Encapsulation and electronic effects in a thin-film model of a rhodium-titania catalyst

Belton, David N.; Sun, Yufan; White, J. M.

doi:10.1021/ja00322a066

Cited by 55 publications

(22 citation statements)

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“…The depth profiles, taken with Auger electron spectroscopy (AES) and Ar+ bombardment at 500 eV after HTR at 673 K and also after annealing in A c c e p t e d M a n u s c r i p t vacuum revealed support material on top of the rhodium layer. Similar results were obtained with model systems consisting of platinum or rhodium, evaporated on a this TiO 2 layer on Ti(0001) single crystals [28][29][30][31][32]. After HTR at 775 K, the hydrogen chemisorption capacity was reduced and SIMS and AES revealed a titanium species on top of the metal (Pt or Rh).…”

Section: Titania As Support Materialssupporting

confidence: 75%

Strong metal–support interactions on rhodium model catalysts

Linsmeier

Taglauer

2011

Applied Catalysis A: General

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Reactive processes on catalyst surfaces are studied in this work for Rh/metal oxide model systems by means of surface science techniques. Published results in the literature deal with titania, alumina, and silica as support materials and are briefly reviewed. For the present studies Rh/Al 2 O 3 and Rh/TiO 2 model catalysts with about one monolayer Rh coverage are specially prepared and analyzed by ion scattering spectroscopy, X-ray photoelectron spectroscopy, and thermal desorption measurements as main techniques. In part these measurements are supported by a variety of other analytical and imaging techniques. For thermal treatment in hydrogen atmosphere at low and elevated pressures a complete Rh encapsulation by titania is observed for temperatures above 773 K. The results from ion bombardment depth profiling are corroborated by the concomitant drastic reduction of the CO adsorption capacity of these samples. The model catalysts thus exhibit the typical features of 'strong metal-support interaction'. The effect was not found for alumina supports, for which thermal treatments mainly resulted in gradual interdiffusion of the various surface species. These results also demonstrate that characteristic catalyst behavior can be successfully studied by applying surface science methods to model catalysts.

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Section: Titania As Support Materialssupporting

confidence: 75%

Strong metal–support interactions on rhodium model catalysts

Linsmeier

Taglauer

2011

Applied Catalysis A: General

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“…[2] In the development of this subject, titania as a support has played a central role, because the metal-support interactions have been among the strongest observed-this support even migrates after high-temperature treatments to envelope metal particles on it. [3,4] Much of the recent research on titania has been focused on its photocatalytic properties and its potential for use in catalytic photo-splitting of water and oxidation of organic compounds. Numerous investigations have focused on photo-generation of defect sites [5] and radical species [6,7] on titania surfaces, because they have been implicated in catalysis by titania subjected to UV radiation.…”

Section: Introductionmentioning

confidence: 99%

“…[HRe(CO) 5 ] and [CH 3 Re(CO) 5 ], were used to probe surface sites of TiO 2 (anatase). These complexes were adsorbed from the gas phase onto anatase powder that had been treated in flowing O 2 or under vacuum to vary the density of surface OH sites.…”

Section: Introductionmentioning

confidence: 99%

Probing Surface Sites of TiO₂: Reactions with [HRe(CO)₅] and [CH₃Re(CO)₅]

Lobo‐Lapidus

Gates

2010

Chemistry A European J

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Two carbonyl complexes of rhenium, [HRe(CO)(5)] and [CH(3)Re(CO)(5)], were used to probe surface sites of TiO(2) (anatase). These complexes were adsorbed from the gas phase onto anatase powder that had been treated in flowing O(2) or under vacuum to vary the density of surface OH sites. Infrared (IR) spectra demonstrate the variation in the number of sites, including Ti(+3)-OH and Ti(+4)-OH. IR and extended X-ray absorption fine structure (EXAFS) spectra show that chemisorption of the rhenium complexes led to their decarbonylation, with formation of surface-bound rhenium tricarbonyls, when [HRe(CO)(5)] was adsorbed, or rhenium tetracarbonyls, when [CH(3)Re(CO)(5)] was adsorbed. These reactions were accompanied by the formation of water and surface carbonates and removal of terminal hydroxyl groups associated with Ti(+3) and Ti(+4) ions on the anatase. Data characterizing the samples after adsorption of [HRe(CO)(5)] or [CH(3)Re(CO)(5)] determined a ranking of the reactivity of the surface OH sites, with the Ti(+3)-OH groups being the more reactive towards the rhenium complexes but the less likely to be dehydroxylated. The two rhenium pentacarbonyl probes provided complementary information, suggesting that the carbonate species originate from carbonyl ligands initially bonded to the rhenium and from hydroxyl groups of the titania surface, with the reaction leading to the formation of water and bridging hydroxyl groups on the titania. The results illustrate the value of using a family of organometallic complexes as probes of oxide surface sites.

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“…Model catalyst studies (mostly transition metals on titania) conducted after 1981 have convincingly demonstrated that SMSI involves, perhaps not exclusively, encapsulation of the active metal 19,10,[20][21][22].…”

Section: Introductionmentioning

confidence: 99%

“…Our previous work demonstrated that encapsulation suppresses hydrogen and carbon monoxide chemisorption, and that restor-ation occurred when the encapsulating layer was removed [22].…”

Section: Introductionmentioning

confidence: 99%

Chemisorption of CO, NO, and H2 on transition metal-titania thin film model catalysts*1

Belton¹

1986

Journal of Catalysis

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Encapsulation and electronic effects in a thin-film model of a rhodium-titania catalyst

Cited by 55 publications

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Strong metal–support interactions on rhodium model catalysts

Strong metal–support interactions on rhodium model catalysts

Probing Surface Sites of TiO₂: Reactions with [HRe(CO)₅] and [CH₃Re(CO)₅]

Chemisorption of CO, NO, and H2 on transition metal-titania thin film model catalysts*1

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Encapsulation and electronic effects in a thin-film model of a rhodium-titania catalyst

Cited by 55 publications

References 0 publications

Strong metal–support interactions on rhodium model catalysts

Strong metal–support interactions on rhodium model catalysts

Probing Surface Sites of TiO2: Reactions with [HRe(CO)5] and [CH3Re(CO)5]

Chemisorption of CO, NO, and H2 on transition metal-titania thin film model catalysts*1

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Probing Surface Sites of TiO₂: Reactions with [HRe(CO)₅] and [CH₃Re(CO)₅]