Nanostructured equimolar ceria-praseodymia for NOx-assisted soot oxidation: Insight into Pr dominance over Pt nanoparticles and metal support interaction

This work compares the catalytic activity of nanostructured ceria-praseodymia impregnated with Pt nano-particles stabilized by n-octylsilane (Pt/Ce50Pr50-NP), with pure ceria nanoparticles (Ce-NP), ceria-praseodymia (Ce50Pr50-NP) and Pt on ceria (Pt/Ce-NP). The idea behind these structures stems from the fact that both Pt/ceria and Ce-Pr mixed oxide are effective towards CO, NO and soot oxidations, as well as for the NOx-assisted soot oxidation. The oxide supports have been prepared via a hydrothermal synthesis. Catalytic activity tests have shown the effectiveness of Ce50Pr50-NP towards the NOx-assisted soot oxidation. The intrinsic activity of this material is even higher than the Pt/Ce-NP counterpart. This finding seems related to the adsorption of NO2 onto ceria-praseodymia. The addition of Pt on the Ce50Pr50-NP surface appears unnecessary as the effect of Pr on the catalytic activity prevails. The samples have also been thermally aged and their catalytic performances have been compared. A smaller decrease in activity has been observed for Ce50Pr50-NP, compared to Ce-NP, and it has been linked to the material's persistent adsorptive properties. The deposited Pt nanoparticles on the surface of Ce50Pr5o-NP, however, have suffered from sintering after the thermal aging, and therefore both aged Pt/Ce50Pr50-NP and Ce50Pr50-NP have comparable catalytic performances.