Template-Free Hydrothermal Synthesis, Mechanism, and Photocatalytic Properties of Core–Shell CeO2 Nanospheres

CeO2 nanospheres with the core–shell nanostructure have been successfully synthesized by a template-free hydrothermal method. The structures, morphologies and optical properties of core–shell CeO2 nanospheres were analyzed by X-ray diffraction (XRD), TG, Fourier transform infrared spectroscopy, XRD, EDS, SAED, scanning electron microscopy and transmission electron microscopy, UV–Vis diffuse reflectance spectra, Raman analyses. The degradation efficiencies of core–shell CeO2 nanospheres for methyl orange were as high as 93.49, 95.67 and 98.28% within 160 min, and the rates of photo degradation of methyl orange by core–shell CeO2 nanospheres under UV-light were 0.01693, 0.01782 and 0.02375 min−1. Methyl orange was degraded in photocatalytic oxidation processes, which mainly gave the credit to a large number of reactive species including h+, surface superoxide species ·O2−, and ·OH radicals. The core–shell structure, small crystallite size and the conversion between Ce3+ and Ce4+ of CeO2 nanospheres were of importance for its catalytic activity. These results demonstrated the possibility of improving the efficient catalysts of the earth abundant CeO2 catalysts.