The Strengthening Effect Of Pulse DBD On CeO₂-MO_x Catalyst Towards Model Soot Oxidation

A series of MnOx-CeO2catalysts with various Mn/(Mn+Ce) molar ratios prepared bycitric acid complex method have been studied for the catalytic combustion of model soot. Thestructure properties and surface active species on the catalysts were characterized by XRD, N2adsorption/desorption, Raman spectra, O2-TPD, H2-TPR and XPS. The soot catalyticoxidation mechanism was investigated by in situ Raman spectra. Additionally, a pulsedielectric barrier discharge (DBD) was introduced to the soot-catalyst system to inverstigatethe non-thermal plasma(NTP) enhancement for MnOx-CeO2catalysts towards soot oxidation.The results found that Mn was incorporated into ceria lattice to form solid solution, thusMnOx-CeO2catalysts exhibited superior catalytic activities than pure catalysts. Soot oxidationvia MnOx-CeO2catalysts was found to launch in the range of254.5℃to319.8℃, which wassignificantly lower than that of457.0℃in the case of catalyst absent, or349.5℃for CeO2and357.3℃for MnOx, respectively. Among the MnOx-CeO2catalysts，the catalyst withhigher solid solution concentration corresponding to larger specific surface area(SSA),smaller average crystallite size, more oxygen vacancies, and more Mn4+and Ce4+, thusexhibiting better redox property and superior soot oxidation activity. The surface activespecies including Mn4+, Olatt, Osurand Ce4+were proposed to be involved in soot oxidation. Inaddition, larger SSA and more oxygen vacancies favored to the migration and transformationof those surface active species, and were believed to play significant roles in the soot removalprocess.Soot oxidation over MnOx-CeO2catalysts via an oxidation-reduction cycle, Mn4+speciesplayed an important role in the reaction process. Firstly, Mn4+and Ce4+changed to Mn3+、Mn2+and Ce3+. Than active oxygen species (O2(active)) was generated and migrated to reactedwith soot, accompanied by the oxygen vacancies were formed on the catalyst. Part of the bulklattice oxygen Olattspilled to the surface vacancy to replenish the consumed oxygen, and Mn4+and Ce4+were partly recovered. Gas phase O2molecules(O2(gas)) acted as an oxygen storagecavern, it can adsorbed onto the oxygen vacancy to supplement the consumed active oxygenthrough O2OadsOsurOlatt. NTP can accelerate Mn4+and Ce4+changed to Mn3+、 Mn2+and Ce3+, as well as speed up Oadschanged to Osur, thus promoted the catalytic oxidationof soot.