A series of Ag/CeO2 catalysts was synthesized by the incipient wetness method. Compared with Ag/Al2O3 and CeO2 catalysts, Ag/CeO2 catalysts are more promising candidates for naphthalene oxidation, in which Cex+ act as the main active sites and are efficiently promoted by Ag species. By characterizing the solid properties and the redox ability, the mechanism of ceria catalysis by the Ag-modified catalysts was investigated. It was found that Ag species can work as an oxygen pump to enhance the oxygen availability in the ceria bulk. They also promote the oxygen regeneration capacity by the oxygen spillover effect. However, such an effect would also decrease the ability for active oxygen regeneration at higher Ag loading, which arises from the lower surface oxygen vacancy concentration. Because of the balance between these two factors, the Ag/CeO2 catalyst with 1 wt.%Ag shows the best performance for isothermal catalytic oxidation of naphthalene. (C) 2017 Elsevier B.V. All rights reserved.