On the Role of Oxygen Defects in the Catalytic Performance of Zinc Oxide

Polarz, Sebastian; Strunk, Jennifer; Ischenko, Vladislav; Berg, Maurits W. E. van den; Hinrichsen, Olaf; Mühler, Martin; Drieß, Matthias

doi:10.1002/anie.200503068

Cited by 246 publications

(203 citation statements)

References 45 publications

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“…Since the surface layer is only ZnO, it has been revealed that V O s can behave as important adsorption and active sites for catalysis, which strongly inuence the reactivity of metal oxides. 77 Notably, V O ++ forms aer capturing a hole from the VB.…”

Section: Role Of Holesmentioning

confidence: 99%

Selective isolation of the electron or hole in photocatalysis: ZnO–TiO2 and TiO2–ZnO core–shell structured heterojunction nanofibers via electrospinning and atomic layer deposition

et al. 2014

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Heterojunctions are a well-studied material combination in photocatalysis studies, the majority of which aim to improve the efficacy of the catalysts. Developing novel catalysts begs the question of which photo-generated charge carrier is more efficient in the process of catalysis and the associated mechanism. To address this issue we have fabricated core-shell heterojunction (CSHJ) nanofibers from ZnO and TiO 2 in two combinations where only the 'shell' part of the heterojunction is exposed to the environment to participate in the photocatalysis. Core and shell structures were fabricated via electrospinning and atomic layer deposition, respectively which were then subjected to calcination. These CSHJs were characterized and studied for photocatalytic activity (PCA). These two combinations expose electrons or holes selectively to the environment. Under suitable illumination of the ZnO-TiO 2 CSHJ, e/h pairs are created mainly in TiO 2 and the electrons take part in catalysis (i.e. reduce the organic dye) at the conduction band or oxygen vacancy sites of the 'shell', while holes migrate to the core of the structure. Conversely, holes take part in catalysis and electrons diffuse to the core in the case of a TiO 2 -ZnO CSHJ. The results further revealed that the TiO 2 -ZnO CSHJ shows $1.6 times faster PCA when compared to the ZnO-TiO 2 CSHJ because of efficient hole capture by oxygen vacancies, and the lower mobility of holes.

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Section: Role Of Holesmentioning

confidence: 99%

Selective isolation of the electron or hole in photocatalysis: ZnO–TiO2 and TiO2–ZnO core–shell structured heterojunction nanofibers via electrospinning and atomic layer deposition

et al. 2014

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“…Using pyrolysis and gasification both can be successfully transformed to syngas 1, 2 which, in turn, is used in methanol formation. [3][4][5][6] Zeolite ZSM-5 is a well-known catalyst of MTH and MTG transformations. 7 Although this catalyst was used in the MTG process from early 1970s, its deactivation by coke formation dampened its applications.…”

Section: Introductionmentioning

confidence: 99%

Metal oxide–zeolite composites in transformation of methanol to hydrocarbons: do iron oxide and nickel oxide matter?

