Carbon Monoxide Chemisorption Research Articles

The stoichiometry of hydrogen and carbon monoxide chemisorption on alumina- and silica-supported nickel

Adsorption stoichiometries of H 2 at 298 K and CO at 190–298 K on alumina- and silica-supported Ni catalysts prepared by impregnation and precipitation techniques were investigated. In the case of alumina-supported nickel catalysts the metal loading was varied from 0.5 to 23 wt% in order to study the effects of metal-support interactions. Ni SiO 2 catalysts were prepared by both impregnation and precipitation techniques to determine effects of catalyst preparation. Room-temperature H 2 adsorption on alumina- and silica-supported nickel occurs with a stoichiometry of one hydrogen atom per surface nickel atom as determined by chemisorption, X-ray diffraction, and electron microscopy. CO adsorption is considerably more complex, the stoichiometry of which varies with equilibration pressure, temperature, metal crystallite size, and metal loading. Formation of nickel carbonyl and substantial amounts of chemical and physical adsorption of CO on the support provide additional complications.

Adsorption and oxidation of carbon monoxide on smooth palladium in sulfuric acid solution

The adsorption of carbon monoxide was investigated on a smooth palladium wire electrode under steady-state conditions in 0.5 M H 2 SO 4 at room temperature. The coverage with carbon monoxide is equal to the saturation coverage between 0.2 and 0.65 V, measured vs. a hydrogen electrode in 0.5 M H 2 SO 4 . The surface of the palladium electrode is largely blocked for the dissolution of hydrogen inside the electrode at potentials of the α phase. The coverage decreases rapidly to zero in a narrow potential range above 0.65 V. The oxidation of chemisorbed carbon monoxide occurs in the absence of a noticeable coverage of oxygen atoms below 0.9 V. Above 0.9 V the oxidation CO ad is accompanied by the formation of the oxygen layer. The oxidation rate, determined at about half saturation coverage, follows a Tafel law at potentials below 0.9 V. The shape of voltammetric current-potential curves, measured in the presence of CO stirring, is interpreted on the basis of the adsorption results.

Effect of chemisorbed carbon monoxide on the rate of hydrogen dissolution in palladium electrodes at potentials of the α phase

Effect of chemisorbed carbon monoxide on the rate of hydrogen dissolution in palladium electrodes at potentials of the α phase

Effect of chemisorbed carbon monoxide on the rate of hydrogen dissolution in palladium electrodes at potentials of the α phase

Cathodic current-potential curves were measured on a smooth palladium wire electrode, covered to different degrees with chemisorbed carbon monoxide, in 0.5 M H 2SO 4 at sweep rates between 0.01 and 30 V s −1 in the potential range between 0.6 and 0.08 V. In the absence of CO ad the net reaction of hydrogen dissolution at potentials of the α phase was diffusion-controlled at sweep rates <0.1 V s −1. The dissolution rate was reduced to about half at small sweep rates with increasing coverage of CO ad up to about 0.6. A further increase of the coverage led to a considerable decrease of the dissolution rate. However, the dissolution rate did not become negligibly small at saturation coverage with CO ad.

Molecular cluster calculations for the analysis of CO chemisorption on Ni, Pd, Pt and Ir surfaces

Abstract Self-consistent Hartree-Fock-Slater molecular cluster calculations for the chemisorption of carbon monoxide on Ni, Pd, Pt and Ir surfaces are presented. The variation of the energy levels with respect to the height of the CO molecule above a particular surface is calculated with the CO molecule linearly bonded to the surface. The calculations are performed using a XCO cluster, where X = (Ni, Pd, Pt, Ir), with the carbon-oxygen distance ( R CO ) equal to the free molecular value. The variation of the energy levels with varying ( R CO ) distances is investigated in more detail for the NiCO cluster. The chemisorption of CO on palladium is also investigated by performing calculations for a Pd 5 CO cluster representing linear bonding to the surface. Relativistic calculations are presented for the IrCO cluster. The relativistic splitting of the chemisorbed 1 π CO level is found to be less than 0.1 eV. The bonding character of the different clusters are investigated through a Mulliken population analysis. Investigations of the bonding and antibonding character for the CO valence levels have also been analyzed by evaluating the derivatives of the molecular eigenvalues with respect to a change in bond distance to the surface and the ( R CO ) distance, respectively. It is found for the valence levels of the chemisorbed CO molecule that the derivatives of the eigenvalues are about five times larger for a change in the carbon-oxygen distance compared with a change in the carbon-metal distance. The energy separation between the 1 π and 4σ peaks of the chemisorbed CO are evaluated and compared with experimental results. Theoretical ionization energies relative to the Fermi energy are calculated for certain bond distances and compared with experimental values.

