CO Oxidation on Metal‐Supported Ultrathin Oxide Films: What Makes Them Active?

Martynova, Y.; Shaikhutdinov, Shamil K.; Freund, Hans‐Joachim

doi:10.1002/cctc.201300212

Cited by 31 publications

(31 citation statements)

References 76 publications

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“…By comparison with other films, we concluded that oxygen binding energy in the films plays the decisive role for the CO oxidation reaction in an excess of oxygen [11]. The more weakly bound the oxygen species, the higher the reaction rate.…”

Section: Introductionmentioning

confidence: 83%

“…In contrast, the planar morphology of ZnO films grown on Ag(111) and Pt (111) is maintained in the reaction. For dense ZnO (0001) films, the CO oxidation rate is independent of the metal support, and this rate has turned out to be the smallest amongst the thin oxide films studied under the same conditions [11]. At submonolayer coverages, the ZnO/Pt (111) films used in these calculations were represented by a close-packed layer of metal cations (bonded to Pt) and a topmost layer of oxygen anions.…”

Section: Reactivity Of Metal-supported Zno(0001) Films: Comparisonmentioning

confidence: 99%

“…In particular, Ru-oxide films on Ru(0001) [6][7][8] and oxide films on Pt(111) [9][10][11] show a higher CO oxidation rate at nearatmospheric pressures and low temperatures at which pure metals are essentially inactive. The promotional effect of oxide overlayers on the reactivity observed on model planar systems allows one to rationalize the enhanced reactivity observed on highly dispersed metal particles, encapsulated by the supporting oxide due to the a so-called strong metal-support interaction, as has been demonstrated for iron oxide-supported Pt catalysts [12].…”

Section: Introductionmentioning

confidence: 99%

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Reactivity of Ultra-Thin ZnO Films Supported by Ag(111) and Cu(111): A Comparison to ZnO/Pt(111)

et al. 2014

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Abstract.We studied structure and reactivity of ZnO(0001) ultrathin films grown on Ag (111) and Cu(111) single crystal surfaces. Structural characterization was carried out by scanning tunneling microscopy, Auger electron spectroscopy, low-energy electron diffraction, and temperature programmed desorption. The CO oxidation behavior of the films was studied at low temperature (450 K) at near atmospheric pressures using gas chromatography. For ZnO/Cu(111), it is shown that under reaction conditions ZnO readily migrates into the Cu crystal bulk, and the reactivity is governed by a CuO x oxide film formed in the reaction ambient. In contrast, the planar structure of ZnO films on Ag(111) is maintained, similarly to the previously studied ZnO films on Pt(111). At sub-monolayer coverages, the "inverse" model catalysts are represented by two-monolayer-thick ZnO(0001) islands on Pt(111) and Ag(111) supports. While the CO oxidation rate is considerably increased on ZnO/Pt(111), which is attributed to active sites at the metal/oxide boundary, sub-monolayer ZnO films on Ag(111) did not show such an effect, and the reactivity was inhibited with increasing film coverage. The results are explained by much stronger adsorption of CO on Pt(111) as compared with Ag(111) in proximity to O species at the oxide/metal boundary. In addition, the water-gas shift and reverse water-gas shift reactions were examined on ZnO/Ag(111), which revealed no promotional effect of ZnO on the reactivity of Ag under the conditions studied. The latter finding suggests that wetting phenomena of ZnO on metals does not play a crucial role in the catalytic performance of ZnObased real catalysts in those reactions.

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Section: Introductionmentioning

confidence: 83%

Section: Reactivity Of Metal-supported Zno(0001) Films: Comparisonmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Reactivity of Ultra-Thin ZnO Films Supported by Ag(111) and Cu(111): A Comparison to ZnO/Pt(111)

et al. 2014

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“…This has been observed to be the case in oxygen activation reactions such as 16 O 2 / 18 O 2 isotopic exchange [24] and oxidation of CH 4 [24], C 3 H 6 [25], H 2 [24][25][26][27] and CO [28][29][30]. The activity in the catalytic oxidation of CO on thin metal oxide films has also been correlated to the activation energy for oxygen desorption [31], which scales with the heat of chemisorption. Furthermore, the heat of chemisorption has also been found to be among the factors that play a role for the selectivity in oxidation of benzaldehyde [32] and methanol [33].…”

Section: Introductionmentioning

confidence: 99%

Importance of the oxygen bond strength for catalytic activity in soot oxidation

Christensen

Grunwaldt

Jensen

2016

Applied Catalysis B: Environmental

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The oxygen bond strength on a catalyst, as measured by the heat of oxygen chemisorption, is observed to be a very important parameter for the activity of the catalyst in soot oxidation. With both intimate contact between soot and catalyst (tight contact) and with the solids stirred loosely together (loose contact) the rate constants for a number of catalytic materials outline a volcano curve when plotted against their heats of oxygen chemisorption. However, the optima of the volcanoes correspond to different heats of chemisorption for the two contact situations. In both cases the activation energies for soot oxidation follow linear Brønsted-Evans-Polanyi relationships with the heat of oxygen chemisorption. Among the tested metal or metal oxide catalysts Co 3 O 4 and CeO 2 were nearest to the optimal bond strength in tight contact oxidation, while Cr 2 O 3 was nearest to the optimum in loose contact oxidation. The optimum of the volcano curve in loose contact is estimated to occur between the bond strengths of α-Fe 2 O 3 and α-Cr 2 O 3 . Guided by an interpolation principle Fe a Cr b O x binary oxides were tested, and the activity of these oxides was observed to pass through an optimum for an FeCr 2 O x binary oxide catalyst, which exhibited a rate constant at 550 °C that was 2.3 times higher than the one for pure α-Cr 2 O 3 and 29 times higher than the one for pure α-Fe 2 O 3 .

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“…While several other oxide/metal combinations have meanwhile been tested for enhanced catalytic activity in CO oxidation [28], experimental verification of the promotional effect of a metal support in CO oxidation over ultra-thin MgO films is still lacking.…”

Section: Introductionmentioning

confidence: 99%

The role of exposed silver in CO oxidation over MgO(0 0 1)/Ag(0 0 1) thin films

et al. 2015

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The reactivity of MgO(001) films deposited on Ag(001) and Mo(001) in CO oxidation as a function of oxide film thickness was investigated experimentally at ambient pressure reaction conditions. MgO films grown on Mo(001) were found to be inactive in CO oxidation, whereas activity enhancement with decreasing oxide film thickness was observed for MgO(001)/Ag(001). In-situ infrared and post-reaction X-ray photoemission data showed that ultra-thin MgO films interact much more strongly with the reactants and residual water than bulk-like MgO. Poisoning of the MgO surfaces by the resultant accumulation of carbonate and hydroxyl species is suggested to inhibit the reactivity in CO oxidation. Detailed investigations of the surface structure of MgO(001)/Ag(001) films indicate that silver adislands on Ag(001), which are formed during MgO growth, are responsible for the enhancement of CO oxidation activity over ultrathin MgO(001)/Ag(001) films.

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CO Oxidation on Metal‐Supported Ultrathin Oxide Films: What Makes Them Active?

Cited by 31 publications

References 76 publications

Reactivity of Ultra-Thin ZnO Films Supported by Ag(111) and Cu(111): A Comparison to ZnO/Pt(111)

Reactivity of Ultra-Thin ZnO Films Supported by Ag(111) and Cu(111): A Comparison to ZnO/Pt(111)

Importance of the oxygen bond strength for catalytic activity in soot oxidation

The role of exposed silver in CO oxidation over MgO(0 0 1)/Ag(0 0 1) thin films

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