Study of Mesostructured CeO Synthesis via Nanocasting Using SBA-15 as a Template: Influence of the Cerium Precursor.

Mesoporous materials with high surface area, large pore volume, and adjustable pore size are promising in the fields of adsorption and heterogeneous catalysis. In this work, ordered mesoporous ceria structures were successfully prepared via nanocasting using SBA-15 as a template, with Ce(NO)·6HO or CeCl·7HO as ceria precursors. The materials were characterized before and after template removal. The CeO crystallite size in the CeO/SBA-15 composites increases with successive impregnations until it reaches the pore size of the SBA-15. Upon removal of the SBA-15 template, the synthesized materials exhibit pore diameters corresponding to the wall thickness of the SBA-15, evidencing that the inverted structure was obtained. Mesoporous ceria exhibits increasingly ordered structure up to five successive impregnations with 1.3 mmol/g. Using cerium chloride as a precursor, highly ordered structures were reached after only three impregnations. The feasibility of this synthesis in fewer steps (1, 3, and 5), employing the same amount of Ce precursor (6.7 mmol/g), was also studied. Results show a higher ordering degree and oxygen mobility capacity at higher impregnation steps. The mesostructured ceria samples exhibit significantly higher oxygen mobility than commercial bulk ceria, along with high thermal stability, which highlights the usefulness of these structures.