The NO + H2 reaction on Pt(100): steady state and oscillatory kinetics

Slinko, M. M.; Fink, Th.; Löher, T.; Madden, H. H.; Lombardo, Stephen J.; Imbihl, R.; Ertl, G.

doi:10.1016/0039-6028(92)90174-5

Cited by 94 publications

(53 citation statements)

References 33 publications

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“…Ammonia undergoes one dehydrogenation step on the Pt . Even considering only the slower reacting isomer, Pt 5 À constitutes the most reactive bare cluster in the present study.…”

Section: Resultsmentioning

confidence: 98%

“…[38] For Pt 4 À , two consecutive dehydrogenations are observed: in the first step, a low rate constant of 1.9 10 À12 cm 3 molecule À1 s À1 is again observed, while the . Figure 1 depicts the measured ion intensities as a function of time for Pt 5 À , together with a kinetic fit. Pt 5 À is the only ion in the present study for which the reactant intensity in the semi-logarithmic plot is curved; this effect indicates the presence of several reactive platinum isomers or groups with distinctly different kinetic or internal energy content.…”

Section: Resultsmentioning

confidence: 99%

“…[3] Elementary steps of all these processes have been extensively studied on bulk surfaces as well as under ultra-high vacuum conditions. [4][5][6] Ionic platinum clusters and even monoatomic platinum ions in the gas phase have been widely used as model systems for heterogeneous catalysis, exploring elementary steps like C À H bond activation, oxidation reactions or hydrogen adsorption. [7][8][9][10][11][12][13][14][15][16][17][18][19][20] Even complete catalytic cycles have been demonstrated, like the oxidation of H 2 by O 2 to H 2 O, [21] or of CO by N 2 O to CO 2 .…”

Section: Introductionmentioning

confidence: 99%

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Thermal NH Bond Activation on Anionic and Cationic Platinum Clusters: Non‐Predetermined Reaction Pathways Indicate Transitions to a Bulk Surface Reactivity

Ončák

Cao

Höckendorf

et al. 2009

Chemistry A European J

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Reactions of cationic and anionic platinum clusters Pt(n)(+/-), n=1-5, with NH(3) are studied by FT-ICR mass spectrometry and DFT calculations. With cationic clusters, radiative association of an intact NH(3) is the dominant reaction channel. On anionic clusters, NH(3) undergoes reductive elimination of molecular hydrogen, with nitride and hydride bound at remote sites of the cluster. Nitride assumes a bridge position, while hydride is bound atop a single platinum atom. On the [Pt(n),NH(3)](-) potential energy surface, for n=4 fifteen local minima and connecting transition states were identified with relevance to the hydrogen formation reaction, and 12 local minima were identified for n=5. These potential energy surfaces offer a rich variety of pathways, illustrating a key feature of a successful bulk catalyst: The variety of pathways helps the catalyst to work over a wide range of temperatures and pressures.

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“…Ammonia undergoes one dehydrogenation step on the Pt . Even considering only the slower reacting isomer, Pt 5 À constitutes the most reactive bare cluster in the present study.…”

Section: Resultsmentioning

confidence: 98%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Thermal NH Bond Activation on Anionic and Cationic Platinum Clusters: Non‐Predetermined Reaction Pathways Indicate Transitions to a Bulk Surface Reactivity

Ončák

Cao

Höckendorf

et al. 2009

Chemistry A European J

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“…Otro mecanismo que promueve la formación de oscilaciones, en esta reacción, se debe a la gran interacción que existe entre las especies adsorbidas (Slinko et al, 1992). En particular, para la reacción NO+CO en Pt(100), a condiciones de T > 430 K estos son los mecanismos aceptados y se han realizado diferentes estudios de Monte Carlo (MC) para explicar la aparición de los diferentes fenómenos no lineales (Zhdanov, 2002;Perera y Vicente, 2002).…”

Section: Introduccionunclassified

Estudio del Fenómeno Explosión de Superficie en la Reacción NO+CO en Pt(100) por Simulación de Monte Carlo Dinámico

Alas

Vicente

2009

Inf. tecnol.

