State-resolved studies of CO2 sticking to CO2 ice

Internal vibrations may affect the adsorption, scattering, and reactions of molecules impinging onto a surface. The energy of the ν3 antisymmetric stretch vibration of CO2 slightly exceeds the desorption energy of CO2 bound to CO2 ice. We use supersonic molecular beam techniques and rovibrationally state-resolved excitation to determine whether this vibration affects condensation of gas phase CO2 to its ice. We detect sticking and CO2 ice formation using RAIRS and quantify the sticking probability using the King and Wells method with modulation of the vibrational excitation and Fourier transform based detection. We find that the influence of this vibration on the structure of the formed ice and on the sticking probability is negligible under our conditions. Based on our detection limit, we quantify the weighted average sticking probability at approximately 0.9 and the difference between the state-resolved and weighted average sticking probability as below 0.5%

Coverage-dependent adsorption and desorption of oxygen on Pd(100)

Catalysis and Surface Chemistr

Oxygen-Induced Surface Reconstructions on Curved Ag(111)

The adsorption of oxygen and the resultant O-induced surface reconstructions are key components in heterogeneously catalyzed reactions on silver metal surfaces. O uptake and reconstructions on planar Ag(111) are well-characterized, and in this paper, we show that curved Ag(111) features similar O adsorption and reconstructions. Through a systematic scanning tunneling microscope study of a curved Ag(111) single crystal exposed to gas-phase atomic oxygen at a temperature of 525 K, we observed Oad and, upon higher coverages, saw p(4 4) and p(4 5 p3) reconstructions form on both the A-type and B-type steps. Exposures at low temperatures (\u3c 500 K) resulted in the formation of subsurface oxygen and the appearance of a stripe pattern and amorphous phase on the surface. Upon heating, stable surface reconstructions were formed. Although the geometric arrangement of atoms along the steps were different, A-type and B-type steps formed the same reconstructions. In addition, the B-type steps also saw the formation of several different features atop the oxygen reconstructions

Double-Stranded Water on Stepped Platinum Surfaces

The interaction of platinum with water plays a key role in (electro)catalysis. Herein, we describe a combined theoretical and experimental study that resolves the preferred adsorption structure of water wetting the Pt(111)-step type with adjacent (111) terraces. Double stranded lines wet the step edge forming water tetragons with dissimilar hydrogen bonds within and between the lines. Our results qualitatively explain experimental observations of water desorption and impact our thinking of solvation at the Pt electrochemical interface

Initial stages of water solvation of stepped platinum surfaces

Catalysis and Surface Chemistr

A Comparison of CO Oxidation by Hydroxyl and Atomic Oxygen from Water on Low-Coordinated Au Atoms

The catalytic oxidation of CO is studied at low-coordinated Au atoms using a single-crystal approach. Electron irradiation activates an otherwise unreactive overlayer of undissociated D₂O on Au(310). A low-coverage D₂O/O mixture is subsequently allowed to react at surface temperatures from 105 K upward, with CO supplied from the gas phase. X-ray photoelectron spectroscopy shows the absence of Au oxides and quantifies various O-containing species during the reaction. The dependency of the reaction rate on the surface temperature yields an activation energy for the Langmuir–Hinshelwood reaction of O­(ads) and CO­(ads) between 26 ± 4 and 42 ± 5 kJ/mol. The presented results provide evidence that O­(ads) and not OH­(ads) is the active reactant on small Au nanoparticles. In addition, the observations suggest that water has a negative effect on the reactivity of O­(ads)