| Summary: | The NOx storage mechanism on BaTi<sub>0.8</sub>Cu<sub>0.2</sub>O<sub>3</sub> 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 Ba<sub>2</sub>TiO<sub>4</sub> plays a key role in the NOx storage process. In situ DRIFTS experiments under NO/O<sub>2</sub> and NO/N<sub>2</sub> 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<sub>0.8</sub>Cu<sub>0.2</sub>O<sub>3</sub> 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 NO<sub>2</sub> generation and the nitrate formation.
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