Organic pollutants can be effectively degraded by CeO2/H2O2 system, the catalytic activity of which is restricted by over-complexation of H2O2 with CeO2. In this study, nano ceria was pretreated simply in different ways. Degradation of AO7 was employed to evaluate the catalytic activity of the pretreated ceria samples in the presence of H2O2 in pre-adsorbed mode (AO7 pre-adsorbed on CeO2 before the addition of H2O2) and pre-mixed mode (CeO2 pre-mixed with H2O2 before the addition of AO7). Two sulfated ceria samples (H2SO4-CeO2 and Na2SO4-CeO2) exhibit enhanced catalytic performance in both modes compared with un-pretreated bare CeO2. XRD, BET, FTIR and potentiometric titration methods were used to characterize the pretreated ceria samples. The sulfated samples display stronger surface acidity due to the sulfate ions anchored on their surface. Raman and XPS measurements were carried out to analyze the samples after reacting with H2O2. A mechanism to explain the improved catalytic activity of sulfated CeO2 is proposed that the active surface peroxide species (equivalent to Ce(III)-O2H-), which are excessive due to the over-complexation of H2O2 with surface Ce3+ sites, can be decomposed into high-active hydroxyl radicals under surface acidic environment. (C) 2013 Elsevier B.V. All rights reserved.