NOx Storage on BaTi_0.8Cu_0.2O₃ Perovskite Catalysts: Addressing a Feasible Mechanism

The NOx storage mechanism on BaTi_0.8Cu_0.2O₃ catalyst were studied using different techniques. The results obtained by XRD, ATR, TGA and XPS under NOx storage-regeneration conditions revealed that BaO generated on the catalyst by decomposition of Ba₂TiO₄ plays a key role in the NOx storage process. In situ DRIFTS experiments under NO/O₂ and NO/N₂ show that nitrites and nitrates are formed on the perovskite during the NOx storage process. Thus, it seems that, as for model NSR catalysts, the NOx storage on BaTi_0.8Cu_0.2O₃ catalyst takes place by both "nitrite" and "nitrate" routes, with the main pathway being highly dependent on the temperature and the time on stream: (i) at T < 350 °C, NO adsorption leads to nitrites formation on the catalyst and (ii) at T > 350 °C, the catalyst activity for NO oxidation promotes NO₂ generation and the nitrate formation.