Catalytic oxidation of NO over TiO2 supported platinum clusters. II: Mechanism study by in situ FTIR spectra

The surface species formed during NO oxidation in the absence/presence of SO2 over Pt/TiO2 catalyst prepared by photo-deposition are investigated by in situ FTIR spectroscopy. During the adsorption of NO–O2, predominant various nitrates are formed on the surface of TiO2. The addition of SO2 to NO–O2 greatly suppresses the formation of surface nitrates and also changes the types of nitrates formed. The decomposition of surface nitrates on Pt/TiO2 is observed at elevated temperature of ca. 250 °C and the decomposition temperature is retarded to ca. 350 °C with the addition of SO2 during NO–O2 adsorption. The direct oxidation of gaseous NO to NO2 is proposed as the main pathway for NO2 formation and the decomposition of surface nitrates at elevated temperatures plays a negative role on NO oxidation.