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. The study provides new insights for the design and synthesis of efficient oxidation catalysts for carbon soot combustion as well as for other oxidation reactions of harmful hydrocarbon compounds.