Phase-Dependent Structure Sensitivity of Pt/TiO2 for CO Oxidation Reactions

Abstract

Here, we report the different structure sensitivity of Pt nanoparticles supported on titania (rutile vs anatase) for CO oxidation. The steady-state specific activity of Pt/rutile gradually increases with increasing Pt dispersion, while that of Pt/anatase remains unchanged regardless of Pt dispersion and is lower than that of Pt/rutile. Our kinetic studies demonstrate that the reaction order for CO is positive for subnm Pt clusters stabilized on rutile and gradually changes to zero for large Pt clusters (>1 nm). While Pt/anatase catalysts do not show dependency for CO concentration, irrespective of the size of the Pt nanoparticles. Scanning transmission electron microscopy (STEM), X-ray photoelectron spectroscopy (XPS), and CO chemisorption results confirm that the sintering of subnm Pt clusters supported on anatase occurs during the CO oxidation reaction, which is correlated with the change in the CO reaction order from positive (initially) to zero during the reaction. In contrast, subnm Pt clusters supported on rutile do not show significant sintering during the reaction but exhibit positive reaction order even at the steady state. Our study reveals the origin of the dramatic catalytic differences between Pt nanoparticles supported on anatase and rutile, highlighting the superior stability and activity of the Pt/rutile catalysts.