Fabrication of three dimensional CeO2 hierarchical structures: Precursor template synthesis, formation mechanism and properties

Abstract

In this paper, three dimensional mesoporous CeO₂ hierarchical structures were synthesized through the thermal decomposition of cerium formate precursors, which were prepared by a solvothermal method. X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier-transform infrared (FT-IR), and Thermal gravimetric (TG) was applied to characterize the precursors. Urchin-like Ce(HCOO)₃ precursors were prepared using dimethyl sulfoxide (DMSO) and ammonia solution (1 M) as solvent and base source, respectively, while coral-like Ce(HCOO)₃ precursors were prepared using dimethyl formamide (DMF) and NH₄HCO₃ as solvent and base source, respectively. The formation mechanism of the hierarchical structured precursors was proposed involving a process of anisotropic growth–H₂O induced self-assembly–oriented aggregation and disassembly–Ostwald ripening. CeO₂ hierarchical structures were obtained by annealing the corresponding Ce(HCOO)₃ precursors at 400 °C for 60 min. N₂ adsorption–desorption isotherms indicate that both CeO₂ hierarchical structures derived from their Ce(HCOO)₃ precursors display large surface areas and high pore volumes. In addition, the as-prepared CeO₂ catalysts with hierarchical structures are highly active for conversion of CO to CO₂.