Effect of nature of ceria supports on the growth and sintering behavior of Au nanoparticles

• Flatter Au particles are formed on reduced ceria than on CeO2 at 300 K.
• Au can sinter to form larger particles with a hexagonal shape upon heating.
• Au films with discrete layers can be formed by deposition on reduced ceria at 500 K.
• Structures of Au can be controlled by Ce oxidation states and growth conditions.

The growth and sintering behavior of gold have been investigated on reducible CeOx(1 1 1 ) (1.5 < x < 2) thin films with controlled oxidation states under ultrahigh vacuum conditions. Scanning tunneling microscopy studies reveal that Au experiences the transition of the three-dimensional particle growth on the fully oxidized ceria surface to the two-dimensional growth on the reduced ceria at room temperature. X-ray photoelectron spectroscopy data show a positive shift of up to 0.7 eV for the Au 4f core level with the increase of the degree of Ce reduction in the film, which is attributed to the Au particle size effect. Upon heating to higher temperatures, Au agglomerates to form large particles with a well-defined hexagonal shape. The temperature of transformation depends on the cerium oxidation states. These Au particles exhibit the 4f binding energies that are characteristics for the bulk gold. Instead of nanoparticles, layered films can be formed on the reduced ceria surface when Au is deposited at 500 K. Our study demonstrates that the structure of Au and correspondingly the interfaces between Au and ceria can be controlled by varying the nature of ceria surfaces as well as annealing/deposition temperatures. Such study can play a role in the understanding of the structure–reactivity relationship of ceria-supported gold catalysts.

Figure optionsDownload high-quality image (300 K)Download as PowerPoint slide