Vibrational spectroscopy of CO used as a local probe to study the surface morphology of Pt on Ru() in the submonolayer regime

Schlapka, A.; Käsberger, U.; Menzel, D.; Jakob, Peter M.

doi:10.1016/s0039-6028(01)01909-4

Cited by 48 publications

(86 citation statements)

References 18 publications

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“…Temperature-programmed desorption (TPD) and infrared-reflection absorption spectroscopy (IRAS) measurements, using CO and D 2 as probe molecules, were applied to gain insight into the chemical properties of the resulting model surfaces. The information obtained from the study of these two probe molecules is complementary: while CO is adsorbed only in on-top sites on PtRu/Ru(0001) surfaces, [13,19,21,22] deuterium (hydrogen) atoms are assumed to occupy fcc threefold-hollow sites on the bimetallic surfaces, similar to findings for the close-packed surfaces of the two pure constituents Ru(0001) [23,24] and Pt(111) [25,26] . Therefore, the effect of a variation in the size of the adsorption ensemble on the adsorption behavior can be derived from a comparison of the CO and hydrogen adsorption properties at different surface compositions.…”

Section: Introductionmentioning

confidence: 78%

“…[6,16,20] With increasing temperature, the islands grow in size and are transformed to a compact shape after annealing to higher temperatures (~700 K). [6,16,19,20] The onset of surface alloy formation at the descending edges of vacancy islands in Pt monolayer films was observed after annealing to 850 K, [16] while surface alloy formation is completed after annealing to 1300 K. [13,16] Herein, we present the results of a combined STM and spectroscopic study on the correlation between structural variations in bimetallic PtRu/Ru(0001) surfaces during the surface alloy formation process and the corresponding modifications in their chemical properties. The surface structure and distribution of the components in the topmost layer was revealed by STM.…”

Section: Introductionmentioning

confidence: 98%

“…The structural properties of laterally equilibrated bimetallic PtRu/Ru(0001) surfaces were already studied in detail by STM. [6,13,14,16,[19][20][21] Pt deposition at room temperature (300 K) and subsequent heating to different temperatures (up to 1300 K) leads to a broad variation of the distribution of both components in the topmost layer. For Pt deposition at room temperature, dendritic Pt islands are formed on the Ru(0001) substrate.…”

Section: Introductionmentioning

confidence: 99%

“…[19] With increasing CO exposure, the first band shifts tõ 2020 cm À1 and is centered at 2049 cm À1 after CO saturation.…”

mentioning

confidence: 96%

“…[19] For a CO ad coverage of 0.01 ML, IR peaks detected at 2041 and 2047 cm À1 were associated with kink or step sites at the edges of the Pt islands, respectively. [19] CO adsorbed in the inner part of larger Pt islands produced a feature at 2085 cm À1 .…”

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confidence: 99%

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From Adlayer Islands to Surface Alloy: Structural and Chemical Changes on Bimetallic PtRu/Ru(0001) Surfaces

et al. 2010

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The correlation between structural and chemical properties of bimetallic PtRu/Ru(0001) model catalysts and their modification upon stepwise annealing of a submonolayer Pt‐covered Ru(0001) surface up to the formation of an equilibrated PtxRu1−x/Ru(0001) monolayer surface alloy was investigated by scanning tunneling microscopy and by the adsorption of CO and D2 probe molecules. Both temperature‐programmed desorption and IR measurements demonstrate the influence of the surface structure on the adsorption properties of the bimetallic surface, which can be explained by changes of the composition of the adsorption ensembles (ensemble effects) for D adsorption and by changes in the electronic interaction (ligand effects, strain effects) of the metallic constituents for CO and D adsorption upon alloy formation.

