Showing papers on "Chemisorption published in 1974"
TL;DR: In this paper, the surface composition of binary alloys is determined by minimizing alloy surface free energy with respect to atom exchange between the surface and the bulk, using a pairwise bound model of the solid with a broken bond surface.
546 citations
Book•
01 Jan 1974
TL;DR: In this paper, the basic principles of catalysis adsorption on solid surfaces and chemisorption at metal surfaces were discussed, as well as the kinetics of catalysed reactions.
Abstract: Basic principles of catalysis adsorption on solid surfaces chemisorption at metal surfaces chemisorption at oxide surfaces kinetics of catalysed reactions quantitative aspects of catalysis by metals heterogeneous catalysis: structure, preparation, and use catalysis in energy conversion and in the production of hydrocarbon feedstocks reactions on acidic solids and bifunctional catalysts: the petroleum industry oxidation catalysis: the petrochemical industry catalysis in the heavy inorganic chemicals industry hydrogenation of multiple bonds: the production of margarine, and the fine-chemicals industry catalysts in atmospheric pollution control prospects for the future Bibliography Index.
401 citations
TL;DR: The initial stages of the interaction of oxygen gas with a clean Ni (100) surface have been studied by a combination of LEED, AES, work function change and ion bombardment sectioning techniques as mentioned in this paper.
399 citations
Journal Article•
TL;DR: The initial stages of the interaction of oxygen gas with a clean Ni surface have been studied by a combination of LEED, AES, work function change and ion bombardment sectioning techniques as discussed by the authors.
387 citations
TL;DR: In this article, it was shown that small perturbations to the energy of the iron (III) 2p electrons can be attributed to changes in crystal structure and multiplet splitting and shake-up in the iron oxides contributes to iron 2p peak widths; the chemisorption of water has a marked effect upon the observed peak profiles; the oxygen 1s peaks due to oxide, hydroxyl, and adsorbed water have been characterised.
Abstract: X-Ray photoelectron spectroscopy has been used to study a series of iron oxides. It has been shown that iron metal has a different ionisation energy from a number of iron(III) oxides. Small perturbations to the energy of the iron (III) 2p electrons can be attributed to changes in crystal structure. Multiplet splitting and shake-up in the iron oxides contributes to iron 2p peak widths. The chemisorption of water has a marked effect upon the observed peak profiles; the oxygen 1s peaks due to oxide, hydroxyl, and adsorbed water have been characterised.
348 citations
06 Aug 1974
TL;DR: In this article, the formation of a chemisorbed overlayer on a homotattic surface with fourfold symmetry was studied, taking into account the existence of short range order in the overlayer.
Abstract: Kinetic models are developed for the formation of a chemisorbed overlayer on a homotattic surface with fourfold symmetry, taking into account the existence of short range order in the overlayer. It is shown that where the pairwise lateral interaction energy between nearest neighbour adatoms is large (repulsive or attractive), and the overlayer is consequently highly ordered, dissociative adsorption follows a pseudo first-order rate mechanism. Accurate sticking probabilities as a function of surface stoichiometry are reported for the interaction of nitrogen with the {100} plane of tungsten, obtained by a molecular beam technique, over a wide range of both surface and gas temperatures. The results are shown to be in quantitative agreement with the kinetic model, allowing for initial trapping into a mobile physisorbed state, and consistency is established with structural (low-energy electron diffraction) studies.
341 citations
TL;DR: In this article, carbon monoxide adsorbed on Ni(111) forms around θ = 1/3 an ordered √3 × √ 3/R 30c structure whose unit cell is continuously compressed upon further increasing the coverage until at saturation (θ=0.53 corresponding to 1 × 1015 molecules/cm2) a densely packed layer is reached.
