Synthesis of cerium oxide-based nanostructures in near- and supercritical fluids

Cerium-oxide based nanostructures attract increasing interest for their use in multiple applications. In particular, the substitution of Ce atoms by other elements with lower oxidation state is used to control oxygen vacancies within the oxide structures, which can greatly enhance the material properties for catalysis applications. Among the synthesis approaches, supercritical water (scH2O) has been proved to be an extremely efficient media for the fast and facile elaboration of pure CeO2 nanostructures, although substitution was little investigated with this method (precursors' reactivity, mechanisms, etc.). Here, the influence of two cerium precursors - Ce(NO3)3*6H2O and Ce(NO3)6(NH4)2 - in scH2O synthesis was first investigated over the CeO2 nanostructures synthesis process. Cerium ammonium nitrate was later used as precursor for the synthesis of Ce1−x−yAxByO2−δ (A, B = Zr, Pr and/or La; 0 ≤ x, y ≤ 0.1). Supported by ICP analysis quantification, this study proposes an overview of the influences of residence time, temperature and precursors' concentration over the proportion of the substitution element in the CeO2 NCs. This work demonstrates a fast and simple process to Ce1−x−yAxByO2−δ nanostructures synthesis using scH2O synthesis