Activity controlling factors for low-temperature oxidation of CO over supported Pd catalysts

► The activity-controlling factors of were discussed on CO oxidation over supported Pd catalysts. ► Both of two factors, (1) formation of metallic Pd and (2) oxygen storage property of metal oxide support, were clarified to be critical. ► The oxidation of CO proceeds on Pd/CeO2 and Pd/TiO2 even under nearly 100% coverage of CO over Pd.