In order to investigate the metal-support interaction in PM-CeO2 system, a Pd-doped CeO2 catalyst prepared by the sol-gel method and was treated in the H-2-O-2 redox atmosphere at 300,500 and 800 degrees C. respectively The Brunauer-Emmett-Teller (BET). X-ray diffraction (XRD) and temperature-programmed reduction (TPR) results indicate that the redox treatment at 300 degrees C mainly affect the surface properties of the catalyst, while those at higher temperatures have an influence on the bulk pi pet ties The step-scanning XRD and Raman results prove that Pd species on the surface of the sample mainly exist in the form of bulk Pd and pdO crystallites after the redox treatment at 500 degrees C, which are encapsulated by CeO2 particles after the treatment at 800 degrees C The CO oxidation activity. dynamic oxygen storage capacity (DOSC) and oxygen storage complete capacity (OSCC) of the catalyst vary with the treating temperature The 300 degrees C-treated sample presents the highest activity for CO oxidation and oxygen storage capacity The reduction-ratio dependent activation energy (E-a) is extremely low for the surface reduction of this sample. suggesting the participation of highly active oxygen The active oxygen are suggested to originate from the enlarged Pd-Ce interface. which depends on the avaibility of surface Pd sites and contact between metal and support (C) 2010 Elsevier B V. All rights reserved