Uniform Organically Modified CeO<sub>2</sub> Nanoparticles Synthesized from a Carboxylate Complex under Supercritical Hydrothermal Conditions: Impact of Ce Valence
Yuki Omura, Akira Yoko, Gimyeong Seong, Maiko Nishibori, Kakeru Ninomiya, Takaaki Tomai, Tadafumi Adschiri
Abstract
In this study, the supercritical hydrothermal synthesis of cerium oxide (CeO2) nanoparticles from a Ce–carboxylate complex with different valences was performed. Ce(III) and Ce(IV) octanoates were synthesized and hydrothermally treated at 400 °C for 10 min. The Ce valences were confirmed using Ce L3-edge X-ray absorption near-edge structure spectra. The hydrothermally treated products were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and transmission electron microscopy. When Ce(III) octanoate was used as the precursor, cerium(III) hydroxide (Ce(OH)3) nanorods were predominantly formed, whereas CeO2(IV) nanoparticles were formed as a minor product. When Ce(IV) octanoate was used, uniform CeO2 nanoparticles were synthesized directly. The CeO2 nanoparticles synthesized from Ce(IV) octanoate were smaller and more uniform than those synthesized by the previously reported supercritical hydrothermal method using cerium(IV) hydroxide Ce(OH)4.