Nanocrystalline alumina-supported ceria–praseodymia solid solutions: structural characteristics and catalytic CO oxidation

Abstract

In this work, alumina supported ceria–praseodymia (CP/A) samples were synthesized by a deposition coprecipitation method. The structural, textural, and redox properties of the prepared samples were characterized at different calcination temperatures from 773 to 1073 K and their catalytic activity was assessed in the CO oxidation reaction. In order to determine the promoting effect of the alumina support in the sample, the physicochemical and catalytic properties of CP/A were compared with unsupported ceria–praseodymia (CP) solid solutions. The X-ray diffraction results indicated the formation of ceria–praseodymia solid solutions over the alumina support. The nanocrystalline nature of the samples was confirmed by transmission electron microscopy. The CP/A sample showed an extremely high surface area which remained reasonably high even after calcination at 1073 K. The combined analyses revealed that the CP/A sample had more oxygen vacancies than CP. The H₂-temperature programmed reduction results suggested that the active oxygens were significantly improved in CP/A over CP. The characterization results also highlighted the excellent thermal stability of CP/A. The CO oxidation profiles signified that the catalytic activity of CP/A calcined at 773 K was remarkably enhanced in comparison to that of CP. The fine dispersion of ceria–praseodymia solid solutions over the alumina support in the process of deposition coprecipitation and the synergistic effect between ceria–praseodymia and the support, which resulted in very high surface areas, oxygen vacancy concentrations, and active oxygen species, are believed to be responsible for the superior activity of the CP/A sample.