CO catalytic oxidation over Pd/CeO 2 with different chemical states of Pd

Abstract Three Pd/CeO 2 catalysts were, respectively, prepared by reduction–deposition and impregnation method (IMP) to investigate the effect of chemical state of Pd on CO oxidation. Two kinds of surface Pd species, namely PdO and Pd δ + (2 < δ ≤ 4) in Pd x Ce 1− x O 2 , were identified in all Pd/CeO 2 samples although their relative ratios in each sample were different. Surface Pd x Ce 1− x O 2 species were found to be very active for CO oxidation, and it could act as a channel by which active oxygen species can be transferred from CeO 2 to Pd species for CO oxidation. Our results reveal that the preparation method can severely influence the chemical state of Pd which can further determine the activity for CO oxidation.