Enhanced adsorption of CO at steps of ultrathin ZnO: the importance of Zn-O geometry and coordination.

The interaction between CO and ultrathin ZnO supported on Au(111) has been studied using temperature programmed desorption (TPD) and density functional theory (DFT) calculations. We find that CO binds weakly on the planar ZnO bilayer and trilayer surfaces, desorbing at T = 130 K. CO binds more strongly at the steps formed between ZnO bilayers and trilayers, desorbing at T = 285-320 K depending upon the CO exposure.

Tunable Lattice Constant and Band Gap of Single- and Few-Layer ZnO.

Single and few-layer ZnO(0001) (ZnO(nL), n = 1-4) grown on Au(111) have been characterized via scanning tunneling microscopy (STM), scanning tunneling spectroscopy (STS), and density functional theory (DFT) calculations. We find that the in-plane lattice constants of the ZnO(nL, n ≤ 3) are expanded compared to that of the bulk wurtzite ZnO(0001). The lattice constant reaches a maximum expansion of 3% in the ZnO(2L) and decreases to the bulk wurtzite ZnO value in the ZnO(4L).

Water Chain Formation on TiO2(110).

The adsorption of water on a reduced rutile TiO2(110)-(1×1) surface has been investigated using scanning tunneling microscopy (STM) and density functional theory (DFT) calculations. The STM measurements show that at a temperature of 50 K, an isolated water monomer adsorbs on top of a Ti(5f) atom on the Ti row in agreement with earlier studies. As the coverage increases, water molecules start to form one-dimensional chain structures along the Ti row direction.

Electron-induced dissociation of CO2 on TiO2(110).

The electron-induced dissociation of CO(2) adsorbed at the oxygen vacancy defect on the TiO(2)(110) surface has been investigated at the single-molecular level using scanning tunneling microscopy (STM). Electron injection from the STM tip into the adsorbed CO(2) induces the dissociation of CO(2). The oxygen vacancy defect is found to be healed by the oxygen atom released during the dissociation process.

In situ observation of water dissociation with lattice incorporation at FeO particle edges using scanning tunneling microscopy and X-ray photoelectron spectroscopy.

The dissociation of H2O and formation of adsorbed hydroxyl groups on FeO particles grown on Au(111) were identified with in situ X-ray photoelectron spectroscopy (XPS) at water pressures ranging from 3 × 10(-8) to 0.1 Torr. The facile dissociation of H2O takes place at FeO particle edges, and it was successfully observed in situ with atomically resolved scanning tunneling microscopy (STM).

Influence of the cobalt particle size in the CO hydrogenation reaction studied by in situ X-ray absorption spectroscopy.

The influence of particle size in the carbon monoxide hydrogenation reaction has been studied using cobalt nanoparticles (NPs) with narrow size distribution prepared from colloidal chemistry. The surfactant covering the NPs after synthesis could be removed by heating to 200-270 degrees C in H(2). Soft X-ray absorption spectroscopy was performed using a gas flow cell under reaction conditions of H(2) and CO at atmospheric pressure.

Water growth on metals and oxides: binding, dissociation and role of hydroxyl groups.

We discuss the role of the presence of dangling H-bonds from water or from surface hydroxyl species on the wetting behavior of surfaces. Using scanning tunneling and atomic force microscopies and photoelectron spectroscopy, we have examined a variety of surfaces, including mica, oxides and pure metals. We find that in all cases, the availability of free, dangling H-bonds at the surface is crucial for the subsequent growth of wetting water films.

Surface chemistry of Cu in the presence of CO2 and H2O.

The chemical nature of copper and copper oxide (Cu 2O) surfaces in the presence of CO 2 and H 2O at room temperature was investigated using ambient pressure X-ray photoelectron spectroscopy. The studies reveal that in the presence of 0.1 torr CO 2 several species form on the initially clean Cu, including carbonate CO 3 (2) (-), CO 2 (delta-) and C (0), while no modifications occur on an oxidized surface.

Partial oxidation of propene on oxygen-covered Au(111).

Partial oxidation of propene is promoted by Au following deposition of atomic oxygen (0.3 ML) via O3 decomposition on Au(111) at 200 K. Several partial oxidation products--acrolein, acrylic acid, and carbon suboxide (O=C=C=C=O)-are produced in competition with combustion to CO2 and H2O.

Selective oxidation of styrene on an oxygen-covered Au(111).

For the first time, we demonstrate olefin epoxidation promoted by an extended Au surface. The oxidation of styrene to styrene epoxide, benzoic acid, and benzeneacetic acid is promoted on Au(111) covered with 0.2 ML of oxygen atoms.

Enhancement of O2 dissociation on Au111 by adsorbed oxygen: implications for oxidation catalysis.

We show that the dissociation probability of O2 on the reconstructed, Au111-herringbone surface is dramatically increased by the presence of some atomic oxygen on the surface. Specifically, at 400 K the dissociation probability of O2 on oxygen precovered Au111 is on the order of 10(-3), whereas there is no measurable dissociation on clean Au111, establishing an upper bound for the dissociation probability of 10(-6). Atomic oxygen was deposited on the clean reconstructed Au111-herringbone surface using electron bombardment of condensed NO2 at 100 K.