Structure, defects, and impurities at the rutile TiO2(011)-(2×1) surface: A scanning tunneling microscopy study

Dulub, Olga; Valentin, Cristiana Di; Selloni, Annabella; Diebold, Ulrike

doi:10.1016/j.susc.2006.06.042

Cited by 62 publications

(88 citation statements)

References 74 publications

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“…In 2004, a first structure model was suggested by Beck et al [49,50] who postulated a missing-row reconstruction and the formation of one-fold-coordinated oxygen leading to titanyl (Ti = O) groups which were believed to account for the peculiar photocatalytic activity of the (011) orientation. A subsequent extensive STM study by Dulub et al [77] confirmed the conclusions and provided additional information about defects and impurities on the (011) surface. First-principles calculations (T = 0 K) of the energetics and structure of stoichiometric TiO 2 surfaces were communicated by Ramamoorthy et al [59] and revealed that the (011) surface should be more corrugated than the (110) surface and dominated by five-fold coordinated Ti atoms.…”

Section: (011)-oriented Rutile Thin Filmsmentioning

confidence: 73%

Model Studies on CO Oxidation Catalyst Systems: Titania and Gold Nanoparticles

et al. 2010

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The peculiar catalytic activity of Au-supported titanium dioxide surfaces in the CO oxidation reaction has been a focus of interest for more than twenty years. Herein, recent data concerning preparation and structural characterisation of planar catalyst model systems consisting of single-crystalline titania and/or gold nanoparticles deposited thereon is presented and reviewed. We first expand on the deposition and growth of TiO(2) films on selected metal host surfaces and then consider the deposition of Au nanoparticles on these surfaces, including information on their geometric and electronic structures. The second issue is the interaction of these materials with carbon monoxide (one of the essential ingredients of the CO oxidation reaction) which serves as a probe molecule and monitor of the chemical activity of the model catalyst samples. Concerted efforts relating the structural and chemical properties of the respective binary materials (titania support plus deposited gold) can help to tackle and finally resolve the still open problems concerning the high activity of Au-TiO(2) catalysts in the CO oxidation reaction.

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Section: (011)-oriented Rutile Thin Filmsmentioning

confidence: 73%

Model Studies on CO Oxidation Catalyst Systems: Titania and Gold Nanoparticles

et al. 2010

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“…The rutile TiO 2 (101) surface in grown films and single crystals also possess a (1x2) reconstruction [34,35]. In analogy to a model for this rutile TiO 2 (101)-(1x2) surface [35,36] {110} and {100} facets. Our SEM results show that the precalcined RuO 2 crystals indeed exhibit {101} facets, which however must be completely inactive in CO oxidation.…”

Section: Ruo 2 As Bulk Phasementioning

confidence: 99%

On the CO-Oxidation over Oxygenated Ruthenium

Rosenthal¹,

Girgsdies

Timpe

et al. 2009

Zeitschrift Für Physikalische Chemie

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The oxidation of carbon monoxide over polycrystalline ruthenium dioxide (RuO 2 ) powder was studied in a packed-bed reactor and by bulk and surface analytical methods. Activity data were correlated with bulk phases in an in-situ X-ray diffraction (XRD) setup at atmospheric pressure. Ruthenium dioxide was pre-calcined in pure oxygen at 1073 K. At this stage RuO 2 is completely inactive in the oxidation of CO. After a long induction period in the feed at 503 K RuO 2 becomes active with 100% conversion, while in-situ XRD reveals no changes in the RuO 2 diffraction pattern. At this stage selective roughening of apical RuO 2 facets was observed by scanning electron microscopy (SEM). Seldom also single lateral facets are roughened. EDX indicated higher oxygen content in the following order: flat lateral facets > rough lateral facets > rough apical facets. Further, experiments in the packed bed reactor indicated oscillations in the CO 2 formation rate. At even higher temperatures in reducing feed (533-543 K) the sample reduces to ruthenium metal according to XRD. The reduced particles exhibiting lower ignition temperature are very rough with cracks and deep star-shaped holes. An Arrhenius plot of the CO 2 formation rate below the ignition temperature reveals the reduced samples to be significantly more active based on mass unit and shows lower apparent activation energy than the activated oxidized sample. Micro-spot X-ray photoelectron spectroscopy (XPS) and XPS microscopy experiments were carried out on a Ru(0001) single crystal exposed to oxygen at different temperature. Although low energy electron diffraction (LEED) images show a strong 1x1 pattern, the XPS data indicated a wide lateral inhomogeneity with different degree of oxygen dissolved in the subsurface layers. All these and the literature data are discussed in the context of different active states and transport issues, and the metastable nature of a phase mixture under conditions of high catalytic activity.

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“…In one report, the photo-induced oxidative and reductive half-reactions were observed to take place predominantly on the (0 1 1) and (1 1 0) surfaces of well-faceted TiO 2 microcrystals, respectively [11]. The need to understand such phenomena and the dearth of information on rutile (0 1 1) as compared to other TiO 2 surfaces has recently stimulated several surface science studies on single crystal TiO 2 (0 1 1) [13][14][15][16][17][18].…”

Section: Introductionmentioning

confidence: 99%

“…1b). From STM and photoemission experiments, it was established that (i) bombardment of TiO 2 (0 1 1)-2 Â 1 with electrons desorbs surface oxygen atoms and results in missing bright spots [16], (ii) water adsorbs in a mixed molecular/dissociated form at low temperatures, and the molecular water desorbs around 200 K [14,15], (iii) hydroxyls (formed via dissociation of water from the residual gas on O vacancies) are apparent as bright spots on bright zig-zag rows [15,17] and (iv) adsorbates such as formic acid adsorb in between the bright rows [13].…”

Section: Introductionmentioning

confidence: 99%