Molecular cluster calculations for the analysis of CO chemisorption on Ni, Pd, Pt and Ir surfaces

Self-consistent Hartree-Fock-Slater molecular cluster calculations for the chemisorption of carbon monoxide on Ni, Pd, Pt and Ir surfaces are presented. The variation of the energy levels with respect to the height of the CO molecule above a particular surface is calculated with the CO molecule linearly bonded to the surface. The calculations are performed using a XCO cluster, where X = (Ni, Pd, Pt, Ir), with the carbon-oxygen distance ( R CO ) equal to the free molecular value. The variation of the energy levels with varying ( R CO ) distances is investigated in more detail for the NiCO cluster. The chemisorption of CO on palladium is also investigated by performing calculations for a Pd 5CO cluster representing linear bonding to the surface. Relativistic calculations are presented for the IrCO cluster. The relativistic splitting of the chemisorbed 1 π CO level is found to be less than 0.1 eV. The bonding character of the different clusters are investigated through a Mulliken population analysis. Investigations of the bonding and antibonding character for the CO valence levels have also been analyzed by evaluating the derivatives of the molecular eigenvalues with respect to a change in bond distance to the surface and the ( R CO ) distance, respectively. It is found for the valence levels of the chemisorbed CO molecule that the derivatives of the eigenvalues are about five times larger for a change in the carbon-oxygen distance compared with a change in the carbon-metal distance. The energy separation between the 1 π and 4σ peaks of the chemisorbed CO are evaluated and compared with experimental results. Theoretical ionization energies relative to the Fermi energy are calculated for certain bond distances and compared with experimental values.

Adsorption and oxidation of carbon monoxide on smooth palladium in sulfuric acid solution

The adsorption of carbon monoxide was investigated on a smooth palladium wire electrode under steady-state conditions in 0.5 M H 2SO 4 at room temperature. The coverage with carbon monoxide is equal to the saturation coverage between 0.2 and 0.65 V, measured vs. a hydrogen electrode in 0.5 M H 2SO 4. The surface of the palladium electrode is largely blocked for the dissolution of hydrogen inside the electrode at potentials of the α phase. The coverage decreases rapidly to zero in a narrow potential range above 0.65 V. The oxidation of chemisorbed carbon monoxide occurs in the absence of a noticeable coverage of oxygen atoms below 0.9 V. Above 0.9 V the oxidation CO ad is accompanied by the formation of the oxygen layer. The oxidation rate, determined at about half saturation coverage, follows a Tafel law at potentials below 0.9 V. The shape of voltammetric current-potential curves, measured in the presence of CO stirring, is interpreted on the basis of the adsorption results.

Hydrogen-oxygen titration and carbon monoxide chemisorption for the measurement of supported palladium surface areas

Hydrogen-oxygen titration and carbon monoxide chemisorption of silica supported palladium have been investigated, using the pulse chromatographic technique. An excellent agreement between metal surface areas derived from both methods was observed.

Embedded versus non-embedded-cluster treatment of chemisorbed systems: A model computation

The chemisorption of carbon monoxide on the basal plane of graphite has been considered in a CNDO 2 approximation using an isolated- and an embedded-cluster approach. It is shown that conformational data practically coincide in the two approaches, whereas chemisorption energies and electronic structure data exhibit relevant discrepancies.

Coordination chemistry of metal surfaces - carbon monoxide chemisorption states on platinum(111)

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCoordination chemistry of metal surfaces - carbon monoxide chemisorption states on platinum(111)C. M. Friend, R. M. Gavin, E. L. Muetterties, and Min-Chi TsaiCite this: J. Am. Chem. Soc. 1980, 102, 5, 1717–1719Publication Date (Print):February 1, 1980Publication History Published online1 May 2002Published inissue 1 February 1980https://doi.org/10.1021/ja00525a042RIGHTS & PERMISSIONSArticle Views91Altmetric-Citations10LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (465 KB) Get e-Alerts Get e-Alerts

Chemisorption of carbon monoxide on W{110} and W{320}. Adsorption, desorption and state interconversion

Kinetic studies have been made of the interaction of carbon monoxide with the {100} and the stepped {320} planes of tungsten. No marked influence of the steps on kinetic processes or on the nature of the chemisorbed overlayer was observed. At 300 K, the saturation coverage on both planes is ≈ 10 × 1014 molecules cm–2, although the initial sticking probability, so, is higher (0.9) on W{320} than on W{110}(0.46). Desorption spectra for both planes are similar, showing, after 300 K adsorption, α1, 2, β1 and β2 peaks. Evidence is produced for the existence of an α3 state on both planes, which can be increased in population by adsorption at temperatures above 500 K. Conversion from the “virgin” CO state formed at 85 K to β-CO is characterised by secondary electron emission studies; the activation energy for this process on W{110} is ≈ 77 kJ mol–1, compared with an estimated desorption energy of ≈ 110 kJ mol–1. Very little difference could be found between the “virgin” and the α1,2 state. Reasons are discussed for the observed pseudo-first-order desorption behaviour in the dissociatively bound β states on both crystal planes.

