Unveiling the Surface Chemical Reactions during Multi-Phase Catalytic Oxidation of Soot on Nanoengineering/Interfacing/Doping-Prepared Mn-CeO₂ Catalysts Using TG-MS and Operando DRIFTS-MS

Abstract

The aerosol pyrolysis method from nitrate precursors was used to prepare the Mn-CeO 2 catalyst containing Mn 2 O 3 , CeO 2 , and Mn-doped CeO 2 nanoparticles for catalyzing carbonous soot oxidation. The prepared Mn-CeO 2 catalysts have high specific surface areas, Ce 3+ ratio, and oxygen vacancy defects; these are a benefit for soot oxidation. The T 50 for soot oxidation on the 0.57Mn-CeO 2 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 2 -TPR-MS, O 2 -TPD-MS, soot-TPR-MS, and operando DRIFTS-MS. The functions of Mn 2 O 3 , CeO 2 , and Mn-doped CeO 2 in the 0.57Mn-CeO 2 catalyst are unveiled. Mn-doped CeO 2 plays a key role and CeO 2 participates in soot oxidation, while Mn 2 O 3 is used to enhance higher ratios of Ce 3+ , via the reaction of Mn 3+ + Ce 4+ = Mn 4+ + Ce 3+ . The mechanism of soot oxidation on Mn-CeO 2 was proposed.