Mesoporous CeO2 Hollow Spheres Prepared by Ostwald Ripening and Their Environmental Applications

CeO2 hollow spheres (250-350 nm in diameter), with mesoporous shells of approximately 50 nm, were synthesized by a one-pot, template-free hydrothermal method. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), and nitrogen adsorption-desorption measurements were used to characterize the products. The formation of these hollow spheres involves the aggregation of the initial nanoparticles followed by solid evacuation driven by an Ostwald ripening process. The mesoporous CeO2 hollow spheres showed an excellent adsorption capacity for organic pollutants (Congo red) from waste water (about 84 mg Congo red per g CeO2). Furthermore, relative to commercial CeO2 powders, the CeO2 hollow spheres exhibited a higher catalytic activity towards CO oxidation.