Effect of Ag doping on Pd/Ag-CeO catalysts for CO and CH oxidation.

To achieve high fuel efficiency and low emission in automobiles, it is necessary to develop highly active diesel oxidation catalysts (DOCs). Pd/CeO catalysts have been widely used as active catalysts for CO and CH oxidation reactions. Additionally, Ag has been reported to enhance the oxygen storage capacity (OSC) of CeO, which contributes to the oxidation ability of Pd/CeO. In this study, Pd/Ag-CeO catalysts were used for CO and CH oxidation reactions. When CeO was doped with appropriate amounts of Ag, reducibility and CO desorption rate were increased, which confirmed the high OSCs of Ag-doped catalysts. However, Ag particles were formed and the Ce/Ce ratio decreased when CeO was doped with excess amounts of Ag. In addition, reduced Pd (Pd), which is an active species for CH oxidation, was formed and maintained even under oxidative reaction conditions. Since the removal of CH is important for the oxidation of CO and CH, the catalyst with the highest Pd fraction (Pd/0.1Ag-CeO and Pd/0.3Ag-CeO) presented improved catalytic activity. Consequently, the optimal amount of Ag enhanced the OSC of Pd/Ag-CeO catalysts and formed active Pd species under oxidative conditions, which resulted in the excellent catalytic activity of Pd/Ag-CeO for the CO and CH oxidation reaction.