Surfactant-mediated morphology evolution and self-assembly of cerium oxide nanocrystals for catalytic and supercapacitor applications

Abstract

Surfactant plays a remarkable role in determining the growth process (facet exposition) of colloidal nanocrystals (NCs) and the formation of self-assembled NC superstructures, the underlying mechanism of which, however, still requires elucidation. In this work, the mechanism of surfactant-mediated morphology evolution and self-assembly of CeO₂ nanocrystals is elucidated by exploring the effect that surfactant modification has on the shape, size, exposed facets, and arrangement of the CeO₂ NCs. It is directly proved that surfactant molecules determine the morphologies of the CeO₂ NCs by preferentially bonding onto Ce-terminated {100} facets, changing from large truncated octahedra (mostly {111} and {100} exposed), to cubes (mostly {100} exposed) and small cuboctahedra (mostly {100} and {111} exposed) by increasing the amount of surfactant. The exposure degree of the {100} facets largely affects the concentration of Ce³⁺ in the CeO₂ NCs, thus the cubic CeO₂ NCs exhibit superior oxygen storage capacity and excellent supercapacitor performance due to a high fraction of exposed active {100} facets with great superstructure stability.