Exploiting the dynamic properties of Pt on ceria for low-temperature CO oxidation

This study explores the dynamic properties of Pt/CeO(2)catalysts to develop active catalytic converters for diesel exhausts. It is now well established that single Pt atoms can be stabilised on ceria surface defects under oxidising conditions. However, their catalytic activity is rather poor. A reducing treatment is required to build more active Pt nanoparticles. A Pt/CeO(2)catalyst, containing mainly atomically dispersed Pt species, was exposed to reduction steps either at 250 or 500 degrees C to build Pt nanoparticles. Their redispersion after oxidising treatments in oxygen at three temperatures (room temperature, 250 degrees C and 500 degrees C) as well as in a simulated diesel exhaust gas was deeply investigated using different characterisation techniques such as high angle annular dark field scanning transmission electron microscopy,in situRaman spectroscopy,in situX-ray diffraction, X-ray photoelectron spectroscopy and H-2-temperature-programmed reduction. The arrangement of close packed Pt clusters is a permanent event at low temperatures (<200 degrees C) between two pseudo-stable states of Pt on ceria: 3D hemispherical NPs under reducing conditions and isolated cations under oxidising conditions at high temperature. We have identified an intermediate 2D monolayer arrangement that coincided with low-temperature CO oxidation (TOF approximate to 4-6 x 10(-2)s(-1)at 100 degrees C in a simulated exhaust gas containing water, NO and propene). These Pt rafts combine 100% Pt dispersion with specific electronic properties and highly reactive interfacial oxygen species.