We prepared PdO nanoflakes by reactive sputter deposition to form a heterostructure with TiO2 nanoparticles on the SiO2 substrate for the study of photocatalytic decomposition of methylene blue (MB) molecules. Although the PdO nanoflake has little photocatalytic activity toward MB decomposition, the PdO/TiO2 heterostructure has a photocatalytic activity toward MB decomposition under UV light illumination as large as twice that of bare TiO2 nanoparticles. The enhancement in the photocatalytic activity is ascribed to the fast photogenerated carrier separation resulting from the potential barrier formed at the heterojunction between the two oxide semiconductors. Although PdO nanoflakes can be photoexcited under visible light illumination, the PdO/TiO2 heterostructure exhibits little photocatalytic activity toward the MB decomposition. (C) 2012 Elsevier B. V. All rights reserved.