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Integral and angle resolved thermal desorption spectroscopies were used to study methanol adsorption and oxidation on clean and oxygen covered Cu(110) surfaces. Special emphasis was put on the Cu–CuO stripe phase, which forms when the Cu(110) surface is covered with 0.25 ML of oxygen. In the temperature regime between 200 and 300 K associative desorption of methanol and water takes place, showing a normal desorption character with peaks shifting to lower temperature with increasing coverage and with a nearly cosine angular desorption distribution. In the temperature range of about 350 K formaldehyde, hydrogen, and again methanol desorb nearly concomitantly in the form of a very narrow peak (full width at half maximum=10 K), with peaks shifting to higher temperature with increasing methanol coverage. The angular distribution of these peaks is strongly forward focused, indicating activation barriers being involved. In the case of the Cu–CuO stripe phase the angular distribution of the desorption products is clearly different in the [11_0] and [001] azimuthal directions, demonstrating the influence of the border lines between the copper and the copper oxide stripes on the desorption process. [ABSTRACT FROM AUTHOR]

Ultraviolet and x-ray photoelectron spectroscopies were used to study electronic properties of interfaces between Au substrates and a number of organic semiconductors (small molecules and polymers). Au surface work function ([lowercase_phi_synonym]) values before organic deposition were ∼4.7 eV (exposed to air), ∼5.2 eV (atomically clean), and ∼5.5 eV (UV/ozone treated). The high [lowercase_phi_synonym] obtained for UV/O3 treated Au was due to Au oxide formation and surface-adsorbed carbon and oxygen species. Au surface morphology remained essentially unchanged by UV/ozone exposure, as observed by atomic force microscopy. Hole injection barriers (HIBs) at interfaces between UV/ozone treated Au and the organic semiconductors were systematically lower than those for untreated Au (both atomically clean and air exposed). Reductions in HIB of up to 1.4 eV (for p-sexiphenyl) were achieved. In addition, good long-term stability of reduced HIBs of such interfaces was observed for air storage of up to several days. [ABSTRACT FROM AUTHOR]

The adsorption of carbon monoxide on Rh(111) and on oxygen modified Rh(111) was investigated using thermal desorption spectroscopy, reflection absorption infrared spectroscopy (RAIRS), and density functional theory. The results show that CO adsorbs on Rh(111) in on top sites at low coverages. With increasing coverage hollow sites and bridge sites get occupied according to the RAIRS results. A new vibrational feature at high wave numbers was found in the on top region of the CO stretching frequency. This feature can be explained by a local high density CO structure where two CO molecules are adsorbed in the ([Square_Root]3×[Square_Root]3)R30° structure. The coadsorption of oxygen and carbon monoxide leads to a shift of the CO stretching frequency to higher wave numbers with increasing O to CO ratio. CO adsorption on a (2×1) oxygen layer is possible and RAIRS shows that the CO adsorbs in on top and most likely in bridge sites in this case. [ABSTRACT FROM AUTHOR]

The dehydrogenation reaction of methanol on a Rh(111) surface, a Rh(111)/V subsurface alloy, and on a Rh(111)/V islands surface has been studied by thermal-desorption spectroscopy, reflection absorption infrared spectroscopy, and density-functional theory calculations. The full monolayer of methanol forms a structure with a special geometry with methanol rows, where two neighboring molecules have different oxygen–rhodium distances. They are close enough to form a H-bonded bilayer structure, with such a configuration, where every second methanol C–O bond is perpendicular to the surface on both Rh(111) and on the Rh(111)/V subsurface alloy. The Rh(111)/V subsurface alloy is slightly more reactive than the Rh(111) surface which is due to the changes in the electronic structure of the surface leading to slightly different methanol species on the surface. The Rh(111)/V islands surface is the most reactive surface which is due to a new reaction mechanism that involves a methanol species stabilized up to about 245 K, partial opening of the methanol C–O bond, and dissociation of the product carbon monoxide. The latter two reactions also lead to a deactivation of the Rh(111)/V islands surface. [ABSTRACT FROM AUTHOR]

The dehydrogenation of methanol on Rh(111), on a Rh(111)/V subsurface alloy and on Rh(111) with V islands has been studied with and without preadsorbed oxygen using a supersonic molecular beam and temperature programmed desorption. The reactivity is highest for the V islands surface without oxygen. But this surface is deactivated due to CO dissociation. The subsurface alloy is less reactive than the islands, but still more active than the Rh(111) surface. The reaction products are carbon monoxide and hydrogen only. With preadsorbed oxygen Rh(111) is the most active surface, but a strong dependence of the activity on the amount of preadsorbed oxygen is found for all three surfaces. The reaction products with preadsorbed oxygen are water, hydrogen, carbon dioxide and carbon monoxide. The reactions follow the same mechanism on all surfaces, but the activation energy of the individual reaction steps is different leading to significant changes in the thermal desorption spectra and in King and Wells-type experiments. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The evidence that a hydrogen bond between two neighboring methanol molecules on the Pd(111) surface is necessary to break the C-O bond by the combination of thermal desorption spectroscopy and density functional theory is presented. It is proposed that a complete suppression of the C-O bond cleavage in methanol is possible by changing the electronic structure of the surface due to the formation of a Pd/V surface alloy.