Catalysis Today, Vol.376, 9-18, 2021
Soot combustion over Ag catalysts supported on shape-controlled CeO2
Shape-controlled CeO2 nano-rods (CeO2-R), CeO2 nano-cubes (CeO2-C) and CeO2 nano-octahedrons (CeO2-O) were prepared as support of Ag/CeO2 for soot combustion. Ag/CeO2-C is more active than Ag/CeO2-R and Ag/ CeO2-O, even with the presence of water, whose TOF value is 7.7, 11.4 times of Ag/CeO2-R and Ag/CeO2-O, respectively. The chemical state of Ag and the ability in oxygen activation is controlled by the support morphology through the interaction between Ag and CeO2. The weak interaction makes Ag in form of metallic state on Ag/CeO2-C which has better contact extent with soot than Ag oxides. Meanwhile, a high concentration of bulk oxygen vacancies on Ag/CeO2-C is also formed which efficiently provide active oxygen species by oxygen reverse spillover. It also explores a new pathway boosting soot combustion. As for CeO2-R and CeO2-O, although the introduced Ag improves the surface reducibility on CeO2, similar oxygen desorption behavior with the introduction of Ag reveals the unchanged way in oxygen activation and reaction pathway in soot combustion.