Pd-Cu supported on TiO2-CeO2 mixed oxides (Pd-Cu/TiO2-CeO2) were tested for the reduction of nitrate ions in water. Compared with a Pd-Cu catalyst with TiO2 only as support (Pd-Cu/TiO2), which was proved to be active for this reaction in our previous study, Pd-Cu/TiO2-CeO2 showed improved activity if TiO2-CeO2 contained an appropriate amount of ceria (Ti:Ce = 18:1). Especially, the Pd-Cu/TiO2-CeO2 (Ti:Ce = 18:1) showed the initial nitrate reduction rate of 3.20 mmolimin/g(cat), eight times higher than that of Pd-Cu/TiO2 (0.41 mmol/min/g(cat)). It was supposed that the improved activity of the catalyst was attributable to the reduced surface (oxygen vacancies) of the support and zero-valence states of the active metals (including the Pd-Cu alloy) in the catalyst. (C) 2014 Elsevier B.V. All rights reserved.