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 Al 2O 3 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/Al 2O 3. 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.