We investigated the molecular adsorption of methane, ethane, propane and n-butane on stoichiometric and oxygen-rich RuO2(110) surfaces using temperature-programmed desorption (TPD) and dispersion-corrected density functional theory (DFT-D3) calculations. We find that each alkane adsorbs strongly on the coordinatively-unsaturated Ru (Rucus) atoms of s-RuO2(110), with desorption from this state producing a well-defined TPD peak at low alkane coverage. As the coverage increases, we find that alkanes first form a compressed layer on the Rucus atoms and subsequently adsorb on the bridging O atoms of the surface until the monolayer saturates. DFT-D3 calculations predict that methane preferentially adsorbs on top of a Rucus atom and that the C2 to C4 alkanes preferentially adopt bidentate configurations in which each molecule aligns parallel to the Rucus atom row and datively bonds to neighboring Rucus atoms. DFT-D3 predicts binding energies that agree quantitatively with our experimental estimates for alkane σ-complexes on RuO2(110). We find that oxygen atoms adsorbed on top of Rucus atoms (Oot atoms) stabilize the adsorbed alkane complexes that bind in a given configuration, while also blocking the sites needed for σ-complex formation. This site blocking causes the coverage of the most stable, bidentate alkane complexes to decrease sharply with increasing Oot coverage. Concurrently, we find that a new peak develops in the C2 to C4 alkane TPD spectra with increasing Oot coverage, and that the desorption yield in this TPD feature passes through a maximum at Oot coverages between ∼50% and 60%. We present evidence that the new TPD peak arises from C2 to C4 alkanes that adsorb in upright, monodentate configurations on stranded Rucus sites located within the Oot layer.

High-resolution core-level spectroscopy (HRCLS) and density functional theory (DFT) calculations have been used to investigate the adsorption and dissociation of hydrogen on a PdO(101) film grown on Pd(111). Energy-dependent measurements of the O 1s and Pd 3d 5/2 binding energies enable identification of surface components that correspond to undercoordinated Pd and O atoms. HRCLS data obtained at 110 K, after hydrogen exposure at the same temperature, reveal hydrogen adsorption and formation of Pd-H and O-H groups. Adsorption at room temperature results instead in complete reduction of the oxide. The experimental results are supported by the DFT calculations of core-level shifts and barriers for water formation.

We used X-ray photoelectron spectroscopy and temperature-programmed desorption (TPD) to investigate the oxidation of Tb 2 O 3 (111) films on Pt(111) by gaseous oxygen atoms. We find that plasma-generated O atom beams are highly effective at completely oxidizing the Tb 2 O 3 films to TbO 2 at 300 K, for film thicknesses up to at least seven layers. Heating to ∼1000 K in ultrahigh vacuum restores the films to the Tb 2 O 3 stoichiometry and produces two distinct O 2 TPD features centered at ∼385 and 660 K, which we attribute to the release of lattice oxygen from the surface vs bulk trilayers, respectively. We also find that the adsorption of plasma-activated oxygen at 90 K produces a weakly bound state of oxygen on the TbO x films which desorbs between ∼100 and 270 K during TPD. This oxygen state is consistent with a form of chemisorbed oxygen, possibly an atomic and/or molecular species that bonds on-top of Tb atoms at the surface. TPD experiments of the oxidation of Tb 2 18 O 3 films by 16 O atom beams demonstrate that oxygen desorption below about 500 K originates almost entirely from the oxygen that is "added" to the Tb 2 O 3 film and that all isotopic combinations of O 2 desorb from the bulk above 500 K, though the relative amount of 18 O to 16 O which desorbs above 500 K is lower than that determined from the isotopic composition of the oxidized TbO x films. These results support the idea that oxygen desorption below 500 K originates from oxygen species that are localized at the surface and further suggest that the oxide structure only partially accommodates oxygen atoms that incorporate into lattice sites at 300 K.