In situ observation of platinum sintering on ceria-based oxide for autoexhaust catalysts using Turbo-XAS

Abstract

Using a time resolved X-ray absorption spectroscopy (XAS) technique, we studied an in situ dynamic observation of sintering for Pt particles supported on a ceria-based oxide and Al2O3 supports under cyclic oxidizing/reducing conditions at 800 °C. The effect of the support oxide and the amount of Pt loading on the Pt sintering was investigated. The sintering of Pt particles in 2 wt% Pt/ceria-based oxide could be inhibited, when compared to in 2 wt% Pt/Al2O3. Moreover, 0.5 wt% Pt and 1 wt% Pt/ceria-based oxide with a lower Pt loading brought higher stability of Pt against sintering. For a 0.5 wt% Pt/ceria-based oxide catalyst, sintering was completely inhibited and highly dispersed Pt particles (particle size; 1.5 nm) were maintained under redox cycling at 800 °C. These results lead to the conclusion that Pt-O-Ce bond formation on the surface of a ceria-based oxide under oxidative conditions in redox cycling inhibits the sintering of Pt particles, and that the Pt-O-Ce anchor site (its strength and number) has an important role in the sintering inhibition of Pt particles on ceria-based oxide. In addition, we note and discuss apparent change in the oxygen storage/release performance of ceria-based oxide from the viewpoint of the Pt particle size and the intrinsic bulk behavior of ceria-based oxide. © 2011 Elsevier B.V. All rights reserved.