Interaction of CO with atomically well-defined Pt Ru /Ru(0 0 0 1) surface alloys

Rauscher, Hubert; Häger, Tobias; Diemant, Thomas; Hoster, Harry E.; Mongeot, F. Buatier de; Behm, R. J.

doi:10.1016/j.susc.2007.07.019

Cited by 41 publications

(106 citation statements)

References 40 publications

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“…After annealing to 1300 K, Pt and Ru surface atoms are finally homogeneously distributed in the resulting surface alloy. [6,13,14,16] In summary, the annealing experiments confirm previous findings about the morphological changes of Pt islands on Ru(0001) upon annealing to T > 600 K. [16,20] For T ! 850 K, these morphological changes are accompanied by exchange processes between Pt adatoms and embedded Ru surface atoms, that is, the onset of surface alloy formation.…”

Section: à2supporting

confidence: 87%

“…lower than typical values for a saturated CO layer on Pt(111). [33,34] Additionally, it should be noted that, similar to results of other IR studies of CO adsorption on Pt ML / Ru(0001), [13,21] we did not detect any features related to CO adsorbed on bridge or hollow sites. After CO saturation, the IR spectrum is dominated by the band related to CO adsorption on the Pt islands (2089 cm…”

supporting

confidence: 89%

“…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%

“…In a first-order approximation, the modification of the adsorption properties of both CO and D observed for PtRu/Ru(0001) relative to adsorption on Ru(0001) or on Pt(111) can also be explained in the above framework. [13,17,19,22] For a pseudomorphic Pt layer on the Ru substrate, the lattice mismatch between the two components of the bimetallic sample (Pt: 2.77 , Ru: 2.70 ) results in electronic strain effects. Furthermore, the interaction between the Ru(0001) substrate and the Pt cover layer also modifies the electronic structure and hence the chemical properties of the Pt cover layer (vertical electronic ligand effect).…”

Section: Discussionmentioning

confidence: 99%

“…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%

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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: à2supporting

confidence: 87%

supporting

confidence: 89%

Section: Introductionmentioning

confidence: 78%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

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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Synthesis and Characterization of Three‐Dimensional Porous Cu@Pt and Cu@Pt‐Ru Catalysts for Methanol Oxidation

2017

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Highly porous Cu foams comprised of interconnected branched dendrites were used as sacrificial templates for the fabrication of pseudo core–shell Cu@Pt and Cu@Pt‐Ru unsupported electrodes by galvanic replacement. The as‐prepared materials presented a three‐dimensional structure with pores between 17 and 45 μm made of superimposed layers of ramified dendrites. TEM analysis showed that the dendrites were composed of agglomerates of grains of about 4 nm in size and mesopores of ca. 30 nm in diameter. The as‐prepared 3D electrodes were tested for methanol oxidation in acid media at different temperatures. The results showed that the catalytic activities of Cu@Pt and Cu@Pt‐Ru foams normalized to the electrochemical surface area are almost 50 % higher than that of a commercial Pt−Ru/C material, with poisoning rates that are reduced by half in the same potential range. The enhanced behavior of the as‐prepared foams is believed to be the result of the influence of copper atoms on the reactivity of platinum sites, the highly defective structure of the electrodes, as well as the facilitated diffusion of methanol molecules and the products formed during the reaction throughout the highly porous three‐dimensional structure of the electrode. The apparent activation energies (Ea,app) for the methanol oxidation reaction (MOR) were determined by potentiostatic experiments. Ea,app values of 29.07 and 24.20 kJ mol−1 were calculated for Cu@Pt and Cu@Pt‐Ru foams at 0.3 V, respectively. The results suggested that the MOR is governed by the dissociative adsorption of methanol as a result of the multifunctional nature of the catalyst and the facilitated diffusion of the products formed during the reaction.

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Interaction of CO with atomically well-defined Pt Ru /Ru(0 0 0 1) surface alloys

Cited by 41 publications

References 40 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

Synthesis and Characterization of Three‐Dimensional Porous Cu@Pt and Cu@Pt‐Ru Catalysts for Methanol Oxidation

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