Modification of Pd–CeO2 catalyst by different treatments: Effect on the structure and CO oxidation activity

Abstract

To investigate the interaction between noble metal and CeO2, a Pd-doped CeO2 catalyst was prepared by sol–gel method, and the catalyst was then treated in static air and a H2/O2 alternating flow at 800°C, respectively. It is found by step-scanning XRD that Pd ions migrate out of the ceria lattice during the redox treatment, while the exudation of Pd is not so obvious after the oxidative treatment. For the CO oxidation activity, the redox treated catalyst is seriously weakened compared with the oxidative-treated one. This difference is ascribed to the encapsulation of Pd crystallites by the CeO2 support during the redox treatment, which is confirmed by XPS and CO-TPR. Based on the activity and FTIR results, it is proposed that, CO oxidation at low temperatures proceeds mainly via the reaction between the adsorbed CO on Pd sites and the lattice oxygen of surface CeO2 at the Pd–Ce interface.