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Showing papers on "Chemisorption published in 1983"


Journal ArticleDOI
TL;DR: In this paper, infrared and volumetric studies of NO adsorption have been used to elucidate the type of surface structures present in sulfided Co Al 2 O 3, Ni Al 2O 3, Mo Al 2 o 3, CoMo S 2, and Ni Al O 3 catalysts.

394 citations


Journal ArticleDOI
TL;DR: In this paper, a model for the redispersion of Pt in oxygen is proposed and two surface oxides, α- and β-[PtO2]s, and two chloride-containing surface complexes are found and a comprehensive scheme of surface reactions is proposed.

333 citations


Journal ArticleDOI
TL;DR: In this paper, the formation of a subsurface hydrogen species at 130 K on a Pd(110) single crystal surface was shown to be well separated by distinct activation energy barriers from species which are chemisorbed or which are dissolved in the Pd bulk.
Abstract: We report experimental evidence for the formation of a ‘‘subsurface’’ hydrogen species at 130 K on a Pd(110) single crystal surface. This is well separated by distinct activation energy barriers from species which are chemisorbed or which are dissolved in the Pd bulk, thereby confirming a model of H absorption in Pd in which a subsurface state acts as a reaction intermediate.

271 citations


Journal ArticleDOI
TL;DR: In this paper, the saturation coverage of NO on Rh(111) is approximately 0.67 of the surface atom density and saturation coverage ratio of atomic oxygen is approximately 2.83 times the surface density.

271 citations


Journal ArticleDOI
TL;DR: The X-ray absorption spectrum of the Rh K edge of a highly dispersed reduced 0.57 wt % Rh/ y-A1203 catalyst shows EXAFS oscillations due to rhodium-rhodium nearest neighbors, which proves the existence of rhodIUMmetal crystallites.
Abstract: The X-ray absorption spectrum of the Rh K edge of a highly dispersed reduced 0.57 wt % Rh/ y-A1203 catalyst shows EXAFS oscillations due to rhodium-rhodium nearest neighbors, which proves the existence of rhodium metal crystallites. Adsorption of CO at room temperature on the reduced catalyst significantly decreases the amplitude of these EXAFS oscillations. This implies that CO adsorption on very small rhodium crystallites leads to a disruption of a significant number of the metal-metal bonds.

233 citations


Journal ArticleDOI
TL;DR: In this paper, surface alloys were formed by heating the Pt(111) crystal that was covered with a Au multilayer, and the surfaces were characterized with Auger electron spectroscopy (AES), low-energy electron diffraction (LEED), and temperature-programmed desorption (TPD) of CO.

195 citations


Journal ArticleDOI
TL;DR: In this article, photoemission techniques with synchrotron radiation were used to study the adsorption of oxygen on the Si(111)•(7×7) and Si(100)−(2×1) surfaces at room temperature in the submonolayer and monolayer regimes.
Abstract: We have used photoemission techniques with synchrotron radiation to study the adsorption of oxygen on the Si(111)‐(7×7) and Si(100)‐(2×1) surfaces at room temperature in the submonolayer and monolayer regimes. High resolution Si 2p core‐level spectra, valence‐band spectra, work‐function, and Fermi‐level pinning positions have been measured for exposures between 1 and 1000 L and after annealing at 700 °C. Four oxidation states have been detected for the silicon surface atoms with Si 2p core‐level shifts of 0.9, 1.9, 2.6, and 3.4 eV which are assigned to silicon atoms bonded to 1, 2, 3, and 4 oxygen atoms. Both (111) and (100) surfaces are characterized by about the same sticking coefficient, a simple adsorption process for 1‐L exposures, the quenching of the surface states after 15 L and a saturation of the amount of oxygen after 100 L. Significant differences exist in the initial bonding geometries for the (111) and (100) surfaces. After 15‐L exposure, oxygen atoms are incorporated below the Si (111)‐(7×7...

176 citations


Journal ArticleDOI
TL;DR: The adsorption of chlorine on the Ag(111) surface has been studied using LEED, Auger and temperature programmed desorption in this paper, showing that the chlorine adsorbs dissociately with an initial sticking probability of 0.4, and a precursor state is implicated in the chemisorption process.

138 citations


Journal ArticleDOI
TL;DR: In this paper, it was shown that through adsorbate-induced surface-structure changes, effective channels open for hydrogen to move from the surface to the interior of metals.
Abstract: Conclusive evidence is provided for the first time that through adsorbate-induced surface-structure changes, effective channels open for hydrogen to move from the surface to the interior of metals. In Pd(110), all available subsurface sites between the first and the second metal layers can be selectively populated by thermal activation from a specific type of chemisorption place, which is associated with a substrate reconstruction at high hydrogen surface coverage.

