Chemische Aktivität von dünnen Oxidschichten: Starke Träger‐ Wechselwirkungen ergeben eine neue ZnO‐Dünnfilmphase

Schott, Vadim; Oberhofer, Harald; Birkner, Alexander; Xu, Mingchun; Wang, Yuemin; Mühler, Martin; Reuter, Karsten; Wöll, Christof

doi:10.1002/ange.201302315

Cited by 29 publications

(8 citation statements)

References 36 publications

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“…Because of the multi‐tasking ability of this class of catalysts, they are used in many applications and different scientific questions are currently studied based on Cu/ZnO‐based materials. The range spans from investigations of reaction mechanisms2–4 and metal–support interaction,5–8 over catalyst stability9 to new synthesis methods10–13 and attempts to find alternatives to Cu/ZnO 14–16. Usually, the progress made in the individual studies is well documented, but—as a general problem of catalysis research—a meaningful comparison of the model catalysts or newly developed materials of different reports is often rather difficult.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Characterisation of a Highly Active Cu/ZnO:Al Catalyst

et al. 2014

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We report the application of an optimised synthesis protocol of a Cu/ZnO:Al catalyst. The different stages of synthesis are all well-characterised by using various methods with regard to the (micro-)structural, textural, solid-state kinetic, defect and surface properties. The low amount of the Al promoter (3 %) influences but does not generally change the phase evolution known for binary Cu/ZnO catalysts. Its main function seems to be the introduction of defect sites in ZnO by doping. These sites as well as the large Cu surface area are responsible for the large N₂O chemisorption capacity. Under reducing conditions, the Al promoter, just as Zn, is found enriched at the surface suggesting an active role in the strong metal–support interaction between Cu and ZnO:Al. The different stages of the synthesis are comprehensively analysed and found to be highly reproducible in the 100 g scale. The resulting catalyst is characterised by a uniform elemental distribution, small Cu particles (8 nm), a porous texture (pore size of approximately 25 nm), high specific surface area (approximately 120 m² g^-1), a high amount of defects in the Cu phase and synergetic Cu–ZnO interaction. A high and stable performance was found in methanol synthesis. We wish to establish this complex but well-studied material as a benchmark system for Cu-based catalysts

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Section: Introductionmentioning

confidence: 99%

Synthesis and Characterisation of a Highly Active Cu/ZnO:Al Catalyst

et al. 2014

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“…[13][14][15][16] Recently Schott et al reported about the aplanar distortion of thin ZnO layers on copper, leading to a systematically less strongly oxidized Zn d+ . [17] In real catalysts, an amorphous overlayer of partially reduced ZnO x influencing the adsorption properties of copper is found covering the copper particles after the activation procedure, and the resulting catalyst characteristics have been extensively studied. [14,18] This can be seen as a precursor state to the partial formation of Cu-Zn surface alloys, which in fact might be the driving force for the strong interaction.…”

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confidence: 99%

Counting of Oxygen Defects versus Metal Surface Sites in Methanol Synthesis Catalysts by Different Probe Molecules

et al. 2014

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Different surface sites of solid catalysts are usually quantified by dedicated chemisorption techniques from the adsorption capacity of probe molecules, assuming they specifically react with unique sites. In case of methanol synthesis catalysts, the Cu surface area is one of the crucial parameters in catalyst design and was for over 25 years commonly determined using diluted N2O. To disentangle the influence of the catalyst components, different model catalysts were prepared and characterized using N2O, temperature programmed desorption of H2, and kinetic experiments. The presence of ZnO dramatically influences the N2O measurements. This effect can be explained by the presence of oxygen defect sites that are generated at the Cu-ZnO interface and can be used to easily quantify the intensity of Cu-Zn interaction. N2O in fact probes the Cu surface plus the oxygen vacancies, whereas the exposed Cu surface area can be accurately determined by H2.

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“…In the case of ZnO/Cu(111), calculations show that the charge transfer takes place also for Au 2‐4 and Au 20 clusters . This latter case may have practical implications, because a thin ZnO layer coating cupper nanoparticles has been identified as the active phase in industrial catalyst employed in the methanol synthesis . Also the case of Au n anionic species formed on top of MgO/Ag was shown to have interesting applications in terms of surface reactivity.…”

Section: Supported Clustersmentioning

confidence: 99%

Oxide‐Supported Gold Clusters and Nanoparticles in Catalysis: A Computational Chemistry Perspective

Tosoni

Pacchioni

2018

ChemCatChem

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This review provides an insight into the simulation of gold nanoparticles supported on oxide surfaces, with particular emphasis on the applications in heterogeneous catalysis. Some important methodological issues are firstly addressed: the polymorphism of small gold clusters, the difficulty in determining the actual charge state of adsorbed gold atoms, the relevance of long‐range dispersion and relativistic effects and the size‐effects in modelling Au nanoparticles. Then, the adsorption of Au species on oxides is addressed by comparing bulk oxides to ultrathin oxide films supported on metals. The role of defects as nucleation centres is also discussed. Finally, this review addresses the contribution from computational studies on the mechanisms involving Au‐based heterogeneous catalysts in important reactions such as the CO oxidation, the water‐gas shift reaction and the CO2 hydrogenation to methanol.

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Chemische Aktivität von dünnen Oxidschichten: Starke Träger‐ Wechselwirkungen ergeben eine neue ZnO‐Dünnfilmphase

Cited by 29 publications

References 36 publications

Synthesis and Characterisation of a Highly Active Cu/ZnO:Al Catalyst

Synthesis and Characterisation of a Highly Active Cu/ZnO:Al Catalyst

Counting of Oxygen Defects versus Metal Surface Sites in Methanol Synthesis Catalysts by Different Probe Molecules

Oxide‐Supported Gold Clusters and Nanoparticles in Catalysis: A Computational Chemistry Perspective

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