Chemisorbed Carbon Research Articles

Dynamics at Polarized Carbon Dioxide–Iron Oxyhydroxide Interfaces Unveil the Origin of Multicarbon Product Formation

Surface-sensitive ambient pressure X-ray photoelectron spectroscopy and near-edge X-ray absorption fine structure spectroscopy combined with an electrocatalytic reactivity study, multilength-scale electron microscopy, and theoretical modeling provide insights into the gas-phase selective reduction of carbon dioxide to isopropanol on a nitrogen-doped carbon-supported iron oxyhydroxide electrocatalyst. Dissolved atomic carbon forms at relevant potentials for carbon dioxide reduction from the reduction of carbon monoxide chemisorbed on the surface of the ferrihydrite-like phase. Theoretical modeling reveals that the ferrihydrite structure allows vicinal chemisorbed carbon monoxide in the appropriate geometrical arrangement for coupling. Based on our observations, we suggest a mechanism of three-carbon-atom product formation, which involves the intermediate formation of atomic carbon that undergoes hydrogenation in the presence of hydrogen cations upon cathodic polarization. This mechanism is effective only in the case of thin ferrihydrite-like nanostructures coordinated at the edge planes of the graphitic support, where nitrogen edge sites stabilize these species and lower the overpotential for the reaction. Larger ferrihydrite-like nanoparticles are ineffective for electron transport.

Quantum-state-resolved reactivity of overtone excited CH4 on Ni(111): Comparing experiment and theory.

Quantum state resolved reactivity measurements probe the role of vibrational symmetry on the vibrational activation of the dissociative chemisorption of CH4 on Ni(111). IR-IR double resonance excitation in a molecular beam was used to prepare CH4 in three different vibrational symmetry components, A1, E, and F2, of the 2ν3 antisymmetric stretch overtone vibration as well as in the ν1+ν3 symmetric plus antisymmetric C-H stretch combination band of F2 symmetry. The quantum state specific dissociation probability S0 (sticking coefficient) was measured for each of the four vibrational states by detecting chemisorbed carbon on Ni(111) as the product of CH4 dissociation by Auger electron spectroscopy. We observe strong mode specificity, where S0 for the most reactive state ν1+ν3 is an order of magnitude higher than for the least reactive, more energetic 2ν3-E state. Our first principles quantum scattering calculations show that as molecules in the ν1 state approach the surface, the vibrational amplitude becomes localized on the reacting C-H bond, making them very reactive. This behavior results from the weakening of the reacting C-H bond as the molecule approaches the surface, decoupling its motion from the three non-reacting C-H stretches. Similarly, we find that overtone normal mode states with more ν1 character are more reactive: S0(2ν1) > S0(ν1 + ν3) > S0(2ν3). The 2ν3 eigenstates excited in the experiment can be written as linear combinations of these normal mode states. The highly reactive 2ν1 and ν1 + ν3 normal modes, being of A1 and F2 symmetry, can contribute to the 2ν3-A1 and 2ν3-F2 eigenstates, respectively, boosting their reactivity over the E component, which contains no ν1 character due to symmetry.

Enhanced Chemical Reactivity of Pristine Graphene Interacting Strongly with a Substrate: Chemisorbed Carbon Monoxide on Graphene/Nickel(1 1 1)

AbstractGraphene is usually considered a chemically inert material. Theoretical studies of CO adsorption on free‐standing graphene predict quite low adsorption energies (<0.1 eV). However, we show here by vibrational spectroscopy and scanning tunneling microscopy that the nondissociative chemisorption of CO occurs at cold, pristine graphene grown on Ni(1 1 1). The CO adlayer remains stable up to 125 K, although some coverage survives flashes to 225 K. This unexpected result is explained qualitatively by the modification of the density of states close to the Fermi energy induced by the relatively strong graphene–substrate interaction. The value of the adsorption energy allows us to estimate an equilibrium coverage of the order of 0.1 monolayers at 10 mbar pressure, which thus paves the way for the use of graphene as a catalytically active support under realistic conditions.

