Dissociative adsorption of carbon monoxide on Mo(110): first-principles theory

The adsorption and dissociation of carbon monoxide on Mo (110) surface is studied with density functional theory. The results at different sites (atop, short bridge, long bridge, and hollow) are presented. The hollow site is found to be the most stable adsorption site for CO. The CO molecule is found to adsorb in end-on configurations (alpha states) at high coverage and inclined configurations (beta states) at low coverage. The dissociation activation energy from beta states is found to be approximately 1 eV lower than from alpha state. The adsorption of dissociation products, C and O, on Mo(110) has also been studied. The most stable adsorption site for C and O is long bridge and hollow site, respectively. The adsorption of C and O at low coverage is, in general, stronger than at high coverage, which is partly responsible for the high reactivity of CO dissociation at low coverage, since the binding energy of CO is not very sensitive to the coverage.     

Stochastic bi-resonance in non-isothermal carbon monoxide catalytic oxidation system

The Pt(110)/CO O2 system subject to reaction heat, heat conduction and radiative heat transfer is non-isothermal and its temperature varies in time and space. In this paper, taking support temperature (ST) as the control parameter, the effect of the ST fluctuations in the oscillatory dynamics of the non-isothermal Pt(110)/CO O2 system is numerically studied. It is found that the ST fluctuations may induce stochastic oscillations and the oscillations exhibit stochastic bi-resonance (SBR) with the change of the strength or correlation time of the fluctuations. This result shows that the temperature fluctuations may enhance the chemical reaction oscillations. Moreover, the system can selectively and repeatedly employ the temperature fluctuations to enhance its reaction oscillations. It is also shown when the distance of the ST temperature to the oscillatory region increases a little, the effect of the temperature fluctuations would obviously weaken.     

Dynamic model of self-oscillatory evolution in carbon monoxide oxidation over Pt(110)

Based on the proposed reaction mechanism of catalytic CO oxidation on a Pt(110) surface, which has been well supported by experimental data, a kinetic model (six ODE's) was constructed accounting for the dynamics of adsorbates on the surface. This model completely reproduces the qualitative features of the reaction dynamics under fixed parameters (T, PCO, PO2), i.e. induction period before the beginning of self-oscillations and further time evolution of shape, period and amplitude of self-oscillations up to the achievement of a stable limit cycle (or steady state). In addition, the model predicts the possibility of bursting regimes (intermittence) of self-oscillations.     

Stochastic resonance in surface catalytic oxidation of carbon monoxide induced by colored noise

Noise is generally considered as a disadvanta-geous factor, which would smear weak signals, there-fore, people always try to reduce its influence. How-ever, recent studies show that, for a nonlinear system, under certain circumstances, noise can enhance sys-tem抯 response to a signal. At specific noise intensity, the response of a system to a weak signal may reach its maximum, which is called 搒tochastic resonance?(SR). The concept of SR was originally put forward by Benzi and his collaborat…     

First principles study of CO oxidation on TiO2(110): the role of surface oxygen vacancies

The reactivities of the stoichiometric and partially reduced rutile TiO2(110) surfaces towards oxygen adsorption and carbon monoxide oxidation have been studied by means of periodic density functional theory calculations within the Car-Parrinello approach. O2 adsorption as well as CO oxidation are found to take place only in the presence of surface oxygen vacancies (partially reduced surface). The oxidation of CO by molecularly adsorbed O2 at the O-vacancy site is found to have an activation energy of about 0.4 eV. When the adsorbed O2 is dissociated, the resulting adatoms can oxidize incoming gas-phase CO molecules with no barrier. In all studied cases, once CO is oxidized to form CO2, the resulting surface is defect-free and no catalytic cycle can be established.     

Evidence from first principles calculations for a bent CO2 intermediate in the oxidation of carbon monoxide on the Cu (110) surface

We have carried out first principles plane wave density-functional theory calculations to study the adsorption of CO molecule on a clean and unreconstructed Cu (110) surface at 1/12 monolayer coverage and have investigated the subsequent oxidation by preadsorbed oxygen atoms. As found experimentally, the CO adsorbs perpendicular to the surface plane through the carbon atom; the top site was found to be the most favorable position for CO adsorption although the short-bridge site is only slightly less stable. Surprisingly, for a sparely oxidized surface with O atoms adsorbed in hollow sites the coadsorption energy is slightly negative for only the above two CO sites which have therefore been used as starting points to explore the energy surface of the oxidation reaction. We have confirmed the existence of bent CO(2) surface intermediate as previously suggested from experimental studies. Using the nudged elastic band method, we have characterized a two step reaction which involves the formation of this intermediate. The results suggest that the rate determining step of the oxidation reaction is the formation of the intermediate and the energy barrier (200 meV) is close to although smaller than experimentally estimated values.     

