Adsorption of hydrogen on the polar O–ZnO surface: a molecular beam study

Kunat, M.; Burghaus, U.; Wöll, Christof

doi:10.1039/b307955d

Cited by 34 publications

(37 citation statements)

References 48 publications

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“…Therefore, in the Zn-polar case, accumulation of metallic zinc at the surface acts as a self-inhibitor for the reaction, explaining the self-saturation profiles in Figure 2. This instability in hydrogen of Zn-polar (0001) ZnO is also consistent with the reports of Becker et al [36] Conversely, on the O-polar (000À1) surface, which shows a natural affinity for H atoms, these can adsorb on the O sites only (upon exposure to atomic hydrogen, a H(1 Â 1) of a hydroxilated HO-ZnO surface has been reported [37] ). The -OH-terminated O-polar (000À1) surface becomes more stable by adsorbing H atoms, [38] as also predicted by total-energy calculations, [39] explaining its unreactivity.…”

supporting

confidence: 88%

Is There a ZnO Face Stable to Atomic Hydrogen?

et al. 2009

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The interaction of atomic hydrogen with ZnO depends on ZnO polarity. O‐polar (000−1) ZnO is stable to atomic hydrogen; Zn‐polar (0001) ZnO is partially attacked by atomic hydrogen, affording a self‐inhibiting reaction that enriches the surface in metallic Zn; nonpolar (11−20) ZnO is completely etched by atomic hydrogen; and the nonpolar (10−10) ZnO is roughened during interaction with atomic hydrogen.

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confidence: 88%

Is There a ZnO Face Stable to Atomic Hydrogen?

et al. 2009

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“…Unconstrained geometry optimization starting from the suspected (Bowker et al 1981), 77.90 (Kunat et al 2003) energy minimum structure has confirmed this finding and allowed us to refine the intermediate structure that comprises a hydrogen atom floating over the VOISS, which is in turn occupied by a hydride ion. The electron initially trapped at the VOISS is now localized on the floating hydrogen atom, which, on dissociation of the H 2 molecule, returns to the 'high' position, about 3 Å above the surface.…”

Section: (C) Reaction Path For Hydrogen Dissociationmentioning

confidence: 67%

“…Both preparation and operation of the catalyst include its hydrogenation as an important step (Waugh 1992;French et al 2001aFrench et al , 2003b. The complex atomistic processes involved in sorption, reaction and then desorption of hydrogen from ZnO have captured the interest of both experimentalists and theoreticians (Taylor & Sickman 1932;Taylor & Strother 1934;Taylor & Liang 1947;Kubokawa & Toyama 1954;Low 1959Low , 1965Kubokawa 1960;Eischens et al 1962;Nagarjunan et al 1963;Peshev 1966;Dent & Kokes 1969;Morrison 1969;Narayana et al 1970a,b;Baraski & Galuszka 1976;Boccuzzi et al 1978;Watanabe 1978;Bowker et al 1981;Griffin & Yates 1982;Maslov et al 1982;Denisenko et al 1983;Roberts & Griffin 1986, 1988Burch et al 1990;Idriss & Barteau 1992;Waugh 1992;Ghiotti et al 1993;Nyberg et al 1996;Gines et al 1997;Mitra et al 1998;Lu et al 1999;Spencer 1999;Zapol et al 1999;Scarano et al 2001;Kazanskii & Pid'ko 2002;Kunat et al 2003;Rozovskii & Lin 2003;…”

Section: Hydrogen Dissociation Over Oxygen Terminated Polar Surface Omentioning

confidence: 99%

Characterization of hydrogen dissociation over aluminium-doped zinc oxide using an efficient massively parallel framework for QM/MM calculations

et al. 2011

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A task-farm parallelization framework has been implemented in the ChemShell computational chemistry environment to provide a facility for parallelizing common chemical calculations, including finite-difference Hessian evaluation, the nudged elastic band method for reaction path optimization, and population-based methods for global optimization. The optimization methods are provided by a parallel interface to the DL-FIND optimization library. As ChemShell can already exploit parallel external programs for energy and gradient evaluations, the new methods result in a two-level approach to parallelization that gives significantly improved performance for massively parallel calculations. For typical systems, speed-up factors of five to eight times have been observed compared with non-task-farmed calculations. The task-farming version of ChemShell has been used to study the heterolytic dissociation of a hydrogen molecule over a polar oxygen-terminated surface of aluminium-doped zinc oxide using an embedded cluster hybrid QM/MM approach. We calculate a 42 kcal mol −1 heat of reaction and a 30 kcal mol −1 activation energy, which is equivalent to a high backward reaction barrier of 72 kcal mol −1 per H 2 molecule, in close agreement with temperature programmed desorption experiments. The dissociation path includes a stable intermediate comprising a hydride ion in an oxygen vacancy and physisorbed atomic hydrogen.

