Highly active MnO_x-CeO₂ catalyst for diesel soot combustion

A series of MnO_x-CeO₂ composites have been prepared via a facile coprecipitation method and used as catalysts for diesel soot combustion. It is found that the content of manganese oxide has a considerable influence on both the morphology and catalytic activity for diesel soot combustion in the copresence of NO_x and O₂. Superior catalytic activity (T_f = 360 °C) was obtained over the optimized catalyst CM₂₀ [Mn/(Mn + Ce) equals to 20 at%], which is believed to be attributable to the following two aspects: (1) the abundant pore structure, presenting between the loosely-packed homogeneous particles with similar sizes to that of the soot particles, which is beneficial for mass transfer and heat diffusion as well as the sufficient contact between catalyst and soot; (2) high concentration of Mn⁴⁺ and Ce³⁺ cations derived from the charge transfer between Mn and Ce species as active sites can adsorb and activate NO and O₂, and then greatly facilitate NO₂ production.