Water adsorption on stoichiometric and defective SnO2(110) surfaces

Gercher, Victoria A.; Cox, David F.

doi:10.1016/0039-6028(95)90028-4

Cited by 98 publications

(84 citation statements)

References 25 publications

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“…On MgO(100) [343] and α-Fe 2 O 3 (0001) [136,349], water was found to dissociate both on regular and defective surfaces and a correlation between the defect concentration and amount of dissociative adsorption was found. On other oxides, the role of defects for the dissociative adsorption is not clear, because water dissociation occurs both on ordered and defective surfaces with a similar rates, as on V 2 O 3 (047) [135], TiO 2 (110) [355], TiO 2 (001) [356] and SnO 2 (110) [350]. These studies suggest that defect sites can mostly dissociate water, in agreement with many studies performed on polycrystalline oxide materials [3].…”

Section: Discussionsupporting

confidence: 79%

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

Weiß

Ranke

2002

Progress in Surface Science

584

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: Discussionsupporting

confidence: 79%

“…Water adsorption studies on metal-oxide surfaces were initiated by work on its photocatalytic decomposition on TiO 2 [348], followed by investigations on other oxides and ionic compounds [5,338,349,350]. Molecular adsorption mostly occurs via the lone-pair of the O atom to an acidic surface site [58].…”

Section: Discussionmentioning

confidence: 99%

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

Weiß

Ranke

2002

Progress in Surface Science

584

610

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“…In the TDS experiments referred to in the Introduction [10,13], the high temperature features at 435 K (SnO 2 ) and 375 K (TiO 2 ) were attributed to desorption from the dissociated state.…”

Section: Discussionmentioning

confidence: 99%

“…Recent experiments by Gercher and Cox [13] using a combination of TDS and UPS show the presence of dissociatively adsorbed water on SnO 2 (110). On the perfect stoichiometric surface, three distinct TDS peaks are seen at T = 200, 300 and 435 K. The 200 K peak is attributed entirely and the 300 K peak mainly to molecular H 2 O.…”

Section: Introductionmentioning

confidence: 99%

The adsorption of H2O on TiO2 and SnO2(110) studied by first-principles calculations

1996

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First-principles calculations based on density functional theory and the pseudopotential method have been used to investigate the energetics of H 2 O adsorption on the (110) surface of TiO 2 and SnO 2 . Full relaxation of all atomic positions is performed on slab systems with periodic boundary conditions, and the cases of full and half coverage are studied. Both molecular and dissociative (H 2 O → OH − + H + ) adsorption are treated, and allowance is made for relaxation of the adsorbed species to unsymmetrical configurations. It is found that for both TiO 2 and SnO 2 an unsymmetrical dissociated configuration is the most stable. The symmetrical molecularly adsorbed configuration is unstable with respect to lowering of symmetry, and is separated from the fully dissociated configuration by at most a very small energy barrier. The calculated dissociative adsorption energies for TiO 2 and SnO 2 are in reasonable agreement with the results of thermal desorption experiments. Calculated total and local electronic densities of states for dissociatively and molecularly adsorbed configurations are presented and their relation with experimental UPS spectra is discussed.

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“…The first species labeled γ saturates at 225 K with d/l e =0.43±0.03 and exhibits two broad peaks. We attribute them to the 1π and 3σ orbitals of OH δ--species formed by dissociation of water into OH δ-+H δ+ 48 , as observed on many other metal oxide surfaces [49][50][51][52][53][54] . The work function decreases by 0.75 eV, indicating that OH δ-species are adsorbed with the oxygen atom oriented towards the surface.…”

Section: Active Sites For Water Chemisorptionmentioning

confidence: 99%

Structure and reactivity of iron oxide surfaces

Shaikhutdinov¹,

Joseph²,

Kuhrs³

et al. 1999

Faraday Disc.

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Epitaxial films of different iron oxide phases and of potassium iron oxide were grown onto Pt(111) substrates and used for studying structure-reactivity correlations. The film morphologies and their atomic surface structures were characterized by scanning tunneling microscopy and low energy electron diffraction including multiple scattering calculations. The adsorption of water, ethylbenzene, and styrene was investigated by temperature programmed desorption and photoelectron spectroscopy. A dissociative chemisorption of water and a molecular chemisorption of ethylbenzene and styrene is observed on all oxides that expose metal cations in their topmost layers, whereas purely oxygen terminated FeO(111) monolayer films are chemically inert and only physisorption occurs. Regarding the technical styrene synthesis reaction which is performed over iron oxide based catalysts, we find a decreasing chemisorption strength of the reaction product molecule styrene if compared to ethylbenzene when going from Fe 3 O 4 (111) over α-Fe 2 O 3 (0001) to KFe x O y (111). Extrapolation of the adsorbate coverages to the technical styrene synthesis reaction conditions using the Langmuir isotherm for coadsorption suggests an increasing catalytic activity along the same direction. This result agrees with previous kinetic experiments performed at elevated gas pressures over the model systems studied here and over polycrystalline iron oxide catalyst samples. It indicates that the iron oxide surface chemistry does not change across the pressure-gap and that the model systems simulate technical styrene synthesis catalysts in a realistic way.

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Water adsorption on stoichiometric and defective SnO2(110) surfaces

Cited by 98 publications

References 25 publications

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

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

The adsorption of H2O on TiO2 and SnO2(110) studied by first-principles calculations

Structure and reactivity of iron oxide surfaces

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