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Section: Introductionmentioning

confidence: 99%

“…It has been shown that Ni(111) exposed to H at under UHV condition can form bulk hydrogen species, which show a unique catalytic activity towards hydrogenation of hydrocarbons [7]. H atoms were also reported to readily adsorb on the ZnO(0001) surface [8,9].Here we present a surface science study on the interaction of atomic hydrogen with iron oxides. We observe an autocatalytically accelerated partial reduction of the oxides.…”

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confidence: 99%

Autocatalytic partial reduction of FeO(111) and Fe3O4(111) films by atomic hydrogen

Huang

Ranke

2006

Surface Science

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The interaction of atomic hydrogen with thin epitaxial FeO(111) and Fe3O4(111) films was studied by TDS, XPS and LEED. On the thin, one Fe-O bilayer thick FeO film, partial reduction occurs in two steps during exposure. It ends after removal of ¼ monolayer (ML) of oxygen with a 2´2 pattern appearing in LEED. This FeO0.75 film is passive against further reduction. The first reduction step saturates after removal of ~0.2 ML and shows autocatalytic kinetics with the oxygen vacancies formed during reduction causing acceleration. The second step is also autocatalytic and is related with reduction to the final composition and an improvement of the 2´2 order. A structure model explaining the two-step reduction is proposed. On the thick Fe3O4 film, irregular desorption bursts of H2O and H2 were observed during exposure. Their occurrence appears to depend on the film quality and thus on surface order. Because of the healing of reduction-induced oxygen vacancies by exchange of oxygen or iron with the bulk, a change of the surface composition was not visible. The existence of partially reduced oxide phases resistant even to atomic hydrogen is relevant to the mechanism of dehydrogenation reactions using iron oxides as catalysts.Key words: Low energy electron diffraction, X-ray photoelectron spectroscopy, temperature programmed desorption, catalysis, surface chemical reaction, hydrogen atom, iron oxide IntroductionIron oxides, widespread in nature, are of interest to many scientific disciplines from geology to biology [1]. The reduction of iron oxides is inevitable in many processes, such as metallurgy, corrosion, and heterogeneous catalysis. It was long found that the very rapid dissolution of the passive iron oxides film on iron involves a reductive mechanism [2]. The surface reduction, together with coke formation, is responsible for the deactivation of the iron oxide-based catalyst for the dehydrogenation of ethylbenzene to styrene [3,4]. Because of their relevance for corrosion processes, the reduction of iron oxides in solution has been extensively studied and a clear understanding of the mechanism and kinetics is acquired [5]. However, fundamental understanding of of iron oxide reduction by gas phase hydrogen is poor.Most fundamental understanding of the gas-solid interactions comes from surface science studies of relevant model systems under ultra-high-vacuum (UHV) conditions. Very little is known about the interaction of hydrogen with well-characterized single-crystal iron oxides. The nearly stoichiometric, well ordered a-Fe 2 O 3 (0001) surface is inert towards molecular hydrogen at room temperature and interaction occurs only at defects [6]. Thus it is difficult to approach the reduction of iron oxides by employing molecular hydrogen. The reason is, of course, the high dissociation energy of H 2 (432 kJ/mol). Atomically adsorbed hydrogen, OH groups or protons are formed in catalytic dehydrogenation reactions or during electrochemical reduction. Therefore it makes sense to study the interaction of surfaces...

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Adsorption of hydrogen on the polar O–ZnO surface: a molecular beam study

Cited by 34 publications

References 48 publications

Is There a ZnO Face Stable to Atomic Hydrogen?

Is There a ZnO Face Stable to Atomic Hydrogen?

Characterization of hydrogen dissociation over aluminium-doped zinc oxide using an efficient massively parallel framework for QM/MM calculations

Autocatalytic partial reduction of FeO(111) and Fe3O4(111) films by atomic hydrogen

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