title: CO Adsorption on Reconstructed Ir(100) Surfaces from UHV to mbar Pressure: A LEED, TPD, and PM-IRAS Study.
abstract: Clean and stable surface modifications of an iridium (100) single crystal, i.e., the (1 × 1) phase, the (5 × 1) reconstruction, and the oxygen-terminated (2 × 1)-O surface, were prepared and characterized by low energy electron diffraction (LEED), temperature-programmed desorption (TPD), infrared reflection absorption spectroscopy (IRAS) and polarization modulation IRAS (PM-IRAS). The adsorption of CO in UHV and at elevated (mbar) pressure/temperature was followed both ex situ and in situ on all three surface modifications, with a focus on mbar pressures of CO. The Ir(1 × 1) surface exhibited c(4 × 2)/c(2 × 2) and c(6 × 2) CO structures under low pressure conditions, and remained stable up to 100 mbar and 700 K. For the (2 × 1)-O reconstruction CO adsorption induced a structural change from (2 × 1)-O to (1 × 1), as confirmed by LEED, TPD, and IR. For Ir (2 × 1)-O TPD indicated that CO reacted with surface oxygen forming CO2. The (5 × 1) reconstruction featured a reversible and dynamic behavior upon CO adsorption, with a local lifting of the reconstruction to (1 × 1). After CO desorption, the (5 × 1) structure was restored. All three reconstructions exhibited CO adsorption with on-top geometry, as evidenced by IR. With increasing CO exposure the resonances shifted to higher wavenumber, due to adsorbate-adsorbate and adsorbate-substrate interactions. The largest wavenumber shift (from 2057 to 2100 cm-1) was observed for Ir(5 × 1) upon CO dosing from 1 L to 100 mbar.
authors.affiliation: Institute of Materials Chemistry, TU Wien , Getreidemarkt 9/BC, 1060 Vienna, Austria.
authors.forename: Kresimir
authors.initials: K
authors.lastname: Anic
authors.affiliation: Institute of Materials Chemistry, TU Wien, Getreidemarkt 9/BC, 1060 Vienna, Austria; Boreskov Institute of Catalysis SB RAS, Lavrentieva Ave., 5, Novosibirsk 630090, Russia.
authors.forename: Andrey V
authors.initials: AV
authors.lastname: Bukhtiyarov
authors.affiliation: Institute of Materials Chemistry, TU Wien , Getreidemarkt 9/BC, 1060 Vienna, Austria.
authors.forename: Hao
authors.initials: H
authors.lastname: Li
authors.affiliation: Institute of Materials Chemistry, TU Wien , Getreidemarkt 9/BC, 1060 Vienna, Austria.
authors.forename: Christoph
authors.initials: C
authors.lastname: Rameshan
authors.affiliation: Institute of Materials Chemistry, TU Wien , Getreidemarkt 9/BC, 1060 Vienna, Austria.
authors.forename: Günther
authors.initials: G
authors.lastname: Rupprechter