Study of reactive film heterostructures with several interfaces using the thermal desorption spectroscopy

The thermal desorption spectroscopy is used to study the interaction of the chemisorbed oxygen and carbon monoxide molecules with the nanometer-thick ytterbium films that are formed on the surfaces of silicon substrates at room temperature. In accordance with the results at a temperature of 300 K, the O2 and CO molecules are chemisorbed on the surface of a metal film and do not exhibit dissociation to atoms under such conditions. The molecular dissociation is observed at higher temperatures. The liberated oxygen is involved in reactions with ytterbium and silicon that lead to the formation of complicated silicates, which dissociate at even higher temperatures.

Effect of chemisorbed oxygen and carbon monoxide molecules on the properties of Yb-Si(111) nanofilm structures

A study is reported of the effect of chemisorbed O2 and CO molecules on the properties of structures of the type “nanoscale-ytterbium-film-Si(111) silicon substrate” and, in particular, on the reactions between a metal and silicon. It has been shown that chemisorption of the above molecules on Yb-Si(111) structures initiates partial or total suppression of growth of ytterbium silicide and that the effect of adsorbates on reactions at the metal-silicon interface depends on the thickness of the ytterbium nanolayer. Indeed, at a film thickness of 8 monolayers and higher oxygen doses (360 Langmuir), chemisorbed molecules suppress completely the silicide formation process. With ytterbium films of larger thicknesses (16 monolayers) and higher doses of oxygen (360 Langmuir) or carbon monoxide (480 Langmuir), while the silicide does grow, this apparently takes place only in ytterbium nanofilm layers closest to the substrate. The effect of adsorbed molecules on the silicide formation becomes less pronounced also with decreasing number of these molecules on the surface, i.e., as their dose decreases.

Surface-bound chemical vapour deposition of carbon nanotubes: In situ study of catalyst activation

We combine in situ X-ray photoelectron spectroscopy and ex situ electron and Raman spectroscopy to study chemical interactions of SiO 2-supported Fe catalyst films during C 2H 2 exposure in the 400–600 °C temperature range. Carbon nanotubes nucleate at C 2H 2 pressures below 10 −6 mbar, which allows a time-resolved recording of core level spectra. We find a rapid transition from an initial chemisorbed carbon on metallic Fe catalyst nanoparticles to a sp 2 graphitic carbon network. Pre-treating the Fe catalyst film by H 2 sputtering influences the initial catalyst de-wetting and increases carbon nanotube yield.

Oxidation of CO in H 2–CO mixtures catalyzed by platinum: alkali effects on rates and selectivity

Turnover rates and selectivities for CO oxidation in H 2–CO–O 2 reactant mixtures are much greater on Pt clusters supported on Cs-modified SiO 2 than on clusters of similar size dispersed on SiO 2 or Al 2O 3 supports. Selectivity effects reflect the inhibition of spillover-mediated H 2 oxidation pathways on support surfaces. Infrared spectra showed that Cs, Rb, or Na titrates support hydroxyl groups required for these unselective pathways. These H 2 oxidation pathways are unaffected by competitive CO co-adsorption and can lead to significant selectivity losses during preferential CO oxidation in H 2-rich streams. CO oxidation selectivities on Pt are above 90%, even at H 2/CO ratios of ∼100; much lower selectivities reported previously reflect contributions from spillover-mediated H 2 oxidation pathways on supports, which are not inhibited by CO co-reactants. Cs and Rb also increased turnover rates for monofunctional oxidation of CO on Pt cluster surfaces, apparently by disrupting the growth of chemisorbed CO monolayers, which prevent activation of O 2 co-reactants. The addition of 1.6 Cs/nm 2 to SiO 2 led to CO oxidation turnover rates more than 10 times higher than those on Pt/SiO 2 catalysts with similar Pt dispersion. CO monolayer growth processes are evident from a gradual decrease in CO oxidation rates during the initial stages of H 2–CO–O 2 reactions, which occurs simultaneously with an increase in intensity for chemisorbed CO infrared bands measured during reaction. This densification of chemisorbed CO monolayers is consistent with the recovery of initial rates by thermal treatment in inert streams and with the observed monotonic increase in CO oxidation selectivity as catalysts gradually approach steady-state CO coverages during reaction. Alkali appears to disrupt CO monolayer growth by promoting the formation of unreactive chemisorbed carbon via CO dissociation and disproportionation reactions, the rates of which increase when alkali is added to Pt surfaces. Chemisorbed carbon blocks some active Pt surface atoms, but also introduces obstacles that inhibit the formation of dense CO monolayers, thus retaining exposed Pt atoms required for the activation of O 2 co-reactants. Rb and Cs cations, which are more electropositive than Na cations, increase CO oxidation turnover rates more strongly, consistent with the proposed mechanisms for the electronic promotion effects of alkali on CO dissociation.

