to understand the adsorption behavior of nitric oxide on different phases of Ir{1 0 0} at 95 K, namely, Ir{1 0 0}-(1 × 1), Ir{1 0 0}-(1 × 5), and O-precovered Ir{1 0 0}-(1 × 1) surfaces. Molecular NO adsorption is observed on all the phases and the adsorption structures of NO on the surfaces are determined. Mixed isotope experiments verify that no (NO)2 dimer is formed on the surfaces. Importantly, at an NO coverage of ∼0.3 ML, a local lifting of reconstruction from the (1 × 5) to the (1 × 1) phase occurs, which is found to be driven by the preferential adsorption of NO on the (1 × 1) phase. On the O-precovered Ir{1 0 0} surface, an unusual NOδ+ species is identified, featuring a stretching frequency 30-60 cm−1 higher than the NO gas phase frequency. This NOδ+ species is suggested to be NO bonded to preadsorbed O atoms rather than surface Ir atoms.