Diesel Soot Combustion over Mn O Catalysts with Different Morphologies: Elucidating the Role of Active Oxygen Species in Soot Combustion.

Catalytic diesel soot combustion was examined using a series of Mn O catalysts with different morphologies, including plate, prism, hollow spheres and powders. The plate-shaped Mn O (Mn O -plate) exhibited superior carbon soot combustion activity compared to the prism-shaped, hollow-structured and powdery Mn O under both tight and loose contact modes at soot combustion temperatures (T ) of 327 °C and 457 °C, respectively. Comprehensive characterization studies using scanning electron microscopy, scanning transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, temperature-programmed reduction and oxygen release measurements, revealed that the improved activity of Mn O -plate was mainly attributed to the high oxygen release rate of surface-adsorbed active oxygen species, which originated from oxygen vacancy sites introduced during the catalyst preparation, rather than specific surface-exposed planes.