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ResumenSe presenta el estudio de la reducción catalítica de NO por CO en una superficie de Pt(100) por medio de una simulación de Monte Carlo dinámico. El objetivo es analizar la evolución temporal y espacio-temporal del sistema. Considerando un mecanismo de reacción tipo Langmuir-Hinshelwood, se construye un modelo donde se involucran todos los pasos elementales de la reacción y se simula la llamada explosión de superficie. El análisis también considera recientes evidencias experimentales concernientes a la formación y decaimiento de una especie intermediaria (N-NO)* como el paso de reacción principal en la producción de N 2 . Los resultados de la simulación están de acuerdo con resultados experimentales de espectroscopia de desorción de masas. Además, la simulación permite correlacionar los máximos de producción de N 2 y CO 2 con la formación de patrones espaciales tipo célula sobre la superficie. Palabras clave: Monte Carlo dinámico, reducción de NO, explosión de superficie, patrones celulares Study of the Surface Explosion Phenomenon in the NO+CO Reaction on Pt(100) by Dynamic Monte Carlo Simulation AbstractIn this work the catalytic reduction of NO by CO on a Pt(100) surface by dynamic Monte Carlo simulation is presented. The objective is to analyze the temporal and spatial-temporal behavior. A Langmuir-Hinshelwood mechanism and a model where all the reaction steps are taken into account are considered and the so-called surface explosion is simulated. The analysis also includes recent experimental evidences concerning the formation and decay of a (N-NO)* intermediary species which turns out to be important for the N 2 formation. These simulation results show good quantitative agreement with experimental results obtained from isothermal mass spectroscopy desorption. Furthermore, the simulations allow correlating the maximum production of N 2 with the formation of cellular patterns on the surface.

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“…Reduction of NO by either H 2 or NH 3 does not proceed along single pathways but through branching channels whereby the aspect of selectivity also comes into play. In the NO + H 2 reaction on Pt(100) both N 2 and NH 3 are formed (apart from a minor yield of N 2 O) [155,156] whereby chaotic kinetics were also identified [157].…”

Section: Other Isothermal Systems With Oscillatory Kineticsmentioning

confidence: 99%

Non‐Linear Dynamics: Oscillatory Kinetics and Spatio‐Temporal Pattern Formation

Ertl

2008

Handbook of Heterogeneous Catalysis

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The rate of a catalytic reaction is governed by the underlying mechanism, i.e. the sequence of elementary reaction steps, and depends on the external control parameters such as the concentrations (= partial pressures) p j of educt and product species and temperature T, if transport processes are excluded in this context. More specifically, usually the adsorbed species are assumed to be randomly distributed over the surface, and their concentrations (= coverages) θ i are described within a mean-field approximation so that the reaction rate (= number of molecules r formed per unit time, dn r /dt t ) is given by dn r dt = f θ i , T ( ) (1) whereby the coverages θ i are in turn determined by a set of differential equations (modeling the individual steps of adsorption, desorption and surface reaction) of the typeProper treatment then requires that additional constraints given by heat and mass balance are taken into consideration.Under flow conditions with the external control parameters being kept fixed, usually the reaction proceeds at steady state with constant rate, i.e., dn r /dt = constant and dθ i /dt = 0. Due to the nonlinear character of the quoted differential equations, this has, however, not necessarily to be the case; the kinetics may -for certain ranges of parameters -become oscillatory or even irregular (chaotic). Such systems are typically far away from equilibrium, and (i) By far the most detailed insights into the underlying mechanisms and the general phenomenology of spatio-temporal self-organization were obtained in studies with well-defined single crystal surfaces by applying the arsenal of modern surface physical methods.(ii) Single crystal studies are usually conducted with bulk samples under low pressure conditions (≤ 10 -4 mbar)where the temperature changes associated with varying reaction rate are negligible. In addition, the mean-free path of gaseous molecules is comparable or even larger than the dimensions of the reaction vessel, which is operated as a continuous flow reactor. Hence, concentration gradients in the gas phase are practically instantaneously (≤ 10 -3 s)transmitted. Analysis of such experiments is thus appreciably simplified.(iii) Experiments with polycrystalline, i.e. "real", catalysts are usually conducted at elevated partial pressures (≥ 1 mbar) under which the heat released by the reaction may lead to noticeable temperature variations. The resulting thermokinetic effects may become dominating, so that even the nonuniformity of the surface chemistry is masked and quite novel phenomena may arise. Ideally, the reaction is conducted in a way, which may be described by a continuously stirred tank reactor (CSTR), i.e., perfect mixing ensures that the concentrations are everywhere identical.However, frequently a concentration profile exists along the reactor, which is hence rather of the plug-flow type. It is thus evident that heat and mass transfer limitations may play important roles with such systems.Generally, an extended system such as a single crystal surface, or even more ...

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The NO + H2 reaction on Pt(100): steady state and oscillatory kinetics

Cited by 94 publications

References 33 publications

Thermal NH Bond Activation on Anionic and Cationic Platinum Clusters: Non‐Predetermined Reaction Pathways Indicate Transitions to a Bulk Surface Reactivity

Thermal NH Bond Activation on Anionic and Cationic Platinum Clusters: Non‐Predetermined Reaction Pathways Indicate Transitions to a Bulk Surface Reactivity

Estudio del Fenómeno Explosión de Superficie en la Reacción NO+CO en Pt(100) por Simulación de Monte Carlo Dinámico

Non‐Linear Dynamics: Oscillatory Kinetics and Spatio‐Temporal Pattern Formation

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