Kinetic model of catalytic oxidation of carbon monoxide on nickel

A mechanism is proposed for describing the previous disclosed multiplicity of equilibrium states in the oxidation of carbon monoxide on metallic nickel. In contrast to the known mechanism for oxidation of CO oh platinum metals it includes a nonlinear stage of carbon monoxide adsorption and a linear stage of oxygen adsorption. A kinetic model has been obtained and stage velocity constants have been found, providing a basis for obtaining a quantitative agreement between the calculated and experimental relations between the reaction velocity and the reagent concentrations. Opinions are stated in relation to the causes for evolution of the CO oxidation reaction from platinum metals to nickel.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 22, No. 1, pp. 83–87, January–February, 1986.     

单晶Au表面和Au/TiO2（110）模型催化剂表面CO氧化反应机理和活性位

在分子尺度上介绍了Au/TiO2(110)模型催化剂表面和单晶Au表面CO氧化反应机理和活性位、以及H2O的作用.在低温(<320 K), H2O起着促进CO氧化的作用, CO氧化的活性位位于金纳米颗粒与TiO2载体界面(Auδ+–Oδ––Ti)的周边. O2和H2O在金纳米颗粒与TiO2载体界面边缘处反应形成OOH,而形成的OOH使O–O键活化,随后OOH与CO反应生成CO2.300 K时CO2的形成速率受限于O2压力与该反应机理相印证.相反,在高温(>320 K)下,因暴露于CO中而导致催化剂表面重组,在表面形成低配位金原子.低配位的金原子吸附O2,随后O2解离,并在金属金表面氧化CO.     

Adsorption of carbon monoxide and oxygen on Pt(110)

Adsorption of CO and O₂ on Pt(110) was studied by XPS, LEED and TDS methods to elucidate the role of O_ads states and structural rearrangements of the surface under the action of CO_ads in the appearance of self-oscillations in the rate of CO oxidation on Pt(110).

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, CO O₂ Pt(110) O CO CO Pt(110).

     

Adsorption of carbon monoxide on Pd low‐index surfaces and (110) reconstructed surface

Adsorption and diffusion of carbon monoxide on Pd low‐index surfaces and missing‐row Pd (110) reconstructed surface have been investigated by the extended London–Eyring–Polyani–Sato (LEPS) method constructed by means of a five‐parameter Morse potential. All critical characteristics, such as adsorption site, adsorption geometry, binding energy, CO vibrational frequency have been obtained and compared with the experimental and theoretical data. On these surfaces, the stable adsorption sites of CO are changed with increasing CO coverage. On the missing‐row Pd (110) reconstructed surface, there are five stable adsorption sites: H₁, H₂ (H₁ and H₂ are threefold hollow sites on (111) subsurface), B (bridge site on the second layer), SB (short‐bridge site), and T (top site). Copyright © 2010 John Wiley & Sons, Ltd.     

Density functional theory study of CO catalytic oxidation on Co_2B_2/TiO_2（110） surface

Titanium dioxide with CoB amorphous alloys nanoparticles deposited on the surface is known to exhibit higher catalytic activity than the CoB amorphous. A study of the structure of such system is necessary to understand this effect. A quantum chemical study of Co2B2 on the TiO2 (110) surface was studied using periodic slab model within the framework of density functional theory (DFT). The results of geometry optimization indicated that the most stable model of adsorption was Co2B2 cluster adsorbed on the hollow site of TiO2.The adsorption energy calculated for Co2B2 on the hollow site was 439.3 kJ/mol.The adsorption of CO and O2 was further studied and the results indicated that CO and O2 are preferred to adsorb on the Co2 site. Co-adsorption of CO and O2 shows that Co2B2/TiO2 is a good catalyst for the oxidation of CO to carbon dioxide in the presence of oxygen.     

Quantum chemical analysis of the Eley-Rideal and Langmuir-Hinshelwood mechanisms of the catalytic oxidation of carbon monoxide on the nickel surface

The studies concerned with the oxidation of carbon monoxide on the nickel surface are reviewed. The Eley-Rideal (ER) collision and Langmuir-Hinshelwood (LH) adsorption mechanisms of the oxidation are analyzed. Calculations of the activation barriers of the oxidation of carbon monoxide on the Ni (111), (100), and (110) faces were performed for the first time and involved optimization of the reaction paths by the collision and adsorption mechanisms. It is shown that on the Ni (111) and (110) faces the ER collision mechanism of the reaction is preferable with the activation barriers ΔE _dis ^O ₂=62 kJ/mole and ΔE _trans ^O A21F5001₂x=25 kJ/mole for Ni (111) and ΔE _dis ^O ₂=72 kJ/mole and ΔE _trans ^O ₂=20 kJ/mole for Ni (110); on the Ni (100) face, the LH adsorption mechanism with the activation barriers ΔE _dis ^O ₂=75 kJ/mole and ΔE _trans ^O ₂=42 kJ/mole is favored. Analysis of the potential barriers for the catalytic oxidation of carbon monoxide on the Ni surfaces suggests the LH mechanism to be preferential, although insignificant differences in the activation barries can lead to the oscillatory reaction mechanism, which is confirmed experimentally. The calculations were performed by the LCAO MO SCF method in the MINDO/3 approximation. Kiev Polytechnical Institute. Translated fromZhurnal Struktumoi Khimii, Vol. 37, No. 4, pp. 628–645, July–August, 1996. Translated by I. Izvekova     

Catalytic oxidation of carbon monoxide over Au/Fe2O3 preparations

Low temperature catalytic oxidation of carbon monoxide has been studied over Au/Fe₂O₃. On the coprecipitated samples the catalytic activity shows a maximum at a gold content of about 5%. Calcination of Au/Fe₂O₃ decreases the catalytic activity and the stability. The catalytic activity measured is the highest ever reported in the literature on Au/Fe₂O₃ preparations.     

