Topotactical Route to Multiwalled Cerium Oxide Nanotubes from MWCNTs

The development of new strategies for synthesizing 1D cerium oxide (CeO2) hollow nanostructures has attracted much attention in recent years due to the importance of their superior properties and highly anisotropic geometry. This study reports an unpublished route of fabricating novel multiwalled CeO2-delta nanotubes (CeO2-delta NTs) in which the entire volume of functionalized multiwalled carbon nanotubes (f-MWCNTs) is converted into the CeO2-delta pseudomorph through oxidation and dehydration topotactic reactions. The stable CeO2-delta (111) planes are topotactically grown on the curved C (002) planes, preferentially exposed along the nanotube axis. In their initial condition, the novel nanotubes consist of Ce oxyhydroxide (CeO2-x(OH)(x)) with residual carbon. When heating the air up to 500 degrees C, CeO2-x(OH)(x) transforms gradually by dehydration into CeO2-delta, while the residual carbon is oxidized. Despite compositional changes, nanotubes maintain their multiwalled structural integrity up to approximate to 550 degrees C. The CeO2-delta NTs exhibit an unusually high presence of Ce3+ ions and surface O vacancies, contributing to a low direct band gap ranging from 2.67 to 2.32 eV compared to their NPs counterparts (3.2 eV).

Automated summary

The development of 1D cerium oxide (CeO2) hollow nanostructures has attracted attention for their superior properties and anisotropic geometry. This study reports a novel method to fabricate multiwalled CeO2-delta nanotubes (CeO2-delta NTs) by converting functionalized multiwalled carbon nanotubes (f-MWCNTs) through oxidation and dehydration reactions. The CeO2-delta NTs exhibit a low direct band gap and an unusually high presence of Ce3+ ions and surface O vacancies.