Growth and Structure of Ni–Au Bimetallic Particles on Reducible CeO2(111)

Abstract

The growth and sintering behavior of Ni-Au have been investigated on CeO x (111) (1.5 \ x \ 2) thin films with controlled oxidation states under ultrahigh vacuum conditions. Scanning tunneling microscopy studies reveal that pure Au grows three-dimensional particles with a submonolayer coverage at room temperature, while Ni prefers two-dimensional islands on ceria as a result of a stronger metal-ceria interaction. With heating, Au experiences extensive particle growth compared to Ni. In the study, bimetallic Ni-Au particles were prepared by deposition of 0.3 ML Ni followed by 0.3 ML Au on ceria. A larger fraction of deposited Au on the Ni particles dispersed on ceria. A small percent of Au was observed to form new pure Au particles on both ceria surfaces. With heating, both Au and Ni-Au particles sinter on CeO 1.8 resulting in a bimodal particle size distribution. However, mostly Ni-Au bimetallic particles are present on CeO 2 . The different sintering behavior is attributed to the surface defects present on the reduced ceria. Such behavior was also observed in the study of ceria-supported Pt-Au bimetallic particles. Our study demonstrates that bimetallic Ni-Au particles can be prepared by deposition of Au on the existing Ni particles as ''seeds'' on both oxidized and partially reduced ceria. The growth and sintering behavior of Ni-Au bimetallic surfaces are dependent on the nature of ceria supports. Our study can provide morphological and size information for the understanding of the activity of ceria-supported Ni-Au catalysts.

Metallic Alloy Nanoparticles and Metal-Semiconductor Nanomaterials

“…Supported Ni-Au alloy nanoparticles are known as robust system for catalytic activities [44]. Growth and sintering behavior of Ni-Au bimetallic alloy nanoparticles supported on CeO (1 1 1) have been studied recently to understand catalytic reactions of the nanomaterials [45].…”