Surface tailoring on SrMnO3@SmMn2O5 for boosting the performance in diesel oxidation catalyst

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.