Abstract: Carbon monoxide adsorbed on Ni(111) forms around θ = 1/3 an ordered √3 × √3/R 30c structure whose unit cell is continuously compressed upon further increasing the coverage until at saturation (θ=0.53 corresponding to 1 × 1015 molecules/cm2) a densely packed layer is reached. The work function increases by 1.31 eV. At θ=1/3 the adsorption energy decreases from its value of 26.5 kcal/mole by 3 kcal/mole. CO adsorption causes the appearance of two peaks at 6 and 14 eV in the electron energy loss spectra, which are ascribed to excitations of electrons from chemisorption levels. The sticking coefficient remains nearly constant up to medium coverages which can be described by a ``precursor'' state model. The results show close similarities with those reported for other nickel surfaces.
320 citations
TL;DR: In this paper, an Anderson formalism including overlap is used to treat the chemisorption of carbon monoxide on the transition metals Cu, Ni and Pd, where the wave functions of the metal surface are approximated by a linear combination of atomic d-orbitals, which are oriented in such a manner that maximum overlap with the 2π ∗ -orbital of CO is achieved.
244 citations
TL;DR: In this article, an experimental study of the chemisorption of a variety of closely related absorbates (H, O, C, CO, S, Se and Te) on clean single crystal nickel surfaces is presented.
225 citations
TL;DR: In this article, the effect of adsorbate-adsorbate interactions on the formation of ordered adorbate structures and multiple peak thermal desorption spectra is considered with reference to a lattice-gas Ising model.
182 citations
IBM1
TL;DR: In this paper, the degree to which surface atomic arrangement influences the bonding geometry of sulfur atoms on Ni surfaces was investigated by an analysis of experimental low-energy electron diffraction data, showing that the sulfur atoms reside in high-coordination sites, i.e., the atomic hollows of the surface.
Abstract: The degree to which the surface atomic arrangement influences the bonding geometry of sulfur atoms on (001), (110), and (111) Ni surfaces is investigated by an analysis of experimental low-energy electron diffraction data. For all surfaces, the sulfur atoms reside in high-coordination sites---the atomic hollows of the surface; all nearest-neighbor Ni-S bond lengths are less than those of stable bulk compounds.
TL;DR: In this article, the interaction of oxygen with the (111) surface of a single crystal is studied, mainly in the pressure range from 10 −3 up to 1 torr and at temperatures from room up to 500°C.
TL;DR: In this paper, it was shown that iridium phase oxides can be formed in 1 or 0.1 M H2SO4 with a coverage of one oxygen atom per iridium surface site at 1.5 V on a triangular potential sweep.
TL;DR: In this paper, hydrogen adsorption isotherms were measured on unsupported and supported Ru catalysts and compared with argon surface areas and particle size distributions measured by electron microscopy.
TL;DR: In this article, the extended Huckel molecular orbital method is used to examine interactions of Li2, B2, C2, N2, CO, NO, O2, and F2 with nine atom clusters representing W(100) and Ni(100).
Abstract: The extended Huckel molecular orbital method is used to examine interactions of Li2, B2, C2, N2, CO, NO, O2, and F2 with nine atom clusters representing W(100) and Ni(100) crystal surfaces. The following predictions are made and are corroborated by experimental facts when available: (1) A strong tendency for charge transfer between the substrate and adsorbate exists as would be expected from electronegativity differences. (2) The adsorbed molecules display a tendency to dissociate because of Coulombic repulsions and frequently because of the filling of antibonding levels as well. At the same time Li2 and F2 form ionic bonds with the surface and covalent character is also evident for the others. (3) Strong bonding interactions form between the adsorbates and surfaces for any adsorbate orientation or position. Thus a connection is made with physical theories which exclude atomic detail. Such surface homogeneity can be resolved into detail with molecular orbital methods, but the emphasis in this paper is on examining orbital interactions between adsorbates and substrates with small regard to energy changes. (4) Active sites, which are atoms on a surface which have stronger chemisorptive capability, are found on steps and corners of metal clusters. These atoms, which stick out from the bulk, gain extra electronic charge as a result of orbital orthogonality and they form stronger bonds with electrophilic adsorbates, sometimes also strengthening the diatomic bond a little. This suggests rough surface areas might initially attract electrophilic adsorbates, but that dissociation could happen in a nearby region. (5) Photoemission spectra for CO on W(100) and Ni(100) and ethylene on Ni(111) are considered in some detail. The calculations corroborate the spectra. Comments are made on spectra of N2, N2O, NO, and O2 on W(100), CO on W(110), and ethylene on W(100) and Ni(100). Bandwidths and positions are discussed. In general the extended Huckel molecular orbital method appears to be a valuable tool in surface chemisorption and catalysis studies.
