Structure of the Hydrated α-Al
            <sub>2</sub>
            O
            <sub>3</sub>
            (0001) Surface

Eng, Peter J.; Trainor, Thomas P.; Brown, Gordon E.; Waychunas, Glenn A.; Newville, Matthew; Sutton, S. R.; Rivers, Mark L.

doi:10.1126/science.288.5468.1029

Cited by 532 publications

(406 citation statements)

References 32 publications

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“…Also, in ISS H cannot be discriminated from the high background in the high-loss region. The outward relaxation found here (+10%) lies well within the range found for hydroxilated α-Al 2 O 3 (0001) [296][297][298][299] and α-Fe 2 O 3 (0001) [300] surfaces (+3 to +20%). Possibly, the bond of adjacent O atoms to the surface is weakened by such a OH nucleus, so that further O is removed and the OH island grows by further water adsorption as discussed by several authors (see discussion, Section 5.6.4).…”

Section: (Ii) Termination B After Oxidation In 10 -5 Mbar Osupporting

confidence: 64%

Surface chemistry and catalysis on well-defined epitaxial iron-oxide layers

Weiß

Ranke

2002

Progress in Surface Science

579

610

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Metal-oxide based catalysts are used for many important synthesis reactions in the chemical industry. A better understanding of the catalyst operation can be achieved by studying elemantary reaction steps on well-defined model catalyst systems. For the dehydrogenation of ethylbenzene to styrene in the presence of steam both unpromoted and potassium promoted iron-oxide catalysts are active. Here we review the work done over unpromoted single-crystalline FeO(111), Fe 3 O 4 (111) and α-Fe 2 O 3 (0001) films grown epitaxially on Pt(111) substrates. Their geometric and electronic surface structures were characterized by STM, LEED, electron microscopy and electron spectroscopic techniques. In an integrative approach, the interaction of water, ethylbenzene and styrene with these films was investigated mainly by thermal desorption and photoelectron emission spectroscopy. The adsorptiondesorption energetics and kinetics depend on the oxide surface terminations and are correlated to the electronic structures and acid-base properties of the corresponding oxide phases, which reveal insight into the nature of the active sites and into the catalytic function of semiconducting oxides in general. Catalytic studies, using a batch reactor arrangement at high gas pressures and post reaction surface analysis, showed that only α-Fe 2 O 3 (0001) containing surface defects is catalytically active, whereas Fe 3 O 4 (111) is always inactive. This can be related to the elementary adsorption and desorption properties observed in ultrahigh vacuum, which indicates that the surface chemical properties of the iron-oxide films do not change significantly across the "pressure-gap". A model is proposed according to which the active site involves a regular acidic surface sites and a defect site next to it. The results on metal-oxide surface chemistry also have implications for other fields, such as environmental science, biophysics and chemical sensors.-2 -"2kyEi9FYSQjBVrZxIPQ.FHIAC_WRa02_review.doc", Datum: 19.02.03

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Section: (Ii) Termination B After Oxidation In 10 -5 Mbar Osupporting

confidence: 64%

Surface chemistry and catalysis on well-defined epitaxial iron-oxide layers

Weiß

Ranke

2002

Progress in Surface Science

579

610

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“…(see Supporting Information for the AFM image) Sample preparation followed the recipe of Ref. [15,43,44]. The sample surface was first cleaned in a sonication bath of acetone, methanol, and pure water for 10, 10, and 60min, respectively, in sequence.…”

Section: Methodsmentioning

confidence: 99%

Surface Structure of Protonated R-Sapphire (11̅02) Studied by Sum-Frequency Vibrational Spectroscopy

et al. 2011

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Sum frequency vibrational spectroscopy was used to study the protonated R-plane (1102 ) sapphire surface. The OH stretch vibrational spectra show that the surface is terminated with three hydroxyl moieties, two from AlOH 2 and one from Al 2 OH functional groups. The observed polarization dependence allows determination of the orientations of the three OH species. The results suggest that the protonated sapphire (1102 ) surface differs from an ideal stoichimetric termination in a manner consistent with previous X-ray surface diffraction (crystal truncation rod) studies. However, in order to best explain the observed hydrogenbonding arrangement, surface oxygen spacing determined from the X-ray diffraction study requires modification.