The vibrational spectra of chemisorbed carbon monoxide and ethylene

We use Raman spectroscopy to investigate the vibrational behaviour of simple molecules chemisorbed on catalytic metallic surfaces. The vibrational modes of the adsorbed species can be described in the approximation of a surface molecule. The interaction between the localized vibrational modes and the phonons of the metal is assumed to be small. The assignment of the vibrations to irreducible representations of the adsorbed molecule and the change of selection rules is discussed for carbon monoxide, benzene and ethylene.

Does chemisorbed carbon monoxide dissociate on rhodium?

Isotopic exchange measurements have shown that at surface temperatures below 800 K, the upper limit on the probability of dissociation/recombination of CO on Rh(111) is approximately 10 −3. Related Auger spectroscopic measurements, monitoring the accumulation of atomic carbon on the surface, have shown that the maximum probability of dissociation of CO per collision with the Rh surface in a temperature range between 300 and 870 K is 10 −4. Hence, it has been demonstrated that the probability of dissociation of CO on Rh(111) is negligible compared to the probability of molecular desorption, in contrast to recent reports in the literature concerning both polycrystalline Rh and stepped surfaces of Rh.

Does chemisorbed carbon monoxide dissociate on rhodium?

Does chemisorbed carbon monoxide dissociate on rhodium?

The chemisorption of CO and CO 2 on Rh(111) studied by high resolution electron energy loss spectroscopy

We have applied the techniques of high resolution electron energy loss spectroscopy (ELS), thermal desorption mass spectrometry (TDS) and low energy electron diffraction (LEED) to a study of CO and CO 2 chemisorption on the Rh(111) single crystal surface. The vibrational spectra of carbon monoxide indicate two distinct binding sites (atop and bridged) whose relative populations and vibrational frequencies are determined by both the substrate temperature and the background pressure. TDS measurements show the bridge bonded CO to have an approximately 4 kcal mole lower binding energy to the surface than the species located in the atop site. Surface pretreatment also had a marked effect on CO adsorption: oxygen and carbon both inhibited carbon monoxide chemisorption and weakened the metal-adsorbate bond strength. Hydrogen had no observable effects. The adsorption of carbon dioxide yields virtually identical spectra to that of chemisorbed CO, indicating dissociative adsorption. By combining the present data with earlier infrared and inelastic electron tunneling spectroscopic studies, a consistent set of force constants for the two types of chemisorbed carbon monoxide can be calculated.

Determination of the dispersity of supported platinum catalysts by hydrogen, oxygen or carbon monoxide chemisorption and hydrogen-oxygen titrations, using volumetric, gravimetric and catharometric techniques

The dispersity of supported Pt catalysts is measured with better exactness by means of O2 (one atom O per surface Pt atom, Pts), or CO (one CO molecule per Pts) chemisorption; among the three techniques, the volumetric one is the most sensitive. But H2 chemisorption and H2−O2 titrations have to be used additionally in the case of thermally sensitive catalysts and if the support is not completely inert towards H2 at 400–500 °C.

Electron microscopy of supported metal particles II. Further studies of Pt/TiO

Hydrogen and carbon monoxide chemisorption on Pt on titanium oxide powders [Pt/TO(P)] and transmission electron microscopy of Pt on titanium oxide films [Pt/TO(F)] have been investigated for a common series of thermal treatments in various gaseous atmospheres. Following reduction at 875 K in H2, Pt/TO(P) did not adsorb H2 or CO, and X-ray diffraction examination showed that the Pt had not agglomerated. This behavior is attributed to a strong metal-support interaction (SMSI). The adsorption of H2 and CO could be partially restored if the sample in the SMSI state were treated with H2O vapor at 525 K or O2 at 875 K, the latter treatment being more effective. Transmission electron microscopy studies of Pt/TO(F) treated in the same way as the Pt/TO(P) showed that in the SMSI state the Pt was in the form of hexagonal thin pillbox structures grown on a lower oxide of titania, Ti4O7. When Pt in the SMSI state was oxidized, there was an appreciable increase in the growth rate of the Pt particles, comparable to that found on conventional supports. Examination of the individual Pt particles showed that while their shape remained hexagonal, their thickness increased following oxidation so they were no longer present as thin pillbox structures. Electron diffraction analysis demonstrated that the support had also undergone a structural change, Ti4O7 reverting to TiO2. Reduction of the sample to induce the SMSI state showed that although a few large Pt crystallites remained, there was significant redispersion of the metal. Following re-reduction, all particles had again assumed the pillbox structure of the SMSI state and the support had reverted, once again, to Ti4O7. A schematic model is presented to illustrate the sequence of events during cycling into and out of the SMSI state.

