Fabrication of porous and highly defective CeO2-based catalysts for soot combustion with the strategy of soft-template addition and matrix doping by multiple rare earth elements

Abstract

In this study, aiming to optimize the reactivity of CeO2 for soot combustion, rare earth elements (La, Pr, Sm and Y) co-doped CeO2 catalysts were synthesized via polyvinylpyrrolidone (PVP) and glycine (GNC) combustion methods. The PVP-CeO2-Re catalyst maintains a high specific surface area (82.9 m2 g-1) and abundant porous structure, thus being able to enhance the soot contact efficiency. The co-doping of multiple rare earth ions improves also the redox properties of the catalyst and increases the surface defects/vacancies, which is crucial to form the active surface O2- and O22- species to participate in soot combustion. The oxygen exchange rate over the catalyst with gaseous O2 can be accelerated by raising the temperature, and the exchange mechanism changes from a mixture of the R1 and R2 mechanisms to a domination by the R2 mechanism. Notably, PVP-CeO2-Re catalyst shows not only excellent activity (T50=373 °C) but also good stability. Our work could provide some reference for the design of promising catalysts applied in diesel particulate filters.