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Journal ArticleDOI

Steady and nonsteady rates of reaction in a heterogeneously catalyzed reaction: Oxidation of CO on platinum, experiments and simulations

15 Oct 1989-Journal of Chemical Physics (American Institute of Physics)-Vol. 91, Iss: 8, pp 4949-4960
TL;DR: In this paper, the rate of reaction for oxidation of CO over (210 and (111) singlecrystal surfaces of platinum has been studied as a function of reactant pressures (PO2,PCO) and sample temperature (T), both experimentally and by computer simulation.
Abstract: The rate of reaction for oxidation of CO over (210) and (111) single‐crystal surfaces of platinum has been studied as a function of reactant pressures (PO2,PCO) and sample temperature (T), both experimentally and by computer simulation Experimental results on both surfaces show regions with a steady high rate of reaction followed by a nonsteady transition region and, at high CO pressures, a region with low reactivity caused by CO poisoning of the surface At constant sample temperature, the transition region can be narrow and depends critically on the ratio of the gas phase concentration of reactants (PCO/PO2) The temperature dependences of the experimental data indicate that the critical ratio and the details for the occurrence of CO poisoning are strongly affected by surface processes such as adsorption, desorption, and diffusion ordering and reconstruction phenomena A computer simulation model of the Langmuir–Hinshelwood surface reaction as developed by Ziff et al was used for the simulation of the reaction under flow conditions The initial fair agreement between this model and the experiment can be significantly improved if processes such as adsorption, desorption, and diffusion are taken into account in an extended simulation model which in turn provides an insight into the kinetics of adsorbate poisoning and the effect of adsorbate‐induced processes on the reaction
Citations
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Journal ArticleDOI
TL;DR: In this article, a review of recent developments in non-equilibrium statistical physics is presented, focusing on phase transitions from fluctuating phases into absorbing states, the universality class of directed percolation is investigated in detail.
Abstract: This review addresses recent developments in non-equilibrium statistical physics. Focusing on phase transitions from fluctuating phases into absorbing states, the universality class of directed percolation is investigated in detail. The survey gives a general introduction to various lattice models of directed percolation and studies their scaling properties, field-theoretic aspects, numerical techniques, as well as possible experimental realizations. In addition, several examples of absorbing-state transitions which do not belong to the directed percolation universality class will be discussed. As a closely related technique, we investigate the concept of damage spreading. It is shown that this technique is ambiguous to some extent, making it impossible to define chaotic and regular phases in stochastic non-equilibrium systems. Finally, we discuss various classes of depinning transitions in models for interface growth which are related to phase transitions into absorbing states.

1,475 citations

Journal ArticleDOI
TL;DR: In this article, a review of recent developments in nonequilibrium statistical physics is presented, focusing on phase transitions from fluctuating phases into absorbing states, and several examples of absorbing-state transitions which do not belong to the directed percolation universality class are discussed.
Abstract: This review addresses recent developments in nonequilibrium statistical physics. Focusing on phase transitions from fluctuating phases into absorbing states, the universality class of directed percolation is investigated in detail. The survey gives a general introduction to various lattice models of directed percolation and studies their scaling properties, field-theoretic aspects, numerical techniques, as well as possible experimental realizations. In addition, several examples of absorbing-state transitions which do not belong to the directed percolation universality class will be discussed. As a closely related technique, we investigate the concept of damage spreading. It is shown that this technique is ambiguous to some extent, making it impossible to define chaotic and regular phases in stochastic nonequilibrium systems. Finally, we discuss various classes of depinning transitions in models for interface growth which are related to phase transitions into absorbing states.

1,081 citations

Journal ArticleDOI
TL;DR: In this paper, a two-variable model for catalytic CO oxidation on a Pt(110) surface has been proposed, with the faceting of the surface as a fourth variable.
Abstract: The parameters entering the kinetics for the mechanism of catalytic CO oxidation have been adapted for a Pt(110) surface, giving rise to a two‐variable model correctly predicting bistability. Oscillations are obtained when, in addition, the adsorbate‐driven 1×2–1×1 structural phase transition of Pt(110) is taken into account. Mixed‐mode oscillations can be qualitatively explained by including the faceting of the surface as a fourth variable. The limitations of the model essentially stem from the fact that only ordinary differential equations have been analyzed so far neglecting spatial pattern formation. It is discussed which dynamic phenomena observed experimentally in the CO oxidation on Pt(110) will probably not be adequately describable without taking spatial effects into account.

