Availability, mobility and reactivity of oxygen species in Ag/CeMnOx composite oxide for promoted catalytic soot combustion

In this study, the dynamic behavior of oxygen species in Ag/CeMnO x composite oxides and their promotional effects on catalytic soot combustion were investigated. By combining in-situ XRD with multi-scale characterization techniques, the mechanism underlying the Ce-Mn synergistic effect is elucidated in the formed Ce-Mn solid solution. A series of Ag-loaded composite oxides with varying Ce:Mn molar ratios were prepared via a hydrothermal method, and it was found that the Ag/Ce8Mn2 catalyst achieved a soot half-conversion temperature (T 50 ) below 300 °C (T 50 = 295 °C), significantly outperforming Ag-loaded single-metal catalysts. Furthermore, the presence of NO and H₂O improved catalytic activity by generating oxidative intermediates and enhancing interfacial wettability. Notably, the Ag/Ce8Mn2 catalyst retained 95 % of its initial performance after five cycles, demonstrating excellent stability. XPS, H₂-TPR, O₂-TPD and Raman spectroscopy analyses revealed that an appropriate Mn doping induced abundant oxygen vacancies in the CeO₂ lattice, enhancing the active oxygen species generation and lattice oxygen activation. In-situ XRD directly observed the outward diffusion of oxygen ions from CeO₂ during the reaction, confirming the mobility of surface/bulk lattice oxygen and the oxygen replenishment mechanism facilitated by Mn-O-Ce bridge bonds, driving efficient soot oxidation. This study elucidates a synergistic regulation strategy for oxygen vacancy density and lattice oxygen mobility, providing theoretical support for the development of efficient and durable soot oxidation catalysts.