Three supported Pt/Fe 2 O 3 catalysts were prepared by depositing platinum colloids with discrete particle sizes onto the surface of Fe(OH) 3 powders, which were then calcined at an elevated temperature. Pt nanoparticle colloids with mean diameters of 1.1, 1.9 or 2.7 nm were synthesized in order to investigate the effects of particle size on the structure and CO oxidation properties of these Pt/Fe 2 O 3 catalysts. All Pt/Fe 2 O 3 catalysts demonstrated activity in low-temperature CO oxidation, with the sample containing Pt nanoparticles with a mean diameter of 1.9 nm (designated Pt-Fe 2 O 3 -b) exhibiting relatively higher catalytic activity. Compared with the other two catalysts, Pt/Fe 2 O 3 -b exhibited an increased ability to activate oxygen and maintain the stability of Pt species, correlating with its higher catalytic activity. The results of various characterization techniques revealed that the mean particle size of the Pt nanoparticles could influence the chemical states of Pt species and the strength of metal-support interactions of the Pt/Fe 2 O 3 catalysts. It was observed that the metal-support interactions in Pt/Fe 2 O 3 catalysts were able to adjust the redox properties and the O 2 -activation abilities of the catalysts. Finally, it is proposed that the interacting Pt and Fe species located at the Pt-FeO x interface are the primary active sites for the activation of CO and O 2 , respectively.

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