Characterization of cerium dioxide nanoparticles prepared by supercritical water oxidation

Abstract

CeO2 nanoparticles with high purity and crystallinity were prepared by a continuous supercritical water oxidation (SCWO) reaction. The phase composition, microstructure, and morphology of the prepared CeO2 particles were characterized by X-Ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), BET specific surface area (BET), and X-ray photoelectron spectroscopy (XPS). The size distribution of the particles is narrow with an average particle size between 10 and 13nm; the diameter decreased gradually as the Ce(NO3)3·6H2O concentration in the preparation increased. The BET results show an increase in the products׳ specific surface area as the Ce(NO3)3·6H2O concentration increased, with an average surface area of 48m2g−1. SEM micrographs reveal that the CeO2 particles are spherical, and that higher Ce(NO3)3·6H2O concentrations are conducive to the formation of smaller particles. However, excess Ce(NO3)3·6H2O caused serious agglomeration, due to the higher surface energy. XPS patterns indicate that Ce(III) was almost completely oxidized to Ce(IV) in the reaction, and that the binding capacity of Ce–O reduced gradually with increasing concentrations of Ce(NO3)3.