It has become a hot topic to destroy air pollutants such as formaldehyde (HCHO) using noble metal nanoparticles at ambient temperature. To reduce noble metal loading for saving cost and investigate the reaction mechanism presents two challenges for this reaction. In this study, highly efficient Pd/TiO2 catalysts were facilely synthesized with deposition-precipitation method followed by sodium borohydride (NaBH4) reduction at room temperature. XPS, H-2-TPR and O-2-TPD experiments were used to identify the oxygen species on the catalysts. Complete oxidation of HCHO can be achieved at ambient temperature over them even with 0.1 wt% Pd loading. The Pd/TiO2 catalysts prepared by deposition-precipitation method is much more active than those prepared by impregnation method mainly due to the stronger capacity for the generation and transfer of chemisorbed oxygen. Water vapor is essential to HCHO oxidation. Hydroxyl radical (center dot OH) from water vapor dissociation favors the adsorption and transfer of oxygen on the Pd/TiO2 catalysts, which is very important during HCHO oxidation. (C) 2013 Elsevier B.V. All rights reserved.