A structural study of a C3H3 species coadsorbed with CO on Pd(111)

Knight, Matthew John; Allegretti, Francesco; Kröger, Emily Alice; Polčík, Martin; Lamont, Christine L. A.; Woodruff, D.P.

doi:10.1016/j.susc.2008.06.038

Cited by 10 publications

(18 citation statements)

References 28 publications

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“…3B) using equations adapted from Stöhr and Outka (31), we determined that the CO axis lies within 21.4°± 7.0°of the surface normal. Previous C K-edge NEXAFS measurements of CO on the native Pd(111) surface reveal an upright bonding orientation (29). We attribute the discrepancy in the CO bond angle measured from the single crystal in ref.…”

Section: Resultsmentioning

confidence: 68%

“…Notice that in all our proposed models [and those by Rose et al (25)] CO is assumed to bond with its molecular axis more or less normal to the (111) top facet, as has been observed on native Pd(111) (29). By using X-ray photoemission electron microscopy (XPEEM), we tested this assumption through nearedge X-ray absorption fine structure (NEXAFS) measurements of a single nanoparticle, to our knowledge the first occasion that such a measurement has been reported.…”

Section: Resultsmentioning

confidence: 81%

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Influence of support morphology on the bonding of molecules to nanoparticles

Yim

Pang

Hermoso

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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Supported metal nanoparticles form the basis of heterogeneous catalysts. Above a certain nanoparticle size, it is generally assumed that adsorbates bond in an identical fashion as on a semiinfinite crystal. This assumption has allowed the database on metal single crystals accumulated over the past 40 years to be used to model heterogeneous catalysts. Using a surface science approach to CO adsorption on supported Pd nanoparticles, we show that this assumption may be flawed. Near-edge X-ray absorption fine structure measurements, isolated to one nanoparticle, show that CO bonds upright on the nanoparticle top facets as expected from single-crystal data. However, the CO lateral registry differs from the single crystal. Our calculations indicate that this is caused by the strain on the nanoparticle, induced by carpet growth across the substrate step edges. This strain also weakens the COmetal bond, which will reduce the energy barrier for catalytic reactions, including CO oxidation.nanoparticle | carpet growth | surface strain | adsorption | scanning tunneling microscopy N anoparticles exhibit properties distinct from their bulk counterparts (1-3). For instance, semiconductor particles smaller than ∼10 nm act as quantum dots (1-4) and oxide-supported gold nanoparticles are active for a variety of reactions including CO oxidation (5), water-gas-shift reaction (6), and epoxidation (7), whereas gold itself is not. Nanoclusters composed of ∼10 atoms have been shown to be exceptionally catalytically active for some reactions on some metals (8, 9). When the particle size is reduced, the relative number of undercoordinated atoms at the edges and corners increases. The proportion of perimeter sites at the interface between the metal and the support also increases. All these sites have been shown to play a crucial role in some reactions (10, 11). Reducing the particle size can also lead to a decrease in the interatomic bond length in small metal clusters (12, 13), which in the case of Pd nanoparticles results in lower adsorption energies for both CO (14,15) and O 2 (16), although such weakening of CO binding on the nanoparticle can also arise from other factors such as encapsulation of the nanoparticles by the support (17).The role of the support in modifying nanoparticle properties has also been recognized. For instance, the strong metal support interaction has been known for some time (2) and charge transfer either to or from the nanoparticles can lead to enhanced reactivity (18). More recently, it has come to light that the particle size itself may be governed by the interaction with the support (19). However, one effect that has not been discussed and yet should be present in any nanoparticle-support system is the influence of the support morphology such as steps.Here, we investigate the role of the support morphology on the reactivity of metal nanoparticles using scanning tunneling microscopy (STM). As our test system we choose Pd nanoparticles (20, 21) supported on TiO 2 (110) (22) simply because much is known about bo...

