Multi-shelled ceria hollow spheres with a tunable shell number and thickness and their superior catalytic activity.

In this work, ceria multi-shelled nanospheres with a tunable shell number and thickness were prepared by a facile coordination polymer (CP) precursor method without the use of any template and surfactant. Interestingly, the number, thickness and structure of the shell can be tuned by varying the reaction time, reaction temperature, ratio of reagent and calcination temperature. The formation process of the multi-shelled hollow spheres was also investigated, which experienced a core contraction and shell separation process. Moreover, the multi-shelled CeO2 hollow nanospheres displayed excellent photocatalytic activity in the degradation of RhB. Au and AuPd nanoparticle loaded multi-shelled CeO2 nanocomposites were also prepared. Results show that Au/CeO2 multi-shelled hollow nanospheres showed eximious catalytic activity for the reduction of p-nitrophenol with a reaction rate constant k of 0.416 min. In addition, AuPd/CeO2 exhibited a remarkable catalytic activity for the conversion of CO. Employing this method, heavy rare earth oxide multi-shelled structures and light rare earth oxide solid spheres were obtained. This method may be employed for the preparation of other materials with complex structures.