Bistability and oscillations in CO oxidation studied with scanning tunnelling microscopy inside a reactor

Hendriksen, Bas L. M.; Bobaru, S.C.; Frenken, J.W.M.

doi:10.1016/j.cattod.2005.02.041

Cited by 88 publications

(71 citation statements)

References 66 publications

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“…A similar mechanism was previously proposed by Hendriksen and co-workers [59] for the rate oscillations in the oxidation of CO over Pt(110) and Pd(100) single crystals observed under near atmospheric pressure (~0.5 bar). The authors supposed that the rate oscillations were not due to the bistability in the Langmuir-Hinshelwood kinetics, but arose from the periodic switching between the low-reactive metallic surface and the high-reactive oxide surface.…”

Section: Discussionsupporting

confidence: 80%

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Evolution of self-sustained kinetic oscillations in the catalytic oxidation of propane over a nickel foil

Каичев

Teschner

Saraev

et al. 2016

Journal of Catalysis

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The evolution of self-sustained reaction-rate oscillations in the catalytic oxidation of propane over a nickel foil has been studied in situ using X-ray photoelectron spectroscopy coupled with on line mass spectrometry and gas chromatography. Changes in the effective surface area and in the catalyst morphology under reaction conditions have been examined by scanning electron microscopy and a krypton adsorption technique. It is shown that the regular kinetic oscillations arise under oxygen-lean conditions. CO, CO 2 , H 2 , H 2 O, and propylene are detected as products.The conversion of propane oscillates in a range from 1% to 23%. During the half-periods with high activity, the main reaction pathway is the partial oxidation of propane: selectivity toward CO achieves 98%. In contrast, during the half-periods with low activity, the reaction proceeds through three competitive pathways: the partial oxidation of propane, the total oxidation of propane, and the dehydrogenation of propane to propylene. The driving force for the selfsustained kinetic oscillations is the periodic reoxidation of nickel. According to the Ni2p and O1s core-level spectra measured in situ, the high-active catalyst surface is represented by metallic nickel, whereas during the inactive half-periods the catalyst surface is covered with a thick layer of NiO. The intensity of O1s spectra follows the oscillations of O 2 in the gas phase during the oxidation of propane. It is found that during the induction period before the regular oscillations appear, a rough and porous structure develops because of strong reconstruction of the catalyst surface. The thickness of the reconstructed layer is approximately 10-20 µm. This process is accompanied with at least an 80-fold increase in the effective surface area compared with a clean, non-treated nickel foil, which undoubtedly leads to a drastic increase in the number of active sites. We believe that it is the main reason for the induction period always being  Corresponding author.E-mail address: vvk@catalysis.ru (V.V. Kaichev) 2 observed before the appearance of self-sustained oscillations in the catalytic oxidation of light hydrocarbons over catalysts with a low specific surface area (single crystals, foils, or wires).Moreover, without such reconstruction, the oscillations cannot arise due to low activity of such catalysts.

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Section: Discussionsupporting

confidence: 80%

“…However, afterward this mechanism was subjected to criticism. In contrast to results by Hendriksen et al [59] obtained in the mbar pressure range, no surface oxides were detected by XPS on the Pt(110) surface during the oxidation of CO [60]. Therefore, some additional experiments are needed for explaining these discrepancies.…”

Section: Discussioncontrasting

confidence: 62%

Evolution of self-sustained kinetic oscillations in the catalytic oxidation of propane over a nickel foil

Каичев

Teschner

Saraev

et al. 2016

Journal of Catalysis

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“…14 The oscillatory behavior of the reaction is also explained by metal-oxide islands formation, 15 which was never observed under UHV conditions. 16 Bridging the pressure gap by theoretical means was also attempted and the higher reactivity of such an oxide phase compared with that of a Pt surface was shown.…”

Section: Introductionmentioning

confidence: 99%

“…14,15 Two active phases were observed in an O 2 -rich atmosphere; one phase where reaction occurs on Pt terraces with a low activity, and the other phase with a high activity where Pt oxide islands were formed on the Pt surface.…”

Section: Reaction Mechanism and Possible Surface Speciesmentioning

confidence: 99%

Simultaneous in situ monitoring of surface and gas species and surface properties by modulation excitation polarization-modulation infrared reflection-absorption spectroscopy: CO oxidation over Pt film

