Planar-dependent oxygen vacancy concentrations in photocatalytic CeO₂ nanoparticles

The present work reports the rapid preparation of CeO₂ nanorods by surfactant-free precipitation for the first time, which initiates a strategy for the quantitative elucidation of the importance of the exposed crystallographic planes and the oxygen vacancy concentrations of different morphologies of nanoceria. These relations are revealed through comparison of the relative surface areas of the exposed crystallographic planes. The precipitation temperature was critical in that nanooctahedra formed at the three lower temperatures and nanorods formed at the highest. The key feature to differentiate the photocatalytic performance was the morphology that the nanorods exhibit ∼200% superior performance compared to those of the nanooctahedra. The principal reason for this is the presence of exposed {110} planes in the nanorods, which are not present in nanoctahedra. This crystallographic dependence of the improved performance of the nanorods is attributed directly to the greater oxygen vacancy concentration for the calculated surface area of this morphology.