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High specific surface area nanotube g-C3N4 was fabricated by a simple two-step condensation method.

Uniform-sized and monodiperse cerium dioxide porous hollow spheres (CeO2-PH) based on the Ostwald ripening process were fabricated by a simple solvothermal method in the absence of any templates.

In this study, CeO 2 with a broom-like porous hierarchical structure was successfully prepared by a simple template-free hydrothermal method. In the whole hydrothermal process, reaction time and temperature play important roles in morphology control. The morphology of the as-prepared samples was characterized by field emission scanning electron microscopy, transmission electron microscopy and high-resolution transmission electron microscopy. Structure information was obtained by using an X-ray diffractometer and Raman analysis. Analyses of elements and chemical valence analysis were carried on X-ray photoelectron spectroscopy. Absorption edge and band gap energy were investigated by UV-vis diffuse reflectance. In addition, the optimum experimental conditions for target products were determined. Compared with various morphology samples' BET data, relative intensity of Raman peaks, catalytic evaluation, we can draw a conclusion that CeO 2 with a broom-like porous hierarchical structure has a higher concentration of oxygen vacancies that results in enhancement of catalytic activity. An Ostwald ripening process with orientative self-assembly was proposed for formation of the broom-like porous hierarchical structure.

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In this study, yttrium-doped CeO2 with a broom-like porous hierarchical structure was successfully prepared by a simple template-free hydrothermal method with cerium nitrate hexahydrate and yttrium nitrate hexahydrate as original materials. Through systematic experiments, the different effects of doping concentrations on characteristics of the ceria were examined in detail and the optimal doping ratio was determined simultaneously. The morphology and element distribution of the as-prepared samples were characterized by field emission scanning electron microscopy and high-resolution transmission electron microscopy. Structure information with Rietveld refined data were obtained by using an X-ray diffractometer. Intrinsic oxygen vacancy and extrinsic oxygen vacancy caused by doing were analyzed from Raman spectra. Analyses of elements and chemical valence analysis were carried out by X-ray photoelectron spectroscopy, and changes in reactive oxygen species were determined by calculation. Based on structural information, element valence states, results of hydrogen temperature-programmed reduction and oxygen temperature-programmed decomposition analysis and the results of photocatalytic decomposition of acetaldehyde, we can draw the conclusion that a certain amount of Y-doped CeO2 with a broom-like porous hierarchical structure has high photocatalytic activity, attributed to more oxygen vacancies and surface active oxygen species generated after yttrium doping.

a b s t r a c tYttrium-doped hedgehog-like ceria with a high concentration of oxygen vacancies was successfully prepared by a traditional hydrothermal process. Crystal phase composition, morphology, and size of as-fabricated products were found to be greatly dependent on the mole ratio of original materials and reaction temperature. The morphology and size of the as-prepared samples were characterized by FE-SEM, HR-TEM and HADDF-STEM. Structure information was obtained by XRD and Raman analyses. Absorption band and band gap energy, which are responsible for the observed photocatalytic behavior, were investigated by UV-vis diffuse reflectance. In addition, the optimum experimental conditions for target products were determined. The as-prepared doped three dimensional (3D) hierarchical structure samples showed higher photocatalytic activity than that of one dimensional (1D) octahedral and nanorod morphology ceria as evaluated by measuring CO 2 liberation form the photocatalytic decomposition of acetaldehyde.