Kinetic oscillations in the NO + CO reaction on Pt(100): Experiments and mathematical modeling

Fink, Th.; Dath, Jean‐Pierre; Imbihl, R.; Ertl, G.

doi:10.1063/1.461010

Cited by 159 publications

(132 citation statements)

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“…Subsequently, this reaction became subject of extended investigations with Pt(100) in the 10 -7 to 10 -5 mbar pressure regime [142][143][144][145][146][147][148]. No oscillations were observed on Pt (111) and Pt (110), which planes were found to be much less reactive in dissociating NO, in accordance with findings made with the cylindrical Pt single crystal sample [146].…”

Section: Other Isothermal Systems With Oscillatory Kineticssupporting

confidence: 64%

“…In the low temperature (≤ 430 K) range the oscillations occur on a pure 1 × 1 substrate. They are not sustained but may be initiated by a small temperature jump after which they decay within a few cycles [144]. This effect is due to insufficient lateral coupling as was verified by imaging spatio-temporal concentration patterns by PEEM [148].…”

Section: Other Isothermal Systems With Oscillatory Kineticsmentioning

confidence: 98%

“…At the upper limit, oscillations develop via a Feigenbaum scenario from small amplitude chaotic oscillations, while at the lower limit the transition to stationary kinetics is discontinuous and associated with the onset of spatio-temporal pattern formation [147,148]. The mechanism of the NO + CO reaction (with formation of N 2 O in a side reaction being neglected) involves dissociation of adsorbed NO as rate-limiting step [144]. This process, NO ad + * → N ad + O ad , requires (formally) an additional vacant adsorption site (*).…”

Section: Other Isothermal Systems With Oscillatory Kineticsmentioning

confidence: 99%

“…A qualitative theoretical description could be achieved by including this step in the model [144], which was recently extended further by incorporating more accurately the growth kinetics of the 1 × 1 phase triggered by lifting the hex reconstruction [152]. Even then, however, the agreement between theory and experiment is not completely satisfactory, most probably due to the presence of surface defects which play a significant role in the dissociation of NO [144] and may be modified by the reaction [153]. 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.…”

Section: Other Isothermal Systems With Oscillatory Kineticsmentioning

confidence: 99%

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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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Section: Other Isothermal Systems With Oscillatory Kineticssupporting

confidence: 64%

Section: Other Isothermal Systems With Oscillatory Kineticsmentioning

confidence: 98%

Section: Other Isothermal Systems With Oscillatory Kineticsmentioning

confidence: 99%

Section: Other Isothermal Systems With Oscillatory Kineticsmentioning

confidence: 99%

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

Ertl

2008

Handbook of Heterogeneous Catalysis

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“…El cambio periódico que experimenta la estructura del catalizador causa oscilaciones en la reacción de reducción de NO, por diferentes agentes como CO, H 2 y NH 3 , por ejemplo, en el monocristal de Pt(100), el estado estable cuasi-hexagonal (hex) puede ser reestructurado hacia un estado metaestable 1 1 por efectos de adsorción de las moléculas, y puede reconstruir de manera inversa 1 1 → hex por la desorción de los productos (Imbihl y Ertl, 1995;Lombardo et al, 1993;Fink et al, 1991b). 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).…”

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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