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Changes in the surface structure of Pd/Ta 2 O 5 by oxygen and CO studied using X‐ray Photoelectron Spectroscopy (XPS)
Author(s) -
Seo Hyun Ook,
Lee Jaeyoung,
Kim KwangDae,
Luo Yuan,
Dey Nilay Kumar,
Kim Young Dok
Publication year - 2011
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/sia.3725
Subject(s) - x ray photoelectron spectroscopy , oxygen , oxide , chemistry , chemical state , substrate (aquarium) , binding energy , analytical chemistry (journal) , oxidation state , metal , nuclear magnetic resonance , environmental chemistry , physics , oceanography , organic chemistry , nuclear physics , geology
Behaviors of Pd structures with different thicknesses supported by Ta 2 O 5 /Ta in the reaction with oxygen and CO were studied by XPS and SEM. For the samples with a Pd thickness of 3 nm, a new low‐binding‐energy component appeared in the Pd 3d level upon O 2 exposure at ∼200 °C and was reduced in intensity after a subsequent CO exposure at 150 and 200 °C. The change in the Ta 4f state could also be found upon oxygen and CO exposure, indicating that both Pd and the Ta‐oxide substrate participate in the chemical reactions. For the sample with a higher Pd thickness, a positive shift in the Pd 3d level due to the oxidation of Pd was observed after exposure to O 2 at a higher temperature (280 °C). A subsequent CO exposure at ∼150 °C could not reduce Pd‐oxide layers, as confirmed by the unchanged Pd 3d spectra after CO treatment, i.e. Pd‐oxide was not reactive for CO oxidation. Copyright © 2010 John Wiley & Sons, Ltd.