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Size-Dependent Oxygen Activation Efficiency over Pdn/TiO2(110) for the CO Oxidation Reaction

Summary: Size-Dependent Oxygen Activation Efficiency over Pdn/TiO2(110) for the CO
Oxidation Reaction
William E. Kaden, William A. Kunkel, Matt D. Kane, F. Sloan Roberts, and Scott L. Anderson*
Department of Chemistry, UniVersity of Utah, 315 South 1400 East, Room 2020, Salt Lake City, Utah 84112-0850
Received April 20, 2010; E-mail: anderson@chem.utah.edu
Abstract: The dissociative binding efficiency of oxygen over Pdn/
TiO2(110) (n ) 4, 7, 10, 20) has been measured using temper-
ature programmed reaction (TPR) mass spectrometry and X-ray
photoemission spectroscopy (XPS) following exposure to O2 with
varying doses and dose temperatures. Experiments were carried
out following two different O2 exposures at 400 K (10 L and 50 L)
and for 10 L of O2 exposure at varying temperatures (Tsurf ) 200,
300, and 400 K). During TPR taken after sequential O2 and CO
(5 L at 180 K) exposures, unreacted CO is found to desorb in
three features at Tdesorb 150, 200, and 430 K, while CO2 is
observed to desorb between 170 and 450 K. We show that Pd20
has exceptionally high efficiency for oxygen activation, compared
to other cluster sizes. As a consequence, its activity becomes
limited by competitive CO binding at low O2 exposures, while other
Pdn sizes are still limited by inefficient O2 activation. This


Source: Anderson, Scott L. - Department of Chemistry, University of Utah


Collections: Energy Storage, Conversion and Utilization; Materials Science; Chemistry