<i>In situ</i> gas–surface interactions: approaching realistic conditions

Lundgren, Edvin; Over, Herbert

doi:10.1088/0953-8984/20/18/180302

Cited by 15 publications

(11 citation statements)

References 18 publications

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“… 4 − 8 Such systems have model character in terms of catalytic CVD of all other carbon nanostructures inasmuch as flat, well-defined catalyst surfaces have been used for decades in surface science as model systems for nanoparticulate catalysts typically used in industrial heterogeneous catalysis. 3 , 9 …”

Section: Introductionmentioning

confidence: 99%

Interdependency of Subsurface Carbon Distribution and Graphene–Catalyst Interaction

et al. 2014

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The dynamics of the graphene–catalyst interaction during chemical vapor deposition are investigated using in situ, time- and depth-resolved X-ray photoelectron spectroscopy, and complementary grand canonical Monte Carlo simulations coupled to a tight-binding model. We thereby reveal the interdependency of the distribution of carbon close to the catalyst surface and the strength of the graphene–catalyst interaction. The strong interaction of epitaxial graphene with Ni(111) causes a depletion of dissolved carbon close to the catalyst surface, which prevents additional layer formation leading to a self-limiting graphene growth behavior for low exposure pressures (10–6–10–3 mbar). A further hydrocarbon pressure increase (to ∼10–1 mbar) leads to weakening of the graphene–Ni(111) interaction accompanied by additional graphene layer formation, mediated by an increased concentration of near-surface dissolved carbon. We show that growth of more weakly adhered, rotated graphene on Ni(111) is linked to an initially higher level of near-surface carbon compared to the case of epitaxial graphene growth. The key implications of these results for graphene growth control and their relevance to carbon nanotube growth are highlighted in the context of existing literature.

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Section: Introductionmentioning

confidence: 99%

Interdependency of Subsurface Carbon Distribution and Graphene–Catalyst Interaction

et al. 2014

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“… 3 , 4 For this reason, the surface science community has developed traditional surface-sensitive techniques such as scanning tunneling microscopy (STM), 5 surface X-ray diffraction (SXRD), 6 and high-pressure X-ray photoemission spectroscopy (HPXPS) 7 to operate at higher pressure, in situ. 8 − 10 What is often overseen is that at higher pressure the flow of gases through the catalysis reactor will have a substantial impact on the interaction between the catalyst surface and gas molecules; 11 , 12 nevertheless, studies of the gas composition adjacent to the catalyst surface is to a large extent lacking, which emphasizes the importance of studying the gas phase when aiming for characterization of catalysts under realistic conditions. CO oxidation is one of the most investigated reactions in heterogeneous catalysis and has been studied in great detail.…”

Section: Introductionmentioning

confidence: 99%

Real-Time Gas-Phase Imaging over a Pd(110) Catalyst during CO Oxidation by Means of Planar Laser-Induced Fluorescence

et al. 2015

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The gas composition surrounding a catalytic sample has direct impact on its surface structure, which is essential when in situ investigations of model catalysts are performed. Herein a study of the gas phase close to a Pd(110) surface during CO oxidation under semirealistic conditions is presented. Images of the gas phase, provided by planar laser-induced fluorescence, clearly visualize the formation of a boundary layer with a significantly lower CO partial pressure close to the catalytically active surface, in comparison to the overall concentration as detected by mass spectrometry. The CO partial pressure variation within the boundary layer will have a profound effect on the catalysts’ surface structure and function and needs to be taken into consideration for in situ model catalysis studies.

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“…Recently, an increasing number of experimental techniques providing in situ information on gas surface interactions in the mbar to bar pressure range have become available. [4][5][6][7][8] These techniques can reveal atomic level structure of the metal catalyst and the supporting oxide. One important observation achieved using these in situ techniques is that the catalyst sometimes exhibits its active phase only under reaction conditions.…”

Section: A Introductionmentioning

confidence: 99%

Reversible formation of a PdCx phase in Pd nanoparticles upon CO and O2 exposure

Balmès

Resta

Wermeille

et al. 2012

Phys. Chem. Chem. Phys.

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The structure and chemical composition of Pd nanoparticles exposed to pure CO and mixtures of CO and O(2) at elevated temperatures have been studied in situ by a combination of X-ray Diffraction and X-ray Photoelectron Spectroscopy in pressures ranging from ultra high vacuum to 10 mbar and from room temperature to a few hundred degrees celsius. Our investigation shows that under CO exposure, above a certain temperature, carbon dissolves into the Pd particles forming a carbide phase. Upon exposure to CO and O(2) mixtures, the carbide phase forms and disappears reversibly, switching at the stoichiometric ratio for CO oxidation. This finding opens new scenarios for the understanding of catalytic oxidation of C-based molecules.

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In situ gas–surface interactions: approaching realistic conditions

Cited by 15 publications

References 18 publications

Interdependency of Subsurface Carbon Distribution and Graphene–Catalyst Interaction

Interdependency of Subsurface Carbon Distribution and Graphene–Catalyst Interaction

Real-Time Gas-Phase Imaging over a Pd(110) Catalyst during CO Oxidation by Means of Planar Laser-Induced Fluorescence

Reversible formation of a PdCx phase in Pd nanoparticles upon CO and O2 exposure

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