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“…The structures and functionalities of aluminas with LASs on the surface have been studied in detail, and the strongest LASs were reported for three-, four-, or five-coordinated Al 3 + on the surface (Liu and Truitt 1997;Eng et al 2000;Fionov 2002). Our results indicate the important role of alumina LASs in propachlor transformation with dithionite.…”

Section: Discussionmentioning

confidence: 99%

“…Reactions at the mineral-water interface are an important topic in a variety of applications ranging from mineral beneficiation to contaminant detergency (Eng et al 2000). Aluminum is one of the most abundant metallic elements of the Earth's crust (8.1 % by the weight) (Greenwood and Earnshaw 1997).…”

Section: Introductionmentioning

confidence: 99%

Dechlorinating transformation of propachlor through nucleophilic substitution by dithionite on the surface of alumina

et al. 2012

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Purpose The aim of this study was to evaluate the roles of aluminum-based minerals, especially their surface Lewis acid sites (LASs), on the transformation and fate of chloroacetanilide herbicide contaminants when nucleophilic reagents are present. Materials and methods Batch experiments were used to study propachlor transformation processes under different reaction conditions. The surface bonding of aluminas before and after interacting with propachlor and dithionite were characterized by Fourier transform infrared (FTIR) spectra. The LASs on different aluminas, acting as the key role for accelerating the propachlor transformation, were analyzed by pyridine adsorption/FTIR spectroscopic technique. Results and discussion Rates of dithionite-initiated propachlor dechlorination were increased in the presence of aluminas. Transformation efficiencies of propachlor on different aluminas were found to be as γ-Al 2 O 3 >γ-AlOOH>α-Al 2 O 3 . A higher reaction temperature, higher pH, and higher alumina dosage can further increase the propachlor dechlorination rate.The addition of citric acid may block the active sites on alumina and reduce propachlor transformation by dithionite. FTIR and pyridine adsorption/diffuse reflectance Fourier transform infrared spectroscopy indicated that Al-S and Al-O bonds on the LASs of alumna play a key role in accelerating propachlor transformation. Conclusions LASs on alumina surfaces can effectively accelerate the propachlor transformation by dithionite. The strong electron accepting ability of LASs gives dithionite a favorable affinity to form surface sulfur compounds, which are stronger reductants and nucleophilic reagents for propachlor dechlorination. The intensities of LASs on alumina surfaces can be used to control the rate of propachlor transformation by dithionite.

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Structure of the Hydrated α-Al ₂ O ₃ (0001) Surface

Cited by 532 publications

References 32 publications

Surface chemistry and catalysis on well-defined epitaxial iron-oxide layers

Surface chemistry and catalysis on well-defined epitaxial iron-oxide layers

Surface Structure of Protonated R-Sapphire (11̅02) Studied by Sum-Frequency Vibrational Spectroscopy

Dechlorinating transformation of propachlor through nucleophilic substitution by dithionite on the surface of alumina

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Structure of the Hydrated α-Al 2 O 3 (0001) Surface

Cited by 532 publications

References 32 publications

Surface chemistry and catalysis on well-defined epitaxial iron-oxide layers

Surface chemistry and catalysis on well-defined epitaxial iron-oxide layers

Surface Structure of Protonated R-Sapphire (11̅02) Studied by Sum-Frequency Vibrational Spectroscopy

Dechlorinating transformation of propachlor through nucleophilic substitution by dithionite on the surface of alumina

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Structure of the Hydrated α-Al ₂ O ₃ (0001) Surface