HAADF STEM observation of the Au/CeO2 nanostructures

•A simple method was used to fabricate Au/CeO2 nanostructures.•The method is free of surfactant and template.•The Au clusters of less than 2 nm cannot form the FCC structure of Au.•Twins are formed in the Au nanoparticles of larger than 2 nm.•The orientation relation is determined between the Au and CeO2.

Gold nanoparticles supported on oxide substrates are widely utilized as heterogeneous catalysts. Here, we apply a facile surfactant- and template-free hydrothermal method to fabricate Au/CeO2 nanostructures, and show a successful preparation of well-defined CeO2 nano-octahedrons with Au nanoparticles on their surface. The high-angle annular dark field scanning transmission microscopy imaging technique is applied to investigate microstructure of the Au/CeO2 nanostructure. We find that the Au clusters with a diameter of less than 2 nm cannot form the FCC Au lattice, and that twins emerge in the Au nanoparticles with a diameter of larger than 2 nm. Moreover, we identify preferential orientation relationships {111}Au∥{111}CeO2 and 〈110〉Au∥〈110〉CeO2〈110〉Au∥〈110〉CeO2 between the Au nanoparticles and CeO2 nano-octahedrons.