Adsorption of oxygen and carbon monoxide on DymCun bimetallic surfaces at room temperature

1987 ◽  
Vol 52 (10) ◽  
pp. 2392-2400
Author(s):  
Josef Kopešťanský
Keyword(s):  
Carbon Monoxide ◽  
Surface Layer ◽  
Room Temperature ◽  
Dipole Moments ◽  
Dissociative Adsorption ◽  
Copper Surfaces ◽  
Cu Content ◽  
Bimetallic Surfaces ◽  
Adsorbed Co ◽  
Alloy Segregation

The adsorption of oxygen and carbon monoxide on surfaces of dysprosium, copper, and their bimetallic “alloys” DymCun was studied by work function measurements. In the starting stage of adsorption of oxygen, copper surfaces are more reactive than dysprosium surfaces, and bulk oxide appears in the sub-surface copper layers at room temperature; this was also observed for the bimetallic surfaces, where the starting adsorption of oxygen took place nearly exclusively on copper. With dysprosium, the bulk oxide did not form at room temperature; instead, oxygen was adsorbed on the surface to form a layer consisting of species of two kinds with substantially different dipole moments. Carbon monoxide practically did not adsorb on copper at 25 °C, whereas on dysprosium it exhibited dissociative adsorption. On the bimetallic surfaces (DyCu and DyCu6) the amount of adsorbed CO decreased proportionally to the increasing Cu content of the alloy. Segregation of copper in the surface layer, observed for the bimetallic DymCun “alloys”, resulted in an additional decrease in the amount of adsorbed CO.

Surface potential of mixed adsorbates on metal films

1962 ◽  
Vol 268 (1335) ◽  
pp. 452-473 ◽  
Keyword(s):  
Carbon Monoxide ◽  
Surface Potential ◽  
Room Temperature ◽  
Dipole Moments ◽  
Preliminary Investigation ◽  
Spectroscopic Method ◽  
Adsorbed Layer ◽  
Potential Method ◽  
Potential Change ◽  
The Individual

The surface potential changes effected at the surface of sintered evaporated films of two metals, copper and nickel, by the chemisorption of pairs of gases at —183 °C have been measured. The sign and magnitude of the dipole moment of the chemisorbed bond (which is directly related to the surface potential change) are specific to the chemisorbed species and the induced polarization effects of neighbouring dipoles are small. Consequently, an approximate additivity rule has been used by which the surface potential change of an adsorbed layer comprising two different adsorbates can be calculated from the relative amounts and the individual dipole moments of each adsorbate. Significant departures from this rule indicate the occurrence of a surface reaction with the formation of a new surface complex, the nature of which depends on the order of addition of the individual gases at — 183 °C. By measuring the amount of, and analyzing the nature of, the products desorbed on raising the adsorbent to room temperature, followed by a measurement of the amount of one of the adsorbates re-adsorbed at — 183 °C, and simultaneously recording the surface potential changes, information about the structure of the first-formed complex, together with some details of its possible mode of decomposition, is obtained. The present method of detecting intermediaries at the adsorbent surface during the process of a simple heterogeneously-catalyzed process is complementary to the infra-red spectroscopic method originated by Eischens and his co-workers. The present paper represents a preliminary investigation of the potential value of the surface potential method and has been applied to the reactions of (i) carbon monoxide and hydrogen, (ii) carbon monoxide and oxygen, and (iii) hydrogen and oxygen. The results are limited to processes occurring at room temperature and to two metal adsorbents, copper and nickel, chosen because the former has a full d -band whereas the latter has available empty d -orbitals. Marked differences are found with reaction (i), but these are less marked, particularly when oxygen is chemisorbed first, in reactions (ii) and (iii). The limitations of the general approach are discussed and the disadvantages of the use of the space-charge limited-diode technique are noted.

Infrared evidence of room temperature dissociative adsorption of carbon monoxide over Ag/Al2O3

2012 ◽  
Vol 197 (1) ◽  
pp. 155-161 ◽  
Author(s):  
Kévin Bechoux ◽  
Olivier Marie ◽  
Marco Daturi ◽  
Gérard Delahay ◽  
Carolina Petitto ◽  
...  
Keyword(s):  
Carbon Monoxide ◽  
Room Temperature ◽  
Dissociative Adsorption

Conformation and electronic structure of aromatic chloroformates

1987 ◽  
Vol 52 (4) ◽  
pp. 970-979 ◽  
Author(s):  
Otto Exner ◽  
Pavel Fiedler
Keyword(s):  
Electronic Structure ◽  
Oxygen Atom ◽  
Strong Interaction ◽  
Electron Distribution ◽  
Room Temperature ◽  
Functional Group ◽  
Dipole Moments ◽  
Carbonyl Oxygen ◽  
Nonpolar Solvents ◽  
Single Method

Aromatic chloroformates Ib-Ie were shown to exist in the ap conformation, in agreement with aliphatic chloroformates, i.e. the alkyl group is situated cis to the carbonyl oxygen atom as it is the case in all esters. While 4-nitrophenyl chloroformate (Ie) is in this conformation in crystal, in solution at most several tenths of percent of the sp conformation may be populated at room temperature and in nonpolar solvents only. A new analysis of dipole moments explained the previous puzzling results and demonstrated the impossibility to determine the conformation by this single method, in consequence of the strong interaction of adjoining bonds. If, however, the ap conformation is once proven, the dipole moments reveal some features of the electron distribution on the functional group, characterized by the enhanced polarity of the C-Cl bond and reduced polarity of the C=O bond. This is in agreement with the observed bond lengths and angles.