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Section: Introductionmentioning

confidence: 78%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

“…[19] With increasing CO exposure, the first band shifts tõ 2020 cm À1 and is centered at 2049 cm À1 after CO saturation.…”

mentioning

confidence: 96%

mentioning

confidence: 99%

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From Adlayer Islands to Surface Alloy: Structural and Chemical Changes on Bimetallic PtRu/Ru(0001) Surfaces

et al. 2010

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The Effect of Structurally Well‐Defined Pt Modification on the Electrochemical and Electrocatalytic Properties of Ru(0001) Electrodes

Hoster

Behm

2008

Fuel Cell Catalysis

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The effects of structurally well defined Pt modifications of Ru(0001) single crystal electrodes on their electrochemical behavior and their CO oxidation properties are identified and quantitatively related to the structural characteristics. Pure Ru(0001) and the bimetallic surfaces, including Ru(0001) surfaces covered by Pt monolayer islands, by a complete Pt monolayer or by monolayer PtRu surface alloys of varying composition, were prepared under ultrahigh vacuum (UHV) conditions and characterized quantitatively by high resolution scanning tunneling microscopy (STM). The electrochemical/-catalytic properties were determined under defined electrolyte flow conditions in an electrochemical flow cell attached to the UHV system. While on pure Ru(0001) the overlapping stability ranges of underpotential deposited hydrogen (H upd ) or CO ad on the one hand and OH ad /O ad on the other hand hinder the adsorption of the respective adsorbates, Pt promotes and catalyzes the potential dependent formation and removal of adlayers. Monolayer Pt islands and pure Pt or mixed Pt x Ru 1-x (x = 1,2) adsorption ensembles provide additional channels for the adsorption (H upd  OH ad exchange, CO ad  OH ad exchange) and reaction (CO oxidation) of the respective second adsorbate on the adsorbate covered Ru(0001) areas. Quantitative correlation between the surface atom distribution and the electrochemical characteristics shows that the uptake/desorption of H upd is correlated with the abundance of threefold coordinated Ru sites, while on mixed Ru n Pt 3-n sites, H upd and OH ad adsorption is much weaker and shifted to lower and higher potentials, respectively. For both types of model surfaces, the availability of Pt sites leads to a substantially higher activity for the electrooxidation of CO as compared to bare Ru(0001), with significant differences between the behavior of surface alloys and Pt island modified Ru(0001). The different effects contributing to the modified adsorption/reaction behavior and the relative contributions are identified and discussed comparing with results obtained on Ru and PtRu electrodes reported previously and on bimetallic PtRu surfaces under UHV conditions.

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Segregation and Stability in Surface Alloys: PdxRu1−x/Ru(0001) and PtxRu1−x/Ru(0001)

2011

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The stability of PdRu/Ru(0001) and PtRu/Ru(0001) surface alloys and the tendency for surface segregation of Pd and Pt subsurface guest metals in these surface alloys is studied by scanning tunneling microscopy (STM) and Auger electron spectroscopy (AES). Atomic resolution STM imaging and AES measurements reveal that upon overgrowing the surface alloys with a 1-2 monolayer Ru film and subsequent annealing to the temperatures required for initial surface alloy formation, the Ru-covered Pd (Pt) atoms float back to the outermost layer. The lateral distribution of these species is also essentially identical to that of the initial surface alloys, before overgrowth by Ru. In combination, this clearly demonstrates that the surface alloys represent stable surface configurations, metastable only towards entropically favored bulk dissolution, and that there is a distinct driving force for surface segregation of these species. Consequences of these data on the mechanism for surface alloy formation are discussed.

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Vibrational spectroscopy of CO used as a local probe to study the surface morphology of Pt on Ru() in the submonolayer regime

Cited by 48 publications

References 18 publications

From Adlayer Islands to Surface Alloy: Structural and Chemical Changes on Bimetallic PtRu/Ru(0001) Surfaces

From Adlayer Islands to Surface Alloy: Structural and Chemical Changes on Bimetallic PtRu/Ru(0001) Surfaces

The Effect of Structurally Well‐Defined Pt Modification on the Electrochemical and Electrocatalytic Properties of Ru(0001) Electrodes

Segregation and Stability in Surface Alloys: PdxRu1−x/Ru(0001) and PtxRu1−x/Ru(0001)

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