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

Abstract

In this work, Ag-Ce modified 3DOM LaMnO3 catalysts were first synthesized by redox etching precipitation and used for NOx-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 NOx-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 NOx-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.