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

Bergbreiter, Andreas; Hoster, Harry E.; Behm, R. Jürgen

doi:10.1002/cphc.201001087

Cited by 19 publications

(13 citation statements)

References 74 publications

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“…In Pt/Ru(0001), as in many other systems, surface alloys are actually thermodynamically more stable than the island morphologies [29,120,166]. This can be experimentally demonstrated by burying them under an additionally evaporated layer of substrate metal (here: Ru).…”

Section: Foreign Metal Islands and Surface Alloys: Ensemble Effects Amentioning

confidence: 98%

“…Due to its high activity in low temperature fuel cell anodes for the oxidation of CO contaminated H 2 or the direct electrochemical oxidation of methanol, the metal combination Pt+Ru has attracted tremendous research activity over the last decades. Apart from the electrochemistry community [113][114][115][116][117], also the Surface Science community was significantly involved [8,19,22,34,[118][119][120][121][122][123][124][125].…”

Section: Strain and Vertical Ligand Effects In Experiments And Theorymentioning

confidence: 99%

“…This can be experimentally demonstrated by burying them under an additionally evaporated layer of substrate metal (here: Ru). If the overgrown surface alloy is annealed again, it will float back to the surface [120]. In a simplified picture, this is driven by a lower surface energy of the guest as compared to the host metal atoms.…”

Section: Foreign Metal Islands and Surface Alloys: Ensemble Effects Amentioning

confidence: 99%

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Ultrahigh vacuum and electrocatalysis – The powers of quantitative surface imaging

Mercer

Hoster

2016

Nano Energy

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We highlight the impact of Ultrahigh Vacuum (UHV)-born surface science on modern electrocatalysis. The microscopic, atomic level picture of surface adsorption and reaction, which was developed in the surface science community in decades of systematic research on single crystals in UHV, has meanwhile become state-of-the-art also in electrochemistry. For the example of CO on Pt(111) single crystals, which has been extensively studied at the solid/gas and the solid/liquid interface using atomic resolution scanning tunnelling microscopy (STM), we highlight how both interfaces may have even more in common than often assumed. We then illustrate how planar model surfaces such as mono-and bimetallic single crystals and surface alloys, prepared and thoroughly analysed in UHV, enabled a systematic search for improved electrocatalysts. Surface alloys, thermodynamically more stable than foreign metal islands, are a particularly important subgroup of model surfaces, which so far have only been fabricated in UHV. We also flag that model surfaces may not always assume the structure anticipated for the respective experiment, regardless of their preparation in UHV or by electrochemical methods. "Accidental" surface alloying may be more common than often assumed, leading to misinterpretations of the structure-property relationships targeted in many model studies. We highlight that controlled surface alloy formation should be a key step in any model study looking at bimetallic systems in order to get an idea what the effect of unintended alloying could possibly be, and to cross-check whether alloyed surfaces may potentially be the better electrocatalysts in the first place.

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Section: Foreign Metal Islands and Surface Alloys: Ensemble Effects Amentioning

confidence: 98%

Section: Strain and Vertical Ligand Effects In Experiments And Theorymentioning

confidence: 99%

Section: Foreign Metal Islands and Surface Alloys: Ensemble Effects Amentioning

confidence: 99%

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Ultrahigh vacuum and electrocatalysis – The powers of quantitative surface imaging

Mercer

Hoster

2016

Nano Energy

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“…17 The segregation of Pd-Pt systems has been studied in vacuum, and in the presence of adsorbed H 2 , O 2 , OOH, and O. [25][26][27] For core-shell PtPd system, a 38-atom truncated octahedron was chosen as a model for bimetallic nanoparticles. Those 4 results show that there is minimal change in surface composition under different gaseous conditions, which was also experimentally observed.…”

Section: Introductionmentioning

confidence: 99%

A Pathway for the Growth of Core–Shell Pt–Pd Nanoparticles

Narula

Yang

et al. 2015

J. Phys. Chem. C

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The aging of both Pt-Pd nanoparticles and core-shell Pt-Pd nanoparticles has been reported to result in alloying of Pt with Pd. In comparison to monometallic Pt catalysts, the growth of Pd-Pt bimetallics is slower; however, the mechanism of growth of particles and the mechanism by which Pd improves the hydrothermal durability of bimetallic Pd-Pt particles remains uncertain. In our work on hydrothermal aging of core-shell Pt-Pd nanoparticles, synthesized by solution methods, with varying Pd:Pt ratio of 1:4, 1:1, and 4:1, we compare the growth of core-shell Pt-Pd nanoparticles and find that particles grow by migrating and joining together. The unique feature of the observed growth is that Pd shells from both particles open up and join, thereby allowing the cores to merge. At high temperatures, alloying occurs in good agreement with reports by other workers.

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“…Due to its high activity in low temperature fuel cell anodes for the oxidation of CO contaminated H 2 or the direct electrochemical oxidation of methanol the metal combination Pt+Ru continuously was subject of research over the last decades. Apart from the electrochemistry community [4][5][6][7][8], also the Surface Science community was significantly involved [9][10][11][12][13][14][15][16][17][18][19][20].…”

Section: Introductionmentioning

confidence: 99%

Direct observation of local chemical surface properties by scanning tunneling microscopy

Hoster¹

2012

AIP Conference Proceedings

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Vapor deposited Pt films with a thickness locally varying between one and two atomic layers on Ru(0001) are studied as model surfaces with a well-defined lateral variation of the chemical properties. These are probed by reversible CO adsorption at 300 K and with CO pressures in the range p CO =10-10 …10-5 mbar under real-time STM observation. Upon exposure to 10-5 mbar CO, no densely packed adlayer is formed on the areas with a local thickness of one atomic layer, whereas a c(4u2) adlayer containing 0.5 CO molecules per surface atom is reversibly formed on areas with locally two atomic layers of Pt. Based on experimental and theoretical data points and parameters from the literature we calculate adsorption isotherms for Pt(111) and the two Ru(0001) supported Pt thin films at 300 K. For all three surfaces, STM observations on CO adsorption are found to be fully consistent with the respective isotherms.

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

Cited by 19 publications

References 74 publications

Ultrahigh vacuum and electrocatalysis – The powers of quantitative surface imaging

Ultrahigh vacuum and electrocatalysis – The powers of quantitative surface imaging

A Pathway for the Growth of Core–Shell Pt–Pd Nanoparticles

Direct observation of local chemical surface properties by scanning tunneling microscopy

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