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Title: Vibrational properties of CO at the Pt(111)-solution interface:The Anomalous Stark-Tuning Slope

Authors:
; ; ; ;
Publication Date:
Research Org.:
Ernest Orlando Lawrence Berkeley NationalLaboratory, Berkeley, CA (US)
Sponsoring Org.:
USDOE Director. Office of Science. Office of AdvancedScientific Computing Research. Office of Basic Energy Sciences. MaterialsSciences and Engineering Division
OSTI Identifier:
894699
Report Number(s):
LBNL-53703
R&D Project: 517101; BnR: KC0203010
DOE Contract Number:
DE-AC02-05CH11231
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Physical Chemistry B; Journal Volume: 109; Related Information: Journal Publication Date: 2005
Country of Publication:
United States
Language:
English
Subject:
37

Citation Formats

Stamenkovic, V., Chou, K.C., Somorjai, G.A., Ross, P.N., and Markovic, N.M.. Vibrational properties of CO at the Pt(111)-solution interface:The Anomalous Stark-Tuning Slope. United States: N. p., 2005. Web. doi:10.1021/jp044802i.
Stamenkovic, V., Chou, K.C., Somorjai, G.A., Ross, P.N., & Markovic, N.M.. Vibrational properties of CO at the Pt(111)-solution interface:The Anomalous Stark-Tuning Slope. United States. doi:10.1021/jp044802i.
Stamenkovic, V., Chou, K.C., Somorjai, G.A., Ross, P.N., and Markovic, N.M.. Fri . "Vibrational properties of CO at the Pt(111)-solution interface:The Anomalous Stark-Tuning Slope". United States. doi:10.1021/jp044802i.
@article{osti_894699,
title = {Vibrational properties of CO at the Pt(111)-solution interface:The Anomalous Stark-Tuning Slope},
author = {Stamenkovic, V. and Chou, K.C. and Somorjai, G.A. and Ross, P.N. and Markovic, N.M.},
abstractNote = {},
doi = {10.1021/jp044802i},
journal = {Journal of Physical Chemistry B},
number = ,
volume = 109,
place = {United States},
year = {Fri Dec 23 00:00:00 EST 2005},
month = {Fri Dec 23 00:00:00 EST 2005}
}
  • Three experiments were designed to clarify the source of a surprising difference observed earlier between the vibrational Stark shift of two different atom C[double bond]O stretch modes, CO on the step edge and CO on the (111) terrace, on the stepped Pt(335) surface. The observed data of CO on Pt(335) cannot be explained by a difference in intramolecular structure between the two CO species-a chemical mechanism. The electron energy loss spectroscopy (EELS) measurements for CO on Pt(335) indicate that any such differences are too small to account for the data. An alternative, physical mechanism has to be responsible. The observedmore » Stark effect of CO on Pt(335) results from strong screening of the static field at terrace sites, even though no difference in the screening of the IR field is observed. The authors developed a model for the populations of four CO species versus coverage for CO on Pt(335), which plausibly accounts for our EELS and temperature programmed desorption data. Bridge-bonded CO is first observed on this highly stepped surface. The authors used reflection absorption infrared spectroscopy (RAIRS) and electroreflectance vibrational infrared spectroscopy (EVS) to confirm that the Stark shift of terrace CO on Pt(335) is significantly suppressed. The Stark shift of CO on Pt(111) is quite comparable to that of edge CO and is significantly bigger than that of terrace CO on Pt(335). In the same experiment, the authors observed that the screening effects for the IR field and the static field are fundamentally different. Most importantly, this result and the conclusion for CO on Pt(335) suggest that the present physical picture of electric field screening at surfaces is qualitatively wrong. The authors also found that our measured Stark shift of CO on Pt(111) in ultrahigh vacuum (UHV) is only one half that in electrochemical cells. Such a difference is possible related to extra screening of the static electric field in UHV.« less
  • Adsorption of CO on ultrathin Cu films supported on Pt(111) has been studied using infrared reflection absorption spectroscopy (IRAS). Our results indicate that the infrared intensities of adsorbed CO are not representative of the relative composition of the Cu{sub {lt}1.0}/Pt(111) surfaces. The Cu-bonded CO molecules screen CO molecules bonded to Pt, making them invisible in the infrared spectrum. The screening'' effect depends on the morphology and polarizability of the Cu overlayer. Changes in the morphology of the Cu adlayer produce large variations in the position and line shape of the Cu--CO signal in the infrared spectrum. CO molecules bonded tomore » small Cu clusters show a higher ({similar to}40 cm{sup {minus}1}) C--O stretch frequency than CO molecules adsorbed on large Cu islands. The present results were compared with those reported in the literature for the CO/Cu/Ru(0001) and CO/Cu/Rh(100) systems. For CO adsorbed on supported monolayers of Cu, a correlation was found between the strength of the Cu--CO bond, the amount of {pi} backdonation, and the C--O stretch frequency. This correlation cannot be explained using simple models of molecular orbital theory. On the bimetallic surfaces, the C--O stretch frequency is more sensitive to the charge on the metal center to which CO is bonded, than to the electron population of the CO(2{pi}) orbitals.« less
  • The vibrational spectrum of CO on Pt(111) was monitored over 13 orders of magnitude in CO pressure by using infrared-visible sum frequency generation. Surprising results at high pressures indicate a pressure-induced major reorganization of CO on Pt(111). At low pressures (10{sup {minus}10} Torr{endash}10{sup {minus}1} Torr) CO bonds at atop and bridge sites, but above 10 Torr new features appear, and by 700 Torr they dominate the spectrum. They suggest the presence of an incommensurate CO overlayer together with some terminally bound CO at atop defect sites. {copyright} {ital 1996 The American Physical Society.}
  • The adsorption of CO{sub 2} on K-dosed Pt(111) was studied by high-resolution electron energy loss and thermal desorption spectroscopy. Adsorption of CO{sub 2} produced measurable vibrational spectra at low K coverage ({theta}{sub K} = 0.05) as well as for a multilayer of K ({theta}{sub K} = 1.27). At a K coverage of {theta}{sub K} {approx} 0.49, intense losses were observed at 1600 {plus minus} 20, 1340 {plus minus} 20, and 820 {plus minus} 20 cm{sup {minus}1} tentatively attributed to the asymmetric stretching, symmetric stretching, and the bending modes of a bent CO{sub 2}{sup {minus}} species formed by the direct interactionmore » of metallic potassium and CO{sub 2}. CO{sub 2}{sup {minus}} may be stabilized in the form of a dimer or oxalate. Above 200 K, this surface species is transformed into carbonate and CO, which are characterized by loss features at 1440 {plus minus} 20 and 1600 {plus minus} 20 cm{sup {minus}1}, respectively. CO desorbs above 600 K (T{sub p} = 640 K), while carbonate decomposes above 650 K (T{sub p} = 674 and 790 K).« less