Enhanced catalytic oxidation of soot over 3DOM LaMnO₃ by adding Ag and CeO₂: Improving the generation and delivery of active oxygen species

In this work, Ag-Ce modified 3DOM LaMnO₃ catalysts were first synthesized by redox etching precipitation and used for NO_x-assisted soot oxidation. Compared with wetness impregnation method, Ag introduced by redox etching precipitation method showed smaller size and stronger interaction with 3DOM LaMnO₃, thus presented better catalytic performance. Moreover, Ag content was selected as variable (Ag mass ratio = 1–5 wt%) to explore the role of Ag in catalytic soot oxidation. The characterization results had demonstrated that Ag could activate oxygen and convert it into highly active superoxide species (O₂^–). Besides, Ag could enhance the oxygen mobility and NO₂ consumption rate, leading to better activity for NO_x-assisted soot oxidation. However, excessive Ag (>4 wt%) would cause too low oxygen vacancy amount, causing worse catalytic performance. Further modification with CeO₂ mainly increased oxygen vacancy and transferred O₂^– produced on Ag. Besides, NO₂ utilization rate were further enhanced. Hence, 4Ag-Ce/LM with optimal Ag amount exhibited the best catalytic activity for NO_x-assisted soot oxidation with T₅₀ value of 367 ℃. Moreover, it also showed good reusability and water resistance. This work synthesized a promising catalyst for soot oxidation and was expected to offer a new insight for catalyst design in other fields.