Influence of H2/O2 redox treatments at different temperatures on Pd-CeO2 catalyst: Structure and oxygen storage capacity

In order to investigate the metal–support interaction in PM-CeO2 system, a Pd-doped CeO2 catalyst was prepared by the sol–gel method and was treated in the H2–O2 redox atmosphere at 300, 500 and 800 °C, respectively. The Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD) and temperature-programmed reduction (TPR) results indicate that the redox treatment at 300 °C mainly affect the surface properties of the catalyst, while those at higher temperatures have an influence on the bulk properties. 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 °C, which are encapsulated by CeO2 particles after the treatment at 800 °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 °C-treated sample presents the highest activity for CO oxidation and oxygen storage capacity. The reduction-ratio dependent activation energy (Ea) 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.