Effect of platinum and palladium additives on the surface state and catalytic activity of vanadium oxides in the oxidation of carbon monoxide

The Pt/V₂O₅ and Pd/V₂O₅ systems formed upon hydrogen reduction have catalytic activity in the oxidation of carbon monoxide exceeding the activity of Pt/Al₂O₃ and Pd/Al₂O₃. The transition from the low-activity to high-activity state on the Pt/V₂O₅ and Pd/V₂O₅ catalysts is characterized by temperature hysteresis and change in the kinetic equation. X-ray phase analysis (XPA), X-ray photoelectron spectroscopy (XPES), and X-ray spectral microanalysis were used to establish that prior reduction of V₂O₅ by hydrogen gives VO₂, V₆O₁₃, a-H _x V₂O₅, and b-H _x V₂O₅, which facilitates the formation of an active catalyst surface.     

Agglomeration, sputtering, and carbon monoxide adsorption behavior for Au/Al(2)O(3) prepared by Au(n)(+) deposition on Al(2)O(3)/NiAl(110)

Size-selected gold clusters, Au(n)(+) (n = 1, 3, 4), were deposited on an ordered Al(2)O(3) film grown on NiAl(110), and changes in morphology and electronic properties with deposition/annealing temperature and cluster size were investigated by X-ray photoelectron spectroscopy (XPS) and ion-scattering spectroscopy (ISS). Extensive agglomeration was observed by ISS for annealing temperatures above 300 K, accompanied by large shifts in the Au XPS binding energy. Agglomeration is more extensive in room-temperature deposition, compared to samples prepared by low-temperature deposition, then annealed to room temperature. Agglomeration is also observed to be dependent on deposited cluster size. CO adsorption was studied by ISS and temperature-programmed desorption, and we looked for CO oxidation under conditions where substantial activity is seen for Au(n)/TiO(2). No activity was observed for Au(n)/Al(2)O(3). The differences between the two systems are interpreted in terms of the nature of the metal-support interactions.     

The interaction of hydrogen and carbon monoxide on Cu-Ni (110) single-crystal surfaces

The co-adsorption of H₂ and CO on a Cu-Ni (110) surface was studied by thermal desorption spectroscopy (TDS) and ultraviolet photoemission spectroscopy (UPS). Strong interactions between adsorbed CO and hydrogen observed in the CO desorption spectrum and CO valence emissions were attributed to a blockage of certain CO adsorption sites by hydrogen.     

In-situ scanning tunneling microscopy of carbon monoxide adsorbed on Au(111) electrode

In-situ scanning tunneling microscopy (STM) coupled with cyclic voltammetry was used to examine the adsorption of carbon monoxide (CO) molecules on an ordered Au(111) electrode in 0.1 M HClO4. Molecular resolution STM revealed the formation of several commensurate CO adlattices, but the (9 x radical 3) structure eventually prevailed with time. The CO adlayer was completely electrooxidized to CO2 at 0.9 V versus RHE in CO-free 0.1 M HClO(4), as indicated by a broad and irreversible anodic peak which appeared at this potential in a positive potential sweep from 0.05 to 1.6 V. A maximal coverage of 0.3 was estimated for CO admolecules from the amount of charge involved in this feature. Real-time in-situ STM imaging allowed direct visualization of the adsorption process of CO on Au(111) at 0.1 V, showing the lifting of (radical 3 x 22) reconstruction of Au(111) and the formation of ordered CO adlattices. The (9 x radical 3) structure observed in CO-saturated perchloric acid has a coverage of 0.28, which is approximately equal to that determined from coulometry. Switching the potential from 0.1 to -0.1 V restored the reconstructed Au(111) with no change in the (9 x radical 3)-CO adlattice. However, the reconstructed Au(111) featured a pairwise corrugation pattern with two nearest pairs separated by 74 +/- 1 A, corresponding to a 14% increase from the ideal value of 65.6 A known for the ( radical 3 x 22) reconstruction. Molecular resolution STM further revealed that protrusions resulting from CO admolecules in the (9 x radical 3) structure exhibited distinctly different corrugation heights, suggesting that the CO molecules resided at different sites on Au(111). This ordered structure predominated in the potential range between 0.1 and 0.7 V; however, it was converted into new structures of (7 x radical 7) and ( radical 43 x 2 radical 13) on the unreconstructed Au(111) when the potential was held at 0.8 V for ca. 60 min. The coverage of CO adlayer decreased accordingly from 0.28 to 0.13 before it was completely removed from the Au(111) surface at more positive potentials.