This paper focuses on the study of Ni metal nanoparticles supported on Ti-doped ceria surfaces as steam reforming of ethanol catalysts for hydrogen production and presents a fundamental mechanistic understanding of the effect of Ti dopant in ceria on their structure and electronic properties.  The unique oxygen-storage capacity and redox properties of ceria can potentially inhibit Ni particles from sintering and eliminate carbon deposits/coke species from Ni surfaces during the reforming process. Doping ceria with Ti can enhance the stability and redox properties of ceria for practical applications. Furthermore, the unique heterogeneous structures at the doped-ceria interfaces can alter the properties of Ni. In the study, reducible CeOx(111) (1.5<x<2) thin films grown on a Ru(0001) substrate were used as model ceria supports.  Ti-doped ceria thin films were prepared by physical vapor deposition of Ti on CeOx at 300 K. X-ray photoelectron spectroscopy data suggest that Ti is oxidized to Ti4+ at the cost of Ce4+ reduction on both fully oxidized and partially reduced ceria. Our scanning tunneling microscopy results show that doping ceria with Ti introduces the formation of atomic-like titania features at 300 K, which order into chain structures upon heating. These titania features provide additional nucleation sites for Ni particles that grow as two-dimensional structures at 300 K. With heating, Ni particles tend to anchor to titania chains on the reduced ceria and the sintering of Ni is significantly inhibited. However, interesting nickel-titania mixed structures are formed on Ti-doped CeO2 surfaces. The different growth behavior of Ni on Ti-modified CeO2 is attributed to the formation of Ni2+. In addition to structure and stability, the promotional effects of Ti-doped ceria on the chemical behavior of Ni particles will be examined upon adsorption of ethanol molecules. The research is sponsored by the National Science Foundation Career Grant (Award Number: CHE1151846).

Growth and characterization of nickel nanoparticles supported on Ti-doped ceria thin films

247th National Meeting (2014)

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