Facile hydrothermal method to synthesise hexagonal rotor-like cerium carbonate hydroxide and CeO2 nanostructures

The hexagonal rotor-like cerium carbonate hydroxide (CeCO₃OH) and CeO₂ nanostructures were successfully synthesised via a facile hydrothermal method using Ce(NO₃)₃ · 6H₂O as the cerium resource, HNO₃ additive to form an acidic solution, CO(NH₂)₂ as both precipitator and carbon source and polyvinylpyrrolidone as surfactant. Characterisation techniques using an X-ray diffractometer, scanning electron microscope, transmission electron microscope, X-ray photoelectron spectroscopy, thermogravimetric differential thermal analysis apparatus and UV-vis absorption spectrum have been used for studying the roles of Ce(NO₃)₃ · 6H₂O and HNO₃. It was found that the amount of Ce(NO₃)₃ · 6H₂O has an obvious effect on the morphology of the as-synthesised CeCO₃OH and CeO₂ nanostructures, whereas HNO₃ has a significant influence on the crystalline phase. CeO₂ has a higher UV absorption than as-synthesised CeCO₃OH, which is likely associated with the charge-transition between Ce³⁺ and Ce⁴⁺.