Visualization of oscillatory behaviour of Pt nanoparticles catalysing CO oxidation

Vendelbo, Søren Bastholm; Elkjær, Christian Fink; Falsig, Hanne; Puspitasari, Indra; Dona, Pleun; Mele, L.; Morana, B.; Nelissen, B.J.; Rijn, Richard M. van; Creemer, J.F.; Kooyman, Patricia J.; Helveg, Stig

doi:10.1038/nmat4033

Cited by 383 publications

(442 citation statements)

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“…The periodic switching between these states of low and high activity gives rise to the observed modulation of the reaction rate as it is observed in the oxidation of CO on Pt(110) under UHV conditions [1]. More recently, Vendelbo et al [54], using in situ time-resolved high-resolution transmission electron microscopy coupled with mass spectrometry, have shown that periodic changes in the oxidation of CO at atmospheric pressure are synchronous with a periodic faceting of Pt nanoparticles. It means that this so-called faceting mechanism can exist in a wide pressure range from UHV to elevated pressures.…”

Section: Discussionmentioning

confidence: 91%

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: Discussionmentioning

confidence: 91%

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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“…Prominent examples in which TEM was used to gain insights into dynamic structure changes of catalysts are the restructurings of Cu surfaces of a Cu/ZnO catalyst in different gas atmospheres (see also Figures 5 and 6),46, 47 carbon nanofiber growth on a Ni catalyst during methane decomposition,14 and the refacetting of Pt nanocrystals during CO oxidation in a nanoreactor at 1 bar and at elevated temperatures 89…”

Section: Advancing the Characterization Methods: Following Dynamicsmentioning

confidence: 99%

Future Challenges in Heterogeneous Catalysis: Understanding Catalysts under Dynamic Reaction Conditions

et al. 2016

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In the future, (electro‐)chemical catalysts will have to be more tolerant towards a varying supply of energy and raw materials. This is mainly due to the fluctuating nature of renewable energies. For example, power‐to‐chemical processes require a shift from steady‐state operation towards operation under dynamic reaction conditions. This brings along a number of demands for the design of both catalysts and reactors, because it is well‐known that the structure of catalysts is very dynamic. However, in‐depth studies of catalysts and catalytic reactors under such transient conditions have only started recently. This requires studies and advances in the fields of 1) operando spectroscopy including time‐resolved methods, 2) theory with predictive quality, 3) kinetic modelling, 4) design of catalysts by appropriate preparation concepts, and 5) novel/modular reactor designs. An intensive exchange between these scientific disciplines will enable a substantial gain of fundamental knowledge which is urgently required. This concept article highlights recent developments, challenges, and future directions for understanding catalysts under dynamic reaction conditions.

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“…However, surfaces of most materials tend to restructure in reactive gas environments and such changes have a profound feedback on catalysts' properties. It has therefore remained an important milestone in catalysis and surface sciences to functionalize electron microscopy for operando studies in which the catalyst surface structure and properties are simultaneously evaluated at the atomic-scale and under relevant reaction conditions.Here, we report on a nanoreactor system that enables combined electron microscopy and functional measurements of catalysts [2][3][4][5][6] and is available from Thermo Fisher Scientific. The nanoreactor is a micro-electro-mechanical system device integrating a 5-µm-high, one-pass and bypass-free gas-flow channel, a microheater and an array of 15-nm-thick electron-transparent windows of silicon nitride (Figure 1) [4].…”

mentioning

confidence: 99%

“…Moreover, mass spectrometry of gas exiting the reaction zone is made possible by the small reaction volume of ca. 0.3 nL and reaction calorimetry is accessed from the power compensation used for isothermal operation of the microheater [6].…”

mentioning

confidence: 99%

“…Based on such observations, structure-activity relationship will be outlined for e.g. the steady-state and oscillatory catalytic oxidation of carbon monoxide over Pt nanoparticles [6]. These examples demonstrate exciting possibilities for including information about the exposed surface sites into the description of dynamic properties and functions of catalysts.…”

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confidence: 99%

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Atomic-Resolution Imaging of Heterogeneous Catalysts at Work

Helveg¹,

Elkjcer²,

Jespersen³

et al. 2018

Microsc Microanal

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Transmission electron microscopy (TEM) has become indispensable in the study of heterogeneous catalysts. The ability to acquire atomic-resolution images of catalysts opens up for unprecedented new information about the catalyst surface that benefits the understanding of structure-sensitivity in catalysis [1]. However, surfaces of most materials tend to restructure in reactive gas environments and such changes have a profound feedback on catalysts' properties. It has therefore remained an important milestone in catalysis and surface sciences to functionalize electron microscopy for operando studies in which the catalyst surface structure and properties are simultaneously evaluated at the atomic-scale and under relevant reaction conditions.Here, we report on a nanoreactor system that enables combined electron microscopy and functional measurements of catalysts [2][3][4][5][6] and is available from Thermo Fisher Scientific. The nanoreactor is a micro-electro-mechanical system device integrating a 5-µm-high, one-pass and bypass-free gas-flow channel, a microheater and an array of 15-nm-thick electron-transparent windows of silicon nitride (Figure 1) [4]. This nanoreactor is operational with variable gas flows (0-0.1 sccm/min), ambient pressure levels (> 1 bar) and elevated temperatures (25-700 o C), while maintaining the inherent 1Å resolution in modern electron microscopes. Moreover, mass spectrometry of gas exiting the reaction zone is made possible by the small reaction volume of ca. 0.3 nL and reaction calorimetry is accessed from the power compensation used for isothermal operation of the microheater [6].The nanoreactor performance and application will be showcased by observations of Pt nanoparticles under oxidizing and reducing reaction conditions. Specifically, high-resolution TEM images were acquired of the Pt nanoparticles under exposure to reactive gas environments synchronously with mass spectrometry and calorimetry data. Based on such observations, structure-activity relationship will be outlined for e.g. the steady-state and oscillatory catalytic oxidation of carbon monoxide over Pt nanoparticles [6]. These examples demonstrate exciting possibilities for including information about the exposed surface sites into the description of dynamic properties and functions of catalysts.

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Visualization of oscillatory behaviour of Pt nanoparticles catalysing CO oxidation

Cited by 383 publications

References 40 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

Future Challenges in Heterogeneous Catalysis: Understanding Catalysts under Dynamic Reaction Conditions

Atomic-Resolution Imaging of Heterogeneous Catalysts at Work

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