Unveiling the Surface Chemical Reactions during Multi-Phase Catalytic Oxidation of Soot on Nanoengineering/Interfacing/Doping-Prepared Mn-CeO Catalysts Using TG-MS and Operando DRIFTS-MS.

The aerosol pyrolysis method from nitrate precursors was used to prepare the Mn-CeO catalyst containing MnO, CeO, and Mn-doped CeO nanoparticles for catalyzing carbonous soot oxidation. The prepared Mn-CeO catalysts have high specific surface areas, Ce ratio, and oxygen vacancy defects; these are a benefit for soot oxidation. The for soot oxidation on the 0.57Mn-CeO catalyst is as low as 355 °C, which is 329 °C lower than that for soot oxidation without a catalyst. The catalysts were characterized using XRD, SEM-EDS, HRTEM, XPS, Raman spectroscopy, H-TPR-MS, O-TPD-MS, soot-TPR-MS, and operando DRIFTS-MS. The functions of MnO, CeO, and Mn-doped CeO in the 0.57Mn-CeO catalyst are unveiled. Mn-doped CeO plays a key role and CeO participates in soot oxidation, while MnO is used to enhance higher ratios of Ce, via the reaction of Mn + Ce = Mn + Ce. The mechanism of soot oxidation on Mn-CeO was proposed.