Rotationally resolved spectroscopy of Pt2

Airola, Marc B.; Morse, Michael D.

doi:10.1063/1.1428753

Cited by 86 publications

(55 citation statements)

References 51 publications

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“…The experimental value for the Pt 2 equilibrium bond length, 233.3 pm, [38] is in reasonable agreement with the B3LYP/cc-pwCVDZ-PP value of 220.4 pm. The calculated Pt-Pt vibrational frequency, 265.3 cm…”

Section: Methodssupporting

confidence: 69%

Chemical State of Adsorbed Sulfur on Pt Nanoparticles

Park

Atienza

et al. 2011

ChemPhysChem

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Adsorption of sulfur (S)-containing molecules on Pt has attracted much interest in heterogeneous catalysis in general, and in electrocatalysis in particular, because of its widely observed strong negative effect on catalytic activity. It is generally believed that the PtÀS bond is predominantly covalent and the adsorbed S (S ads ) induces a significant depletion in the d-electron population of Pt.[1] The S ads on Pt can act as a site-blocking species and/or modify the band structure of the metal resulting in a significant decrease in the reactivity of the Pt surface toward small molecules (e.g. CO, H 2 , C 2 H 4 ).[2] While the effect of the former is usually very localized, that of the latter can be long range. For instance, the adsorption of hydrogen (H) is totally inhibited by S ads before full-monolayer coverage of S ads is reached. The estimated numbers (N S ) of H adsorption sites blocked by one S atom at very low S coverage are 12 AE 3 for Pt (110) and 10 AE 1 for Pt (111), although the corresponding saturation coverages (q s ) are 0.8 and 0.62, respectively. [3,4] In contrast, a much lower N S (~2 to 3) was reported on polycrystalline Pt, indicating that the influence of the PtÀS bond is sensitive to the surface structure. [5,6] Recent studies have also shown that S ads on carbon-supported Pt (Pt/C) nanoparticles (NPs) substantially impedes the oxygen reduction reaction (ORR) and hydrogen oxidation reaction (HOR). [7,8] In particular, the S ads enhanced the formation of the deleterious H 2 O 2 by-product during the ORR. On the other hand, S ads has also been shown to enhance the activity of Pt as a site-modifier in formic acid, formaldehyde and methanol electro-oxidation. [9][10][11][12] Multiple mechanisms have been proposed for the enhancement including the entropy effect, [9] the chemical state of S ads [11] and the reduction effect. [12] A similar enhancement was also observed by a partial anodic stripping of the S ads layer and attributed to a transformation of the S adsorption structure.[9] Furthermore, the structure of the S ads , deposited from a liquid S-containing solution, was investigated by determining the anodic charges associated with the S electro-oxidation (S-EO) process. Although monomeric S, [4,[13][14][15] diatomic S [8-10, 16, 17] and polymeric (or multilayer) S [6,18,19] structures on Pt electrodes have been proposed, no consensus has been reached on the exact chemical state of adsorbed S.It is clear that in order to understand the chemistry behind these unclear and sometimes contradictory observations, unambiguous identification of the chemical state of the S ads is highly desirable. Herein we report a detailed electrochemical (EC) study of S adsorption on commercial carbon-supported Pt (Pt/C) and Pt black (Pt-B) NPs as a function of the S coverage substantiated by in situ surface enhanced Raman spectroscopy (SERS) and density functional theory (DFT) calculations of related model molecules. The NP sizes in Pt/C and Pt-B were about 4 nm and 7 nm respectively. The S coverage was cont...

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Section: Methodssupporting

confidence: 69%

Chemical State of Adsorbed Sulfur on Pt Nanoparticles

Park

Atienza

et al. 2011

ChemPhysChem

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“…39 For the ground state of Pt 2 , we find r e = 2.442 Å and D e = 3.10 eV compared to experimental r 0 = 2.33297 Å and D e = 3.14Ϯ 0.02 eV. 49 Similarly In the XAS calculations, the ͑core-excited͒ oxygen of the central water molecule in the cluster models was described using the IGLO-III all-electron basis set of Kutzelnigg et al; 52 all other oxygen atoms were described using an ECP ͑Ref. 53͒ as in previous reports; 26,33 this eliminates their O 1s level and leads to the O 1s level of the target molecule being unique and nondegenerate ensuring in a very simple way convergence to the desired core hole state.…”

Section: Methodsmentioning

confidence: 98%

The role of substrate electrons in the wetting of a metal surface

Schiros

Takahashi

Andersson

et al. 2010

The Journal of Chemical Physics

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We address how the electronic and geometric structures of metal surfaces determine water-metal bonding by affecting the balance between Pauli repulsion and electrostatic attraction. We show how the rigid d-electrons and the softer s-electrons utilize different mechanisms for the redistribution of charge that enables surface wetting. On open d-shell Pt͑111͒, the ligand field of water alters the distribution of metal d-electrons to reduce the repulsion. The closed-shell Cu d 10 configuration of isostructural Cu͑111͒, however, does not afford this mechanism, resulting in a hydrophobic surface and three-dimensional ice cluster formation. On the geometrically corrugated Cu͑110͒ surface, however, charge depletion involving the mobile sp-electrons at atomic rows reduces the exchange repulsion sufficiently such that formation of a two-dimensional wetting layer is still favored in spite of the d 10 electronic configuration.

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“…Introduction.-In the last two decades many spectroscopic studies of diatomic transition metals of the 3d and 4d periods have been published (see [1] and references therein). Through this work the basic electronic structure of the homometallic and heterometallic 3d and 4d dimers has been discerned and a qualitative understanding of many of these molecules has been established.…”

mentioning

confidence: 99%