Ceria-supported Co nanoparticles have been of great interest as economical and promising catalysts for chemical reactions including CO oxidation, ethanol reforming, and dry reforming of methane. To elucidate the nature of their reactivity, it is of significance to gain a fundamental understanding of the nucleation, growth, and sintering behavior of Co particles on ceria supports. We studied Co particles deposited on CeOx(111) (1.5&lt;x&lt;2) thin films as a function of Co coverages, deposition temperatures, post-deposition annealing temperatures, as well as degrees of Ce reduction using x-ray photoelectron spectroscopy and scanning tunneling microscopy. CeOx(111) thin films were grown in situ on Ru(0001) under ultrahigh vacuum conditions. Low coverages of Co (&lt; 0.5 ML) were vapor-deposited onto ceria. At 300 K, metallic Co is the only species present on partially reduced ceria. However, oxidation of Co to Co2+ occurs on CeO2. Co form two-dimensional particles with an average height of 2 Å on ceria at room temperature. Varying Co coverage from 0.05 to 0.5 ML largely increases the particle density. With further heating to 800 K, the particles can agglomerate into large three-dimensional structures. The structural and electronic properties of Co metal particles on ceria were further examined upon adsorption of reactant molecules including water, ethanol, carbon dioxide, and methane.

Structural and electronic properties of Co nanoparticles supported on reducible CeO2(111) thin films

2019 Fall National Meeting

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