133 citations


Journal ArticleDOI
TL;DR: In this article, the authors showed that CO is molecularly adsorbed on Co(0001) in the investigated temperature range from 100 to 450 K. This was deduced from the UPS and EELS results and the reversibility of the sp and LEED data.

132 citations


Journal ArticleDOI
TL;DR: In this article, the DV-Xα cluster method was used to analyze the electronic properties of oxide surfaces, including the properties of the electronic states which are related to surface chemical activities, and the role of the partially filled d band and the influence of the chemisorption geometry.

Journal ArticleDOI
TL;DR: In this paper, infrared spectroscopy has been employed to characterize adsorbed CO species under steadystate reaction conditions in the presence of H2 and also under equilibrium adsorption conditions under equilibrium He.

Journal ArticleDOI
TL;DR: In this paper, the chemisorption of O2 and NO was investigated at −78 °C and at room temperature using pulse-flow and volumetric techniques. But the results were not consistent with the anion vacancy concentration, and the results could be rationalized by assuming that these chemisors took place on Mo2+ centers (two anion vacancies on the same Mo).

Journal ArticleDOI
TL;DR: In this paper, the dependence of the results on both the adsorption site (top or hollow) and the size of the cluster has been analyzed using a decomposition of the energy in various terms (steric repulsion, σ bonding, π backbonding).
Abstract: Chemisorption of CO on (100) and (111) Cu surfaces has been investigated by calculations on a series of small clusters. The dependency of the results on both the adsorption site (top or hollow) and the size of the cluster has been analyzed using a decomposition of the adsorption energy in various terms (steric repulsion, σ bonding, π backbonding). Some properties, i.e., M–CO distance, M–CO vibration, C–O distance, can be obtained from small cluster calculations as they are determined by ‘‘local’’ bonding aspects, whereas, e.g., the adsorption energy is not reliable due to delocalized features of the bonding being not well represented by small clusters. The deficiency of small clusters in modeling the polarizability of a metal substrate is stressed.

Journal ArticleDOI
TL;DR: In this paper, the adsorption and condensation of H 2 O(D 2 O) on ZnO(1010), Zn and O surfaces were investigated by means of thermal desorption (TDS) and UV photoelectron spectroscopy (UPS).

Journal ArticleDOI
TL;DR: In this paper, a monohydride Si(100) 2x1:H and a dihydride Si (100) 1x1::2H phase were identified using normal vibrational modes.

Journal ArticleDOI
TL;DR: In this article, angle resolved photoemission and thermal desorption studies of atomic hydrogen adsorbed onto the (111) surface of Cu show that the bonding of H to Cu is very similar to H bonding on transition metals.

Journal ArticleDOI
TL;DR: The role of surface oxygen in the activation of molecularly adsorbed water by Ni(210) and polycrystalline lead surfaces has been investigated by X-ray photoelectron spectroscopy as discussed by the authors.

Journal ArticleDOI
TL;DR: In this paper, the interaction of methanol and of coadsorbed hydrogen and carbon monoxide with a Pd(111) surface has been examined with thermal desorption and decomposition spectroscopy (TDS), LEED and AES.

Book ChapterDOI
01 Jan 1983
TL;DR: The interaction of the adsorptive with the adsorbent can very greatly in nature, i.e. from weak interaction by van der Waals forces, leading to physisorption, to strong chemical bonding or chemisorsorption as mentioned in this paper.
Abstract: The lattice of a crystal is abruptly terminated at its surface. In consequence, the constituents of the lattice are unsaturated in their coordination, giving rise to the surface energy. Adsorption of substances which are foreign to the lattice may lower the energy of the system and reduce the coordinative “unsaturation”. The interaction of the adsorptive with the adsorbent can very greatly in nature, i.e. from weak interaction by van der Waals forces, leading to physisorption, to strong chemical bonding or chemisorption. Chemisorption of molecules is frequently dissociative and often irreversible as well, that is the adsorptive cannot always be recovered in its original form. An example is the chemisorption of oxygen, O2, on carbon giving rise to surface oxides [1] which yield CO and CO2 on thermal decomposition.

