Abstract
Balance of activity and thermal stability for diesel oxidation catalyst (DOC) is difficult to control in terms of different modification methods. We prepare SrMnO3-mixed SmMn2O5 (SMO) by the one-pot calcination, then followed in 5 M HNO3 treatment to yield Mn4+@SMO catalyst. Highly active Mn4+ cations form on SMO surface as amorphous MnO2 via removing nearly all the Sr in perovskite framework and surface Sm of SMO. Mn4+@SMO exhibits superior DOC performance compared with pristine and MnO2-doped SMO under a GHSV of 120000 mL·g−1·h−1 or even after 800 °C hydrothermal aging, since it possesses higher average oxidation state of Mn, more oxygen vacancies, stronger covalent bonds of Mn-O, and larger NO adsorption above 200 °C. DRIFTS, NAP-XPS, and isotopic analysis demonstrate that the exposed Mn4+ cations are the major sites for nitrate or nitrite adsorptions, while both CO and NO oxidation reactions follow the MvK mechanism.
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