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Section: Resultsmentioning

confidence: 68%

Section: Resultsmentioning

confidence: 81%

Influence of support morphology on the bonding of molecules to nanoparticles

Yim

Pang

Hermoso

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

show abstract

“…The incident light is set to be p-polarized, hence b = 0°T op Catal (2016) 59:708-724 713 (111) top facet contributes most to the total X-ray absorption signal and hence the corresponding I versus h curve (open circles) exhibits a strong dependence on h and reaches an intensity offset of 0.082 at h = 0°. Apart from the non-zero intensity offset at h = 0°, this curve resembles that from CO on a Pd(111) single crystal where CO bonds upright on the surface [27]. As R TS decreases, the I versus h curve has a descending intensity at normal incidence and drops at a slower rate with decreasing h. However, when R TS \ 0.29, the I versus h curve (open rhombus) starts to develop a different character: rather than decreasing monotonically, the curve now has a breakpoint at h = 55°, below which it increases to reach a higher intensity value at h = 0°.…”

Section: Relative Size Of the Top Facetmentioning

confidence: 84%

“…5b. For a particle with a large R TS value of 7.9, CO on the (111) top facet contributes most to the total X-ray absorption signal and hence the corresponding I versus h curve (open-circles) resembles that from CO on a Pd(111) single crystal surface [27]. As R TS decreases, while still retaining the same essential character, the I versus h curve exhibits a diminishing dependence on h so that for a particle with R TS = 0.14 (at which the particle has 84 % of its surface atoms in the side facets), the corresponding I versus h curve (crosses) is almost invariant with h.…”

Section: Relative Size Of the Top Facetmentioning

confidence: 99%

Simulation of Near Edge X-ray Absorption Fine Structure (NEXAFS) Measurements of CO on Supported Pd Nanoparticles

2016

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Near edge X-ray absorption fine structure (NEXAFS) measurements of CO on Pd nanoparticles have been simulated. This was achieved by calculating the CO p* resonance signal of CO on a nanoparticle both as a function of the angle of incidence (I vs h) and the direction of the electric field vector E of the incident photon beam (I vs b), with the nanoparticle defined as a 111 ð Þ top facet with 111 f g and 100 f g side facets. The dependence of the p* resonance intensity signal of CO covered nanoparticles on the particle geometry and orientation as well as the bond orientation of CO is examined. In addition, we compare our simulations to a set of C K-edge NEXAFS experimental data obtained from a single Pd nanoparticle decorated with CO. Our simulation predicts that the nanoparticle has a high lateral aspect ratio of 37.7 ± 4.1.

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“…He also performed DFT calculations on furan adsorbed on Pd(1 1 1) and for C 3 H 3 on Pd(1 1 1) [134,136]. Woodruff's group has recently studied this system using photoelectron diffraction, near edge x-ray adsorption fine structure, and DFT [137][138][139][140].…”

Section: Furan Decomposition On Pd(1 1 1)mentioning

confidence: 99%

Imaging atoms and molecules on surfaces by scanning tunnelling microscopy

Chiang¹

2011

J. Phys. D: Appl. Phys.

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This review discusses nearly 30 years of scanning tunnelling microscopy (STM) work on high resolution imaging of numerous materials systems, giving a historical perspective on the field through the author's work. After a brief discussion of early STM and atomic force microscope (AFM) instrumentation development, the review discusses high resolution STM imaging on semiconductors, metals on semiconductors, Au(1 1 1), metal on metals including surface alloys, oxygen on metals, molecules adsorbed on metals, and AFM measurements of friction on graphite and mica.

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A structural study of a C3H3 species coadsorbed with CO on Pd(111)

Cited by 10 publications

References 28 publications

Influence of support morphology on the bonding of molecules to nanoparticles

Influence of support morphology on the bonding of molecules to nanoparticles

Simulation of Near Edge X-ray Absorption Fine Structure (NEXAFS) Measurements of CO on Supported Pd Nanoparticles

Imaging atoms and molecules on surfaces by scanning tunnelling microscopy

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