Sintering-redispersion of Pt and cleterioration-regeneration of catalytic activity on Pt/MgO as automotive exhaust catalyst were studied. No Pt sintering was observed after air aging up to 1173 K. Pt L-3-edge extended X-ray absorption fine structure results revealed the formation of an Mg2PtO4-Iike compound at the MgO surface and stabilization of oxidized Pt after air aging. Interaction between Pt and lOgO involved in the formation of this Mg2PtO4-like compound likely provides an anchoring effect thalF prevents Pt sintering. After redox aging at 1073 K, Pt particles of ca. 20 nm were observed by X-ray djIffraction and transmission electron microscopy (TEM). TEM images revealed that sintered Pt redispersed into smaller Pt particles of 2-5 rim on sequential oxidation-reduction treatment at 1073 K. Interacti.ons involved in the formation of the Mg2PtO4-like compound should be the driving force for this redispersion. The redispersion behavior led to regeneration of the catalytic activity of Pt/MgO in a simulated automotive exhaust reaction. (c) 2008 Elsevier Inc. All rights reserved.