FT-IR study of NOX storage mechanism over Pt/BaO/Al2O3 catalysts.: Effect of the Pt-BaO interaction

NOx storage mechanism over a model NSR catalyst has been analysed by means of in-situ FTIR. The results indicated that a two-step mechanism involving nitrite formation, without requirement of NO evolution to NO2, followed by oxidation to nitrate species, being both steps assisted by O-2, would describe the overall process at 350 degrees C. This mechanism could be also extended to a wider temperature range. The interaction between Pt and Ba sites was crucial in this mechanism, since spillover process of oxidising agents appeared to play a key role. NO2 direct interaction with BaO surface may also occur, but this process was only dominant on Ba sites away from Pt interaction.