CO on Pt(335) and Pt(111): Vibrational stark effect and electron energy loss investigation

Luo, J.S.; Tobin, R. G.; Lambert, David K.; Wagner, Frederick T.; Moylan, Thomas E.

doi:10.1016/0368-2048(90)80239-7

Cited by 18 publications

(5 citation statements)

References 25 publications

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“…When the fractional CO surface coverage reaches about 40%, Avd shows a steep increase, reaching a value of about 38 cm-1 at 65%, after which it remains nearly constant out to saturation coverages. It is notable that the coverage dependence of Avd displayed in Figure 5 tracks the major coverage dependent adlayer structural transitions that have been 10 observed for this system [3][4][5][6][8][9][10][11][12][13]. For example, Avd is small at low coverages, where exclusive edge-site adsorption occurs, but begins to increase as terrace sites become occupied.…”

Section: Mixed Isotope Experiments On Saturated Co Adlayersmentioning

confidence: 53%

“…Several recent papers in this area have reported on site-dependent phenomena at Pt(335) (Pt-(S)-[4(l 11) x (100)]) [3][4][5][6][7][8][9][10][11][12][13][14][15][16]. This surface was originally used to support infrared spectroscopic studies of carbon monoxide (CO) adsorption at defect sites on small platinum catalyst particles [13,14], and it has since become a model substrate for vibrational studies of site-dependent adsorption processes.…”

Section: Introductionmentioning

confidence: 99%

“…The earliest experiments defined conditions for observing independent vibrational spectral features for molecules on Pt(335) step edges (edge-CO) and for molecules on Pt(335) terrace planes (terrace-CO) [12,13]. Subsequent investigations have used this knowledge to explore aspects of sitedependent interfacial phenomena, such as electric field inhomogeneities at surface defects [5,8,10,11,16], site-specific CO oxidation [6,9] and molecular interactions at stepped monocrystalline electrode surfaces [3,4].…”

Section: Introductionmentioning

confidence: 99%

“…A notable property of Pt(335)/CO is that the CO occupancy at step and terrace sites is determined by the surface coverage, as CO preferentially binds sites on the step edge, and begins to occupy terrace sites only after the edge sites fill [3][4][5][6][8][9][10][11][12][13]. At low coverages, vibrational features for edge-CO are observed, whereas at intermediate and high…”

Section: Introductionmentioning

confidence: 99%

“…For species in 2 terminal coordination environments, the intensity of the lower energy edge-CO feature diminishes with increasing CO surface coverage, as the terrace sites fill. These intensity alterations occur on account of strong intermolecular interactions between edge-and terrace-CO molecules, and several vibrational spectroscopic studies of Pt(335)/CO have observed the effect [3][4][5][6][8][9][10][11][12][13].…”

Section: Introductionmentioning

confidence: 99%

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Site-dependent vibrational coupling of CO adsorbates on well-defined step and terrace sites of monocrystalline platinum: Mixed-isotope studies at Pt(335) and Pt(111) in the aqueous electrochemical environment

Kim

Tornquist

Korzeniewski

1994

The Journal of Chemical Physics

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Infrared spectroscopy is applied to probe qualitative structural features of the adlayers formed by CO at step sites and on terrace planes of Pt(335){Pt(S)-[4(111)×(100)]} in the aqueous electrochemical environment. The C–O stretching vibrational features are reported for adlayers formed from 12CO/13CO isotopic mixtures over a wide range of CO surface coverages. At saturation, the predominant spectral features are associated with the vibrational modes of terrace-CO in terminal (atop) coordination environments. The position of the 12CO and 13CO spectral features and their relative intensity are examined for several 12CO/13CO fractions, and they are shown to display the characteristics of a strongly coupled system. In comparison with corresponding mixed isotope spectra for CO at Pt(111) electrodes, intermolecular coupling for terrace-CO on the (111) surface planes of Pt(335) is observed to be significantly stronger, reflecting the higher CO surface coverages on the edge sites and the terrace sites of the Pt(335) surface plane. At low coverages, spectral features associated with edge-CO are discerned, and the intermolecular coupling for atop CO is weaker than for corresponding coverages of CO at Pt(111). The weak coupling at low coverages is attributed to the exclusive CO occupation at the step edges, which confines the intermolecular coupling to one dimension, in the direction along the step edges. For all coverages, values are determined for the dynamic dipole–dipole coupling parameter (Δνd) and the chemical (static–dipole) shift parameter (Δνs). Values for Δνs are generally small at all coverages. Values for Δνd are small (<8 cm−1) at low coverages, where CO forms one-dimensional structures along the step edges, and they increase to large values (∼42 cm−1) at coverages that coincide with the growth of two-dimensional structures on the terrace planes. The majority of measurements were made for the Pt(335) electrode at potentials in the classical double-layer region, although dipole coupling parameters are also reported for Pt(335)/CO at potentials in the hydrogen adsorption region, where Δνd approaches zero at low coverages.

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