Hierarchical macroparticles of ceria with tube-like shape - synthesis and properties

This work presents the results of a multi-technique (HRTEM - high resolution transmission electron microscopy, EDX - energy-dispersive X-ray spectroscopy, XRD - X-ray diffraction and H-2-TPR - temperature programmed reduction by H-2) study on the hierarchical organization of Yb-doped ceria nanocrystals (Ce1-xYbxO2-x/2) into tube-like macro-particles. Hierarchically organized ceria-based mixed oxides (macroparticles) were prepared by a wet chemical method. It was observed that the predetermined shape of the investigated macroparticles was kept up to x = similar to 0.2. Above this value, additional forms (like large, un-shapely aggregates of the nanoparticles) were created. A very important feature of these materials is the very high shape stability, even at high temperatures. The overall shape of the macroparticles remained unchanged even at up to 900 degrees C. Moreover, the effect of the hierarchical arrangement of nanocrystallites into the tube-like macroparticles on the activity for propane oxidation and soot combustion reactions has been investigated. The CeO2 nanopowder (prepared by the microemulsion technique) was used as an example of an unorganized structure. It was concluded that the presence of a 3D structure composed of CeO2 nanocrystals significantly improves the catalytic activity of the tube-like material in comparison to the ceria nanopowder. The investigated oxides are good candidates for catalysts of soot oxidation. For the tube-like ceria, the temperature of half oxidation (T-50% = 468 degrees C) was 62 degrees C lower than that for the nanopowder (T-50% = 538 degrees C) and 103 degrees C lower than that for non-catalysed oxidation (T-50% = 592 degrees C). Moreover, introduction of Yb3+ ions into the ceria matrix led to further improvement of the propane oxidation performance. For the tube-like Ce0.9Yb0.1O1.95, the temperature of half oxidation (T-50% = 455 degrees C) was 40 degrees C lower than that for undoped tube-like CeO2 (T-50% = 495 degrees C) and 95 degrees C lower than that for the ceria nanopowder (T-50% = 550 degrees C).

Automated summary

The study investigated the hierarchical organization of Yb-doped ceria nanocrystals into tube-like macro-particles using various techniques, revealing high shape stability and improved catalytic activity. Introduction of Yb3+ ions further enhanced the performance for propane oxidation, showcasing the potential of these materials as catalysts for soot oxidation.