In situ DRIFTS investigation on the NOx storage mechanisms over Pt/K/TiO2–ZrO2 catalyst

The NSR catalyst Pt/K/TiO2–ZrO2 was prepared by successive impregnation. In situ DRIFTS technique was employed to investigate the NOx storage mechanisms. The results show that no adsorbed NOx species were detected over TiO2–ZrO2, while nitrite and nitrate species could be identified simultaneously over K/TiO2–ZrO2. After Pt deposition, only nitrates species, such as free nitrate ions and monodentate or bidentate nitrates, were observed. The main NOx storage route is via the potassium sites (I) adjacent to Pt, the potassium sites (II) away from Pt trap NOx only after the saturation of potassium sites (I).