Interface Reaction Route to Two Different Kinds of CeO2 Nanotubes

Abstract

CeO₂ nanotubes have been synthesized with a simple solid−liquid interface reaction route in the absence of any surfactants. Although the basic reaction principles are similar, two kinds of nanotubes with completely different morphologies and structures can be generated by slightly tuning the postprocessing conditions. The first formation involves employing Ce(OH)CO₃ nanorods as both the physical and chemical templates, and the other requires layered Ce(OH)₃ as an anisotropic intermediate species. During this process, NaOH and reaction temperature were demonstrated as the key factors responsible for the formation of Ce(OH)₃ intermediate and final CeO₂ nanotubes with well-defined structures. The structural details were provided by a combination of XRD, SEM, TEM, and HRTEM investigations. Catalytic measurement shows that both nanotubes are very active for CO oxidation, and at 250 °C, the conversion rates of CeO₂ nanotubes are 3 times higher than that of the bulk counterpart.