et al. 2016

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(2016) Metal oxide-zeolite composites in transformation of methanol to hydrocarbons : do iron oxide and nickel oxide matter? RSC Advances, 6 (79). pp. 75166-75177. Permanent WRAP URL:http://wrap.warwick.ac.uk/81920 Copyright and reuse:The Warwick Research Archive Portal (WRAP) makes this work of researchers of the University of Warwick available open access under the following conditions. Copyright © and all moral rights to the version of the paper presented here belong to the individual author(s) and/or other copyright owners. To the extent reasonable and practicable the material made available in WRAP has been checked for eligibility before being made available.Copies of full items can be used for personal research or study, educational, or not-for-profit purposes without prior permission or charge. Provided that the authors, title and full bibliographic details are credited, a hyperlink and/or URL is given for the original metadata page and the content is not changed in any way. Publisher statement:First published by Royal Society of Chemistry 2016 http://dx.doi.org/10.1039/C6RA19471K A note on versions:The version presented here may differ from the published version or, version of record, if you wish to cite this item you are advised to consult the publisher's version. Please see the 'permanent WRAP url' above for details on accessing the published version and note that access may require a subscription. ABSTRACT: The methanol-to-hydrocarbon (MTH) reaction received considerable attention as utilizing renewable sources of both value-added chemicals and fuels becomes number one priority for the society. Here, for the first time we report the development of hierarchical zeolites (ZSM-5) containing both iron oxide and nickel oxide nanoparticles. Modifying the iron oxide (magnetite, Fe3O4) amounts, we are able to control the catalyst activity and the product distribution in the MTH process. At the medium Fe3O4 loading, the major fraction is composed of the C9-C11 hydrocarbons (gasoline fraction). At the higher Fe3O4 loading, the C1-C4 hydrocarbons prevail in the reaction mixture, while at the lowest magnetite loading the major component is the C5-C8 hydrocarbons. Addition of Ni species to Fe3O4-ZSM-5 leads to the formation of mixed Ni oxides (NiO/Ni2O3) positioned either on top or next to Fe3O4 nanoparticles. This modification allowed us to significantly improve the catalyst stability due to diminishing coke formation and disordering of the coke formed. The incorporation of Ni oxide species also leads to a higher catalyst activity (up to 9.3 g(Methanol)/(g(ZSM-5)×h) and an improved selectivity (11.3% of the C5-C8 hydrocarbons and 23.6% of the C9-C11 hydrocarbons), making these zeolites highly promising for industrial applications.

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“…Regarding the degree of complexity reached by the real catalytic systems (either at the industrial scale or the laboratory scale), it is often mandatory to go beyond the ideal surface approach at low coverage. This is particularly true when defects cannot be described by specific cleavage orientations of the bulk materials, such as for low-coordinated sites of nano-aggregates, extra-framework species or vacancies, [52][53][54][55][56][57][58][59][60][61][62] and when they dominate the surface reactivity of solids. It is also mandatory to address the complexity of the system for supported catalysts when support effects are suspected to influence directly or indirectly the reactivity.…”

Section: Introductionmentioning

confidence: 99%

Density functional theory simulations of complex catalytic materials in reactive environments: beyond the ideal surface at low coverage

Chizallet

Raybaud

2014

Catal. Sci. Technol.

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Most efficient heterogeneous catalysts used industrially are generally very complex systems. Far away from perfect crystallinity and well-defined oriented surfaces at low coverage, they involve structural disorder, heterogeneous site distribution with variable coordination and structural dependence upon the chemical environment. Unravelling their atomic-scale structures and understanding their roles in the catalytic reaction are not easy tasks, as the respective contributions of each type of site to the spectroscopic or catalytic responses are generally convoluted. Computational chemistry is of great help to address these issues. In the present perspective review, we highlight two relevant systems involved in numerous industrial applications: the amorphous silica alumina support; and subnanometric platinum clusters, possibly doped with tin and/or indium, supported on γ-Al 2 O 3 . The structural complexity is inherent to the amorphous nature of an oxide support on the one hand, and to the ultra-dispersed form of a mono-and multi-metallic catalyst on the other hand. In each case, Density Functional Theory (DFT) calculation was used to provide an original structure for active sites and to reveal how the corresponding multi-step reactions are influenced. Moreover, we highlight how theoretical studies including coverage effects on complex systems, induced by (T, P) reaction conditions, offer enriched perspectives with respect to studies on ideal surfaces at low coverage.

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On the Role of Oxygen Defects in the Catalytic Performance of Zinc Oxide

Cited by 246 publications

References 45 publications

Selective isolation of the electron or hole in photocatalysis: ZnO–TiO2 and TiO2–ZnO core–shell structured heterojunction nanofibers via electrospinning and atomic layer deposition

Selective isolation of the electron or hole in photocatalysis: ZnO–TiO2 and TiO2–ZnO core–shell structured heterojunction nanofibers via electrospinning and atomic layer deposition

Metal oxide–zeolite composites in transformation of methanol to hydrocarbons: do iron oxide and nickel oxide matter?

Density functional theory simulations of complex catalytic materials in reactive environments: beyond the ideal surface at low coverage

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