Adsorption of Carbon Monoxide on Pd/SiO2/Si(111) Studied by Core-Level Photoemission

1998 ◽  
Vol 63 (11) ◽  
pp. 1793-1802 ◽  
Author(s):  
Zdeněk Bastl ◽  
Tomáš Šarapatka
Keyword(s):  
Carbon Monoxide ◽  
Photoelectron Spectroscopy ◽  
Co Adsorption ◽  
Charge Balance ◽  
Adsorption Activity ◽  
Chemical States ◽  
Adsorbed Co ◽  
Pd Clusters ◽  
Almost All ◽  
P Type

X-Ray photoelectron spectroscopy (XPS) has been used to study the adsorption of carbon monoxide on Pd dispersed on oxidized Si(111) surface. A fraction of the deposited Pd diffusing at room temperature to the SiO2/Si interface increases with decreasing SiO2 thickness. For oxide layers thinner than ≈1 nm, almost all deposited Pd diffuses to SiO2/Si interface forming there Si silicide. Consequently, the amount of adsorbed CO is dependent on the thickness of the thermally grown SiO2 layer. Two different chemical states of adsorbed carbon atoms, the population of which depends on the amount of the Pd deposited, are observed in the C (1s) spectra of adsorbed CO. Adsorption activity of Pd clusters does not depend on whether n- or p-type Si is used. Comparison of the experimental Pd/CO concentration ratios with those calculated assuming several different modes of the Pd growth on SiO2/Si points to the pseudo-Stranski-Krastanow mode (flat clusters with incomplete condensation of the first layer) at 300 K. Changes in charge balance across the Pd/SiO2/Si interface caused by CO adsorption are discussed in terms of the surface photovoltage effect and work function variation.

scholarly journals CO Oxidation Efficiency and Hysteresis Behavior over Mesoporous Pd/SiO2 Catalyst

Catalysts ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 131 ◽  
Author(s):  
Rola Mohammad Al Soubaihi ◽  
Khaled Mohammad Saoud ◽  
Myo Tay Zar Myint ◽  
Mats A. Göthelid ◽  
Joydeep Dutta
Keyword(s):  
Carbon Monoxide ◽  
Catalytic Activity ◽  
Co Oxidation ◽  
Active Sites ◽  
Bond Activation ◽  
Dissociative Adsorption ◽  
High Catalytic Activity ◽  
Good Catalytic Activity ◽  
Pretreatment Conditions ◽  
Oxidation Efficiency

Carbon monoxide (CO) oxidation is considered an important reaction in heterogeneous industrial catalysis and has been extensively studied. Pd supported on SiO2 aerogel catalysts exhibit good catalytic activity toward this reaction owing to their CO bond activation capability and thermal stability. Pd/SiO2 catalysts were investigated using carbon monoxide (CO) oxidation as a model reaction. The catalyst becomes active, and the conversion increases after the temperature reaches the ignition temperature (Tig). A normal hysteresis in carbon monoxide (CO) oxidation has been observed, where the catalysts continue to exhibit high catalytic activity (CO conversion remains at 100%) during the extinction even at temperatures lower than Tig. The catalyst was characterized using BET, TEM, XPS, TGA-DSC, and FTIR. In this work, the influence of pretreatment conditions and stability of the active sites on the catalytic activity and hysteresis is presented. The CO oxidation on the Pd/SiO2 catalyst has been attributed to the dissociative adsorption of molecular oxygen and the activation of the C-O bond, followed by diffusion of adsorbates at Tig to form CO2. Whereas, the hysteresis has been explained by the enhanced stability of the active site caused by thermal effects, pretreatment conditions, Pd-SiO2 support interaction, and PdO formation and decomposition.

Carbon monoxide formation as an intermediate product in photocatalytic steam reforming of methane with lanthanum-doped sodium tantalate

2021 ◽  
Author(s):  
Wirya Sarwana ◽  
Akihiko Anzai ◽  
Daichi Takami ◽  
Akira Yamamoto ◽  
Hisao Yoshida
Keyword(s):  
Carbon Monoxide ◽  
Solar Energy ◽  
Steam Reforming ◽  
Intermediate Product ◽  
Room Temperature ◽  
Carbon Monoxide Formation ◽  
Steam Reforming Of Methane

Photocatalytic steam reforming of methane (PSRM) has been studied as an attractive method to produce hydrogen by utilizing photoenergy like solar energy around room temperature with metal-loaded photocatalysts, where methane...

scholarly journals Room-temperature carbon monoxide oxidation by oxygen over Pt/Al2O3 mediated by reactive platinum carbonates

2015 ◽  
Vol 6 (1) ◽  
Author(s):  
Mark A. Newton ◽  
Davide Ferri ◽  
Grigory Smolentsev ◽  
Valentina Marchionni ◽  
Maarten Nachtegaal
Keyword(s):  
Carbon Monoxide ◽  
Room Temperature ◽  
Carbon Monoxide Oxidation
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