The chemisorption of carbon monoxide on palladium single crystal surfaces: IR spectroscopic evidence for localised site adsorption

Bradshaw, A. M.; Hoffmann, F. M.

doi:10.1016/0039-6028(78)90367-9

Cited by 667 publications

(228 citation statements)

References 47 publications

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“…Frequencies of the bands due to adsorbed CO on Pd(111) are strongly correlated with adsorbed CO coverage, θ. [36][37][38] For example, a band is located at 1936 cm −1 for θ = 0.5, at which the c(4 × 2) ordered structure was formed. Based on the C-O stretching frequency, the 1930 cm −1 band can be ascribed to bridge-bonded CO on Pd(111).…”

Section: Resultsmentioning

confidence: 99%

“…The IRRAS spectrum of the clean Pt(111) is characterized by two distinct bands at 2095 and 1853 cm −1 , which can reliably be assigned to adsorbed CO on the on-top and bridge sites of surface Pt atoms, respectively. 36,39 The IRRAS spectrum of Pt 0.6nm /Pd(111) shows linear-and bridgebonded CO bands at 2097 cm −1 and 1857 cm −1 , respectively. These frequencies are slightly higher than those for the clean Pt(111); slight blue shifts might arise from the influence of the Pd(111) substrate on the topmost Pt(111) epitaxial layers.…”

Section: Resultsmentioning

confidence: 99%

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Electrochemical Properties of Pt Epitaxial Layers Formed on Pd(111) in Ultra-High Vacuum

Bando

Takahashi

Todoroki

et al. 2015

J. Electrochem. Soc.

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Electrocatalytic properties for oxygen reduction reaction (ORR) of Pt(111) epitaxial layers on a Pd(111) substrate are investigated. Scanning tunneling microscopy images of the as-prepared 0.6-nm-and 1.2-nm-thick Pt(111) epitaxial layers on Pd(111) (Pt 0.6nm /Pd(111) and Pt 1.2nm /Pd(111)) revealed that the topmost surface has atomically flat, 50-100-nm-wide terraces. Remarkable current features due to hydrogen storage and emission by the Pd(111) substrate dominated the cyclic voltammograms of Pt 0.6nm /Pd(111) in the potential range of 0.15-0.4 V vs. a reversible hydrogen electrode. In contrast, the curve of Pt 1.2nm /Pd(111) exhibited a shrinkage in the hydrogen charges (Q H ) in the potential range of 0.25-0.4 V, accompanied by the emergence of symmetrical redox features at 15 mV on the positive potential side, relative to Pt(111) "butterfly" feature. Both Pt 0.6nm /Pd(111) and Pt 1.2nm /Pd(111) showed ca. four times higher ORR activity than clean Pt(111), although their hydrogen-related behaviors and activity changes during applying potential cycles were much different. The results suggest that shrinkage in Q H and positive shift in the onset potential of hydroxyl species are common features of the CV of highly ORR-active well-defined Pt-M(111) bimetallic surfaces and that the activity enhancements and the structural stabilities fairly depend on the surface structure of the epitaxial Pt (111) High-performance low-cost polymer electrolyte membrane fuel cells (PEMFC) are required for wide-spread use in fuel cell vehicles. Developments in highly active oxygen reduction reaction (ORR) catalysts are one of the top priorities for developing PEMFC stacks. Since the pioneering work on Pt-M (M is a more affordable, lowcost material) alloys by Watanabe and co-workers, 1 numerous studies on the ORR properties of Pt-M bimetallic alloy with nanosized structures have been intensively performed. To date, several types of nanosized structures of Pt-M have been proposed for use as highperformance ORR catalysts, e.g., Pt-shell and M-core core-shell nanoparticles (NPs), 2-5 especially electrochemically de-alloyed M from Pt-M NPs, 6-9 nanostructured thin films of Pt-M, 10,11 shapecontrolled Pt-M NPs, [12][13][14][15] and nanoframe structures of Pt-Ni alloy. 16Irrespective of the proposed nature of the nanosized structures, the generation of electrochemically stable Pt-shell layers at the topmost surfaces is the consensus for synthesizing Pt-M ORR catalysts with high activity and durability. 17-20The topmost atomic-level structures of the Pt-shell layers for the Pt-M bimetallic alloys determine ORR performance. However, because ORR is governed by many factors, the discussions of ORR enhancement mechanisms are intricate. For example, atomic arrangements of the topmost Pt-shell, thickness of the Pt-shell layers, and interface structures between the surface Pt-shell and underlying M (Pt-M) core [21][22][23][24] are expected to have a serious influence on the ORR activities. When studying the topmost surface structures and the eval...

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Electrochemical Properties of Pt Epitaxial Layers Formed on Pd(111) in Ultra-High Vacuum

Bando

Takahashi

Todoroki

et al. 2015

J. Electrochem. Soc.

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“…Gas-phase A g and B 1u irreducible representations in D 2h correlate with A 1 in C 2v symmetry [28]. Only modes of A 1 symmetry are active in RAIRS [29] so that, in principle, ethylene adsorbed with C 2v symmetry should exhibit four peaks.…”

Section: Discussionmentioning

confidence: 99%

Ethylene adsorption on Pd( 111 ) studied using infrared reflection–absorption spectroscopy

2002

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The adsorption of ethylene has been studied on clean and hydrogen-covered Pd(1 1 1) using reflection-absorption infrared spectroscopy and molecular beam methods. Using a correlation diagram, in which vibrational frequencies are plotted versus a rp parameter proposed by Stuve and Madix, shows that ethylene is substantially rehybridized on Pd(1 1 1) having a rp parameter intermediate between those of ethylene on Ni(1 1 1) and Ru(0 0 1). In contrast, when ethylene adsorbs on hydrogen-covered Pd(1 1 1), only p-bonded species are detected. An additional species appears exhibiting a characteristic frequency of 957 cm À1 when Pd(1 1 1) is cooled to $80 K and the system pressurized with $10 À5 Torr of ethylene. This species also appears on a CO-saturated Pd(1 1 1) surface. Molecular beam measurements show that its coverage reaches $1.3 ML indicating that it is due to ethylene adsorbed in the second and subsequent layers. Ó

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“…At about half a monolayer, an ordered structure forms and there is a drastic decrease in the heat of adsorption. Infrared spectroscopy studies suggest that the decreased heat of adsorption in this ordered structure is due both to dipole-dipole interactions between adjacent CO's and a shift in the adsoption site on the surface from 3-fold hollow to 2-fold bridge [52]. -18-The further decrease in the heat of adsorption at higher coverages may also be due to a combination of subtle changes in the bonding site and increased repulsive intereactions between adsorbates.…”

Section: Benzenementioning

confidence: 99%

Bonding and chemistry of hydrocarbon monolayers on metal surfaces

Bent

Somorjai

1989

Advances in Colloid and Interface Science

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The chemisorption of carbon monoxide on palladium single crystal surfaces: IR spectroscopic evidence for localised site adsorption

Cited by 667 publications

References 47 publications

Electrochemical Properties of Pt Epitaxial Layers Formed on Pd(111) in Ultra-High Vacuum

Electrochemical Properties of Pt Epitaxial Layers Formed on Pd(111) in Ultra-High Vacuum

Ethylene adsorption on Pd( 111 ) studied using infrared reflection–absorption spectroscopy

Bonding and chemistry of hydrocarbon monolayers on metal surfaces

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