Journal ArticleDOI
TL;DR: In this article, the metal surface reactions are modeled with a novel theoretical construct in which periodic trends can be scrutinized and a conspectus of periodic trends, based on the model, is explored.
Abstract: Metal surface reactions are modeled with a novel theoretical construct in which periodic trends can be scrutinized. The theoretical model is succinctly presented and a conspectus of periodic trends, based on the model, is explored. Periodic trends are discussed in the contexts of chemisorption bond energies, electron transfer between metal surface and adsorbate, stereochemical features of chemisorption states for closed-shell diatomic and linear X-CN or X-NC molecules, and hydrocarbon reactions. Hydrocarbon C-H bond-breaking processes are analyzed in terms of d-level occupancy, electron transfer, and stereochemistry of intermediates. Conceptually and computationally, the metal surface is characterized as a good electron donor: antibonding molecular orbitals of the adsorbate species appear to be significant contributors to the chemisorption bond and also play a decisive role in bond-breaking processes. No aspect of the model projections is inconsistent with the experimental data although the electronic characterization of some chemisorption states are counter to commonly held perceptions.

Journal ArticleDOI
TL;DR: In this paper, an XPS investigation of Pt and Rh supported on γ-Al 2 O 3 and TiO 2 was performed in order to establish the differences in metal-support interactions.

Journal ArticleDOI
Karl-Heinz Rieder1, H. Wilsch1
TL;DR: In this article, surface charge density calculations using overlapping atomic charge densities indicate a normal distance of the hydrogens from the topmost Ni layer dn ≅ 0.9-1.0 A.

Journal ArticleDOI
TL;DR: In this paper, the effect of preadsorbed K on CO chemisorption was studied and the adsorption of K on a cluster model of a Pt(111) surface was found to lead to a significant charge transfer which in turn increased the electron density of all surface Pt atoms.

Journal ArticleDOI
TL;DR: In this paper, the titania-supported Ni, NiFe, and Pt samples were investigated at room temperature following reduction at 770 K. The hydrogen uptake was low for each sample (e.g., zero for Pt TiO 2 ) as determined by adsorption measurements.

Journal ArticleDOI
TL;DR: In this article, the sintering kinetics of Ni SiO 2 and Ni γ-Al 2 O 3 catalysts in H2 atmosphere were studied in the temperature range between 923 and 1023 K.

Journal ArticleDOI
TL;DR: In this paper, the effects of pressure-induced absorption-desorption cycling on the degradation properties and the hydrogen purification ability of TiMn alloy hydrides were studied.
Abstract: The effects of pressure-induced absorption-desorption cycling on the degradation properties and the hydrogen purification ability of TiMn alloy hydrides were studied. The lines in the characteristic X-ray diffraction pattern were much broader and weaker in the cycled alloys but the C14 hexagonal structure was maintained and no second phase was observed. The hydrogen capacity was reduced by 30% for TiMn binary alloy and by 20% for TiMn multicomponent alloys after about 10 000 cycles in contrast with the marked reduction observed for LaNi5. In some cases slight recovery could be produced by heating at 500 °C for 1 h in a vacuum after cycling. Gas chromatography measurements on hydrogen released from TiMn1.5 hydride showed that the hydrogen purity was better than 99.9999% (except for an H2O impurity) after a purge release of only a few per cent of hydrogen when the purity of the commercial grade hydrogen absorbed by the hydride was 99.99%. It can be concluded from the results of these measurements that hydrogen purification using TiMn alloy is related to two factors. The removal of N2, CO and CO2 proceeds by surface poisoning (i.e. oxidation, physisorption or chemisorption), whereas the removal of CH4, O2, H2O and Ar is controlled by surface poisoning and concentration. The hydrogen purification effect of TiMn alloy hydrides showed little degradation even after a large number of absorption-desorption cycles.

Journal ArticleDOI
TL;DR: In this paper, the authors considered the properties of 3D transition-metal oxides in terms of the types of surface structures that can exist, including steps and point defects, and their relation to the experimental data that is available for well characterized, single-crystal surfaces.

Journal ArticleDOI
Yves J. Chabal1
TL;DR: The vibrational spectrum of hydrogen chemisorbed on Si(111)7 is studied with high-resolution infrared spectroscopy in this paper, where a unique chemisors site characterized by a dangling bond perpendicular to the surface is identified for the first time and assigned to a silicon atom at the bottom of a deep hole formed by long-range reconstruction.
Abstract: The vibrational spectrum of hydrogen chemisorbed on Si(111)7\ifmmode\times\else\texttimes\fi{}7 is studied with high-resolution infrared spectroscopy. A unique chemisorption site characterized by a dangling bond perpendicular to the surface is identified for the first time and assigned to a silicon atom at the bottom of a deep hole formed by long-range reconstruction.