TL;DR: A theory of the angular distributions of electrons photoemitted from sub-monolayer films of chemisorbed atoms is presented in this article, which is treated within the surface-molecule limit of the Anderson model.
Abstract: A theory of the angular distributions of electrons photoemitted from submonolayer films of chemisorbed atoms is presented. Chemisorption is treated within the surface-molecule limit of the Anderson model. It is shown that the key features which differentiate between solid-state photoemission and atomic photoionization are the localization of the hole left behind in the photoexcitation process and the preferential orientation of atomic or molecular orbitals (in photoemission from solids or chemisorbed atoms). The differential photoionization cross sections or angular distributions for spatially oriented atoms and surface molecules are obtained and contours of constant emission intensity, as projected on a flat fluorescent screen which is parallel to the surface, are presented. It is shown that the chemisorption bonding geometry can be ascertained from such measurements.
TL;DR: In this article, a solution of the Anderson model for chemisorption including correlation effects is presented, which becomes exact in three limiting cases (largeU, smallU i.e., Hartree-Fock and the so-called symmetric strong coupling limit) of the intra atomic Coulomb repulsionU and the hopping termV.
Abstract: A solution of the Anderson model for chemisorption including correlation effects is presented. The solution becomes exact in three limiting cases (largeU, smallU i.e. Hartree-Fock and the so-called symmetric strong coupling limit) of the intra atomic Coulomb repulsionU and the hopping termV. Excellent agreement of our approximation with Schrieffer's exact numerical results for the binding energy of a small model system is found. Our results for the binding energy and the charge of the adsorbate show a significant improvement over the Hartree-Fock approximation. The single particle spectral density of the H-F approximation turns out to be even qualitatively wrong in the largeU strong coupling limit.
TL;DR: In this article, the effect of varying partial pressure of hydrogen on the chemisorption and ordering characteristics of hydrocarbons are also discussed in the presence of hydrogen and polycyclohexane.
TL;DR: In this article, the chemisorption of both CO and O 2 on a clean tungsten ribbon has been studied using an ultrahigh vacuum X-ray photoelectron spectrometer.
TL;DR: In this article, the level width and level shift functions for the Anderson theory of chemisorption on metal surfaces were derived for the case where the substrate is either a free electron metal or a tight-binding p-band metal.
TL;DR: In this article, the irreversible chemisorption of water, formic acid and acetic acid on a thin amorphous aluminum oxide film was investigated using inelastic tunneling spectroscopy.
TL;DR: In this article, the effect of preadsorbed oxygen layers on the physisorption of xenon on tungsten has been studied using flash desorption and work function methods.
TL;DR: In this paper, the area of platinum in alumina supported catalysts was determined by chemisorption of hydrogen or carbon monoxide and small angle X-ray scattering and the agreement between the results was good enough to corroborate a hypothesis on the stoichiometry of the adsorption reaction over a wide range of particle size.
TL;DR: In this paper, Dyson's equation is used to embed an adsorbate/absorbent cluster in the surface of the semi-infinite adsorbent, which is formulated correctly, but to have a practical scheme, an approximate version is needed.
