Activity studies of nickel-gold and cobalt-gold bimetallic clusters on titanium dioxide(110)

A series of model experiments were undertaken to examine and gain fundamental understanding of growth and activity of Au-based bimetallic clusters. This knowledge can aid in the development and tailoring of new materials for specific catalytic processes. Activity of methanol and carbon monoxide oxidation on Co-Au and Ni-Au bimetallic clusters on a TiO2 (titania) support was examined under ultra-high vacuum (UHV) conditions, to determine the mechanism of oxidation. On a pure gold surface, the O-H bond is broken, and the methoxy intermediate binds to the Au-titania interface. A C-H bond is broken and the resulting product is formaldehyde. The additions of nickel and cobalt to the gold surface were to determine any synergistic effects, though they only resulted in additive effects. Additional experiments were undertaken to understand how gold and Ni-Au clusters encapsulate with titania upon heating, ideally to increase the number of Au-titania interfacial sites. The encapsulated Ni-Au clusters were also oxidized in various steps. Oxidation of the Ni-Au clusters after encapsulation yielded the greatest increase in formaldehyde production. Carbon monoxide oxidation of Ni-Au and Co-Au was also examined as a comparison because it is well studied throughout the literature.