Copper-cerium-zirconium catalysts loaded on TiO2 prepared by a wet impregnation method were investigated for NH3-selective catalytic reduction of NOx, aiming to study the effects of the Ce/Zr molar ratio on the performance of Cu-Ce-Zr/TiO2 catalysts. The Cu-Ce-0.25-Zr-0.75/TiO2 sample exhibited nearly 100% NOx conversion over a wide temperature range (165-450 degrees C), which is strikingly superior to that of Cu/TiO2 (210-389 degrees C) within the range of exhaust temperatures of diesel engines. The factors that govern the activity enhancement were extensively investigated by using a series of characterization techniques, namely X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and temperature-programmed reduction by hydrogen (H-2-TPR). The results showed that the addition of zirconium and/or cerium refined the copper dispersion, prevented copper crystallization and partially incorporated the copper ions into the zirconia (ceira) lattice, which led to enhance the redox abilities of Cu-Ce-Zr/TiO2 catalysts. (C) 2014 Elsevier Ltd. All rights reserved.