The oscillatory behavior of the CO oxidation reaction at atmospheric pressure over platinum single crystals: Surface analysis and pressure dependent mechanisms

Yeates, R.C.; Turner, J. E.; Gellman, Andrew J.; Somorjai, Gábor A.

doi:10.1016/s0039-6028(85)80021-2

Cited by 137 publications

(36 citation statements)

References 18 publications

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“…[19][20][21] Interesting effects like an oscillatory behaviour 22 of this reaction have been reported to take place under UHV conditions 23,24 and also at ambient pressures. 25 While the oscillations for Pt(100) observed in UHV 23,24 are induced by surface phase transitions, at high pressures this behaviour was attributed to SiO 2 formation due to platinum bulk impurities. 25 In the last years, an intense debate arouse 13,[26][27][28] with respect to CO oxidation at higher pressures, especially concerning the state of the catalyst in the active range.…”

Section: Introductionmentioning

confidence: 99%

“…25 While the oscillations for Pt(100) observed in UHV 23,24 are induced by surface phase transitions, at high pressures this behaviour was attributed to SiO 2 formation due to platinum bulk impurities. 25 In the last years, an intense debate arouse 13,[26][27][28] with respect to CO oxidation at higher pressures, especially concerning the state of the catalyst in the active range. Whereas Hendriksen et al 13,29,30 suggested a Mars-van Krevelen oxidation-reduction mechanism for Pt(110) and also Pd(100), with the respective metal oxide as highly active species, other groups report a metallic state of the surface in the most active regime.…”

Section: Introductionmentioning

confidence: 99%

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CO oxidation on Pt(111) at near ambient pressures

Calderón

Grabau

Óvári³

et al. 2016

The Journal of Chemical Physics

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Kinetics of the CO oxidation reaction on Pt(111) studied by in situ high-resolution x-ray photoelectron spectroscopy J. Chem. Phys. 120, 7113 (2004) The oxidation of CO on Pt(111) was investigated simultaneously by near ambient pressure X-ray photoelectron spectroscopy and online gas analysis. Different CO:O 2 reaction mixtures at total pressures of up to 1 mbar were used in continuous flow mode to obtain an understanding of the surface chemistry. By temperature-programmed and by isothermal measurements, the onset temperature of the reaction was determined for the different reactant mixtures. Highest turnover frequencies were found for the stoichiometric mixture. At elevated temperatures, the reaction becomes diffusionlimited in both temperature-programmed and isothermal measurements. In the highly active regime, no adsorbates were detected on the surface; it is therefore concluded that the catalyst surface is in a metallic state, within the detection limits of the experiment, under the applied conditions. Minor bulk impurities such as silicon were observed to influence the reaction up to total inhibition by formation of non-platinum oxides. C 2016 AIP Publishing LLC.[http://dx

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

CO oxidation on Pt(111) at near ambient pressures

Calderón

Grabau

Óvári³

et al. 2016

The Journal of Chemical Physics

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“…Three proposals were considered as most likely in the case of supported Pt catalysts: a model based upon adsorbate induced reconstructions of the low index faces exposed to the reactants at the surfaces of the supported Pt particles [42,48,[50][51][52]60]; "the carbon" model, wherein carbon, resulting from the dissociation of CO could accumulate on the surface, causing transient deactivation before being cleared away to reactivate the catalyst in the presence of oxygen [56][57][58][59]; and, the redox model wherein periodic switching of the Pt between metallic Pt 0 and oxidic states, was the source of the splitting of the catalysis into high reactivity and low reactivity states [39][40][41]43,44,49].…”

Section: Fast X-ray Diffraction (Xrd) and Debye-analysis Of Oscillatimentioning

confidence: 99%

“…As a result, by the 1980s, these phenomena had become the object of intense theoretical and experimental research that resulted in numerous mechanistic possibilities for their explanation , e.g., spatial separation and self-organization of the reactants [48,[60][61][62][63][64][65][66][67][68], surface reconstruction [42,48,[50][51][52]60], surface roughening/retexturing [49], the deposition and then ignition of carbon on the Pt [56][57][58][59], and reversible reduction-oxidation of the Pt itself [39][40][41][43][44][45]49,50].…”

Section: Introductionmentioning

confidence: 99%

Time Resolved Operando X-ray Techniques in Catalysis, a Case Study: CO Oxidation by O2 over Pt Surfaces and Alumina Supported Pt Catalysts

Newton

2017

Catalysts

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Abstract:The catalytic oxidation of CO by O 2 to form CO 2 over Pt surfaces and supported catalysts is one of the most studied catalytic reactions from both fundamental and applied points of view. This review aims to show how the application of a range of time resolved, X-ray based techniques, such as X-ray diffraction (XRD), Surface X-ray diffraction (SXRD), total X-ray scattering/pair distribution function (PDF), X-ray absorption (XAFS), X-ray emission (XES), and X-ray photoelectron spectroscopies (XPS), applied under operando conditions and often coupled to adjunct techniques (for instance mass spectrometry (MS) and infrared spectroscopy (IR)) have shed new light on the structures and mechanisms at work in this most studied of systems. The aim of this review is therefore to demonstrate how a fusion of the operando philosophy with the ever augmenting capacities of modern synchrotron sources can lead to new insight and catalytic possibilities, even in the case of a process that has been intensely studied for almost 100 years.

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“…From analysis of angular diffraction profiles it was concluded that the rate oscillations are associated with periodic oxidation and reduction of PtO and Pt 3 O 4 , reaching a maximum degree of oxidation of about 20-30% [131]. It is felt that the oxide mechanism is prevailing in CO oxidation on Pt catalysts, whenever the experiments are performed near atmospheric pressure, even if single crystal samples are used [132]. Theoretical modeling of the transition to oxide and its influence on the kinetics of CO oxidation shows good agreement with experimental observations [133].…”

Section: Oxidation Of Carbon Monoxide On Other Surfacesmentioning

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 oscillatory behavior of the CO oxidation reaction at atmospheric pressure over platinum single crystals: Surface analysis and pressure dependent mechanisms

Abstract: The oscillatory behavior of the catalyzed oxidation of carbon monoxide has been studied over platinum single crystals of At atmospheri~ pressure, silicon was always present on the platinum surfaces and was necessary to detect oscillatory behavior.

Cited by 137 publications

References 18 publications

CO oxidation on Pt(111) at near ambient pressures

CO oxidation on Pt(111) at near ambient pressures

Time Resolved Operando X-ray Techniques in Catalysis, a Case Study: CO Oxidation by O2 over Pt Surfaces and Alumina Supported Pt Catalysts

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

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