| Abstract
| - The electrooxidation of carbon monoxide on titania- and carbon-supported gold nanoparticles of mean diameters<6.5 nm was studied in 0.5 M HClO4. The samples were prepared by physical vapor deposition, and theactivity of the supported particles compared with the reaction at bulk, polycrystalline gold. Carbon-supportedgold exhibited activity for CO oxidation only at potentials similar to that observed for bulk gold. Decreasingthe particle size below ∼2.5 nm resulted in a sharp decay in catalytic activity. Titania-supported gold exhibitedcatalytic activity at overpotentials significantly below those of bulk gold, and the activity was strongly particle-size-dependent. A maximum in activity was observed at ∼3.0 nm, and a sharp reduction in activity is observedbelow ∼2.5 nm. The results highlight two important effects. Titania is responsible for a strong substrate-induced activity for CO electrooxidation on gold particles. In addition to the induced activity at lowoverpotentials, this titania-supported gold is also shown to exhibit activity at high potentials where normallythe oxidation of the gold poisons the reaction. The second observation is that the oxidation is inhibited onparticles below 2.5 nm in size, irrespective of the support.
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