Comparison of the early stages of corrosion of copper and iron investigated by in situ TM-AFM

Kleber, Christoph; Weissenrieder, Jonas; Schreiner, Manfred; Leygraf, Christofer

doi:10.1016/s0169-4332(02)00491-9

Cited by 24 publications

(3 citation statements)

References 6 publications

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“…Since these results lie in good agreement with literature data (28,29) for various iron particle sizes, the roughness factor we determined was also used for the calculation of iron surface atoms of the large iron particles.…”

Section: Particle Characterizationsupporting

confidence: 83%

An innovative approach for fatty acid reduction to fatty aldehydes

Johannsen

Baek

Fieg

et al. 2021

Green Chemistry Letters and Reviews

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The increasing demand for fatty aldehydes as natural flavoring agents nowadays grapples with current production processes requiring harsh reaction conditions and hazardous chemicals. Our research group proved the concept of an innovative, sustainable process based on renewable plant oils for fatty aldehyde production: fatty acids reduction via zerovalent iron. In this study, we present for the first time extensive supporting data characterizing the metal particles used as co-reactants and the core step of the reaction, with varying process parameters. Furthermore, process improvement is demonstrated in that addition of fatty ester-obtained alcohol regenerates metal particles, thereby increasing process yield and selectivity as well as avoiding resource waste. Hexanoic acid reduction to hexanal in the presence of iron particles was used as a reference reaction system, generating a 40% hexanoic acid conversion using Fe 36 μmparticles. To increase overall process sustainability, we explored the possibility of an in toto exploitation of the starting materials (esters) through an a posteriori reduction of the oxidized iron, exemplarily with the alcohol hexanol. The hexanoic acid conversion rate was thereby increased to 83%, while a 44-fold increase in hexanal yield was observed.

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Section: Particle Characterizationsupporting

confidence: 83%

An innovative approach for fatty acid reduction to fatty aldehydes

Johannsen

Baek

Fieg

et al. 2021

Green Chemistry Letters and Reviews

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“…Under ambient atmosphere the oxidation of copper proceeds through an initial formation of a thin film of cuprous oxide (Cu 2 O). Upon further exposure copper will eventually become fully oxidized (CuO). − The formation of CuO results in loss of catalytically active Cu + centers and therefore determines the oxidation and reduction properties of cuprous oxide, critical for the understanding of the deactivation processes of copper catalysts.…”

Section: Introductionmentioning

confidence: 99%

Redox Properties of Cu₂O(100) and (111) Surfaces

et al. 2018

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Intense research efforts are directed toward Cu and Cu2O based catalysts as they are viewed as potential replacements for noble metal catalysts. However, applications are hampered by deactivation, e.g., through facile complete oxidation to CuO. Despite the importance of the redox processes for Cu2O catalysts, a molecular level understanding of the deactivation process is still lacking. Here we study the initial stages of oxidization of well-defined Cu2O bulk single crystals of (100) and (111) termination by means of synchrotron radiation X-ray photoemission spectroscopy (XPS) and scanning tunneling microscopy (STM). Exposure of the (100) surface to 1 mbar O2 at 25 °C results in the formation of a 1.0 monolayer (ML) CuO surface oxide. The surface is covered by 0.7 ML OH groups from trace moisture in the reaction gas. In contrast, neither hydroxylation nor oxidation was observed on the (111) surface under similar mild exposure conditions. On Cu2O(111) the initial formation of CuO requires annealing to ∼400 °C in 1 mbar O2, highlighting the markedly different reactivity of the two Cu2O surfaces. Annealing of the (100) surface, under ultrahigh vacuum conditions, to temperatures up to ∼225 °C resulted in removal of the OH groups (0.46 ML decrease) at a rate similar to a detected increase in CuO coverage (0.45 ML increase), suggesting the reaction path 2OHadsorbed + Cu2Osolid → H2Ogas + 2CuOsolid. STM was used to correlate the observed changes in surface chemistry with surface morphology, confirming the surface hydroxylation and CuO formation. The STM analysis showed dramatic changes in surface morphology demonstrating a high mobility of the active species under reaction conditions.

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“…Since copper is both malleable and corrosion resistant, it is also frequently used as plumbing and roofing material . In such applications the most prevalent initial corrosion product is cuprous oxide (Cu 2 O); a thin film of Cu 2 O is rapidly formed on copper upon exposure to an ambient environment. − Besides being an abundant corrosion product, Cu 2 O has properties making it suitable for applications within e.g. catalysts for CO oxidation, − photocatalytic water splitting, and propene epoxidation. − …”

Section: Introductionmentioning

confidence: 99%

Interaction of Sulfur Dioxide and Near-Ambient Pressures of Water Vapor with Cuprous Oxide Surfaces

et al. 2017

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The interaction of water vapor and sulfur dioxide (SO2) with single crystal cuprous oxide (Cu2O) surfaces of (100) and (111) termination was studied by photoelectron spectroscopy (PES) and density functional theory (DFT). Exposure to near-ambient pressures of water vapor, at 5 × 10–3 %RH and 293 K, hydroxylates both Cu2O surfaces with OH coverage up to 0.38 copper monolayers (ML) for (100) and 0.25 ML for (111). O 1s surface core level shifts indicate that the hydroxylation lifts the (3,0;1,1) reconstruction of the clean (100) surface. On both clean Cu2O terminations, SO2 adsorbs to unsaturated surface oxygen atoms to form SO3 species with coverage, after a saturating SO2 dose, corresponding to 0.20 ML on the Cu2O(100) surface and 0.09 ML for the Cu2O(111) surface. Our combined DFT and PES results suggest that the SO2 to SO3 transformation is largely facilitated by unsaturated copper atoms at the Cu2O(111) surface. SO3-terminated surfaces exposed to low doses of water vapor (≤100 langmuirs) in ultrahigh vacuum show no adsorption or reaction. However, during exposure to near-ambient pressures of water vapor, the SO3 species dissociate, and sulfur replaces a Cu2O lattice oxygen in a reaction that forms Cu2S. The hydroxylation of the Cu2O surfaces is believed to play a central role in the reaction.

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Comparison of the early stages of corrosion of copper and iron investigated by in situ TM-AFM

Cited by 24 publications

References 6 publications

An innovative approach for fatty acid reduction to fatty aldehydes

An innovative approach for fatty acid reduction to fatty aldehydes

Redox Properties of Cu₂O(100) and (111) Surfaces

Interaction of Sulfur Dioxide and Near-Ambient Pressures of Water Vapor with Cuprous Oxide Surfaces

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Comparison of the early stages of corrosion of copper and iron investigated by in situ TM-AFM

Cited by 24 publications

References 6 publications

An innovative approach for fatty acid reduction to fatty aldehydes

An innovative approach for fatty acid reduction to fatty aldehydes

Redox Properties of Cu2O(100) and (111) Surfaces

Interaction of Sulfur Dioxide and Near-Ambient Pressures of Water Vapor with Cuprous Oxide Surfaces

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Product

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Redox Properties of Cu₂O(100) and (111) Surfaces