Template‐Free Synthesis, Controlled Conversion, and CO Oxidation Properties of CeO₂ Nanorods, Nanotubes, Nanowires, and Nanocubes

Abstract

Abstract A general large‐scale synthesis of single‐crystalline and uniform CeO 2 nanorods was first realized without templates by a precipitation method at room temperature and pressure. Such nanorods have an aspect ratio of ca. 3 nm with a diameter of ca. 8 nm and a large BET specific area of 128.2 m 2 /g. On the basis of this, the controlled conversion of the as‐prepared nanorods into nanotubes, nanowires, and nanocubes through hydrothermal reactions has been realized. Further experimental results show that the growth of nanorods is a function of the base concentration, temperature, and time. In addition, particle size measurements demonstrate that the primary nanorods grow by Ostwald ripening. It is found that CeO 2 growth is faster at higher base concentration and temperature due to the accelerated ripening. During the synthesis, the formation of Ce(OH) 3 intermediate species and their transformation into CeO 2 have been dynamically demonstrated and are regarded as the key factors responsible for the evolution of shape. The CO oxidation properties of CeO 2 nanorods, nanowires, nanotubes, and nanocubes were investigated, and CeO 2 nanotubes have the best performance due to the large BET surface area and the novel inner surface. In addition, CeO 2 nanorods aged for 9 d also have an excellent catalytic performance for CO oxidation due to the exposed crystal surface (110) of CeO 2 . (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)