A model high surface area alumina-supported palladium catalyst

A catalyst preparative procedure is described that produces a high surface area alumina-supported palladium catalyst that yields an atypical chemisorbed carbon monoxide infrared spectrum. This inherently residue-free substrate provides a useful reference for evaluation of catalyst crystallite morphology and its effect on reactivity profiles.

The Infrared Spectra of Chemisorbed Carbon Monoxide as a Characterization Tool for Metal Heterogeneous Catalysts

AbstractFor Abstract see ChemInform Abstract in Full Text.

Kinetics of carbon deposition from ethylene on Pt(110) surface

The formation of carbonaceous deposits on Pt(110) surface due to ethylene decomposition in the temperature range of 770–970 K has been studied. Both kinetic and XPS data show that chemisorbed carbon (with no C−C bonds, but only C−Pt bonds) forms at T=770–870 K, the saturation coverage θs being about 1 ML. At higher temperatures, θs increases by a factor of 1.5, indicating the formation of more densely packed carbon species (DPC) due to C−C bonding. A kinetic model has been proposed to describe the process of carbon conversion.

Reactivity of oxygen states at caesium surfaces towards carbon monoxide and carbon dioxide

The development of oxygen states at caesium surfaces at 80 K has been studied by X-ray photoelectron spectroscopy. Core-level O 1s spectra have enabled three distinct oxygen states to be assigned to isolated oxygen adatoms, Oδ–, peroxo-type species, O2δ–, and oxide, O2–. The Oδ– state is only observed at low coverages and is the precursor to oxide formation. The reactivity of these species towards carbon monoxide and carbon dioxide has been studied through monitoring the O 1s and C 1s spectra and quantitative analysis of the stoichiometry of the reactions. Both the anionic form of chemisorbed carbon dioxide, CO2δ–, and surface carbonate species can be formed through reactions of the individual oxygen species with either CO or CO2 while the CO2δ– species can be transformed to carbonate species by exposure to dioxygen. All reactions are of low activation energy and occur at 80 K. A reaction scheme is proposed which illustrates the various reaction pathways available when carbon monoxide–dioxygen mixtures are exposed to a caesium surface at 80 K; for oxygen rich mixtures surface oxidation dominates while for carbon monoxide rich mixtures both chemisorbed carbon dioxide, CO2δ–, and surface carbonate form.

Chemisorption on surfaces — an historical look at a representative adsorbate: carbon monoxide

