Formation of CeO2 Nanotubes from Ce(OH)CO3 Nanorods through Kirkendall Diffusion

In this paper, CeO2 nanotubes based on the Kirkendall effect (for simplicity, this type of nanotubes is denoted as K-type CeO2 nanotubes) are fabricated through a solid-liquid interface reaction between Ce(OH)CO3 nanorods and NaOH solutions. Our studies indicate the formation mechanism of K-type CeO2 nanotubes; is quite different from those of CeO2 nanotubes subjected to template (T-type CeO2 nanotubes) and lamellar rolling (L-type CeO2 nanotubes) reported previously by our group. The K-type CeO2 nanotubes are prepared by congregating Kirkendall voids and subsequent calcinations. The time evolution processes are imaged by TEM, and the results show that as the reaction processes, interior spaces are formed and enlarged in Ce(OH)CO3 nanorods to form K-type CeO2 nanotubes. In contrast, the interior space in T-type CeO2 nanotubes; decreases with reaction time. XRD is applied to study the phase transformation in the formation process of K-type CeO2 nanotubes. Our study also indicates NaOH and reaction temperature are two key factors responsible for formation of K-type CeO2 nanotubes. Combined with the T- and L-type nanotubes, three types of CeO2 nanotubes with different formation mechanisms are successfully synthesized in one reaction system, which might afford some guidance for the synthesis of other inorganic nanotubes.