Mesoporous CeO2 nanobelts synthesized by a facile hydrothermal route via controlling cationic type and concentration of alkali

Abstract

Mesoporous CeO2 nanobelts have been synthesized by a facile hydrothermal route via controlling cationic type and concentration of alkali without any surfactant or template. The key synthesis of CeO2 nanobelts is forming the beltlike precursors in the presence of enough NaOH (Na/Ce molar ratio ⩾16.3 at 120°C) during hydrothermal process. The enough OH− ions induce the two steps of Cannizzaro disproportionation reaction to result in conversion of formate partly into carbonate, and Na+ ions with small ionic radius allow coexistence of carbonate and formate in structure and accordingly are favorable to anisotropic growth of beltlike precursors. The increased hydrothermal temperature can promote the formation of carbonates and the minimal required Na/Ce molar ratio is decreased from 16.3 at 120°C to 10.8 at 140°C. When Na+ is substituted by the same concentration of K+ or NH4+, the obtained precursor products are finally nanowires or irregular morphology. XRD measurement proves that the sodium ions do not enter the crystalline frame of CeO2 nanobelts and can be easily removed by simple washing with deionized water. After washing, CeO2 nanobelts with enlarged mesoporous pores show superior catalytic performance for CO oxidation compared with CeO2 nanoparticles prepared with traditional methods.