The study of the interaction of molecules with clean surfaces extends back to the work of Irving Langmuir. In this historical account, the development of selected experimental methods for the study of molecular adsorption will be discussed. This will be done by historically reviewing research on one of the most well-studied adsorbate molecules, carbon monoxide. Many of the modern surface science techniques have first been used to study chemisorbed carbon monoxide, and the CO molecule is employed even today as a test molecule for currently developing surface measurement instruments such as the low temperature STM. In addition to being a good test molecule for new surface measurement techniques, adsorbed carbon monoxide is one of the centrally important molecules in the field of heterogeneous catalysis where the production of synthetic fuels and useful organic molecules often depends on the catalytic behavior of the adsorbed CO molecule. Interestingly, the carbon monoxide molecule also serves as a bridge between surface chemistry on the transition metals and the field of organometallic chemistry. Concepts about the chemical bonding and the reactive behavior of CO chemisorbed on transition metal surfaces and CO bound in transition metal carbonyls link these two fields together in a significant manner. The carbon monoxide molecule has been the historical focal point of many endeavors in surface chemistry and surface physics, and research on adsorbed carbon monoxide well represents many of the key advances which characterize the first thirty years of the development of surface science.

Rate law and activation energy of isotope mixing between chemisorbed carbon monoxide molecules on a potassium-promoted nickel(111) surface

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTRate law and activation energy of isotope mixing between chemisorbed carbon monoxide molecules on a potassium-promoted nickel(111) surfaceKumar Sinniah, William D. Sands, John T. Yates Jr., and Kenneth C. JandaCite this: J. Am. Chem. Soc. 1991, 113, 10, 3684–3688Publication Date (Print):May 1, 1991Publication History Published online1 May 2002Published inissue 1 May 1991https://doi.org/10.1021/ja00010a008RIGHTS & PERMISSIONSArticle Views86Altmetric-Citations9LEARN 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 (658 KB) Get e-Alerts Get e-Alerts

Modified zinc silicate ? an active rubber filler

Physico-chemical properties have been characterized for zinc silicates obtained in various conditions in reaction of sodium metasilicate solution with water soluble zinc salt (zinc sulphate or chloride). Attempts have been made to apply the precipitated zinc silicates in rubber mixtures based on butadiene-styrene rubber. Appropriate tests have been conducted. Also, a possibility has been tested of eliminating zinc oxide (an activator in the vulcanization process) from the rubber mixture. Studies have been presented on the modification of zinc silicate surface with silane and titanate coupling agents. The extent of surface modification has been estimated measuring heats of surface immersion and determining chemisorbed carbon on the surface which has originated from coupling agents. The effect of modifying zinc silicate surface has been evaluated by strength tests performed on vulcanizates filled with the modified silicates.

Hydrogenation of surface carbon on alumina-supported nickel

Four types of carbon were observed to form on an alumina-supported nickel methanation catalyst on exposure to carbon monoxide at 550 ± 50 K. In order of their reactivity toward hydrogen the carbon species may be classified as: chemisorbed carbon atoms (α), bulk nickel carbide, amorphous carbon (β), and crystalline elemental carbon. The α-phase and the initial monolayers of Ni 3C are much more reactive than the elemental forms as measured by temperature-programmed surface reaction in 100 kPa H 2. At 550 K the α- and β-carbon species formed by CO exposure populate the surface at a ratio of about 2:1. Both phases are relatively stable on heating to 600 K in a He atmosphere. At higher temperatures, slow conversion of α- and β-carbon to graphite was observed. Hydrogenation of the α state at 550 K leads to methane at a sufficiently fast rate to make it a likely intermediate in nickel-catalyzed methane synthesis from hydrogen and carbon monoxide.

The infrared spectrum of carbon monoxide on reduced and oxidized palladium

The spectra of carbon monoxide adsorbed on a silica-supported, 9% palladium catalyst has been studied in conjunction with adsorption studies of carbon monoxide and oxygen. Both bridged and linear species are observed. These species both react readily at room temperature with gas phase oxygen, and a pre-adsorbed oxygen layer reacts rapidly with gaseous carbon monoxide to yield the same spectrum as that on the reduced catalyst. If the catalyst is subjected to bulk oxidation, however, the spectrum of adsorbed carbon monoxide changes dramatically; the linear form is greatly enhanced and the bridged species becomes greatly reduced. No bands ascribable to adsorbed carbon dioxide are observed. Evidence is presented that some of the several separate bands seen for bridged species stem from the same species interacting to differing degrees with neighboring chemisorbed carbon monoxide. Estimates based on adsorbed amounts suggest that the bridged species has an extinction coefficient an order of magnitude greater than that for the firmly bound linear species but that a loosely bound linear species has an extinction coefficient more comparable to that of the bridged species. A model is suggested for the mode of adsorption that assumes both linear and bridged carbon monoxide bound to the same metal atom.

