Decoration with ceria nanoparticles activates inert gold island/film surfaces for the CO oxidation reaction

Ceria nanoparticles (<5 nm) were deposited on a polycrystalline gold film supported on SiO2/Si substrate in an e-beam apparatus, and the catalytic activity of the inverse CeO2/Au structure for the CO oxidation reaction was evaluated at ambient pressure in a recycle reactor. The gold film contained large crystal grains (lateral size in tens and hundreds of nanometers) and was nearly inert. CeO2 nanoparticles deposited directly on the silicon substrate were also inert. However, decoration of the gold film with CeO2 nanoparticles produced an activity enhancement of three orders of magnitude. This induced activation of the gold surface atoms at the interface with ceria nanoparticles was independent of the grain size of the gold film but proportional to the amount of CeO2. No visible reconstruction of the Au surface upon ceria deposition was found by TEM. XPS analysis identified a high concentration of Ce3+ in the ceria nanoparticles, but was not useful in identifying the state of the interfacial gold atoms. In stability studies, it was found that deactivation was accompanied by a decrease in the Ce3+. concentration. The Au interfacial atom-TOF of the inverse CeO2/Au film structures and Au/CeO2 nanoparticles was similar, as was the apparent activation energy, E-app = 49 +/- 9 kJ/mol, indicating a common reaction mechanism. (C) 2011 Elsevier Inc. All rights reserved.