Complete oxidization of formaldehyde into harmless water and carbon dioxide was obtained over Ag/MnOx-CeO2 catalysts at a temperature as low as 373 K. Structural analysis by X-ray powder diffraction (XRD), X-ray photoelectron spectra (XPS) and temperature-programmed reduction (TPR) measurements revealed that the formation of MnOx-CeO2 solid solution and the subsequent addition of silver species resulted in significant improvement in the effective activation of oxygen molecules in the reaction stream. Accordingly, a consecutive oxygen transfer mechanism starting from the oxygen reservoir Of CeO2 to active Ag2O sites through MnOx was proposed. The oxygen species released from the decomposition of Ag2O participated in the oxidation of formaldehyde, and the reoxidation of Ag to Ag2O was achieved through the oxygen species from MnO2. Simultaneously, the transformation of the produced Mn2O3 to MnO2 was realized by the oxygen species from the oxygen reservoir of CeO2, and the Ce2O3 thus formed can be reoxidized into CeO2 by the oxygen in the feed stream. Such a consecutive oxygen pathway was suggested to play an important role in the complete oxidation of formaldehyde. (c) 2006 Elsevier B.V. All rights reserved.