247 citations

Journal ArticleDOI
TL;DR: In this paper, the authors present a detailed catalogue of the experimental data obtained in this field of surface science and show that the coverage dependence of the apparent Arrhenius parameters is, as a rule, rather strong.

210 citations

Journal ArticleDOI
TL;DR: In this article, a review of the first-order kinetic phase transition with bistability and chemical waves is presented, where the authors mainly focus on the first order kinetic phase transitions connected with bistsability and resulting in chemical waves.

190 citations

References
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Book
01 Jan 1982
TL;DR: In early spring 1996, this article published a complete handbook on science and technology of catalysis, which is available as a set for a reduced price for all scientists working in the fields of kinetics and homogenous or heterogenous catalysis.
Abstract: In early spring 1996 our handbook on science and technology of catalysis will be completed In order to give all scientists working in the fields of kinetics and homogenous or heterogenous catalysis the possibility to have this detailed treatise of the topic on his or her shelf we decided to offer the whole handbook as a set for a reduced price

1,689 citations

Journal ArticleDOI
TL;DR: In this paper, an irreversible kinetic surface-reaction model based on the reaction of carbon monoxide and oxygen on a catalyst surface was presented, and it was found by computer simulation that the adsorbed molecules on the surface undergo both first-and second-order kinetic phase transitions.
Abstract: An irreversible kinetic surface-reaction model, based upon the reaction of carbon monoxide and oxygen on a catalyst surface, is presented. It is found by computer simulation that the adsorbed molecules on the surface undergo both first- and second-order kinetic phase transitions. These transitions correspond to the "poisoning" phenomenon seen on catalysts. Interesting transient and periodic behavior is also seen.

784 citations

Journal ArticleDOI
TL;DR: The work function at first decreases, exhibits a (temperature-dependent) minimum at θ = 13, attains nearly the value of the clean surface at 12 and again exhibits a second (shallow) minimum around 0.68 as mentioned in this paper.

721 citations

Journal ArticleDOI
TL;DR: In this paper, a detailed investigation of the steady-state and nonsteady-state reaction CO+1/2O2→CO2 on Pd (111) has been carried out with the molecular beam technique.
Abstract: A detailed investigation of the steady‐state and nonsteady‐state reaction CO+1/2O2→CO2 on Pd (111) has been carried out with the molecular beam technique. It could be shown conclusively that the reaction proceeds between two adsorbed species (Langmuir–Hinshelwood mechanism) throughout the temperature and pressure range investigated. For low CO coverages, the activation energy of the reaction was determined to be 25 kcal/mole, whereas at moderate CO coverages, a rearrangement of the oxygen adlayer takes place resulting in a reduction of the activation energy to 14 kcal/mole. It is not possible to formulate a simple kinetic expression for the reaction rate which is valid over the entire range of temperatures and pressures due to changes in the adsorption rate for O2, coadsorption of CO and O2, to diffusion in the adlayer, and to changes in the geometrical arrangement within the adlayer with varying coverage.

527 citations

Journal ArticleDOI
TL;DR: In this paper, the authors studied the reaction of carbon monoxide catalyzed by Pt(111) using reactive molecular beam-surface scattering and showed that at low coverage, the reaction proceeds with an activation energy E*LH =24.1 kcal/mole and a pre-exponential υ4 =0.11 cm2 particles−1
Abstract: The oxidation of carbon monoxide catalyzed by Pt(111) was studied in ultrahigh vacuum using reactive molecular beam–surface scattering. Under all conditions studied, the reaction follows a Langmuir–Hinshelwood mechanism: the combination of a chemisorbed CO molecule and an oxygen adatom. When both reactants are at low coverage, the reaction proceeds with an activation energy E*LH =24.1 kcal/mole and a pre‐exponential υ4 =0.11 cm2 particles−1 sec−1. At very high oxygen coverage, E*LH decreases to about 11.7 kcal/mole and υ4 to about 2×10−6 cm2 particles−1 sec−1. This is largely attributed to the corresponding increase in the energy of the adsorbed reactants. When a CO molecule incident from the gas phase strikes the surface presaturated with oxygen, it enters a weakly held precursor state to chemisorption. Desorption from this state causes a decrease in chemisorption probability with temperature. Once chemisorbed, the CO molecule then has almost unit probability of reacting to produce CO2 below 540 K. The CO2 product angular distribution varies from cosγ to cos4γ depending sensitively upon the adsorbed reactant concentrations.

522 citations