Shape-Selective Synthesis and Oxygen Storage Behavior of Ceria Nanopolyhedra, Nanorods, and Nanocubes

Abstract

Single-crystalline and uniform nanopolyhedra, nanorods, and nanocubes of cubic CeO₂ were selectively prepared by a hydrothermal method at temperatures in the range of 100−180 °C under different NaOH concentrations, using Ce(NO₃)₃ as the cerium source. According to high-resolution transmission electron microscopy, they have different exposed crystal planes: {111} and {100} for polyhedra, {110} and {100} for rods, and {100} for cubes. During the synthesis, the formation of hexagonal Ce(OH)₃ intermediate species and their transformation into CeO₂ at elevated temperature, together with the base concentration, have been demonstrated as the key factors responsible for the shape evolution. Oxygen storage capacity (OSC) measurements at 400 °C revealed that the oxygen storage takes place both at the surface and in the bulk for the as-obtained CeO₂ nanorods and nanocubes, but is restricted at the surface for the nanopolyhedra just like the bulk one, because the {100}/{110}-dominated surface structures are more reactive for CO oxidation than the {111}-dominated one. This result suggests that high OSC materials might be designed and obtained by shape-selective synthetic strategy.