General and facile synthesis of ceria-based solid solution nanocrystals and their catalytic properties

Uniform Ce 1− x Zr x O 2 ( x=0.2–0.8) nanocrystals with ultra-small size were synthesized through a thermolysis process, facilitated by the initial formation of precursor (hydrated (Ce,Zr)-hydroxides) at low temperature. TEM, XRD, EDAX, and Raman spectra were employed to study the formation of the solid solutions with various Ce/Zr ratios. Ultraviolet–visible (UV–vis) spectra showed that the ratios of Ce 3+ to Ce 4+ in both surface and bulk for the as-prepared Ce 1− x Zr x O 2 nanocrystals increased with the zirconium content x. The well-distributed Zr and Ce in the hydrated (Ce,Zr)-hydroxides before their thermolysis became the crucial factor for the structural homogeneity of the products. In addition, this strategy was extended to the synthesis of Ce 1− x Gd x O 1− x /2, Ce 1− x Sm x O 1− x /2, and Ce 1− x Sn x O 2 solid solutions. Catalytic measurements indicated that the ceria-based catalysts were active for CO oxidation at temperatures beyond 250 °C and the sequence of catalytic activity was Ce 0.5Zr 0.5O 2>Ce 0.8Zr 0.2O 2>Ce 0.2Zr 0.8O 2>Ce 0.5Sm 0.5O 1.75. Uniform ultra-small nanostructured Ce 1− x Zr x O 2, Ce 1− x Gd x O 1− x /2, Ce 1− x Sm x O 1− x /2, and Ce 1− x Sn x O 2 solid solutions with homogeneous textures were synthesized through a thermolysis process, facilitated by the initial formation of precursors (hydrated (Ce,M)-hydroxides). [Display omitted]