Urakawa

Bürgi

Schläpfer

et al. 2006

The Journal of Chemical Physics

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A method for in situ monitoring of surface and gas species utilizing separately the difference and sum reflectivity of two polarizations, normal and parallel to the surface, measured by polarization-modulation infrared reflection-absorption spectroscopy is presented. Surface and gas-phase spectra were separately but simultaneously obtained from the reflectivities. The technique is combined with modulation excitation spectroscopy to further enhance the sensitivity, and a small-volume cell was designed for this purpose. CO oxidation over a 40 nm Pt film on aluminum was investigated under moderate pressure ͑atmospheric pressure, 5% CO, and 5%-40% O 2 ͒ at 373-433 K. The surface species involved in the oxidation process and the gas-phase species, both reactant ͑CO͒ and product ͑CO 2 ͒, could be simultaneously monitored and analyzed quantitatively. In addition, the reflectivity change of the sample during the reaction was assigned to a near-surface bulk property change, that is, surface reconstruction to the oxide phase. Under an O 2 -rich atmosphere, two reactive phases, denoted as low-and high-activity phases, were identified. A large amount of atop CO was observed during the low-activity phase, while the adsorbed CO completely disappeared during the high-activity phase. The presence of an infrared-inactive CO 2 precursor formed by the reaction between surface oxide and gaseous CO during the high-activity phase was inferred. The desorption of the CO 2 precursor is facilitated under a CO-rich atmosphere, most likely, by surface reconstruction to metallic Pt and a competitive adsorption of CO on the surface.

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“…6b). In combination with SMFS activity analysis, these time-resolved diffractograms can reveal local turnover-induced structural transformations in the catalysts (see above) (79). Furthermore, high-resolution optical images obtained by mapping stochastic turnover events (45,46) can be compared with x-ray diffraction data of the inorganic catalyst, thus directly linking activity to crystal properties.…”

Section: Integration Of Techniques and Perspectivesmentioning

confidence: 99%

Single-molecule fluorescence spectroscopy in (bio)catalysis

Roeffaers

Cremer

Uji‐i

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

146

114

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The ever-improving time and space resolution and molecular detection sensitivity of fluorescence microscopy offer unique opportunities to deepen our insights into the function of chemical and biological catalysts. Because single-molecule microscopy allows for counting the turnover events one by one, one can map the distribution of the catalytic activities of different sites in solid heterogeneous catalysts, or one can study time-dependent activity fluctuations of individual sites in enzymes or chemical catalysts. By experimentally monitoring individuals rather than populations, the origin of complex behavior, e.g., in kinetics or in deactivation processes, can be successfully elucidated. Recent progress of temporal and spatial resolution in single-molecule fluorescence microscopy is discussed in light of its impact on catalytic assays. Key concepts are illustrated regarding the use of fluorescent reporters in catalytic reactions. Future challenges comprising the integration of other techniques, such as diffraction, scanning probe, or vibrational methods in single-molecule fluorescence spectroscopy are suggested.S ingle-molecule fluorescence spectroscopy (SMFS) has recently developed into a powerful tool for studying biophysical and biochemical phenomena. In studies of enzymatic catalysis, SMFS has revealed that there are large differences between the catalytic activity of individual enzymes within a population (''static disorder'') and that the rate constant (k cat ) of an individual enzyme may strongly fluctuate over time (''dynamic disorder''), the latter resulting from conformational changes of the enzyme. The recent application of SMFS to catalysis by solid materials has shown that heterogeneities in k cat also exist between individual catalytic crystals of one powder sample and even between the sites of an individual crystal. In this case, heterogeneity might arise from different chemical environments within the catalyst sample. The observation of heterogeneity in the k cat of those different catalytic systems suggests that the parallel introduction and evolution of SMFS techniques in bioand chemocatalysis will deepen our insights in almost any type of catalytic conversion. Indeed, the challenge to derive overall kinetics from the contributions of individuals within a population is essentially the same for biological, heterogeneous and even homogeneous systems, as discussed in From Populations to Individuals.From a technical viewpoint, SMFS requires strongly fluorescent probe molecules. The concepts to use such probes and even the probes themselves can be exchanged freely between heterogeneous, homogeneous, and biocatalysis, as discussed in Probes for SMFS in (Bio)Catalysis. If one wants to map in even more detail the contributions of the individual enzymes or catalytic sites to the overall kinetics, further improvements of the spatial and temporal resolution of SMFS will be required (see Spatial Resolution: Micro-and Nanoscopy and Time Resolution and Dynamics). Finally, to complement the information from S...

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Bistability and oscillations in CO oxidation studied with scanning tunnelling microscopy inside a reactor

Cited by 88 publications

References 66 publications

Evolution of self-sustained kinetic oscillations in the catalytic oxidation of propane over a nickel foil

Evolution of self-sustained kinetic oscillations in the catalytic oxidation of propane over a nickel foil

Simultaneous in situ monitoring of surface and gas species and surface properties by modulation excitation polarization-modulation infrared reflection-absorption spectroscopy: CO oxidation over Pt film

Single-molecule fluorescence spectroscopy in (bio)catalysis

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