Function of various levels of hierarchical organization of the porous Ce0.9REE0.1O1.95 mixed oxides in the catalytic activity.

In this paper, the effect of the nanocrystallites hierarchical arrangement on CO oxidation and soot combustion activity has been investigated. Hierarchically structured star-shaped particles (HS stars) were compared with microemulsion-derived, loosely arranged nanoparticles (NPs). The star-like Ce0.9REE0.1O1.95 mixed oxides were synthesized by the oxidative thermolysis of the Ce0.9REE0.1(HCOO)3 mixed formates. The study of the synthesis, structure and catalytic activity of the porous, star-like ceria based mixed oxides was presented for the first time. It was shown that each level of the hierarchical structure of the star-like mixed oxides has its own functionality and it is vulnerable for modifications. In-depth characterization of as synthesized ceria allowed to determine relationship between hierarchically-structured nature of material with its catalytic activity in CO oxidation and soot combustion. It was concluded that the presence of the 3D structure composed of ceria nanocrystals significantly improves the stability and catalytic activity of star-like material in comparison to nano-powdered one. Moreover, introduction of the trivalent RE-ion into the ceria structure lead to further improvement the CO oxidation performance. Finally, key-lock catalysis concept was applied to explain the enhanced activity of the hierarchically structured star-shaped ceria particles as a catalyst in the soot combustion process in comparison to nanocrystalline CeO2.