Gold nanoparticles supported on reducible oxides such as TiO2 demonstrate exceptional catalytic activity for a wide range of oxidation reactions including CO oxidation, olefin epoxidation and water gas shift catalysis. In-situ transmission IR spectroscopic and kinetic studies along with first-principle density functional theory results suggest that the Au-Ti4+ dual perimeter sites are directly involved in the activation of oxygen and help to promote selective oxidation reactions. Interfacial Au-Ti4+ sites aid in the activation of O2 as a result of charge transfer from the Au into antibonding states on O2 and direct di-s interactions with interfacial Au-Ti4+ sites. Oxygen dissociates with barriers of 0.16-0.60 eV thus allowing these materials to operate over a wide range of temperatures and offering the ability also to control H-H, C-H, and C-O bond scission. At low temperatures, adsorbed O2 can directly react with co-adsorbed CO as well as other intermediates. At higher temperatures, O2 dissociates to form active oxygen adatoms (O*) on Au and TiO2 that readily react with bound hydrocarbon intermediates. Atomic oxygen as well as hydroxyl groups bound to Au are rather basic and assist in activating weakly acidic C-H bonds thus promoting the activation of neighboring RC-O bonds. The interfacial Au-Ti4+ sites can subsequently carryout the activation of the RC-O bond to subsequently form unsaturated and partially oxidized products. Herein we discuss the oxidation of CO, the partial oxidation of ethylene to ethylene oxide and the partial oxidation of C2-C4 acids at the Au/TiO2 interface.

Selective oxidation at the Au/TiO2 interface

251st National Meeting (2016)

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