Discussion of Blyholder, G.: Molecular Orbital View of Chemisorbed Carbon Monoxide

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTDiscussion of Blyholder, G.: Molecular Orbital View of Chemisorbed Carbon Monoxide F Matson, J Yates, and E HutchinsonCite this: J. Phys. Chem. 1964, 68, 10, 2777–2778Publication Date (Print):October 1, 1964Publication History Published online23 August 2006Published inissue 1 October 1964https://doi.org/10.1021/j100792a703RIGHTS & PERMISSIONSArticle Views211Altmetric-Citations7LEARN 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 (231 KB) Get e-Alerts

ON THE ANODIC OVERVOLTAGE IN ALUMINUM ELECTROLYSIS

The overvoltage on the carbon anode in aluminum electrolysis has been measured against a CO2/C reference electrode placed in the cryolite melt. The behavior of the reference electrode was first investigated against the aluminum cathode. This galvanic cell showed a stable potential of 1.15 V, which was close to the reversible potential for the cell reaction in aluminum electrolysis. Similar measurements were made with CO/C and CO2,CO/C electrodes. The potential of the CO/C electrode was in fair agreement with the reversible potential for the most probable cell reaction. The potentials obtained with CO2–CO mixtures were intermediate between those for the pure gases, increasing with increasing CO2 content. An explanation for the behavior of the CO2,CO/C electrode is suggested.The anodic overvoltage depended only to a limited extent on the chemical reactivity of carbon with respect to oxygen. Graphite anodes showed higher overvoltage than all other types of carbon anodes. Catalyzing and inhibiting additives to the carbon had small but significant influences on the overvoltage. Straight Tafel plots were obtained with slopes varying between 0.26 and 0.27. On this basis it is shown that the overvoltage may be due either to slow transport of oxygen ions through the double layer or to slow reaction between chemisorbed oxygen and carbon.

Influence of chemisorbed carbon monoxide on subsequent physical adsorption of nitrogen

1. The investigation of the effect of chemisorbed layer of carbon monoxide on subsequent adsorption of nitrogen at -191° on two samples of cobalt powder has shown that (a) the presence of a layer of chemisorbed carbon monoxide suppresses the nitrogen adsorption at -191°, (b) the suppression is constant irrespective of the volume of carbon monoxide on the surface, (c) the suppression effect disappears on heating the samples to 370° and above. 2. The suppression of nitrogen adsorption appears to be due to the presence of certain active centres on the surface of cobalt powder and which chemisorb carbon monoxide in such a manner that subsequent adsorption of nitrogen does not take place on such chemisorbed centres. 3. When suppression of nitrogen adsorption takes place in presence of chemisorbed carbon monoxide, the assumption of Emmett and Brunauer that the entire chemisorbed surface has the same adsorption characteristics as a bare non-metallic surface is invalid. 4. A method has been suggested for determination of carbon monoxide chemisorption in cases where suppression of nitrogen adsorption in presence of chemisorbed carbon monoxide is observed.

Oxygen Exchange in Chemisorbed Carbon Monoxide1

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTOxygen Exchange in Chemisorbed Carbon Monoxide1A. N. Webb and R. P. EischensCite this: J. Am. Chem. Soc. 1955, 77, 18, 4710–4713Publication Date (Print):September 1, 1955Publication History Published online1 May 2002Published inissue 1 September 1955https://doi.org/10.1021/ja01623a005RIGHTS & PERMISSIONSArticle Views44Altmetric-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 (527 KB) Get e-Alerts Get e-Alerts