The surface species formed during NO oxidation in the absence/presence of SO(2) over Pt/TiO(2) catalyst prepared by photo-deposition are investigated by in situ FTIR spectroscopy. During the adsorption of NO-O(2), predominant various nitrates are formed on the surface of TiO(2). The addition of SO(2) to NO-O(2) greatly suppresses the formation of surface nitrates and also changes the types of nitrates formed. The decomposition of surface nitrates on Pt/TiO(2) is observed at elevated temperature of ca. 250 degrees C and the decomposition temperature is retarded to ca. 350 degrees C with the addition of SO(2) during NO-O(2) adsorption. The direct oxidation of gaseous NO to NO(2) is proposed as the main pathway for NO(2) formation and the decomposition of surface nitrates at elevated temperatures plays a negative role on NO oxidation. (C) 2010 Elsevier B. V. All rights reserved.