Single-Step Process To Prepare CeO2 Nanotubes with Improved Catalytic Activity

CeO2 nanotubes have been grown electrochemically using a porous alumina membrane as a template. The resulting material has been characterized by means of scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy, high-angle annular dark-field scanning transmission electron microscopy tomography, high-resolution electron microscopy (HREM), and electron energy loss spectroscopy. According to SEM, the outer diameter of the nanotubes corresponds to the pore size (200 nm) of the alumina membrane, and their length ranges between 30 and 40 pm. HREM images have revealed that the width of the nanotube walls is about 6 nm. The catalytic activity of these novel materials for the CO oxidation reaction is compared to that of a polycrystalline powder CeO2 sample prepared by a conventional route. The activity of the CeO2 nanotubes is shown to be in the order of 400 times higher per gram of oxide at 200 degrees C (77.2 x 10(-2) cm(3) CO2 (STP/(g.s) for the nanotube-shaped CeO2 and 0.16 x 10(-2) cm(3) CO2 (STP/(g.s) for the powder CeO2).