Abstract: To overcome the limitation of conventional quantum chemistry computer programs using the Hartree-Fock approximation which can only handle small clusters of atoms, Dyson's equation is used to embed an adsorbate/absorbent cluster in the surface of the semi-infinite adsorbent. The embedding problem is formulated correctly, but to have a practical scheme, an approximate version is needed. This version uses a tight-binding electron Green function in the adsorbent beyond the cluster, but the correct self-consistent Green function in the adsorbate/adsorbent cluster. Calculations have been made for hydrogen on the (100) surfaces of two simple, and two face-centred cubic s band solids.
TL;DR: In this article, the photoadsorption of oxygen by temperature-programmed desorption was studied on reduced rutile surfaces and it was shown that photo-holes are produced by irradiating the specimen with ultra-violet light λ 330 nm.
Abstract: A study of the photoadsorption of oxygen by temperature-programmed desorption reveals that, on fully oxidised rutile surfaces, adsorbed hydroxyl groups act as traps for the photo-holes which are produced by irradiating the specimen with ultra-violet light λ 330 nm. The photo-electrons, which are simultaneously produced, are then free to participate in the chemisorption of oxygen. On reduced rutile surfaces it has been established that the photoadsorption of oxygen is enhanced by the additional presence of Ti3+ ions which also fulfil the role of traps for photo-holes.The photo-oxidation of isopropanol has been shown to be quite complex. The initial product is acetone, but the subsequent photo-oxidation of the acetone produces formic acid. Acetaldehyde is also produced, but probably arises from the photo-oxidation of adsorbed propene which is formed by the thermal dehydration of isopropanol. Ultimately the products of prolonged photo-oxidation are carbon dioxide and water.
TL;DR: In this article, the authors describe adsorption studies of serveral inorganic and organic species on single crystal Ni(111) using ultraviolet photoemission spectroscopy (hv=21.2 eV).
Abstract: We describe adsorption studies of serveral inorganic and organic species on single crystal Ni(111) using ultraviolet photoemission spectroscopy (hv=21.2 eV). Adsorbate orbital ionization energies and line shapes have been measured and surface reactions have been studied. Ionization energies for chemisorbed unsaturated hydrocarbons (C2H2, C2H4, and C6H6) exhibit large surface-induced relaxation shifts (~1–3 eV) relative to their gas phase counterparts as well as π-orbital bonding shifts (~0.9–1.5 eV). We estimate these π-d bonding interaction strengths and chemisorption energies using Mulliken's donor-acceptor theory as described by Grimley for weak chemical bonds and show that an observed surface reaction, i.e. the dehydrogenation of chemisorbed ethylene (C2H4) to chemisorbed acetylene (C2H2) for T\gtrsim230 K, becomes exothermic only for the chemisorbed species due to the π-d electron interaction.
TL;DR: The role of the substrate temperature in determining the relative stability of the different states of the molecules is emphasized in this paper, with the assumption that identical electron-binding data by XPS reflect identical surface-bonding situations.
Abstract: Electron spectroscopic (XPS and UPS) studies of the interaction of CO, CO2, O2 and H2O with Mo, and H2O and CO2 with Au are reported. The object was first to explore how far one could distinguish and between different states of chemisorption; whether there was any relation between bond strength and electron binding energy and whether electron spectroscopy, particularly UPS, could provide unambiguous information on the molecular nature of surface species. Physical adsorption data for CO2 and H2O on Au at 77 K provide reference binding-energy data.Arguments are given for believing that, with molybdenum, CO can exist in both molecular and dissociated forms, that CO2 dissociates into C and O and that water exists in both molecular and dissociated forms. The role of the substrate temperature in determining the relative stability of the different states of the molecules is emphasized. Implicit is the assumption that identical electron-binding data by XPS reflect identical surface-bonding situations. In this context the role of complementary UPS data is important. Where information was available on the relative strengths of surface bonding then for any given adsorbate the electron binding energy was greatest when bonding to the surface was weakest.
TL;DR: In this article, an ultrahigh vacuum ESCA spectrometer has been modified such that thermal desorption behavior from the W (111) crystal can be directly compared with the Xe (3 d 5 2 ) level.