Effects of Mn-doped ceria oxygen-storage material on oxidation activity of diesel soot

Abstract

A Diesel Particulate Filter (DPF) is an effective device for reducing the soot emission of diesel engines. In order to realize the passive regeneration of DPF at low temperature, Ce1-xMnxO2 catalysts doped with different doses of Mn were prepared through a sol-gel method. The influence of the catalyst on soot oxidation characteristics was studied by thermogravimetric analysis (TGA). The oxygen vacancy formation energy was calculated using the first principles Perdew-Wang 1991 (PW91) method based on density functional theory (DFT) within the generalized gradient approximation (GGA). Moreover, catalytic performance was evaluated using X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, H2-temperature programming reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS). The results show that the ignition temperature and peak temperature of soot oxidation gradually decrease, and also the activation energy of Ce1-xMnxO2 for the catalytic soot oxidation decreases with the increase of Mn concentration. When the Mn concentration is 50%, the ignition temperature and peak temperature are decreased by 42 °C and 32 °C, respectively. The crystal structure of the prepared Ce1-xMnxO2 has a better stability, and Mn doping leads to the increase of lattice defects. Moreover, the oxygen vacancy formation energy of the Ce1-xMnxO2 catalyst decreases with increasing Mn concentrations. When Mn doping concentration is 50%, the oxygen vacancy formation energy represents a minimum value of 0.31 eV.