Direct spectroscopic observation of the reactive catalytic site for CO oxidation on Pt(335)

Xu, Jian; Henriksen, P. N.; Yates, John T.

doi:10.1063/1.463825

Cited by 65 publications

(69 citation statements)

References 20 publications

(1 reference statement)

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“…One of the advantages of IRRAS is its ability to sensitively discriminate between adsorbates on different adsorption sites, i.e., steps and terraces, making it a powerful technique for catalyst surface characterization and in situ investigation of the nature and structure of the active sites [25][26][27]. It was found that CO adsorbed on terraces is more reactive than CO adsorbed on steps [24].…”

Section: Co Electrooxidation On Ptmentioning

confidence: 99%

Mechanisms of Carbon Monoxide and Methanol Oxidation at Single-crystal Electrodes

et al. 2007

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The electrochemical oxidation of carbon monoxide and methanol on single-crystal noble metal electrodes has been studied using cyclic voltammetry, chronoamperometry, in situ FTIR spectroscopy, online electrochemical mass spectrometry, and theoretical methods. The oxidation of CO was found to be enhanced by steps and defects. Furthermore, the surface diffusion rate was found to have a significant influence on the kinetics of the oxidation process: for high diffusion rates, such as the oxidation of CO on platinum, the kinetics can be described by a mean field model, while for low diffusion rates, such as CO oxidation on rhodium in sulfuric acid, a nucleationand-growth model was found to be more suitable. Voltammetric and mass spectrometric measurements on the oxidation of methanol on platinum indicate that steps enhance the overall reaction rate. In general, the selectivity towards the direct oxidation pathway through soluble intermediates was found to be higher in the absence of strongly adsorbing anions. In both perchloric and sulfuric acid, this selectivity was also found to increase with increasing step density. In sulfuric acid, Pt(111) shows the highest relative contribution for the direct pathway of all surfaces studied in that electrolyte. Based on these results, a detailed reaction scheme for the electrochemical oxidation of methanol is presented.

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Section: Co Electrooxidation On Ptmentioning

confidence: 99%

Mechanisms of Carbon Monoxide and Methanol Oxidation at Single-crystal Electrodes

et al. 2007

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“…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%

“…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%

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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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“…Following studies that employed low index Pt surface planes [14], techniques were extended to the stepped Pt(s)-[4(111) x (100)] surface [15]. The saturation coverage for CO on a Pt(s)-[4(111) x (100)] electrode was determined for the first time and found to be consistent with expectations based on ultra high vacuum surface science experiments on the system [19][20][21]. Our study also included the first kinetic measurements of sub-saturation coverage CO monolayer oxidation.…”

Section: Abstract Progress Report and Future Directionsmentioning

confidence: 59%

Strategies for Probing Nanometer-Scale Electrocatalysts: From Single Particles to Catalyst-Membrane Architectures

Korzeniewski

2014

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Objectives Abstract, Progress Report and Future Directions A. Fuel Cell Membrane and Catalyst-Membrane Architectures Probed by VibrationalSpectroscopy: Infrared and Raman spectroscopy were investigated as probes of structures within proton conductive materials that limit or enhance performance in polymer electrolyte fuel cells. The following were primary accomplishments: (a) least squares modeling in conjunction with infrared spectroscopy was demonstrated as a useful approach to detect differences in the response of hydrophilic and more hydrophobic functional groups in ionomer materials undergoing changes in hydration state [1]; (b) strategies developed during the project through studies of model Nafion membranes [2][3][4] were adapted to investigate new bis(perfluoroalkylsulfonyl) imide [5] and fluoroalkyl phosphonate [6] ionomer materials; (c) the capabilities of Raman spectroscopy were explored for its potential to enable depth profiling of practical fuel cell membrane and in situ studies of fuel cell catalyst-membrane architectures.

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Direct spectroscopic observation of the reactive catalytic site for CO oxidation on Pt(335)

Cited by 65 publications

References 20 publications

Mechanisms of Carbon Monoxide and Methanol Oxidation at Single-crystal Electrodes

Mechanisms of Carbon Monoxide and Methanol Oxidation at Single-crystal Electrodes

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

Strategies for Probing Nanometer-Scale Electrocatalysts: From Single Particles to Catalyst-Membrane Architectures

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