Morphology-Controllable Synthesis of Mesoporous CeO₂ Nano- and Microstructures

Abstract

Spherical cerium oxide nanoparticles and microsized rod-shaped and spindle-like CeO 2 structures have been synthesized using a polyol method. When the duration of reaction and the concentration of cerium precursor are controlled, CeO 2 products of different morphologies can be selectively produced. Results from XRD, XPS, SEM, and FT-IR measurements suggest that the CeO 2 nanospheres are formed from the decomposition of the cerium precursor. Further reactions between the as-prepared CeO 2 and ethylene glycol yield the rods/spindle-like cerium formate particles. These morphologies are preserved even after calcination. The order of band gap energy of these samples was found to be rod-shaped > spherical > spindle-like samples, as determined by the UV−Vis spectroscopic method. Compared to a nonoriented polycrystalline CeO 2, these samples show an increase in band gap energy due to the quantum size effect. The higher catalytic activity on CO conversion in a spindle-like sample can be explained from the extent of Ce(IV) reduction and the oxygen vacancy.