Mechanism of Low-Temperature
CO Oxidation on Pt/Fe-Containing
Alumina Catalysts Pretreated with Water
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Abstract
In a previous article (Catal. Commun. 2012, 17, 194), we reported that Pt/Fe-containing
alumina
catalysts pretreated with water could catalyze CO oxidation even below
room temperature. To clarify the effect of the water pretreatment
and the reaction mechanism of the novel catalytic system, in situ
Fourier transform infrared (FT-IR), and X-ray absorption fine structure
(XAFS) measurements during CO oxidation were conducted. From FT-IR
measurements, it was revealed that the Pt surface of the catalyst
was covered with CO and that the adsorbed CO molecules did not desorb
easily, as in the case of conventional Pt/Al<sub>2</sub>O<sub>3</sub> catalyst. Pt L<sub>III</sub> XAFS results also suggested the presence
of CO on the Pt surface during CO oxidation. Thresholds of Fe K X-ray
absorption near-edge structure shifted with the change between oxidative
(0.5% O<sub>2</sub>/He) and reductive (1% CO/He) atmospheres, indicating
that the Fe redox change Fe<sup>2+</sup> ↔ Fe<sup>3+</sup> can
participate in the reaction. From the degree of the shifts and average
Pt diameters derived from high-angle annular dark-field scanning transmission
electron microscopy and metal dispersion measurements, it was concluded
that PtNP/FeO<sub><i>x</i></sub> boundaries were efficiently
formed upon the water pretreatment. The enhanced reactivity of the
water-pretreated catalyst can be attributed to the increased number
of boundaries and Pt diameter