Ceria-supported Au nanoparticles have been of great interest in catalysis. They can exhibit promising reactivity in many important applications including syngas reaction, hydrogen carbon conversion, water-gas shift reaction as well as CO oxidation. One of the major issues with Au nanoparticles is sintering at high temperatures, which results in the loss of the reactivity. The presence of Ni and Pt in bimetallic Au-Ni and Au-Pt particles could potentially inhibit the Au sintering on ceria. Furthermore, the bimetallic Au-Ni and Au-Pt particles can exhibit unique reactivity different than pure Au, Ni and Pt due to the synergistic effect between the metals. To elucidate the nature of their reactivity, it is of significance to gain a fundamental understanding of the nucleation and growth of Au-Ni and Au-Pt particles on well-ordered CeO2(111) thin films grown in situ on Ru(0001) under ultrahigh vacuum conditions. Scanning tunneling microscopy results indicate that Au shows a preferential nucleation at the step edges on CeO2 at room temperature and exhibits a larger particle size compared to that of pure Pt and Ni as a result of a weaker metal-ceria interaction and a greater mobility. Upon heating, Au significantly agglomerates to form hexagonal particles that are ~2.0 nm high. Deposition of Au on ceria with submonolayer coverage of pre-existing Pt or Ni particles can produce both monometallic and bimetallic Au particles. A bimodal size distribution is formed upon heating to higher temperatures. The bimetallic Au-Ni and Au-Pt particles exhibit significantly smaller size than that of pure Au particles. Increasing the pre-existing Ni or Pt particles can promote the formation of bimetallic Au-Ni and Au-Pt nanoparticles with a mono-dispersed particle size. During the talk, the interactions of Au-Ni/Pt as well as metal-ceria will be discussed based on our x-ray photoelectron spectroscopy results. The structures as well as electronic properties of bimetallic Au-Ni and Au-Pt particles will be further elucidated upon adsorption of CO and ethanol molecules. The research is sponsored by the Wyoming NASA EPSCoR grant and the National Science Foundation Career Grant (Award Number: CHE1151846).

Growth and structure of bimetallic Au-Ni and Au-Pt nanoparticles on reducible CeO<sub>2</sub>(111) thin films

247th National Meeting (2014)

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Growth and structure of bimetallic Au-Ni and Au-Pt nanoparticles on reducible CeO2(111) thin films

Growth and structure of bimetallic Au-Ni and Au-Pt nanoparticles on reducible CeO₂(111) thin films