Study of clean and CO-covered Ge(111) surfaces by photoemission and ion-neutralizaiton spectroscopies

Chemisorption of carbon monoxide (CO) on the Ge(111) 2\ifmmode\times\else\texttimes\fi{}8 surface was investigated using ultraviolet photoemission spectroscopy (UPS) and ion-neutralization spectroscopy (INS). It was found that CO molecules are not adsorbed on the Ge(111) surface unless they are activated. Once activated by hot tungsten filaments, CO molecules are chemisorbed nondissociatively at room temperature with a small sticking coefficient (\ensuremath{\sim}0.001). Both UPS and INS show that CO saturates the (111) surface to produce four CO-associated features at $E\ensuremath{-}{E}_{\mathrm{VAC}}=\ensuremath{-}7.0,\ensuremath{-}9.5,\ensuremath{-}12.0,\mathrm{and}\ensuremath{-}14.2$ eV in the surface electronic density of states. The feature at highest energy is identified as an enhanced Ge $p$-like valence band due to CO molecules on the surface. The remaining three peaks at -9.5, -12.0, and-14.2 eV are related to the $5\ensuremath{\sigma}$, $1\ensuremath{\pi}$, and $4\ensuremath{\sigma}$ orbitals of the free CO molecule, respectively. These spectral features are significantly different from those for CO adsorption on a number of transition metals. Simultaneous use of INS and UPS provides us with complementary information on the present chemisorption system, on the basis of which we propose that the CO molecule occupies upon adsorption the threefold interstitial site with the carbon atom toward the bulk and the oxygen atom toward the vacuum.

Molecular cluster calculations for the interpretation of CO chemisorption on a Ni(100) surface

Self-consistent Hartree-Fock-Slater molecular cluster calculations for the chemisorption of carbon monoxide on a Ni(100) surface are presented. In earlier calculations of this type the CO molecule has been assumed to be chemisorbed in a hollow position of C 4v symmetry. A recent EELS experiment shows however that in the most stable configuration CO is linearly bonded to the Ni atoms, i.e. a top position of the CO-molecule. This experiment indicates also that there exists an additional bridge bonding of the CO molecule to the two nearest neighbour Ni atoms. The variation of the energy levels, binding energies and charge distribution with the height of the CO molecule above the nickel surface is calculated for the top position using the NiCO and Ni 5CO clusters and for the bridge bonding configuration using the Ni 2CO cluster. The CO 1π level is found to be split by about 0.8 eV in bridge bonding geometry. For both hollow and top positions the 1π and 5σ levels are separated by about 0.5 eV. The energy separation to the 4σ level is about 3 eV, which is in good agreement with experimental data. Theoretical ionization energies relative to the Fermi energy for top position geometry at a bond distance of 3.5 au between the carbon atom and nickel surface were found to be 25.7, 11.7, 8.7 and 8.2 eV for the 3σ, 4σ, 5σ and 1π levels which should be compared with the experimental data of 29.0, 10.8, 8.4 and 7.8 eV, respectively. The corresponding ionization energies for a bond angle of 99° in bridge bonding were 23.7, 12.1, 7.3, 7.0 and 7.9 eV. The two last values represent the 1π level which is split into two levels in this geometry. The variation of the C-O stretch vibrational frequencies with the height of the CO molecule above the surface for the top-position geometry is estimated from the 5σ and 2π gross orbital populations and from the CO σ and π overlap populations.

High resolution electron energy loss spectroscopy of chemisorbed carbon monoxide and oxygen on the ruthenium (001) surface

The adsorption of CO and O2 on the Ru(001) surface and the interaction between CO and chemisorbed oxygen on this surface have been studied by measuring the vibrational energies of the adsorbed layer with electron energy loss spectroscopy. Adsorbed CO shows two vibrational energies that are assigned to the metal–carbon and carbon–oxygen stretching frequencies of an upright CO with a single metal–carbon bond. Oxygen adsorbed on Ru (001) has a single vibrational energy that can be attributed to a mode of atomic oxygen perpendicular to the surface. The variation of the frequency spectrum of CO with CO coverage and with the coverage of oxygen in coadsorption experiments is discussed in terms of direct interadsorbate interactions and indirect through-bond interactions.