Revealing the effects of preparation methods over Ce-MnOx catalysts for soot combustion: Physicochemical properties and catalytic performance

Catalytic oxidation for soot emissions from diesel engines is a major post-processing technology, but limited by the lack of efficient catalysts. Herein, a series of MnCeO x catalysts with different Mn/Ce molar ratios were prepared by the traditional hydrothermal (tr-MnCeO x ) and MOFs derivatization method (M-MnCeO x ), and mechanism behind for soot combustion were investigated by several techniques and density functional theory (DFT) calculations. Encouragingly, N 2 adsorption–desorption result demonstrates M-MnCeO x has a larger specific surface area, thus increasing the number of active sites and contact efficiency between soot and catalysts. Further, XPS, H 2 -TPR observations manifest the appropriate Ce doping would promote the generation of oxygen vacancy through the redox cycle of Ce 4+ + Mn 3+ ↔ Mn 4+ + Ce 3+ , thereby improving the catalytic performance for soot combustion. More importantly, the DFT calculations indicate that MOFs-derived 2Mn1Ce-200 possesses the lowest oxygen vacancy formation energy and stronger affinity for both O 2 and H 2 O, which is favorable for the generation of active oxygen species. Among all catalysts, the 2Mn1Ce (Mn/Ce molar ratio of 2:1) exhibited the highest catalytic activity under tight contact with T 90 value of 360 °C, and maintained good stability. Our work provides guidance for developing catalysts with tunable physicochemical properties.